Author name code: title
ADS astronomy entries on 2022-09-14
author:"Title, Alan M."
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Title: Deciphering Solar Magnetic Activity: The Solar Cycle Clock
Authors: Leamon, Robert J.; McIntosh, Scott W.; Title, Alan M.
Bibcode: 2022FrASS...9.6670L
Altcode:
The Sun's variability is controlled by the progression and interaction
of the magnetized systems that form the 22-year magnetic activity cycle
(the "Hale Cycle") as they march from their origin at ∼55° latitude
to the equator, over ∼19 years. We will discuss the end point of that
progression, dubbed "terminator" events, and our means of diagnosing
them. In this paper we expand on the Extended Solar Cycle framework to
construct a new solar activity "clock" which maps all solar magnetic
activity onto a single normalized epoch based on the terminations
of Hale Magnetic Cycles. Defining phase 0*2π on this clock as the
Terminators, then solar polar field reversals occur at ∼ 0.2*2π,
and the geomagnetically quiet intervals centered around solar minimum
start at ∼ 0.6*2π and end at the terminator, thus lasting 40% of the
cycle length. At this onset of quiescence, dubbed a "pre-terminator,"
the Sun shows a radical reduction in active region complexity and,
like the terminator events, is associated with the time when the solar
radio flux crosses F10.7 = 90 sfu. We use the terminator-based clock
to illustrate a range of phenomena that further emphasize the strong
interaction of the global-scale magnetic systems of the Hale Cycle: the
vast majority, 96%, of all X-flares happen between the Terminator and
pre-Terminator. In addition to the X-rays from violent flares, rapid
changes in the number of energetic photons—EUV spectral emission
from a hot corona and the F10.7 solar radio flux—impinging on the
atmosphere are predictable from the Terminator-normalized unit cycle,
which has implications for improving the fidelity of atmospheric
modelling.
Title: Deciphering Solar Magnetic Activity. The Solar Cycle Clock
Authors: Leamon, Robert; McIntosh, Scott; Title, Alan
Bibcode: 2020arXiv201215186L
Altcode:
The Sun's variability is controlled by the progression and interaction
of the magnetized systems that form the 22-year magnetic activity cycle
(the "Hale Cycle'') as they march from their origin at $\sim$55 degrees
latitude to the equator, over $\sim$19 years. We will discuss the end
point of that progression, dubbed "terminator'' events, and our means
of diagnosing them. Based on the terminations of Hale Magnetic Cycles,
we construct a new solar activity 'clock' which maps all solar magnetic
activity onto a single normalized epoch. The Terminators appear at
phase $0 * 2\pi$ on this clock (by definition), then solar polar
field reversals commence at $\sim0.2 * 2\pi$, and the geomagnetically
quiet intervals centered around solar minimum, start at $\sim0.6 *
2\pi$ and end at the terminator, lasting 40% of the normalized cycle
length. With this onset of quiescence, dubbed a "pre-terminator,''
the Sun shows a radical reduction in active region complexity and (like
the terminator events) is associated with the time when the solar radio
flux crosses F10.7=90 sfu -- effectively marking the commencement of
solar minimum conditions. In this paper we use the terminator-based
clock to illustrate a range of phenomena that further emphasize the
strong interaction of the global-scale magnetic systems of the Hale
Cycle. arXiv:2010.06048 is a companion article.
Title: Small satellites for space science. A COSPAR scientific roadmap
Authors: Millan, Robyn M.; von Steiger, Rudolf; Ariel, Meir; Bartalev,
Sergey; Borgeaud, Maurice; Campagnola, Stefano; Castillo-Rogez, Julie
C.; Fléron, René; Gass, Volker; Gregorio, Anna; Klumpar, David M.;
Lal, Bhavya; Macdonald, Malcolm; Park, Jong Uk; Sambasiva Rao, V.;
Schilling, Klaus; Stephens, Graeme; Title, Alan M.; Wu, Ji
Bibcode: 2019AdSpR..64.1466M
Altcode:
This is a COSPAR roadmap to advance the frontiers of science through
innovation and international collaboration using small satellites. The
world of small satellites is evolving quickly and an opportunity
exists to leverage these developments to make scientific progress. In
particular, the increasing availability of low-cost launch and
commercially available hardware provides an opportunity to reduce the
overall cost of science missions. This in turn should increase flight
rates and encourage scientists to propose more innovative concepts,
leading to scientific breakthroughs. Moreover, new computer technologies
and methods are changing the way data are acquired, managed, and
processed. The large data sets enabled by small satellites will
require a new paradigm for scientific data analysis. In this roadmap
we provide several examples of long-term scientific visions that could
be enabled by the small satellite revolution. For the purpose of this
report, the term "small satellite" is somewhat arbitrarily defined as
a spacecraft with an upper mass limit in the range of a few hundred
kilograms. The mass limit is less important than the processes used
to build and launch these satellites. The goal of this roadmap is
to encourage the space science community to leverage developments in
the small satellite industry in order to increase flight rates, and
change the way small science satellites are built and managed. Five
recommendations are made; one each to the science community, to space
industry, to space agencies, to policy makers, and finally, to COSPAR.
Title: Community Input Solicited for Heliophysics Decadal Survey
Midterm Assessment Committee
Authors: Woods, Thomas; Millan, Robyn; Charo, Art; Bastian, Tim;
Bobra, Monica; Coster, Anthea; DeLuca, Ed; England, Scott; Fuselier,
Stephen; Lopez, Ramon; Luhmann, Janet; Nykyri, Katariina; Oberheide,
Jens; Opher, Merav; Schrijver, Karel; Semeter, Josh; Thayer, Jeff;
Title, Alan
Bibcode: 2019shin.confE...6W
Altcode:
The National Academies of Sciences, Engineering, and Medicine has
convened a committee to review the progress towards implementing the
2013 Heliophysics Decadal Survey, titled Solar and Space Physics: a
Science for a Technological Society. This review serves as a midterm
assessment before the next Heliophysics Decadal Survey committee would
begin its formulation. This committee is interested to receive input
from the heliophysics and space weather communities about the 2013-2018
progress realizing the 15 recommendations and applications specified in
the 2013 Heliophysics Decadal Survey, about any suggested actions to
optimize the science value during 2019-2023, about any suggestions to
improve the process for the next Heliophysics Decadal Survey, and about
any suggested actions to enhance all stages of careers for scientists
and engineers in the solar and space physics community. This poster
outlines the Heliophysics Decadal Survey recommendations and recent
progress, and it also summarizes the tasks for this midterm assessment
committee. There will be an opportunity to discuss your inputs with
a couple of the Committee members during the SHINE meeting.
Title: Chapter 12 - Observations of the Sun from Space
Authors: Title, Alan
Bibcode: 2019sgsp.book..387T
Altcode: 2019sgsp.book..387.
This chapter summarizes how observations of the Sun from space have
revolutionized the understanding of our star. In space, instruments can
observe the Sun in spectral regions that are absorbed by the Earth's
atmosphere. Equally important is the ability to make long-duration,
high-spatial, and spectral-resolution observations that are impossible
to obtain on the ground even with a network of telescopes that span
the Earth. It is impossible to cover the hundreds of rocket, balloon,
and satellite missions that have contributed to our current knowledge
of solar processes, but an attempt has been made to capture how data
from space have increased our understanding of the Sun. The chapter
also tries to put the development of space solar physics into the
context of national and international political, national security,
and scientific goals. Early in the Space Age, an "open sky policy" was
accepted internationally: space has no national boundaries. The chapter
also tracks how the traditional science policy of data ownership by
the developers of experiments evolved into open data policies that were
gradually supported by national governments that funded the scientists.
Title: Solar Physics from Unconventional Viewpoints
Authors: Gibson, Sarah E.; Vourlidas, Angelos; Hassler, Donald M.;
Rachmeler, Laurel A.; Thompson, Michael J.; Newmark, Jeffrey; Velli,
Marco; Title, Alan; McIntosh, Scott W.
Bibcode: 2018FrASS...5...32G
Altcode: 2018arXiv180509452G
We explore new opportunities for solar physics that could be realized
by future missions providing sustained observations from vantage
points away from the Sun-Earth line. These include observations from
the far side of the Sun, at high latitudes including over the solar
poles, or from near-quadrature angles relative to the Earth (e.g.,
the Sun-Earth L4 and L5 Lagrangian points). Such observations fill
known holes in our scientific understanding of the three-dimensional,
time-evolving Sun and heliosphere, and have the potential to open new
frontiers through discoveries enabled by novel viewpoints.
Title: Solar Observations Away from the Sun-Earth Line
Authors: Gibson, Sarah E.; McIntosh, Scott William; Rachmeler,
Laurel; Thompson, Michael J.; Title, Alan M.; Velli, Marco C. M.;
Vourlidas, Angelos
Bibcode: 2018tess.conf40340G
Altcode:
Observations from satellite missions have transformed the field of solar
physics. High-resolution observations with near-continuous temporal
coverage have greatly extended our capability for studying long-term
and transient phenomena, and the opening of new regions of the solar
spectrum has made detailed investigation of the solar atmosphere
possible. However, to date most solar space-based missions
have been restricted to an observational vantage in the vicinity of
the Sun-Earth line, either in orbit around the Earth or from the L1
Lagrangian point. As a result, observations from these satellites
represent the same geometrical view of the Sun that is accessible
from the Earth. Understanding the deep interior structure of the
Sun and the full development of solar activity would really benefit
from fully three-dimensional monitoring of the solar atmosphere and
heliosphere. On the one hand, simultaneous spacecraft observations
from multiple vantage points would allow studies of the deep interior
structure of the sun via stereoscopic helioseismology; on the other,
distributed observations would allow the understanding of the complete
evolution of activity complexes and enhance space weather predictions
dramatically. Presently, observations of the Sun away from Earth
are obtained by the STEREO pair of satellites, which have provided
an unprecedented global view by orbiting around to the far side of
the Sun, and the Ulysses mission, which achieved a high-inclination
(80˚) near-polar orbit (but which, however, did not include any solar
imaging instruments). The forthcoming Solar Orbiter mission, which
will orbit the sun and reach a maximum inclination of 34˚ out of the
ecliptic should provide the first detailed mapping of the sun's polar
fields. In addition, Solar Probe Plus will explore the outer corona
and inner Heliosphere with very rapid solar encounters at a minimum
perihelion 9.86 solar radii from the center of the Sun. We explore
some of the new opportunities for solar physics that can be realized
by future missions that provide sustained observations from vantage
points away from the Sun-Earth line (and in some cases the ecliptic
plane): observations from the far side of the Sun, over its poles,
or from the L5 Lagrangian point.
Title: Flare Clustering
Authors: Title, A. M.
Bibcode: 2016AGUFMSH43E..01T
Altcode:
The continuous full disk observations provided by the Atmospheric
Imaging Assembly (AIA ) can give an observer the impression that
many flare eruptions are causally related to one another. However,
both detailed analyses of a number of events as well as several
statistical studies have provided only rare examples or weak evidence
of causal behavior. Since the mechanisms of flare triggering are not
well understood, the lack of hard evidence is not surprising. For
this study we looked instead for groups of flares (flare clusters)
in which successive flares occur within a fixed time - the selection
time. The data set used for the investigation is the flare waiting
times provided by the X-ray flare detectors on the Geostationary
Operational Environmental Satellites (GOES). We limited the study
to flares of magnitude C5 and greater obtained during cycles 21,
22, 23, and 24. The GOES field of view includes the entire visible
surface. While many flares in a cluster may come from the same active
region, the larger clusters often have origins in multiple regions. The
longest C5 cluster found with a linking window of 36 hours in cycles
21, 22, 23,and 24 was 54, 82, 42, and 18 days, respectively. X flares
also cluster. A superposed epoch analyses demonstrates that there is
a pronounced enhancement of number of C5 and and above flares that are
centered on the X flare clusters. We suggest that this behavior implies
that a component of the observed coordinated behavior originates from
the MHD processes driven by the solar dynamo that in turn creates
unstable states in the solar atmosphere. The relationship between
flare clusters and magnetic centers of activity was explored as was
the correlation between high flare rates and significant changes in
the total solar magnetic flux,
Title: Flare Clustering
Authors: Title, Alan; DeRosa, Marc
Bibcode: 2016usc..confE..50T
Altcode:
The continuous full disk observations provided by the Atmospheric
Imaging Assembly (AIA ) can give an observer the impression that
many flare eruptions are causally related to one another. However,
both detailed analyses of a number of events as well as several
statistical studies have provided only rare examples or weak evidence
of causal behavior. Since the mechanisms of flare triggering are not
well understood, the lack of hard evidence is not surprising. For
this study we looked instead for groups of flares (flare clusters)
in which successive flares occur within a fixed time - the selection
time. The data set used for the investigation is the flare waiting
times provided by the X-ray flare detectors on the Geostationary
Operational Environmental Satellites (GOES). We limited the study
to flares of magnitude C5 and greater obtained during cycles 21,
22, 23, and 24. The GOES field of view includes the entire visible
surface. While many flares in a cluster may come from the same active
region, the larger clusters often have origins in multiple regions. The
longest C5 cluster found with a linking window of 36 hours in cycles
21, 22, 23,and 24 was 54, 82, 42, and 18 days, respectively. X flares
also cluster. A superposed epoch analyses demonstrates that there is
a pronounced enhancement of number of C5 and and above flares that are
centered on the X flare clusters. We suggest that this behavior implies
that a component of the observed coordinated behavior originates from
the MHD processes driven by the solar dynamo that in turn creates
unstable states in the solar atmosphere. The relationship between
flare clusters and magnetic centers of activity was explored as was
the correlation between high flare rates and significant changes in
the total solar magnetic flux,
Title: a Numerical Study of Long-Range Magnetic Impacts during
Coronal Mass Ejections
Authors: Jin, Meng; Schrijver, Karel; Cheung, Mark; DeRosa, Marc;
Nitta, Nariaki; Title, Alan
Bibcode: 2016shin.confE..38J
Altcode:
With the global view and high-cadence observations from SDO/AIA and
STEREO, many spatially separated solar eruptive events appear to be
coupled. However, the mechanisms for 'sympathetic' events are still
largely unknown. In this study, we investigate the impact of an erupting
flux rope on surrounding solar structures through large-scale magnetic
coupling. We build a realistic environment of the solar corona on
2011 February 15 using a global magnetohydrodynamics (MHD) model and
initiate coronal mass ejections (CMEs) in active region (AR) 11158
by inserting Gibson-Low analytical flux ropes. We show that a CME's
impact on the surrounding structures depends not only on the magnetic
strength of these structures and their distance to the source region,
but also on the interaction between the CME with the large-scale
magnetic field. Within the CME expansion domain where the flux rope
field directly interacts with the solar structures, expansion-induced
reconnection often modifies the overlying field, thereby increasing
the decay index. This effect may provide a primary coupling mechanism
underlying the sympathetic eruptions. The magnitude of the impact
is found to depend on the orientation of the erupting flux rope,
with the largest impacts occurring when the flux rope is favorably
oriented for reconnecting with the surrounding regions. Outside the
CME expansion domain, the influence of the CME is mainly through field
line compression or post-eruption relaxation. Based on our numerical
experiments, we discuss a way to quantify the eruption impact, which
could be useful for forecasting purposes.
Title: A Numerical Study of Long-range Magnetic Impacts during
Coronal Mass Ejections
Authors: Jin, M.; Schrijver, C. J.; Cheung, M. C. M.; DeRosa, M. L.;
Nitta, N. V.; Title, A. M.
Bibcode: 2016ApJ...820...16J
Altcode: 2016arXiv160304900J
With the global view and high-cadence observations from Solar Dynamics
Observatory/Atmospheric Imaging Assembly and Solar TErrestrial RElations
Observatory, many spatially separated solar eruptive events appear
to be coupled. However, the mechanisms for “sympathetic” events
are still largely unknown. In this study, we investigate the impact
of an erupting flux rope on surrounding solar structures through
large-scale magnetic coupling. We build a realistic environment of the
solar corona on 2011 February 15 using a global magnetohydrodynamics
model and initiate coronal mass ejections (CMEs) in active region
11158 by inserting Gibson-Low analytical flux ropes. We show that a
CME’s impact on the surrounding structures depends not only on the
magnetic strength of these structures and their distance to the source
region, but also on the interaction between the CME and the large-scale
magnetic field. Within the CME expansion domain where the flux rope
field directly interacts with the solar structures, expansion-induced
reconnection often modifies the overlying field, thereby increasing
the decay index. This effect may provide a primary coupling mechanism
underlying the sympathetic eruptions. The magnitude of the impact
is found to depend on the orientation of the erupting flux rope,
with the largest impacts occurring when the flux rope is favorably
oriented for reconnecting with the surrounding regions. Outside the
CME expansion domain, the influence of the CME is mainly through field
line compression or post-eruption relaxation. Based on our numerical
experiments, we discuss a way to quantify the eruption impact, which
could be useful for forecasting purposes.
Title: The Role of Large-scale Magnetic Coupling for Solar Corona
Sympathy
Authors: Jin, M.; Schrijver, K.; Cheung, C. M. M.; DeRosa, M. L.;
Nitta, N.; Title, A. M.
Bibcode: 2015AGUFMSH23A2425J
Altcode:
With the comprehensive view and high cadence observations from
SDO/AIA and STEREO in solar cycle 24, a large number of spatially
separated solar eruptive events are found to be coupled. However,
compared with the established initiation mechanisms for "isolated"
events, the mechanisms for "sympathetic" events are still largely
unknown, and nascent theories are untested. In this study, we build
a realistic environment of solar corona on 2011 February 15 using
a global MHD model and investigate how an eruption can impact the
surrounding solar structures. Our result shows that the solar eruption's
impact on the different structures can be quite different. Within
the CME expansion domain, it is possible to trigger an eruption by
overlaying field removal through expansion induced reconnection. The
magnitude of impact is found to be dependent on the orientation
of the erupting flux rope. Outside the CME expansion domain, the
post-eruption reconfiguration could play an important role for solar
sympathy. Based on the modeling results, we discuss the possibility of
using observable/estimable parameters to quantify the eruption impact
therefore providing an useful parameter for forecasting sympathy.
Title: Modified Rossby Waves in the Solar Interior
Authors: McIntosh, Scott W.; Title, Alan M.; Leamon, Robert J.
Bibcode: 2015TESS....110501M
Altcode:
Using a combination of STEREO/SECCHI/EUVI and SDO/AIA imaging we reveal
patterns in the imaging data that are consistent in appearance with
global scale rotationally driven waves on the activity bands of the
solar magnetic polarity cycle.
Title: First High-resolution Spectroscopic Observations of an Erupting
Prominence Within a Coronal Mass Ejection by the Interface Region
Imaging Spectrograph (IRIS)
Authors: Liu, Wei; De Pontieu, Bart; Vial, Jean-Claude; Title, Alan
M.; Carlsson, Mats; Uitenbroek, Han; Okamoto, Takenori J.; Berger,
Thomas E.; Antolin, Patrick
Bibcode: 2015ApJ...803...85L
Altcode: 2015arXiv150204738L
Spectroscopic observations of prominence eruptions associated with
coronal mass ejections (CMEs), although relatively rare, can provide
valuable plasma and three-dimensional geometry diagnostics. We report
the first observations by the Interface Region Imaging Spectrograph
mission of a spectacular fast CME/prominence eruption associated with
an equivalent X1.6 flare on 2014 May 9. The maximum plane-of-sky and
Doppler velocities of the eruption are 1200 and 460 km s-1,
respectively. There are two eruption components separated by ∼200
km s-1 in Doppler velocity: a primary, bright component
and a secondary, faint component, suggesting a hollow, rather than
solid, cone-shaped distribution of material. The eruption involves
a left-handed helical structure undergoing counterclockwise (viewed
top-down) unwinding motion. There is a temporal evolution from upward
eruption to downward fallback with less-than-free-fall speeds and
decreasing nonthermal line widths. We find a wide range of Mg ii k/h
line intensity ratios (less than ∼2 expected for optically-thin
thermal emission): the lowest ever reported median value of 1.17
found in the fallback material, a comparably high value of 1.63 in
nearby coronal rain, and intermediate values of 1.53 and 1.41 in
the two eruption components. The fallback material exhibits a strong
(\gt 5σ ) linear correlation between the k/h ratio and the Doppler
velocity as well as the line intensity. We demonstrate that Doppler
dimming of scattered chromospheric emission by the erupted material
can potentially explain such characteristics.
Title: The solar magnetic activity band interaction and instabilities
that shape quasi-periodic variability
Authors: McIntosh, Scott W.; Leamon, Robert J.; Krista, Larisza D.;
Title, Alan M.; Hudson, Hugh S.; Riley, Pete; Harder, Jerald W.; Kopp,
Greg; Snow, Martin; Woods, Thomas N.; Kasper, Justin C.; Stevens,
Michael L.; Ulrich, Roger K.
Bibcode: 2015NatCo...6.6491M
Altcode: 2015NatCo...6E6491M
Solar magnetism displays a host of variational timescales of which
the enigmatic 11-year sunspot cycle is most prominent. Recent work
has demonstrated that the sunspot cycle can be explained in terms of
the intra- and extra-hemispheric interaction between the overlapping
activity bands of the 22-year magnetic polarity cycle. Those
activity bands appear to be driven by the rotation of the Sun's
deep interior. Here we deduce that activity band interaction can
qualitatively explain the `Gnevyshev Gap'--a well-established feature
of flare and sunspot occurrence. Strong quasi-annual variability in the
number of flares, coronal mass ejections, the radiative and particulate
environment of the heliosphere is also observed. We infer that this
secondary variability is driven by surges of magnetism from the activity
bands. Understanding the formation, interaction and instability of
these activity bands will considerably improve forecast capability in
space weather and solar activity over a range of timescales.
Title: Internetwork Chromospheric Bright Grains Observed With IRIS
and SST
Authors: Martínez-Sykora, Juan; Rouppe van der Voort, Luc; Carlsson,
Mats; De Pontieu, Bart; Pereira, Tiago M. D.; Boerner, Paul; Hurlburt,
Neal; Kleint, Lucia; Lemen, James; Tarbell, Ted D.; Title, Alan;
Wuelser, Jean-Pierre; Hansteen, Viggo H.; Golub, Leon; McKillop, Sean;
Reeves, Kathy K.; Saar, Steven; Testa, Paola; Tian, Hui; Jaeggli,
Sarah; Kankelborg, Charles
Bibcode: 2015ApJ...803...44M
Altcode: 2015arXiv150203490M
The Interface Region Imaging Spectrograph (IRIS) reveals small-scale
rapid brightenings in the form of bright grains all over coronal holes
and the quiet Sun. These bright grains are seen with the IRIS 1330,
1400, and 2796 Å slit-jaw filters. We combine coordinated observations
with IRIS and from the ground with the Swedish 1 m Solar Telescope
(SST) which allows us to have chromospheric (Ca ii 8542 Å, Ca ii H
3968 Å, Hα, and Mg ii k 2796 Å) and transition region (C ii 1334 Å,
Si iv 1403 Å) spectral imaging, and single-wavelength Stokes maps
in Fe i 6302 Å at high spatial (0\buildrel{\prime\prime}\over{.}
33), temporal, and spectral resolution. We conclude that the IRIS
slit-jaw grains are the counterpart of so-called acoustic grains,
i.e., resulting from chromospheric acoustic waves in a non-magnetic
environment. We compare slit-jaw images (SJIs) with spectra from the
IRIS spectrograph. We conclude that the grain intensity in the 2796
Å slit-jaw filter comes from both the Mg ii k core and wings. The
signal in the C ii and Si iv lines is too weak to explain the presence
of grains in the 1300 and 1400 Å SJIs and we conclude that the grain
signal in these passbands comes mostly from the continuum. Although
weak, the characteristic shock signatures of acoustic grains can often
be detected in IRIS C ii spectra. For some grains, a spectral signature
can be found in IRIS Si iv. This suggests that upward propagating
acoustic waves sometimes reach all the way up to the transition region.
Title: Flare Clustering
Authors: Title, Alan M.
Bibcode: 2015TESS....140602T
Altcode:
In this study we tested for groups of flares (flare clusters) in which
successive flares occur within a fixed time - the linking window. The
data set used is the flare waiting times provided by the X-ray flare
detectors on the Geostationary Operational Environmental Satellites
(GOES). The study was limited to flares of magnitude C5 and greater
obtained during cycle 23. While many flares in a cluster may come
from the same active region, the larger clusters often have origins in
multiple regions. The longest cluster of the last cycle lasted more than
42 days with an average time separation between successive flares of 5
hours, where no two flares were separated by more than 36 hours. The
flare rate in clusters is 4 to 6 time greater than the rate in solar
maximum outside of flares. The are indications that flare clustering
is associated with periods of multiple sunspot nests, but they are
much rarer.
Title: Homologous Helical Jets: Observations By IRIS, SDO, and Hinode
and Magnetic Modeling With Data-Driven Simulations
Authors: Cheung, Mark C. M.; De Pontieu, B.; Tarbell, T. D.; Fu, Y.;
Tian, H.; Testa, P.; Reeves, K. K.; Martínez-Sykora, J.; Boerner,
P.; Wülser, J. P.; Lemen, J.; Title, A. M.; Hurlburt, N.; Kleint,
L.; Kankelborg, C.; Jaeggli, S.; Golub, L.; McKillop, S.; Saar, S.;
Carlsson, M.; Hansteen, V.
Bibcode: 2015ApJ...801...83C
Altcode: 2015arXiv150101593C
We report on observations of recurrent jets by instruments on board
the Interface Region Imaging Spectrograph, Solar Dynamics Observatory
(SDO), and Hinode spacecraft. Over a 4 hr period on 2013 July 21,
recurrent coronal jets were observed to emanate from NOAA Active Region
11793. Far-ultraviolet spectra probing plasma at transition region
temperatures show evidence of oppositely directed flows with components
reaching Doppler velocities of ±100 km s-1. Raster Doppler
maps using a Si iv transition region line show all four jets to have
helical motion of the same sense. Simultaneous observations of the
region by SDO and Hinode show that the jets emanate from a source
region comprising a pore embedded in the interior of a supergranule. The
parasitic pore has opposite polarity flux compared to the surrounding
network field. This leads to a spine-fan magnetic topology in the
coronal field that is amenable to jet formation. Time-dependent
data-driven simulations are used to investigate the underlying drivers
for the jets. These numerical experiments show that the emergence of
current-carrying magnetic field in the vicinity of the pore supplies
the magnetic twist needed for recurrent helical jet formation.
Title: First High-resolution Spectroscopic Observations by IRIS
of a Fast, Helical Prominence Eruption Associated with a Coronal
Mass Ejection
Authors: Liu, W.; De Pontieu, B.; Okamoto, T. J.; Vial, J. C.; Title,
A. M.; Antolin, P.; Berger, T. E.; Uitenbroek, H.
Bibcode: 2014AGUFMSH11D..04L
Altcode:
High-resolution spectroscopic observations of prominence eruptions and
associated coronal mass ejections (CMEs) are rare but can provide
valuable plasma and energy diagnostics. New opportunities have
recently become available with the advent of the Interface Region
Imaging Spectrograph (IRIS) mission equipped with high resolution of
0.33-0.4 arcsec in space and 1 km/s in velocity, together with the
Hinode Solar Optical Telescope of 0.2 arcsec spatial resolution. We
report the first result of joint IRIS-Hinode observations of a
spectacular prominence eruption occurring on 2014-May-09. IRIS
detected a maximum redshift of 450 km/s, which, combined with the
plane-of-sky speed of 800 km/s, gives a large velocity vector of 920
km/s at 30 degrees from the sky plane. This direction agrees with the
source location at 30 degrees behind the limb observed by STEREO-A
and indicates a nearly vertical ejection. We found two branches of
redshifts separated by 200 km/s appearing in all strong lines at
chromospheric to transition-region temperatures, including Mg II k/h,
C II, and Si IV, suggesting a hollow, rather than solid, cone in the
velocity space of the ejected material. Opposite blue- and redshifts
on the two sides of the prominence exhibit corkscrew variations both
in space and time, suggestive of unwinding rotations of a left-handed
helical flux rope. Some erupted material returns as nearly streamline
flows, exhibiting distinctly narrow line widths (~10 km/s), about
50% of those of the nearby coronal rain at the apexes of coronal
loops, where the rain material is initially formed out of cooling
condensation. We estimate the mass and kinetic energy of the ejected
and returning material and compare them with those of the associated
CME. We will discuss the implications of these observations for CME
initiation mechanisms.
Title: The High-Resolution Coronal Imager (Hi-C)
Authors: Kobayashi, Ken; Cirtain, Jonathan; Winebarger, Amy R.;
Korreck, Kelly; Golub, Leon; Walsh, Robert W.; De Pontieu, Bart;
DeForest, Craig; Title, Alan; Kuzin, Sergey; Savage, Sabrina; Beabout,
Dyana; Beabout, Brent; Podgorski, William; Caldwell, David; McCracken,
Kenneth; Ordway, Mark; Bergner, Henry; Gates, Richard; McKillop,
Sean; Cheimets, Peter; Platt, Simon; Mitchell, Nick; Windt, David
Bibcode: 2014SoPh..289.4393K
Altcode: 2014SoPh..tmp..104K
The High-Resolution Coronal Imager (Hi-C) was flown on a NASA sounding
rocket on 11 July 2012. The goal of the Hi-C mission was to obtain
high-resolution (≈ 0.3 - 0.4''), high-cadence (≈ 5 seconds)
images of a solar active region to investigate the dynamics of solar
coronal structures at small spatial scales. The instrument consists of
a normal-incidence telescope with the optics coated with multilayers
to reflect a narrow wavelength range around 19.3 nm (including the
Fe XII 19.5-nm spectral line) and a 4096×4096 camera with a plate
scale of 0.1'' pixel−1. The target of the Hi-C rocket
flight was Active Region 11520. Hi-C obtained 37 full-frame images
and 86 partial-frame images during the rocket flight. Analysis of the
Hi-C data indicates the corona is structured on scales smaller than
currently resolved by existing satellite missions.
Title: Probing the solar interface region
Authors: De Pontieu, Bart; Title, Alan; Carlsson, Mats
Bibcode: 2014Sci...346..315D
Altcode:
No abstract at ADS
Title: Hot explosions in the cool atmosphere of the Sun
Authors: Peter, H.; Tian, H.; Curdt, W.; Schmit, D.; Innes, D.;
De Pontieu, B.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt, N.;
Tarbell, T. D.; Wuelser, J. P.; Martínez-Sykora, Juan; Kleint,
L.; Golub, L.; McKillop, S.; Reeves, K. K.; Saar, S.; Testa, P.;
Kankelborg, C.; Jaeggli, S.; Carlsson, M.; Hansteen, V.
Bibcode: 2014Sci...346C.315P
Altcode: 2014arXiv1410.5842P
The solar atmosphere was traditionally represented with a simple
one-dimensional model. Over the past few decades, this paradigm shifted
for the chromosphere and corona that constitute the outer atmosphere,
which is now considered a dynamic structured envelope. Recent
observations by the Interface Region Imaging Spectrograph (IRIS) reveal
that it is difficult to determine what is up and down, even in the cool
6000-kelvin photosphere just above the solar surface: This region hosts
pockets of hot plasma transiently heated to almost 100,000 kelvin. The
energy to heat and accelerate the plasma requires a considerable
fraction of the energy from flares, the largest solar disruptions. These
IRIS observations not only confirm that the photosphere is more complex
than conventionally thought, but also provide insight into the energy
conversion in the process of magnetic reconnection.
Title: The unresolved fine structure resolved: IRIS observations of
the solar transition region
Authors: Hansteen, V.; De Pontieu, B.; Carlsson, M.; Lemen, J.; Title,
A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser, J. P.; Pereira,
T. M. D.; De Luca, E. E.; Golub, L.; McKillop, S.; Reeves, K.; Saar,
S.; Testa, P.; Tian, H.; Kankelborg, C.; Jaeggli, S.; Kleint, L.;
Martínez-Sykora, J.
Bibcode: 2014Sci...346E.315H
Altcode: 2014arXiv1412.3611H
The heating of the outer solar atmospheric layers, i.e., the transition
region and corona, to high temperatures is a long-standing problem
in solar (and stellar) physics. Solutions have been hampered by an
incomplete understanding of the magnetically controlled structure of
these regions. The high spatial and temporal resolution observations
with the Interface Region Imaging Spectrograph (IRIS) at the solar
limb reveal a plethora of short, low-lying loops or loop segments
at transition-region temperatures that vary rapidly, on the time
scales of minutes. We argue that the existence of these loops solves
a long-standing observational mystery. At the same time, based on
comparison with numerical models, this detection sheds light on a
critical piece of the coronal heating puzzle.
Title: Evidence of nonthermal particles in coronal loops heated
impulsively by nanoflares
Authors: Testa, P.; De Pontieu, B.; Allred, J.; Carlsson, M.; Reale,
F.; Daw, A.; Hansteen, V.; Martinez-Sykora, J.; Liu, W.; DeLuca, E. E.;
Golub, L.; McKillop, S.; Reeves, K.; Saar, S.; Tian, H.; Lemen, J.;
Title, A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser, J. P.;
Kleint, L.; Kankelborg, C.; Jaeggli, S.
Bibcode: 2014Sci...346B.315T
Altcode: 2014arXiv1410.6130T
The physical processes causing energy exchange between the Sun’s
hot corona and its cool lower atmosphere remain poorly understood. The
chromosphere and transition region (TR) form an interface region between
the surface and the corona that is highly sensitive to the coronal
heating mechanism. High-resolution observations with the Interface
Region Imaging Spectrograph (IRIS) reveal rapid variability (~20 to
60 seconds) of intensity and velocity on small spatial scales (≲500
kilometers) at the footpoints of hot and dynamic coronal loops. The
observations are consistent with numerical simulations of heating by
beams of nonthermal electrons, which are generated in small impulsive
(≲30 seconds) heating events called “coronal nanoflares.” The
accelerated electrons deposit a sizable fraction of their energy
(≲1025 erg) in the chromosphere and TR. Our analysis
provides tight constraints on the properties of such electron beams
and new diagnostics for their presence in the nonflaring corona.
Title: Prevalence of small-scale jets from the networks of the solar
transition region and chromosphere
Authors: Tian, H.; DeLuca, E. E.; Cranmer, S. R.; De Pontieu, B.;
Peter, H.; Martínez-Sykora, J.; Golub, L.; McKillop, S.; Reeves,
K. K.; Miralles, M. P.; McCauley, P.; Saar, S.; Testa, P.; Weber,
M.; Murphy, N.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt, N.;
Tarbell, T. D.; Wuelser, J. P.; Kleint, L.; Kankelborg, C.; Jaeggli,
S.; Carlsson, M.; Hansteen, V.; McIntosh, S. W.
Bibcode: 2014Sci...346A.315T
Altcode: 2014arXiv1410.6143T
As the interface between the Sun’s photosphere and corona, the
chromosphere and transition region play a key role in the formation and
acceleration of the solar wind. Observations from the Interface Region
Imaging Spectrograph reveal the prevalence of intermittent small-scale
jets with speeds of 80 to 250 kilometers per second from the narrow
bright network lanes of this interface region. These jets have lifetimes
of 20 to 80 seconds and widths of ≤300 kilometers. They originate from
small-scale bright regions, often preceded by footpoint brightenings
and accompanied by transverse waves with amplitudes of ~20 kilometers
per second. Many jets reach temperatures of at least ~105
kelvin and constitute an important element of the transition region
structures. They are likely an intermittent but persistent source of
mass and energy for the solar wind.
Title: On the prevalence of small-scale twist in the solar
chromosphere and transition region
Authors: De Pontieu, B.; Rouppe van der Voort, L.; McIntosh, S. W.;
Pereira, T. M. D.; Carlsson, M.; Hansteen, V.; Skogsrud, H.; Lemen,
J.; Title, A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser,
J. P.; De Luca, E. E.; Golub, L.; McKillop, S.; Reeves, K.; Saar,
S.; Testa, P.; Tian, H.; Kankelborg, C.; Jaeggli, S.; Kleint, L.;
Martinez-Sykora, J.
Bibcode: 2014Sci...346D.315D
Altcode: 2014arXiv1410.6862D
The solar chromosphere and transition region (TR) form an interface
between the Sun’s surface and its hot outer atmosphere. There,
most of the nonthermal energy that powers the solar atmosphere
is transformed into heat, although the detailed mechanism remains
elusive. High-resolution (0.33-arc second) observations with NASA’s
Interface Region Imaging Spectrograph (IRIS) reveal a chromosphere
and TR that are replete with twist or torsional motions on sub-arc
second scales, occurring in active regions, quiet Sun regions, and
coronal holes alike. We coordinated observations with the Swedish
1-meter Solar Telescope (SST) to quantify these twisting motions and
their association with rapid heating to at least TR temperatures. This
view of the interface region provides insight into what heats the low
solar atmosphere.
Title: An Interface Region Imaging Spectrograph First View on Solar
Spicules
Authors: Pereira, T. M. D.; De Pontieu, B.; Carlsson, M.; Hansteen,
V.; Tarbell, T. D.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt,
N.; Wülser, J. P.; Martínez-Sykora, J.; Kleint, L.; Golub, L.;
McKillop, S.; Reeves, K. K.; Saar, S.; Testa, P.; Tian, H.; Jaeggli,
S.; Kankelborg, C.
Bibcode: 2014ApJ...792L..15P
Altcode: 2014arXiv1407.6360P
Solar spicules have eluded modelers and observers for decades. Since
the discovery of the more energetic type II, spicules have become
a heated topic but their contribution to the energy balance of the
low solar atmosphere remains unknown. Here we give a first glimpse of
what quiet-Sun spicules look like when observed with NASA's recently
launched Interface Region Imaging Spectrograph (IRIS). Using IRIS
spectra and filtergrams that sample the chromosphere and transition
region, we compare the properties and evolution of spicules as
observed in a coordinated campaign with Hinode and the Atmospheric
Imaging Assembly. Our IRIS observations allow us to follow the thermal
evolution of type II spicules and finally confirm that the fading
of Ca II H spicules appears to be caused by rapid heating to higher
temperatures. The IRIS spicules do not fade but continue evolving,
reaching higher and falling back down after 500-800 s. Ca II H type
II spicules are thus the initial stages of violent and hotter events
that mostly remain invisible in Ca II H filtergrams. These events
have very different properties from type I spicules, which show lower
velocities and no fading from chromospheric passbands. The IRIS spectra
of spicules show the same signature as their proposed disk counterparts,
reinforcing earlier work. Spectroheliograms from spectral rasters also
confirm that quiet-Sun spicules originate in bushes from the magnetic
network. Our results suggest that type II spicules are indeed the
site of vigorous heating (to at least transition region temperatures)
along extensive parts of the upward moving spicular plasma.
Title: The Interface Region Imaging Spectrograph (IRIS)
Authors: De Pontieu, B.; Title, A. M.; Lemen, J. R.; Kushner, G. D.;
Akin, D. J.; Allard, B.; Berger, T.; Boerner, P.; Cheung, M.; Chou,
C.; Drake, J. F.; Duncan, D. W.; Freeland, S.; Heyman, G. F.; Hoffman,
C.; Hurlburt, N. E.; Lindgren, R. W.; Mathur, D.; Rehse, R.; Sabolish,
D.; Seguin, R.; Schrijver, C. J.; Tarbell, T. D.; Wülser, J. -P.;
Wolfson, C. J.; Yanari, C.; Mudge, J.; Nguyen-Phuc, N.; Timmons,
R.; van Bezooijen, R.; Weingrod, I.; Brookner, R.; Butcher, G.;
Dougherty, B.; Eder, J.; Knagenhjelm, V.; Larsen, S.; Mansir, D.;
Phan, L.; Boyle, P.; Cheimets, P. N.; DeLuca, E. E.; Golub, L.;
Gates, R.; Hertz, E.; McKillop, S.; Park, S.; Perry, T.; Podgorski,
W. A.; Reeves, K.; Saar, S.; Testa, P.; Tian, H.; Weber, M.; Dunn, C.;
Eccles, S.; Jaeggli, S. A.; Kankelborg, C. C.; Mashburn, K.; Pust, N.;
Springer, L.; Carvalho, R.; Kleint, L.; Marmie, J.; Mazmanian, E.;
Pereira, T. M. D.; Sawyer, S.; Strong, J.; Worden, S. P.; Carlsson,
M.; Hansteen, V. H.; Leenaarts, J.; Wiesmann, M.; Aloise, J.; Chu,
K. -C.; Bush, R. I.; Scherrer, P. H.; Brekke, P.; Martinez-Sykora,
J.; Lites, B. W.; McIntosh, S. W.; Uitenbroek, H.; Okamoto, T. J.;
Gummin, M. A.; Auker, G.; Jerram, P.; Pool, P.; Waltham, N.
Bibcode: 2014SoPh..289.2733D
Altcode: 2014arXiv1401.2491D; 2014SoPh..tmp...25D
The Interface Region Imaging Spectrograph (IRIS) small explorer
spacecraft provides simultaneous spectra and images of the photosphere,
chromosphere, transition region, and corona with 0.33 - 0.4 arcsec
spatial resolution, two-second temporal resolution, and 1 km
s−1 velocity resolution over a field-of-view of up to
175 arcsec × 175 arcsec. IRIS was launched into a Sun-synchronous
orbit on 27 June 2013 using a Pegasus-XL rocket and consists of a
19-cm UV telescope that feeds a slit-based dual-bandpass imaging
spectrograph. IRIS obtains spectra in passbands from 1332 - 1358 Å,
1389 - 1407 Å, and 2783 - 2834 Å, including bright spectral lines
formed in the chromosphere (Mg II h 2803 Å and Mg II k 2796 Å) and
transition region (C II 1334/1335 Å and Si IV 1394/1403 Å). Slit-jaw
images in four different passbands (C II 1330, Si IV 1400, Mg II k
2796, and Mg II wing 2830 Å) can be taken simultaneously with spectral
rasters that sample regions up to 130 arcsec × 175 arcsec at a variety
of spatial samplings (from 0.33 arcsec and up). IRIS is sensitive to
emission from plasma at temperatures between 5000 K and 10 MK and will
advance our understanding of the flow of mass and energy through an
interface region, formed by the chromosphere and transition region,
between the photosphere and corona. This highly structured and dynamic
region not only acts as the conduit of all mass and energy feeding
into the corona and solar wind, it also requires an order of magnitude
more energy to heat than the corona and solar wind combined. The
IRIS investigation includes a strong numerical modeling component
based on advanced radiative-MHD codes to facilitate interpretation of
observations of this complex region. Approximately eight Gbytes of data
(after compression) are acquired by IRIS each day and made available
for unrestricted use within a few days of the observation.
Title: Detection of Supersonic Downflows and Associated Heating
Events in the Transition Region above Sunspots
Authors: Kleint, L.; Antolin, P.; Tian, H.; Judge, P.; Testa, P.;
De Pontieu, B.; Martínez-Sykora, J.; Reeves, K. K.; Wuelser, J. P.;
McKillop, S.; Saar, S.; Carlsson, M.; Boerner, P.; Hurlburt, N.; Lemen,
J.; Tarbell, T. D.; Title, A.; Golub, L.; Hansteen, V.; Jaeggli, S.;
Kankelborg, C.
Bibcode: 2014ApJ...789L..42K
Altcode: 2014arXiv1406.6816K
Interface Region Imaging Spectrograph data allow us to study the solar
transition region (TR) with an unprecedented spatial resolution of
0.''33. On 2013 August 30, we observed bursts of high Doppler shifts
suggesting strong supersonic downflows of up to 200 km s-1
and weaker, slightly slower upflows in the spectral lines Mg II h
and k, C II 1336, Si IV 1394 Å, and 1403 Å, that are correlated
with brightenings in the slitjaw images (SJIs). The bursty behavior
lasts throughout the 2 hr observation, with average burst durations
of about 20 s. The locations of these short-lived events appear to
be the umbral and penumbral footpoints of EUV loops. Fast apparent
downflows are observed along these loops in the SJIs and in the
Atmospheric Imaging Assembly, suggesting that the loops are thermally
unstable. We interpret the observations as cool material falling
from coronal heights, and especially coronal rain produced along the
thermally unstable loops, which leads to an increase of intensity
at the loop footpoints, probably indicating an increase of density
and temperature in the TR. The rain speeds are on the higher end of
previously reported speeds for this phenomenon, and possibly higher
than the free-fall velocity along the loops. On other observing days,
similar bright dots are sometimes aligned into ribbons, resembling
small flare ribbons. These observations provide a first insight into
small-scale heating events in sunspots in the TR.
Title: A study of sympathetic eruptions using the Heliophysics
Events Knowledgebase
Authors: Higgins, Paul A.; Schrijver, Carolus J.; Title, Alan M.;
Bloomfield, D. Shaun; Gallagher, Peter T
Bibcode: 2014AAS...22412316H
Altcode:
Over the past few decades there have been a number of papers
investigating the connection between flares occurring in
succession. Statistically, any connection that affects the timing of
successive flares that exists is found to be weak. However, the majority
of previous investigations has been limited by only considering the
causal connection between soft X-ray flares. More recent case studies
have shown convincing evidence that large eruptions cause a global
reorganization of overlying magnetic fields that can result in the
eruption of both flares and filaments at large distances from the
original event. In this work, the connection between GOES X-ray flares
(C-, M-, and X-class) and filament eruptions occurring in succession in
two different active regions is considered statistically. The filament
eruptions are recorded in the Heliophysics Events Knowledgebase
by observers using SDO/AIA data. A significant causal connection is
found between the two event types, such that large flares are followed
by filament eruptions within 24 hours much more often than they are
preceded by filament eruptions. This stipulates that the flares either
cause the filaments to erupt or affect the eruption timing such that
the filament eruptions follow the flares more closely in time.
Title: High-resolution Observations of the Shock Wave Behavior for
Sunspot Oscillations with the Interface Region Imaging Spectrograph
Authors: Tian, H.; DeLuca, E.; Reeves, K. K.; McKillop, S.; De Pontieu,
B.; Martínez-Sykora, J.; Carlsson, M.; Hansteen, V.; Kleint, L.;
Cheung, M.; Golub, L.; Saar, S.; Testa, P.; Weber, M.; Lemen, J.;
Title, A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser, J. P.;
Kankelborg, C.; Jaeggli, S.; McIntosh, S. W.
Bibcode: 2014ApJ...786..137T
Altcode: 2014arXiv1404.6291T
We present the first results of sunspot oscillations from observations
by the Interface Region Imaging Spectrograph. The strongly nonlinear
oscillation is identified in both the slit-jaw images and the
spectra of several emission lines formed in the transition region and
chromosphere. We first apply a single Gaussian fit to the profiles of
the Mg II 2796.35 Å, C II 1335.71 Å, and Si IV 1393.76 Å lines in the
sunspot. The intensity change is ~30%. The Doppler shift oscillation
reveals a sawtooth pattern with an amplitude of ~10 km s-1
in Si IV. The Si IV oscillation lags those of C II and Mg II by ~3 and
~12 s, respectively. The line width suddenly increases as the Doppler
shift changes from redshift to blueshift. However, we demonstrate
that this increase is caused by the superposition of two emission
components. We then perform detailed analysis of the line profiles at
a few selected locations on the slit. The temporal evolution of the
line core is dominated by the following behavior: a rapid excursion
to the blue side, accompanied by an intensity increase, followed by a
linear decrease of the velocity to the red side. The maximum intensity
slightly lags the maximum blueshift in Si IV, whereas the intensity
enhancement slightly precedes the maximum blueshift in Mg II. We find
a positive correlation between the maximum velocity and deceleration,
a result that is consistent with numerical simulations of upward
propagating magnetoacoustic shock waves.
Title: Sparkling Extreme-ultraviolet Bright Dots Observed with Hi-C
Authors: Régnier, S.; Alexander, C. E.; Walsh, R. W.; Winebarger,
A. R.; Cirtain, J.; Golub, L.; Korreck, K. E.; Mitchell, N.; Platt,
S.; Weber, M.; De Pontieu, B.; Title, A.; Kobayashi, K.; Kuzin, S.;
DeForest, C. E.
Bibcode: 2014ApJ...784..134R
Altcode: 2014arXiv1402.2457R
Observing the Sun at high time and spatial scales is a step toward
understanding the finest and fundamental scales of heating events
in the solar corona. The high-resolution coronal (Hi-C) instrument
has provided the highest spatial and temporal resolution images of
the solar corona in the EUV wavelength range to date. Hi-C observed
an active region on 2012 July 11 that exhibits several interesting
features in the EUV line at 193 Å. One of them is the existence
of short, small brightenings "sparkling" at the edge of the active
region; we call these EUV bright dots (EBDs). Individual EBDs have a
characteristic duration of 25 s with a characteristic length of 680
km. These brightenings are not fully resolved by the SDO/AIA instrument
at the same wavelength; however, they can be identified with respect
to the Hi-C location of the EBDs. In addition, EBDs are seen in other
chromospheric/coronal channels of SDO/AIA, which suggests a temperature
between 0.5 and 1.5 MK. Based on their frequency in the Hi-C time
series, we define four different categories of EBDs: single peak,
double peak, long duration, and bursty. Based on a potential field
extrapolation from an SDO/HMI magnetogram, the EBDs appear at the
footpoints of large-scale, trans-equatorial coronal loops. The Hi-C
observations provide the first evidence of small-scale EUV heating
events at the base of these coronal loops, which have a free magnetic
energy of the order of 1026 erg.
Title: Properties of Solar Flare Clustering
Authors: Title, Alan; DeRosa, Marc
Bibcode: 2014cosp...40E3345T
Altcode:
The continuous full disk observations provided by the Atmospheric
Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO) give
an observer the impression that flare and filament eruptions are
related. However, both detailed analysis of a number of events as well
as a number of statistical studies have provided only rare examples of
clear causal behavior. But the mechanisms of flare triggering are not
well understood, so the lack of hard evidence is not surprising. Here
we have examined the waiting-time statistics of GOES X-ray flares of
magnitude C5 or greater during the last sunspot cycle with the aim of
assessing the degree to which flares are clustered in time. Clusters are
groups of flares in which all successive flares occur within a fixed
separation time - the linking window. While many of the flares in a
cluster may come from the same active region, the clusters that last
more than a disk passage must result from flares in multiple active
regions. The longest cluster of the last cycle lasted more than 42
days. None of the flares were separated by more than 36 hours. Since
that cluster lasted more than three disk passages, it could not have
been caused by a single region. We find that during the last maximum,
eight clusters contributed 44% of all flares. All of these clusters
spanned multiple disk passages, but occupied only 16.5% of the cycle
duration. Two of the clusters provided 34% of the flares. We suggest
that this behavior implies that a component of the observed coordinated
behavior has its origin in the solar dynamo.
Title: Large-scale Coronal Propagating Fronts in Solar Eruptions
as Observed by the Atmospheric Imaging Assembly on Board the Solar
Dynamics Observatory—an Ensemble Study
Authors: Nitta, Nariaki V.; Schrijver, Carolus J.; Title, Alan M.;
Liu, Wei
Bibcode: 2013ApJ...776...58N
Altcode: 2013arXiv1308.3544N
This paper presents a study of a large sample of global disturbances
in the solar corona with characteristic propagating fronts as
intensity enhancement, similar to the phenomena that have often
been referred to as Extreme Ultraviolet Imaging Telescope (EIT)
waves or extreme-ultraviolet (EUV) waves. Now EUV images obtained by
the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics
Observatory provide a significantly improved view of these large-scale
coronal propagating fronts (LCPFs). Between 2010 April and 2013 January,
a total of 171 LCPFs have been identified through visual inspection of
AIA images in the 193 Å channel. Here we focus on the 138 LCPFs that
are seen to propagate across the solar disk, first studying how they
are associated with flares, coronal mass ejections (CMEs), and type II
radio bursts. We measure the speed of the LCPF in various directions
until it is clearly altered by active regions or coronal holes. The
highest speed is extracted for each LCPF. It is often considerably
higher than EIT waves. We do not find a pattern where faster LCPFs
decelerate and slow LCPFs accelerate. Furthermore, the speeds are
not strongly correlated with the flare intensity or CME magnitude,
nor do they show an association with type II bursts. We do not find
a good correlation either between the speeds of LCPFs and CMEs in a
subset of 86 LCPFs observed by one or both of the Solar and Terrestrial
Relations Observatory spacecraft as limb events.
Title: Anti-parallel EUV Flows Observed along Active Region Filament
Threads with Hi-C
Authors: Alexander, Caroline E.; Walsh, Robert W.; Régnier, Stéphane;
Cirtain, Jonathan; Winebarger, Amy R.; Golub, Leon; Kobayashi,
Ken; Platt, Simon; Mitchell, Nick; Korreck, Kelly; DePontieu, Bart;
DeForest, Craig; Weber, Mark; Title, Alan; Kuzin, Sergey
Bibcode: 2013ApJ...775L..32A
Altcode: 2013arXiv1306.5194A
Plasma flows within prominences/filaments have been observed for
many years and hold valuable clues concerning the mass and energy
balance within these structures. Previous observations of these flows
primarily come from Hα and cool extreme-ultraviolet (EUV) lines (e.g.,
304 Å) where estimates of the size of the prominence threads has been
limited by the resolution of the available instrumentation. Evidence of
"counter-steaming" flows has previously been inferred from these cool
plasma observations, but now, for the first time, these flows have been
directly imaged along fundamental filament threads within the million
degree corona (at 193 Å). In this work, we present observations
of an AR filament observed with the High-resolution Coronal Imager
(Hi-C) that exhibits anti-parallel flows along adjacent filament
threads. Complementary data from the Solar Dynamics Observatory
(SDO)/Atmospheric Imaging Assembly (AIA) and Helioseismic and Magnetic
Imager are presented. The ultra-high spatial and temporal resolution
of Hi-C allow the anti-parallel flow velocities to be measured (70-80
km s-1) and gives an indication of the resolvable thickness
of the individual strands (0.''8 ± 0.''1). The temperature of the
plasma flows was estimated to be log T (K) = 5.45 ± 0.10 using Emission
Measure loci analysis. We find that SDO/AIA cannot clearly observe these
anti-parallel flows or measure their velocity or thread width due to
its larger pixel size. We suggest that anti-parallel/counter-streaming
flows are likely commonplace within all filaments and are currently
not observed in EUV due to current instrument spatial resolution.
Title: Pathways of Large-scale Magnetic Couplings between Solar
Coronal Events
Authors: Schrijver, Carolus J.; Title, Alan M.; Yeates, Anthony R.;
DeRosa, Marc L.
Bibcode: 2013ApJ...773...93S
Altcode: 2013arXiv1305.0801S
The high-cadence, comprehensive view of the solar corona by SDO/AIA
shows many events that are widely separated in space while occurring
close together in time. In some cases, sets of coronal events are
evidently causally related, while in many other instances indirect
evidence can be found. We present case studies to highlight a variety
of coupling processes involved in coronal events. We find that physical
linkages between events do occur, but concur with earlier studies that
these couplings appear to be crucial to understanding the initiation
of major eruptive or explosive phenomena relatively infrequently. We
note that the post-eruption reconfiguration timescale of the large-scale
corona, estimated from the extreme-ultraviolet afterglow, is on average
longer than the mean time between coronal mass ejections (CMEs), so
that many CMEs originate from a corona that is still adjusting from a
previous event. We argue that the coronal field is intrinsically global:
current systems build up over days to months, the relaxation after
eruptions continues over many hours, and evolving connections easily
span much of a hemisphere. This needs to be reflected in our modeling
of the connections from the solar surface into the heliosphere to
properly model the solar wind, its perturbations, and the generation and
propagation of solar energetic particles. However, the large-scale field
cannot be constructed reliably by currently available observational
resources. We assess the potential of high-quality observations from
beyond Earth's perspective and advanced global modeling to understand
the couplings between coronal events in the context of CMEs and solar
energetic particle events. .
Title: Detecting Nanoflare Heating Events in Subarcsecond Inter-moss
Loops Using Hi-C
Authors: Winebarger, Amy R.; Walsh, Robert W.; Moore, Ronald;
De Pontieu, Bart; Hansteen, Viggo; Cirtain, Jonathan; Golub, Leon;
Kobayashi, Ken; Korreck, Kelly; DeForest, Craig; Weber, Mark; Title,
Alan; Kuzin, Sergey
Bibcode: 2013ApJ...771...21W
Altcode:
The High-resolution Coronal Imager (Hi-C) flew aboard a NASA sounding
rocket on 2012 July 11 and captured roughly 345 s of high-spatial and
temporal resolution images of the solar corona in a narrowband 193 Å
channel. In this paper, we analyze a set of rapidly evolving loops that
appear in an inter-moss region. We select six loops that both appear in
and fade out of the Hi-C images during the short flight. From the Hi-C
data, we determine the size and lifetimes of the loops and characterize
whether these loops appear simultaneously along their length or
first appear at one footpoint before appearing at the other. Using
co-aligned, co-temporal data from multiple channels of the Atmospheric
Imaging Assembly on the Solar Dynamics Observatory, we determine the
temperature and density of the loops. We find the loops consist of
cool (~105 K), dense (~1010 cm-3)
plasma. Their required thermal energy and their observed evolution
suggest they result from impulsive heating similar in magnitude to
nanoflares. Comparisons with advanced numerical simulations indicate
that such dense, cold and short-lived loops are a natural consequence
of impulsive magnetic energy release by reconnection of braided magnetic
field at low heights in the solar atmosphere.
Title: Quasi-periodic Fast-mode Magnetosonic Wave Trains Inside and
Outside CME Bubbles Detected by SDO/AIA
Authors: Liu, Wei; Ofman, L.; Downs, C.; Title, A. M.
Bibcode: 2013SPD....44...50L
Altcode:
Quasi-periodic fast-mode magnetosonic wave trains both inside and
outside expanding CME bubbles have recently been discovered by
SDO/AIA (Liu et al. 2011, 2012; Shen & Liu 2012). In general,
a wave train inside a CME bubble originates from a flare site and
propagates along a funnel of coronal loops at typically 1000-2000 km/s
(Ofman et al. 2011). A wave train outside a CME usually originates
from a CME flank and propagates in the low corona along the solar
surface following the leading front of a global EUV wave at typically
500-1000 km/s. The former is primarily seen in the cooler 171 Angstrom
channel with a characteristic temperature of 0.8 MK, while the latter
is pronounced in the hotter 193 and 211 Angstrom channels of typically
1.6-2.0 MK. What is the relationship between the two types of wave
trains? Why do they appear differently in location and wavelength
(temperature)? To answer these questions, we report here for the
first time the evidence that the wave train beyond the CME bubble is
the continuation of the same wave train along the funnel within the
CME. The continuous deceleration of the waves is consistent with the
expected decrease of the local fast-mode speed with distance from the
active region (e.g., Ofman et al. 2011; Downs et al. 2012). There is
an abrupt change of the wave speed at the topological interface where
the expanding CME flank is located, indicative of contrasting magnetic
and plasma conditions, which can give rise to different (fast-mode)
speeds and wavelength (temperature) dependent appearances of these wave
trains.Abstract (2,250 Maximum Characters): Quasi-periodic fast-mode
magnetosonic wave trains both inside and outside expanding CME bubbles
have recently been discovered by SDO/AIA (Liu et al. 2011, 2012;
Shen & Liu 2012). In general, a wave train inside a CME bubble
originates from a flare site and propagates along a funnel of coronal
loops at typically 1000-2000 km/s (Ofman et al. 2011). A wave train
outside a CME usually originates from a CME flank and propagates in
the low corona along the solar surface following the leading front of a
global EUV wave at typically 500-1000 km/s. The former is primarily seen
in the cooler 171 Angstrom channel with a characteristic temperature
of 0.8 MK, while the latter is pronounced in the hotter 193 and 211
Angstrom channels of typically 1.6-2.0 MK. What is the relationship
between the two types of wave trains? Why do they appear differently
in location and wavelength (temperature)? To answer these questions,
we report here for the first time the evidence that the wave train
beyond the CME bubble is the continuation of the same wave train
along the funnel within the CME. The continuous deceleration of the
waves is consistent with the expected decrease of the local fast-mode
speed with distance from the active region (e.g., Ofman et al. 2011;
Downs et al. 2012). There is an abrupt change of the wave speed at
the topological interface where the expanding CME flank is located,
indicative of contrasting magnetic and plasma conditions, which can
give rise to different (fast-mode) speeds and wavelength (temperature)
dependent appearances of these wave trains.
Title: The Interface Region Imaging Spectrograph (IRIS)
Authors: De Pontieu, Bart; Title, A. M.; Lemen, J.; Wuelser, J.;
Tarbell, T. D.; Schrijver, C. J.; Golub, L.; Kankelborg, C.; Carlsson,
M.; Hansteen, V. H.; Worden, S.; IRIS Team
Bibcode: 2013SPD....44...03D
Altcode:
The solar chromosphere and transition region (TR) form a highly
structured and dynamic interface region between the photosphere and
the corona. This region not only acts as the conduit of all mass and
energy feeding into the corona and solar wind, it also requires an
order of magnitude more energy to heat than the corona. Nevertheless,
the chromosphere remains poorly understood, because of the complexity
of the required observational and analytical tools: the interface
region is highly complex with transitions from optically thick to
optically thin radiation, from pressure to magnetic field domination,
and large density and temperature contrasts on small spatial scales. The
Interface Region Imaging Spectrograph (IRIS) was selected for a NASA
SMEX mission in 2009 and is scheduled to launch on 26-June-2013 (with
first light scheduled for mid July). IRIS addresses critical questions:
(1) Which types of non-thermal energy dominate in the chromosphere and
beyond? (2) How does the chromosphere regulate mass and energy supply
to the corona and heliosphere? (3) How do magnetic flux and matter
rise through the lower atmosphere, and what role does flux emergence
play in flares and mass ejections? These questions are addressed with
a high-resolution near and far UV imaging spectrometer sensitive to
emission from plasma at temperatures between 5,000 K and 10 MK. IRIS
has a field-of-view of 120 arcsec, a spatial resolution of 0.4 arcsec,
and velocity resolution of 0.5 km/s. The IRIS investigation includes
a strong numerical modeling component based on advanced radiative MHD
codes to facilitate interpretation of observations. We describe the
IRIS instrumentation and numerical modeling, and present the plans for
observations, calibration and data distribution. We will highlight some
of the issues that IRIS observations can help resolve. More information
can be found at http://iris.lmsal.com
Title: SDO AIA Observations of Large-Scale Coronal Propagating Fronts
Authors: Nitta, Nariaki; Schrijver, C. J.; Title, A. M.; Liu, W.
Bibcode: 2013SPD....44...40N
Altcode:
The discovery of "EIT waves" rekindled interests in what used to be
called flare waves, which had been typically observed in H-alpha. In
addition to Moreton waves, first observed at the Lockheed Solar
Observatory, other manifestations of shock waves propagating in the
corona include type II radio bursts and filament oscillations away from
flare sites. Identification of EIT waves with the postulated fast-mode
MHD shock waves in the corona has been questioned, however, largely
because of their low speeds (e.g., 200-400 km/s). EIT's 10-20 minute
cadence could be a contributing factor for this, and we need to find how
fast large-scale coronal propagating fronts are in higher-cadence EUV
images. It is clear that AIA on SDO is the best instrument at the moment
for this type of work. With the availability of high-cadence full-disk
images, we now can compare propagating fronts in different directions,
and determine the highest speed of each event on AIA images more
objectively and accurately than on EIT (and STEREO EUVI) images. In a
large number of EIT wave events, we have measured speeds of propagating
fronts using AIA's 193 A images. Before the fronts are deflected by the
discontinuities, e.g., active regions and coronal holes, the mean and
median speeds are 620 km/s and 600 km/s, respectively, and many exceed
800 km/s. Higher speeds are often seen in events that accompany a type
II burst, strong flare or energetic CME, but the distribution of the
speed with these attributes is broad. We also find that the speeds of
the large-scale coronal propagating fronts are not well correlated
with those of the associated CMEs. Given that large-scale coronal
propagating fronts at large distances represent freely propagating MHD
waves, we discuss how to understand their nature close to their origins.
Title: Observing Coronal Nanoflares in Active Region Moss
Authors: Testa, Paola; De Pontieu, Bart; Martínez-Sykora, Juan;
DeLuca, Ed; Hansteen, Viggo; Cirtain, Jonathan; Winebarger, Amy;
Golub, Leon; Kobayashi, Ken; Korreck, Kelly; Kuzin, Sergey; Walsh,
Robert; DeForest, Craig; Title, Alan; Weber, Mark
Bibcode: 2013ApJ...770L...1T
Altcode: 2013arXiv1305.1687T
The High-resolution Coronal Imager (Hi-C) has provided Fe XII 193Å
images of the upper transition region moss at an unprecedented spatial
(~0.''3-0.''4) and temporal (5.5 s) resolution. The Hi-C observations
show in some moss regions variability on timescales down to ~15 s,
significantly shorter than the minute-scale variability typically found
in previous observations of moss, therefore challenging the conclusion
of moss being heated in a mostly steady manner. These rapid variability
moss regions are located at the footpoints of bright hot coronal
loops observed by the Solar Dynamics Observatory/Atmospheric Imaging
Assembly in the 94 Å channel, and by the Hinode/X-Ray Telescope. The
configuration of these loops is highly dynamic, and suggestive of
slipping reconnection. We interpret these events as signatures of
heating events associated with reconnection occurring in the overlying
hot coronal loops, i.e., coronal nanoflares. We estimate the order
of magnitude of the energy in these events to be of at least a few
1023 erg, also supporting the nanoflare scenario. These
Hi-C observations suggest that future observations at comparable
high spatial and temporal resolution, with more extensive temperature
coverage, are required to determine the exact characteristics of the
heating mechanism(s).
Title: The Hinode Spectro-Polarimeter
Authors: Lites, B. W.; Akin, D. L.; Card, G.; Cruz, T.; Duncan, D. W.;
Edwards, C. G.; Elmore, D. F.; Hoffmann, C.; Katsukawa, Y.; Katz, N.;
Kubo, M.; Ichimoto, K.; Shimizu, T.; Shine, R. A.; Streander, K. V.;
Suematsu, A.; Tarbell, T. D.; Title, A. M.; Tsuneta, S.
Bibcode: 2013SoPh..283..579L
Altcode:
The joint Japan/US/UK Hinode mission includes the first large-aperture
visible-light solar telescope flown in space. One component of the
Focal Plane Package of that telescope is a precision spectro-polarimeter
designed to measure full Stokes spectra with the intent of using those
spectra to infer the magnetic-field vector at high precision in the
solar photosphere. This article describes the characteristics of the
flight hardware of the HinodeSpectro-Polarimeter, and summarizes its
in-flight performance.
Title: Some Difficulties in Determining Causality of Sympathetic
Solar Events
Authors: DeRosa, M. L.; Schrijver, C. J.; Title, A. M.; Yeates, A. R.
Bibcode: 2013enss.confE..91D
Altcode:
Much has been made regarding the occurrence of synchronous eruptive
events occurring in the solar corona. Determining the frequencies at
which they occur and understanding the causal linkages that may connect
such events (making them sympathetic in addition to synchronous) are an
area of active research. Causal linkages are observed to take the form
of (1) disturbances in magnetic fields that connect active regions,
(2) disturbances in the magnetic field configuration overlying active
regions, and/or (3) triggering by disturbances propagating from one
region to another. Here we display two types of synchronous events:
those where, using a combination of image sequences from SDO and STEREO
as well as coronal-field modeling, evidence for sympathy seems solid,
and those where evidence of sympathy is more ambiguous. We use these two
types of cases to illustrate some difficulties in establishing whether
synchronous events are in fact sympathetic. This has implications
for determining the frequency and importance of sympathetic events,
and thus for understanding of coronal field evolution and the origins
of space weather.
Title: Recent Advances in Observations of Coronal EUV Waves
Authors: Liu, Wei; Ofman, Leon; Aschwanden, Markus J.; Nitta, Nariaki;
Zhao, Junwei; Title, Alan M.
Bibcode: 2013enss.confE..67L
Altcode:
MHD waves can be used as seismological tools to decipher otherwise
elusive physical parameters of the solar corona, such as the magnetic
field strength and plasma density. Recent high cadence, high resolution,
full-disk imaging observations from SDO/AIA have opened a new chapter
in understanding these waves. Various types of EUV waves associated with
flares/CMEs have been discovered or observed in unprecedented detail. In
this talk, we will review such new observations, focusing on the
following topics and their interrelationships: (1) quasi-periodic fast
waves traveling along coronal funnels within CME bubbles at speeds up
to 2000 km/s, associated with flare pulsations at similar frequencies;
(2) quasi-periodic wave trains within broad, diffuse pulses of global
EUV waves (so-called "EIT waves") running ahead of CME fronts; (3)
interactions of global EUV waves with local coronal structures on
their paths, such as flux-rope coronal cavities and their embedded
filaments (kink oscillations) and coronal holes or active regions
(deflections). We will discuss the implications of these observations
on coronal seismology, on their roles in transporting energy through
different parts of the solar atmosphere, and on understanding their
associated eruptive flares/CMEs.
Title: SDO AIA Observations of Large-Scale Coronal Disturbances in
the Form of Propagating Fronts
Authors: Nitta, Nariaki V.; Schrijver, Carolus J.; Title, Alan M.;
Liu, Wei
Bibcode: 2013enss.confE.111N
Altcode:
One of the most spectacular phenomena detected by SOHO EIT
was the large-scale propagating fronts associated with solar
eruptions. Initially these 'EIT' waves were thought to be coronal
counterparts of chromospheric Moreton waves. However, different
spatial and kinematic properties of the fronts seen in H-alpha and
EUV images, and far more frequent occurrences of the latter have
led to various interpretations that are still actively debated by
a number of researchers. A major factor for the lack of closure was
the various limitation in EIT data, including the cadence that was
typically every 12 minutes. Now we have significantly improved data
from SDO AIA, which have revealed some very interesting phenomena
associated with EIT waves. However, the studies so far conducted
using AIA data have primarily dealt with single or a small number of
events, where selection bias and particular observational conditions
may prevent us from discovering the general and true nature of EIT
waves. Although automated detection of EIT waves was promised for
AIA images some time ago, it is still not actually implemented in the
data pipeline. Therefore we have manually found nearly 200 examples
of large-scale propagating fronts, going through movies of difference
images from the AIA 193 A channel up to January 2013. We present our
study of the kinematic properties of the fronts in a subset of about
150 well-observed events in relation with other phenomena that can
accompany EIT waves. Our emphasis is on the relation of the fronts
with the associated coronal eruptions often but not always taking
the form of full-blown CMEs, utilizing STEREO data for a subset of
more than 80 events that have occurred near the limb as viewed from
one of the STEREO spacecraft. In these events, the availability of
data from the STEREO inner coronagraph (COR1) as well as from the EUVI
allows us to trace eruptions off the solar disk during the times of our
propagating fronts. The representative relations between the fronts and
CMEs will be discussed in terms of the evolution of EIT waves observed
in different channels of AIA, which provide information of the thermal
properties of the fronts. Our study will further clarify the variety
of solar eruptions and their associated manifestations in the corona.
Title: Collective Solar Behavior
Authors: Title, Alan; Schrijver, Karel; Derosa, MArc
Bibcode: 2013enss.confE.120T
Altcode:
The Atmospheric Imaging Assembly (AIA) on the Solar Dynamic Observatory
(SDO) together with the Helioseismic and Magnetic Imager (HMI) and the
Extreme Ultraviolet Variability Experiment (EVE) allow observations of
the entire Sun from 6000 K to 20,000,000 K with arcsecond resolution
and a 12 second cadence (AIA), obtain doppler and continuum images at
a 45 second cadence and Line of Sight and vector magnetograms (HMI)
every few minutes, and integrated solar spectra from 1 to 100 nm on a 2
second cadence (EVE) 24/7. Because of the enhanced thermal and temporal
coverage and the high dynamic range available with AIA, it has been
able to discovery associated behavior associated with extreme solar
events that are apparently driven by the rapid expansion of magnetic
structures. The extent of the events are recognized by using co-temporal
STEREO data. The rapidly expanding magnetic structures, speeds between
500 and 2000 km/s, can apparently trigger filament eruptions, CME's,
and other flares. These "triggered" events are sometimes larger that
the initial disturbance. The remote triggering makes flare prediction
based upon ONLY local energy build up models less valuable, but suggests
that with proper coverage prediction of solar events with potential
for Earth impact may be made more reliable. Movies of sample events
discovered in AIA together with STEREO data will be shown.
Title: The Coronal Mass Source for Post-Eruption Arcade Loops
Authors: Cheung, M. C. M.; Title, A. M.; Boerner, P.
Bibcode: 2013enss.confE.113C
Altcode:
Dark, sunward propagating features above post-eruption arcades have
long been studied using X-ray and EUV data since their first reported
discovery in the Yohkoh era. The data suggests that these so-called
supra-arcade downflows (SADs, sometimes referred to as tadpoles)
may be evacuated field lines retracting from the current sheet
beneath a coronal mass ejection. In this study, we focus on the bright
material in between tadpoles. AIA observations indicate that this high
emission-measure (EM) material is also propagating sunward. From this
empirical detection, we argue that a large fraction of retracting
field lines is loaded with mass. This plasma, which was initially
thrown up into the high coronal during the preceding CME launch, is
trapped in the reconnected magnetic field lines. As these field lines
retract toward a more force-free configuration, they pump the plasma
sunward and compress the plasma to high densities, temperatures (T >
10 MK) and EMs, leading to the fuzzy haze above the post-eruption arcade
loops. The fuzzy haze actually precedes the formation of distinct arcade
loops, which originate starting from the loop tops (which are near the
bottom of the haze) instead of the footpoints. We suggest this occurs
because the bottom of the haze is the region that has experienced
the most compression (due to pile-up up of retracting field lines)
and is thus an ideal location for catastrophic cooling to occur.
Title: Energy release in the solar corona from spatially resolved
magnetic braids
Authors: Cirtain, J. W.; Golub, L.; Winebarger, A. R.; de Pontieu,
B.; Kobayashi, K.; Moore, R. L.; Walsh, R. W.; Korreck, K. E.; Weber,
M.; McCauley, P.; Title, A.; Kuzin, S.; Deforest, C. E.
Bibcode: 2013Natur.493..501C
Altcode:
It is now apparent that there are at least two heating mechanisms
in the Sun's outer atmosphere, or corona. Wave heating may be the
prevalent mechanism in quiet solar periods and may contribute to
heating the corona to 1,500,000 K (refs 1, 2, 3). The active corona
needs additional heating to reach 2,000,000-4,000,000 K this heat
has been theoretically proposed to come from the reconnection and
unravelling of magnetic `braids'. Evidence favouring that process has
been inferred, but has not been generally accepted because observations
are sparse and, in general, the braided magnetic strands that are
thought to have an angular width of about 0.2 arc seconds have not been
resolved. Fine-scale braiding has been seen in the chromosphere but not,
until now, in the corona. Here we report observations, at a resolution
of 0.2 arc seconds, of magnetic braids in a coronal active region that
are reconnecting, relaxing and dissipating sufficient energy to heat
the structures to about 4,000,000 K. Although our 5-minute observations
cannot unambiguously identify the field reconnection and subsequent
relaxation as the dominant heating mechanism throughout active regions,
the energy available from the observed field relaxation in our example
is ample for the observed heating.
Title: The Interface Region Imaging Spectrograph (IRIS)
Authors: De Pontieu, B.; Title, A. M.; Lemen, J. R.; Wuelser, J.;
Tarbell, T. D.; Schrijver, C.; Golub, L.; Kankelborg, C. C.; Hansteen,
V. H.; Carlsson, M.
Bibcode: 2012AGUFMSH33D2256D
Altcode:
The solar chromosphere and transition region (TR) form a highly
structured and dynamic interface region between the photosphere and
the corona. This region not only acts as the conduit of all mass and
energy feeding into the corona and solar wind, it also requires an
order of magnitude more energy to heat than the corona. Nevertheless,
the chromosphere remains poorly understood, because of the complexity
of the required observational and analytical tools: the interface
region is highly complex with transitions from optically thick to
optically thin radiation, from pressure to magnetic field domination,
and large density and temperature contrasts on small spatial scales. The
Interface Region Imaging Spectrograph (IRIS) was selected for a NASA
SMEX mission in 2009 and is scheduled to launch in early 2013. IRIS
addresses critical questions: (1) Which types of non-thermal energy
dominate in the chromosphere and beyond? (2) How does the chromosphere
regulate mass and energy supply to the corona and heliosphere? (3)
How do magnetic flux and matter rise through the lower atmosphere, and
what role does flux emergence play in flares and mass ejections? These
questions are addressed with a high-resolution near and far UV imaging
spectrometer sensitive to emission from plasma at temperatures between
5,000 K and 10 MK. IRIS has a field-of-view of 120 arcsec, a spatial
resolution of 0.4 arcsec, and velocity resolution of 0.5 km/s. The
IRIS investigation includes a strong numerical modeling component
based on advanced radiative MHD codes to facilitate interpretation of
observations. We will describe the IRIS instrumentation and numerical
modeling, and present the status of the IRIS observatory development. We
will highlight some of the issues that IRIS observations can help
resolve.
Title: It's not raining frogs. It's raining tadpoles!
Authors: Cheung, M.; Title, A. M.
Bibcode: 2012AGUFMSH51A2195C
Altcode:
Dark, downflowing structures with tadpole-like morphologies were
discovered in TRACE EUV observations of supra-arcades of active region
eruptions. Recent EUV observations of large active region eruptions by
SDO/AIA reveal that broods of coronal condensations in post-eruption
arcades preferentially originate near the tops of arcade loops. The
time lag between the appearance of tadpoles and the appearance of dense
condensations in post-eruption arcade loops suggests a possible casual
relation. We will discuss possible explanations for this tentative
connection. One possible explanation is that tadpoles serve as sources
of mass for coronal condensations.
Title: The impact of geomagnetic storms on the US electric power grid
Authors: Schrijver, C.; Mitchell, S.; Title, A. M.
Bibcode: 2012AGUFMSM23B2303S
Altcode:
Large solar explosions are responsible for space weather that can
impact technological infrastructure on and around Earth. We study
the impacts of geomagnetic activity on the U.S. electric power
grid for the period from 1992 through 2010. We find, with more than
3-sigma significance, that approximately 4% of the disturbances in
the U.S. power grid reported to the U.S. Department of Energy are
attributable to geomagnetic activity. The combination of our results
with an economic assessment study by the electric power industry
suggests that the average cost to the U.S. economy of non-catastrophic
grid disturbances in which space weather conditions are a contributing
factor exceeds $3 billion per year. The magnitude of this apparent
economic impact warrants extensive follow-up studies to validate,
understand, and mitigate against the weak but significant contribution
of space weather in power grid disturbances.
Title: Loop Evolution Observed with AIA and Hi-C
Authors: Mulu-Moore, F.; Winebarger, A. R.; Cirtain, J. W.; Kobayashi,
K.; Korreck, K. E.; Golub, L.; Kuzin, S.; Walsh, R. W.; DeForest,
C.; De Pontieu, B.; Title, A. M.; Weber, M.
Bibcode: 2012AGUFMSH33A2225M
Altcode:
In the past decade, the evolution of EUV loops has been used to infer
the loop substructure. With the recent launch of High Resolution Coronal
Imager (Hi-C), this inference can be validated. In this presentation we
discuss the first results of loop analysis comparing AIA and Hi-C data.
Title: The Fundamental Structure of Coronal Loops
Authors: Winebarger, A. R.; Warren, H. P.; Cirtain, J. W.; Kobayashi,
K.; Korreck, K. E.; Golub, L.; Kuzin, S.; Walsh, R. W.; DeForest,
C.; De Pontieu, B.; Title, A. M.; Weber, M.
Bibcode: 2012AGUFMSH31B..06W
Altcode:
During the past ten years, solar physicists have attempted to infer the
coronal heating mechanism by comparing observations of coronal loops
with hydrodynamic model predictions. These comparisons often used
the addition of sub-resolution strands to explain the observed loop
properties. On July 11, 2012, the High Resolution Coronal Imager (Hi-C)
was launched on a sounding rocket. This instrument obtained images of
the solar corona was 0.2-0.3'' resolution in a narrowband EUV filter
centered around 193 Angstroms. In this talk, we will compare these
high resolution images to simultaneous density measurements obtained
with the Extreme Ultraviolet Imaging Spectrograph (EIS) on Hinode to
determine whether the structures observed with Hi-C are resolved.
Title: Design, performance prediction, and measurements of the
interface region imaging spectrograph (IRIS) telescope
Authors: Podgorski, William A.; Cheimets, Peter N.; Golub, Leon;
Lemen, James R.; Title, Alan M.
Bibcode: 2012SPIE.8443E..3DP
Altcode:
This paper discusses the design of the IRIS Small Explorer
(SMEX) Cassegrain telescope, as well as its intended and measured
performance. Lockheed Martin, along with SAO, Montana State University,
and Stanford University are developing the IRIS instrument for a mission
to examine the solar spectra in two bands, one centered on 1369 Å,
and the other centered on 2810 Å. SAO led the design and construction
of the telescope feed, with assistance from Lockheed and Montana State
University. The telescope posed a number of implementation challenges,
which are discussed here, including the fact that no effective filters
exist to isolate the science spectra to the exclusion of the rest
of the solar flux, making it necessary to allow full sunlight into
the telescope.
Title: The interface region imaging spectrograph for the IRIS Small
Explorer mission
Authors: Wülser, Jean-Pierre; Title, Alan M.; Lemen, James R.; De
Pontieu, Bart; Kankelborg, Charles C.; Tarbell, Theodore D.; Berger,
Thomas E.; Golub, Leon; Kushner, Gary D.; Chou, Catherine Y.; Weingrod,
Isaac; Holmes, Buck; Mudge, Jason; Podgorski, William A.
Bibcode: 2012SPIE.8443E..08W
Altcode:
The Interface Region Imaging Spectrograph (IRIS) is a NASA SMall
EXplorer mission scheduled for launch in January 2013. The primary goal
of IRIS is to understand how the solar atmosphere is energized. The
IRIS investigation combines advanced numerical modeling with a high
resolution UV imaging spectrograph. IRIS will obtain UV spectra
and images with high resolution in space (0.4 arcsec) and time (1s)
focused on the chromosphere and transition region of the Sun, a complex
interface region between the photosphere and corona. The IRIS instrument
uses a Cassegrain telescope to feed a dual spectrograph and slit-jaw
imager that operate in the 133-141 nm and 278-283 nm ranges. This paper
describes the instrument with emphasis on the imaging spectrograph,
and presents an initial performance assessment from ground test results.
Title: Plasma Instabilities in Quiescent Prominences
Authors: Ryutova, M.; Berger, T.; Frank, Z.; Title, A.; Tarbell, T.
Bibcode: 2012ASPC..454..143R
Altcode:
We study dynamics of quiescent prominences using several data sets
taken with the SOT on Hinode. We find a number of processes occurring
at different stages of the prominence evolution that are common for
all the chosen cases, and having universal character, can be related
to a fundamental plasma instabilities. We combine the observational
evidence and theory to identify these instabilities. Here we discuss
only two examples: (1) Coronal cavity formation under a prominence
body and its evolution associated with screw pinch instability, and
(2) Development of a regular series of plumes and spikes typical to
the Rayleigh-Taylor instability modified by solenoidal magnetic field.
Title: Quasi-periodic Fast-mode Wave Trains within a Global EUV Wave
and Sequential Transverse Oscillations Detected by SDO/AIA
Authors: Liu, Wei; Ofman, Leon; Nitta, Nariaki V.; Aschwanden, Markus
J.; Schrijver, Carolus J.; Title, Alan M.; Tarbell, Theodore D.
Bibcode: 2012ApJ...753...52L
Altcode: 2012arXiv1204.5470L
We present the first unambiguous detection of quasi-periodic wave
trains within the broad pulse of a global EUV wave (so-called EIT wave)
occurring on the limb. These wave trains, running ahead of the lateral
coronal mass ejection (CME) front of 2-4 times slower, coherently
travel to distances >~ R ⊙/2 along the solar surface,
with initial velocities up to 1400 km s-1 decelerating to
~650 km s-1. The rapid expansion of the CME initiated at
an elevated height of 110 Mm produces a strong downward and lateral
compression, which may play an important role in driving the primary
EUV wave and shaping its front forwardly inclined toward the solar
surface. The wave trains have a dominant 2 minute periodicity that
matches the X-ray flare pulsations, suggesting a causal connection. The
arrival of the leading EUV wave front at increasing distances produces
an uninterrupted chain sequence of deflections and/or transverse (likely
fast kink mode) oscillations of local structures, including a flux-rope
coronal cavity and its embedded filament with delayed onsets consistent
with the wave travel time at an elevated (by ~50%) velocity within
it. This suggests that the EUV wave penetrates through a topological
separatrix surface into the cavity, unexpected from CME-caused magnetic
reconfiguration. These observations, when taken together, provide
compelling evidence of the fast-mode MHD wave nature of the primary
(outer) fast component of a global EUV wave, running ahead of the
secondary (inner) slow component of CME-caused restructuring.
Title: CMEs as observed in SDO - comparisons with White Light
observations
Authors: Title, Alan
Bibcode: 2012cosp...39.1978T
Altcode: 2012cosp.meet.1978T
The Atmospheric Imaging Assembly (AIA) is an ideal instrument to observe
the initial phases of Corona Mass Ejections (CME) because is has a 12
second time cycle time during which it takes images in 8 spectral bands
each of which has 41 arc second field of view. The 8 images,coaligned
to a few tenths of a pixel, span a temperature range from 6000 to
20,000,000 K. The 4096 x4096 CCD detectors have a dynamic range of
10,000. These observations can be directly correlated with the white
light coronal images produced by LASCO on SOHO and on the STEREO A and B
spacecraft. STEREO also produces EUV images, although not at as high a
cadence as AIA, that can be used to do some basic triangulation of the
initial phases of the CME process. The Heliospheric images on STEREO
can follow ejecta to the Earth and beyond. The spatial and temporal
details provided by the set of systems in space are a challenge to
modelers. Modern numerical simulations are not capturing some of the
essential feature of CME initiation and evolution. Movies will be
shown of some of the correlated events in the CME process.
Title: Large-Scale Coronal Disturbances as Observed by SDO AIA
Authors: Nitta, Nariaki; Schrijver, Carolus; Title, Alan; Lemen,
James; Liu, Wei
Bibcode: 2012cosp...39.1378N
Altcode: 2012cosp.meet.1378N
With increasing solar activity, the Atmospheric Imaging Assembly
(AIA) on the Solar Dynamics Observatory (SDO) has observed a number
of large-scale coronal disturbances, which may correspond to what we
have generally known as "EIT waves." Although their nature is still
actively debated, these disturbances usually accompany CMEs. In certain
cases, the fronts of the disturbances may signify CME-related shock
waves important for particle acceleration. Using the unprecedented
temporal resolution and broad temperature coverage of the AIA, we have
studied more than 100 such events. Here we discuss their kinematics
characterized by faster fronts than EIT waves in Solar Cycle 23, and
spatial relations with CMEs using STEREO data that provide triangulation
of the fronts. We also try plasma diagnostic using images in different
filters. Association of these disturbances with CMEs, flares and type
II bursts is discussed on a statistical basis. Lastly, we explore the
possible relation of the larger-scale coronal disturbances with SEP
events observed at widely separate longitudes and their onset times.
Title: Magnetic flux emergence from the convective zone into the
solar atmosphere
Authors: Title, Alan
Bibcode: 2012cosp...39.1979T
Altcode: 2012cosp.meet.1979T
The flight of the Solar Dynamics Observatory (SDO) with its three
instruments the Atmospheric Imaging Assembly (AIA), the Helioseismic
and Magnetic Imager (HMI), and the Extreme ultraviolet Variability
Experiment (EVE) has started a revolution in our understanding the
role of flux emergence on the heating and stability of the solar
atmosphere. Because the imaging instruments, AIA and HM, operate 24/7
and take data at high temporal cadence and high spatial resolution
over the entire Sun, there now exists a data set that can track the
magnetic field from the solar convection zone to its appearance on the
solar surface and then follow the consequences of the emergence on the
outer atmosphere. EVE provides a major contribution with a second by
second recording of the solar irradiance in the EUV with high spectral
resolution. The complete data allows determination of the rate that the
atmosphere is heating and cooling in different temperature domains.. The
breath and completeness of the data sets that these three instruments
produce provides modelers exciting new challenges. Supercomputers
are now beginning to produce increasingly convincing simulations of
both flux emergence and the associated heating processes in the outer
atmosphere. Movies of many of the effects of emerging solar fields
with be presented.
Title: First Results from the SUNRISE Mission
Authors: Solanki, S. K.; Barthol, P.; Danilovic, S.; Feller, A.;
Gandorfer, A.; Hirzberger, J.; Jafarzadeh, S.; Lagg, A.; Riethmüller,
T. L.; Schüssler, M.; Wiegelmann, T.; Bonet, J. A.; González,
M. J. M.; Pillet, V. M.; Khomenko, E.; Yelles Chaouche, L.; Iniesta,
J. C. d. T.; Domingo, V.; Palacios, J.; Knölker, M.; González,
N. B.; Borrero, J. M.; Berkefeld, T.; Franz, M.; Roth, M.; Schmidt,
W.; Steiner, O.; Title, A. M.
Bibcode: 2012ASPC..455..143S
Altcode:
The SUNRISE balloon-borne solar observatory consists of a 1m aperture
Gregory telescope, a UV filter imager, an imaging vector polarimeter,
an image stabilization system, and further infrastructure. The first
science flight of SUNRISE yielded high-quality data that reveal the
structure, dynamics, and evolution of solar convection, oscillations,
and magnetic fields at a resolution of around 100 km in the quiet
Sun. Here we describe very briefly the mission and the first results
obtained from the SUNRISE data, which include a number of discoveries.
Title: SDO/AIA Detection of Quasi-periodic Wave Trains Within Global
EUV ("EIT") Waves and Their Coronal Seismology Implications
Authors: Liu, Wei; Ofman, L.; Aschwanden, M. J.; Nitta, N.; Schrijver,
C. J.; Title, A. M.; Tarbell, T. D.
Bibcode: 2012AAS...22051501L
Altcode:
The nature of global EUV waves (so-called "EIT waves") has long
been under debate because of instrumental limitations and projection
effects when viewed on the solar disk. We present here high cadence
SDO/AIA observations of global EUV waves occurring on the limb. We
report newly discovered quasi-periodic wave trains located in the low
corona within a broad, diffuse pulse of the global EUV wave ahead of
the lateral CME front/flank. These waves coherently travel to large
distances on the order of 1 solar radii with initial velocities up
to 1400 km/s. They have dominant 1-3 minute periodicities that often
match the X-ray pulsations of the accompanying flare, suggestive of
a causal connection. In addition, recently discovered quasi-periodic
fast propagating (QFP) waves of 1000-2000 km/s (Liu, Title, Zhao et
al. 2011 ApJL) are found in the funnel of coronal loops rooted at the
flare kernel. These waves are spatially confined within the CME bubble
and rapidly disappear while approaching the CME front, suggestive
of strong damping and/or dispersion. These observations provide new
evidence of the fast-mode wave nature of the primary, fast component
of a global EUV wave, running ahead of a secondary, slow component
of CME-caused restructuring of the coronal magnetic field. We suggest
that the two types of quasi-periodic waves are both integral parts of
global coronal dynamics manifested as a CME/flare eruption, and they
have important implications for global and local coronal seismology.
Title: CME’s - The Early Stages
Authors: Title, Alan M.
Bibcode: 2012AAS...22030901T
Altcode:
The Atmospheric Imaging Assembly on the Solar Dynamics Observatory
provides 24/7 full Sun coverage with a 12 second cadence with images
that span the temperature range from 6000 to 20,000,000 with arc second
resolution. With this data set and observations with the pair of STEREO
satellites and images from LASCO on SOHO it has become possible to
identify the earliest stages of a CME and to obtain at least a rough
idea of the CME’s shape. Numerous example of events will be shown.
Title: Large-scale Coronal Disturbances As Observed By SDO AIA
Authors: Nitta, Nariaki; Schrijver, C.; title, A.; Liu, W.; Lemen, J.
Bibcode: 2012AAS...22051502N
Altcode:
With increasing solar activity, the Atmospheric Imaging Assembly
(AIA) on the Solar Dynamics Observatory (SDO) has observed a number
of large-scale coronal disturbances, which may correspond to what
we have generally known as "EIT waves." Their nature is still
actively debated. In certain cases, the fronts of the disturbances
may signify CME-related shock waves that are important for particle
acceleration. Using the unprecedented temporal resolution and broad
temperature coverage of the AIA, we have studied more than 100 such
events. Here we discuss their kinematics characterized by faster fronts
than EIT waves in Solar Cycle 23, and spatial relations with CMEs
using STEREO data that provide triangulation of the fronts. We also
try plasma diagnostic using images in different filters. Association
of these disturbances with other phenomena such as CMEs, flares and
type II bursts, is discussed on a statistical basis.
Title: A First Look at Magnetic Field Data Products from SDO/HMI
Authors: Liu, Y.; Scherrer, P. H.; Hoeksema, J. T.; Schou, J.; Bai,
T.; Beck, J. G.; Bobra, M.; Bogart, R. S.; Bush, R. I.; Couvidat,
S.; Hayashi, K.; Kosovichev, A. G.; Larson, T. P.; Rabello-Soares,
C.; Sun, X.; Wachter, R.; Zhao, J.; Zhao, X. P.; Duvall, T. L., Jr.;
DeRosa, M. L.; Schrijver, C. J.; Title, A. M.; Centeno, R.; Tomczyk,
S.; Borrero, J. M.; Norton, A. A.; Barnes, G.; Crouch, A. D.; Leka,
K. D.; Abbett, W. P.; Fisher, G. H.; Welsch, B. T.; Muglach, K.;
Schuck, P. W.; Wiegelmann, T.; Turmon, M.; Linker, J. A.; Mikić,
Z.; Riley, P.; Wu, S. T.
Bibcode: 2012ASPC..455..337L
Altcode:
The Helioseismic and Magnetic Imager (HMI; Scherrer & Schou 2011)
is one of the three instruments aboard the Solar Dynamics Observatory
(SDO) that was launched on February 11, 2010 from Cape Canaveral,
Florida. The instrument began to acquire science data on March 24. The
regular operations started on May 1. HMI measures the Doppler velocity
and line-of-sight magnetic field in the photosphere at a cadence of
45 seconds, and the vector magnetic field at a 135-second cadence,
with a 4096× 4096 pixels full disk coverage. The vector magnetic
field data is usually averaged over 720 seconds to suppress the p-modes
and increase the signal-to-noise ratio. The spatial sampling is about
0".5 per pixel. HMI observes the Fe i 6173 Å absorption line, which
has a Landé factor of 2.5. These data are further used to produce
higher level data products through the pipeline at the HMI-AIA Joint
Science Operations Center (JSOC) - Science Data Processing (Scherrer et
al. 2011) at Stanford University. In this paper, we briefly describe the
data products, and demonstrate the performance of the HMI instrument. We
conclude that the HMI is working extremely well.
Title: Connected Solar Events
Authors: Title, A.
Bibcode: 2012EGUGA..14.6812T
Altcode:
The Atmospheric Imaging Assembly on the Solar Dynamics Observatory
(SDO) provides 24/7 full Sun coverage with a 12 second cadence with
images that span the temperature range from 6000 to 20,000,000K with
arc second resolution. The Heliospheric and Magnetic Imager on SDO
provides doppler data every 30 seconds, line-of-sight magnetograms
every 45 seconds, and vector magnetograms every 5 minutes. With this
data set and observations from the pair of STEREO satellites it has
become apparent that many flares, filament eruptions, and CME's have
causal connections. These connections often span a hemisphere. Numerical
simulations have indicated at least one mechanism of how the triggering
of remote events occurs. Maps of the magnetic topology implied by the
surface field often indicates both the regions that are connected and
the boundaries of the connected zones. Movies of everts and numerical
simulations will be presented as well as topological mappings that
indicate the zones of connectivity.
Title: Diffusivity of Isolated Internetwork Ca II H Bright Points
Observed by SuFI/SUNRISE
Authors: Jafarzadeh, S.; Solanki, S. K.; Cameron, R. H.; Feller, A.;
Pietarila, A.; Lagg, A.; Barthol, P.; Berkefeld, T.; Gandorfer, A.;
Knoelker, M.; Martinez Pillet, V.; Schmidt, W.; Title, A.
Bibcode: 2012decs.confE..99J
Altcode:
We analyze trajectories of the proper motion of intrinsically magnetic,
isolated internetwork Ca II H BPs (with mean lifetime of 461 sec) to
obtain their diffusivity behaviors. We use high spatial and temporal
resolution image sequences of quiet-Sun, disc-centre observations
obtained in the Ca II H 397 nm passband of the Sunrise Filter Imager
(SuFI) on board the SUNRISE balloon-borne solar observatory. In
order to avoid misidentification, the BPs are semi-manually selected
and then automatically tracked. The trajectory of each BP is then
calculated and its diffusion index is described by a power law
exponent, using which we classify the BPs' trajectories into sub-,
normal and super- diffusive. In addition, the corresponding diffusion
coefficients (D) based on the observed displacements are consequently
computed. We find a strong super-diffusivity at a height sampled by the
SuFI/SUNRISE Ca II H passband (i.e. a height corresponding roughly to
the temperature minimum). We find that 74% of the identified tiny BPs
are super-diffusive, 18% move randomly (i.e. their motion corresponds
to normal diffusion) and only 8% belong to the sub-diffusion regime. In
addition, we find that 53% of the super-diffusion regime (i.e. 39% of
all BPs) have the diffusivity index of 2 which are termed as "Ballistic
BPs". Finally, we explore the distribution of diffusion index with the
help of a simple simulation. The results suggest that the BPs are random
walkers superposed by a systematic (background) velocity in which the
magnitude of each component (and hence their ratio) depends on the time
and spatial scales. We further discuss a simple sketch to explain the
diffusivity of observed BPs while they migrate within a supergranule
(i.e. internetwork areas) or close to the network regions.
Title: Observation, inversion and numerical simulation of single-lobed
Stokes V profiles in the quiet sun.
Authors: Sainz Dalda, A.; Martínez-Sykora, J.; Bellot Rubio, L.;
Title, A.
Bibcode: 2012decs.confE..89S
Altcode:
We have studied characteristics and statistics of strong asymmetric
profiles in Stokes V, i.e., single-lobed profiles, in quiet sun using
Hinode/SOT. These profiles require the existence of a velocity gradient
along the line-of-sight, possibly associated with gradients of magnetic
field strength, inclination and/or azimuth. For a better understanding,
observations, inversions and numerical simulations are compared. We
focus our analysis of the observations on the statistical properties
of the single-lobed Stokes V profiles and the results provided by the
inversions using SIRJUMP, which is an LTE inversion code that can
reproduce sharp discontinuities or jump in the magnetic field and
line-of-sight velocity of the atmosphere model. In the quiet sun,
magnetic field is continuously appearing and disappearing at small
scales due to the convective motions and the input of new flux from
deeper layers. From radiative MHD 3D simulations, using Bifrost code, we
note that most of these small scale processes have stratifications with
gradients of magnetic field strength, inclination and velocities. As
result, those stratifications showing jumps in the magnetic field
configuration are associated with the existence of single-lobe Stokes
V profiles in the solar photosphere, as we previously assumed for the
inversions. We show that most of these profiles come from emerging and
disappearance magnetic flux in small scales in the simulations. Finally,
we emphasize importance of the comparison between the synthetic profiles
from the simulations with the observed ones and the atmospheres that
produce them. This comparison will ultimately improve the realism of
the simulations and quantify the emerging and disappearance flux in
the quiet sun.
Title: Study of Single-lobed Circular Polarization Profiles in the
Quiet Sun
Authors: Sainz Dalda, A.; Martínez-Sykora, J.; Bellot Rubio, L.;
Title, A.
Bibcode: 2012ApJ...748...38S
Altcode: 2012arXiv1202.0593S
The existence of asymmetries in the circular polarization (Stokes V)
profiles emerging from the solar photosphere has been known since
the 1970s. These profiles require the presence of a velocity gradient
along the line of sight (LOS), possibly associated with gradients of
magnetic field strength, inclination, and/or azimuth. We have focused
our study on the Stokes V profiles showing extreme asymmetry in the
form of only one lobe. Using Hinode spectropolarimetric measurements,
we have performed a statistical study of the properties of these
profiles in the quiet Sun. We show their spatial distribution, their
main physical properties, how they are related with several physical
observables, and their behavior with respect to their position on
the solar disk. The single-lobed Stokes V profiles occupy roughly
2% of the solar surface. For the first time, we have observed their
temporal evolution and have retrieved the physical conditions of the
atmospheres from which they emerged using an inversion code implementing
discontinuities of the atmospheric parameters along the LOS. In
addition, we use synthetic Stokes profiles from three-dimensional
magnetoconvection simulations to complement the results of the
inversion. The main features of the synthetic single-lobed profiles
are in general agreement with the observed ones, lending support to
the magnetic and dynamic topologies inferred from the inversion. The
combination of all these different analyses suggests that most of the
single-lobed Stokes V profiles are signals coming from the magnetic
flux emergence and/or submergence processes taking place in small
patches in the photosphere of the quiet Sun.
Title: On the importance of Global Events in Destabilizations of
the Solar Atmosphere
Authors: Title, Alan
Bibcode: 2012decs.confE.123T
Altcode:
A large segment of solar research has focused on structures that give
rise to violent events- flares and coronal mass ejections (CME's). This
has placed emphasis on the development of active regions and filament
channels with foci on energy build up and triggering. At the same
time there have existed controversies about sympathetic flares,
stealth CME's, and whether there can be CME's without flares. The
operation of the Solar Dynamic Observatory, which collects full Sun
line-of-sight and vector magnetograms field maps as well as full-Sun
images in a range of wavelengths in the UV and EUV on a 12 second
cadence 24/7, is now demonstrating that many violent solar events
are connected. Recent simulations have suggested how the remote
destabilizations occur. Maps of the Sun's magnetic topology show
both the paths and the bounds of some of the instabilities. It
is clear that we are in early stages of understanding of some of
probably many mechanisms for destabilization. It is also clear that
an understanding of the consequences of magnetic topologies are now,
and will in the future be, a rich research topic. Movies of solar
events and corresponding simulations will be shown.
Title: SDO/AIA Observations of Various Coronal EUV Waves Associated
with Flares/CMEs and Their Coronal Seismology Implications
Authors: Liu, Wei; Ofman, Leon; Aschwanden, Markus J.; Nitta, Nariaki;
Zhao, Junwei; Title, Alan M.
Bibcode: 2012decs.confE..87L
Altcode:
MHD waves can be used as diagnostic tools of coronal seismology to
decipher otherwise elusive critical physical parameters of the solar
corona, such as the magnetic field strength and plasma density. They
are analogous to acoustic waves used in helioseismology, but with
complexities arising from the magnetic field and nonlinearity. Recent
high cadence, high resolution, full-disk imaging observations from
SDO/AIA have opened a new chapter in understanding these waves. Various
types of EUV waves associated with flares/CMEs have been discovered
or observed in unprecedented detail. In this presentation, we will
review such new AIA observations, focusing on the following topics and
their interrelationships: (1) quasi-periodic fast waves traveling along
coronal funnels within CME bubbles at speeds up to 2000 km/s, associated
with flare pulsations at similar frequencies; (2) quasi-periodic wave
trains within broad, diffuse pulses of global EUV waves (so-called
EIT waves) running ahead of CME fronts; (3) interactions of global EUV
waves with local coronal structures on their paths, such as flux-rope
coronal cavities and their embedded filaments (kink oscillations)
and coronal holes/active regions (deflections). We will discuss the
implications of these observations on coronal seismology, on their roles
in transporting energy through different parts of the solar atmosphere,
and on understanding their associated eruptive flares/CMEs.
Title: The Atmospheric Imaging Assembly (AIA) on the Solar Dynamics
Observatory (SDO)
Authors: Lemen, James R.; Title, Alan M.; Akin, David J.; Boerner,
Paul F.; Chou, Catherine; Drake, Jerry F.; Duncan, Dexter W.; Edwards,
Christopher G.; Friedlaender, Frank M.; Heyman, Gary F.; Hurlburt, Neal
E.; Katz, Noah L.; Kushner, Gary D.; Levay, Michael; Lindgren, Russell
W.; Mathur, Dnyanesh P.; McFeaters, Edward L.; Mitchell, Sarah; Rehse,
Roger A.; Schrijver, Carolus J.; Springer, Larry A.; Stern, Robert A.;
Tarbell, Theodore D.; Wuelser, Jean-Pierre; Wolfson, C. Jacob; Yanari,
Carl; Bookbinder, Jay A.; Cheimets, Peter N.; Caldwell, David; Deluca,
Edward E.; Gates, Richard; Golub, Leon; Park, Sang; Podgorski, William
A.; Bush, Rock I.; Scherrer, Philip H.; Gummin, Mark A.; Smith, Peter;
Auker, Gary; Jerram, Paul; Pool, Peter; Soufli, Regina; Windt, David
L.; Beardsley, Sarah; Clapp, Matthew; Lang, James; Waltham, Nicholas
Bibcode: 2012SoPh..275...17L
Altcode: 2011SoPh..tmp..106L; 2011SoPh..tmp..172L; 2011SoPh..tmp..241L;
2011SoPh..tmp..115L
The Atmospheric Imaging Assembly (AIA) provides multiple simultaneous
high-resolution full-disk images of the corona and transition region
up to 0.5 R⊙ above the solar limb with 1.5-arcsec spatial
resolution and 12-second temporal resolution. The AIA consists of four
telescopes that employ normal-incidence, multilayer-coated optics to
provide narrow-band imaging of seven extreme ultraviolet (EUV) band
passes centered on specific lines: Fe XVIII (94 Å), Fe XVII, XXI
(131 Å), Fe IX (171 Å), Fe XII, XXIV (193 Å), Fe XIV (211 Å),
He II (304 Å), and Fe XVI (335 Å). One telescope observes C IV
(near 1600 Å) and the nearby continuum (1700 Å) and has a filter
that observes in the visible to enable coalignment with images from
other telescopes. The temperature diagnostics of the EUV emissions
cover the range from 6×104 K to 2×107 K. The
AIA was launched as a part of NASA's Solar Dynamics Observatory (SDO)
mission on 11 February 2010. AIA will advance our understanding of the
mechanisms of solar variability and of how the Sun's energy is stored
and released into the heliosphere and geospace.
Title: Initial Calibration of the Atmospheric Imaging Assembly (AIA)
on the Solar Dynamics Observatory (SDO)
Authors: Boerner, Paul; Edwards, Christopher; Lemen, James; Rausch,
Adam; Schrijver, Carolus; Shine, Richard; Shing, Lawrence; Stern,
Robert; Tarbell, Theodore; Title, Alan; Wolfson, C. Jacob; Soufli,
Regina; Spiller, Eberhard; Gullikson, Eric; McKenzie, David; Windt,
David; Golub, Leon; Podgorski, William; Testa, Paola; Weber, Mark
Bibcode: 2012SoPh..275...41B
Altcode:
The Atmospheric Imaging Assembly (AIA) instrument onboard the Solar
Dynamics Observatory (SDO) is an array of four normal-incidence
reflecting telescopes that image the Sun in ten EUV and UV wavelength
channels. We present the initial photometric calibration of AIA,
based on preflight measurements of the response of the telescope
components. The estimated accuracy is of order 25%, which is consistent
with the results of comparisons with full-disk irradiance measurements
and spectral models. We also describe the characterization of the
instrument performance, including image resolution, alignment,
camera-system gain, flat-fielding, and data compression.
Title: Design and Ground Calibration of the Helioseismic and Magnetic
Imager (HMI) Instrument on the Solar Dynamics Observatory (SDO)
Authors: Schou, J.; Scherrer, P. H.; Bush, R. I.; Wachter, R.;
Couvidat, S.; Rabello-Soares, M. C.; Bogart, R. S.; Hoeksema, J. T.;
Liu, Y.; Duvall, T. L.; Akin, D. J.; Allard, B. A.; Miles, J. W.;
Rairden, R.; Shine, R. A.; Tarbell, T. D.; Title, A. M.; Wolfson,
C. J.; Elmore, D. F.; Norton, A. A.; Tomczyk, S.
Bibcode: 2012SoPh..275..229S
Altcode:
The Helioseismic and Magnetic Imager (HMI) investigation (Solar
Phys. doi:10.1007/s11207-011-9834-2, 2011) will study the solar
interior using helioseismic techniques as well as the magnetic field
near the solar surface. The HMI instrument is part of the Solar
Dynamics Observatory (SDO) that was launched on 11 February 2010. The
instrument is designed to measure the Doppler shift, intensity, and
vector magnetic field at the solar photosphere using the 6173 Å Fe I
absorption line. The instrument consists of a front-window filter, a
telescope, a set of waveplates for polarimetry, an image-stabilization
system, a blocking filter, a five-stage Lyot filter with one tunable
element, two wide-field tunable Michelson interferometers, a pair
of 40962 pixel cameras with independent shutters, and
associated electronics. Each camera takes a full-disk image roughly
every 3.75 seconds giving an overall cadence of 45 seconds for the
Doppler, intensity, and line-of-sight magnetic-field measurements
and a slower cadence for the full vector magnetic field. This article
describes the design of the HMI instrument and provides an overview of
the pre-launch calibration efforts. Overviews of the investigation,
details of the calibrations, data handling, and the science analysis
are provided in accompanying articles.
Title: The Helioseismic and Magnetic Imager (HMI) Investigation for
the Solar Dynamics Observatory (SDO)
Authors: Scherrer, P. H.; Schou, J.; Bush, R. I.; Kosovichev, A. G.;
Bogart, R. S.; Hoeksema, J. T.; Liu, Y.; Duvall, T. L.; Zhao, J.;
Title, A. M.; Schrijver, C. J.; Tarbell, T. D.; Tomczyk, S.
Bibcode: 2012SoPh..275..207S
Altcode:
The Helioseismic and Magnetic Imager (HMI) instrument and investigation
as a part of the NASA Solar Dynamics Observatory (SDO) is designed
to study convection-zone dynamics and the solar dynamo, the origin
and evolution of sunspots, active regions, and complexes of activity,
the sources and drivers of solar magnetic activity and disturbances,
links between the internal processes and dynamics of the corona and
heliosphere, and precursors of solar disturbances for space-weather
forecasts. A brief overview of the instrument, investigation objectives,
and standard data products is presented.
Title: SDO/AIA Observations of Quasi-periodic Fast (~1000 km/s)
Propagating (QFP) Waves as Evidence of Fast-mode Magnetosonic Waves
in the Low Corona: Statistics and Implications
Authors: Liu, W.; Ofman, L.; Title, A. M.; Zhao, J.; Aschwanden, M. J.
Bibcode: 2011AGUFMSH33A2043L
Altcode:
Recent EUV imaging observations from SDO/AIA led to the discovery of
quasi-periodic fast (~2000 km/s) propagating (QFP) waves in active
regions (Liu et al. 2011). They were interpreted as fast-mode
magnetosonic waves and reproduced in 3D MHD simulations (Ofman
et al. 2011). Since then, we have extended our study to a sample
of more than a dozen such waves observed during the SDO mission
(2010/04-now). We will present the statistical properties of these waves
including: (1) Their projected speeds measured in the plane of the sky
are about 400-2200 km/s, which, as the lower limits of their true speeds
in 3D space, fall in the expected range of coronal Alfven or fast-mode
speeds. (2) They usually originate near flare kernels, often in the wake
of a coronal mass ejection, and propagate in narrow funnels of coronal
loops that serve as waveguides. (3) These waves are launched repeatedly
with quasi-periodicities in the 30-200 seconds range, often lasting
for more than one hour; some frequencies coincide with those of the
quasi-periodic pulsations (QPPs) in the accompanying flare, suggestive
a common excitation mechanism. We obtained the k-omega diagrams and
dispersion relations of these waves using Fourier analysis. We estimate
their energy fluxes and discuss their contribution to coronal heating
as well as their diagnostic potential for coronal seismology.
Title: Large-scale Coronal Propagating Fronts During the Rising
Phase of Solar Cycle 24
Authors: Nitta, N. V.; Liu, W.; Schrijver, C. J.; Title, A. M.; Lemen,
J. R.
Bibcode: 2011AGUFMSH23A1941N
Altcode:
With increasing solar activity, the AIA on SDO has observed a number
of large-scale coronal propagating fronts, which are often called
"EIT waves." Although their nature is still actively debated,
these propagating fronts usually accompany CMEs, and, in certain
cases, may signify CME-related shock waves important for particle
acceleration. Using the unprecedented temporal resolution and broad
temperature coverage of the AIA, it is possible to characterize
the propagating fronts in the corona far better than before, as
demonstrated in the literature for a yet small number of cases. We
study the properties of more than 40 propagating fronts as observed
by AIA, and discuss the key properties for them to be associated with
other phenomena such as type II radio bursts, flares, CMEs, ICMEs,
and SEP events. We make use of data, both remote-sensing and in-situ,
from STEREO which provides two additional vantage points, to make the
associations more solid. For the associated phenomena, their basic
properties are correlated with those of the propagating fronts. We
also revisit the association of EIT waves with other phenomena during
the similar phase of Solar Cycle 23 and discuss possible differences
in terms of global magnetic field. Understanding their relation with
other phenomena, we can have a more complete picture of the coronal
propagating fronts in the context of CME acceleration and deceleration.
Title: Associated Solar Events
Authors: Title, A. M.
Bibcode: 2011AGUFMSH31D..08T
Altcode:
Flares and coronal mass ejections often occur in clusters. This is
not surprising because they are associated with sunspots and sunspot
emergence. The literature has had numerous papers on sympathetic flares,
stealth coronal mass ejections, and the causal association of flares and
CME's. As this is beginning written data is just coming in from SDO on
the second of the two M class flares that have occurred today - 3 August
2011. Another M class flare occurred yesterday. The GOES identifications
have the flares in three different active regions. The SDO data clearly
shows the magnetic structure of the regions are closely connected and
form a large associated active region in which destabilizations in one
segment tend to create destabilization in the other partners in the
association. The events of 2-3 August are not unique. There a numbers
on then in the SDO data even though most of the observations have
occurred in a deep solar minimum. The formation of such associations
has relevance to our understand of the drivers of violent solar events.
Title: Modeling Super-fast Magnetosonic Waves Observed by SDO in
Active Region Funnels
Authors: Ofman, L.; Liu, W.; Title, A.; Aschwanden, M.
Bibcode: 2011ApJ...740L..33O
Altcode:
Recently, quasi-periodic, rapidly propagating waves have been observed
in extreme ultraviolet by the Solar Dynamics Observatory/Atmospheric
Imaging Assembly (AIA) instrument in about 10 flare/coronal mass
ejection (CME) events thus far. A typical example is the 2010 August 1
C3.2 flare/CME event that exhibited arc-shaped wave trains propagating
in an active region (AR) magnetic funnel with ~5% intensity variations
at speeds in the range of 1000-2000 km s-1. The fast
temporal cadence and high sensitivity of AIA enabled the detection
of these waves. We identify them as fast magnetosonic waves driven
quasi-periodically at the base of the flaring region and develop
a three-dimensional MHD model of the event. For the initial state
we utilize the dipole magnetic field to model the AR and include
gravitationally stratified density at coronal temperature. At the
coronal base of the AR, we excite the fast magnetosonic wave by
periodic velocity pulsations in the photospheric plane confined to a
funnel of magnetic field lines. The excited fast magnetosonic waves
have similar amplitude, wavelength, and propagation speeds as the
observed wave trains. Based on the simulation results, we discuss the
possible excitation mechanism of the waves, their dynamical properties,
and the use of the observations for coronal MHD seismology.
Title: Coronal Seismology in the SDO Era: AIA Observations of Various
Coronal Waves Associated with CMEs/Flares
Authors: Liu, Wei; Ofman, Leon; Aschwanden, Markus J.; Nitta, Nariaki;
Zhao, Junwei; Title, Alan M.
Bibcode: 2011sdmi.confE..49L
Altcode:
MHD waves, as critical diagnostic tools of coronal seismology, can be
used to decipher otherwise elusive physical parameters of the solar
corona, such as the magnetic field strength and plasma density. They
are analogous to acoustic waves used in helioseismology. Recent high
cadence, high resolution, full-disk imaging observations from SDO/AIA
have opened a new chapter in understanding these waves. Various types
of waves associated with flares and/or CMEs have been discovered. In
this presentation, we will review such new AIA observations, focusing
on the following topics: (1) fine structures in CME-related global EUV
waves (so-called EIT waves), including a diffuse pulse superimposed
with multiple sharp fronts or "ripples" (Liu et al. 2010, ApJL); (2)
quasi-periodic fast waves traveling in coronal funnels at speeds up to
2000 km/s and associated with flares pulsating at similar frequencies
(Liu et al. 2011, ApJL); (3) interaction of global EUV waves with local
coronal structures on their paths, such as flux-rope coronal cavities
(triggered kink oscillations, Liu et al. in preparation) and coronal
holes/active regions (deflection). We will discuss the implications
of these observations on coronal seismology and on understanding their
associated flares and CMEs. We also anticipate to exchange ideas with
helioseismologists at this workshop, in a hope to bring together coronal
seismology and helioseismology techniques to advance our understanding
of solar oscillations from the interior to the upper atmosphere.
Title: The 2011 February 15 X2 Flare, Ribbons, Coronal Front, and
Mass Ejection: Interpreting the Three-dimensional Views from the
Solar Dynamics Observatory and STEREO Guided by Magnetohydrodynamic
Flux-rope Modeling
Authors: Schrijver, Carolus J.; Aulanier, Guillaume; Title, Alan M.;
Pariat, Etienne; Delannée, Cecile
Bibcode: 2011ApJ...738..167S
Altcode:
The 2011 February 15 X2.2 flare and associated Earth-directed halo
coronal mass ejection were observed in unprecedented detail with
high resolution in spatial, temporal, and thermal dimensions by the
Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory,
as well as by instruments on the two STEREO spacecraft, then at
near-quadrature relative to the Sun-Earth line. These observations
enable us to see expanding loops from a flux-rope-like structure over
the shearing polarity-inversion line between the central δ-spot groups
of AR 11158, developing a propagating coronal front ("EIT wave"),
and eventually forming the coronal mass ejection moving into the inner
heliosphere. The observations support the interpretation that all of
these features, including the "EIT wave," are signatures of an expanding
volume traced by loops (much larger than the flux rope only), surrounded
by a moving front rather than predominantly wave-like perturbations;
this interpretation is supported by previously published MHD models
for active-region and global scales. The lateral expansion of the
eruption is limited to the local helmet-streamer structure and halts
at the edges of a large-scale domain of connectivity (in the process
exciting loop oscillations at the edge of the southern polar coronal
hole). The AIA observations reveal that plasma warming occurs within
the expansion front as it propagates over quiet Sun areas. This warming
causes dimming in the 171 Å (Fe IX and Fe X) channel and brightening
in the 193 and 211 Å (Fe XII-XIV) channels along the entire front,
while there is weak 131 Å (Fe VIII and Fe XXI) emission in some
directions. An analysis of the AIA response functions shows that
sections of the front running over the quiet Sun are consistent with
adiabatic warming; other sections may require additional heating which
MHD modeling suggests could be caused by Joule dissipation. Although
for the events studied here the effects of volumetric expansion are
much more obvious than true wave phenomena, we discuss how different
magnetic environments within and around the erupting region can lead
to the signatures of either or both of these aspects.
Title: The Sun at high resolution: first results from the Sunrise
mission
Authors: Solanki, S. K.; Barthol, P.; Danilovic, S.; Feller,
A.; Gandorfer, A.; Hirzberger, J.; Lagg, A.; Riethmüller, T. L.;
Schüssler, M.; Wiegelmann, T.; Bonet, J. A.; Pillet, V. Martínez;
Khomenko, E.; del Toro Iniesta, J. C.; Domingo, V.; Palacios, J.;
Knölker, M.; González, N. Bello; Borrero, J. M.; Berkefeld, T.;
Franz, M.; Roth, M.; Schmidt, W.; Steiner, O.; Title, A. M.
Bibcode: 2011IAUS..273..226S
Altcode:
The Sunrise balloon-borne solar observatory consists of a 1m aperture
Gregory telescope, a UV filter imager, an imaging vector polarimeter,
an image stabilization system and further infrastructure. The first
science flight of Sunrise yielded high-quality data that reveal the
structure, dynamics and evolution of solar convection, oscillations
and magnetic fields at a resolution of around 100 km in the quiet
Sun. Here we describe very briefly the mission and the first results
obtained from the Sunrise data, which include a number of discoveries.
Title: Characterizing the Quiet Sun Scale Magnetic Field
Authors: Title, Alan
Bibcode: 2011IAUS..271...86T
Altcode:
Observations with the Solar Optical Telescope on Hinode indicate
that the Quiet Sun magnetic field occurs on every scale of convection
including granulation. Data reported here show that, regardless of the
position on the disk, the polarity in the inner network regions are
balanced to 1 part in 72. This is consistent with both local dynamo
processes or the creation of surface features by the granulation
downflows.
Title: Direct Imaging of Quasi-periodic Fast Propagating Waves of
~2000 km s-1 in the Low Solar Corona by the Solar Dynamics
Observatory Atmospheric Imaging Assembly
Authors: Liu, Wei; Title, Alan M.; Zhao, Junwei; Ofman, Leon;
Schrijver, Carolus J.; Aschwanden, Markus J.; De Pontieu, Bart;
Tarbell, Theodore D.
Bibcode: 2011ApJ...736L..13L
Altcode: 2011arXiv1106.3150L
Quasi-periodic propagating fast mode magnetosonic waves in the solar
corona were difficult to observe in the past due to relatively low
instrument cadences. We report here evidence of such waves directly
imaged in EUV by the new Atmospheric Imaging Assembly instrument
on board the Solar Dynamics Observatory. In the 2010 August 1 C3.2
flare/coronal mass ejection event, we find arc-shaped wave trains of
1%-5% intensity variations (lifetime ~200 s) that emanate near the
flare kernel and propagate outward up to ~400 Mm along a funnel of
coronal loops. Sinusoidal fits to a typical wave train indicate a phase
velocity of 2200 ± 130 km s-1. Similar waves propagating
in opposite directions are observed in closed loops between two flare
ribbons. In the k-ω diagram of the Fourier wave power, we find a
bright ridge that represents the dispersion relation and can be well
fitted with a straight line passing through the origin. This k-ω
ridge shows a broad frequency distribution with power peaks at 5.5,
14.5, and 25.1 mHz. The strongest signal at 5.5 mHz (period 181 s)
temporally coincides with quasi-periodic pulsations of the flare,
suggesting a common origin. The instantaneous wave energy flux
of (0.1-2.6) × 107 erg cm-2 s-1
estimated at the coronal base is comparable to the steady-state heating
requirement of active region loops.
Title: The Interface Region Imaging Spectrograph (IRIS) NASA SMEX
Authors: Lemen, James; Title, A.; De Pontieu, B.; Schrijver, C.;
Tarbell, T.; Wuelser, J.; Golub, L.; Kankelborg, C.
Bibcode: 2011SPD....42.1512L
Altcode: 2011BAAS..43S.1512L
The solar chromosphere and transition region (TR) is highly structured,
dynamic, and intimately connected to the corona. It requires more
than ten times the energy required to heat the corona, and yet it
has received far less interest because of the complexity of the
required observational and analytical tools. In the TR the density
drops by six orders of magnitude and the temperature increases by
three orders of magnitude. Hinode observations reveal the importance
the magnetic field has on this region of the solar atmosphere that
acts as the interface between the photosphere and the corona. The
Interface Region Imaging Spectrograph (IRIS) was selected for a NASA
SMEX mission in 2009 and is scheduled to launch in December 2012. IRIS
addresses critical questions in order to understand the flow of energy
and mass through the chromosphere and TR, namely: (1) Which types of
non-thermal energy dominate in the chromosphere and beyond? (2) How
does the chromosphere regulate mass and energy supply to the corona
and heliosphere? (3) How do magnetic flux and matter rise through the
lower atmosphere, and what roles dos flux emergence play in flares and
mass ejections? These questions are addressed with a high-resolution
imaging spectrometer that observes Near- and Far-VU emissions that
are formed at temperatures between 5,000K and 1.5 x 106
K. IRIS has a field-of-view of 120 arcsec, a spatial resolution
of 0.4 arcsec, and velocity resolution of 0.5 km/s. Members of the
IRIS investigation team are developing advanced radiative MHD codes
to facilitate comparison with and interpretation of observations. We
present the status of the IRIS observatory development, which completed
its Critical Design Review in December 2010.
Title: Spectropolarimetric Study of Sea-serpent Penumbral Filaments
and a Naked Sunspot
Authors: Sainz Dalda, Alberto; Tarbell, T.; Title, A.; Vargas
Dominguez, S.; Bellot Rubio, L. R.
Bibcode: 2011SPD....42.0303S
Altcode: 2011BAAS..43S.0303S
We present a spectropolarimetric study of the sea-serpent penumbral
filaments in AR NOAA 10944 and of a naked sunspot (i.e. a sunspot-like
feature without penumbra) in AR NOAA 10977. Both active regions were
observed by Hinode-SOT/SP in the photospheric lines Fe I 6301 &
6302 [[Unable to Display Character: Ǻ]]. The high spatial and
temporal resolution combined with the high polarimetric sensitivity
of these observations enables us to get a better understanding of the
dynamics of the penumbra and the moving magnetic feature (herafter MMF)
activity in and around both traditional and naked sunspots. Our results
show how the temporal evolution of the sea-serpent filaments fits
very well with the thin-tube flux model for the penumbra presented by
Schlichenmaier (2003). In addition, the spectropolarmetric analysis of
the naked sunspot addresses the issue posed by Zuccarello et al. (2009)
about the existence of bipolar MMFs around naked sunspots even when
they cannot be explained as an extension of the penumbral filaments.
Title: Direct Imaging by SDO/AIA of Quasi-periodic Propagating Fast
Mode Magnetosonic Waves of 2000 km/s in the Solar Corona
Authors: Liu, Wei; Title, A. M.; Zhao, J.; Ofman, L.; Schrijver,
C. J.; Aschwanden, M. J.; De Pontieu, B.; Tarbell, T. D.
Bibcode: 2011SPD....42.2114L
Altcode: 2011BAAS..43S.2114L
Quasi-periodic, propagating fast mode magnetosonic waves in the
corona were difficult to observe in the past due to relatively low
instrument cadences. We report here unprecedented evidence of such
waves directly imaged in EUV by the new SDO/AIA instrument. In the 2010
August 1 C3.2 flare/CME event, we find arc-shaped wave trains of 1-5%
intensity variations emanating near the flare kernel and propagating
outward along a funnel of coronal loops. Sinusoidal fits to a typical
wave train indicate a phase velocity of 2350 +/- 210 km/s. Similar
waves propagating in opposite directions are observed in closed loops
between two flare ribbons. In the k-omega diagram of the Fourier wave
power, we find a bright ridge that represents the dispersion relation
and can be well fitted with a straight line passing through the
origin, giving an equal phase and group velocity of 1630 +/- 760 km/s
averaged over the event. This k-omega ridge shows a broad frequency
distribution with prominent power at four non-harmonic frequencies,
5.5, 14.5, 25.1, and 37.9 mHz, among which the 14.5 mHz (period:
69 s) signal is the strongest. The signal at 5.5 mHz (period: 181 s,
same as chromospheric 3-minute oscillations) temporally coincides with
flare pulsations, suggesting a common origin of possibly quasi-periodic
magnetic reconnection. The instantaneous wave energy flux of (0.1-2.6)e7
ergs/cm2/s estimated at the coronal base is comparable to
the steady-state heating requirement of active region loops.
Title: Modeling Fast Magnetosonic Waves Observed by SDO in Active
region Funnels
Authors: Ofman, Leon; Liu, W.; Title, A.; Aschwanden, M.
Bibcode: 2011SPD....42.2104O
Altcode: 2011BAAS..43S.2104O
Recently, quasi-periodic, propagating waves have been observed in EUV by
the SDO/AIA instrument in about 10 flare/CME events thus far. A typical
example is the waves associated with the 2010 August 1 C3.2 flare/CME
that exhibited arc-shaped wave trains propagating in an active region
magnetic funnel with 5% intensity variations at speeds in the range
of 1000-2000 km/s. The fast temporal cadence and high sensitivity of
AIA enabled the detection of these waves. We identify them as fast
magnetosonic waves driven quasi-periodically at the base of the flaring
region, and develop a three-dimensional MHD model of the event. For
the initial state we utilize the dipole magnetic field to model the
active region, and include gravitationally stratified density at coronal
temperature. At the coronal base of the active region we excite the fast
magnetosonic wave by periodic velocity pulsations in the photospheric
plane confined to the funnel of magnetic field line. The excited fast
magnetosonic waves have similar amplitude, wavelength and propagation
speeds as the observed wave trains. Based on the simulation results, we
discuss the possible excitation mechanism of the waves, their dynamical
properties, and the use of the event for coronal MHD seismology.
Title: Long-range magnetic couplings between solar flares and coronal
mass ejections observed by SDO and STEREO
Authors: Schrijver, C. J.; Title, A. M.
Bibcode: 2011JGRA..116.4108S
Altcode:
The combination of SDO and STEREO observations enables us to
view much of the solar surface and atmosphere simultaneously and
continuously. These near-global observations often show near-synchronous
long-distance interactions between magnetic domains that exhibit flares,
eruptions, and frequent minor forms of activity. Here we analyze a
series of flares, filament eruptions, coronal mass ejections, and
related events which occurred on 1-2 August 2010. These events extend
over a full hemisphere of the Sun, only two-thirds of which is visible
from the Earth's perspective. The combination of coronal observations
and global field modeling reveals the many connections between these
events by magnetic field lines, particularly those at topological
divides. We find that all events of substantial coronal activity,
including those where flares and eruptions initiate, are connected by
a system of separatrices, separators, and quasi-separatrix layers, with
little activity within the deep interiors of domains of connectivity. We
conclude that for this sequence of events the evolution of field on
the hemisphere invisible from Earth's perspective is essential to
the evolution, and possibly even to the initiation, of the flares and
eruptions over an area that spans at least 180 degrees in longitude. Our
findings emphasize that the search for the factors that play a role
in the initiation and evolution of eruptive and explosive phenomena,
sought after for improved space weather forecasting, requires knowledge
of much, if not all, of the solar surface field.
Title: Magneto-thermal convection in solar prominences
Authors: Berger, Thomas; Testa, Paola; Hillier, Andrew; Boerner, Paul;
Low, Boon Chye; Shibata, Kazunari; Schrijver, Carolus; Tarbell, Ted;
Title, Alan
Bibcode: 2011Natur.472..197B
Altcode:
Coronal cavities are large low-density regions formed by
hemispheric-scale magnetic flux ropes suspended in the Sun's outer
atmosphere. They evolve over time, eventually erupting as the dark
cores of coronal mass ejections. Although coronal mass ejections are
common and can significantly affect planetary magnetospheres, the
mechanisms by which cavities evolve to an eruptive state remain poorly
understood. Recent optical observations of high-latitude `polar crown'
prominences within coronal cavities reveal dark, low-density `bubbles'
that undergo Rayleigh-Taylor instabilities to form dark plumes rising
into overlying coronal cavities. These observations offered a possible
mechanism for coronal cavity evolution, although the nature of the
bubbles, particularly their buoyancy, was hitherto unclear. Here we
report simultaneous optical and extreme-ultraviolet observations of
polar crown prominences that show that these bubbles contain plasma at
temperatures in the range (2.5-12)×105 kelvin, which is
25-120 times hotter than the overlying prominence. This identifies a
source of the buoyancy, and suggests that the coronal cavity-prominence
system supports a novel form of magneto-thermal convection in the solar
atmosphere, challenging current hydromagnetic concepts of prominences
and their relation to coronal cavities.
Title: Chromospheric Jet and Growing "Loop" Observed by Hinode: New
Evidence of Fan-spine Magnetic Topology Resulting from Flux Emergence
Authors: Liu, Wei; Berger, Thomas E.; Title, Alan M.; Tarbell,
Theodore D.; Low, B. C.
Bibcode: 2011ApJ...728..103L
Altcode: 2010arXiv1012.1897L
We present observations of a chromospheric jet and growing "loop" system
that show new evidence of a fan-spine topology resulting from magnetic
flux emergence. This event, occurring in an equatorial coronal hole on
2007 February 9, was observed by the Hinode Solar Optical Telescope in
the Ca II H line in unprecedented detail. The predecessor of the jet is
a bundle of fine material threads that extend above the chromosphere and
appear to rotate about the bundle axis at ~50 km s-1 (period
lsim200 s). These rotations or transverse oscillations propagate upward
at velocities up to 786 km s-1. The bundle first slowly and
then rapidly swings up, with the transition occurring at the onset of an
A4.9 flare. A loop expands simultaneously in these two phases (velocity:
16-135 km s-1). Near the peak of the flare, the loop appears
to rupture; simultaneous upward ejecta and mass downflows faster than
free-fall appear in one of the loop legs. The material bundle then
swings back in a whip-like manner and develops into a collimated jet,
which is orientated along the inferred open-field lines with transverse
oscillations continuing at slower rates. Some material falls back along
smooth streamlines, showing no more oscillations. At low altitudes, the
streamlines bifurcate at presumably a magnetic null point and bypass
an inferred dome, depicting an inverted-Y geometry. These streamlines
closely match in space the late Ca II H loop and X-ray flare loop. These
observations are consistent with the model that flux emergence in an
open-field region leads to magnetic reconnection, forming a jet and
fan-spine topology. We propose that the material bundle and collimated
jet represent the outer spine in quasi-static and eruptive stages,
respectively, and the growing loop is a two-dimensional projection of
the three-dimensional fan surface.
Title: The Wave-Front Correction System for the Sunrise Balloon-Borne
Solar Observatory
Authors: Berkefeld, T.; Schmidt, W.; Soltau, D.; Bell, A.;
Doerr, H. P.; Feger, B.; Friedlein, R.; Gerber, K.; Heidecke, F.;
Kentischer, T.; v. d. Lühe, O.; Sigwarth, M.; Wälde, E.; Barthol,
P.; Deutsch, W.; Gandorfer, A.; Germerott, D.; Grauf, B.; Meller, R.;
Álvarez-Herrero, A.; Knölker, M.; Martínez Pillet, V.; Solanki,
S. K.; Title, A. M.
Bibcode: 2011SoPh..268..103B
Altcode: 2010SoPh..tmp..236B; 2010arXiv1009.3196B
This paper describes the wave-front correction system developed for
the Sunrise balloon telescope, and it provides information about its
in-flight performance. For the correction of low-order aberrations,
a Correlating Wave-Front Sensor (CWS) was used. It consisted of a
six-element Shack - Hartmann wave-front sensor (WFS), a fast tip-tilt
mirror for the compensation of image motion, and an active telescope
secondary mirror for focus correction. The CWS delivered a stabilized
image with a precision of 0.04 arcsec (rms), whenever the coarse
pointing was better than ± 45 arcsec peak-to-peak. The automatic
focus adjustment maintained a focus stability of 0.01 waves in the
focal plane of the CWS. During the 5.5 day flight, good image quality
and stability were achieved during 33 hours, containing 45 sequences,
which lasted between 10 and 45 min.
Title: The Sunrise Mission
Authors: Barthol, P.; Gandorfer, A.; Solanki, S. K.; Schüssler,
M.; Chares, B.; Curdt, W.; Deutsch, W.; Feller, A.; Germerott, D.;
Grauf, B.; Heerlein, K.; Hirzberger, J.; Kolleck, M.; Meller, R.;
Müller, R.; Riethmüller, T. L.; Tomasch, G.; Knölker, M.; Lites,
B. W.; Card, G.; Elmore, D.; Fox, J.; Lecinski, A.; Nelson, P.;
Summers, R.; Watt, A.; Martínez Pillet, V.; Bonet, J. A.; Schmidt,
W.; Berkefeld, T.; Title, A. M.; Domingo, V.; Gasent Blesa, J. L.;
del Toro Iniesta, J. C.; López Jiménez, A.; Álvarez-Herrero, A.;
Sabau-Graziati, L.; Widani, C.; Haberler, P.; Härtel, K.; Kampf,
D.; Levin, T.; Pérez Grande, I.; Sanz-Andrés, A.; Schmidt, E.
Bibcode: 2011SoPh..268....1B
Altcode: 2010arXiv1009.2689B; 2010SoPh..tmp..224B
The first science flight of the balloon-borne Sunrise telescope took
place in June 2009 from ESRANGE (near Kiruna/Sweden) to Somerset
Island in northern Canada. We describe the scientific aims and
mission concept of the project and give an overview and a description
of the various hardware components: the 1-m main telescope with its
postfocus science instruments (the UV filter imager SuFI and the imaging
vector magnetograph IMaX) and support instruments (image stabilizing
and light distribution system ISLiD and correlating wavefront sensor
CWS), the optomechanical support structure and the instrument mounting
concept, the gondola structure and the power, pointing, and telemetry
systems, and the general electronics architecture. We also explain
the optimization of the structural and thermal design of the complete
payload. The preparations for the science flight are described,
including AIV and ground calibration of the instruments. The course
of events during the science flight is outlined, up to the recovery
activities. Finally, the in-flight performance of the instrumentation
is discussed.
Title: The Filter Imager SuFI and the Image Stabilization and Light
Distribution System ISLiD of the Sunrise Balloon-Borne Observatory:
Instrument Description
Authors: Gandorfer, A.; Grauf, B.; Barthol, P.; Riethmüller, T. L.;
Solanki, S. K.; Chares, B.; Deutsch, W.; Ebert, S.; Feller, A.;
Germerott, D.; Heerlein, K.; Heinrichs, J.; Hirche, D.; Hirzberger,
J.; Kolleck, M.; Meller, R.; Müller, R.; Schäfer, R.; Tomasch,
G.; Knölker, M.; Martínez Pillet, V.; Bonet, J. A.; Schmidt, W.;
Berkefeld, T.; Feger, B.; Heidecke, F.; Soltau, D.; Tischenberg, A.;
Fischer, A.; Title, A.; Anwand, H.; Schmidt, E.
Bibcode: 2011SoPh..268...35G
Altcode: 2010SoPh..tmp..176G; 2010arXiv1009.1037G
We describe the design of the Sunrise Filter Imager (SuFI) and the
Image Stabilization and Light Distribution (ISLiD) unit onboard the
Sunrise balloon borne solar observatory. This contribution provides the
necessary information which is relevant to understand the instruments'
working principles, the relevant technical data, and the necessary
information about calibration issues directly related to the science
data.
Title: The Origins of Hot Plasma in the Solar Corona
Authors: De Pontieu, B.; McIntosh, S. W.; Carlsson, M.; Hansteen,
V. H.; Tarbell, T. D.; Boerner, P.; Martinez-Sykora, J.; Schrijver,
C. J.; Title, A. M.
Bibcode: 2011Sci...331...55D
Altcode:
The Sun's outer atmosphere, or corona, is heated to millions of degrees,
considerably hotter than its surface or photosphere. Explanations for
this enigma typically invoke the deposition in the corona of nonthermal
energy generated by magnetoconvection. However, the coronal heating
mechanism remains unknown. We used observations from the Solar Dynamics
Observatory and the Hinode solar physics mission to reveal a ubiquitous
coronal mass supply in which chromospheric plasma in fountainlike jets
or spicules is accelerated upward into the corona, with much of the
plasma heated to temperatures between ~0.02 and 0.1 million kelvin (MK)
and a small but sufficient fraction to temperatures above 1 MK. These
observations provide constraints on the coronal heating mechanism(s)
and highlight the importance of the interface region between photosphere
and corona.
Title: Greenhouse effect in quiescent prominences
Authors: Ryutova, M.; Berger, T. E.; Title, A. M.
Bibcode: 2010AGUFMSH51A1664R
Altcode:
Quiescent prominences, by definition, are huge ``clouds'' of cool,
dense plasma overlying rarefied hot corona and supported by a complex
magnetic field anchored in the photosphere along the magnetic polarity
inversion line. One of the most prominent features in their dynamics
is formation, growth and collapse of bubble/cavities filled by coronal
plasma and emerging, often repeatedly, under a prominence body. As
such, prominence/corona interface itself is subject of fundamental
plasma instabilities, which include development of a regular series
of plumes and spikes typical to the Rayleigh-Taylor instability, the
Kelvin-Helmholtz instability, often followed by a sudden collimated mass
upflow, which, in nonlinear stage having an explosive character may
be responsible for CMEs. These were only recently studied in detail
with high cadence, high resolution data obtained from the Hinode
satellite. Even more surprises are brought by the SDO/AIA instrument
showing the Sun's atmosphere in 12 visible and EUV wavelengths. AIA
multi-wavelength images in a temperature range from 105
~K to 2 × 106 ~K combined with the Hinode/SOT data show
that plasma inside the prominence cavity, being as expected, at
coronal temperatures, in fact exceeds the temperature of the ambient
corona. We suggest that an energetically open highly dynamic processes
releasing energy at the prominence/cavity interface accompanied by the
``radiative exchange'', may cause additional increase of temperature
and/or density inside cavity. Given pervasive character of prominences,
future studies will allow us to perform quantitative and statistical
analysis, and reveal relations between the size of cavity, its
temperature, and magnetic properties.
Title: Coordinated observations of solar prominences with Hinode/SOT
and SDO/AIA
Authors: Berger, T. E.; Tarbell, T. D.; Schrijver, C. J.; Title,
A. M.; Boerner, P.; Shine, R. A.
Bibcode: 2010AGUFMSH21C..04B
Altcode:
We show the first detailed study of a solar quiescent prominence
using simultaneous observations from the Hinode/SOT and SDO/AIA
instruments. The prominence studied is a polar crown prominence
located at the base of a large coronal cavity on the NW solar limb on
22-June-2010. Hinode observed the prominence for 2.75 hours running
the HOP 73 prominence observation program to acquire Ca II H-line
filtergrams and H-alpha doppler observations at a 20-second cadence. SOT
observations in Ca II H-line and H-alpha spectral lines reveal the
common dynamics of filamentary downflows and large-scale oscillations
of the prominence body. In addition a dark cavity is observed to
rise into the prominence and stagnate before going unstable to form
Rayleigh-Taylor plume upflows. AIA observations in the 304, 171, 193,
and 211 channels with 14 second cadence reveal that both the cavity
and the plume upflows are bright in these hotter passbands. Filter
ratio measurements as well as preliminary EM estimates imply that
the cavity and plume plasma temperature is at least 10^6 K. Plasma at
this temperature has never been detected or theorized in a confined
configuration in the lower chromosphere below a prominence. Assuming
an electron number density of 3e09 cm-3, the balance between thermal
pressure in the cavity and magnetic pressure in the overlying prominence
implies a magnetic flux density of order 10 gauss, in line with earlier
measurements of prominence magnetic fields. However the cavity likely
contains a significant magnetic energy density of its own implying that
the prominence magnetic fields may need to be significantly higher to
balance the cavity buoyancy. The existence of 10^6 K plasma confined
below a quiescent prominence and the subsequent onset of buoyancy
instabilities present new challenges to theories of prominence and
coronal cavity formation and suggest new avenues for supply of mass
and magnetic flux to the associated coronal cavity systems that make
up the bulk of CMEs. Hinode/SOT Ca II H-line image overlain on SDO/AIA
304A image of a quiescent solar prominence.
Title: First SDO/AIA Observations of Global Coronal EUV "Waves":
Multiple Components and "Ripples"
Authors: Liu, W.; Nitta, N. V.; Schrijver, C. J.; Title, A. M.;
Tarbell, T. D.
Bibcode: 2010AGUFMSH13A..07L
Altcode:
Global coronal EUV disturbances (so-called "EIT waves") are useful
diagnostics for physical conditions on the Sun. Major drawbacks that
hindered our understanding of this phenomenon were previous instruments'
single view point, low cadence (e.g., 12 minutes of EIT), and limited
wavelength coverage. The Atmospheric Imaging Assembly (AIA) on board
the Solar Dynamics Observatory (SDO) observes the full-sun corona
at 10 EUV and UV wavelengths, covering a wide range of temperatures,
with high resolution (1.4") and cadence (up to 12 s). It thus offers a
great chance to end the decade long debate on the nature of global EUV
"waves". We present here the first AIA observations of such phenomenon
on 2010 April 8 revealed in unprecedented detail and discuss their
physical implications. The disturbance exhibits two components: one
weak, diffuse pulse superimposed by multiple strong, sharp fronts,
which again have slow and fast components. The disturbance originates
in front of erupting coronal loops and the slow sharp front undergoes
acceleration, both implying the disturbance being driven by the
coronal mass ejection (CME). Even at a 20 s cadence, the diffuse pulse
propagates at a surprisingly constant velocity of ~200 km/s, weakly
dependent on direction. The fast sharp front overtakes the slow front,
producing multiple "ripples" and steepening of the local pulse, and both
fronts propagate independently afterwards. These resemble the nature
of real waves. Unexpectedly, the amplitude and FWHM of the diffuse
pulse decreases linearly with distance. The diffuse pulse appears as
emission enhancement at hotter 193 Å but reduction at cooler 171 Å,
suggestive of heating, while the sharp fronts appear as enhancement at
both wavelengths, indicating density increase. As evidence for both
wave and non-wave models of "EIT waves" has been found, we suggest
that a hybrid model combining both mechanisms (e.g., Cohen et al. 2010)
may best explaine the data. In addition to the global EUV disturbance,
we found fast (600-1100 km/s) features repeated at 100 s intervals
as tentative evidence of fast mode MHD waves. Discoveries of the fast
features, multiple ripples, and two-component fronts were made possible
for the first time thanks to AIA's high cadences and sensitivities.
Title: The role of the chromosphere in filling the corona with hot
plasma (Invited)
Authors: de Pontieu, B.; McIntosh, S. W.; Carlsson, M.; Hansteen,
V. H.; Tarbell, T. D.; Boerner, P.; Martinez-Sykora, J.; Schrijver,
C. J.; Title, A. M.
Bibcode: 2010AGUFMSH21C..03D
Altcode:
We use coordinated observations from the Solar Dynamics Observatory
(SDO), Hinode and the Swedish Solar Telescope (SST) to show how
plasma is heated to coronal temperatures from its source in the
chromosphere. Our observations reveal a ubiquitous mass supply
for the solar corona in which chromospheric plasma is accelerated
upward into the corona with much of the plasma heated to transition
region temperatures, and a small, but significant fraction heated
to temperatures in excess of 1 million K. Our observations show,
for the first time, how chromospheric spicules, fountain-like jets
that have long been considered potential candidates for coronal
heating, are directly associated with heating of plasma to coronal
temperatures. These results provide strong physical constraints on
the mechanism(s) responsible for coronal heating and do not seem
compatible with current models. The association with chromospheric
spicules highlights the importance of the interface region between
the photosphere and corona to gain a full understanding of the coronal
heating problem.
Title: Observation of Plasma Instabilities in Quiescent Prominences
Authors: Ryutova, M.; Berger, T.; Frank, Z.; Tarbell, T.; Title, A.
Bibcode: 2010SoPh..267...75R
Altcode: 2010SoPh..tmp..170R
We study dynamics of quiescent prominences using several data sets taken
with the Solar Optical Telescope (SOT) on Hinode. We find a number of
processes occurring at different stages of prominence evolution that
are common for all of our chosen cases and, having universal character,
can be related to fundamental plasma instabilities. We combine the
observational evidence and theory to identify these instabilities. Here
we discuss three examples: i) prominence cavity formation and its
evolution, associated with a screw-pinch instability; ii) development
of a regular series of plumes and spikes typical to the Rayleigh -
Taylor (RT) instability; and iii) the appearance of growing ripples at
the prominence/corona interface, often followed by a sudden collimated
mass upflow, attributed to the Kelvin - Helmholtz (KH) instability. The
conditions for transition from a linear (rippling mode) to nonlinear
stage of the KH instability, known to have an explosive character,
are specified. Given excellent Hinode data, all three aspects of
prominence dynamics allow quantitative analysis.
Title: SUNRISE: Instrument, Mission, Data, and First Results
Authors: Solanki, S. K.; Barthol, P.; Danilovic, S.; Feller, A.;
Gandorfer, A.; Hirzberger, J.; Riethmüller, T. L.; Schüssler, M.;
Bonet, J. A.; Martínez Pillet, V.; del Toro Iniesta, J. C.; Domingo,
V.; Palacios, J.; Knölker, M.; Bello González, N.; Berkefeld, T.;
Franz, M.; Schmidt, W.; Title, A. M.
Bibcode: 2010ApJ...723L.127S
Altcode: 2010arXiv1008.3460S
The SUNRISE balloon-borne solar observatory consists of a 1 m aperture
Gregory telescope, a UV filter imager, an imaging vector polarimeter,
an image stabilization system, and further infrastructure. The first
science flight of SUNRISE yielded high-quality data that revealed the
structure, dynamics, and evolution of solar convection, oscillations,
and magnetic fields at a resolution of around 100 km in the quiet
Sun. After a brief description of instruments and data, the first
qualitative results are presented. In contrast to earlier observations,
we clearly see granulation at 214 nm. Images in Ca II H display narrow,
short-lived dark intergranular lanes between the bright edges of
granules. The very small-scale, mixed-polarity internetwork fields
are found to be highly dynamic. A significant increase in detectable
magnetic flux is found after phase-diversity-related reconstruction
of polarization maps, indicating that the polarities are mixed right
down to the spatial resolution limit and probably beyond.
Title: Transverse Component of the Magnetic Field in the Solar
Photosphere Observed by SUNRISE
Authors: Danilovic, S.; Beeck, B.; Pietarila, A.; Schüssler, M.;
Solanki, S. K.; Martínez Pillet, V.; Bonet, J. A.; del Toro Iniesta,
J. C.; Domingo, V.; Barthol, P.; Berkefeld, T.; Gandorfer, A.;
Knölker, M.; Schmidt, W.; Title, A. M.
Bibcode: 2010ApJ...723L.149D
Altcode: 2010arXiv1008.1535D
We present the first observations of the transverse component of
a photospheric magnetic field acquired by the imaging magnetograph
SUNRISE/IMaX. Using an automated detection method, we obtain statistical
properties of 4536 features with significant linear polarization
signal. We obtain a rate of occurrence of 7 × 10-4
s-1 arcsec-2, which is 1-2 orders of magnitude
larger than the values reported by previous studies. We show that
these features have no characteristic size or lifetime. They appear
preferentially at granule boundaries with most of them being caught
in downflow lanes at some point. Only a small percentage are entirely
and constantly embedded in upflows (16%) or downflows (8%).
Title: First SDO AIA Observations of a Global Coronal EUV "Wave":
Multiple Components and "Ripples"
Authors: Liu, Wei; Nitta, Nariaki V.; Schrijver, Carolus J.; Title,
Alan M.; Tarbell, Theodore D.
Bibcode: 2010ApJ...723L..53L
Altcode: 2012arXiv1201.0815L
We present the first Solar Dynamics Observatory Atmospheric Imaging
Assembly (AIA) observations of a global coronal EUV disturbance
(so-called "EIT wave") revealed in unprecedented detail. The disturbance
observed on 2010 April 8 exhibits two components: one diffuse pulse
superimposed, on which are multiple sharp fronts that have slow and
fast components. The disturbance originates in front of erupting coronal
loops and some sharp fronts undergo accelerations, both effects implying
that the disturbance is driven by a coronal mass ejection. The diffuse
pulse, propagating at a uniform velocity of 204-238 km s-1
with very little angular dependence within its extent in the south,
maintains its coherence and stable profile for ~30 minutes. Its arrival
at increasing distances coincides with the onsets of loop expansions and
the slow sharp front. The fast sharp front overtakes the slow front,
producing multiple "ripples" and steepening the local pulse, and both
fronts propagate independently afterward. This behavior resembles
the nature of real waves. Unexpectedly, the amplitude and FWHM of
the diffuse pulse decrease linearly with distance. A hybrid model,
combining both wave and non-wave components, can explain many, but
not all, of the observations. Discoveries of the two-component fronts
and multiple ripples were made possible for the first time thanks to
AIA's high cadences (<=20 s) and high signal-to-noise ratio.
Title: Magnetic Loops in the Quiet Sun
Authors: Wiegelmann, T.; Solanki, S. K.; Borrero, J. M.; Martínez
Pillet, V.; del Toro Iniesta, J. C.; Domingo, V.; Bonet, J. A.;
Barthol, P.; Gandorfer, A.; Knölker, M.; Schmidt, W.; Title, A. M.
Bibcode: 2010ApJ...723L.185W
Altcode: 2010arXiv1009.4715W
We investigate the fine structure of magnetic fields in the atmosphere
of the quiet Sun. We use photospheric magnetic field measurements from
SUNRISE/IMaX with unprecedented spatial resolution to extrapolate
the photospheric magnetic field into higher layers of the solar
atmosphere with the help of potential and force-free extrapolation
techniques. We find that most magnetic loops that reach into the
chromosphere or higher have one footpoint in relatively strong magnetic
field regions in the photosphere. Ninety-one percent of the magnetic
energy in the mid-chromosphere (at a height of 1 Mm) is in field
lines, whose stronger footpoint has a strength of more than 300 G,
i.e., above the equipartition field strength with convection. The
loops reaching into the chromosphere and corona are also found to be
asymmetric in the sense that the weaker footpoint has a strength B <
300 G and is located in the internetwork (IN). Such loops are expected
to be strongly dynamic and have short lifetimes, as dictated by the
properties of the IN fields.
Title: Fully Resolved Quiet-Sun Magnetic flux Tube Observed with
the SUNRISE/IMAX Instrument
Authors: Lagg, A.; Solanki, S. K.; Riethmüller, T. L.; Martínez
Pillet, V.; Schüssler, M.; Hirzberger, J.; Feller, A.; Borrero,
J. M.; Schmidt, W.; del Toro Iniesta, J. C.; Bonet, J. A.; Barthol, P.;
Berkefeld, T.; Domingo, V.; Gandorfer, A.; Knölker, M.; Title, A. M.
Bibcode: 2010ApJ...723L.164L
Altcode: 2010arXiv1009.0996L
Until today, the small size of magnetic elements in quiet-Sun areas has
required the application of indirect methods, such as the line-ratio
technique or multi-component inversions, to infer their physical
properties. A consistent match to the observed Stokes profiles could
only be obtained by introducing a magnetic filling factor that specifies
the fraction of the observed pixel filled with magnetic field. Here,
we investigate the properties of a small magnetic patch in the quiet
Sun observed with the IMaX magnetograph on board the balloon-borne
telescope SUNRISE with unprecedented spatial resolution and low
instrumental stray light. We apply an inversion technique based on
the numerical solution of the radiative transfer equation to retrieve
the temperature stratification and the field strength in the magnetic
patch. The observations can be well reproduced with a one-component,
fully magnetized atmosphere with a field strength exceeding 1 kG and
a significantly enhanced temperature in the mid to upper photosphere
with respect to its surroundings, consistent with semi-empirical flux
tube models for plage regions. We therefore conclude that, within the
framework of a simple atmospheric model, the IMaX measurements resolve
the observed quiet-Sun flux tube.
Title: Quiet-sun Intensity Contrasts in the Near-ultraviolet as
Measured from SUNRISE
Authors: Hirzberger, J.; Feller, A.; Riethmüller, T. L.; Schüssler,
M.; Borrero, J. M.; Afram, N.; Unruh, Y. C.; Berdyugina, S. V.;
Gandorfer, A.; Solanki, S. K.; Barthol, P.; Bonet, J. A.; Martínez
Pillet, V.; Berkefeld, T.; Knölker, M.; Schmidt, W.; Title, A. M.
Bibcode: 2010ApJ...723L.154H
Altcode:
We present high-resolution images of the Sun in the near-ultraviolet
spectral range between 214 nm and 397 nm as obtained from the first
science flight of the 1 m SUNRISE balloon-borne solar telescope. The
quiet-Sun rms intensity contrasts found in this wavelength range are
among the highest values ever obtained for quiet-Sun solar surface
structures—up to 32.8% at a wavelength of 214 nm. We compare the
rms contrasts obtained from the observational data with theoretical
intensity contrasts obtained from numerical magnetohydrodynamic
simulations. For 388 nm and 312 nm the observations agree well with
the numerical simulations whereas at shorter wavelengths discrepancies
between observed and simulated contrasts remain.
Title: Simulation of the Formation of a Solar Active Region
Authors: Cheung, M. C. M.; Rempel, M.; Title, A. M.; Schüssler, M.
Bibcode: 2010ApJ...720..233C
Altcode: 2010arXiv1006.4117C
We present a radiative magnetohydrodynamics simulation of the formation
of an active region (AR) on the solar surface. The simulation models
the rise of a buoyant magnetic flux bundle from a depth of 7.5 Mm in
the convection zone up into the solar photosphere. The rise of the
magnetic plasma in the convection zone is accompanied by predominantly
horizontal expansion. Such an expansion leads to a scaling relation
between the plasma density and the magnetic field strength such that
B vprop rhov1/2. The emergence of magnetic flux into the
photosphere appears as a complex magnetic pattern, which results
from the interaction of the rising magnetic field with the turbulent
convective flows. Small-scale magnetic elements at the surface
first appear, followed by their gradual coalescence into larger
magnetic concentrations, which eventually results in the formation
of a pair of opposite polarity spots. Although the mean flow pattern
in the vicinity of the developing spots is directed radially outward,
correlations between the magnetic field and velocity field fluctuations
allow the spots to accumulate flux. Such correlations result from
the Lorentz-force-driven, counterstreaming motion of opposite polarity
fragments. The formation of the simulated AR is accompanied by transient
light bridges between umbrae and umbral dots. Together with recent
sunspot modeling, this work highlights the common magnetoconvective
origin of umbral dots, light bridges, and penumbral filaments.
Title: Quiet-Sun intensity contrasts in the near ultraviolet
Authors: Hirzberger, Johann; Feller, Alex; Riethmüller, Tino L.;
Schüssler, Manfred; Borrero, Juan M.; Afram, Nadine; Unruh, Yvonne C.;
Berdyugina, Svetlana V.; Gandorfer, Achim; Solanki, Sami K.; Barthol,
Peter; Bonet, Jose A.; Martínez Pillet, Valentin; Berkefeld, Thomas;
Knölker, Michael; Schmidt, Wolfgang; Title, Alan M.
Bibcode: 2010arXiv1009.1050H
Altcode:
We present high-resolution images of the Sun in the near ultraviolet
spectral range between 214 nm and 397 nm as obtained from the first
science flight of the 1-m Sunrise balloon-borne solar telescope. The
quiet-Sun rms intensity contrasts found in this wavelength range
are among the highest values ever obtained for quiet-Sun solar
surface structures - up to 32.8% at a wavelength of 214 nm. We
compare with theoretical intensity contrasts obtained from numerical
magneto-hydrodynamic simulations. For 388 nm and 312 nm the observations
agree well with the numerical simulations whereas at shorter wavelengths
discrepancies between observed and simulated contrasts remain.
Title: Magnetic Field Topology and the Thermal Structure of the
Corona over Solar Active Regions
Authors: Schrijver, Carolus J.; DeRosa, Marc L.; Title, Alan M.
Bibcode: 2010ApJ...719.1083S
Altcode:
Solar extreme ultraviolet (EUV) images of quiescent active-region
coronae are characterized by ensembles of bright 1-2 MK loops that fan
out from select locations. We investigate the conditions associated
with the formation of these persistent, relatively cool, loop fans
within and surrounding the otherwise 3-5 MK coronal environment by
combining EUV observations of active regions made with TRACE with
global source-surface potential-field models based on the full-sphere
photospheric field from the assimilation of magnetograms that are
obtained by the Michelson Doppler Imager (MDI) on SOHO. We find that in
the selected active regions with largely potential-field configurations
these fans are associated with (quasi-)separatrix layers (QSLs) within
the strong-field regions of magnetic plage. Based on the empirical
evidence, we argue that persistent active-region cool-loop fans are
primarily related to the pronounced change in connectivity across a QSL
to widely separated clusters of magnetic flux, and confirm earlier work
that suggested that neither a change in loop length nor in base field
strengths across such topological features are of prime importance to
the formation of the cool-loop fans. We discuss the hypothesis that
a change in the distribution of coronal heating with height may be
involved in the phenomenon of relatively cool coronal loop fans in
quiescent active regions.
Title: Emergence of Helical Flux and the Formation of an Active
Region Filament Channel
Authors: Lites, B. W.; Kubo, M.; Berger, T.; Frank, Z.; Shine, R.;
Tarbell, T.; Title, A.; Okamoto, T. J.; Otsuji, K.
Bibcode: 2010ApJ...718..474L
Altcode:
We present comprehensive observations of the formation and evolution
of a filament channel within NOAA Active Region (AR) 10978 from
Hinode/Solar Optical Telescope and TRACE. We employ sequences
of Hinode spectro-polarimeter maps of the AR, accompanying Hinode
Narrowband Filter Instrument magnetograms in the Na I D1 line, Hinode
Broadband Filter Instrument filtergrams in the Ca II H line and G-band,
Hinode X-ray telescope X-ray images, and TRACE Fe IX 171 Å image
sequences. The development of the channel resembles qualitatively
that presented by Okamoto et al. in that many indicators point to
the emergence of a pre-existing sub-surface magnetic flux rope. The
consolidation of the filament channel into a coherent structure takes
place rapidly during the course of a few hours, and the filament form
then gradually shrinks in width over the following two days. Particular
to this filament channel is the observation of a segment along its
length of horizontal, weak (500 G) flux that, unlike the rest of the
filament channel, is not immediately flanked by strong vertical plage
fields of opposite polarity on each side of the filament. Because this
isolated horizontal field is observed in photospheric lines, we infer
that it is unlikely that the channel formed as a result of reconnection
in the corona, but the low values of inferred magnetic fill fraction
along the entire length of the filament channel suggest that the bulk
of the field resides somewhat above the low photosphere. Correlation
tracking of granulation in the G band presents no evidence for either
systematic flows toward the channel or systematic shear flows along
it. The absence of these flows, along with other indications of these
data from multiple sources, reinforces (but does not conclusively
demonstrate) the picture of an emerging flux rope as the origin of
this AR filament channel.
Title: Flight control software for the wave-front sensor of SUNRISE
1m balloon telescope
Authors: Bell, Alexander; Barthol, Peter; Berkefeld, Thomas; Feger,
Bernhard; Gandorfer, Achim M.; Heidecke, Frank; Knoelker, Michael;
Martinez Pillet, Valentin; Schmidt, Wolfgang; Sigwarth, Michael;
Solanki, Sami K.; Soltau, Dirk; Title, Alan M.
Bibcode: 2010SPIE.7740E..03B
Altcode: 2010SPIE.7740E...2B
This paper describes the flight control software of the wave-front
correction system that flew on the 2009 science flight of the Sunrise
balloon telescope. The software discussed here allowed fully automated
operations of the wave-front sensor, communications with the adaptive
optics sub-system, the pointing system, the instrument control unit
and the main telescope controller. The software was developed using
modern object oriented analysis and design techniques, and consists
of roughly 13.000 lines of C++ code not counting code written for the
on-board communication layer. The software operated error free during
the 5.5 day flight.
Title: SUNRISE Impressions from a successful science flight
Authors: Schmidt, W.; Solanki, S. K.; Barthol, P.; Berkefeld, T.;
Gandorfer, A.; Knölker, M.; Martínez Pillet, V.; Schüssler, M.;
Title, A.
Bibcode: 2010AN....331..601S
Altcode:
SUNRISE is a balloon-borne telescope with an aperture of one meter. It
is equipped with a filter imager for the UV wavelength range between
214 nm and 400 nm (SUFI), and with a spectro-polarimeter that measures
the magnetic field of the photosphere using the Fe I line at 525.02
nm that has a Landé factor of 3. SUNRISE performed its first science
flight from 8 to 14 June 2009. It was launched at the Swedish ESRANGE
Space Center and cruised at an altitude of about 36 km and geographic
latitudes between 70 and 74 degrees to Somerset Island in northern
Canada. There, all data, the telescope and the gondola were successfully
recovered. During its flight, Sunrise achieved high pointing stability
during 33 hours, and recorded about 1.8 TB of science data. Already at
this early stage of data processing it is clear that SUNRISE recorded
UV images of the solar photosphere, and spectropolarimetric measurements
of the quiet Sun's magnetic field of unprecedented quality.
Title: Considerations for the next generation of solar telescopes:
A systems approach to solar physics
Authors: Title, A.
Bibcode: 2010AN....331..596T
Altcode:
The exciting new high resolution images from the one meter Sunrise
balloon telescope and the first images from the 1.6 meter Big Bear
telescope together with the continuing data from the 1 meter Swedish
Solar Observatory demonstrate the promise of the new generation of
multimeter solar telescopes. While the promise of the new generation of
telescopes is great the technical challenges to build them will require
the efforts of a significant fraction of the solar community. In this
talk I will emphasize the need for an integrated systems approach to
the development of the telescope, its instruments, its software, and
its operations and management structures. The experience of several
decades of space mission has taught us a great deal about the value
of planning mission development from the definition of the primary
scientific objectives to the delivery of the data to the science
community. Much of these lessons learned, often painfully, should
provide guidance to those in developing the new telescope systems.
Title: Quiescent Prominence Dynamics Observed with the Hinode Solar
Optical Telescope. I. Turbulent Upflow Plumes
Authors: Berger, Thomas E.; Slater, Gregory; Hurlburt, Neal; Shine,
Richard; Tarbell, Theodore; Title, Alan; Lites, Bruce W.; Okamoto,
Takenori J.; Ichimoto, Kiyoshi; Katsukawa, Yukio; Magara, Tetsuya;
Suematsu, Yoshinori; Shimizu, Toshifumi
Bibcode: 2010ApJ...716.1288B
Altcode:
Hinode/Solar Optical Telescope (SOT) observations reveal two new
dynamic modes in quiescent solar prominences: large-scale (20-50 Mm)
"arches" or "bubbles" that "inflate" from below into prominences, and
smaller-scale (2-6 Mm) dark turbulent upflows. These novel dynamics are
related in that they are always dark in visible-light spectral bands,
they rise through the bright prominence emission with approximately
constant speeds, and the small-scale upflows are sometimes observed to
emanate from the top of the larger bubbles. Here we present detailed
kinematic measurements of the small-scale turbulent upflows seen in
several prominences in the SOT database. The dark upflows typically
initiate vertically from 5 to 10 Mm wide dark cavities between the
bottom of the prominence and the top of the chromospheric spicule
layer. Small perturbations on the order of 1 Mm or less in size
grow on the upper boundaries of cavities to generate plumes up to
4-6 Mm across at their largest widths. All plumes develop highly
turbulent profiles, including occasional Kelvin-Helmholtz vortex
"roll-up" of the leading edge. The flows typically rise 10-15 Mm before
decelerating to equilibrium. We measure the flowfield characteristics
with a manual tracing method and with the Nonlinear Affine Velocity
Estimator (NAVE) "optical flow" code to derive velocity, acceleration,
lifetime, and height data for several representative plumes. Maximum
initial speeds are in the range of 20-30 km s-1, which
is supersonic for a ~10,000 K plasma. The plumes decelerate in the
final few Mm of their trajectories resulting in mean ascent speeds
of 13-17 km s-1. Typical lifetimes range from 300 to 1000
s (~5-15 minutes). The area growth rate of the plumes (observed as
two-dimensional objects in the plane of the sky) is initially linear
and ranges from 20,000 to 30,000 km2 s-1 reaching
maximum projected areas from 2 to 15 Mm2. Maximum contrast of
the dark flows relative to the bright prominence plasma in SOT images
is negative and ranges from -10% for smaller flows to -50% for larger
flows. Passive scalar "cork movies" derived from NAVE measurements show
that prominence plasma is entrained by the upflows, helping to counter
the ubiquitous downflow streams in the prominence. Plume formation
shows no clear temporal periodicity. However, it is common to find
"active cavities" beneath prominences that can spawn many upflows in
succession before going dormant. The mean flow recurrence time in these
active locations is roughly 300-500 s (5-8 minutes). Locations remain
active on timescales of tens of minutes up to several hours. Using a
column density ratio measurement and reasonable assumptions on plume
and prominence geometries, we estimate that the mass density in the
dark cavities is at most 20% of the visible prominence density, implying
that a single large plume could supply up to 1% of the mass of a typical
quiescent prominence. We hypothesize that the plumes are generated from
a Rayleigh-Taylor instability taking place on the boundary between
the buoyant cavities and the overlying prominence. Characteristics,
such as plume size and frequency, may be modulated by the strength
and direction of the cavity magnetic field relative to the prominence
magnetic field. We conclude that buoyant plumes are a source of
quiescent prominence mass as well as a mechanism by which prominence
plasma is advected upward, countering constant gravitational drainage.
Title: Magnetic Field Topology and the Thermal Structure of the
Corona over Solar Active Regions
Authors: Schrijver, Carolus J.; DeRosa, M. L.; Title, A. M.
Bibcode: 2010AAS...21631201S
Altcode:
Solar extreme-ultraviolet images of active-region coronae are
characterized by ensembles of bright 1-2 MK loops that fan out from
select locations. We investigate the conditions associated with the
formation of these relatively cool loop fans within the otherwise
3-5 MK coronal environment by combining EUV observations of active
regions made with the Transition Region and Coronal Explorer (TRACE)
with global source-surface potential-field models based on the
full-sphere photospheric field from the assimilation of magnetograms
that are obtained by MDI on SOHO. We find that in the selected active
regions with largely potential field configurations these fans are
associated with (quasi-)separatrices within the strong-field regions
of magnetic plage and vice versa. We argue that the divergence of the
field lines across a (quasi-)separatrix may cause heating to happen
relatively low in the corona, resulting in a lower loop temperature
and flatter thermal profile of relatively dense (and thus EUV-bright)
loops that are surrounded by warmer, thermally more stratified loops
in field that does not straddle such topological divides.
Title: New Insights to Global Coronal EUV Waves: First Double
Quadrature Observations by SDO/AIA and STEREO/EUVI
Authors: Liu, Wei; Nitta, N. V.; Schrijver, C. J.; Title, A. M.
Bibcode: 2010AAS...21640230L
Altcode:
Global coronal EUV waves are useful diagnostic tools for physical
conditions on the Sun. Major drawbacks that hindered our understanding
of EUV waves were previous instruments' low cadence (e.g., 12
minutes for SoHO/EIT) and limited spatial resolution and wavelength
coverage. The Atmospheric Imaging Assembly (AIA) on board the recently
launched Solar Dynamics Observatory (SDO), joined by the STEREO EUV
Imager (EUVI), offers a great chance to end the decade long debate
on the nature of global EUV waves. AIA observes the corona at 10 EUV
and UV wavelengths, covering a wide range of temperatures. It has high
resolution (0.6") and cadence (20 s, 7 times faster than EUVI). These
capabilities allow us to study the thermal structure and kinematics
of EUV waves in unprecedented detail. We present here the first AIA
observations of an EUV wave occurring on 2010 April 8. AIA observed
this event on the solar disk, while the STEREO Ahead (A) and Behind
(B) spacecraft, which were 67 degree ahead and 72 degree behind the
Earth, respectively, provided side views of both the EUV wave and the
halo coronal mass ejection (seen by SoHO/LASCO) near the limb. This
formed a double quadrature configuration with great advantages to
infer the 3D structure. Initial analysis indicates that this wave
exhibited strong anisotropy, propagating primarily toward the south,
on the same side of the erupting loop system. We will examine its
spatial and temporal relationship with the erupting loop and CME and
discuss physical implications.
Title: Direct Imaging of an Emerging Flux Rope and a Resulting
Chromospheric Jet Observed by Hinode
Authors: Liu, Wei; Berger, T.; Title, A. M.; Tarbell, T. D.; DeRosa, M.
Bibcode: 2010AAS...21640307L
Altcode: 2010BAAS...41R.878L
Magnetic flux emergence has been traditionally observed on the disk by
identifying changes in magnetograms. Observations near the limb offer
an alternative perspective and allow direct imaging of emerging flux
ropes. We present Hinode/SOT Ca II H observations of such an event in
an equatorial coronal hole on 2007 February 9. The precursor of the
event was a bundle of fine material threads that extended at an oblique
angle above the chromosphere and appeared to rotate about a common
axis. This bundle first slowly and then rapidly swung up, accompanied
by a loop that appeared at the base of the bundle and expanded at
comparable rates. During the first (slow rise) stage, the apex of the
loop ascended at 16 km/s, a velocity similar to that of H-alpha arch
filaments (e.g., Chou & Zirin) and of emerging flux ropes expanding
into the corona as found in MHD simulations (e.g., Fan & Gibson;
Martinez-Sykora). The second stage started at the onset of a GOES A5
flare and the loop expansion accelerated, reaching a velocity of 130
km/s when the loop appeared to rupture near the peak of the flare. The
material bundle then swung back in a whiplike manner and developed into
a collimated jet, exhibiting oscillatory transverse motions across its
axis, as expected from unwinding twists. Some jet material fell back
along smooth streamlines, which bypass an unseen dome and presumably
a null point in the low corona, depicting an inverted-Y shape. Some
of these observations resemble the model (e.g., Uchida & Shibata)
of the emergence of a twisted flux rope into an open field region that
leads to reconnection and formation of a jet. Some observations are,
however, not predicted in previous models and we will discuss their
implications.
Title: AIA on SDO
Authors: Title, Alan M.
Bibcode: 2010AAS...21630803T
Altcode:
SDO is on orbit and AIA is operating well. Here the method for
obtaining detailed information about the instrument characteristics
and its calibration are given. Movies and data from the first solar
rotation will be presented.
Title: High resolution imaging and polarimetry with SUNRISE, a
balloon-borne stratospheric solar observatory
Authors: Barthol, Peter; Chares, Bernd; Deutsch, Werner; Feller, Alex;
Gandorfer, Achim; Grauf, Bianca; Hirzberger, Johann; Meller, Reinhard;
Riethmueller, Tino; Schuessler, Manfred; Solanki, Sami K.; Knoelker,
Michael; Martinez Pillet, Valentin; Schmidt, Wolfgang; Title, Alan
Bibcode: 2010cosp...38.4063B
Altcode: 2010cosp.meet.4063B
SUNRISE is an international collaboration for the development
and operation of a meter-class balloon-borne stratospheric solar
observatory. Prime science goal is the study of structure and dynamics
of the magnetic field in the solar atmosphere and the interaction of
the magnetic field with convective plasma flows. These processes are
studied by high resolution imaging in the UV and polarimetry at visible
wavelengths. The instrument has been successfully launched on June 8,
2009 from ESRANGE, Kiruna, Northern Sweden. During the more than 5
days flight about 1.5 TByte of scientific data were collected. The
paper gives an overview of the instrument and mission, examples of
the scientific output will also be presented. SUNRISE is a joint
project of the Max-Planck-Institut fuer Sonnensystemforschung (MPS),
Katlenburg-Lindau, with the Kiepenheuer-Institut fuer Sonnenphysik
(KIS), Freiburg, the High-Altitude Observatory (HAO), Boulder, the
Lockheed-Martin Solar and Astrophysics Lab. (LMSAL), Palo Alto, and
the Spanish IMaX consortium.
Title: The Ultraviolet Filter Imager (SuFI) onboard the Sunrise
balloon-borne solar observatory: Instrument description and first
results
Authors: Gandorfer, Achim; Barthol, Peter; Feller, Alex; Grauf,
Bianca; Hirzberger, Johann; Riethmueller, Tino; Solanki, Sami K.;
Berkefeld, Thomas; Knoelker, Michael; Martinez Pillet, Valentin;
Schmidt, Wolfgang; Title, Alan
Bibcode: 2010cosp...38.4064G
Altcode: 2010cosp.meet.4064G
We describe the design of the near UV filter imager SuFi onboard
Sunrise, which was successfully flown in the stratosphere in June
2009. During its five days flight SuFI captured the highest contrast
images of solar granulation ever. SuFI is a diffraction limited filter
imager with an effective focal length of 121m, working in 5 distinct
wavelength bands between 210nm and 397nm. It is based on a two mirror
modified Schwarzschild microscope, which is integral part of the central
Image stabilization and light Distribution unit (ISLiD) of Sunrise,
which acts as the reimaging optics between the 1m telescope and the
science instruments. The key technical features of the instrument are
presented under the view of the specific demands of balloon-borne
optical systems. First results obtained with the instrument are
presented to demonstrate the capabilities of the instrument.
Title: UV intensity distributions of the quiet Sun observed with
Sunrise
Authors: Hirzberger, Johann; Feller, A.; Riethmueller, T.; Borrero,
J. M.; Schüssler, M.; Barthol, P.; Berkefeld, T.; Gandorfer, A.;
Knoelker, M.; Martínez Pillet, V.; Schmidt, W.; Solanki, S.; Title, A.
Bibcode: 2010cosp...38.1735H
Altcode: 2010cosp.meet.1735H
High resolution solar images in the near UV have been obtained with
the Solar UV Filtergraph (SUFI) onboard the Sunrise balloon borne
observatory, amongst others in wavelength regions not accessible
from the ground. We present intensity distributions of the quiet
Sun at different heliocentric angles, from disk center to the solar
limb. These results, obtained in spectral windows at 214 nm, 313 nm
(OH band), 388 nm (CN band) and 396.7 nm (CaIIH), represent an important
validation of numerical models of the solar photosphere and are, thus,
fundamental ingredients for our understanding of the thermal processes
in the solar surface region.
Title: Relation between the Sunrise photospheric magnetic field and
the Ca II H bright features
Authors: Jafarzadeh, Shahin; Hirzberger, J.; Feller, A.; Lagg, A.;
Solanki, S. K.; Pietarila, A.; Danilovic, S.; Riethmueller, T.;
Barthol, P.; Berkefeld, T.; Gandorfer, A.; Knülker, M.; Martínez
Pillet, V.; Schmidt, W.; Schüssler, M.; Title, A.
Bibcode: 2010cosp...38.2856J
Altcode: 2010cosp.meet.2856J
Recent observations from the Sunrise balloon-borne solar telescope
have enabled us to reach an unprecedented high spatial resolution
on the solar surface with the near-ultraviolet photo-spheric and
chromospheric images as well as the magnetograms. We use these high
resolution observations to investigate the structure of the solar
upper photosphere and lower chromosphere as well as their temporal
evolutions. We study the relation between the inter-granular Ca II
397 nm bright structures in images obtained by the Sunrise Filter
Imager (SuFI) and their corresponding photospheric vector magnetic
field computed from the Imaging Magnetogram eXperiment (IMaX)
observations. The targets under study are in a quiet Sun region and
close to disc-centre.
Title: First Observation with AIA
Authors: Title, Alan
Bibcode: 2010cosp...38.2859T
Altcode: 2010cosp.meet.2859T
On February 11, 2010 at about 10:23 EST the Solar Dynamics Observatory
(SDO) Atlas 5 launched from the Kennedy Spacecraft Center in central
Florida. As this abstract is being written SDO is circling the Earth
in preparation for injection into its final geosynchronous orbit. The
current schedule plans the Atmospheric Imaging Assembly (AIA) instrument
doors will open in 37 days from launch. After a week of checking systems
and initial calibration initial observations will begin. During this
period several observing sequences will be tested to evaluate normal
and various special sequences. At COSPAR initial observations and
evaluation of initial sequences will be presented. Because AIA, HMI,
and EVE have open data policies the SDO mission represents a huge step
forward in the amount and quality of solar data available to the science
community. Significant international effort has gone into developing
tools for both visualizing and mining the SDO database. Both the data
and the data mining tools will be demonstrated.
Title: Imaging Michelson interferometers
Authors: Title, Alan M.
Bibcode: 2010ISSIR...9..327T
Altcode:
The imaging solid wide-field Michelson (SWFM) interferometer has
a performance superior to that of a wide-field birefringent element
because of its smaller angle sensitivity and its relative insensitivity
to temperature. For these reasons SWFM filter systems were chosen as
the imaging spectrometers for the Michelson Doppler Imager on SOHO
and for the Helioseismic and Magnetic Imager on the SDO. Theory and
practice in space are described for SWFM filters.
Title: Response of the Chromosphere to Penumbral Dynamics: Bow Shocks
and Microjets
Authors: Ryutova, M.; Berger, T.; Frank, Z.; Title, A.
Bibcode: 2009ASPC..415..373R
Altcode:
We have analyzed the data sets obtained with the SOT instrument
on Hinode during the disc passage of AR 10923 (November 10--20,
2006). Along with a limited number of jet-like features (Katsukawa
2007), we found other kinds of bright chromospheric transients
abundantly pervading the entire penumbra and drifting as a whole in
a direction perpendicular to their long axes. Quantitative analysis
based on our recent penumbral model (Ryutova et al. 2008a) shows that
they have all the signatures of bow shocks produced in the overlying
chromosphere by post-reconnection penumbral filaments.
Title: Sunspot Penumbrae: Formation and Fine Structure
Authors: Ryutova, M.; Berger, T.; Title, A.
Bibcode: 2009ASPC..415..361R
Altcode:
Sub-arcsecond observations revealing the fine sub-structure of
penumbral filaments and new properties of their dynamics, provide both
the basis and constraints for novel models of the penumbra. Even more
severe conditions are imposed on models by new data obtained with the
SOT instrument on Hinode, showing e.g. direct connection between the
dynamic changes in penumbra and appearance of bright transients in
the overlying chromosphere. We propose the mechanism that not only
explains the observed properties of individual filaments, but is part
of the physical process that determines formation of penumbra and its
impact on the overlying atmosphere.
Title: The Interface Region Imaging Spectrograph (IRIS) Small Explorer
Authors: de Pontieu, B.; Title, A. M.; Schryver, C. J.; Lemen, J. R.;
Golub, L.; Kankelborg, C. C.; Carlsson, M.
Bibcode: 2009AGUFMSH33B1499D
Altcode:
The Interface Region Imaging Spectrograph (IRIS) was recently selected
as a small explorer mission by NASA. The primary goal of IRIS is to
understand how the solar atmosphere is energized. The IRIS investigation
combines advanced numerical modeling with a high resolution 20 cm UV
imaging spectrograph that will obtain spectra covering temperatures
from 4,500 to 10 MK in three wavelength ranges (1332-1358 Angstrom,
1390-1406 Angstrom and 2785-2835 Angstrom) and simultaneous images
covering temperatures from 4,500 K to 65,000 K. IRIS will obtain UV
spectra and images with high resolution in space (1/3 arcsec) and time
(1s) focused on the chromosphere and transition region of the Sun, a
complex dynamic interface region between the photosphere and corona. In
this region, all but a few percent of the non-radiative energy leaving
the Sun is converted into heat and radiation. IRIS fills a crucial gap
in our ability to advance Sun-Earth connection studies by tracing the
flow of energy and plasma through this foundation of the corona and
heliosphere. The IRIS investigation is led by PI Alan Title (LMSAL)
with major participation by the Harvard Smithsonian Astrophysical
Observatory, Montana State University, NASA Ames Research Center,
Stanford University and the University of Oslo (Norway). IRIS is
scheduled for launch in late 2012, and will have a nominal two year
mission lifetime.
Title: An Intriguing Chromospheric Jet Observed by Hinode: Fine
Structure Kinematics and Evidence of Unwinding Twists
Authors: Liu, Wei; Berger, Thomas E.; Title, Alan M.; Tarbell,
Theodore D.
Bibcode: 2009ApJ...707L..37L
Altcode: 2009arXiv0910.5186L
We report a chromospheric jet lasting for more than 1 hr observed by
the Hinode Solar Optical Telescope in unprecedented detail. The ejection
occurred in three episodes separated by 12-14 minutes, with the amount
and velocity of material decreasing with time. The upward velocities
range from 438 to 33 km\nolimits s\nolimits ^{-1}, while the downward
velocities of the material falling back have smaller values (mean:
-56 km\nolimits s\nolimits ^{-1}) and a narrower distribution (standard
deviation: 14 km\nolimits s\nolimits ^{-1}). The average acceleration
inferred from parabolic spacetime tracks is 141 m\nolimits s^{-2}, a
fraction of the solar gravitational acceleration. The jet consists of
fine threads (0farcs5-2'' wide), which exhibit coherent, oscillatory
transverse motions perpendicular to the jet axis and about a common
equilibrium position. These motions propagate upward along the jet,
with the maximum phase speed of 744 ± 11 km\nolimits s\nolimits ^{-1}
at the leading front of the jet. The transverse oscillation velocities
range from 151 to 26 km\nolimits s\nolimits ^{-1}, amplitudes from
6.0 to 1.9 Mm\nolimits, and periods from 250 to 536 s\nolimits. The
oscillations slow down with time and cease when the material starts to
fall back. The falling material travels along almost straight lines in
the original direction of ascent, showing no transverse motions. These
observations are consistent with the scenario that the jet involves
untwisting helical threads, which rotate about the axis of a single
large cylinder and shed magnetic helicity into the upper atmosphere.
Title: Is Flux Submergence an Essential Aspect of Flux Emergence?
Authors: Lites, B. W.; Frank, Z.; Shine, R. A.; Title, A. M.;
Ichimoto, K.
Bibcode: 2009ASPC..415..172L
Altcode:
High resolution Hinode Spectro-Polarimeter observations permit one
to examine the detailed structure of the magnetic field vector in
emerging flux regions. We find the field to have a concave-upward
geometry on the smallest scales observed (0.3 arcsec), indicating the
presence of U-loops at the sites of approaching and canceling opposite
polarities. This structure suggests that reconnection is taking place
at or below the surface, allowing the emerging flux to rid itself of
its considerable mass burden. Supersonic down flows are often observed
adjacent to, but not coincident with, the sites of canceling flux. We
propose that these are the sites that drain the mass contained in the
buoyantly-rising flux elements. The observations then suggest a process
of sub-surface reconnection producing O-loops that then are forced to
descend with the intergranular convective down flows, thus making flux
submergence important to the larger scale flux emergence process.
Title: Using SiC for Lightweight EUV Space Optics
Authors: Martinez-Galarce, Dennis S.; Boerner, P.; De Pontieu, B.;
Katz, N.; Title, A.; Soufli, R.; Robinson, J. C.; Baker, S. L.;
Gullikson, E. M.
Bibcode: 2009SPD....41.1813M
Altcode:
SiC technology is fast becoming a material of choice for space
systems. Herein, we present a novel design for an EUV telescope made
entirely of SiC - optics and metering structure inclusive - called the
High-resolution Lightweight Telescope for the EUV (HiLiTE). HiLiTE is a
Cassegrain telescope with multilayer coated SiC optics tuned to operate
at 465 Å, and will image Ne VII emission formed in solar transition
region plasma at 500,000 K. HiLiTE will have an aperture of 30 cm,
angular resolution of 0.2 arc seconds and operate at a cadence of 5
seconds or less, having a mass that is about ¼ that of one of the
20 cm aperture telescopes on the Atmospheric Imaging Assembly (AIA)
instrument aboard NASA's Solar Dynamics Observatory (SDO). This new
instrument technology thus serves as a path finder to a post-AIA,
Explorer-class mission.
Title: Helical Shape and Twisting Motion as Intrinsic Properties of
Penumbral Filaments
Authors: Shine, R. A.; Ryutova, M.; Berger, T. E.; Title, A. M.;
Tarbell, T. D.; Ichimoto, K.
Bibcode: 2009AGUFMSH23B1541S
Altcode:
A wealth of high resolution data obtained with advanced ground based
telescopes and the SOT instrument on HINODE have led to new findings
in the properties of penumbral filaments and controversies in their
interpretation. Here we address one such issue, namely the question of
whether the apparent twist of filaments is real or is just a viewing
effect. We show that the helical shape and twisting motions of penumbral
filaments follow from first principles and represent an integral part of
penumbra formation and dynamics. As such, these properties link together
other observed features of filaments including their magnetic and
thermal substructure and their impact on the overlying atmosphere. At
all stages of penumbral dynamics, qualitative agreement of theory and
observations is supported by quantitative analysis as well.
Title: Role of the Resistive and Thermal Instabilities in Dynamics
of Quiescent Prominences
Authors: Frank, Z.; Ryutova, M.; Berger, T. E.; Title, A. M.; Tarbell,
T. D.
Bibcode: 2009AGUFMSH41B1653F
Altcode:
We present the observations taken with the SOT instrument on Hinode in
G-band and Ca H lines. High cadence data compiled in movies show clear
evidence for several fundamental plasma instabilities. We combine
the observational evidence and theoretical estimates to identify
these instabilities. The following can be given as examples. (1)
An analogue of the Kelvin-Helmholtz instability develops at the
prominence/corona interface that manifests itself in growing ripples
during a linear growth phase and may be followed by a nonlinear stage
taking the form of an explosive instability corresponding to a CME
ejection. This instability also includes the regime of "smoke ring"
formation. (2) The appearence of "bubbles and spikes" typical to
the Rayleigh-Taylor instability are observed. Their evolution and
growth rates are found to be modified by both poloidal and toroidal
components of magnetic field. (3) A resistive interchange instability,
associated with an "unfavorable" magnetic field curvature relative to
the density/temperature gradients, may be responsible for a hot barb
formation, its evolution and collapse.
Title: Radiative MHD simulation of an Emerging Flux Region
Authors: Cheung, C.; Rempel, M.; Title, A. M.; Schuessler, M.
Bibcode: 2009AGUFMSH51A1267C
Altcode:
We present a radiation magnetohydrodynamics (MHD) simulation of
the birth of an active region. The simulation models the rise
of a magnetic flux bundle from the convection zone into the solar
photosphere. Observational properties of the simulation are consistent
with recent, high-cadence and high spatial resolution observations of
emerging flux regions taken by Hinode/SOT. Observational properties
common to both simulation and observation include the hierarchical
formation of progressively larger photospheric magnetic structures,
the formation and disappearance of light bridges, umbral dots as well
as penumbral filaments.
Title: Fine Structures and Kinematics of an Intriguing Chromospheric
Jet Observed by Hinode Solar Optical Telescope
Authors: Liu, W.; Berger, T. E.; Title, A. M.; Tarbell, T. D.
Bibcode: 2009AGUFMSH51A1266L
Altcode:
Transient, small-scale ejections of plasma from the lower atmosphere
are common manifestations of solar activity. Hinode, with its superior
resolutions, has spurred renewed interest in solar jets since its
launch. Here we report a chromospheric jet lasting for more than 1
hr on 2007 February 9 observed by the Hinode Solar Optical Telescope
(SOT) in unprecedented detail. SOT Ca II H passband observations
at high resolution of 0.2 arcsecond and cadence of 8 s allowed us to
investigate the fine structures and kinematics of the jet. The ejection
occurred in three episodes, rather than continuously, with the amount
and velocity of material decreasing with time. The upward velocities
along the jet range from ~440 to ~30 km/s, while the downward velocities
of the material falling back have much smaller values (mean: -60 km/s)
and a narrower distribution. Some tracks in the space-time plot clearly
show parabolic shapes and the inferred acceleration is a fraction of
the solar gravitational acceleration. The jet consists of fine threads
(0.5-2 arcsecond wide), which exhibit coherent, oscillatory transverse
motions perpendicular to the jet axis and about a common equilibrium
position. These motions propagate upward, with the maximum phase speed
of ~740 km/s found at the leading front of the jet. The transverse
oscillation velocities range from 150 to 30 km/s, amplitudes from 6 to 2
Mm, and periods from 250 to 550 s. The oscillations slow down with time
and cease when the material starts to fall back. The falling material
travels along almost straight lines in the original direction of ascent,
showing no transverse motions. These observations are consistent with
the models suggested by Shibata & Uchida (1985) and Canfield et
al. (1996). In this scenario, the jet involves untwisting helical
threads, which rotate about the axis of a single large cylinder and
shed magnetic helicity into the upper atmosphere. Implications of this
event in the context of multiwavelength data in H-alpha, EUV, and X-rays
will be discussed. A chromospheric jet observed by Hinode SOT in the
Ca II H passband (T=1-2×10 4 K). Note the helical-like fine threads.
Title: Solar Surface Emerging Flux Regions: A Comparative Study of
Radiative MHD Modeling and Hinode SOT Observations
Authors: Cheung, M.; Schüssler, M.; Tarbell, T. D.; Title, A. M.
Bibcode: 2009ASPC..415...79C
Altcode:
We present results from three-dimensional radiative MHD simulations
of the rise of buoyant magnetic flux tubes through the convection
zone and into the photosphere. Due to the strong stratification
of the convection zone, the rise results in a lateral expansion
of the tube into a magnetic sheet, which acts as a reservoir for
small-scale flux emergence events at the scale of granulation. The
interaction of the convective downflows and the rising magnetic flux
tube undulates it to form serpentine field lines that emerge into the
photosphere. Observational characteristics of the simulated emerging
flux regions are discussed in the context of new observations from
Hinode SOT.
Title: Origin of Filamentary Structures and Flows in Quiescent
Prominences
Authors: Ryutova, M.; Berger, T. E.; Tarbell, T. D.; Frank, Z.; Title,
A. M.
Bibcode: 2009AGUFMSH23B1540R
Altcode:
The paradox of fine vertical structure has usually referred to an
apparent contradiction met when comparing vertical fine structures
of quiescent prominences observed on the limb with the necessary
horizontal magnetic field along their long axis. In addition to this
fundamental problem, the very formation of fine vertical structures
has been a long standing puzzle. Here we address these problems and
show that considering the global structure of a prominence as a large
scale skewed formation with toroidal and poloidal fields removes the
paradox and allows derivation of dynamic stability criteria. This also
includes the mechanism of the fine structure formation and peculiarities
of downward mass motions. Theoretical estimates of key parameters
are compared with the observations taken with the SOT instrument
on Hinode. We find results of comparison very encouraging. For the
approximate 3D reconstruction of the general shape of prominences,
the STEREO A and B images have been used.
Title: A New View of Fine Scale Dynamics and Magnetism of Sunspots
Revealed by Hinode/SOT
Authors: Ichimoto, K.; Suematsu, Y.; Katsukawa, Y.; Tsuneta, S.;
Shimojo, M.; Shimizu, T.; Shine, R. A.; Tarbell, T. D.; Berger, T.;
Title, A. M.; Lites, B. W.; Kubo, M.; Yokoyama, T.; Nagata, S.
Bibcode: 2009ASPC..405..167I
Altcode:
The Solar Optical Telescope on-board Hinode is providing a new view of
the fine scale dynamics in sunspots with its high spatial resolution and
unprecedented image stability. We present three features related to the
Evershed flow each of which raises a new puzzle in sunspot dynamics;
i.e., twisting appearance of penumbral filaments, the source and sink
of individual Evershed flow channels, and the net circular polarization
in penumbrae with its spatial relation to the Evershed flow channels.
Title: Has Hinode Revealed the Missing Turbulent Flux of the
Quiet Sun?
Authors: Lites, B. W.; Kubo, M.; Socas-Navarro, H.; Berger, T.; Frank,
Z.; Shine, R.; Tarbell, T.; Title, A. M.; Ichimoto, K.; Katsukawa,
Y.; Tsuneta, S.; Suematsu, Y.; Shimizu, T.; Nagata, S.
Bibcode: 2009ASPC..405..173L
Altcode:
The Hinode Spectro-Polarimeter has revealed the presence of surprisingly
strong horizontal magnetic fields nearly everywhere in the quiet
solar atmosphere. These horizontal fields, along with measures of the
vertical fields, may be the signature of the ``hidden turbulent flux''
of the quiet Sun. The measured horizontal fields average at least to
55 Gauss: nearly 5 times that of the measured longitudinal apparent
flux density. The nature of these fields are reviewed, and discussed
in the light of recent magneto-convection numerical simulations of
the quiet Sun.
Title: The AIA for SDO: Plans for Flight Operations
Authors: Lemen, James; Title, A. M.; Schrijver, K.; Boerner, P.;
Wolfson, C. J.; Nightingale, R.
Bibcode: 2009SPD....40.1703L
Altcode:
The Atmospheric Imaging Array (AIA) has been integrated to the NASA
Solar Dynamics Observatory for over a year and is being prepared for
launch in the fourth quarter of 2009. AIA will provide unprecedented
full-disk images of the solar corona simultaneously covering a
wide range of temperatures. Four normal incidence telescopes with
multilayer-coated optics obtain images with 0.6 arcsec pixels of
EUV-emitting iron lines (covering temperatures between 0.6 and 15 x
106 K), He II 304Å, and C IV in broadband UV. In normal
operations, AIA acquires eight 4k x 4k pixel images every 10s that are
compressed for transmission to the ground, and require approximately
1 TByte of ground storage per day if compressed by a factor of 2. The
instrument calibration has been completed and comprehensive performance
predictions are available (see Wolfson et al). The observing program is
configurable by tables that can be uploaded from the ground. AIA data
is processed to Level 1 in the JSOC pipeline and made available for
export to scientific users. Additional data products, such as movies
of active regions, light curves, and DEM maps, have been developed
for distribution. We present an update of the predicted instrument
performance, discuss the concept of operations, and describe the data
processing for Level 1 data products. Exported FITs data files conform
to SolarSoft standards and the data flow design enables a seamless
connection to the Heliosphysics Event Knowledgebase (see Hurlburt
et al).
Title: Pre-flight Calibration Of The AIA Instrument On SDO
Authors: Wolfson, C. Jacob; Boerner, P.; Soufli, R.; Podgorski, W.;
Title, A.; Lemen, J.; Rausch, A.; Shing, L.; Stern, R.; McKenzie,
D.; Testa, P.; Weber, M.
Bibcode: 2009SPD....40.1704W
Altcode:
The Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics
Observatory (SDO) is a set of four reflecting telescopes designed to
acquire high-resolution images of the solar atmosphere in a variety of
extreme ultraviolet, ultraviolet and visible-light wavelength bands
(see Lemen et al.). AIA takes images in ten wavelength channels,
whose bandpasses are determined by the collecting area dedicated to
each channel and the efficiency of the mirror coatings, filters, and
detector. We describe the measurements of each of these components,
and present the resulting effective area as functions of wavelength. The
measured effective area functions will be cross-calibrated on orbit by
comparing full-disk integrated fluxes from each of the AIA channels
with the calibrated irradiance measurements from the EUV Variability
Experiment (EVE) on SDO. The AIA effective areas are used to calculate
temperature response functions and expected count rates in each channel
for observations of various solar features.
Title: The AIA for SDO
Authors: Title, Alan M.
Bibcode: 2009SPD....40.1702T
Altcode:
This fall will see the launch of the Solar Dynamics Observatory
(SDO). The Atmospheric Imaging Assembly (AIA) will be one of the
three instruments on the spacecraft. AIA can obtain full disk 4096x
4096 pixel images of the Sun in 10 wavelength bands with its four
telescopes. In normal operations the system will obtain 8 images every
10 seconds. During the initial phases of operation we will determine
the best image sequence for the prevailing solar conditions. Our plan
is to remain in that mode for many weeks at a time. However, during
the eclipse season we do plan to do some special experiments. SDO is an
open science mission; however, the amount of data generated is several
terabytes per day. This means that some planning by the mission and
the community is required for efficient data distribution. The plan is
to quickly produce a range of quick look products to allow selection of
events and an efficient mechanism for delivering the science data. Talks
in this session will address the data selection tools.
Title: Prominence Formation Associated with an Emerging Helical
Flux Rope
Authors: Okamoto, Takenori J.; Tsuneta, Saku; Lites, Bruce W.; Kubo,
Masahito; Yokoyama, Takaaki; Berger, Thomas E.; Ichimoto, Kiyoshi;
Katsukawa, Yukio; Nagata, Shin'ichi; Shibata, Kazunari; Shimizu,
Toshifumi; Shine, Richard A.; Suematsu, Yoshinori; Tarbell, Theodore
D.; Title, Alan M.
Bibcode: 2009ApJ...697..913O
Altcode: 2009arXiv0904.0007O
The formation and evolution process and magnetic configuration of
solar prominences remain unclear. In order to study the formation
process of prominences, we examine continuous observations of a
prominence in NOAA AR 10953 with the Solar Optical Telescope on
the Hinode satellite. As reported in our previous Letter, we find
a signature suggesting that a helical flux rope emerges from below
the photosphere under a pre-existing prominence. Here we investigate
more detailed properties and photospheric indications of the emerging
helical flux rope, and discuss their relationship to the formation of
the prominence. Our main conclusions are: (1) a dark region with absence
of strong vertical magnetic fields broadens and then narrows in Ca II
H-line filtergrams. This phenomenon is consistent with the emergence
of the helical flux rope as photospheric counterparts. The size of the
flux rope is roughly 30,000 km long and 10,000 km wide. The width is
larger than that of the prominence. (2) No shear motion or converging
flows are detected, but we find diverging flows such as mesogranules
along the polarity inversion line. The presence of mesogranules may
be related to the emergence of the helical flux rope. (3) The emerging
helical flux rope reconnects with magnetic fields of the pre-existing
prominence to stabilize the prominence for the next several days. We
thus conjecture that prominence coronal magnetic fields emerge in
the form of helical flux ropes that contribute to the formation and
maintenance of the prominence.
Title: The Magnetic Landscape of the Sun's Polar Region
Authors: Tsuneta, S.; Ichimoto, K.; Katsukawa, Y.; Lites, B. W.;
Matsuzaki, K.; Nagata, S.; Orozco Suárez, D.; Shimizu, T.; Shimojo,
M.; Shine, R. A.; Suematsu, Y.; Suzuki, T. K.; Tarbell, T. D.; Title,
A. M.
Bibcode: 2008ApJ...688.1374T
Altcode: 2008arXiv0807.4631T
We present observations of the magnetic landscape of the polar region
of the Sun that are unprecedented in terms of spatial resolution,
field of view, and polarimetric precision. They were carried out with
the Solar Optical Telescope aboard Hinode. Using a Milne-Eddington
inversion, we find many vertically oriented magnetic flux tubes
with field strengths as strong as 1 kG scattered in latitude between
70° and 90°. They all have the same polarity, consistent with the
global polarity of the polar region. The field vectors are observed to
diverge from the centers of the flux elements, consistent with a view
of magnetic fields that are expanding and fanning out with height. The
polar region is also found to have ubiquitous horizontal fields. The
polar regions are the source of the fast solar wind, which is channeled
along unipolar coronal magnetic fields whose photospheric source is
evidently rooted in the strong-field, vertical patches of flux. We
conjecture that vertical flux tubes with large expansion around the
photospheric-coronal boundary serve as efficient chimneys for Alfvén
waves that accelerate the solar wind.
Title: Solar Surface Emerging Flux Regions: A Comparative Study of
Radiative MHD Modeling and Hinode SOT Observations
Authors: Cheung, M. C. M.; Schüssler, M.; Tarbell, T. D.; Title, A. M.
Bibcode: 2008ApJ...687.1373C
Altcode: 2008arXiv0810.5723C
We present results from numerical modeling of emerging flux regions
on the solar surface. The modeling was carried out by means of
three-dimensional (3D) radiative MHD simulations of the rise of
buoyant magnetic flux tubes through the convection zone and into the
photosphere. Due to the strong stratification of the convection zone,
the rise results in a lateral expansion of the tube into a magnetic
sheet, which acts as a reservoir for small-scale flux emergence
events at the scale of granulation. The interaction of the convective
downflows and the rising magnetic flux tube undulates it to form
serpentine field lines that emerge into the photosphere. Observational
characteristics, including the pattern of the emerging flux regions,
the cancellation of surface flux and associated high-speed downflows,
the convective collapse of photospheric flux tubes, the appearance
of anomalous darkenings, the formation of bright points, and the
possible existence of transient kilogauss horizontal fields are
discussed in the context of new observations from the Hinode Solar
Optical Telescope. Implications for the local helioseismology of
emerging flux regions are also discussed.
Title: On the Penumbral Jetlike Features and Chromospheric Bow Shocks
Authors: Ryutova, M.; Berger, T.; Frank, Z.; Title, A.
Bibcode: 2008ApJ...686.1404R
Altcode:
We present observations of sunspot penumbrae obtained during the disk
passage of AR 10923 (2006 November 10-20) with the SOT instrument on
Hinode in 4305 Å G band and Ca II λ3968 H line. Along with recently
discovered jetlike features (Katsukawa et al. 2007), we find other
kinds of bright elongated transients abundantly pervading the entire
penumbra and drifting as a whole in a direction almost perpendicular
to their long axes. Their measured velocities strongly depend
on their orientation with respect to the line of sight and range
from simeq1 to simeq20 km s-1. We present quantitative
analysis of these features and interpret them relative to our recent
penumbral model (Ryutova et al. 2008) to show that they are produced
by shocks resulting from a slingshot effect associated with the ongoing
reconnection processes in neighboring penumbral filaments. Due to sharp
stratification of the low atmosphere, postreconnection flux tubes moving
upward quickly accelerate. At transonic velocities a bow (detached)
shock is formed in front of the flux tube, as usually occurs in cases
of blunt bodies moving with supersonic velocities. Observed parameters
of transients are in good agreement with calculated parameters of
bow shocks. On some, much more rare occasions compared to "drifting"
bow-shock-type transients, there appear compact bright transients
moving in the radial direction, along their long axis, and having
velocities of 20-50 km s-1. We relate these features to a
category of true microjets.
Title: Magnetic Fields of the Quiet Sun: A New Quantitative
Perspective From Hinode
Authors: Lites, B. W.; Kubo, M.; Socas-Navarro, H.; Berger, T.; Frank,
Z.; Shine, R.; Tarbell, T.; Title, A.; Ichimoto, K.; Katsukawa, Y.;
Tsuneta, S.; Suematsu, Y.; Shimizu, T.; Nagata, S.
Bibcode: 2008ASPC..397...17L
Altcode:
This article summarizes results of studies presented in two papers
already published: Lites et al. (2007a); Lites et al. (2007b). Please
see these for further details.
Title: Evolution of Magnetic Fields at the Boundary of the Penumbra
Authors: Kubo, M.; Ichimoto, K.; Shimizu, T.; Lites, B. W.; Tsuneta,
S.; Suematsu, Y.; Katsukawa, Y.; Nagata, S.; Tarbell, T.; Shine,
R. A.; Title, A. M.
Bibcode: 2008ASPC..397...79K
Altcode:
The formation of moving magnetic features (MMFs) separating from the
penumbra were successfully observed with the Solar Optical Telescope
(SOT) aboard the Hinode satellite. We find that bright features in
the outer penumbra are located at the penumbral spines, which have
magnetic fields more vertical than the surroundings, or located at the
MMFs separating from the spines. This suggests that convection in the
outer penumbra is related to the disintegration of the sunspot.
Title: Erratum: The Analysis of Penumbral Fine Structure Using an
Advanced Inversion Technique
Authors: Jurcák, Jan; Bellot Rubio, Luis; Ichimoto, Kiyoshi;
Katsukawa, Yukio; Lites, Bruce; Nagata, Shin'ichi; Shimizu, Toshifumi;
Suematsu, Yoshinori; Tarbell, Theodore D.; Title, Alan M.; Tsuneta,
Saku
Bibcode: 2008PASJ...60..933J
Altcode:
In the article [PASJ 59, S601-S606 (2007)], the word ''CSIC'' was
omitted from the affiliation of Dr. Luis Bellot Rubio. The correct
affiliation is : 2Instituto de Astrofísica de Andalucía
(CSIC), Apdo. de Correos 3004, 18080 Granada, Spain
Title: SUNRISE: High resolution UV/VIS observations of the sun from
the stratosphere
Authors: Sunrise Team; Barthol, P.; Gandorfer, A. M.; Solanki,
S. K.; Knölker, M.; Martinez Pillet, V.; Schmidt, W.; Title, A. M.;
SUNRISE Team
Bibcode: 2008AdSpR..42...70S
Altcode:
SUNRISE is an international project for the development, construction
and operation of a balloon-borne solar telescope with an aperture
of 1 m, working in the UV/VIS spectral domain. The main scientific
goal of SUNRISE is to understand the structure and dynamics of the
magnetic field in the atmosphere of the Sun. SUNRISE will provide
near diffraction-limited images of the photosphere and chromosphere
with an unprecedented resolution down to 35 km on the solar surface
at wavelengths around 220 nm. Active in-flight alignment and image
stabilization techniques are used. The focal-plane instrumentation
consists of a polarization sensitive spectrograph, a Fabry Perot
filter magnetograph and a phase-diverse filter imager working in
the near UV. The first stratospheric long-duration balloon flight
of SUNRISE is planned in summer 2009 from the Swedish ESRANGE
station. SUNRISE is a joint project of the German Max-Planck-Institut
für Sonnensystemforschung (MPS), Katlenburg-Lindau, with the
Kiepenheuer-Institut für Sonnenphysik (KIS), Freiburg, Germany, the
High-Altitude Observatory (HAO), Boulder, USA, the Lockheed-Martin
Solar and Astrophysics Laboratory (LMSAL), Palo Alto, USA, and the
Spanish IMaX consortium. This paper will give an overview about the
mission and a description of its scientific and technological aspects.
Title: Disintegration of Magnetic Flux in Decaying Sunspots as
Observed with the Hinode SOT
Authors: Kubo, M.; Lites, B. W.; Ichimoto, K.; Shimizu, T.; Suematsu,
Y.; Katsukawa, Y.; Tarbell, T. D.; Shine, R. A.; Title, A. M.; Nagata,
S.; Tsuneta, S.
Bibcode: 2008ApJ...681.1677K
Altcode: 2008arXiv0806.0415K
Continuous observations of sunspot penumbrae with the Solar Optical
Telescope aboard Hinode clearly show that the outer boundary of the
penumbra fluctuates around its averaged position. The penumbral outer
boundary moves inward when granules appear in the outer penumbra. We
discover that such granules appear one after another while moving
magnetic features (MMFs) are separating from the penumbral "spines"
(penumbral features that have fields that are stronger and more vertical
than those of their surroundings). These granules that appear in the
outer penumbra often merge with bright features inside the penumbra
that move with the spines as they elongate toward the moat region. This
suggests that convective motions around the penumbral outer boundary are
related to the disintegration of magnetic flux in the sunspot. We also
find that dark penumbral filaments frequently elongate into the moat
region in the vicinity of MMFs that detach from penumbral spines. Such
elongating dark penumbral filaments correspond to nearly horizontal
fields extending from the penumbra. Pairs of MMFs with positive and
negative polarities are sometimes observed along the elongating dark
penumbral filaments. This strongly supports the notion that such
elongating dark penumbral filaments have magnetic fields with a "sea
serpent"-like structure. Evershed flows, which are associated with the
penumbral horizontal fields, may be related to the detachment of the
MMFs from the penumbral spines, as well as to the formation of the MMFs
along the dark penumbral filaments that elongate into the moat region.
Title: The high-resolution lightweight telescope for the EUV (HiLiTE)
Authors: Martínez-Galarce, Dennis S.; Boerner, Paul; Soufli, Regina;
De Pontieu, Bart; Katz, Noah; Title, Alan; Gullikson, Eric M.;
Robinson, Jeff C.; Baker, Sherry L.
Bibcode: 2008SPIE.7011E..3KM
Altcode: 2008SPIE.7011E.105M
The High-resolution Lightweight Telescope for the EUV (HiLiTE) is
a Cassegrain telescope that will be made entirely of Silicon Carbide
(SiC), optical substrates and metering structure alike. Using multilayer
coatings, this instrument will be tuned to operate at the 465 Å Ne VII
emission line, formed in solar transition region plasma at ~500,000
K. HiLiTE will have an aperture of 30 cm, angular resolution of ~0.2
arc seconds and operate at a cadence of ~5 seconds or less, having a
mass that is about 1/4 that of one of the 20 cm aperture telescopes on
the Atmospheric Imaging Assembly (AIA) instrument aboard NASA's Solar
Dynamics Observatory (SDO). This new instrument technology thus serves
as a path finder to a post-AIA, Explorer-class missions.
Title: Polarization Calibration of the Solar Optical Telescope
onboard Hinode
Authors: Ichimoto, K.; Lites, B.; Elmore, D.; Suematsu, Y.; Tsuneta,
S.; Katsukawa, Y.; Shimizu, T.; Shine, R.; Tarbell, T.; Title, A.;
Kiyohara, J.; Shinoda, K.; Card, G.; Lecinski, A.; Streander, K.;
Nakagiri, M.; Miyashita, M.; Noguchi, M.; Hoffmann, C.; Cruz, T.
Bibcode: 2008SoPh..249..233I
Altcode: 2008SoPh..tmp...69I
The Solar Optical Telescope (SOT) onboard Hinode aims to obtain vector
magnetic fields on the Sun through precise spectropolarimetry of
solar spectral lines with a spatial resolution of 0.2 - 0.3 arcsec. A
photometric accuracy of 10−3 is achieved and, after the
polarization calibration, any artificial polarization from crosstalk
among Stokes parameters is required to be suppressed below the level
of the statistical noise over the SOT's field of view. This goal was
achieved by the highly optimized design of the SOT as a polarimeter,
extensive analyses and testing of optical elements, and an end-to-end
calibration test of the entire system. In this paper we review both
the approach adopted to realize the high-precision polarimeter of the
SOT and its final polarization characteristics.
Title: The Solar Optical Telescope for the Hinode Mission: An Overview
Authors: Tsuneta, S.; Ichimoto, K.; Katsukawa, Y.; Nagata, S.; Otsubo,
M.; Shimizu, T.; Suematsu, Y.; Nakagiri, M.; Noguchi, M.; Tarbell,
T.; Title, A.; Shine, R.; Rosenberg, W.; Hoffmann, C.; Jurcevich,
B.; Kushner, G.; Levay, M.; Lites, B.; Elmore, D.; Matsushita, T.;
Kawaguchi, N.; Saito, H.; Mikami, I.; Hill, L. D.; Owens, J. K.
Bibcode: 2008SoPh..249..167T
Altcode: 2008SoPh..tmp...74T; 2007arXiv0711.1715T
The Solar Optical Telescope (SOT) aboard the Hinode satellite
(formerly called Solar-B) consists of the Optical Telescope Assembly
(OTA) and the Focal Plane Package (FPP). The OTA is a 50-cm
diffraction-limited Gregorian telescope, and the FPP includes the
narrowband filtergraph (NFI) and the broadband filtergraph (BFI), plus
the Stokes Spectro-Polarimeter (SP). The SOT provides unprecedented
high-resolution photometric and vector magnetic images of the
photosphere and chromosphere with a very stable point spread function
and is equipped with an image-stabilization system with performance
better than 0.01 arcsec rms. Together with the other two instruments
on Hinode (the X-Ray Telescope (XRT) and the EUV Imaging Spectrometer
(EIS)), the SOT is poised to address many fundamental questions about
solar magnetohydrodynamics. This paper provides an overview; the
details of the instrument are presented in a series of companion papers.
Title: Cooperative Observation of Ellerman Bombs between the Solar
Optical Telescope aboard Hinode and Hida/Domeless Solar Telescope
Authors: Matsumoto, Takuma; Kitai, Reizaburo; Shibata, Kazunari;
Nagata, Shin'ichi; Otsuji, Kenichi; Nakamura, Tahei; Watanabe, Hiroko;
Tsuneta, Saku; Suematsu, Yoshinori; Ichimoto, Kiyoshi; Shimizu,
Toshifumi; Katsukawa, Yukio; Tarbell, Theodore D.; Lites, Bruce W.;
Shine, Richard A.; Title, Alan M.
Bibcode: 2008PASJ...60..577M
Altcode:
High-resolution CaIIH broad-band filter images of NOAA10933 on 2007
January 5 were obtained by the Solar Optical Telescope aboard the Hinode
satellite. Many small-scale (∼1") bright points were observed outside
the sunspot and inside the emerging flux region. We identified some of
these bright points with Ellerman bombs (EBs) by using Hα images taken
by the Domeless Solar Telescope at Hida observatory. The sub-arcsec
structures of two EBs seen in CaIIH were studied in detail. Our
observation showed the following two aspects: (1) The CaIIH bright
points identified with EBs were associated with the bipolar magnetic
field structures, as reported by previous studies. (2)The structure
of the CaIIH bright points turned out to consist of the following two
parts: a central elongated bright core (0.7" × 0.5") located along
the magnetic neutral line and a diffuse halo (1.2"×1.8").
Title: Emergence of a helical flux rope and prominence formation
Authors: Okamoto, T. J.; Tsuneta, S.; Lites, B. W.; Kubo, M.; Yokoyama,
T.; Berger, T. E.; Ichimoto, K.; Katsukawa, Y.; Nagata, S.; Shibata,
K.; Shimizu, T.; Shine, R. A.; Suematsu, Y.; Tarbell, T. D.; Title,
A. M.
Bibcode: 2008AGUSMSP43B..06O
Altcode:
We report a discovery about emergence of a helical flux rope. The
episode may be related to the formation and evolution of an active
region prominence. Statistical studies by previous authors indicate that
numerous prominences have the inverse-polarity configuration suggesting
the helical magnetic configurations. There are two theoretical
models about formation of such a coronal helical magnetic field in
association with prominences: flux rope model and sheared-arcade
model. We have so far no clear observational evidence to support
either model. In order to find a clue about the formation of the
prominence, we had continuous observations of NOAA AR 10953 with the
SOT during 2007 April 28 to May 9. A prominence was located over the
polarity inversion line in the south-east of the main sunspot. These
observations provided us with a time series of vector magnetic fields
on the photosphere under the prominence. We found four new features:
(1) The abutting opposite-polarity regions on the two sides along
the polarity inversion line first grew laterally in size and then
narrowed. (2) These abutting regions contained vertically-weak,
but horizontally-strong magnetic fields. (3) The orientations of
the horizontal magnetic fields along the polarity inversion line on
the photosphere gradually changed with time from a normal- polarity
configuration to an inverse-polarity one. (4) The horizontal-magnetic
field region was blueshifted. These indicate that helical flux rope
emerges from below the photosphere into the corona along the polarity
inversion line under the prominence. We suggest that this supply of a
helical magnetic flux possibly into the corona is related to formation
and maintenance of active-region prominences.
Title: Evershed Flows as an Integral Part of Penumbral Formation
and its Fine Structure
Authors: Ryutova, M.; Berger, T.; Lites, B.; Title, A.; Frank, Z.
Bibcode: 2008AGUSMSP41B..07R
Altcode:
Observations of Evershed flows with the Solar Optical Telescope (SOT)
on Hinode (Ichimito, Shine, Lites, et al. 2008, PASJ, 59, S593) showed
that penumbral flows have small scale structures and much more complex
properties than those of a simple outflow of material with unique
direction and appearence. We address this problem and show that the
flow properties are directly connected to the observed properties of
penumbral filaments and are an integral part of penumbral development
during sunspot formation. In our recent model (Ryutova, Berger, &
Title, 2008, ApJ, 676, April), based on the observations that sunspot
has a filamentary structure and consists of a dense conglomerate of
non-collinear interlaced flux tubes, the penumbra is formed due to
an on-going reconnection processes that leads to branching out of the
peripheral flux tubes from the "trunk". As flux tubes have different
parameters, branching occurs at different heights and with different
inclinations, thus forming an "uncombed" penumbra. Each elemental act
of reconnection generates an inevitable twist in the post-reconnection
filaments that acquire a screw pinch configuration. This explains
the remarkable dynamic stability of penumbral filaments and their
observed properties, such as presence of dark cores, wrapping and
spinning of filaments around each other, bright footpoints, etc. Here
we show that propagation of twist along current carrying helical flux
tubes is accompanied by plasma flows that may have diverse properties
depending on the location of interacting flux tubes, their inclination
and pitch. We apply the model to observations taken with the SOT
instrument, which includes spectro-polarimetric data, and perform
quantitative analysis.
Title: Preliminary Pre-flight Calibration of the AIA instrument on SDO
Authors: Boerner, P.; Soufli, R.; Podgorski, W.; Rausch, A.; Shing,
L.; Stern, R.; Lemen, J.; Title, A.; Wolfson, C. J.
Bibcode: 2008AGUSMSP51B..10B
Altcode:
In this poster we present the preliminary pre-flight photometric
calibration of the Atmospheric Imaging Assembly (AIA) aboard the
Solar Dynamics Observatory (SDO). The AIA instrument is set of four
reflecting telescopes designed to acquire high-resolution images of the
solar atmosphere in a variety of extreme ultraviolet, ultraviolet and
visible-light wavelength bands in order to study energy input, storage
and release in the dynamic, three- dimensional solar corona. AIA takes
images in ten wavelength channels, whose bandpasses are determined by
the collecting area dedicated to each channel and the efficiency of the
mirror coatings, filters, and detector. We describe the measurements
of each of these components and present the resulting effective area
functions. The effective areas are then used to produce temperature
response functions and expected count rates for observations of various
solar features.
Title: Patterns of Flux Emergence
Authors: Title, A.; Cheung, M.
Bibcode: 2008AGUSMSH54A..01T
Altcode:
The high spatial resolution and high cadence of the Solar Optical
Telescope on the JAXA Hinode spacecraft have allowed capturing many
examples of magnetic flux emergence from the scale of granulation
to active regions. The observed patterns of emergence are quite
similar. Flux emerges as a array of small bipoles on scales from
1 to 5 arc seconds throughout the region that the flux eventually
condenses. Because the fields emerging from the underlying flux rope
my appear many in small segments and the total flux (absolute sum) is
not a conserved quantity the amount of total flux on the surface may
vary significantly during the emergence process. Numerical simulations
of flux emergence exhibit patterns similar to observations. Movies of
both observations and numerical simulations will be presented.
Title: Sources and Sinks of the Evershed Flow
Authors: Shine, R. A.; Title, A. M.; Ichimoto, K.; Lites, B.
Bibcode: 2008AGUSMSP31A..01S
Altcode:
Extending the work of Ichimoto et al (2007), we investigate the sources
and sinks of the Evershed flow in sunspot penumbra using data from the
Solar Optical Telescope (SOT) instruments on the Hinode satellite. We
use spectral maps taken with the Spectro-Polarimeter (SP) that provide
detailed snapshots of the large sunspot in AR 10930 over a range
of viewing angles as it rotated across the solar disk in December
2006. These are supplemented by images taken with the Filtergraph
(FG) instrument that show the dynamics of the structures. AR 10930 has
some large sunspots showing sources and sinks within the penumbra as
well as near the inner and outer boundaries. There are also regions
of contact between penumbra of two sunspots (of opposite magnetic
polarity) that show stronger horizontal flows and downdrafts than seen
elsewhere in the penumbras. The relationship between Evershed "clouds"
showing quasi-periodic variations in the spatially averaged Evershed
flow and the penumbral fine structures is also investigated. This work
was supported by NASA contract NNM07AA01C.
Title: Disintegration of Magnetic Flux in Decaying Sunspots as
Observed with the Hinode/SOT
Authors: Kubo, M.; Lites, B. W.; Ichimoto, K.; Shimizu, T.; Suematsu,
Y.; Katsukawa, Y.; Tarbell, T. D.; Shine, R. A.; Title, A. M.; Nagata,
S.; Tsuneta, S.
Bibcode: 2008AGUSMSP31B..01K
Altcode:
Continuous observations of sunspot penumbrae with the Solar Optical
Telescope aboard Hinode clearly show that the outer boundary of the
penumbra fluctuates around its averaged position. The penumbral outer
boundary moves inward when granules appear in the outer penumbra. We
discover that such granules appear one after another while moving
magnetic features (MMFs) are separating from the penumbral "spines"
(penumbral features having fields that are stronger and more vertical
than their surroundings). These granules that appear in the outer
penumbra often merge with bright features inside the penumbra that move
with spines as they elongate toward the moat region. This suggests that
convective motions around the penumbral outer boundary are related to
disintegration of magnetic flux in the sunspot. We also find that dark
penumbral filaments frequently elongate into the moat region in the
vicinity of MMFs that detach from penumbral spines. Such elongating
dark penumbral filaments correspond to nearly horizontal fields
extending from the penumbra. Pairs of MMFs with positive and negative
polarities are sometimes observed along the elongating dark penumbral
filaments. This strongly supports the notion that such elongating dark
penumbral filaments have magnetic fields with a "sea serpent"-like
structure. Evershed flows, which are associated with the penumbral
horizontal fields, may be related to detachment of the MMFs from the
penumbral spines, as well as to the formation of the MMFs along the
dark penumbral filaments that elongate into the moat region.
Title: Optical Analysis of HiLiTE (High-Resolution Lightweight
Telescope for the EUV)
Authors: Boerner, P.; Martinez-Galarce, D.; de Pontieu, B.; Soufli,
R.; Katz, N.; Title, A.; Gullikson, E.
Bibcode: 2008AGUSMSP51B..09B
Altcode:
We have completed a preliminary design of a telescope capable
of observing the 500,000 K transition region at high spatial (0.2
arcseconds) and temporal (5 seconds) resolution. The High-resolution
Lightweight Telescope for the EUV (HiLiTE) is a Cassegrain telescope
with an aperture of 30 cm, with multilayer-coated optics tuned to the
465 Å the Ne VII emission line formed in plasma at 500,000 K. The
HiLiTE instrument, including both mirrors and the metering structure,
will be constructed entirely from lightweight, thermally stable, high-
stiffness advanced silicon carbide (SiC) material. In this poster we
provide an update on the development of the HiLiTE instrument concept,
including metrology on SiC optics and model results of the instrument's
optical performance during a proposed sounding rocket flight.
Title: On the Fine Structure and Formation of Sunspot Penumbrae
Authors: Ryutova, M.; Berger, T.; Title, A.
Bibcode: 2008ApJ...676.1356R
Altcode:
Recent high-resolution observations with the 1 m Swedish Solar Telescope
(SST) on La Palma reveal the fine substructure of penumbral filaments
and new properties of their dynamics. These findings provide both the
basis and constraints for novel models of the penumbra. We present new
observations of a large isolated sunspot near Sun center obtained with
the SST in 2006. Our data, taken simultaneously in the 4305 Å G-band
and 4364 Å continuum bandpasses and compiled in high-cadence movies,
confirm the previous results and reveal new features of penumbral
filament dynamics. We find that individual filaments are cylindrical
helices with the apparent properties of vortex tubes exhibiting flow
patterns similar to kinked flux tubes. Measured pitch/radius ratios
of helical filaments indicate their dynamic stability. We propose a
mechanism that explains the fine structure of penumbral filaments,
their observed dynamics, and their formation process in association
with sunspot properties. The mechanism assumes that the umbra itself
is a dense conglomerate of twisted, interlaced flux tubes with
peripheral filaments branching out from the "trunk" at different
heights due to ongoing reconnection processes and arcing downward to
the photosphere. The twist of individual filaments, and the resulting
distribution of magnetic fields and temperature, is due to the onset
of the well-known screw pinch instability, the parameters of which
can be measured from our data.
Title: Formation of Solar Magnetic Flux Tubes with Kilogauss Field
Strength Induced by Convective Instability
Authors: Nagata, Shin'ichi; Tsuneta, Saku; Suematsu, Yoshinori;
Ichimoto, Kiyoshi; Katsukawa, Yukio; Shimizu, Toshifumi; Yokoyama,
Takaaki; Tarbell, Theodore D.; Lites, Bruce W.; Shine, Richard A.;
Berger, Thomas E.; Title, Alan M.; Bellot Rubio, Luis R.; Orozco
Suárez, David
Bibcode: 2008ApJ...677L.145N
Altcode:
Convective instability has been a mechanism used to explain
the formation of solar photospheric flux tubes with kG field
strength. However, the turbulence of the Earth's atmosphere has
prevented ground-based observers from examining the hypothesis
with precise polarimetric measurement on the subarcsecond scale
flux tubes. Here we discuss observational evidence of this scenario
based on observations with the Solar Optical Telescope (SOT) aboard
Hinode. The cooling of an equipartition field strength flux tube
precedes a transient downflow reaching 6 km s-1 and the
intensification of the field strength to 2 kG. These observations
agree very well with the theoretical predictions.
Title: Transient horizontal magnetic fields in solar plage regions
Authors: Ishikawa, R.; Tsuneta, S.; Ichimoto, K.; Isobe, H.; Katsukawa,
Y.; Lites, B. W.; Nagata, S.; Shimizu, T.; Shine, R. A.; Suematsu,
Y.; Tarbell, T. D.; Title, A. M.
Bibcode: 2008A&A...481L..25I
Altcode: 2008arXiv0802.1769I
Aims:We report the discovery of isolated, small-scale emerging
magnetic fields in a plage region with the Solar Optical Telescope
aboard Hinode.
Methods: Spectro-polarimetric observations were
carried out with a cadence of 34 s for the plage region located near
disc center. The vector magnetic fields are inferred by Milne-Eddington
inversion.
Results: The observations reveal widespread occurrence
of transient, spatially isolated horizontal magnetic fields. The
lateral extent of the horizontal magnetic fields is comparable to
the size of photospheric granules. These horizontal magnetic fields
seem to be tossed about by upflows and downflows of the granular
convection. We also report an event that appears to be driven by the
magnetic buoyancy instability. We refer to buoyancy-driven emergence
as type 1 and convection-driven emergence as type 2. Although both
events have magnetic field strengths of about 600 G, the filling
factor of type 1 is a factor of two larger than that of type 2.
Conclusions: Our finding suggests that the granular convection in
the plage regions is characterized by a high rate of occurrence of
granular-sized transient horizontal fields.
Title: Net circular polarization of sunspots in high spatial
resolution
Authors: Ichimoto, K.; Tsuneta, S.; Suematsu, Y.; Katsukawa, Y.;
Shimizu, T.; Lites, B. W.; Kubo, M.; Tarbell, T. D.; Shine, R. A.;
Title, A. M.; Nagata, S.
Bibcode: 2008A&A...481L...9I
Altcode:
Context: Net circular polarization (NCP) of spectral lines in
sunspots has been most successfully explained by the presense of
discontinuities in the magnetic field inclination and flow velocity
along the line-of-sight in the geometry of the embedded flux tube model
of penumbrae (Δγ-effect).
Aims: The fine scale structure of
NCP in a sunspot is examined with special attention paid to spatial
relations of the Evershed flow to confirm the validity of the present
interpretation of the NCP of sunspots.
Methods: High resolution
spectro-polarimetric data of a positive-polarity sunspot obtained
by the Solar Optical Telescope aboard Hinode are analysed.
Results: A positive NCP is associated with the Evershed flow
channels in both limb-side and disk center-side penumbrae and with
upflows in the penumbra at disk center. The negative NCP in the disk
center-side penumbra is generated in inter-Evershed flow channels.
Conclusions: The first result is apparently inconsistent with the
current explanation of NCP with the Δγ-effect but rather suggests a
positive correlation between the magnetic field strength and the flow
velocity as the cause of the NCP. The second result serves as strong
evidence for the presence of gas flows in inter-Evershed flow channels.
Title: Hinode SOT Observations of Solar Quiescent Prominence Dynamics
Authors: Berger, Thomas E.; Shine, Richard A.; Slater, Gregory L.;
Tarbell, Theodore D.; Title, Alan M.; Okamoto, Takenori J.; Ichimoto,
Kiyoshi; Katsukawa, Yukio; Suematsu, Yoshinori; Tsuneta, Saku; Lites,
Bruce W.; Shimizu, Toshifumi
Bibcode: 2008ApJ...676L..89B
Altcode:
We report findings from multihour 0.2'' resolution movies of
solar quiescent prominences (QPs) observed with the Solar Optical
Telescope (SOT) on the Hinode satellite. The observations verify
previous findings of filamentary downflows and vortices in QPs. SOT
observations also verify large-scale transverse oscillations in QPs,
with periods of 20-40 minutes and amplitudes of 2-5 Mm. The upward
propagation speed of several waves is found to be ~10 km s-1,
comparable to the sound speed of a 10,000 K plasma, implying that
the waves are magnetoacoustic in origin. Most significantly, Hinode
SOT observations reveal that dark, episodic upflows are common in
QPs. The upflows are 170-700 km in width, exhibit turbulent flow,
and rise with approximately constant speeds of ~20 km s-1
from the base of the prominence to heights of ~10-20 Mm. The upflows
are visible in both the Ca II H-line and Hα bandpasses of SOT. The new
flows are seen in about half of the QPs observed by SOT to date. The
dark upflows resemble buoyant starting plumes in both their velocity
profile and flow structure. We discuss thermal and magnetic mechanisms
as possible causes of the plumes.
Title: Emergence of a Helical Flux Rope under an Active Region
Prominence
Authors: Okamoto, Takenori J.; Tsuneta, Saku; Lites, Bruce W.; Kubo,
Masahito; Yokoyama, Takaaki; Berger, Thomas E.; Ichimoto, Kiyoshi;
Katsukawa, Yukio; Nagata, Shin'ichi; Shibata, Kazunari; Shimizu,
Toshifumi; Shine, Richard A.; Suematsu, Yoshinori; Tarbell, Theodore
D.; Title, Alan M.
Bibcode: 2008ApJ...673L.215O
Altcode: 2008arXiv0801.1956O
Continuous observations were obtained of NOAA AR 10953 with the Solar
Optical Telescope (SOT) on board the Hinode satellite from 2007 April
28 to May 9. A prominence was located over the polarity inversion
line (PIL) to the southeast of the main sunspot. These observations
provided us with a time series of vector magnetic fields on the
photosphere under the prominence. We found four features: (1) The
abutting opposite-polarity regions on the two sides along the PIL first
grew laterally in size and then narrowed. (2) These abutting regions
contained vertically weak but horizontally strong magnetic fields. (3)
The orientations of the horizontal magnetic fields along the PIL on
the photosphere gradually changed with time from a normal-polarity
configuration to an inverse-polarity one. (4) The horizontal magnetic
field region was blueshifted. These indicate that helical flux rope
was emerging from below the photosphere into the corona along the PIL
under the preexisting prominence. We suggest that this supply of a
helical magnetic flux to the corona is associated with evolution and
maintenance of active region prominences.
Title: Observations and Modeling of the Early Acceleration Phase of
Erupting Filaments Involved in Coronal Mass Ejections
Authors: Schrijver, Carolus J.; Elmore, Christopher; Kliem, Bernhard;
Török, Tibor; Title, Alan M.
Bibcode: 2008ApJ...674..586S
Altcode: 2007arXiv0710.1609S
We examine the early phases of two near-limb filament destabilizations
involved in coronal mass ejections (CMEs) on 2005 June 16 and July
27, using high-resolution, high-cadence observations made with the
Transition Region and Coronal Explorer (TRACE), complemented by
coronagraphic observations by the Mauna Loa Solar Observatory (MLSO)
and the Solar and Heliospheric Observatory (SOHO). The filaments'
heights above the solar limb in their rapid-acceleration phases are
best characterized by a height dependence h(t) propto tm
with m near, or slightly above, 3 for both events. Such profiles are
incompatible with published results for breakout, MHD-instability,
and catastrophe models. We show numerical simulations of the
torus instability that approximate this height evolution in case a
substantial initial velocity perturbation is applied to the developing
instability. We argue that the sensitivity of magnetic instabilities
to initial and boundary conditions requires higher fidelity modeling of
all proposed mechanisms if observations of rise profiles are to be used
to differentiate between them. The observations show no significant
delays between the motions of the filament and of overlying loops:
the filaments seem to move as part of the overall coronal field until
several minutes after the onset of the rapid-acceleration phase.
Title: The Horizontal Magnetic Flux of the Quiet-Sun Internetwork
as Observed with the Hinode Spectro-Polarimeter
Authors: Lites, B. W.; Kubo, M.; Socas-Navarro, H.; Berger, T.; Frank,
Z.; Shine, R.; Tarbell, T.; Title, A.; Ichimoto, K.; Katsukawa, Y.;
Tsuneta, S.; Suematsu, Y.; Shimizu, T.; Nagata, S.
Bibcode: 2008ApJ...672.1237L
Altcode:
Observations of very quiet Sun using the Solar Optical
Telescope/Spectro-Polarimeter (SOT/SP) aboard the Hinode spacecraft
reveal that the quiet internetwork regions are pervaded by horizontal
magnetic flux. The spatial average horizontal apparent flux density
derived from wavelength-integrated measures of Zeeman-induced linear
polarization is BTapp = 55 Mx cm -2, as
compared to the corresponding average vertical apparent flux density of
| BLapp| = 11 Mx cm -2. Distributions
of apparent flux density are presented. Magnetic fields are organized on
mesogranular scales, with both horizontal and vertical fields showing
"voids" of reduced flux density of a few granules spatial extent. The
vertical fields are concentrated in the intergranular lanes, whereas the
stronger horizontal fields are somewhat separated spatially from the
vertical fields and occur most commonly at the edges of the bright
granules. High-S/N observations from disk center to the limb help
to constrain possible causes of the apparent imbalance between |
BLapp| and BTapp, with
unresolved structures of linear dimension on the surface smaller by at
least a factor of 2 relative to the SOT/SP angular resolution being one
likely cause of this discrepancy. Other scenarios for explaining this
imbalance are discussed. The horizontal fields are likely the source of
the "seething" fields of the quiet Sun discovered by Harvey et al. The
horizontal fields may also contribute to the "hidden" turbulent flux
suggested by studies involving Hanle effect depolarization of scattered
radiation.
Title: Hinode Observations of Flux Emergence in Quiet and Active
Regions
Authors: Lites, B. W.; Centeno, R.; Kubo, M.; Socas-Navarro, H. Berger,
T.; Frank, Z.; Shine, R.; Tarbell, T.; Title, A.; Ichimoto, K.;
Katsukawa, Y.; Tsuneta, S.; Suematsu, Y.; Shimizu, T.; Nagata, S.
Bibcode: 2008ASPC..383...71L
Altcode:
We review briefly the observational understanding of emergence of
flux in both the quiet Sun and active regions in the light of first
results from the joint Japan/US/UK Hinode mission. That spacecraft
is now providing us with our first continuous, high resolution
measurements of the photospheric vector magnetic field, along with
high resolution observations of the thermal and dynamic properties
of the chromosphere and corona. This review is intended to present a
few very early results and to highlight the potential for discovery
offered by this extraordinary new mission. The discovery of ubiquitous
horizontal magnetic flux in the quiet internetwork regions is presented.
Title: Mangetic field properties at the footpoints of solar
microflares (active-region transient brightenings)
Authors: Shimizu, T.; Kano, R.; Katsukawa, Y.; Kubo, M.; Deluca, E.;
Ichimoto, K.; Lites, B.; Nagata, S.; Sakao, T.; Shine, R.; Suematsu,
Y.; Tarbell, T.; Title, A.; Tsuneta, S.
Bibcode: 2007AGUFMSH52C..06S
Altcode:
Solar active regions produce numerous numbers of small-scale explosive
energy releases, i.e., microflares, which are captured by imaging
observations in soft X-rays as transient brightenings of small-scale
coronal loops. Thanks to advanced performance of X-Ray Telescope (XRT)
onboard the Hinode satellite, we can investigate finer structure
of the brightening X-ray sources in more details than we did with
Yohkoh data. One of important questions on microflares is what causes
microflares. The simultaneous visible-light observations by the Solar
Optical Telescope (SOT) allow us to explore magnetic activities
and magnetic field configuration at the photospheric footpoints
of brightening loops, giving key observations to investigate the
question. For our investigations of corona-photosphere magnetic
coupling, we have established co-alignment between SOT and XRT
with accuracy better than 1 arcsec (Shimizu et al. 2007, PASJ in
press). It turns out that Ca II H observations are very useful
to identify the exact positions of footpoints of X-ray transient
brightening loops. Small "Kernels" are sometimes observed in Ca II H
and they may be signature of highly accelerated non-thermal particles
impinging on chromosphere. As already shown in Shimizu et al.(2002),
frequent transient brightenings are observed at the locations where
emerging activities are on going. However, another type of brightening
triggering mechanism should exist to explain some observed multiple-loop
brightenings. In the multiple-loop brightenings, multiple loops are
magnetically in parallel with each other and no apparent magnetic
activities, such as emerging and canceling, are observed at and near
the footpoints. This paper will present SOT observations of some
microflares observed with XRT.
Title: The Astmospheric Imaging Assembly
Authors: Title, A.
Bibcode: 2007AGUFMSH44B1737T
Altcode:
The Atmospheric Imaging Assembly is a set of four EUV telescopes that
will fly on the Solar Dynamic Observatory. The instrument has recently
been delivered for integration to the Solar Dynamics Observatory. This
poster provides an overview of the AIA instrument, its operation,
and the data distribution plan. Pictures of the as delivery instrument
are shown.
Title: Small-Scale Jetlike Features in Penumbral Chromospheres
Authors: Katsukawa, Y.; Berger, T. E.; Ichimoto, K.; Lites, B. W.;
Nagata, S.; Shimizu, T.; Shine, R. A.; Suematsu, Y.; Tarbell, T. D.;
Title, A. M.; Tsuneta, S.
Bibcode: 2007Sci...318.1594K
Altcode:
We observed fine-scale jetlike features, referred to as penumbral
microjets, in chromospheres of sunspot penumbrae. The microjets
were identified in image sequences of a sunspot taken through a Ca II
H-line filter on the Solar Optical Telescope on board the Japanese solar
physics satellite Hinode. The microjets’ small width of 400 kilometers
and short duration of less than 1 minute make them difficult to identify
in existing observations. The microjets are possibly caused by magnetic
reconnection in the complex magnetic configuration in penumbrae and
have the potential to heat the corona above a sunspot.
Title: Chromospheric Alfvénic Waves Strong Enough to Power the
Solar Wind
Authors: De Pontieu, B.; McIntosh, S. W.; Carlsson, M.; Hansteen,
V. H.; Tarbell, T. D.; Schrijver, C. J.; Title, A. M.; Shine, R. A.;
Tsuneta, S.; Katsukawa, Y.; Ichimoto, K.; Suematsu, Y.; Shimizu, T.;
Nagata, S.
Bibcode: 2007Sci...318.1574D
Altcode:
Alfvén waves have been invoked as a possible mechanism for the heating
of the Sun's outer atmosphere, or corona, to millions of degrees and
for the acceleration of the solar wind to hundreds of kilometers per
second. However, Alfvén waves of sufficient strength have not been
unambiguously observed in the solar atmosphere. We used images of
high temporal and spatial resolution obtained with the Solar Optical
Telescope onboard the Japanese Hinode satellite to reveal that the
chromosphere, the region sandwiched between the solar surface and
the corona, is permeated by Alfvén waves with strong amplitudes on
the order of 10 to 25 kilometers per second and periods of 100 to
500 seconds. Estimates of the energy flux carried by these waves and
comparisons with advanced radiative magnetohydrodynamic simulations
indicate that such Alfvén waves are energetic enough to accelerate
the solar wind and possibly to heat the quiet corona.
Title: Chromospheric Anemone Jets as Evidence of Ubiquitous
Reconnection
Authors: Shibata, Kazunari; Nakamura, Tahei; Matsumoto, Takuma; Otsuji,
Kenichi; Okamoto, Takenori J.; Nishizuka, Naoto; Kawate, Tomoko;
Watanabe, Hiroko; Nagata, Shin'ichi; UeNo, Satoru; Kitai, Reizaburo;
Nozawa, Satoshi; Tsuneta, Saku; Suematsu, Yoshinori; Ichimoto, Kiyoshi;
Shimizu, Toshifumi; Katsukawa, Yukio; Tarbell, Theodore D.; Berger,
Thomas E.; Lites, Bruce W.; Shine, Richard A.; Title, Alan M.
Bibcode: 2007Sci...318.1591S
Altcode: 2008arXiv0810.3974S
The heating of the solar chromosphere and corona is a long-standing
puzzle in solar physics. Hinode observations show the ubiquitous
presence of chromospheric anemone jets outside sunspots in active
regions. They are typically 3 to 7 arc seconds = 2000 to 5000 kilometers
long and 0.2 to 0.4 arc second = 150 to 300 kilometers wide, and their
velocity is 10 to 20 kilometers per second. These small jets have an
inverted Y-shape, similar to the shape of x-ray anemone jets in the
corona. These features imply that magnetic reconnection similar to that
in the corona is occurring at a much smaller spatial scale throughout
the chromosphere and suggest that the heating of the solar chromosphere
and corona may be related to small-scale ubiquitous reconnection.
Title: Twisting Motions of Sunspot Penumbral Filaments
Authors: Ichimoto, K.; Suematsu, Y.; Tsuneta, S.; Katsukawa, Y.;
Shimizu, T.; Shine, R. A.; Tarbell, T. D.; Title, A. M.; Lites, B. W.;
Kubo, M.; Nagata, S.
Bibcode: 2007Sci...318.1597I
Altcode:
The penumbra of a sunspot is composed of numerous thin, radially
extended, bright and dark filaments carrying outward gas flows
(the Evershed flow). Using high-resolution images obtained by the
Solar Optical Telescope aboard the solar physics satellite Hinode, we
discovered a number of penumbral bright filaments revealing twisting
motions about their axes. These twisting motions are observed only
in penumbrae located in the direction perpendicular to the symmetry
line connecting the sunspot center and the solar disk center, and
the direction of the twist (that is, lateral motions of intensity
fluctuation across filaments) is always from limb side to disk-center
side. Thus, the twisting feature is not an actual twist or turn of
filaments but a manifestation of dynamics of penumbral filaments with
three-dimensional radiative transfer effects.
Title: Hinode SOT observations of plume upflows and cascading
downflows in quiescent solar prominences
Authors: Berger, T.; Shine, R.; Slater, G.; Tarbell, T.; Title, A.;
Lites, B.; Tsuneta, S.; Okamoto, T. J.; Ichimoto, K.; Katsukawa, Y.;
Sekii, T.; Suematsu, Y.; Shimizu, T.
Bibcode: 2007AGUFMSH53A1065B
Altcode:
We present several Hinode SOT filtergram movies of quiescent solar
prominences that show newly discovered "plume-like" upflows and
cascading "waterfall-like" downflows that persist for the entire
multi-hour duration of the observations. The flow speeds are on the
order of 10 km/sec with typical widths of 400-700 km. Preliminary
calculations show that if the upflows are buoyancy driven, the
associated thermal perturbation is on the order of 10,000 K, sufficient
to explain the dark appearance of the upflows in the interference
filter passbands. In addition we observe rotational vortices and
body oscillations within the prominences. These new observations
challenge current magnetostatic models of solar prominences by showing
that prominence plasmas are in constant motion, often in directions
perpendicular to the magnetic field lines proposed by the models. TRACE,
Hinode/EIS, and Hinode/XRT observations are used to investigate the
differential topology of the flows across temperature regimes.
Title: On the Chromospheric Micro-jets Associated with the Penumbral
Filaments
Authors: Ryutova, M.; Berger, T.; Tarbell, T.; Frank, Z.; Title, A.
Bibcode: 2007AGUFMSH22A0843R
Altcode:
We present observations of sunspot penumbrae obtained during the disk
passage of AR 10923 (November 10--20, 2006) with the Solar Optical
Telescope (SOT) on the Hinode satellite. Co-aligned multi-hour movies
taken simultaneously in several wavelengths show fine-scale dynamics
at the sub-arcsecond level. The dynamics include helical flows along
penumbral filaments, branching of filaments, and penumbral "micro-jets"
recently described by Katsukawa et al. (AAS 210, 94.13). We present
quantitative analyzes of the penumbral jets and interpret them relative
to our recent model of penumbral filaments (Ryutova, Berger and Title,
2007, in "Collective phenomena in macroscopic systems", Ed. G. Bertin,
et al., World Scientific) to show that the jets are the result of
magnetic reconnection of the helical field lines in neighboring
non-collinear filaments.
Title: Coronal Transverse Magnetohydrodynamic Waves in a Solar
Prominence
Authors: Okamoto, T. J.; Tsuneta, S.; Berger, T. E.; Ichimoto, K.;
Katsukawa, Y.; Lites, B. W.; Nagata, S.; Shibata, K.; Shimizu, T.;
Shine, R. A.; Suematsu, Y.; Tarbell, T. D.; Title, A. M.
Bibcode: 2007Sci...318.1577O
Altcode: 2008arXiv0801.1958O
Solar prominences are cool 104 kelvin plasma clouds
supported in the surrounding 106 kelvin coronal plasma by
as-yet-undetermined mechanisms. Observations from Hinode show fine-scale
threadlike structures oscillating in the plane of the sky with periods
of several minutes. We suggest that these represent Alfvén waves
propagating on coronal magnetic field lines and that these may play
a role in heating the corona.
Title: The High-resolution Lightweight Telescope for the EUV (HiLiTE)
Authors: Martínez-Galarce, D.; Boerner, P.; de Pontieu, B.; Katz,
N.; Title, A.; Soufli, R.; Gullikson, E.
Bibcode: 2007AGUFMSH44B1738M
Altcode:
The highly-structured and extremely dynamic interface between the
photosphere and the corona is of crucial importance in understanding
solar activity and space weather. Recent high-resolution observations
with Hinode have shown that understanding this interface requires the
ability to study the transition region by imaging plasma around 500,000
K on spatial scales of ~0.2 arc seconds, at cadences of ~5 seconds or
less. We have completed a preliminary design of a telescope capable
of meeting all three of these requirements - thermal, spatial, and
temporal, called the High-resolution Lightweight Telescope for the EUV
(HiLiTE). HiLiTE is a Cassegrain telescope with an aperture of 30 cm,
angular resolution of ~0.2 arc seconds, and a mass that is about 1/4
that of one of the 20 cm aperture telescopes on SDO/AIA. The instrument
bandpass will be tuned to the 46.5 nm Ne VII emission line formed in
plasma at ~500,000 K. HiLiTE, including both mirrors and the metering
structure, will be constructed entirely from lightweight, thermally
stable, high-stiffness advanced Silicon Carbide (SiC) material. While
SiC is an extremely promising material for space telescopes, SiC optics
with the figure and surface finish required for normal-incidence
multilayers have not yet been demonstrated. Upon integrating this
instrument with an Advanced CMOS detector (in parallel development
at Lockheed Martin via another internally funded program) and on
board electronics, HiLiTE can easily be retrofitted to fly on board a
sounding rocket, acting as a path finder to a post-AIA, Explorer-class
mission. Herein, we give an update of the HiLiTE instrument development
program, discussing expected instrument performance as well as the
advantages of using SiC for EUV/Soft X-ray imaging in solar physics.
Title: Quiet-Sun Internetwork Magnetic Fields from the Inversion of
Hinode Measurements
Authors: Orozco Suárez, D.; Bellot Rubio, L. R.; del Toro Iniesta,
J. C.; Tsuneta, S.; Lites, B. W.; Ichimoto, K.; Katsukawa, Y.; Nagata,
S.; Shimizu, T.; Shine, R. A.; Suematsu, Y.; Tarbell, T. D.; Title,
A. M.
Bibcode: 2007ApJ...670L..61O
Altcode: 2007arXiv0710.1405O
We analyze Fe I 630 nm observations of the quiet Sun at disk center
taken with the spectropolarimeter of the Solar Optical Telescope aboard
the Hinode satellite. A significant fraction of the scanned area,
including granules, turns out to be covered by magnetic fields. We
derive field strength and inclination probability density functions from
a Milne-Eddington inversion of the observed Stokes profiles. They show
that the internetwork consists of very inclined, hG fields. As expected,
network areas exhibit a predominance of kG field concentrations. The
high spatial resolution of Hinode's spectropolarimetric measurements
brings to an agreement the results obtained from the analysis of
visible and near-infrared lines.
Title: Center-to-Limb Variation of Stokes V Asymmetries in Solar
Pores Observed with the Hinode Spectro-Polarimeter
Authors: Morinaga, Shuji; Nagata, Shin'ichi; Ichimoto, Kiyoshi;
Suematsu, Yoshinori; Tsuneta, Saku; Katsukawa, Yukio; Shimizu,
Toshifumi; Shine, Richard A.; Tarbell, Theodore D.; Title, Alan M.;
Lites, Bruce; Kubo, Masahito; Sakurai, Takashi
Bibcode: 2007PASJ...59S.613M
Altcode:
Here we present spectro-polarimetric measurements of several pores
and the surrounding regions taken with the Solar Optical Telescope
aboard Hinode at various viewing angles. We analyzed the Stokes V
area asymmetry, and confirmed that it is depressed at the center of
the pores, while it shows large positive values (a blue lobe larger
than a red lobe) in the surrounding area; this is consistent with a
previous report. In addition to this ring of positive asymmetry, we
found regions of alternating positive and negative area asymmetries
when weak V regions were observed near the solar limb. The positive
asymmetry occurs on the disk-center side and the negative asymmetry
on the limb side of the magnetic concentrations. These center-to-limb
variations of the Stokes V area asymmetry can be interpreted as being
a systematic inflow of plasma into the magnetic concentrations from
their surroundings.
Title: Initial Results on Line-of-Sight Field Calibrations of SP/NFI
Data Taken by SOT/Hinode
Authors: Chae, Jongchul; Moon, Yong-Jae; Park, Young-Deuk; Ichimoto,
Kiyoshi; Sakurai, Takashi; Suematsu, Yoshinori; Tsuneta, Saku;
Katsukawa, Yukio; Shimizu, Toshifumi; Shine, Richard A.; Tarbell,
Theodore D.; Title, Alan M.; Lites, Bruce; Kubo, Masahito; Nagata,
Shin'ichi; Yokoyama, Takaaki
Bibcode: 2007PASJ...59S.619C
Altcode:
We present initial results on the line-of-sight field calibration
of the two kinds of Stokes I and V data taken by the Solar Optical
Telescope on the satellite Hinode: spectral profiles of Stokes I and V
parameters recorded on the Spectro-polarimeter (SP), and monochromatic
images of the same parameters recorded on the Narrow-band Filter Imager
(NFI). By applying the center-of-gravity method to the SP data of
AR10930 taken on 2006 December 11, we determined the line-of-sight field
at every location in the active region. As a result, we found that the
line-of-sight field strength ranges up to 2kG in plages, even without
taking into account the filling factor, and up to 3.5kG or higher values
inside the umbra of the major sunspot. We calibrated the NFI data in
reference to the field determined from the SP data. In regions outside
the sunspots and the penumbral regions, we adopted a linear relation,
B|| = βV / I, between the circular polarization, V / I,
and the line-of-sight field strength, B||, and obtained β =
23.5kG in regions outside the sunspots, and β = 12.0kG in penumbral
regions. In umbral regions of sunspots, a first-order polynomial was
adopted to model the reversal of the polarization signal over the
field strength.
Title: Response of the Solar Atmosphere to Magnetic Flux Emergence
from Hinode Observations
Authors: Li, Hui; Sakurai, Takashi; Ichimito, Kiyoshi; Suematsu,
Yoshinori; Tsuneta, Saku; Katsukawa, Yukio; Shimizu, Toshifumi; Shine,
Richard A.; Tarbell, Theodore D.; Title, Alan M.; Lites, Bruce; Kubo,
Masahito; Nagata, Shin'ichi; Kotoku, Jun; Shibasaki, Kiyoto; Saar,
Steven H.; Bobra, Monica
Bibcode: 2007PASJ...59S.643L
Altcode:
No abstract at ADS
Title: Initial Helioseismic Observations by Hinode/SOT
Authors: Sekii, Takashi; Kosovichev, Alexander G.; Zhao, Junwei;
Tsuneta, Saku; Shibahashi, Hiromoto; Berger, Thomas E.; Ichimoto,
Kiyoshi; Katsukawa, Yukio; Lites, Bruce; Nagata, Shin'ichi; Shimizu,
Toshifumi; Shine, Richard A.; Suematsu, Yoshinori; Tarbell, Theodore
D.; Title, Alan M.
Bibcode: 2007PASJ...59S.637S
Altcode: 2007arXiv0709.1806S
Results from initial helioseismic observations by the Solar Optical
Telescope on-board Hinode are reported. It has been demonstrated
that intensity oscillation data from the Broadband Filter Imager
can be used for various helioseismic analyses. The k - ω power
spectra, as well as the corresponding time-distance cross-correlation
function, which promise high-resolution time-distance analysis below
the 6-Mm travelling distance, were obtained for G-band and CaII-H
data. Subsurface supergranular patterns were observed from our first
time-distance analysis. The results show that the solar oscillation
spectrum is extended to much higher frequencies and wavenumbers, and
the time-distance diagram is extended to much shorter travel distances
and times than were observed before, thus revealing great potential
for high-resolution helioseismic observations from Hinode.
Title: Hinode Observations of Horizontal Quiet Sun Magnetic Flux
and the ``Hidden Turbulent Magnetic Flux''
Authors: Lites, Bruce; Socas-Navarro, Hector; Kubo, Masahito; Berger,
Thomas; Frank, Zoe; Shine, Richard A.; Tarbell, Theodore D.; Title,
Alan M.; Ichimoto, Kiyoshi; Katsukawa, Yukio; Tsuneta, Saku; Suematsu,
Yoshinori; Shimizu, Toshifumi
Bibcode: 2007PASJ...59S.571L
Altcode:
We present observations of magnetic fields of the very quiet Sun
near disk center using the Spectro-Polarimeter of the Solar Optical
Telescope aboard the Hinode satellite. These observations reveal for
the first time the ubiquitous presence of horizontal magnetic fields in
the internetwork regions. The horizontal fields are spatially distinct
from the vertical fields, demonstrating that they are not arising mainly
from buffeting of vertical flux tubes by the granular convection. The
horizontal component has an average ``apparent flux density'' of
55Mxcm-2 (assuming the horizontal field structures are
spatially resolved), in contrast to the average apparent vertical flux
density of 11Mxcm-2. The vertical fields reside mainly in
the intergranular lanes, whereas the horizontal fields occur mainly
over the bright granules, with a preference to be near the outside
edge of the bright granules. The large apparent imbalance of vertical
and horizontal flux densities is discussed, and several scenarios are
presented to explain this imbalance.
Title: Strategy for the Inversion of Hinode Spectropolarimetric
Measurements in the Quiet Sun
Authors: Orozco Suárez, David; Bellot Rubio, Luis R.; Del Toro
Iniesta, Jose Carlos; Tsuneta, Saku; Lites, Bruce; Ichimoto, Kiyoshi;
Katsukawa, Yukio; Nagata, Shin'ichi; Shimizu, Toshifumi; Shine,
Richard A.; Suematsu, Yoshinori; Tarbell, Theodore D.; Title, Alan M.
Bibcode: 2007PASJ...59S.837O
Altcode: 2007arXiv0709.2033O
In this paper we propose an inversion strategy for the analysis of
spectropolarimetric measurements taken by Hinode in the quiet Sun. The
Spectro-Polarimeter of the Solar Optical Telescope aboard Hinode records
the Stokes spectra of the FeI line pair at 630.2nm with unprecendented
angular resolution, high spectral resolution, and high sensitivity. We
discuss the need to consider a local stray-light contamination to
account for the effects of telescope diffraction. The strategy is
applied to observations of a wide quiet Sun area at disk center. Using
these data we examine the influence of noise and initial guess models
in the inversion results. Our analysis yields the distributions of
magnetic field strengths and stray-light factors. They show that quiet
Sun internetwork regions consist mainly of hG fields with stray-light
contamination of about 0.8.
Title: Penumbral Dynamics and its Manifestation in the Overlying
Chromosphere
Authors: Ryutova, Margarita; Berger, Thomas; Tarbell, Theodor; Frank,
Zoe; Title, Alan
Bibcode: 2007APS..DPPYP8056R
Altcode:
Mature sunspots are usually surrounded by penumbra - a dense
conglomerate of a random interlaced flux tubes with varying
inclinations. High resolution observations show a fine sub-structure
of penumbral filaments and new regularities in their dynamics. These
regularities fit well our recent model of penumbra based on cascading
reconnection events occurring in the system of non-collinear flux
tubes. Each act of reconnection generates twist in the reconnected
filaments and facilitates the onset of a screw pinch instability,
consistent with the observations showing that individual filaments
are cylindrical helices with a pitch/radius ratio providing their
stability. In addition, the post-reconnection products produce a
sling-shot effect that generates oblique shocks and leads to appearence
of a lateral jets. Here we report high resolution (120-180 km) high
cadence (15-30 sec) observations taken with the Solar Optical Telescope
(SOT) on the Hinode satellite. Co-aligned multi-hour movies taken
simultaneously in several wavelengths show detailed behavior of penumbra
filaments and their effect on the overlying chromosphere. We confirm
the ubiquitous nature of penumbral micro-jets recently discovered by
SOT instrument (Katsukawa et al. 2007, AAS 210, 94.13), and present
quantitative analysis of chromospheric jets based on our recent model
of penumbra.
Title: Hinode Observations of a Vector Magnetic Field Change
Associated with a Flare on 2006 December 13
Authors: Kubo, Masahito; Yokoyama, Takaaki; Katsukawa, Yukio; Lites,
Bruce; Tsuneta, Saku; Suematsu, Yoshinori; Ichimoto, Kiyoshi; Shimizu,
Toshifumi; Nagata, Shin'ichi; Tarbell, Theodore D.; Shine, Richard A.;
Title, Alan M.; Elmore David
Bibcode: 2007PASJ...59S.779K
Altcode: 2007arXiv0709.2397K
Continuous observations of the flare productive active region 10930
were successfully carried out with the Solar Optical Telescope aboard
the Hinode spacecraft during 2006 December 6 to 19. We focused on the
evolution of photospheric magnetic fields in this active region, and the
magnetic field properties at the site of the X3.4 class flare, using
a time series of vector field maps with high spatial resolution. The
X3.4 class flare occurred on 2006 December 13 at the apparent
collision site between the large, opposite polarity umbrae. Elongated
magnetic structures with alternatingly positive and negative polarities
resulting from flux emergence appeared one day before the flare in the
collision site penumbra. Subsequently, the polarity inversion line
at the collision site became very complicated. The number of bright
loops in CaII H increased during the formation of these elongated
magnetic structures. Flare ribbons and bright loops evolved along
the polarity inversion line and one footpoint of the bright loop was
located in a region having a large departure of the field azimuth angle
with respect to its surroundings. SOT observations with high spatial
resolution and high polarization precision revealed temporal change in
the fine structure of magnetic fields at the flare site: some parts of
the complicated polarity inversion line then disappeared, and in those
regions the azimuth angle of the photospheric magnetic field changed by
about 90°, becoming more spatially uniform within the collision site.
Title: The Analysis of Penumbral Fine Structure Using an Advanced
Inversion Technique
Authors: Jurcák, Jan; Bellot Rubio, Luis; Ichimoto, Kiyoshi;
Katsukawa, Yukio; Lites, Bruce; Nagata, Shin'ichi; Shimizu, Toshifumi;
Suematsu, Yoshinori; Tarbell, Theodore D.; Title, Alan M.; Tsuneta,
Saku
Bibcode: 2007PASJ...59S.601J
Altcode: 2007arXiv0707.1560J
We present a method to study the penumbral fine structure using data
obtained by the spectropolarimeter on board Hinode. For the first
time, the penumbral filaments can be considered as being resolved in
spectropolarimetric measurements. This enables us to use inversion
codes with only one-component model atmospheres, and thus to assign
the obtained stratifications of the plasma parameters directly to the
penumbral fine structure. This approach was applied to the limb-side
part of the penumbra in the active region NOAA10923. Preliminary results
show a clear dependence of the plasma parameters on the continuum
intensity in the inner penumbra, i.e., a weaker and horizontal magnetic
field along with an increased line-of-sight velocity are found in the
low layers of the bright filaments. The results in the mid penumbra
are ambiguous, and future analyses are necessary to unveil the magnetic
field structure and other plasma parameters there.
Title: Fine-Scale Structures of the Evershed Effect Observed by the
Solar Optical Telescope aboard Hinode
Authors: Ichimoto, Kiyoshi; Shine, Richard A.; Lites, Bruce; Kubo,
Masahito; Shimizu, Toshifumi; Suematsu, Yoshinori; Tsuneta, Saku;
Katsukawa, Yukio; Tarbell, Theodore D.; Title, Alan M.; Nagata,
Shin'ichi; Yokoyama, Takaaki; Shimojo, Masumi
Bibcode: 2007PASJ...59S.593I
Altcode:
The small-scale structure of the Evershed effect is being studied
using data obtained by the Spectropolarimeter and the Broadband Filter
Imager of the Solar Optical Telescope aboard Hinode. We find that the
Evershed flow starts at the leading edge of inwardly migrating bright
penumbral grains, and turns to nearly a horizontal flow preferentially
in the dark lanes of the penumbra. A number of small elongated regions
that have an upward motion of ∼ 1kms-1 are found in the
deep photosphere distributed over the penumbra. They are cospatial
with bright grains and have relatively horizontal magnetic fields. A
number of patches having a strong downward motion associated with the
opposite magnetic polarity from the sunspot are also found in the mid
and outer penumbra. They could be identified as foot points of the
Evershed flow channels, though the identification of individual pairs
is not straightforward. Our results provide strong support for some
recent findings from ground-based high-resolution observations, and
are in general agreement with the well-known picture of the uncombed
structure of the penumbra, in which the penumbrae consist of rising
flux tubes carrying nearly horizontal Evershed flows embedded in more
vertical background magnetic fields.
Title: Flare Ribbons Observed with G-band and FeI 6302Å, Filters
of the Solar Optical Telescope on Board Hinode
Authors: Isobe, Hiroaki; Kubo, Masahito; Minoshima, Takashi; Ichimoto,
Kiyoshi; Katsukawa, Yukio; Tarbell, Theodore D.; Tsuneta, Saku; Berger,
Thomas E.; Lites, Bruce; Nagata, Shin'ichi; Shimizu, Toshifumi; Shine,
Richard A.; Suematsu, Yoshinori; Title, Alan M.
Bibcode: 2007PASJ...59S.807I
Altcode: 2007arXiv0711.3946I
The Solar Optical Telescope (SOT) on board the Hinode satellite observed
an X3.4 class flare on 2006 December 13. A typical two-ribbon structure
was observed, not only in the chromospheric CaII H line, but also in
the G-band and FeI 6302Å line. The high-resolution, seeing-free images
achieved by SOT revealed, for the first time, sub-arcsec fine structures
of the ``white light'' flare. The G-band flare ribbons on sunspot
umbrae showed a sharp leading edge, followed by a diffuse inside,
as well as a previously known core-halo structure. The underlying
structures, such as umbral dots, penumbral filaments, and granules,
were visible in the flare ribbons. Assuming that the sharp leading
edge was directly heated by a particle beam and the diffuse parts were
heated by radiative back-warming, we estimated the depth of the diffuse
flare emission using an intensity profile of the flare ribbon. We found
that the depth of the diffuse emission was about 100km or less from
the height of the source of radiative back-warming. The flare ribbons
were also visible in the Stokes-V images of FeI 6302Å, as a transient
polarity reversal. This is probably related to a ``magnetic transient''
reported in the literature. The intensity increase in Stokes-I images
indicates that the FeI 6302Å line was significantly deformed by the
flare, which may cause such a magnetic transient.
Title: Observations of Sunspot Oscillations in G Band and CaII H
Line with Solar Optical Telescope on Hinode
Authors: Nagashima, Kaori; Sekii, Takashi; Kosovichev, Alexander G.;
Shibahashi, Hiromoto; Tsuneta, Saku; Ichimoto, Kiyoshi; Katsukawa,
Yukio; Lites, Bruce; Nagata, Shin'ichi; Shimizu, Toshifumi; Shine,
Richard A.; Suematsu, Yoshinori; Tarbell, Theodore D.; Title, Alan M.
Bibcode: 2007PASJ...59S.631N
Altcode: 2007arXiv0709.0569N
Exploiting high-resolution observations made by the Solar Optical
Telescope on board Hinode, we investigate the spatial distribution
of the power spectral density of the oscillatory signal in and around
the active region NOAA 10935. The G-band data show that in the umbra
the oscillatory power is suppressed in all frequency ranges. On
the other hand, in CaII H intensity maps oscillations in the umbra,
so-called umbral flashes, are clearly seen with the power peaking around
5.5mHz. The CaII H power distribution shows the enhanced elements with
the spatial scale of the umbral flashes over most of the umbra, but
there is a region with suppressed power at the center of the umbra. The
origin and property of this node-like feature remain unexplained.
Title: Hinode SP Vector Magnetogram of AR10930 and Its
Cross-Comparison with MDI
Authors: Moon, Yong-Jae; Kim, Yeon-Han; Park, Young-Deuk; Ichimoto,
Kiyoshi; Sakurai, Takashi; Chae, Jongchul; Cho, Kyung Suk; Bong,
Suchan; Suematsu, Yoshinori; Tsuneta, Saku; Katsukawa, Yukio; Shimojo,
Masumi; Shimizu, Toshifumi; Shine, Richard A.; Tarbell, Theodore D.;
Title, Alan M.; Lites, Bruce; Kubo, Masahito; Nagata, Shin'ichi;
Yokoyama, Takaaki
Bibcode: 2007PASJ...59S.625M
Altcode:
We present one Hinode Spectropolarimeter (SP) magnetogram of AR 10930
that produced several major flares. The inversion from Stokes profiles
to magnetic field vectors was made using the standard Milne-Eddington
code. We successfully applied the Uniform Shear Method for resolving
the 180° ambiguity to the magnetogram. The inversion gave very strong
magnetic field strengths (near 4500 gauss) for a small portion of area
in the umbra. Considering that the observed V-profile of 6301.5Å was
well-fitted as well as a direct estimation of the Zeeman splitting
results in 4300-4600 gauss, we think that the field strengths
should not be far from the actual value. A cross-comparison of the
Hinode SP and SOHO MDI high resolution flux densities shows that the
MDI flux density could be significantly underestimated by about a
factor of two. In addition, it has a serious negative correlation
(the so-called Zeeman saturation effect) with the Hinode SP flux
density for umbral regions. Finally, we could successfully obtain
a recalibrated MDI magnetogram that has been corrected for the
Zeeman saturation effect using not only a pair of MDI intensity and
magnetogram data simultaneously observed, but also the relationship
from the cross-comparison between the Hinode SP and MDI flux densities.
Title: Formation Process of a Light Bridge Revealed with the Hinode
Solar Optical Telescope
Authors: Katsukawa, Yukio; Yokoyama, Takaaki; Berger, Thomas E.;
Ichimoto, Kiyoshi; Kubo, Masahito; Lites, Bruce; Nagata, Shin'ichi;
Shimizu, Toshifumi; Shine, Richard A.; Suematsu, Yoshinori; Tarbell,
Theodore D.; Title, Alan M.; Tsuneta, Saku
Bibcode: 2007PASJ...59S.577K
Altcode: 2007arXiv0709.2527K
The Solar Optical Telescope (SOT) on-board Hinode successfully and
continuously observed the formation process of a light bridge in a
matured sunspot of the NOAA active region 10923 for several days with
high spatial resolution. During its formation, many umbral dots were
observed to be emerging from the leading edges of penumbral filaments,
and rapidly intruding into the umbra. The precursor of the light bridge
formation was also identified as a relatively slow inward motion of
the umbral dots, which emerged not near the penumbra, but inside the
umbra. The spectro-polarimeter on SOT provided physical conditions in
the photosphere around the umbral dots and the light bridges. We found
that the light bridges and the umbral dots had significantly weaker
magnetic fields associated with upflows relative to the core of the
umbra, which implies that there was hot gas with weak field strength
penetrating from the subphotosphere to near the visible surface inside
those structures. There needs to be a mechanism to drive the inward
motion of the hot gas along the light bridges. We suggest that the
emergence and the inward motion are triggered by a buoyant penumbral
flux tube as well as subphotospheric flow crossing the sunspot.
Title: Umbral Fine Structures in Sunspots Observed with Hinode Solar
Optical Telescope
Authors: Kitai, Reizaburo; Watanabe, Hiroko; Nakamura, Tahei; Otsuji,
Ken-ichi; Matsumoto, Takuma; UeNo, Satoru; Nagata, Shin'ichi; Shibata,
Kazunari; Muller, Richard; Ichimoto, Kiyoshi; Tsuneta, Saku; Suematsu,
Yoshinori; Katsukawa, Yukio; Shimizu, Toshifumi; Tarbell, Theodore D.;
Shine, Richard A.; Title, Alan M.; Lites, Bruce
Bibcode: 2007PASJ...59S.585K
Altcode: 2007arXiv0711.3266K
A high resolution imaging observation of a sunspot umbra was made with
the Hinode Solar Optical Telescope. Filtergrams at wavelengths of the
blue and green continua were taken during three consecutive days. The
umbra consisted of a dark core region, several diffuse components,
and numerous umbral dots. We derived basic properties of umbral dots
(UDs), especially their temperatures, lifetimes, proper motions,
spatial distribution, and morphological evolution. The brightness
of UDs is confirmed to depend on the brightness of their surrounding
background. Several UDs show fission and fusion. Thanks to the stable
condition of the space observation, we could for the first time follow
the temporal behavior of these events. The derived properties of the
internal structure of the umbra are discussed from the viewpoint of
magnetoconvection in a strong magnetic field.
Title: On Connecting the Dynamics of the Chromosphere and Transition
Region with Hinode SOT and EIS
Authors: Hansteen, Viggo H.; de Pontieu, Bart; Carlsson, Mats;
McIntosh, Scott; Watanabe, Tetsuya; Warren, Harry P.; Harra, Louise K.;
Hara, Hirohisa; Tarbell, Theodore D.; Shine, Dick; Title, Alan M.;
Schrijver, Carolus J.; Tsuneta, Saku; Katsukawa, Yukio; Ichimoto,
Kiyoshi; Suematsu, Yoshinori; Shimizu, Toshifumi
Bibcode: 2007PASJ...59S.699H
Altcode: 2007arXiv0711.0487H
We use coordinated Hinode SOT/EIS observations that include
high-resolution magnetograms, chromospheric, and transition region
(TR) imaging, and TR/coronal spectra in a first test to study how
the dynamics of the TR are driven by the highly dynamic photospheric
magnetic fields and the ubiquitous chromospheric waves. Initial
analysis shows that these connections are quite subtle and require a
combination of techniques including magnetic field extrapolations,
frequency-filtered time-series, and comparisons with synthetic
chromospheric and TR images from advanced 3D numerical simulations. As a
first result, we find signatures of magnetic flux emergence as well as
3 and 5mHz wave power above regions of enhanced photospheric magnetic
field in both chromospheric, transition region, and coronal emission.
Title: Formation of Moving Magnetic Features and Penumbral Magnetic
Fields with Hinode/SOT
Authors: Kubo, Masahito; Ichimoto, Kiyoshi; Shimizu, Toshifumi;
Tsuneta, Saku; Suematsu, Yoshinori; Katsukawa, Yukio; Nagata,
Shin'ichi; Tarbell, Theodore D.; Shine, Richard A.; Title, Alan M.;
Frank, Zoe A.; Lites, Bruce; Elmore, David
Bibcode: 2007PASJ...59S.607K
Altcode: 2007arXiv0709.1853K
Vector magnetic fields of moving magnetic features (MMFs) were well
observed with the Solar Optical Telescope (SOT) aboard the Hinode
satellite. We focused on the evolution of three MMFs with the SOT in
this study. We found that an MMF having relatively vertical fields
with the same polarity as the sunspot was detached from the penumbra
around the granules appearing in the outer penumbra. This suggests
that granular motions in the outer penumbra are responsible for
disintegration of the sunspot. Two MMFs with polarity opposite to
the sunspot are located around the outer edge of horizontal fields
extending from the penumbra. This is evidence that the MMFs with
polarity opposite to the sunspot are the prolongation of penumbral
horizontal fields. Redshifts larger than the sonic velocity in the
photosphere are detected for some of the MMFs with polarity opposite
to the sunspot.
Title: A Tale of Two Spicules: The Impact of Spicules on the Magnetic
Chromosphere
Authors: de Pontieu, Bart; McIntosh, Scott; Hansteen, Viggo H.;
Carlsson, Mats; Schrijver, Carolus J.; Tarbell, Theodore D.; Title,
Alan M.; Shine, Richard A.; Suematsu, Yoshinori; Tsuneta, Saku;
Katsukawa, Yukio; Ichimoto, Kiyoshi; Shimizu, Toshifumi; Nagata,
Shin'ichi
Bibcode: 2007PASJ...59S.655D
Altcode: 2007arXiv0710.2934D
We use high-resolution observations of the Sun in CaIIH (3968Å)
from the Solar Optical Telescope on Hinode to show that there are
at least two types of spicules that dominate the structure of the
magnetic solar chromosphere. Both types are tied to the relentless
magnetoconvective driving in the photosphere, but have very different
dynamic properties. ``Type-I'' spicules are driven by shock waves
that form when global oscillations and convective flows leak into
the upper atmosphere along magnetic field lines on 3--7minute
timescales. ``Type-II'' spicules are much more dynamic: they form
rapidly (in ∼ 10s), are very thin (≤ 200 km wide), have lifetimes
of 10-150s (at any one height), and seem to be rapidly heated to
(at least) transition region temperatures, sending material through
the chromosphere at speeds of order 50--150kms-1. The
properties of Type II spicules suggest a formation process that is
a consequence of magnetic reconnection, typically in the vicinity
of magnetic flux concentrations in plage and network. Both types of
spicules are observed to carry Alfvén waves with significant amplitudes
of order 20kms-1.
Title: What are 'Faculae'?
Authors: Berger, T. E.; Title, A. M.; Tarbell, T.; Rouppe van der
Voort, L.; Löfdahl, M. G.; Scharmer, G. B.
Bibcode: 2007ASPC..369..103B
Altcode:
We present very high resolution filtergram and magnetogram observations
of solar faculae taken at the Swedish 1-meter Solar Telescope (SST)
on La Palma. Three datasets with average line-of-sight angles of 16,
34, and 53 degrees are analyzed. The average radial extent of faculae is
at least 400~km. In addition we find that contrast versus magnetic flux
density is nearly constant for faculae at a given disk position. These
facts and the high resolution images and movies reveal that faculae are
not the interiors of small flux tubes - they are granules seen through
the transparency caused by groups of magnetic elements or micropores
``in front of'' the granules. Previous results which show a strong
dependency of facular contrast on magnetic flux density were caused
by bin-averaging of lower resolution data leading to a mixture of
the signal from bright facular walls and the associated intergranular
lanes and micropores. The findings are relevant to studies of total
solar irradiance (TSI) that use facular contrast as a function of disk
position and magnetic field in order to model the increase in TSI with
increasing sunspot activity.
Title: The Quiet Sun Magnetic Fields
Authors: Title, A. M.
Bibcode: 2007ASPC..369..125T
Altcode:
The Quiet Sun is a misnomer. The constant emergence of new flux that
covers virtual all of the solar surface plays a major role in the
heating of the chromosphere, transtion region, and corona. The past
decade of research has revealed may of its properties, but has raise
many new questions about its nature and effects. The paper reviews
the status of our understanding of Quiet Sun and points out research
areas that the Solar Optical Telescope on Solar B can make major
contributions.
Title: Performance Characteristics of the Solar-B Spectro-Polarimeter
Authors: Lites, B. W.; Elmore, D. F.; Streander, K. V.; Hoffmann,
C. M.; Tarbell, T. D.; Title, A. M.; Shine, R. A.; Ichimoto, K.;
Tsuneta, S.; Shimizu, T.; Suematsu, Y.
Bibcode: 2007ASPC..369...55L
Altcode:
The Focal Plane Package (FPP) of the Solar Optical Telescope (SOT)
includes the first precision Spectro-Polarimeter (SP) for solar space
observations. The FPP/SP will provide high precision measures of
the vector magnetic field in the solar photosphere. Here we present
some as-built performance specifications for the entire system of
telescope + polarimeter. The FPP-SP system represents significant
gains in several aspects over existing spectro-polarimetric systems;
notably, angular resolution, polarimetric accuracy, spectral purity,
and most importantly, temporal continuity of stable, high angular
resolution. In this short summary of the poster, a few of the
performance characteristics of the SP are presented.
Title: Vector Spectropolarimetry of Dark-cored Penumbral Filaments
with Hinode
Authors: Bellot Rubio, L. R.; Tsuneta, S.; Ichimoto, K.; Katsukawa,
Y.; Lites, B. W.; Nagata, S.; Shimizu, T.; Shine, R. A.; Suematsu,
Y.; Tarbell, T. D.; Title, A. M.; del Toro Iniesta, J. C.
Bibcode: 2007ApJ...668L..91B
Altcode: 2007arXiv0708.2791B
We present spectropolarimetric measurements of dark-cored penumbral
filaments taken with Hinode at a resolution of 0.3". Our observations
demonstrate that dark-cored filaments are more prominent in polarized
light than in continuum intensity. Far from disk center, the Stokes
profiles emerging from these structures are very asymmetric and show
evidence for magnetic fields of different inclinations along the
line of sight, together with strong Evershed flows of at least 6-7 km
s-1. In sunspots closer to disk center, dark-cored penumbral
filaments exhibit regular Stokes profiles with little asymmetries due
to the vanishing line-of-sight component of the horizontal Evershed
flow. An inversion of the observed spectra indicates that the magnetic
field is weaker and more inclined in the dark cores as compared with
the surrounding bright structures. This is compatible with the idea
that dark-cored filaments are the manifestation of flux tubes carrying
hot Evershed flows.
Title: Emergence of Small-Scale Magnetic Loops in the Quiet-Sun
Internetwork
Authors: Centeno, R.; Socas-Navarro, H.; Lites, B.; Kubo, M.; Frank,
Z.; Shine, R.; Tarbell, T.; Title, A.; Ichimoto, K.; Tsuneta, S.;
Katsukawa, Y.; Suematsu, Y.; Shimizu, T.; Nagata, S.
Bibcode: 2007ApJ...666L.137C
Altcode: 2007arXiv0708.0844C
We study the emergence of magnetic flux at very small spatial
scales (less than 2") in the quiet-Sun internetwork. To this aim,
a time series of spectropolarimetric maps was taken at disk center
using the instrument SP/SOT on board Hinode. The LTE inversion of
the full Stokes vector measured in the Fe I 6301 and 6302 Å lines
allows us to retrieve the magnetic flux and topology in the region
of study. In the example presented here, the magnetic flux emerges
within a granular structure. The horizontal magnetic field appears
prior to any significant amount of vertical field. As time goes on,
the traces of the horizontal field disappear, while the vertical dipoles
drift-carried by the plasma motions-toward the surrounding intergranular
lanes. These events take place within typical granulation timescales.
Title: The magnetic field and its effects on the solar atmosphere
in high resolution
Authors: Title, Alan M.
Bibcode: 2007HiA....14...30T
Altcode:
The Sun's magnetic field is produced throughout the solar interior;
it emerges and is dispersed by surface and subsurface flows, and then
expands above the surface to dominate the structure of the corona. To
resolve the effects of the magnetic field it is necessary to image
the interior and measure its rotation and flow systems; track the
responses of the magnetic fields to flows in the surface; and to follow
the evolution of structures in the corona. Because the Sun is dynamic
both high spatial and temporal resolution are essential. Because the
Sun's magnetic field effects encompass the entire spherical exterior,
the entire surface and outer atmosphere must be mapped. And because
the magnetic field is cyclic high-resolution observations must be
maintained over multiple cycles.
Title: The Hinode (Solar-B) Mission: An Overview
Authors: Kosugi, T.; Matsuzaki, K.; Sakao, T.; Shimizu, T.; Sone,
Y.; Tachikawa, S.; Hashimoto, T.; Minesugi, K.; Ohnishi, A.; Yamada,
T.; Tsuneta, S.; Hara, H.; Ichimoto, K.; Suematsu, Y.; Shimojo, M.;
Watanabe, T.; Shimada, S.; Davis, J. M.; Hill, L. D.; Owens, J. K.;
Title, A. M.; Culhane, J. L.; Harra, L. K.; Doschek, G. A.; Golub, L.
Bibcode: 2007SoPh..243....3K
Altcode:
The Hinode satellite (formerly Solar-B) of the Japan Aerospace
Exploration Agency's Institute of Space and Astronautical Science
(ISAS/JAXA) was successfully launched in September 2006. As the
successor to the Yohkoh mission, it aims to understand how magnetic
energy gets transferred from the photosphere to the upper atmosphere
and results in explosive energy releases. Hinode is an observatory
style mission, with all the instruments being designed and built to
work together to address the science aims. There are three instruments
onboard: the Solar Optical Telescope (SOT), the EUV Imaging Spectrometer
(EIS), and the X-Ray Telescope (XRT). This paper provides an overview
of the mission, detailing the satellite, the scientific payload, and
operations. It will conclude with discussions on how the international
science community can participate in the analysis of the mission data.
Title: Chromospheric Micro-jets Discovered Above Sunspot Penumbrae
Authors: Katsukawa, Yukio; Tsuneta, S.; Suematsu, Y.; Ichimoto, K.;
Shimizu, T.; Kubo, M.; Nagata, S.; Berger, T.; Tarbell, T.; Shine,
R.; Title, A.
Bibcode: 2007AAS...210.9413K
Altcode: 2007BAAS...39..219K
The Solar Optical Telescope (SOT) aboard HINODE allows us to observe
dynamical activities in the solar photosphere and the chromosphere
with high and stable image quality of 0.2 arcseconds. This superior
performance of SOT provides new findings of fine-scale transient
activities occurring in the chromosphere. In this paper, we report
discovery of fine-scale jet-like phenomena ubiquitously observed
above sunspot penumbrae. The jets are identified in image sequences
of a sunspot taken through a Ca II H line filter at 3968A. The Ca II
H line is sensitive to about 10^4 K plasma in the chromosphere. Their length is typically between 3000 and 10000km, and their
width is smaller than 500km. It is notable that their lifetime
is shorter than 1 minute. Those small spatial and temporal scale
possibly makes it difficult to identify the phenomena in existing
ground-based observations. The jets are easily identified when a
sunspot is located far from the disk center, and motion of the bright
features suggests that mass is erupted from lower chromosphere to upper
atmosphere. Velocities of the motion are estimated to be 50 to 100 km/s
from their lateral motion of intensity patterns. The velocities are much
faster than sound speeds in the chromosphere. A possible cause of such
high-speed jets is magnetic reconnection at the lower chromosphere
resulted from fluted magnetic configuration in penumbrae which is
suggested by vector magnetic field measurements in the photosphere.
Title: Helio-informatics: Preparing For The Future Of Heliophysics
Research.
Authors: Schrijver, Carolus J.; Hurlburt, N. E.; Cheung, M. C.; Title,
A. M.; Delouille, V.; Hochedez, J.; Berghmans, D.
Bibcode: 2007AAS...210.2514S
Altcode: 2007BAAS...39..133S
The rapidly growing data volumes for space- and ground-based
observatories for Sun and heliosphere will soon make it impractical,
costly, and perhaps effectively impossible for researchers to download
and locally inspect substantial portions of the data archives. By
the end of 2008, for example, the Solar Dynamics Observatory will
downlink over 2TB/day of compressed data; such a large volume would
readily saturate internet connections to the archive site if it were
exported to a handful of researchers around the world. We envision a
revolution in research methodology towards a mode in which researchers
run autonomous event-finding algorithms at a primary data archive in
order to pre-select relatively small subsets of the data that can
subsequently be inspected and analyzed in detail at a researcher's
home institution. Teams from the SDO, Hinode, STEREO, and TRACE
missions are developing the infrastructure that is needed to make this
into a useful research tool: we are (1) defining standardized event
attributes compatible with the Virtual Observatory and EGSO concepts,
(2) developing a knowledge base supported by a web-based tool for
compound queries based on the contents of solar and heliospheric
observations, and (3) assembling a group of researchers who are
interested in helping us develop a prototype system while beta-testing
it in real scientific studies. We invite you to contact us (a) if you
have feature-finding algorithms that you would like to see applied to
existing data archives, (b) if you would like to contribute expertise
in developing the knowledge-base system, or (c) if you would like
to participate in the testing of the system for scientific use. More
information on our plans, target dates, and contact information can
be found at http://www.lmsal.com/helio-informatics/hpkb/. The
helio-informatics project is being developed with support from
the HINODE/SOT (NNM07AA01C), SDO/AIA (NNG04EA00C), STEREO/SECCHI
(N00173-02-C-2035), and TRACE (NAS5-38099) science investigations.
Title: Magnetic Patches in Internetwork Quiet Sun
Authors: De Wijn, Alfred; Lites, B.; Berger, T.; Shine, R.; Title,
A.; Katsukawa, Y.; Tsuneta, S.; Suematsu, Y.; Shimizu, T.; Hinode Team
Bibcode: 2007AAS...210.9412D
Altcode: 2007BAAS...39Q.219D
We study strong flux elements in the quiet sun in the context of
the nature of quiet-sun magnetism, its coupling to chromospheric,
transition-region and coronal fields, and the nature of a local
turbulent dynamo. Strong, kilogauss flux elements show up intermittently
as small bright points in G-band and Ca II H images. Although
bright points have been extensively studied in the magnetic network,
internetwork magnetism has only come under scrutiny in recent years. A
full spectrum of field strengths seems to be ubiquitously present in
the internetwork at small spatial scales, with the stronger elements
residing in intergranular lanes. De Wijn et al. (2005) found that bright
points in quiet sun internetwork areas appear recurrently with varying
intensity and horizontal motion within long-lived patches that outline
cell patterns on mesogranular scales. They estimate that the "magnetic
patches" have a mean lifetime of nine hours, much longer than granular
timescales. We use multi-hour sequences of G-band and Ca II H images
as well as magnetograms recorded by the Hinode satellite to follow up
on their results. The larger field of view, the longer sequences, the
addition of magnetograms, and the absence of atmospheric seeing allows
us to better constrain the patch lifetime, to provide much improved
statistics on IBP lifetime, to compare IBPs to network bright points,
and to study field polarity of IBPs in patches and between nearby
patches. Hinode is an international project supported by JAXA,
NASA, PPARC and ESA. We are grateful to the Hinode team for all their
efforts in the design, build and operation of the mission.
Title: High Resolution Observation of Spicules in Ca II H with
Hinode/SOT
Authors: Suematsu, Yoshinori; Katsukawa, Y.; Ichimoto, K.; Tsuneta, S.;
Okamoto, T.; Nagata, S.; Shimizu, T.; Tarbell, T.; Shine, R.; Title, A.
Bibcode: 2007AAS...210.9411S
Altcode: 2007BAAS...39..219S
High cadence observation with a Ca II H broadband filtergraph
(passband of 0.25 nm) of the Solar Optical Telescope (SOT) aboard
HINODE has revealed dynamical nature of solar limb spicules. Thanks to a
diffraction-limited and low-scattered light property of the instrument,
we can track the detailed evolution of individual spicules for the first
time with a spatial resolution of 0.2 arcsec. The spicules in Ca II
H are typically several arcsec tall and have multi-thread structure;
each threads are a few tenth of arcsec wide. It should be stressed
that most spicules do not show a simple up-and-down motion along a
rigid path line. They start with bright structure emanating from Ca II
H bright region, get widen and diffused with time and ascent, showing
expansion with lateral or even helical motion in tall events. Small and
short lived spicules tend to fade out after ascent. We will present
new findings of spicule dynamics in different magnetic environments
and discuss about long standing controversy of its motion and evolution.
Title: Hinode/SOT Observation of Fine Structure of the Evershed Flow
Authors: Ichimoto, Kiyoshi; Suematsu, Y.; Tsuneta, S.; Katsukawa, Y.;
Shimojo, M.; Kubo, M.; Shimizu, T.; Shine, R.; Tarbell, T.; Title,
A.; Lites, B.; Elmore, D.; Yokoyama, T.; Nagaka, S.
Bibcode: 2007AAS...210.9408I
Altcode: 2007BAAS...39..218I
Small scale structure of the Evershed effect was studied using the
Spectropolarimeter (SP) and Broadband Filter Imager (BFI) of SOT aboard
Hinode. SP maps and high cadence continuum images of BFI coverting
entire sunspots are used to investigate the spatial distribution of
the flow field, brightness and magnetic fields. It is revealed that the
Evershed flow starts at the front edge of inwardly migrating penumbral
grains with an upward velocity component and turns to nearly holizontal
flow preferentially in dark lanes (or dark core of filaments) of the
penumbra. Our results are in general agreement with the well known
uncombed penumbral concept in which the Evershed flow takes place
in nearly holizontal field channels. We discovered a number of tiny
elongated regions in deep photosphere in which there is an obvious
upward motion of 1-1.5km/s distributing over the penumbra. They
could be identified as the 'foot points' of the individual Evershed
flow channels. Cross-correlation among the flow speed, intensity,
magnetic field strength and inclination, and distribution of string
down flows in and around the penumbra will also be discussed.
Title: Observational Evidence For The Ubiquity Of Strong Alfven
Waves In The Magnetized Chromosphere
Authors: De Pontieu, Bart; McIntosh, S. W.; Carlsson, M.; Hansteen,
V. H.; Schrijver, C. J.; Tarbell, T. D.; Title, A.; SOT Team
Bibcode: 2007AAS...210.9415D
Altcode: 2007BAAS...39R.219D
Hinode/SOT Ca II broadband observations show that Alfven waves with
significant amplitudes of order 10-20 km/s and periods of 150-300 s are
extremely ubiquitous in the magnetized middle to upper chromosphere. Our
observations focus on spicules at the limb, and straw-like features
associated with network and plage on the disk. We find that the
weak straw-like features and most spicules all undergo significant
transverse motions that are driven by Alfven waves. These waves are
seen to propagate both up- and downward, and may carry an energy flux
that is significant compared to both the local, coronal and solar wind
energy balance. We will provide estimates of the energy flux carried
by these waves, and will compare our observations with Alfven waves
that are observed in 3D numerical simulations that include advanced
radiative transfer treatment for the chromosphere. This work was
supported by NASA contract NNM07AA01C.
Title: A Tale of Two Spicules
Authors: McIntosh, Scott W.; De Pontieu, B.; Carlsson, M.; Hansteen,
V. H.; Schrijver, C. J.; Tarbell, T. D.; Title, A. M.; SOT Team
Bibcode: 2007AAS...210.9414M
Altcode: 2007BAAS...39..219M
Hinode/SOT Ca II broadband images and movies show that there are
several different types of spicules at the limb. These different
types are distinguished by dynamics on different timescales. The
first type involves up- and downward motion on timescales of 3-5
minutes. The dynamics of these spicules are very similar to those of
fibrils and mottles as observed on the disk. Recent work suggests that
these are driven by slow-mode magnetoacoustic shocks that form when
convective flows and global oscillations leak into the chromosphere
along magnetic flux tubes. The second type is much more dynamic with
typical lifetimes of 10-60 s. These spicules are characterized by
sudden appearance and disappearance that may be indicative of rapid
heating to TR temperatures. We will describe the properties of these
spicules in various magnetic environments (coronal hole, quiet Sun,
active region) and study the possible role of reconnection in driving
the second type of spicules. In addition, we will perform detailed
comparisons of these different types of jets with synthetic Ca images
derived from advanced 3D numerical simulations that encompass the
convection zone up through the corona.
Title: Magnetic Flux Emergence In The Quiet Sun Photosphere
Authors: Centeno, Rebecca; Lites, B.; Socas-Navarro, H.; Frank,
Z.; Shine, R.; Tarbell, T.; Title, A.; Ichimoto, K.; Tsuneta, S.;
Katsukawa, Y.; Suematsu, Y.; Kubo, M.; Shimizu, T.
Bibcode: 2007AAS...210.9406C
Altcode: 2007BAAS...39..218C
We study the emergence of magnetic flux at very small spacial scales
(less than 1 arcsec) in the quiet Sun internetwork. To this aim, several
time series of spectropolarimetric maps were taken at disk center using
the instrument SP/SOT on board Hinode. The LTE inversion of the full
Stokes vector measured in the Fe I 6301 and 6302 lines will allow us
to retrieve the magnetic flux and topology in the region of study. We
find that the magnetic flux emerges typically within the granular
structures. In many cases, the horizontal magnetic field appears
prior to any significant amount of vertical field. As time goes on,
the traces of the horizontal field dissapear while the the vertical
dipoles drift -carried by the plasma motions- towards the surrounding
intergranular lanes. Sometimes they stay trapped there for a while
but they eventually either disappear by disgregation/cancelation
or agregate to other magnetic field concentrations giving rise to
larger flux elements. The time scale of these events is of the order
of 10-20 minutes.
Title: Formation of Moving Magnetic Features and Penumbral Magnetic
Fields
Authors: Kubo, Masahito; Ichimoto, K.; Shimizu, T.; Tsuneta, S.;
Suematsu, Y.; Katsukawa, Y.; Nagata, S.; Lites, B. W.; Frank, Z.;
Tarbell, T. D.; Shine, R. A.; Title, A. M.
Bibcode: 2007AAS...210.9410K
Altcode: 2007BAAS...39..218K
We investigate the formation process of Moving Magnetic Features
(MMFs) observed with Hinode/SOT. Moving magnetic features are small
magnetic elements moving outward in the moat region surrounding
mature sunspots. We derive vector magnetic fields of MMFs around
simple sunspots near the disk center. Most of MMFs with polarity
opposite to the sunspot have large redshift around the penumbral outer
boundary. We find that some of them have Doppler velocities of about
10 km/s and such large Doppler motion is observed only in the Stokes
V profile. The Stokes Q and U profiles in the same pixel do not have
any significant Doppler motions. Horizontal magnetic fields of the
penumbra frequently extend to the moat region and the MMFs having
horizontal fields with polarity same as the sunspot are formed. The
MMFs with polarity opposite to the sunspot appear around the outer
edge of the extending penumbral fields. We also find penumbral spines,
which have more vertical magnetic fields than the surroundings, branch
off at their outer edge and MMFs having relatively vertical fields
with polarity same as the sunspot are detached from the outer edge
of the branch. The branch of penumbral spine is formed when granular
cells in the moat region go into the penumbra.
Title: Ubiquitous Horizontal Magnetic Fields in the Quiet Solar
Photosphere as Revealed by HINODE Meaurements
Authors: Lites, Bruce W.; Socas Navarro, H.; Berger, T.; Frank,
Z.; Shine, R.; Tarbell, T.; Title, A.; Ichimoto, K.; Katsukawa,
Y.; Tsuneta, S.; Suematsu, Y.; Kubo, M.; Shimizu, T.; Nagata, S.;
Hinode Team
Bibcode: 2007AAS...210.6303L
Altcode: 2007BAAS...39..171L
Measurements with the HINODE Spectro-Polarimeter (SP) of the quiet
Sun allow characterization of the weak, mixed-polarity magnetic
flux at the highest angular resolution to date (0.3"), and with good
polarimetric sensitivity(0.025% relative to the continuum). The image
stabilization of the HINODE spacecraft allows long integrations with
degradation of the image quality only by the evolution of the solar
granulation. From the Stokes V profile measurements we find an average
solar "Apparent Flux Density" of 14 Mx cm-2, with significant Stokes V
signals at every position on the disk at all times. However, there are
patches of meso-granular size (5-15") where the flux is very weak. At
this high sensitivity, transverse fields produce measurable Stokes
Q,U linear polarization signals over a majority of the area, with
apparent transverse flux densities in the internetwork significantly
larger than the corresponding longitudinal flux densities. When viewed
at the center of the solar disk, the Stokes V signals (longitudinal
fields) show a preference for occurrence in the intergranular lanes,
and the Q,U signals occur preferably over the granule interiors,
but neither association is exclusive. Hinode is an international
project supported by JAXA, NASA, PPARC and ESA. We are grateful to the
Hinode team for all their efforts in the design, build and operation
of the mission.
Title: First Results from the Solar Optical Telescope on Hinode
Authors: Title, Alan M.; Tarbell, T.; Tsuneta, S.; SOT Team
Bibcode: 2007AAS...210.6301T
Altcode: 2007BAAS...39..171T
The Solar Optical Telescope (SOT) is a joint project of the National
Observatory of Japan and the Lockheed Martin Solar and Astrophysical
Laboratory. SOT consists of a 50 cm Gregorian telescope optimized to
reduce instrumental polarization and the Focal Plane Package (FPP). FPP
contains a version of the Advanced Stokes Polarimeters developed by
the High Altitude Observatory, a broadband filter system, and a tunable
birefringent filter. A correlation tracker in the FPP sends a control
signal to an active mirror in the telescope. Both the telescope and the
active mirror were developed by the National Astronomical Observatory
of Japan. The correlation tracking system reduces image motion in the
focal planes to +/- 0.02 arcseconds. The diffraction limited performance
of the SOT coupled with large format CCD’s and high data rates have
allowed the construction of high resolution line of sight and vector
magnetograms and imaging of phenomena on solar surface and off the
solar limb. This data are providing new insights into the processes
of flux emergence and disappearance from the scale of granulation to
active regions. High cadence observations of filaments, prominences,
and spicules have revealed surprising evolutionary features that include
alfven waves, current systems, and rapid reconnection. Movies of many
of these phenomena will be shown.
Title: Attempt to detect Aflven waves with Solar Optical Telescope
aboard Hinode
Authors: Tsuneta, Saku; Suematsu, Y.; Ichimoto, K.; Katsukawa, Y.;
Shimizu, T.; Nagata, S.; Orozco Suárez, D.; Lites, B.; Shine, D.;
Tarbell, T.; Title, A.
Bibcode: 2007AAS...210.9428T
Altcode: 2007BAAS...39..222T
Flux tube on the sun may carry linear and torsional Alfven waves
generated by photospheric motion. Photospheric motion of 2 km/s would
provide magnetic fluctuation of 40G for 1KG tube and for the Alfven
speed of 50km/s. This may be close to the detection limit of the Stokes
Q and U signals for flux tubes located in the sun center. However,
for flux tubes located near the limb, the fluctuation would be seen in
the Stokes V signal, and can be detectable. We also may be able
to confirm the 90 degree phase shift between magnetic fluctuation and
velocity fluctuation, which is easier to observe for flux tubes near
the limb. Detection of waves would be important in terms of coronal
heating and solar wind acceleration. An attempt to detect waves along
flux tubes will be reported.
Title: Discovery Of Small-scale Horizontal Magnetic Structures On
The Solar Photosphere
Authors: Ishikawa, Ryohko; Tsuneta, S.; Suematsu, Y.; Ichimoto, K.;
Katsukawa, Y.; Nagata, S.; Ishobe, H.; Tarbell, T.; Lites, B. W.;
Title, A.
Bibcode: 2007AAS...210.9404I
Altcode: 2007BAAS...39..217I
We discover two different types of episodes on the appearance
of horizontal magnetic fields with Solar Optical Telescope aboard
Hinode. The first episode is an emergence of strong thin horizontal
magnetic fields associated with separating vertical components on
both ends. Its size is about two granules. We also detect strong area
asymmetry of the environment Stokes Vprofile for the bout 8 minutes
before the first emergence of the horizontal component. One of the
footpoints has very strong downflows (several km/s), while the region
with strong linear polarization signal has small blue shift, indicating
an upward-moving horizontal flux. The second episode appears to be
more ubiquitous. Linear polarization signals appear inside granules (not
in inter-granules). Their size is smaller than granules, and lifetime
is longer than several minutes. We will summarize the nature of the
two types of the horizontal magnetic fluxes, and discuss their origin.
Title: Hinode/SOT Observations of Sunspot Penumbral Dynamics and
Evolution
Authors: Shine, Richard A.; Hagenaar, M.; Tarbell, T.; Title, A.;
Lites, B.; Ichimoto, K.; Tsuneta, S.; Katsakawa, Y.; Suematsu, Y.;
Nagata, S.; Kubo, M.; Shimizu, T.
Bibcode: 2007AAS...210.9407S
Altcode: 2007BAAS...39..218S
The Solar Optical Telescope (SOT) on the Hinode satellite (launched
October 2006) has obtained long and nearly continuous time series of
several large sunspots including those in NOAA AR's 10923, 10925,
and 10930. Here we use high resolution movies taken primarily with
the broad band Ca II (396.8nm) and G band (430.5nm) channels and
magnetograms taken with the 630.2nm narrow band channel to study
the details and short term evolution of penumbral fine structures
as well as the long term evolution of the sunspots. We compute flow
maps and use space/time slices to track motions of Evershed clouds,
penumbral grains, and visualize oscillations. The data contain examples
of penumbral formation and disintegration including "orphan" penumbra
(i.e., penumbra without an obvious umbra). There is also an interesting
instance of "colliding" penumbra in AR 10930 as two sunspots of opposite
polarity converged. The zone of apparent shear was associated with
several flares. This work was supported by NASA contract NNM07AA01C
Title: Magnetic Landscape Of Solar Polar Region With Solar Optical
Telescope Aboard Hinode
Authors: Tsuneta, Saku; Suematsu, Y.; Ichimoto, K.; Shimizu, T.;
Katsukawa, Y.; Nagata, S.; Orozco Suárez, D.; Lites, B.; Shine, D.;
Tarbell, T.; Title, A.
Bibcode: 2007AAS...210.9405T
Altcode: 2007BAAS...39..218T
Solar polar region is the final destination for remnant magnetic
fields due to meridional flow and granular diffusion, and is very
important for the global solar dynamo. Hinode satellite carried out
high-resolution spectro-polarimetric observations for the Northern
pole on 2006 November 22 as a part of its performance verification
program. We find ubiquitous isolated (positive and negative) patches
in the Stokes V map (i.e. fields horizontal to local surface) all over
the Arctic circle. The Q (vertical to local surface) map indicates
scattered vertical flux tubes, which have bipolar feature in the U and
V maps. This suggests canopy-like structure of the strong isolated flux
tubes. This will be compared with equatorial landscape with similar
distance from the sun center. Strong flux tube and weaker ubiquitous
horizontal fields as represented by Stokes V would have implication
to the current understanding of the global and local dynamo.
Title: Anticorrelation between Moving Magnetic Features and Coronal
Loop Formation
Authors: Ryutova, M. P.; Hagenaar, H.; Title, A.
Bibcode: 2007ApJ...656L..45R
Altcode:
We study a possible connection of moving magnetic features (MMFs)
and the overlying atmosphere using several sets of multiwavelength
observations of sunspot areas from the photosphere to the corona. We
find that as a collective phenomenon, very intense MMF formation
anticorrelates with the presence of large-scale ``stable'' coronal
loops: such loops are rooted at the side of sunspots with no or few
MMFs rather than at the side of the penumbra/moat highly populated by
MMFs. Conjectures to help understand the observed correlation between
the preferable site of coronal loops and the deficiency of MMFs are
discussed.
Title: SUNRISE: High resolution UV/VIS observations of the Sun from
the stratosphere
Authors: Gandorfer, A. M.; Solanki, S. K.; Barthol, P.; Martínez
Pillet, V.; Schmidt, W.; Title, A. M.; Knölker, M.
Bibcode: 2007msfa.conf...69G
Altcode:
SUNRISE is an international project for the development, construction,
and operation of a balloon-borne solar telescope with an aperture
of 1 m, working in the UV/VIS spectral domain. The main scientific
goal of SUNRISE is to understand the structure and dynamics of the
magnetic field in the atmosphere of the Sun. SUNRISE will provide
near diffraction-limited images of the photosphere and chromosphere
with an unpredecented resolution down to 35 km on the solar surface at
wavelengths around 220 nm. The focal-plane instrumentation consists of a
polarization sensitive spectrograph, a Fabry-Perot filter magnetograph,
and a phase-diverse filter imager working in the near UV. The first
stratospheric long-duration balloon flight of SUNRISE is planned in
summer 2009 from the Swedish ESRANGE station. SUNRISE is a joint project
of the German Max-Planck-Institut für Sonnensystemforschung (MPS),
Katlenburg-Lindau, with the Kiepenheuer-Institut für Sonnenphysik
(KIS), Freiburg, Germany, the High-Altitude Observatory (HAO), Boulder,
USA, the Lockheed-Martin Solar and Astrophysics Lab. (LMSAL), Palo
Alto, USA, and the Spanish IMaX consortium. In this paper we will
present a brief description of the scientific and technological aspects
of SUNRISE.
Title: Magnetic Field Diagnostic Capability of Solar-B/SOT:
Filtergraph Instrument
Authors: Ichimoto, K.; Suematsu, Y.; Shimizu, T.; Katsukawa, Y.;
Tsuneta, S.; Tarbell, T. D.; Shine, R. A.; Hoffmann, C. M.; Title,
A. M.; Lites, B. W.; Elmore, D. F.; Streander, K. V.
Bibcode: 2006ASPC..358..189I
Altcode:
The Narrowband Filter Instrument (NFI) of the Solar Optical Telescope
onboard Solar-B provides 2D magnetograms/Dopplergrams with a tunable
Lyot filter (width ∼ 0.1 Å) in 6 selected wavelength bands, and
spatial sampling of 0.08 arcsec/px. The Zeeman-effect sensitivity of
NFI and the detection limits of weak magnetic fields are evaluated for
2 photospheric and 3 chromospheric lines. Magnetic-field retrievability
from the NFI observables is studied using synthetic Stokes profiles
of Fe I 5250 Å. We find that, with optimized wavelength sampling at 4
positions, the inferred magnetic field is sufficiently accurate under
the hypothesis of constant magnetic field and velocity along the LOS.
Title: SUNRISE: high resolution UV/VIS observations of the Sun from
the stratosphere
Authors: Gandorfer, A. M.; Solanki, S. K.; Barthol, P.; Lites, B. W.;
Martínez Pillet, V.; Schmidt, W.; Soltau, D.; Title, A. M.
Bibcode: 2006SPIE.6267E..0SG
Altcode: 2006SPIE.6267E..25G
SUNRISE is an international project for the development, construction,
and operation of a balloon-borne solar telescope with an aperture
of 1 m, working in the UV/VIS spectral domain. The main scientific
goal of SUNRISE is to understand the structure and dynamics of the
magnetic field in the atmosphere of the Sun. SUNRISE will provide
near diffraction-limited images of the photosphere and chromosphere
with an unpredecented resolution down to 35 km on the solar surface at
wavelengths around 220 nm. The focal-plane instrumentation consists of a
polarization sensitive spectrograph, a Fabry-Perot filter magnetograph,
and a phase-diverse filter imager working in the near UV. The first
stratospheric long-duration balloon flight of SUNRISE is planned
in Summer 2009 from the swedish ESRANGE station. SUNRISE is a joint
project of the german Max-Planck-Institut fur Sonnensystemforschung
(MPS), Katlenburg-Lindau, with the Kiepenheuer-Institut fur Sonnenphysik
(KIS), Freiburg, Germany, the High-Altitude Observatory (HAO), Boulder,
USA, the Lockheed-Martin Solar and Astrophysics Lab. (LMSAL), Palo Alto,
USA, and the spanish IMaX consortium. In this paper we will present
an actual update on the mission and give a brief description of its
scientific and technological aspects.
Title: The Atmospheric Imaging Assembly (AIA) for the Solar Dynamics
Observatory
Authors: Smith, Peter L.; Golub, L.; Bookbinder, J. A.; Reid, P. B.;
Deluca, E. E.; Cheimets, P. N.; Podgorski, W. A.; Title, A. M.; Lemen,
J. R.; Boerner, P. F.; SAO, Science, and LMSAL Engineering Teams
Bibcode: 2006SPD....37.0119S
Altcode: 2006BAAS...38Q.218S
The Atmospheric Imaging Assembly (AIA) is being developed for the
Solar Dynamics Observatory (SDO), which is designed to study the
Sun as part of NASA's Living With a Star program. AIA comprises
four normal-incidence telescopes with multilayer-coated optics;
entrance-aperture and focal-plane filters limit the bandpasses. Solar
radiation from the upper solar atmosphere at six wavelengths
corresponding to temperatures between 6.3×105 and
1.5×107 K [Fe IX (171 Å) Fe XII, XXIV (193 Å) Fe XIV
(211 Å) Fe XVI (335 Å) Fe XVIII (94 Å) and Fe XX, XXIII (131 Å)]
will be recorded with high spatial resolution (0.6 arcsec pixels). Other
channels enable observations of the chromosphere (He II 304 Å C IV
1550 Å) and the photosphere. Each telescope contains a 4096 x 4096
CCD camera system and has a 41 arcmin field of view. AIA will return 8
full-solar-disk images every 10 s. The 5-year SDO mission is scheduled
to launch in late 2008. The imaging performance of the telescopes,
which are being provided by the Smithsonian Astrophysical Observatory,
and performance of the multilayer coatings, which are responsible for
the large effective area of AIA, will be discussed in the context of
AIA science goals.
Title: The Atmospheric Imaging Assembly on the Solar Dynamics
Observatory
Authors: Title, Alan M.; AIA Team
Bibcode: 2006SPD....37.3605T
Altcode: 2006BAAS...38..261T
The Atmospheric Imaging Assembly (AIA) on SDO will provide revolutionary
coverage of the entire visible solar hemisphere, observed from
photospheric to coronal temperatures, at 1-arcsecond resolution,
with a characteristic cadence of 10 seconds for each channel. The
AIA comprises four dual normal-incidence telescopes that enable it to
cycle through a set of EUV channels centered on strong emission lines
of iron (ranging from Fe IX through XXIII) and helium (304A), plus
two UV channels near 1600A and a broad band visible channel. Combined
with the (vector-)magnetic imagery from SDO/HMI, the AIA observations
will significantly further our understanding of the dynamics of
the magnetic field in the solar atmosphere and heliosphere, both in
quiescent and eruptive stages. The comprehensive thermal coverage of
the corona will open new avenues of study for coronal energetics and
seismology, which will benefit from the excellent calibration against
the SDO/EVE spectral irradiance measurements. The AIA data will be
easily accessible on the web, with a time delay that is expected
to be of the order of 15 minutes to 1 hour. Users will be able to
browse the data through summary web pages that are complemented by
a comprehensive metadata catalog. Data analysis will be supported
through the freely available SolarSoft libraries and through modules
in a flexible, evolving pipeline data analysis system to be operated
at the AIA-HMI Joint Science Operations Center. We plan to incorporate
feature recognition software, automated movie making, coronal field
modeling, and other supporting analysis software. We invite the broad
ILWS community to contact us with ideas to collaborate on any aspect
of the AIA Investigation. Details on the AIA instrument, the Science
Investigation, and related news can be found at http://aia.lmsal.com.
Title: SUNRISE: high-resolution UV/VIS observations of the Sun from
the stratosphere
Authors: Solanki, S. K.; Barthol, P.; Gandorfer, A.; Schüssler, M.;
Lites, B. W.; Martinez Pillet, V.; Schmidt, W.; Title, A. M.
Bibcode: 2006cosp...36.2416S
Altcode: 2006cosp.meet.2416S
SUNRISE is a balloon-borne solar telescope with an aperture of 1m
working in the UV VIS optical domain The main scientific goal of
SUNRISE is to study the structure and dynamics of the magnetic field
in the atmosphere of the Sun at high spatial resolution SUNRISE will
provide diffraction-limited images of the photosphere and chromosphere
with an unprecedented resolution down to 35km at wavelengths around
220nm Focal-plane instruments are a UV filter imager a Fabry-Perot
filter magnetograph and a spectrograph polarimeter Stratospheric
long-duration balloon flights of SUNRISE over the North Atlantic
and or Antarctica are planned SUNRISE is a joint project of the
Max-Planck-Institut fuer Sonnensystemforschung MPS Katlenburg-Lindau
with the Kiepenheuer-Institut fuer Sonnenphysik KIS Freiburg the
High-Altitude Observatory HAO Boulder the Lockheed-Martin Solar and
Astrophysics Lab LMSAL Palo Alto and the spanish IMaX consortium The
presentation will give an overview about the mission and a description
of the instrumentation now at the beginning of the hardware construction
phase
Title: The Atmospheric Imaging Assembly on the Solar Dynamics
Observatory
Authors: Title, A. M.; Hoeksema, J. T.; Schrijver, C. J.; Aia Team
Bibcode: 2006cosp...36.2600T
Altcode: 2006cosp.meet.2600T
The Atmospheric Imaging Assembly AIA on SDO will provide revolutionary
coverage of the entire visible solar hemisphere observed from
photospheric to coronal temperatures at 1-arcsecond resolution with a
characteristic cadence of 10 seconds for each channel The AIA comprises
four dual normal-incidence telescopes that enable it to cycle through
a set of EUV channels centered on strong emission lines of iron ranging
from Fe IX through XXIII and helium 304A plus two UV channels near 1600A
and a broad band visible channel Combined with the vector- magnetic
imagery from SDO HMI the AIA observations will significantly further
our understanding of the dynamics of the magnetic field in the solar
atmosphere and heliosphere both in quiescent and eruptive stages The
comprehensive thermal coverage of the corona will open new avenues of
study for coronal energetics and seismology which will benefit from
the excellent calibration against the SDO EVE spectral irradiance
measurements The AIA data will be easily accessible on the web with
a time delay that is expected to be of the order of 15 minutes to 1
hour Users will be able to browse the data through summary web pages
that are complemented by a comprehensive metadata catalog Data analysis
will be supported through the freely available SolarSoft libraries and
through modules in a flexible evolving pipeline data-analysis system
to be operated at the AIA-HMI Joint Science Operations Center We plan
to incorporate feature recognition software automated movie making
coronal field modeling
Title: The Nonpotentiality of Active-Region Coronae and the Dynamics
of the Photospheric Magnetic Field
Authors: Schrijver, Carolus J.; De Rosa, Marc L.; Title, Alan M.;
Metcalf, Thomas R.
Bibcode: 2005ApJ...628..501S
Altcode:
The magnetic field in the solar photosphere frequently carries strong
electric currents, even though the global coronal configuration often
resembles a potential field ringed by the heliospheric current sheet. To
understand this, we compare TRACE EUV images of active-region coronae
and potential-field source-surface extrapolations based on SOHO MDI
magnetograms for 95 active regions. We conclude that significant
nonpotentiality of the overall active-region coronal field occurs
(1) when new flux has emerged within or very near a region within
the last ~30 hr, resulting in complex polarity separation lines, or
(2) when rapidly evolving, opposite-polarity concentrations are in
contact at 4" resolution. If these criteria are met by more than 15%
of the region's flux, they correctly identify the (non) potentiality of
active-region coronae in 88% of the cases. Flares are found to occur
2.4 times more frequently in active regions with nonpotential coronae
than in near-potential regions, while their average X-ray peak flare
brightness is 3.3 times higher. We suggest that the currents associated
with coronal nonpotentiality have a characteristic growth and decay
timescale of ~10-30 hr. We find that shear flows drive enhanced flaring
or coronal nonpotentiality only if associated with complex and dynamic
flux emergence within the above timescale. We discuss the implications
of this finding for the modeling of the coronal-heliospheric coupling.
Title: Calibration and Tesing of the Tunable Filter on Solar B
Authors: Shine, R. A.; Title, A. M.; Tarbell, T. D.; Mitchell, K.;
Tavarez, L.; Rosenberg, W.
Bibcode: 2005AGUSMSP43A..04S
Altcode:
The tunable filter in the Focal Plane Package (FPP) on the Japanese
Solar B satellite, scheduled for launch in August 2006, was designed,
built, and tested at the Lockheed Martin Advanced Technology Center
(LMATC). It is an eight element wide field calcite filter (an improved
Lyot type) with a spectral resolution of about 100mÅ and a tuning range
of 11.87Å at 6302Å. Using 6 prefilters, it operates in bands covering
the 5172Å Fe I, 5250Å Fe I, 5576Å Fe I, 5896Å Na I, 6302Å Fe I,
and 6563Å H I lines. Here we describe the testing and calibrations
used to determine the tuning parameters as functions of temperature
and wavelength for the six bands. We also measure performance using
sunlight and laser sources in a standalone mode and integrated into
the FPP package. Images and derived magnetograms and Dopplergrams
using a low resolution solar image have also been obtained while
attached to the Solar B telescope and using a heliostat at the LMATC
in Palo Alto. In the course of this work we have also refined the
mathematical description for these types of filters, especially the
error terms that arise from residual misalignments. In particular,
we now believe we understand the intensity oscillations seen in this
and earlier Lyot tunable filters.
Title: The Atmospheric Imaging Assembly (AIA) investigation for the
NASA SDO mission
Authors: Lemen, J. R.; Title, A. M.; Golub, L.
Bibcode: 2005AGUSMSH43A..17L
Altcode:
The Atmospheric Imaging Assembly (AIA) is one of three science
investigations selected for the NASA Solar Dynamics Observatory, the
first mission in NASA's Living With a Star program that is designed to
study the Sun's influence on the Earth and the nearby environment. AIA
consists of four normal incidence telescopes with multilayer coated
optics. It records solar EUV emission with high spatial resolution
(0.6 arcsec pixels) at six wavelengths from iron ions in the solar
atmosphere at temperatures between 6.3 × 105 K and 15 × 106 K:
Fe IX (171Å); Fe XII,XXIV (193Å); Fe XIV (211 Å); Fe XVI (335Å);
Fe XVIII (94Å); and Fe XX,XXIII (131Å). Other wavelength channels
enable observations of the chromosphere (He II, 304Å; C IV) and the
photosphere. Each telescope contains a 16-Mpixel CCD/camera system and
has a 41 arcmin field of view. AIA will return 8 full solar-disk images
every 10 s, producing 2.2 Tbytes/day of data. The AIA investigation is
led by PI Alan Title (LMSAL) with major participation by the Harvard
Smithsonian Astrophysical Observatory, Montana State University, and
Stanford University. The SDO mission is scheduled for launch in 2008
and will have a nominal five year mission lifetime, but will carry
resources for at least ten years of mission operations.
Title: The Heating of Cool-Star Coronae: From Individual Loops to
Global Flux-Flux Scalings
Authors: Schrijver, Carolus J.; Title, Alan M.
Bibcode: 2005ApJ...619.1077S
Altcode:
We simulate surface field patterns for cool dwarf stars of widely
different levels of activity and estimate the associated global
coronal radiative losses. We find that the integrated X-ray
brightness of coronae of cool stars is relatively insensitive to
the patterns of their surface magnetic fields, and that the X-ray
flux is determined almost entirely by the magnetic flux through the
stellar surfaces. This reconciles potentially inconsistent findings
in the literature for the heating of solar and stellar coronae: solar
studies suggested that the heating flux density entering coronal loops
scales as FH=ɛ0Bβ/Lλ
(for a magnetic flux density B at the base of a loop of length L,
with β=1.0+/-0.3 and λ=1.0+/-0.5), whereas combined solar and
stellar data suggested that the X-ray flux density FX
from entire cool-star coronae depends only on the average magnetic
flux density <|ϕ|> through the stellar photospheres. We find
that the above two scalings are compatible because loop lengths and
base magnetic flux densities are essentially uncorrelated for the
global coronal loop ensemble and because the average loop lengths
differ much less from star to star for Sun-like stars of different
activity than the average base field strengths. We also explore the
scaling properties of the constant of proportionality ɛ0
for stars of significantly different surface gravity.
Title: Solar magnetic elements at 0.1 arcsec resolution. General
appearance and magnetic structure
Authors: Berger, T. E.; Rouppe van der Voort, L. H. M.; Löfdahl,
M. G.; Carlsson, M.; Fossum, A.; Hansteen, V. H.; Marthinussen, E.;
Title, A.; Scharmer, G.
Bibcode: 2004A&A...428..613B
Altcode:
New observations of solar magnetic elements in a remnant active region
plage near disk center are presented. The observations were obtained at
the recently commissioned Swedish 1-m Solar Telescope on La Palma. We
examine a single 430.5 nm G-band filtergram that resolves ∼70 km
(0.1 arcsec) structures and find new forms of magnetic structures
in this particular region. A cotemporal Ca II H-line image is used
to examine the low-chromosphere of network elements. A cotemporal Fe
I 630.25 nm magnetogram that resolves structures as small as 120 km
(0.18 arcsec) FWHM with a flux sensitivity of approximately 130 Mx
cm-2 quantifies the magnetic structure of the region. A
Ni I 676.8 nm Dopplergram establishes relative velocity patterns
associated with the network features with an accuracy of about 300 m
s-1. We find that magnetic flux in this region as seen in
both the magnetogram and the G-band image is typically structured into
larger, amorphous, ``ribbons'' which are not resolved into individual
flux tubes. The measured magnetic flux density in the ribbon structures
ranges from 300 to 1500 Mx cm-2, the higher values occurring
at localized concentrations embedded within the ribbons. The Dopplergram
indicates relative downflows associated with all magnetic elements
with some indication that higher downflows occur adjacent to the peak
magnetic flux location. The mean absolute magnetic flux density of the
remnant plage network is about 130 Mx cm-2; in the lowest
flux regions of the field-of-view, the mean absolute flux density is
approximately 60 Mx cm-2. Within these quiet regions we do
not find evidence of pervasive kilo-gauss strength magnetic elements
as seen in recent high resolution internetwork studies. In general,
the observations confirm recent 3-dimensional numerical simulations
which show that the magnetic field in high-density regions such as
plage is concentrated in complex structures that are not generally
composed of discrete magnetic flux tubes. Appendices are only
available in electronic form at http://www.edpsciences.org
Title: Recent Progress in High-Resolution Observations
Authors: Berger, T. E.; Title, A. M.
Bibcode: 2004ASPC..325...95B
Altcode:
We review recent optical observations of the solar photosphere and
chromosphere with an emphasis on those observations that attain
spatial resolution values below 0.25 arcsec. Results from the Dutch
Open Telescope (DOT) on La Palma, the Dunn Solar Telescope (DST)
on Sacramento Peak, and the Vacuum Tower Telescope (VTT) on Tenerife
are reviewed. Particular emphasis is placed on results from the newly
commissioned Swedish 1-meter Solar Telescope (SST) on La Palma following
our successful campaigns at this instrument in 2002 and 2003. The SST
with adaptive optics can now achieve 0.0 arcsec resolution imaging
of the Sun in multiple simultaneous wavelengths. Scientific findings
on the structure of sunspot penumbrae and lightbridges, small-scale
magnetic elements, and faculae at the limb are reviewed. The Lockheed
Solar Optical Universal Polarimeter (SOUP) birefringent tunable filter
at the SST produced 0.16 arcsec resolution magnetograms in the summer
of 2003 that have shed new light on the structure and dynamics of
small-scale magnetic fields in the solar photosphere.
Title: SUNRISE: high-resolution UV/VIS observations of the Sun from
the stratosphere
Authors: Gandorfer, Achim M.; Solanki, Sami K.; Schüssler, Manfred;
Curdt, Werner; Lites, Bruce W.; Martínez Pillet, Valentin; Schmidt,
Wolfgang; Title, Alan M.
Bibcode: 2004SPIE.5489..732G
Altcode:
SUNRISE is a balloon-borne solar telescope with an aperture of 1m,
working in the UV/VIS optical domain. The main scientific goal
of SUNRISE is to understand the structure and dynamics of the
magnetic field in the atmosphere of the Sun. SUNRISE will provide
diffraction-limited images of the photosphere and chromosphere with
an unpredecented resolution down to 35km at wavelengths around
220nm. Focal-plane instruments are a spectrograph/polarimeter,
a Fabry-Perot filter magnetograph, and a filter imager. The first
stratospheric long-duration balloon flight of SUNRISE over Antarctica
is planned in winter 2006/2007. SUNRISE is a joint project of the
Max-Planck-Institut fur Sonnensystemforschung (MPS), Katlenburg-Lindau,
with the Kiepenheuer-Institut für Sonnenphysik (KIS), Freiburg, the
High-Altitude Observatory (HAO), Boulder, the Lockheed-Martin Solar and
Astrophysics Lab. (LMSAL), Palo Alto, and the Instituto de Astrofisica
de Canarias, La Laguna, Tenerife. In this paper we will present an
overview on the mission and give a description of the instrumentation,
now, at the beginning of the hardware construction phase.
Title: Three-Dimensional Structure of the Active Region Photosphere
as Revealed by High Angular Resolution
Authors: Lites, B. W.; Scharmer, G. B.; Berger, T. E.; Title, A. M.
Bibcode: 2004SoPh..221...65L
Altcode:
Blue continuum images of active regions at ∼ 60° from the center
of the solar disk obtained with the new Swedish 1-m Solar Telescope
reveal heretofore unreported structure of the magnetized solar
atmosphere. Perhaps the most striking aspect of these images is
that, at an angular resolution of 0.12″, they show clearly the
three-dimensional structure of the photosphere. In particular,
the Wilson depression of the dark floors of pores is readily
apparent. Conversely, the segmented structure of light bridges running
through sunspots and pores reveal that light bridges are raised
above the dark surroundings. The geometry of light bridges permits
estimates of the height of their central (slightly darker) ridge:
typically in the range 200-450 km. These images also clearly show
that facular brightenings outside of sunspots and pores occur on the
disk-center side of those granules just limbward of intergranular lanes
that presumably harbor the associated plage magnetic flux. In many cases
the brightening extends 0.5″ or more over those granules. Furthermore,
a very thin, darker lane is often found just centerward of the facular
brightening. We speculate that this feature is the signature of cool
down flows that surround flux tubes in dynamical models. These newly
recognized observational aspects of photospheric magnetic fields
should provide valuable constraints for MHD models of the magnetized
photosphere, and examination of those models as viewed from oblique
angles is encouraged.
Title: Observations of solar magnetic elements with 0.1" resolution
Authors: Berger, T. E.; Rouppe van der Voort, L. H. M.; Lofdahl,
M. G.; Carlsson, M.; Fossum, A.; Hansteen, V. H.; Marthinussen, E.;
Title, A. M.; Scharmer, G.
Bibcode: 2004AAS...204.2005B
Altcode: 2004BAAS...36..686B
New observations of solar magnetic elements in a remnant active region
plage near disk center are presented. The observations were taken with
the Swedish 1-meter Solar Telescope on La Palma. We examine a single
430.5 nm G-band filtergram that resolves ∼70 km (0.''1) structures
and find new forms of magnetic structures in this particular region. A
simultaneous Ca II H-line image is used to examine the low-chromosphere
of network elements. A simultaneous Fe I 630.25 nm magnetogram
that resolves structures as small as 120 km (0.''18) FWHM with a
flux sensitivity of approximately 130 Mx cm-2 quantifies
the magnetic structure of the region. A Ni I 676.8 nm Dopplergram
establishes relative velocity patterns associated with the network
features with an accuracy of about 300 m s-1. Magnetic flux
in this region as seen in both the magnetogram and the G-band image
is typically structured into larger, amorphous, ``ribbons'' with a
wide range of flux density values, rather than isolated kilogauss
flux tubes. We also present filtergrams and magnetograms of magnetic
elements at the solar limb showing that solar faculae are resolved
into bright granular walls that appear to project 350 to 500 km above
the photosphere.
Title: Toward Understanding the Sun's Magnetic Fields and their
Effects
Authors: Title, Alan
Bibcode: 2004AIPC..703..163T
Altcode:
Developments in instrumentation, numerical simulations, and theory
are rapidly changing our view of solar magnetism. There are now
observations that show magnetic field emerging on all convective
scales. The emergence rate replaces the quiet Sun flux in less than 12
hours and even active region and sunspot fields are replaced in less
than a month. There is evidence for local dynamo action suggesting that
a bottom to a convection zone is not required for stellar magnetic
activity. It is now recognized that 3D magnetic reconnection is
fundamentally different from 2D. Time sequences of the one arc second
(1'' = 726 km) spatial resolution TRACE images show that the temperature
and density structure of the corona changes as fast as radiation and
conduction allow. Because adjacent loops are observed in a range of
temperatures that span at least 30,000 to 2,500,000 K, there is a inter
mixture of temperatures regimes throughout the corona. Consequently,
there is no line of sight through the corona that can be characterized
by a single temperature and density. It would be surprising if other
stars or other astrophysical systems with magnetic fields were simpler
than the solar atmosphere.
Title: Science with Solar-B solar optical telescope
Authors: Tsuneta, S.; Title, A.
Bibcode: 2004cosp...35.4418T
Altcode: 2004cosp.meet.4418T
SOLAR-B to be launched in the summer of 2006 will carry optical, EUV
and X-ray telescopes. The prime purpose is to track the sub-surface
generation and transport of magnetic fields and its eventual dissipation
in the corona. Solar Optical Telescope (SOT) is a 50cm telescope (0.2
arcsec resolution at 0.5micron, wavelengths: 380nm-670nm, FOV: 328
x 164 arcsec) with spectro-polarimeter (0.16 arcsec pixel) and with
filtergraph for high spatial and temporal observations (0.08 arcsec
pixel). SOT is a combination of the flying Advanced Stokes Polarimeter
and the flying Swedish solar telescope (with lesser spatial resolution)
with 24 hour coverage. Polarimetric and helioseismic approaches allow
us to simultaneously observe the magnetic fields on and below the
photosphere. Configuration of sub-surface and emergent magnetic flux
tubes, emergence, submergence, and cancellation of magnetic fields,
disintegration and transport of sunspot fields, direct detection
of various MHD waves, role of magnetic helicity and flows, nature
of elemental flux tubes are among the massive topics to be pursued
with SOT. SOT also brings fusion of observations and numerical MHD
simulation. Time-dependent boundary-data of magnetic and velocity fields
may be directly fed to the MHD system in the computer to predict its
evolution, that is compared with the X-ray and EUV data.
Title: Solar Magnetic Loops Observed with TRACE and EIT
Authors: Aschwanden, M. J.; Title, A. M.
Bibcode: 2004IAUS..219..503A
Altcode: 2003IAUS..219E.219A
We review major discoveries and new physical results that have
been obtained from the TRACE mission over the last 4 years such as:
(1) the temperature and density inhomogeneity of the coronal plasma
(2) hydrostatic and non-hydrostatic loops (3) plasma flows in loops
(4) transverse oscillations in the MHD kink-mode (5) the spatial
heating function of loops (6) intermittent heating and cooling time
scales (7) iron abundance enhancements (8) magnetic nullpoints and
separator regions (9) highly fragmented postflare loop arcades and
(10) nanoflare loop phenomena. We transform the physical properties
as measured by TRACE for the Sun to stellar coronae and show how
information on heating and cooling processes can be obtained from
stellar differential emission measure (DEM) distributions.
Title: Toward understanding the sun's magnetic fields
Authors: Title, A.; Schrijver, K.
Bibcode: 2004cosp...35.1292T
Altcode: 2004cosp.meet.1292T
The magnetic field of the Sun is responsible for heating of the outer
solar atmosphere. Thus it controls the EUV, x-Ray, and gamma-ray
emission of the Sun. Recent observations with the TRACE satellite
show that the outer atmosphere is highly structured, dynamic, and
multi-thermal. The combination of convection cells and large scale
flows moves, mixes, and inserts magnetic feature. In this talk origin
and scales of resulting magnetic configurations are examined. It now
appears that small-scale localized fields interact with large-scale
flux systems to feed energy from scales of 1000 km to 100,000 km
and more. How scales of convection and magnetic fields interact my
provide clues on the fundamental processes responsible for heating in
astrophysical systems. The talk will be illustrated by visualizations
of numerical simulations and observations from observatories on the
ground and in space.
Title: The Focal Plane Package for Solar B
Authors: Title, A.; Tsuneta, S.
Bibcode: 2004cosp...35.1299T
Altcode: 2004cosp.meet.1299T
The Focal Plane Package (FPP) of the JAXA Solar B Solar Optical
Telescope (SOT) combines an advanced version of Stokes Polarimeter, a
tunable birefringent filter, and a set of narrow spectral filters. The
Stokes Polarimeter and the filter systems can operate simultaneously
allowing the construction of precise vector magnetograms and images
in a range of spectral lines. Both the Stokes Polarimeter and the
filter systems have controllable fields of view and cadence. A local
correlation tracker in the FFP operates a high speed tip-tilt mirror
to stabilize the image in all focal planes. The time sequences of
precise vector magnetic maps uncompromised by seeing will enable new
understanding of how flux emerges through and disappears from the solar
surface. The tunable filter can measure the flows in the atmosphere
from the lower photosphere through the Chromosphere enabling new
insights in the magneto-hydrodynamics of magnetic evolution.
Title: The Magnetic Connection between the Solar Photosphere and
the Corona
Authors: Schrijver, Carolus J.; Title, Alan M.
Bibcode: 2003ApJ...597L.165S
Altcode:
The solar magnetic field that extends through the chromosphere into
the corona is envisioned to fan out from strong flux concentrations
located within the supergranular downflow lanes. That so-called network
field appears to be surrounded by a mixed-polarity magnetic field with
a scale comparable to that of the granulation. We argue that for an
internetwork field with a magnitude of a few tens of Mx cm-2,
as suggested by both observations and models, the commonly held notion
of a wineglass-shaped magnetic canopy of network flux that fully
encloses weakly magnetic regions below it is fundamentally wrong. We
estimate that in the presence of such a relatively strong internetwork
field, as much as half of the coronal field over very quiet Sun may
be rooted in that mixed-polarity internetwork field throughout the
supergranules rather than in the network flux concentrations, as
assumed until now. A corresponding amount of flux forms collars of
closed loops around the network concentrations, connecting network
flux back down onto the internetwork field over distances of several
thousand kilometers. Within such a geometry, the rapid evolution of
the internetwork field may substantially affect coronal heating and the
acceleration of the solar wind. We discuss the potential consequences
of these interacting network and internetwork fields for atmospheric
heating, for wave propagation and the formation of acoustic shadows,
and for the appearance of the near-surface solar outer atmosphere.
Title: Observations of Rotating Sunspots from TRACE
Authors: Brown, D. S.; Nightingale, R. W.; Alexander, D.; Schrijver,
C. J.; Metcalf, T. R.; Shine, R. A.; Title, A. M.; Wolfson, C. J.
Bibcode: 2003SoPh..216...79B
Altcode:
Recent observations from TRACE in the photospheric white-light channel
have shown sunspots that rotate up to 200° about their umbral centre
over a period of 3-5 days. The corresponding loops in the coronal fan
are often seen to twist and can erupt as flares. In an ongoing study,
seven cases of rotating sunspots have been identified, two of which
can be associated with sigmoid structures appearing in Yohkoh/SXT and
six with events seen by GOES. This paper analyzes the rotation rates
of the sunspots using TRACE white-light data. Observations from AR
9114 are presented in detail in the main text and a summary of the
results for the remaining six sunspots is presented in Appendixes
A-F. Discussion of the key results, particularly common features,
are presented, as well as possible mechanisms for sunspot rotation.
Title: SUNRISE: Balloon-borne High-Resolution Observation of the Sun
Authors: Solanki, S. K.; Curdt, W.; Gandorfer, A.; Schüssler,
M.; Lites, B. W.; Martinez Pillet, V.; Schmidt, W.; Title, A. M.;
Sunrise Team
Bibcode: 2003ANS...324..113S
Altcode: 2003ANS...324..P20S
No abstract at ADS
Title: Asterospheric Magnetic Fields and Winds of Cool Stars
Authors: Schrijver, Carolus J.; De Rosa, Marc L.; Title, Alan M.
Bibcode: 2003ApJ...590..493S
Altcode:
This study addresses the winds and magnetic fields in the inner
asterospheres of Sun-like magnetically active stars by combining
empirical relationships between rotation rate and mass loss,
angular-momentum loss, and radiative losses with models of the magnetic
fields at the surfaces of cool stars and in their inner asterospheres
based on the solar example. Our models, for mean magnetic flux densities
up to 10 times solar, suggest that the asterospheric fields of such
stars are dominated by the large-scale dipole component of the surface
field, as is the case for the Sun. Hence, most of the time a single
current sheet is expected to separate domains of opposite magnetic
polarity; the current sheets of more active stars generally have smaller
latitudinal ripples. Magnetic braking requires that the total unsigned
asterospheric magnetic flux increase linearly with the stellar angular
velocity, which is a very much weaker increase than seen for the flux at
the stellar surface. We show that this can be achieved by an increase
in the radial distance at which the coronal field is forced open as
surface activity increases. Combined with measured mass-loss rates
and the assumption that the wind velocity is largely independent of
activity, this requires the wind's Alfvén radius to be nearly constant,
decreasing with surface activity with a power of only -0.16+/-0.13. We
point out that the surface flux density of energy needed to drive a
cool-star wind scales linearly with the unsigned surface magnetic flux
density, as does that needed to heat the corona.
Title: Observations of magnetoconvection in Sunspots with 100 km
resolution
Authors: Berger, T. E.; Löfdahl, M. G.; Scharmer, G.; Title, A. M.
Bibcode: 2003SPD....34.1108B
Altcode: 2003BAAS...35..828B
We present new observations from the Swedish 1-meter Solar Telescope
(SST) on La Palma with ∼0.1 arcsecond ( ∼100 km) resolution:
the highest resolution yet achieved in solar observations. We focus
on sunspot and active region magnetoconvective phenomena using G-band
4305 Å, 4877 Å continuum, 7507 Å TiO bandhead, and Ca II 3968 Å
H-line filtergram movies. The G-band data are post-processed using
Joint Phase Diverse Speckle wavefront restoration to create a full
diffraction limited time series. Sunspot light-bridges are shown to
have dark lanes less than 300 km in width that are coherent along
the entire length of the bridge. Similarly, we find elongated dark
``canals'' in plage regions, particularly near pores, that appear to be
highly modified intergranular downflow lanes. The canals are less than
200 km in width and are much more coherent than intergranular lanes
in non-magnetic regions, often retaining their basic structure for
more than one granular turn-over time. Both the light-bridge central
lane and the canals appear to be the result of highly constrained
flow structure in strong magnetic field regions -- an aspect of solar
magnetoconvection that has not previously been observed. This reseach
was supported by funding from the Royal Swedish Academy of Sciences,
a SOHO Guest Investigator subcontract to California State University
Northridge, and the NASA TRACE contract NAS5-38099 at Lockheed Martin.
Title: SUNRISE: a balloon-borne telescope for high resolution solar
observations in the visible and UV
Authors: Solanki, Sami K.; Gandorfer, Achim M.; Schuessler, Manfred;
Curdt, W.; Lites, Bruce W.; Martinez-Pillet, Valentin; Schmidt,
Wolfgang; Title, Alan M.
Bibcode: 2003SPIE.4853..129S
Altcode:
Sunrise is a light-weight solar telescope with a 1 m aperture for
spectro-polarimetric observations of the solar atmosphere. The telescope
is planned to be operated during a series of long-duration balloon
flights in order to obtain time series of spectra and images at the
diffraction-limit and to study the UV spectral region down to ~200 nm,
which is not accessible from the ground. The central aim of Sunrise
is to understand the structure and dynamics of the magnetic field in
the solar atmosphere. Through its interaction with the convective flow
field, the magnetic field in the solar photosphere develops intense
field concentrations on scales below 100 km, which are crucial for the
dynamics and energetics of the whole solar atmosphere. In addition,
Sunrise aims to provide information on the structure and dynamics
of the solar chromosphere and on the physics of solar irradiance
changes. Sunrise is a joint project of the Max-Planck-Institut fuer
Aeronomie (MPAe), Katlenburg-Lindau, with the Kiepenheuer-Institut fuer
Sonnenphysik (KIS), Freiburg, the High-Altitude Observatory (HAO),
Boulder, the Lockheed-Martin Solar and Astrophysics Lab. (LMSAL),
Palo Alto, and the Instituto de Astrofi sica de Canarias, La Laguna,
Tenerife. In addition, there are close contacts with associated
scientists from a variety of institutes.
Title: TRACE Observation of an Arcade Flare Showing Evidence
Supporting Quadruple Magnetic Source Model for Arcade Flares
Authors: Uchida, Yutaka; Title, Alan; Kubo, Masahito; Tanaka, Tomohiro;
Morita, Satoshi; Hirose, Shigenobu
Bibcode: 2003PASJ...55..305U
Altcode:
The result of analyses of an arcade flare on 1999 July 19, observed by
the Satellite TRACE, is reported, and the significance of the following
findings is stressed. It is clearly seen that four magnetic regions of
alternating polarities [named A(+), B(-), C(+), and D(-) from the East
in the flaring region] are involved in this arcade flare event in an
essential way. The high structure covering the triangular region between
A and the northern part of D disappears when the dark filament lying
between B and C erupts. The X-ray arcade is formed only between B and
C. The overlying structure connecting regions A and the northern part of
D disappears and the entire region is involved in the flare. Low-lying
loops connect the inner sources to the outer sources. The field lines
from regions B to A and C to D are not much affected by the eruption
of the dark filament, itself, but the loops near the upper surfaces
of the closed loop regions are clearly seen to move toward each other
(from both sides to the central line) as the arcade flare progresses
between the inner pair, B and C; some of them appear to be converted
into a flare arcade. The observed behavior can best be understood in
terms of the quadruple magnetic source model advocated by one of the
authors (YU). The long-conceived ``reclosing of once opened bipolar
magnetic arcade'' models by the rising dark filament (called CSHKP
model) find it difficult to explain this.
Title: The Properties of Small Magnetic Regions on the Solar Surface
and the Implications for the Solar Dynamo(s)
Authors: Hagenaar, Hermance J.; Schrijver, Carolus J.; Title, Alan M.
Bibcode: 2003ApJ...584.1107H
Altcode:
We find that bipolar active regions that emerge onto the Sun's surface
are part of a smoothly decreasing frequency distribution that spans
almost 4 orders of magnitude in flux and 8 orders of magnitude in
frequency. Distributions of emergence latitude and dipole orientation
narrow from nearly uniform for the smallest observed ephemeral regions
(~5×1018 Mx) up to narrowly distributed about the mean for
the largest active regions (close to 1022 Mx), while the
emergence frequency increases smoothly and rapidly with decreasing
flux. At the low end of the flux spectrum, the cycle variation in
emergence frequency is at most a factor of 1.5, in antiphase with
the cycle variation of close to an order of magnitude for the large
active regions. We discuss a scenario in which the ephemeral regions
with fluxes below ~30×1018 Mx have their origin in a
turbulent dynamo, largely independent of the global sunspot cycle. Our
empirical findings are based on a combination of previously published
work on active regions and large ephemeral regions, complemented
here with an analysis of the photospheric magnetic field outside
active regions, as observed in SOHO/MDI full-disk magnetograms taken
from the most recent sunspot minimum in 1996 to about 1 yr after
sunspot maximum in 2001. We find that the spectrum of the emerging
bipoles with fluxes (6-30)×1018 Mx can be approximated
throughout this period by a fixed exponential distribution with
an e-folding scale of (5.3+/-0.1)×1018 Mx. We confirm
that the ephemeral regions are an important source of flux for the
quiet magnetic network, in particular for the smallest scales; the
larger scale patterns are dominated by flux dispersing from decaying
active regions. As the variation of these two sources is nearly in
antiphase, the flux contained in the quiet-Sun network shows little
overall variation: the flux spectrum and the total absolute flux for
network concentrations with fluxes <~20×1018 Mx are
essentially independent of cycle phase. For network concentrations with
fluxes >~30×1018 Mx, mostly found in regions populated
substantially by decayed active regions, the network flux distribution
approaches an exponential for which the e-folding scale increases with
sunspot activity from ~20×1018 Mx to ~33×1018
Mx, as the total flux in this component varies in phase with the sunspot
cycle. A comparison of the flux-emergence rate with the network flux
implies an overall mean replacement time for flux in quiet Sun of
8-19 hr.
Title: Instrumentation and Science in Space - The Future
Authors: Title, A. M.
Bibcode: 2003ASPC..307..575T
Altcode:
No abstract at ADS
Title: A New View of the Magnetic Sun
Authors: Title, A.
Bibcode: 2003IAUS..210..195T
Altcode:
No abstract at ADS
Title: Active regions as sources of the heliospheric field
Authors: Schrijver, C. J.; De Rosa, M. L.; Title, A. M.
Bibcode: 2002AGUFMSH52A0436S
Altcode:
The magnetic field in the heliosphere originates from a variety
of sources on the surface of the Sun, including mature, decaying,
and decayed active regions, as well as sunspots. The emergence of new
active regions together with the dispersal of flux from older active
regions causes the coronal magnetic field topology to continually
evolve, allowing previously closed-field regions to open into the
heliosphere and previously open-field regions to close. Such evolution
of the coronal field, together with the rotation of the Sun, drive
space weather through the continually changing conditions of the solar
wind and the magnetic field embedded within it. We combine observations
and numerical simulations by assimilating SOHO/MDI magnetograms into a
surface flux transport model, in order to investigate the origins of
the heliospheric field on the solar surface through the rising phase
of the current activity cycle. We find that around cycle maximum,
the interplanetary magnetic field (IMF) is typically rooted in a
dozen disjoint regions on the solar surface. Whereas active regions
are sometimes ignored as a source for the IMF, the fraction of the
IMF that connects directly to magnetic plage is found to reach up to
30-50%\ at cycle maximum, with even direct connections between sunspots
and the heliosphere. We further compare this data assimilation model
with a pure simulation model, in which the properties of the emergent
active regions were chosen at random from parent distribution functions
measured for the sun. The two models show remarkable agreement in the
temporal behavior of the sector structure of the IMF, in the magnitude
and time-behavior of the heliospheric field, and even in such global
properties as the tilt angle of the Sun's large scale dipole. We thus
conclude that no additional flux-emergence patterns or field-dispersal
properties are required of the solar dynamo beyond those that are
included in the model in order to understand the large-scale solar
and heliospheric fields.
Title: Visualizing and Interpreting Very High Resolution Solar Movies
Authors: Shine, R. A.; Hurlburt, N.; Title, A. M.; Nightingale, R. W.
Bibcode: 2002AGUFMSH52A0498S
Altcode:
Benefiting from advances in detector technology, image compression,
and data storage capacities, current and upcoming solar instruments,
especially the Solar Dynamics Observatory (SDO) due to be launched in
2007, will produce immense amounts of data in the form of movies with
individual images in the 2048x2048 (4 Mpixel) to 4096x4096 (16 Mpixel)
range. This is beyond the capability of most contemporary computer
or video displays but several are now becoming available. In order to
develop concepts and software for working with existing and future data
sets, we have been working with a 9 Mpixel IBM T221 LCD display driven
by an SGI Octane 2 workstation. This is a desktop display with a 22
inch diagonal screen. We will demonstrate our prototype system using
several combinations of movies from the Swedish Vacuum Solar Tower
(SVST) at La Palma, and the TRACE and SOHO satellites and discuss some
approaches for the more challenging SDO data products.
Title: High Speed Reconnection in the Low Corona
Authors: Title, A. M.; Shine, R. A.; Schrijver, C. J.
Bibcode: 2002AGUFMSH52A0470T
Altcode:
High cadence observations taken with the Transition Region and Corona
Explorer (TRACE) instrument in the 1600Å\ band (with ≈~2 second
cadence) and in the Fe~IX/X 171Å\ band (≈~8 seconds cadence)
reveal fast reconnection events of several types. The most common
is a newly emerging magnetic loop that reconnects with an overlying
fan of loops. As the loops intersect, material is injected into the
overlying loops. A newly formed small bright condensation travels in
a helical path with a pitch angle of about 45 degrees and a speed of
700 to 1000 km/s. Movies of example events in both spectral bands will
be shown. This work was supported by NASA contract NAS5-38099.
Title: The properties of small magnetic regions on the solar surface
and the implications for the solar dynamo(s)
Authors: Hagenaar, M.; Schrijver, C. J.; Title, A. M.
Bibcode: 2002AGUFMSH52A0447H
Altcode:
We study a combination of previously published work on active regions
and large ephemeral regions, complemented with an analysis of the
photospheric magnetic field outside active regions, as observed in
SOHO/MDI full-disk magnetograms taken from the most recent sunspot
minimum in 1996 to about a year after sunspot maximum in 2001. We
find that bipolar active regions that emerge onto the Sun's surface
are part of a smoothly decreasing frequency distribution that spans
almost 4 orders of magnitude in flux and 8 orders of magnitude in
frequency. Distributions of emergence latitude and dipole orientation
narrow from nearly uniform for the smallest observed ephemeral regions
(~ 5x 1018 Mx) up to narrowly distributed about the mean
for the largest active regions (close to 1022 Mx), while
the emergence frequency increases smoothly and rapidly with decreasing
flux. At the low end of the flux spectrum, the cycle variation in
emergence frequency is at most a factor of 1.5, in antiphase with the
cycle variation of close to an order of magnitude for the large active
regions. We discuss a scenario in which the ephemeral regions with
fluxes below ~ 30x 1018 Mx have their origin in a turbulent
dynamo, largely independent of the global sunspot cycle. We confirm
that the ephemeral regions are an important source of flux for the
quiet magnetic network, in particular for the smallest scales; the
larger scale patterns are dominated by flux dispersing from decaying
active regions. A comparison of the flux-emergence rate with the
network flux implies an overall mean replacement time for flux in
quiet Sun of 8-19 hrs.
Title: Sunrise: a 1-m balloon borne solar telescope
Authors: Solanki, S. K.; Schüssler, M.; Curdt, W.; Lites, B. W.;
Martinez Pillet, V.; Schmidt, W.; Title, A. M.; Sunrise Team
Bibcode: 2002ESASP.505...27S
Altcode: 2002solm.conf...27S; 2002IAUCo.188...27S
Sunrise is a light-weight solar telescope with a 1 m aperture
for spectro-polarimetric observations of the solar atmosphere. The
telescope is planned to be operated during a series of long-duration
balloon flights in order to obtain time series of spectra and images
at the diffraction-limit and to study the UV spectral region down to
≅200 nm, which is not accessible from the ground. The central aim of
Sunrise is to understand the structure and dynamics of the magnetic
field in the solar atmosphere. Interacting with the convective flow
field, the magnetic field in the solar photosphere develops intense
field concentrations on scales below 100 km, which are crucial for the
dynamics and energetics of the whole solar atmosphere. In addition,
Sunrise aims to provide information on the structure and dynamics of
the solar chromosphere and on the physics of solar irradiance changes.
Title: The long-term variations of the solar and heliospheric fields
Authors: Schrijver, Carolus J.; De Rosa, Marc L.; Title, Alan M.
Bibcode: 2002ESASP.505..253S
Altcode: 2002IAUCo.188..253S; 2002solm.conf..253S
The heliospheric field is determined by the largest-scale patterns of
magnetism at the solar surface, dominated by the lower-latitude active
regions during cycle maximum, and by the circumpolar fields during
cycle minimum. To study these patterns, we simulate the evolution of
the magnetic field at the solar surface and in the heliosphere during
the last 340 years. We conclude that, contrary to current thinking,
the observed magnetic flux in the polar regions of the Sun cannot be
understood as merely a long-term accumulation of active-region decay
products from a dynamo that modulates only the rate at which flux
emerges from cycle to cycle. We suggest that simulation and observation
may be reconciled if the high-latitude solar field decays on a time
scale comparable to that of the sunspot cycle.
Title: What Is Missing from Our Understanding of Long-Term Solar
and Heliospheric Activity?
Authors: Schrijver, Carolus J.; De Rosa, Marc L.; Title, Alan M.
Bibcode: 2002ApJ...577.1006S
Altcode:
The heliospheric magnetic field is associated with changes in space
weather, cosmic-ray flux, and likely climate. This field is determined
by the largest scale patterns of magnetism at the solar surface,
dominated by the lower latitude active regions during cycle maximum and
by the circumpolar fields during cycle minimum. Whereas the magnetic
field in the activity belt is readily studied, the high-latitude
field is much less accessible, and its study requires a combination of
modeling and observation. Current models hold that the high-latitude
magnetic field on the Sun is determined solely by the accumulation of
field transported poleward from lower latitude active regions. We test
this hypothesis by simulating the evolution of the magnetic field at
the solar surface and in the heliosphere during the last 340 yr using a
state-of-the-art model that incorporates all processes that are known to
contribute significantly to the evolution of the large-scale patterns
in the solar field. We find that if only the emergence frequency of
magnetic bipoles is varied in accordance with observed sunspot records,
the polar-cap field reservoir does not match measurements during past
years. Based on comparisons of our simulations with observed polar
fluxes over the last few decades and with the proxy for the heliospheric
flux formed by 340 yr of 10Be ice-core data, we suggest that
the high-latitude field may be subject to decay on a timescale of 5-10
yr. We discuss the consequences of this finding for our understanding
of the Sun-Earth connection and explore inferences for the coupling
of the Sun's internal magnetic field to the heliospheric field.
Title: Observations of rotating sunspots and their effect in the
corona
Authors: Brown, D. S.; Nightingale, R. W.; Alexander, D.; Schrijver,
C. J.; Metcalf, T. R.; Shine, R. A.; Title, A. M.; Wolfson, C. J.
Bibcode: 2002ESASP.505..261B
Altcode: 2002IAUCo.188..261B; 2002solm.conf..261B
Recent observations from TRACE have seen sunspots, in the photospheric
white light filter, rotate up to 180 degrees about their umbral
centre. The corresponding loops in the coronal fan are seen to twist
and can erupt. In an ongoing study, five cases of rotating sunspots
have been identified, three of which can be identified with sigmoid
structures appearing in Yohkoh/SXT. This paper will present images from
one of these events, showing the coupling between the photosphere and
the corona, and observational analysis deducing the rotation speeds
and how they change through time and with radius of the sunspot. In
particular, the paper will focus on the best example of a rotating
sunspot observed so far, that of AR 9114 which occurred over 8-10 August
2000 and was observed by TRACE, SoHO/MDI and Yohkoh/SXT. The sunspot
rotated 150 degrees within this time and is associated with a sigmoid.
Title: A Flux-Tube Tectonics Model for Solar Coronal Heating Driven
by the Magnetic Carpet
Authors: Priest, Eric R.; Heyvaerts, Jean F.; Title, Alan M.
Bibcode: 2002ApJ...576..533P
Altcode:
We explore some of the consequences of the magnetic carpet for coronal
heating. Observations show that most of the magnetic flux in the
quiet Sun emerges as ephemeral regions and then quickly migrates
to supergranule boundaries. The original ephemeral concentrations
fragment, merge, and cancel over a time period of 10-40 hr. Since
the network photospheric flux is likely to be concentrated in units
of 1017 Mx or smaller, there will be myriads of coronal
separatrix surfaces caused by the highly fragmented photospheric
magnetic configuration in the quiet network. We suggest that the
formation and dissipation of current sheets along these separatrices
are an important contribution to coronal heating. The dissipation of
energy along sharp boundaries we call, by analogy with geophysical
plate tectonics, the tectonics model of coronal heating. Similar to
the case on Earth, the relative motions of the photospheric sources
will drive the formation and dissipation of current sheets along a
hierarchy of such separatrix surfaces at internal dislocations in the
corona. In our preliminary assessment of such dissipation we find
that the heating is fairly uniform along the separatrices, so that
each elementary coronal flux tube is heated uniformly. However, 95%
of the photospheric flux closes low down in the magnetic carpet and
the remaining 5% forms large-scale connections, so the magnetic carpet
will be heated more effectively than the large-scale corona. This
suggests that unresolved observations of coronal loops should exhibit
enhanced heating near their feet in the carpet, while the upper parts of
large-scale loops should be heated rather uniformly but less strongly.
Title: Photospheric Magnetic Activities Responsible for Soft
X-Ray Pointlike Microflares. I. Identifications of Associated
Photospheric/Chromospheric Activities
Authors: Shimizu, T.; Shine, R. A.; Title, A. M.; Tarbell, T. D.;
Frank, Z.
Bibcode: 2002ApJ...574.1074S
Altcode:
By combining Yohkoh soft X-ray images with high-resolution magnetograms
simultaneously obtained at La Palma, we studied photospheric magnetic
signatures responsible for soft X-ray microflares (active-region
transient brightenings). In order to have a reliable correspondence
between the photosphere and the corona, we studied 16 pointlike
transient brightenings with X-ray source size less than 10" occurring
during periods when the seeing was excellent at La Palma, although a
lot of transient brightenings were in forms of multiple- or single-loop
structures. In half of the studied events, small-scale emergences
of magnetic flux loops are found in the vicinity of the transient
brightenings. Six events of that half show that a small-scale flux
emergence accompanies the X-ray brightening 5-30 minutes prior to
its onset. In the other half of the studied events, no apparent
evolutionary change of magnetic flux elements is found associated
with the transient brightenings. Many of these events are found in
rather strong magnetic fields, such as sunspots and pores, implying
that small-scale changes of magnetic flux are obscured or suppressed
by strong magnetic fields. The horizontal plasma flows derived from
local cross-correlation tracking of granules in continuum images are
suppressed at the feet of some X-ray transient brightenings.
Title: The topology of a mixed-polarity potential field, and
inferences for the heating of the quiet solar corona
Authors: Schrijver, Carolus J.; Title, Alan M.
Bibcode: 2002SoPh..207..223S
Altcode:
We study the statistical properties of the connectivity of the corona
over the quiet Sun by analyzing the potential magnetic field above
the central area of source planes sprinkled randomly with some 300
magnetic monopoles each. We find that the field is generally more
complex than one might infer from a study of the field within the
source plane alone, or from a study of the 3D field around a small
number of sources. Whereas a given source most commonly connects
to only its nearest neighbors, it may connect to up to several dozen
sources; only a weak trend relates the source strength and the number of
connections. The connections between pairs of sources define volumes,
or domains, of connectivity. Domains that have a finite cross section
with the source plane are enclosed by surfaces that contain a pair
of null points. In contrast, most of the bounding surfaces of domains
that lie above the source plane appear not to contain null points. We
argue that the above findings imply (i) that we should expect at
best a weak correlation between coronal brightness and the flux in an
underlying flux concentration, and (ii) that the low-lying chromospheric
field lines (such as are observable in Hα) provide information on
source connections that are largely complementary to those traced by
the higher-reaching coronal field lines (observable in the extreme
ultraviolet). We compare sample TRACE and SOHO/MDI observations of the
quiet corona and photosphere with our finding that the number density
of null points within the source plane closely matches that of the
sources; because we find essentially no foci of coronal brightening
away from significant photospheric magnetic flux concentrations, we
conclude that coronal heating at such null points does not contribute
significantly to the overall heating. We argue that the divergence of
field lines towards multiple sources restricts the propagation of braids
and twists, so that any coronal heating that is associated with the
dissipation of braids induced by footpoint shuffling in mixed-polarity
network is likely (a) to occur predominantly low in the corona, and
(b) to be relatively more efficient in quiet Sun than in active regions
for a given field strength and loop length.
Title: Sunspots
Authors: Title, A. M.
Bibcode: 2002AAS...200.3407T
Altcode: 2002BAAS...34..691T
The last decade has reveal much about the structure of sunspots. New
imaging techniques have captured with very high-resolution the structure
in the umbra and penumbra, Stokes polarimetry has reveal new details
of the magnetic structure, and the long duration observations from
space are revealing how sunspots are born and how they disappear. We
can expect a significant advance in our understanding of the sunspot
phenomena and flux emergence from the images of the temperature and flow
structure below the solar surface obtained via acoustic imaging. In
parallel with the advances in observational data numerical models are
now of sufficient resolution to predict some of the structures and
flow systems seen below the surface. Above the surface line profile
inversion techniques are revealing the structure of the spot throughout
the photosphere. This work is supported by NASA.
Title: A Search For A Relationship Between Flare Duration and Its
Associated Activated Coronal Volume
Authors: Slater, G. L.; Title, A. M.
Bibcode: 2002AAS...200.3609S
Altcode: 2002BAAS...34..694S
Solar flares have long been divided into two general categories: long
duration flares, and short duration (or impulsive) flares. A parallel
division of flares into eruptive flares and confined flares has also
long been in use, and it has often been assumed that long duration
flares are more likely to be eruptive. At the same time, there is a
general belief that eruptive events are more likely associated with
coronal mass ejections (CMEs). CMEs, in turn, are believed to associated
with more global destabilizations of the corona than flares, which
are local in origin. This study will search for a correlation between
flare duration and the associated volume of the coronal involved in
the flare in an attempt to understand the flare/CME relationship. SXT
and EIt databases will be used for this purpose.
Title: Erratum: ``On the Formation of Polar Spots in Sun-like Stars''
(ApJ, 551, 1099 [2001])
Authors: Schrijver, Carolus J.; Title, Alan M.
Bibcode: 2002ApJ...568.1100S
Altcode:
Equation (3) and the subsequent expression for the
tapering function were misprinted and should appear as
follows: ``We find an acceptable fit to solar observations
forvM=13sin(2θ)f(θ')f(π-θ')ms-
1,(3)with a tapering function of colatitude θ' (in
radians) of f(θ')=1-exp[-(1.45θ')3]
that is effective only above ~40°.''
Title: Transverse oscillations in coronal loops observed with
TRACE I. An Overview of Events, Movies, and a Discussion of Common
Properties and Required Conditions
Authors: Schrijver, Carolus J.; Aschwanden, Markus J.; Title, Alan M.
Bibcode: 2002SoPh..206...69S
Altcode:
We study transverse loop oscillations triggered by 17flares and filament
destabilizations; only 2 such cases have been reported in the literature
until now. Oscillation periods are estimated to range over a factor
of ∼15, with most values between 2 and 7 min. The oscillations are
excited by filament destabilizations or flares (in 6% of the 255 flares
inspected, ranging from about C3 to X2). There is no clear dependence
of oscillation amplitude on flare magnitude. Oscillations occur in
loops that close within an active region, or in loops that connect
an active region to a neighboring region or to a patch of strong
flux in the quiet Sun. Some magnetic configurations are particularly
prone to exhibit oscillations: two active regions showed two, and one
region even three, distinct intervals with loop oscillations. The
loop oscillations are not a resonance that builds up: oscillations
in loops that are excited along their entire length are likely to be
near the fundamental resonance mode because of that excitation profile,
but asymmetrically excited oscillations clearly show propagating waves
that are damped too quickly to build up a resonance, and some cases show
multiple frequencies. We discuss evidence that all oscillating loops lie
near magnetic separatrices that outline the large-scale topology of the
field. All magnetic configurations are more complicated than a simple
bipolar region, involving mixed-polarities in the interior or vicinity
of the region; this may reflect that the exciting eruptions occur only
in such environments, but this polarity mixing likely also introduces
the large-scale separatrices that are involved. Often the oscillations
occur in conjunction with gradual adjustments in loop positions in
response to the triggering event. We discuss the observations in
the context of two models: (a) transverse waves in coronal loops
that act as wave guides and (b) strong sensitivity to changes in
the field sources for field lines near separatrices. Properties
that favor model b are (1) the involvement of loops at or near
separatrices that outline the large-scale topology of the field,
(2) the combined occurrence of oscillations and loop translations,
(3) the small period spread and similar decay time scale in a set of
oscillating loops in one well-observed event, and (4) the existence
of loops oscillating in antiphase with footpoints close together in
two cases. All other properties are compatible with either model,
except the fact that almost all of the oscillations start away from
the triggering event, suggestive of an outward-pushing exciting wave
more in line with model a. The spread in periods from event to event
suggests that the oscillations may reflect the properties of some
driver mechanism that is related to the flare or mass ejection.
Title: Transverse Oscillations in Coronal Loops Observed with TRACE
II. Measurements of Geometric and Physical Parameters
Authors: Aschwanden, Markus J.; De Pontieu, Bart; Schrijver, Carolus
J.; Title, Alan M.
Bibcode: 2002SoPh..206...99A
Altcode:
We measure geometric and physical parameters oftransverse oscillations
in 26 coronal loops, out of the 17 events described in Paper I by
Schrijver, Aschwanden, and Title (2002). These events, lasting
from 7 to 90 min, have been recorded with the Transition Region
and Coronal Explorer (TRACE) in the 171 and 195 Å wavelength
bands with a characteristic angular resolution of 1", with time
cadences of 15-75 seconds. We estimate the unprojected loop (half)
length L and orientation of the loop plane, based on a best-fit of a
circular geometry. Then we measure the amplitude A(t) of transverse
oscillations at the loop position with the largest amplitude. We
decompose the time series of the transverse loop motion into an
oscillating component Aosc(t) and a slowly-varying trend
Atrend(t). We find oscillation periods in the range of
P=2-33 min, transverse amplitudes of A=100-8800 km, loop half lengths
of L=37 000-291 000 km, and decay times of td=3.2-21 min. We
estimate a lower limit of the loop densities to be in the range of
nloop=0.13-1.7×109 cm−3. The
oscillations show (1) strong deviations from periodic pulses, (2)
spatially asymmetric oscillation amplitudes along the loops, and
(3) nonlinear transverse motions of the centroid of the oscillation
amplitude. From these properties we conclude that most of the
oscillating loops do not fit the simple model of kink eigen-mode
oscillations, but rather manifest flare-induced impulsively generated
MHD waves, which propagate forth and back in the loops and decay
quickly by wave leakage or damping. In contrast to earlier work we
find that the observed damping times are compatible with estimates of
wave leakage through the footpoints, for chromospheric density scale
heights of ≈400-2400 km. We conclude that transverse oscillations
are most likely excited in loops that (1) are located near magnetic
nullpoints or separator lines, and (2) are hit by a sufficiently
fast exciter. These two conditions may explain the relative rarity of
detected loop oscillations. We show that coronal seismology based on
measurements of oscillating loop properties is challenging due to the
uncertainties in estimating various loop parameters. We find that a
more accurate determination of loop densities and magnetic fields,
as well as advanced numerical modeling of oscillating loops, are
necessary conditions for true coronal seismology.
Title: Concurrent Rotating Sunspots, Twisted Coronal Fans, Simgoid
Structures and Coronal Mass Ejections
Authors: Nightingale, R. W.; Brown, D. S.; Metcalf, T. R.; Schrijver,
C. J.; Shine, R. A.; Title, A. M.; Wolfson, C. J.
Bibcode: 2002mwoc.conf..149N
Altcode:
In an on-going study, several sunspots, in apparent rotation, have
been identified in TRACE photospheric white light (WL) images with
accompanying twisting of coronal fans in the corresponding EUV (171,
195 AA) images. These observations can also be temporally and spatially
associated with S or inverse-S shaped regions (sigmoid structures)
appearing in Yohkoh SXT images and with concurrent coronal mass
ejections (CMEs) and/or flares. We have determined the rotational
speed of the apparently rotating sunspot in AR 9114 over 8-10 August
2000, established the inverse S shape observed in the SXT data, and
viewed a rapid, bright flash of possible reconnection in a TRACE
EUV movie. A CME was observed during the 15-18 August 1999 event,
which also included an inverse S shaped region in the SXT data, and
a rotating sunspot and twisting coronal fans in the TRACE data. The
large Bastille Day CME event of 14 July 2000 was accompanied by one
or more apparently rotating sunspots as observed in TRACE WL and by
an inverse S shaped region as seen in a difference SXT image. Movies
and plots of some of these data will be shown along with flow maps and
a list of the pertinent parameters for several rotating sunspots. We
will report on our attempt to determine the vertical electric current
flowing through the 8 August 2000 sunspot utilizing the Mees vector
magnetograph data in order to better understand the apparent rotation
"driver". These observations display the coupling of the solar magnetic
field from the photosphere into the corona.
Title: Trace Observations of Filaments
Authors: Title, A.
Bibcode: 2002EGSGA..27.5090T
Altcode:
The Transition Region and Corona Explorer (TRACE) observes filaments
on the disk via absorption in the EUV bands. Because TRACE observes
the Sun continuously for nine months of the year it has been possible
to obtain a large sampling of filament behaviors. Various types
of filament instabilities have been observed. These include flare
associations, flare triggers, eruptions associated with CME events,
and eruptions not associated with CME's. Filaments are also observed
to have associated features that are bright in the EUV channel. The
behavior of the bright structures suggest that there are extended
vertical planes associated with the filament. Movies will display all
of the above mentioned characteristics.
Title: Transverse oscillations in coronal loops observed with TRACE
Authors: Schrijver, C. J.; Aschwanden, M. J.; De Pontieu, B.; Title,
A. M.
Bibcode: 2001AGUFMSH11A0703S
Altcode:
TRACE discovered transverse oscillations in coronal loops associated
with a flare three years ago, and until recently only two such events
were known. We have now identified a total of 17 events that trigger
some form of loop oscillations. Oscillation periods are estimated to
range over a factor of ~ 15, with most values between 2 and 7 min. The
oscillations are excited by filament destabilizations or flares (in 6%\
of the 255 flares inspected, ranging from about C3 to X2). Oscillations
occur in loops that close within an active region, or in loops that
connect an active region to a neighboring region or to a patch of strong
flux in the quiet Sun. Some magnetic configurations are particularly
prone to exhibit oscillations: two active regions showed two, and
one region even three, distinct intervals with loop oscillations. The
loop oscillations are not a resonance that builds up: oscillations in
loops that are excited along their entire length are likely to be near
the fundamental resonance mode because of that excitation profile, but
asymmetrically excited oscillations clearly show propagating waves that
are damped too quickly to build up a resonance, and some cases show
multiple frequencies. We discuss evidence that all oscillating loops
lie near magnetic separatrices that outline the large-scale topology
of the field. Often the oscillations occur in conjunction with gradual
adjustments in loop positions in response to the triggering event. We
discuss the observations in the context of two models, and evaluate
the contraints on coronal properties that can be deduced from them.
>http://vestige.lmsal.com/TRACE/POD/TRACEoscillations.html</a>
Title: Precision spectro-polarimeter for high-resolution observations
of solar magnetic fields
Authors: Lites, Bruce W.; Elmore, David F.; Streander, Kim V.; Akin,
David L.; Berger, Tom; Duncan, Dexter W.; Edwards, Chris G.; Francis,
Barbara; Hoffmann, Chris; Katz, Noah; Levay, Michael; Mathur, Dnyanesh;
Rosenberg, William A.; Sleight, Ericka; Tarbell, Theodore D.; Title,
Alan M.; Torgerson, Darrel
Bibcode: 2001SPIE.4498...73L
Altcode:
As a Japanese National space mission with international collaboration,
Solar-B (2005 launch) will carry a spectro- polarimeter (SP)
to be operated in visible light to obtain the first high angular
resolution, precision measurements of solar vector magnetic fields
from space. The SP is part of the Focal Plane Package (FPP) fed by a
diffraction-limited 50-cm optical telescope. The SP will be operated
exclusively at the photospheric 630 nm Fe I lines. It features a
rotating, low-order crystalline quartz retarder for polarization
modulation and a reflecting Littrow spectrograph design that is
shortened by using diffraction from the 12micrometers wide slit to
fill the grating. Polarization analysis is accomplished by a modified
Savart plate beam splitter. A custom CCD detector with two active
areas, one for each beam from the beam splitter, allows continuous
high duty-cycle sampling of polarization. The spectrograph slit will
sample a 0.16 x 164 arcsec2 rectangle of the solar image,
which may be scanned across the slit by up to +/- 160 arcsec in order
to build up vector magnetic field maps of the solar photosphere. Along
with simultaneous, co-spatial imaging and polarimetry with the filter
imagers of the FPP, the SP will provide a precise view of active and
quiet solar magnetic fields that control the structure, dynamics,
and energetics of the upper solar atmosphere.
Title: High-resolution solar polarimetry with Sunrise
Authors: Schmidt, W.; Solanki, S. K.; Lites, B. W.; Title, A. M.;
Martínez Pillet, V.
Bibcode: 2001AN....322..363S
Altcode:
Sunrise is a solar telescope with an aperture of 1 m, and is dedicated
for spectropolarimetric measurements in the visible and the near
UV. The total wavelength range is 200 to 1000 nm for narrowband imaging
and diagnostic spectroscopy. Sunrise is planned as a stratospheric
long-duration balloon mission with a first flight in 2006
Title: Sustaining the Sun's Magnetic Network with Emerging Bipoles
Authors: Simon, G. W.; Title, A. M.; Weiss, N. O.
Bibcode: 2001ApJ...561..427S
Altcode:
The Michelson Doppler Imager experiment on SOHO has revealed a
``magnetic carpet'' dominated by the emergence of bipolar magnetic flux
in ephemeral active regions, which subsequently split into small flux
elements that drift into the magnetic network. The effects of granular
and supergranular convection on these flux elements are represented
here by kinematic modeling: Elementary flux tubes are transported
passively by the supergranular flow, while experiencing small random
displacements produced by granulation. They end up in the magnetic
network that surrounds the supergranules, where they eventually meet
oppositely directed fields and are annihilated. The model calculations
show that the total unsigned magnetic flux will decay within a few
days unless it is continually replenished. A statistically steady
state with a total unsigned flux of 2-3×1023 Mx over the
whole solar surface can be maintained if bipolar flux emerges at a rate
of 7×1022 Mx day-1, as indicated by published
measurements of the rate at which ephemeral active regions appear.
Title: The New Science of the Sun
Authors: Title, A. M.
Bibcode: 2001AGUSM..SH52B01T
Altcode:
No abstract at ADS
Title: The New Science of the Sun
Authors: Title, A. M.
Bibcode: 2001AGUSM..SA52B01T
Altcode:
No abstract at ADS
Title: The New Science of the Sun
Authors: Title, A. M.
Bibcode: 2001AAS...198.6801T
Altcode: 2001BAAS...33..890T
The past decade has seen a revolution in the scope, amount, and the
quality of solar data. Quantitative and coordinated observations
join the processes in the deep interior to those in the outer
atmosphere. The most important lesson the Sun is now teaching us
is that the parallel development of quantitative measurements with
numerical simulation and theory can produce a physical understanding
of the complex phenomena that occur over a range wide range in
densities, pressures, temperatures, and plasma betas. Because the
Sun is the only astrophysical object that can be studied in detail,
understanding the physics of the Sun is a key to unraveling puzzles
throughout astrophysics. The results discussed will be illustrated
with movies derived from a variety of observations, calculations,
and numerical simulations.
Title: On the Relation of G-Band Bright Points to the Photospheric
Magnetic Field
Authors: Berger, T. E.; Title, A. M.
Bibcode: 2001ApJ...553..449B
Altcode:
Cotemporal observations in the 4305 Å G-band and Ca II λ3933 K-line,
Fe I 6302 Å magnetograms, and 6563 Å Hα images are used to study the
relation of G-band bright points (GBPs) to magnetic elements in the
photosphere. Angular resolution of 0.2" and 0.3" is achieved in the
best G-band and magnetogram images, respectively. Single magnetogram
sensitivity of 120-150 gauss (Φmin~1016 Mx)
is achieved. Small-scale GBPs appear both in intergranular lanes
and on the edges of certain bright, rapidly expanding granules. The
latter class of GBPs are nonmagnetic (at the flux limit) and are
a source of confusion in magnetic element studies. The large-scale
pattern of GBPs and magnetic flux in plage are highly correlated;
GBPs occur preferentially on the periphery of extended plage regions,
which are primarily demarcated by dark or neutral-contrast regions
(e.g., pores or unresolved structures). On subarcsecond scales, GBPs
are cospatial (to within an average of 0.24") and comorphous with
magnetic elements in intergranular lanes; larger flux concentrations
appear more diffuse than the associated GBP groupings. The average peak
flux density of GBPs in the data set is ~160 gauss. No significant
trend in GBP flux density as a function of either contrast or size
is found. Rings of magnetic elements on 5" scales remain very stable
for periods on the order of hours. GBPs trace the temporal evolution
of magnetic elements closely: there is no indication of a lead or lag
(to within the 30-90 s precision of our data) in the appearance of GBPs
relative to the appearance of magnetic elements. Pore formation via
the accumulation of magnetic elements at a flow-field sink is seen in
the data set. Magnetic elements and granules are continually advected
into pores by the photospheric flow field.
Title: Intercomparison of SOUP, ASP, LPSP, and MDI magnetograms
Authors: Berger, T.; Lites, B.; Martinez-Pillet, V.; Tarbell, T.;
Title, A.
Bibcode: 2001AGUSM..SP51B12B
Altcode:
We compare simultaneous magnetograms of a solar active region taken by
the Advanced Stokes Polarimeter (ASP) and the Solar Optical Universal
Polimeter (SOUP) in 1998. In addition we compare magnetograms taken by
the La Palma Stokes Polarimeter (LPSP), the Michelson Doppler Imager
(MDI) on SOHO, and the SOUP instrument in 2000. The SOUP instrument on
the Swedish Vacuum Solar Telescope (SVST) attains the highest spatial
resolution but has the least understood calibration; the ASP on the Dunn
Solar Telescope (DST) at Sacramento Peak attains the highest magnetic
field precision. The goal of the program is to better quantify the
SOUP magnetograms and thereby study magnetic element dynamics in the
photosphere with higher precision.
Title: More Rotating Sunspot Observations by TRACE With Twisting
EUV Coronal Fans
Authors: Nightingale, R. W.; Shine, R. A.; Brown, D. S.; Wolfson,
C. J.; Frank, Z. A.; Title, A. M.
Bibcode: 2001AGUSM..SH41B11N
Altcode:
In an on-going search several sunspots, rotating about their umbral
centers, have been identified in TRACE photospheric white light (WL)
images. In many cases the rotation can also be seen in the corresponding
UV (1600 Å) and/or EUV (171, 195 Å) images. Preliminary analysis of
one such rotating sunspot and the coronal response to the rotation,
observed in AR9114 on August 8-10, 2000, was presented at the fall
AGU meeting (Nightingale et al., Abstract SH11A-10, EOS, AGU 2000 Fall
Meeting, Vol. 81, p. F977, Nov. 2000). Further detailed analysis and
modeling of this event, where loops appear to cross over one another,
is in progress. Meanwhile, we are finding other examples within the
TRACE data set. Twisting EUV coronal fans have been observed above
rotating sunspots on August 16, 1999 for AR8667, where a sigmoid was
visible in Yohkoh SXT data, and on May 20, 2000. Several rotating
sunspots were also seen in the active region of the July 14, 2000
Bastille Day event. More recent rotations observed only in WL and UV
occurred on December 11 and 22, 2000. Movies of some of these rotations
will be shown, as well as magnetic field data from MDI on SOHO where
available. Analysis of the rotational rates of the sunspots will be
given. These observations display the coupling of the magnetic field
from the photosphere into the corona. This work was supported by NASA
under contract NAS5-38099.
Title: The New Science of the Sun
Authors: Title, A. M.
Bibcode: 2001AGUSM..SM52C01T
Altcode:
No abstract at ADS
Title: How the Sun Maintains its Magnetic Network
Authors: Simon, G. W.; Title, A. M.; Weiss, N. O.
Bibcode: 2001AAS...198.8601S
Altcode: 2001BAAS...33..913S
The MDI experiment on SOHO has revealed a `magnetic carpet' dominated
by the emergence of bipolar magnetic flux in ephemeral active regions,
which subsequently split into small flux elements that drift into the
magnetic network. The effects of granular and supergranular convection
on these flux elements are represented here by kinematic modeling:
Elementary flux tubes are transported passively by the supergranular
flow, while experiencing small random displacements produced by
granulation. They end up in the magnetic network that surrounds the
supergranules, where they eventually meet oppositely directed fields and
are annihilated. The model calculations show that the total unsigned
magnetic flux will decay within a few days unless it is continually
replenished. A statistically steady state with a total unsigned
flux of 2-3 x 1023 Mx over the whole solar surface can be
maintained if bipolar flux emerges at a rate of 7 x 1022
Mx d-1, as indicated by published measurements of the rate
at which ephemeral active regions appear.
Title: The New Science of the Sun
Authors: Title, A. M.
Bibcode: 2001AGUSM..SP52A01T
Altcode:
The past decade has seen a revolution in the scope, amount, and the
quality of solar data. Quantitative and coordinated observations
join the processes in the deep interior to those in the outer
atmosphere. The most important lesson the Sun is now teaching us
is that the parallel development of quantitative measurements with
numerical simulation and theory can produce a physical understanding
of the complex phenomena that occur over a range wide range in
densities, pressures, temperatures, and plasma betas. Because the
Sun is the only astrophysical object that can be studied in detail,
understanding the physics of the Sun is a key to unraveling puzzles
throughout astrophysics. The results discussed will be illustrated
with movies derived from a variety of observations, calculations,
and numerical simulations.
Title: On the Formation of Polar Spots in Sun-like Stars
Authors: Schrijver, Carolus J.; Title, Alan M.
Bibcode: 2001ApJ...551.1099S
Altcode:
We simulate the photospheric magnetic field on very active cool stars
using a flux injection and surface distribution model with strictly
solar parameters, including an 11 yr sunspot cycle and associated
butterfly pattern. The only free parameter is the magnitude of the
cycle. We demonstrate that the combination of supergranulation-driven
dispersal and meridional advection of the field on a very active
Sun-like star leads to a strong polar cap field. The polar caps contain
so much flux that in comparable environments on the Sun convection is
suppressed; it appears inevitable that this leads to the formation
of (clusters of) starspots within large unipolar areas that form at
high latitudes. The model exhibits a peak total flux in the polar cap
regions that is roughly proportional to the cycle amplitude for active
regions, A0, whereas the total absolute flux covering the
stellar surface has a significantly weaker than linear dependence on
A0. We find, for example, that for a star with a rotation
period of P~6 days, the total absolute flux on the star is ~10 times
that characteristic of the active Sun, while the peak polar cap flux is
stronger by a factor of ~30. Within the polar caps of such active stars,
flux concentrations coagulate to form relatively large clusters. The
tendency for larger flux concentrations to disperse more slowly causes
the polar cap flux to be concentrated in a more restricted latitude
range with increasing activity; the corresponding longitudinally
averaged flux density in the polar caps of the simulated star with P~6
days reaches ~300-500 Mx cm-2. The polar cap field in these
simulations displays a ring of one polarity at high latitudes around a
polar patch of the opposite polarity during much of the spot cycle. This
bipolar pattern forms a persistent flux reservoir, so that the cycle
modulation of the polar cap flux of an active star is relatively weak,
consistent with observations of polar cap spot coverage on active
cool stars. Based on these model results, we propose that polar spots
are consistent with a dynamo like that of the Sun for a sufficiently
enhanced emergence frequency of active regions.
Title: Today's Science of the Sun -- Part 2
Authors: Schrijver, Carolus J.; Title, Alan M.
Bibcode: 2001S&T...101c..34S
Altcode:
No abstract at ADS
Title: Today's Science of the Sun -- Part 1
Authors: Schrijver, Carolus J.; Title, Alan M.
Bibcode: 2001S&T...101b..34S
Altcode:
No abstract at ADS
Title: High-resolution Solar Polarimetry with Sunrise
Authors: Schmidt, W.; Solanki, S. K.; Schüssler, M.; Curdt, W.;
Lites, B. W.; Title, A. M.; Martinez Pillet, V.
Bibcode: 2001AGM....18S1001S
Altcode:
Sunrise is a 1m balloon-borne solar telescope. It is equipped with
a spectrograph polarimeter which combines vector-polarimetry in the
visible with diagnostic spectroscopy in the visible and the UV, down
to 200 nm. The instrumentation includes a filter-magnetograph and a
medium-band filtergraph. The wavelength bands of the latter include
the CH-band (430.6 nm) and a UV continuum at 205 nm. Diffraction
limited resolution in the UV will be achieved by employing a phase
diversity technique. The main telescope is based on a lightweight
silicon-carbide mirror, developed within the Solar Lite program. During
the long-duration flight at Antarctica, foreseen for late 2005, Sunrise
will continuously observe the sun for a period of about ten days,
with constant image quality across the full field of view. In-flight
alignment of the telescope optics will be controlled by a wavefront
sensor. The main goal of Sunrise is to understand the structure and
dynamics of the magnetic field in the atmosphere of the sun. To this
end, Sunrise will observe small magnetic flux concentrations with
dimensions of less than 70 km with high polarimetric accuracy. At the
same time, Sunrise will provide diffraction-limited filtergrams of
the photosphere and chromosphere with a resolution down to 35 km at
a wavelength of 200 nm.
Title: Sunspots: Moving Magnetic Features and Moat Flow
Authors: Shine, R.; Title, A.
Bibcode: 2000eaa..bookE2038S
Altcode:
Most mature SUNSPOTS and some large SUNSPOT PORES are surrounded, at
least in part, by a zone which is free of stationary magnetic field
(e.g. PLAGE, network) and which exhibits a radially outward horizontal
mass flow. This zone is called a sunspot `moat'. The most notable
features in the moat are small magnetic structures of mixed polarity
called moving magnetic features (MMFs). These are trans...
Title: Time Variability of the ``Quiet'' Sun Observed with
TRACE. II. Physical Parameters, Temperature Evolution, and Energetics
of Extreme-Ultraviolet Nanoflares
Authors: Aschwanden, Markus J.; Tarbell, Ted D.; Nightingale, Richard
W.; Schrijver, Carolus J.; Title, Alan; Kankelborg, Charles C.;
Martens, Piet; Warren, Harry P.
Bibcode: 2000ApJ...535.1047A
Altcode:
We present a detailed analysis of the geometric and physical
parameters of 281 EUV nanoflares, simultaneously detected with the
TRACE telescope in the 171 and 195 Å wavelengths. The detection and
discrimination of these flarelike events is detailed in the first paper
in this series. We determine the loop length l, loop width w, emission
measure EM, the evolution of the electron density ne(t) and
temperature Te(t), the flare decay time τdecay,
and calculate the radiative loss time τloss, the conductive
loss time τcond, and the thermal energy Eth. The
findings are as follows: (1) EUV nanoflares in the energy range of
1024-1026 ergs represent miniature versions
of larger flares observed in soft X-rays (SXR) and hard X-rays
(HXR), scaled to lower temperatures (Te<~2 MK),
lower densities (ne<~109 cm-3),
and somewhat smaller spatial scales (l~2-20 Mm). (2) The cooling
time τdecay is compatible with the radiative cooling
time τrad, but the conductive cooling timescale
τcond is about an order of magnitude shorter, suggesting
repetitive heating cycles in time intervals of a few minutes. (3)
The frequency distribution of thermal energies of EUV nanoflares,
N(E)~10-46(E/1024)-1.8 (s-1
cm-2 ergs-1) matches that of SXR microflares
in the energy range of 1026-1029, and exceeds
that of nonthermal energies of larger flares observed in HXR by a
factor of 3-10 (in the energy range of 1029-1032
ergs). Discrepancies of the power-law slope with other studies, which
report higher values in the range of a=2.0-2.6 (Krucker & Benz;
Parnell & Jupp), are attributed to methodical differences in the
detection and discrimination of EUV microflares, as well as to different
model assumptions in the calculation of the electron density. Besides
the insufficient power of nanoflares to heat the corona, we find also
other physical limits for nanoflares at energies <~1024
ergs, such as the area coverage limit, the heating temperature limit,
the lower coronal density limit, and the chromospheric loop height
limit. Based on these quantitative physical limitations, it appears
that coronal heating requires other energy carriers that are not
luminous in EUV, SXR, and HXR.
Title: The Solar-B Focal Plane Package
Authors: Berger, T. E.; Title, A. M.; Tarbell, T. D.; Lites, B. W.;
Elmore, D. F.
Bibcode: 2000SPD....31.0292B
Altcode: 2000BAAS...32..827B
Solar-B is a Japanese national space science mission of the Institute
of Space and Astronautical Sciences (ISAS) with participation from
US and UK research groups. The satellite consists of a 50-cm optical
telescope and Focal Plane Package (FPP) designed for high resolution
photospheric and chromospheric imaging and spectro-polarimetry as
well as two coronal instruments: the X-Ray Telescope (XRT) and the
Extreme-ultraviolet Imaging Spectrometer (EIS). Solar-B will be
launched into a Sun-synchronous orbit in August of 2004. A team of
Lockheed Martin Solar and Astrophysics Laboratory (LMSAL), High Altitude
Observatory, and ISAS personnel are designing the FPP instrument. It
consists of a narrow-band tunable birefringent filter system,
a wide band interference filter system, and a spectro-polarimeter
system for very high sensitivity Stokes polarimetry, all of which
will be fabricated at LMSAL. We describe the main science goals of
the FPP as well as the current instrument design and performance
characteristics. This work is supported by NASA contract NAS8-00014
(Solar-B FPP).
Title: Report on the Astronomy and Astrophysics Decadal Survey
Authors: Knoelker, M.; Title, A.
Bibcode: 2000SPD....31.0702K
Altcode: 2000BAAS...32Q.839K
The Decadal Survey of Astronomy and Astrophysics is a review that
recommends priorities for all projects in astrophysics in the coming
decade. The priorities are established by a secret vote of the members
of the Astronomy and Astrophysics Survey Committee (AASC). Voting is on
projects recommended by a set of discipline panels. One of us (Knoelker)
chaired the Solar Panel and the other (Title) was a member of the AASC
and vice chair of the Solar Panel. Christopher McKee of the University
of California and Joseph Taylor of Princeton University jointly chaired
the current review. Projects were prioritized in categories of large,
moderate, and small for both ground and space. The output of the study
is a report - Astronomy and Astrophysics in the New Millennium. The
report is in two volumes the main report and an appendix that contains
reports of the AASC panels. We will discuss the process and the
priorities of the survey with special emphasis of the impacts on and
implications for Solar Physics.
Title: Filaments and their Magnetic Structure
Authors: Title, A.
Bibcode: 2000SPD....31.0219T
Altcode: 2000BAAS...32..814T
Filaments are features associated with magnetic flux inversion
boundaries. Such boundaries occur inside or between active region
and around the polar cap. The TRACE satellite has observed numerous
filaments and similarities between all of them have been noted. In
particular there are fine structured flows alone filaments and when
filaments are activated there are loops over the flux inversion
boundaries that range from perpendicular to the filament to highly
oblique - sheared loops. Often active region filaments have a
characteristic S shape. This poster presents example TRACE movies that
illustrate the above mentioned features of filaments. Also presented
are a series of potential field models of flux inversion lines and
pairs of flux inversion lines (quadpole configurations) that have many
of the features that are seen in the TRACE movies.
Title: Report on the Mission Definition Study for the Solar Dynamics
Observatory
Authors: Title, A.
Bibcode: 2000SPD....31.0704T
Altcode: 2000BAAS...32..839T
The Solar Dynamics Observatory (SDO) is the first Living with a Star
mission. This talk reports on the results of the mission definition
study for SDO. The study assumes a 2006 launch and a cost cap of \250
million dollars. The mission study baseline includes a program that
creates coordinated theory groups that attack Scientific Challenges
critical to understanding the physics of the Sun from the interior to
the interaction with the Earth. The SDO is a geosynchronous satellite
that carries instruments that make Dopplergrams, vector magnetograms,
images of the atmosphere in a range of visible, UV, and EUV wavelength
bands, map the corona from 1.05 to 18 solar radii, and makes precision
radiometric measurements over a broad spectral band. SDO carries 12
4096^2$ CCD detectors and has a continuous downlink data rate of 160
megabits per second. All of the SDO data will be available in near
real time from a online data archive.
Title: Magnetic fields below, on and above the solar surface
Authors: Title, Alan
Bibcode: 2000RSPTA.358..657T
Altcode:
The Sun is the only star that can be studied in detail. The last
decade saw a revolution in the scope, amount, and the quality of solar
data. Coordinated quantitative observations link the processes in the
deep interior to those in the outer atmosphere. Numerical simulations
and theoretical modelling have produced detailed agreement with
observations. The most important lesson the Sun is now teaching us
is that the parallel development of quantitative measurements with
numerical simulation and theory can produce a physical understanding
of the complex nonlinear phenomena that occur over a wide range in
densities, pressures, temperatures and plasma betas. Understanding the
physics of the Sun is a major key to unravelling puzzles throughout
astrophysics.
Title: Here Comes Solar Probe!
Authors: Möbius, E.; Gloeckler, G.; Goldstein, B.; Habbal, S.;
McNutt, R.; Randolph, J.; Title, A.; Tsurutani, B.
Bibcode: 2000AdSpR..25.1961M
Altcode:
Despite recent advances, fundamental questions remain about the nature
of the solar corona and the solar wind: 1) What heats the corona and
accelerates the solar wind? 2) Where do the different types of solar
wind originate? 3) Where and how are energetic particles produced and
transported near the Sun? 4) What role do plasma turbulence and waves
play in the corona and solar wind production? 5) What is the nature
of the magnetic field and photospheric structures near the solar
poles? Flying a trajectory perpendicular to the Earth-Sun line during
its perihelion passage, Solar Probe will use in-situ and imaging
instruments to provide the first three dimensional viewing of the
corona, direct observations of solar polar regions, and local sampling
of the solar environment. These primary observations are complemented
by context-setting measurements and Earth-based observations. Solar
Probe is currently scheduled for launch in February 2007 as the third
in the new Outer Planets/Solar Probe mission line of NASA and will
arrive at the Sun in 2010 under solar maximum conditions with a second
closest approach near solar minimum in 2015
Title: Highlights of the TRACE Mission
Authors: Title, Alan
Bibcode: 2000IAUJD...7E...1T
Altcode:
The TRACE mission was constructed to determine the effect of the
magnetic carpet, the pervasive mixed polarity of the magnetic field in
the solar surface, on the outer atmosphere. TRACE forms images over a
temperature range from 4,000 K to nearly 4,000,000 K. The normal time
cadence for images in EUV lines, which span the temperature region
from 600,000 to 4,000,000 K, is 20 seconds and visible and UV cadences,
which span the temperature range from 4,000 to 60,000 K, can be as fast
as a few seconds . A primary result of the TRACE mission is that the
transition region and corona are structured on a scale that is often
limited by the telescopes 0.5 arc second (370 km on the Sun) pixel
size. These fine structures are intermixed in temperature throughout
the corona and they are almost never in thermal equilibrium. In some of
the strong resonance lines there is sufficient density for significant
scattering. Besides the emitting million degree gases that define the
corona, there is great deal of cool material (<30,000 K) intermixed
throughout the outer atmosphere. The cooler gases are visible by the
absorption of the EUV light from the million degree gases. Videos of
the TRACE data will be presented during the talk.
Title: Dynamics of Transition Region `Moss' at high time resolution
Authors: De Pontieu, B.; Berger, T. E.; Schrijver, C. J.; Title, A. M.
Bibcode: 1999SoPh..190..419D
Altcode:
Recent observations of solar active regions made with the Transition
Region and Coronal Explorer (TRACE) have revealed finely textured,
low-lying extreme ultraviolet (EUV) emission, called the moss. It
appears as a bright, dynamic pattern with dark inclusions, structured
on spatial scales of 1 to 3 Mm. The moss has been interpreted as the
upper transition region above active region plage and below relatively
hot loops. Here we study the temporal variability of the morphology of
the moss using a 2-hr time sequence of high-cadence TRACE 171 Å images
and G-band, Ca ii K-line and Hα filtergrams from the Swedish Vacuum
Solar Telescope (SVST, La Palma) on 1 June 1999. The data provide a
unique view of the connections between the photosphere, chromosphere,
transition region and corona in an active region. We find that the
moss is dynamic on time scales of 10-30 s due to intrinsic changes
in brightness, obscuration by chromospheric jets and motion caused
by physical interaction with these jets. The temporal variations of
the bright moss elements occur on shorter time scales than those of
the Ca ii K-line bright points. The bright moss elements generally do
not occur directly above the G-band or Ca ii K-line bright points in
the photosphere or lower chromosphere. This suggests that the upper
transition region emission often occurs at the interface of neighboring
flux tubes. The temporal variability of the moss brightness on 30
s time scales may suggest that the energy source of these intensity
changes occurs relatively locally (height <10 000 km).
Title: What is Moss?
Authors: Berger, T. E.; De Pontieu, B.; Fletcher, L.; Schrijver,
C. J.; Tarbell, T. D.; Title, A. M.
Bibcode: 1999SoPh..190..409B
Altcode:
TRACE observations of active regions show a peculiar extreme ultraviolet
(EUV) emission over certain plage areas. Termed `moss' for its spongy,
low-lying, appearance, observations and modeling imply that the
phenomenon is caused by thermal conduction from 3-5 MKcoronal loops
overlying the plage: moss is the upper transition region emission of
hot coronal loops. The spongy appearance is due to the presence of
chromospheric jets or `spicules' interspersed with the EUV emission
elements. High cadence TRACE observations show that the moss EUV
elements interact with the chromospheric jets on 10 s time scales. The
location of EUV emission in the moss does not correlate well to the
locations of underlying magnetic elements in the chromosphere and
photosphere, implying a complex magnetic topology for coronal loop
footpoint regions. We summarize here the key observations leading to
these conclusions and discuss new implications for understanding the
structuring of the outer solar atmosphere.
Title: Active regions losing their moorings by subsurface reconnection
Authors: Schrijver, Carolus J.; Title, Alan M.
Bibcode: 1999SoPh..188..331S
Altcode:
The properties of emerging active regions suggest that they
originate from deep flux bundles with a field strength well above the
equipartition value, so that they can resist strong deformation by
convection as they surface. Yet upon flux emergence, the field appears
in a multitude of bundles with a field strength near to equipartition
with the pressure component that is associated with the convective
motions. During the subsequent decay of active regions, the flux
disperses in a random walk that seems to be caused uniquely by the
flows in the near-surface convection. We propose that this apparently
untethered random walk is the consequence of subsurface reconnection,
which leads to the formation of flexible weak-field connections between
the strong, buoyant top segments, cut loose from the deep source
region. The frequent reconnection between flux tubes underneath each of
the polarities in the active region acts to maintain an approximately
vertical organization of the subsurface field. We concur with earlier
studies that the distribution of the field can be described by the
horizontal dispersal of a scalar at least in these layers near the
surface, because in addition to this combing of the field, mixing-length
models suggest that the horizontal diffusion coefficient is almost
constant down to a depth of some 10 000 km. Our model predicts that the
sub-surface reconnection between fields of opposite polarity causes
the surface field to be disconnected from the deep source region on
a time scale that is in fair agreement with the observed lifetimes
of active regions of a range of sizes. We explore whether branching
of flux bundles into ever smaller bundles between the bottom of the
convective envelope and the photosphere allows the limited bending of
flux tubes by convection that is required to induce reconnection.
Title: High-resolution Imaging of the Solar Chromosphere/Corona
Transition Region
Authors: Berger, T. E.; De Pontieu, B.; Schrijver, C. J.; Title, A. M.
Bibcode: 1999ApJ...519L..97B
Altcode:
The properties of a previously unresolved extreme-ultraviolet (EUV)
emission in solar active regions are examined using coordinated data
sets from the Transition Region and Coronal Explorer (TRACE) satellite,
the Michelson Doppler Imager on the Solar and Heliospheric Observatory
satellite, the Soft X-Ray Telescope (SXT) on the Yohkoh satellite, and
the ground-based Swedish Vacuum Solar Telescope (SVST) on La Palma. The
emission appears most prominently in TRACE Fe IX/Fe X 171 Å images
as a bright dynamic network surrounding dark inclusions on scales of
2-3 Mm, confined to layers approximately 1-3 Mm thick with base heights
approximately 2-4 Mm above the photosphere. It is seen only above plage
regions that underlie (3-5)×106 K coronal loops visible
in SXT images. The bright EUV elements emit at temperatures of about
106 K. Fine-scale motions and brightness variations of the
emission occur on timescales of 1 minute or less. The dark inclusions
correspond to jets of chromospheric plasma seen in simultaneous SVST
filtergrams in the wings of Hα. The combined characteristics imply
that we are at least partially resolving the structure and dynamics
of the conductively heated upper transition region between the solar
chromosphere and corona.
Title: A new view of the solar outer atmosphere by the Transition
Region and Coronal Explorer
Authors: Schrijver, C. J.; Title, A. M.; Berger, T. E.; Fletcher, L.;
Hurlburt, N. E.; Nightingale, R. W.; Shine, R. A.; Tarbell, T. D.;
Wolfson, J.; Golub, L.; Bookbinder, J. A.; DeLuca, E. E.; McMullen,
R. A.; Warren, H. P.; Kankelborg, C. C.; Handy, B. N.; De Pontieu, B.
Bibcode: 1999SoPh..187..261S
Altcode:
The Transition Region and Coronal Explorer (TRACE) - described in the
companion paper by Handy et al. (1999) - provides an unprecedented
view of the solar outer atmosphere. In this overview, we discuss the
initial impressions gained from, and interpretations of, the first
million images taken with TRACE. We address, among other topics,
the fine structure of the corona, the larger-scale thermal trends,
the evolution of the corona over quiet and active regions, the high
incidence of chromospheric material dynamically embedded in the coronal
environment, the dynamics and structure of the conductively dominated
transition region between chromosphere and corona, loop oscillations
and flows, and sunspot coronal loops. With TRACE we observe a corona
that is extremely dynamic and full of flows and wave phenomena, in
which loops evolve rapidly in temperature, with associated changes in
density. This dynamic nature points to a high degree of spatio-temporal
variability even under conditions that traditionally have been referred
to as quiescent. This variability requires that coronal heating can
turn on and off on a time scale of minutes or less along field-line
bundles with cross sections at or below the instrumental resolution
of 700 km. Loops seen at 171 Å (∼1 MK) appear to meander through
the coronal volume, but it is unclear whether this is caused by the
evolution of the field or by the weaving of the heating through the
coronal volume, shifting around for periods of up to a few tens of
minutes and lighting up subsequent field lines. We discuss evidence
that the heating occurs predominantly within the first 10 to 20 Mm
from the loop footpoints. This causes the inner parts of active-region
coronae to have a higher average temperature than the outer domains.
Title: The transition region and coronal explorer
Authors: Handy, B. N.; Acton, L. W.; Kankelborg, C. C.; Wolfson, C. J.;
Akin, D. J.; Bruner, M. E.; Caravalho, R.; Catura, R. C.; Chevalier,
R.; Duncan, D. W.; Edwards, C. G.; Feinstein, C. N.; Freeland, S. L.;
Friedlaender, F. M.; Hoffmann, C. H.; Hurlburt, N. E.; Jurcevich,
B. K.; Katz, N. L.; Kelly, G. A.; Lemen, J. R.; Levay, M.; Lindgren,
R. W.; Mathur, D. P.; Meyer, S. B.; Morrison, S. J.; Morrison, M. D.;
Nightingale, R. W.; Pope, T. P.; Rehse, R. A.; Schrijver, C. J.;
Shine, R. A.; Shing, L.; Strong, K. T.; Tarbell, T. D.; Title, A. M.;
Torgerson, D. D.; Golub, L.; Bookbinder, J. A.; Caldwell, D.; Cheimets,
P. N.; Davis, W. N.; Deluca, E. E.; McMullen, R. A.; Warren, H. P.;
Amato, D.; Fisher, R.; Maldonado, H.; Parkinson, C.
Bibcode: 1999SoPh..187..229H
Altcode:
The Transition Region and Coronal Explorer (TRACE) satellite, launched
2 April 1998, is a NASA Small Explorer (SMEX) that images the solar
photosphere, transition region and corona with unprecedented spatial
resolution and temporal continuity. To provide continuous coverage
of solar phenomena, TRACE is located in a sun-synchronous polar
orbit. The ∼700 Mbytes of data which are collected daily are made
available for unrestricted use within a few days of observation. The
instrument features a 30-cm Cassegrain telescope with a field of view
of 8.5×.5 arc min and a spatial resolution of 1 arc sec (0.5 arc sec
pixels). TRACE contains multilayer optics and a lumogen-coated CCD
detector to record three EUV wavelengths and several UV wavelengths. It
observes plasmas at selected temperatures from 6000 K to 10 MK with
a typical temporal resolution of less than 1 min.
Title: TRACE Observations of the Birth and Evolution of Emerging
Flux Regions
Authors: Wolfson, C. J.; Schrijver, C. J.; Title, A. M.
Bibcode: 1999AAS...194.7805W
Altcode: 1999BAAS...31..961W
TRACE is uniquely able to observe the birth and evolution of emerging
flux regions, X-ray ``bright points" and bona-fide active regions due to
its high spatial resolution, wide temperature coverage, and continual
solar viewing. On board memory limitations and photon statistics,
however, do force compromises. In this poster we discuss several cases
of emerging flux and subsequent region evolution. These include events
at different aspect angles (on disk and near the limb), near and not
near existing active regions with which there can be interconnection,
and regions that disappear in a couple of days as well as those which
develop more fully. Some of the observations include several channels
(temperature regimes) and some concentrate on higher temporal resolution
with less spectral coverage. Analysis of some of the latter include
MDI magnetograms at a one minute cadence. This work was supported by
NASA contract NAS5-38099.
Title: Dynamics of Transition Region Moss
Authors: Berger, T. E.; de Pontieu, B.; Schrijver, C. J.; Title, A. M.
Bibcode: 1999AAS...194.7901B
Altcode: 1999BAAS...31..963B
We examine the dynamics of solar transition region "moss", the 10(6)
K EUV emission at the footpoint regions of 2--3 MK active region coronal
loops. Comparisons of TRACE 171 Angstroms movies with SVST (La Palma) Ca
II K-line, Hα , and G-band movies are made. Local Correlation Tracking
(LCT) flowmapping techniques are used to establish the photospheric
flowfield in plage regions with and without associated moss. The
relation of moss emission to chromospheric spicules or fibrils is
examined in detail using Hα movies and dopplergrams. In addition,
several microflare events occuring in plage regions are analyzed using
TRACE and SVST movies. This research was supported by NASA contract
NAS5-38099 (TRACE) and NASA SR&T grant NASW-98008.
Title: SONAR - Solar Near-surface Active Region Rendering
Authors: Scherrer, P. H.; Hoeksema, J. T.; Kosovichev, A. G.; Duvall,
T. L.; Schrijver, K. J.; Title, A. M.
Bibcode: 1999AAS...194.7606S
Altcode: 1999BAAS...31Q.957S
The processes in the top 20,000-km of the Sun's convection zone govern
the growth and decay of active regions and provide the magnetic flux and
energy for the active phenomena of the upper solar atmosphere. The MDI
experiment on SOHO has demonstrated that this region is now accessible
to study by means of local helioseismology. However, SOHO provides
neither the temporal nor spatial resolution and coverage necessary
to exploit these techniques to study the eruption and evolution of
active region magnetic structures. The SONAR mission with moderate
resolution full disk Doppler and vector magnetic field observations,
and atmospheric magnetic connectivity observations via EUV imaging
can provide the necessary data. The science motivation and general
instrumentation requirements for the mission are presented.
Title: The Solar-B Solar Optical Telescope Focal Plane Package
Authors: Levay, M.; Berger, T.; Rosenberg, W.; Tarbell, T.; Title,
A.; Bogdan, T.; Elmore, D.; Lites, B.
Bibcode: 1999AAS...194.7610L
Altcode: 1999BAAS...31R.957L
The primary goal of the Solar-B mission is to understand the physical
processes responsible for dynamics and heating of the outer solar
atmosphere. The Focal Plane Package (FPP) instrument for the 50-cm Solar
Optical Telescope provides precise measurements of the vector magnetic
field, vertical and horizontal flows, and thermal conditions in the
photosphere and low chromosphere with spatial resolution as high as
0.16 arcsec and a field-of-view as large as 320 x 160 arcsec. The FPP
can measure continuously and at high cadence to follow the evolution
of solar features. The FPP consists of broad ( 8 Angstroms) and narrow
( 100 m Angstroms) filters and a spectro-polarimeter that provides
precise polarimetry with high spectral resolution ( 25 m Angstroms). A
correlation tracker and tip-tilt mirror ensure that all focal planes
are stable to better than 0.01 arcsec. A major design consideration
of the FPP is cooperative science operations with the other Solar-B
instruments. Solar-B is a Japanese mission with US and UK partners;
S. Tsuneta is the PI of the Solar Optical Telescope and A. Title the
US PI of the FPP. It is scheduled to launch in Japanese FY 2004.
Title: A new view of the solar corona from the transition region
and coronal explorer (TRACE)
Authors: Golub, L.; Bookbinder, J.; Deluca, E.; Karovska, M.; Warren,
H.; Schrijver, C. J.; Shine, R.; Tarbell, T.; Title, A.; Wolfson,
J.; Handy, B.; Kankelborg, C.
Bibcode: 1999PhPl....6.2205G
Altcode:
The TRACE Observatory is the first solar-observing satellite in the
National Aeronautics and Space Administration's (NASA) Small Explorer
series. Launched April 2, 1998, it is providing views of the solar
transition region and low corona with unprecedented spatial and
temporal resolution. The corona is now seen to be highly filamented,
and filled with flows and other dynamic processes. Structure is seen
down to the resolution limit of the instrument, while variability and
motions are observed at all spatial locations in the solar atmosphere,
and on very short time scales. Flares and shock waves are observed,
and the formation of long-lived coronal structures, with consequent
implications for coronal heating models, has been seen. This overview
describes the instrument and presents some preliminary results from
the first six months of operation.
Title: Dynamics and Plasma Diagnostics of Transition Region ``Moss''
using SOHO/CDS, TRACE and SVST (La Palma)
Authors: de Pontieu, B.; Berger, T. E.; Fletcher, L.; Schrijver,
C. J.; Title, A. M.
Bibcode: 1999AAS...194.7804D
Altcode: 1999BAAS...31..961D
Recent observations of solar active regions with the Transition
Region And Coronal Explorer (TRACE) have revealed finely textured,
low-lying extreme ultraviolet (EUV) emission, called the ``moss'',
appearing as a bright dynamic pattern with dark inclusions. The moss
has been interpreted as the upper transition region by Berger et al.,
(1999). In this poster we study the physical conditions in the moss
plasma, as well as its dynamics and connections to photosphere and
chromosphere. Using simultaneous SOHO Coronal Diagnostic Spectrometer
(CDS) and TRACE observations of Active Region (AR) 8227 on 30-May-1998
we determine the physical parameters of the moss material. We find T_e =
0.6-1.5 10(6) K and n_e = 2-5 10(9) cm(-3) at a temperature of 1.3 10(6)
K. The pressure in the moss plasma is higher than that in coronal loops
observed in the TRACE Fe IX/X 171 Angstroms passband, and moss emission
is associated with high temperature loops, observed by SXT and by CDS
in lines of T_max > 2.5 10(6) K. The volume filling factor of the
moss plasma is of the order 0.1 and the path along which the emission
originates is of the order 1,000 km long. We examine the dynamics of
the moss plasma, by making comparisons of TRACE 171 Angstroms movies
with SVST (La Palma) Ca II K-line, Hα , and G-band movies. Local
Correlation Tracking (LCT) flowmapping techniques are used to establish
the photospheric flowfield in plage regions with and without associated
moss. The relation of moss emission to chromospheric spicules or fibrils
is examined in detail using Hα movies and dopplergrams. In addition,
several miniflare events occuring in plage regions are analyzed using
TRACE and SVST movies. This research was supported by NASA contract
NAS5-38099 (TRACE) and NASA SR&T grant NASW-98008.
Title: Observations of Filaments
Authors: Title, A.; Schrijver, C.; Tarbell, T.; Shine, R.
Bibcode: 1999AAS...194.7905T
Altcode: 1999BAAS...31..963T
Filaments are clearly seen as absorption features in the TRACE FE
IX and XII images. Because of the 24 hour coverage of TRACE many
filaments have been observed on the disk and near the limb, and as
quiescent and active structures. A quiescent filament consists of many
parallel strands the run nearly parallel to the surface. The strands
are often at the TRACE resolution and are always in motion. Adjacent
strands often exhibit flows in opposite directions with speeds of
10 to 40 km/second. Filaments occasionally erupt explosive from the
surface. The initial accelerations have not been observed with a 30
second cadence. Velocities in the initial phase range between 200
and 400 km/s. Filaments are observed to erupt and travel out of the
TRACE field of view, erupt and fall back to the solar surface, and
erupt and travel a short distance before being constraint by overlying
fields. Examples of the dynamic structure of filaments and their modes
of eruption will be demonstrated in a video presentation.
Title: Dispersal of Magnetic Flux in the Quiet Solar Photosphere
Authors: Hagenaar, H. J.; Schrijver, C. J.; Title, A. M.; Shine, R. A.
Bibcode: 1999ApJ...511..932H
Altcode:
We study the random walk of magnetic flux concentrations on two
sequences of high-resolution magnetograms, observed with the Michelson
Doppler Imager on board SOHO. The flux contained in the concentrations
ranges from |Φ|=1018 Mx to |Φ|=1019 Mx, with
an average of |Φ|=2.5×1018 Mx. Larger concentrations tend
to move slower and live longer than smaller ones. On short timescales,
the observed mean-square displacements are consistent with a random
walk, characterized by a diffusion coefficient D(t<10 ks)=70-90
km2 s-1. On longer timescales, the diffusion
coefficient increases to D(t>30 ks)=200-250 km2
s-1, approaching the measurements for a five-day set of Big
Bear magnetograms, D~=250 km2 s-1. The transition
between the low and large diffusion coefficients is explained with
a model and simulations of the motions of test particles, subject to
random displacements on both the granular and supergranular scales,
simultaneously. In this model, the supergranular flow acts as a
negligible drift on short timescale, but dominates the granular
diffusion on longer timescales. We also investigate the possibility
that concentrations are temporarily confined, as if they were caught
in supergranular vertices, that form short-lived, relatively stable
environments. The best agreement of model and data is found for step
lengths of 0.5 and 8.5 Mm, associated evolution times of 14 minutes
and 24 hr, and a confinement time of no more than a few hours. On
our longest timescale, DSim(t>105)-->285
km2 s-1, which is the sum of the small- and
large-scale diffusion coefficients. Models of random walk diffusion on
the solar surface require a larger value: DWang=600+/-200
km2 s-1. One possible explanation for the
difference is a bias in our measurements to the longest lived, and
therefore slower concentrations in our data sets. Another possibility
is the presence of an additional, much larger diffusive scale.
Title: Coordinated Observations of Transition Region Dynamics using
TRACE and the SVST
Authors: Berger, T.; de Pontieu, B.; Schrijver, C.; Title, A.;
Scharmer, G.
Bibcode: 1999ASPC..183..365B
Altcode: 1999hrsp.conf..365B
No abstract at ADS
Title: The New Swedish Solar Telescope
Authors: Scharmer, G.; Owner-Petersen, M.; Korhonen, T.; Title, A.
Bibcode: 1999ASPC..183..157S
Altcode: 1999hrsp.conf..157S
No abstract at ADS
Title: The Dynamic Nature of the Solar Magnetic Field
Authors: Schrijver, C. J.; Title, A. M.
Bibcode: 1999ASPC..158...15S
Altcode: 1999ssa..conf...15S
No abstract at ADS
Title: The Transition Region and Coronal Explorer
Authors: Handy, B. N.; Deluca, E. E.; McMullen, R. A.; Schrijver,
C. J.; Tarbell, T. D.; Title, A. M.; Wolfson, C. J.
Bibcode: 1998AAS...193.1207H
Altcode: 1998BAAS...30R1269H
The Transition Region and Coronal Explorer (TRACE), launched 1 April
1998, will have at the time of this meeting been in orbit for just over
8 months. In that time, the instrument will have taken over 500,000
exposures of the sun in ultraviolet and extreme ultraviolet wavelengths,
will have completed three-forths of the nominal mission and will be
approaching the end of the first eclipse season. The TRACE telescope
is unique in its ability to observe in UV and EUV wavelengths at high
cadence with unprecedented resolution. We present a review of the TRACE
instrument and show current observations and results. We discuss the
performance of the instrument in terms of observational capabilities,
sensitivity, calibration, effects of aging on the instrument, CCD
effects, and contamination effects.
Title: The TRACE Mission: Initial Scientific Results
Authors: Title, A. M.; Tarbell, T. D.; Wolfson, J.; Schrijver, K.;
Fisher, R. R.; Gang, Th.; Golub, L.; McMullen, R. A.; Kankelborg,
C.; TRACE Collaboration
Bibcode: 1998AAS...19310008T
Altcode: 1998BAAS...30R1398T
TRACE (Transition Region and Coronal Explorer) is a Small Explorer
Mission (SMEX) devoted to studying the evolution and propagation
of fine-scale magnetic fields and plasma structures throughout the
solar atmosphere. The instrument consists of a telescope with a 30 cm
primary mirror, normal incidence coatings for three EUV bands (171,
195 and 284 Angstroms), and interference filters for UV bands (1216
to 1700 Angstroms) as well as white light (allowing the selection of
temperature ranges from ~ 6 000 to ~ 2 500 000 degrees K). The 1024
x 1024 CCD camera has a field of view of 8.5 arcmin with a spatial
resolution of 1 arcsec and exposure times of 0.002 to 260 sec with
a cadence as short as two seconds. The spacecraft was launched on
April 1, 1998, and first light for the telescope occurred on April
20. Observations have been collected nearly 24 hours per day since
then, with no significant problems in any segment of the spacecraft,
instrument, or mission operations. TRACE transmits about 3--4 GB of
data per week which gets automatically reformatted and becomes available
for the scientific community within approx. 24 hours. It is accessible
without restrictions (only guidelines) together with other informations
(technical details, educational material, movies, images,...) at:
http://vestige.lmsal.com/TRACE. The images reveal activity in the
solar atmosphere in stunning detail and include the first detailed
observations of a magnetic energy release. This magnetic reconnection
was observed on May 8, 1998, in a region of the solar atmosphere where
two sets of perpendicular magnetic loops expanded into each other (see
NASA Press Release 98-92). The TRACE mission has been developed and
operated by NASA's Goddard Space Flight Center, Lockheed Martin Solar
& Astrophysics Laboratory, Smithsonian Astrophysical Observatory,
and Montana State University.
Title: Diffraction Limited Imaging of the Sun from a Balloon
Authors: Title, A. M.; Rosenberg, W. J.
Bibcode: 1998AAS...19311304T
Altcode: 1998BAAS...30.1421T
Using light weight SiC mirror technology developed by IABG in Germany
it is possible to construct diffraction limited mirrors in diameters
up to 3.5 meters that are sufficiently stiff to maintain optical form
without active controls. A telescope now under construction with a one
meter diameter mirror has a total design weight of 200 kg. A 100 day
mission with a tunable optical filter with a resolution of 60,000 as
the focal plane instrument would allow fundamental measurements of the
interaction of convection and magnetic fields in quiet and active Sun.
Title: UV Observations with the Transition Region and Coronal Explorer
Authors: Handy, B. N.; Bruner, M. E.; Tarbell, T. D.; Title, A. M.;
Wolfson, C. J.; Laforge, M. J.; Oliver, J. J.
Bibcode: 1998SoPh..183...29H
Altcode:
The Transition Region and Coronal Explorer is a space-borne solar
telescope featuring high spatial and temporal resolution. TRACE
images emission from solar plasmas in three extreme-ultraviolet (EUV)
wavelengths and several ultraviolet (UV) wavelengths, covering selected
ion temperatures from 6000 K to 1 MK. The TRACE UV channel employs
special optics to collect high-resolution solar images of the H i
Lα line at 1216 Å, the C iv resonance doublet at 1548 and 1550 Å,
the UV continuum near 1550 Å, and also a white-light image covering
the spectrum from 2000-8000 Å.
Title: Measurements of Solar Magnetic Element Dispersal
Authors: Berger, Thomas E.; Löfdahl, Mats G.; Shine, Richard A.;
Title, Alan M.
Bibcode: 1998ApJ...506..439B
Altcode:
The dispersal of magnetic elements in the solar photospheric flow
field is studied by tracking individual ``magnetic bright points''
(MBPs) identified in a G-band 4305 Å filtergram time series obtained
at the 50 cm Swedish Vacuum Solar Telescope on La Palma, Spain. The time
series spans approximately 70 minutes with a field of view of 29" × 29"
near disk center. All images in the time series are restored to near
the telescope diffraction limit (~0.2" in the G band) using partitioned
phase diverse speckle techniques. Regions of enhanced magnetic network
and quiet Sun are examined. In the network region, automated tracking
of individual MBPs reveals approximately Gaussian diffusion, with
indications for slightly ``superdiffusive'' dispersal. The inferred
Gaussian diffusion coefficient is 60.4 +/- 10.9 km2
s-1. In the quiet-Sun region, local correlation tracking
velocity measurements show the dispersal of artificial tracers to be
non-Gaussian over most of our data set with indications of an asymptotic
approach to a 285 km2 s-1 Gaussian diffusion.
Title: Helioseismic Studies of Differential Rotation in the Solar
Envelope by the Solar Oscillations Investigation Using the Michelson
Doppler Imager
Authors: Schou, J.; Antia, H. M.; Basu, S.; Bogart, R. S.; Bush,
R. I.; Chitre, S. M.; Christensen-Dalsgaard, J.; Di Mauro, M. P.;
Dziembowski, W. A.; Eff-Darwich, A.; Gough, D. O.; Haber, D. A.;
Hoeksema, J. T.; Howe, R.; Korzennik, S. G.; Kosovichev, A. G.;
Larsen, R. M.; Pijpers, F. P.; Scherrer, P. H.; Sekii, T.; Tarbell,
T. D.; Title, A. M.; Thompson, M. J.; Toomre, J.
Bibcode: 1998ApJ...505..390S
Altcode:
The splitting of the frequencies of the global resonant acoustic modes
of the Sun by large-scale flows and rotation permits study of the
variation of angular velocity Ω with both radius and latitude within
the turbulent convection zone and the deeper radiative interior. The
nearly uninterrupted Doppler imaging observations, provided by the
Solar Oscillations Investigation (SOI) using the Michelson Doppler
Imager (MDI) on the Solar and Heliospheric Observatory (SOHO) spacecraft
positioned at the L1 Lagrangian point in continuous sunlight,
yield oscillation power spectra with very high signal-to-noise ratios
that allow frequency splittings to be determined with exceptional
accuracy. This paper reports on joint helioseismic analyses of
solar rotation in the convection zone and in the outer part of the
radiative core. Inversions have been obtained for a medium-l mode set
(involving modes of angular degree l extending to about 250) obtained
from the first 144 day interval of SOI-MDI observations in 1996. Drawing
inferences about the solar internal rotation from the splitting data
is a subtle process. By applying more than one inversion technique
to the data, we get some indication of what are the more robust
and less robust features of our inversion solutions. Here we have
used seven different inversion methods. To test the reliability and
sensitivity of these methods, we have performed a set of controlled
experiments utilizing artificial data. This gives us some confidence
in the inferences we can draw from the real solar data. The inversions
of SOI-MDI data have confirmed that the decrease of Ω with latitude
seen at the surface extends with little radial variation through much
of the convection zone, at the base of which is an adjustment layer,
called the tachocline, leading to nearly uniform rotation deeper
in the radiative interior. A prominent rotational shearing layer in
which Ω increases just below the surface is discernible at low to
mid latitudes. Using the new data, we have also been able to study the
solar rotation closer to the poles than has been achieved in previous
investigations. The data have revealed that the angular velocity
is distinctly lower at high latitudes than the values previously
extrapolated from measurements at lower latitudes based on surface
Doppler observations and helioseismology. Furthermore, we have found
some evidence near latitudes of 75° of a submerged polar jet which
is rotating more rapidly than its immediate surroundings. Superposed
on the relatively smooth latitudinal variation in Ω are alternating
zonal bands of slightly faster and slower rotation, each extending
some 10° to 15° in latitude. These relatively weak banded flows
have been followed by inversion to a depth of about 5% of the solar
radius and appear to coincide with the evolving pattern of ``torsional
oscillations'' reported from earlier surface Doppler studies.
Title: Large-scale coronal heating by the small-scale magnetic field
of the Sun
Authors: Schrijver, C. J.; Title, A. M.; Harvey, K. L.; Sheeley,
N. R.; Wang, Y. -M.; van den Oord, G. H. J.; Shine, R. A.; Tarbell,
T. D.; Hurlburt, N. E.
Bibcode: 1998Natur.394..152S
Altcode:
Magnetic fields play a crucial role in heating the outer atmospheres
of the Sun and Sun-like stars, but the mechanisms by which magnetic
energy in the photosphere is converted to thermal energy in the corona
remain unclear. Observations show that magnetic fields emerge onto
the solar surface as bipolar regions with a broad range of length
scales. On large scales, the bipolar regions survive for months before
dispersing diffusively. On the smaller scales, individual bipolar
regions disappear within days but are continuously replenished by new
small flux concentrations, resulting in a sustained state of mixed
polarity. Here we determine the rate of emergence of these small
bipolar regions and we argue that the frequent magnetic reconnections
associated with these regions (an unavoidable consequence of continued
flux replacement) will heat the solar atmosphere. The model that
describes the details of these mixed-polarity regions is complementary
to the traditional diffusion model for large-scale flux dispersal and
a combination of the two should lead to a more complete understanding
of the role of magnetic fields in stellar atmospheres.
Title: First Results from the TRACE Mission
Authors: Title, A.; Tarbell, T.; Schrijver, C.; Wolfson, J.; Shine,
R.; Hurlburt, N.; Golub, L.; Deluca, E.; Bookbinder, J.; Handy, B.;
Acton, L.; Harrison, R.; Delaboudinere, J. -P.
Bibcode: 1998AAS...192.1507T
Altcode: 1998BAAS...30..841T
The TRACE spacecraft was launched on 1 April and all systems are
functioning as designed. The initial outgassing period will conclude
on 20 April and the science program will then begin. TRACE is a UV-EUV
imager with one arc second spatial resolution and is capable of taking
images with a cadence as high as two seconds. We will present images
and image sequences. We hope to present initial comparisons of magnetic
evolution and transition region and coronal brightenings.
Title: Preparation of a Dual Wavelength Sequence of High-Resolution
Solar Photospheric Images Using Phase Diversity
Authors: Löfdahl, Mats G.; E. Berger, Thomas; Shine, Richard S.;
Title, Alan M.
Bibcode: 1998ApJ...495..965L
Altcode:
The collection, seeing compensation, and temporal filtering of
a high-resolution time-sequence of solar photospheric images is
described. A 70 minute time series of cospatial and cotemporal G
band 4305 Å and wideband 4686 Å filtergrams was obtained with
the 50 cm Swedish Vacuum Solar Telescope on the island of La Palma,
Spain. The 29" × 70" field-of-view near disk center contains both
an enhanced network region and an (apparently) nonmagnetic ``quiet''
region of granulation. The mean time between frames is 23.5 s. Each
frame is created with partitioned phase-diverse speckle restoration of
three realizations of the atmospheric turbulence acquired rapidly in
sequence. The result is high-resolution movies of the solar photosphere,
good enough to allow detection, tracking, and analysis of ~0.2" bright
points. This analysis is the subject of a companion paper.
Title: Measurements of Solar Magnetic Element Motion from
High-Resolution Filtergrams
Authors: Berger, Thomas E.; Löfdahl, Mats G.; Shine, Richard S.;
Title, Alan M.
Bibcode: 1998ApJ...495..973B
Altcode:
Solar photospheric flowfield properties on sub-0.5" scales are
measured using local correlation tracking (LCT) and object tracking of
magnetic bright points (MBPs: photospheric bright points associated
with magnetic elements). The dataset is a 70 minute time series
of cospatial and cotemporal G-band 4305 Å and wideband 4686 Å
filtergrams obtained with the 50 cm Swedish Vacuum Solar Telescope on
the island of La Palma, Spain. We examine a 29" × 70" field of view
(FOV) near disk center and compare a 29" × 29" magnetic network
subfield and a 27" × 27" apparently nonmagnetic ``quiet-Sun''
subfield. The mean time between frames is 23.75 s. Each frame is
created by partitioned phase-diverse speckle restoration of three
image pairs acquired rapidly in sequence. Angular resolution is ~0.4"
or less in all frames of the restored data set. From LCT on a 0.4"
grid with 0.83" FWHM apodization, we find the flow speeds to be Rayleigh
distributed with a mode of 550 m s-1 and an average of 950
m s-1 in the network FOV; in the quiet FOV the modal speed
is 700 m s-1 with a mean of 1100 m s-1. Within
the network FOV, a ``magnetic region'' defined by the loci of tracked
MBPs exhibit even greater alteration: rms contrast of the region is
8% higher in the G band compared to areas outside, LCT speeds are
reduced by a factor of 1.6, and the convective flow structures are
smaller and much more chaotic. Mesogranulation is entirely absent in
the magnetic region. The modal and mean speeds of 534 tracked MBPs
are 300 m s-1 and 1470 m s-1, respectively. MBPs
split and merge with mean times of 320 and 404 s respectively. The mean
lifetime of MBPs in the data set is 9.33 minutes although approximately
5% of the objects can be tracked for the entire 70 minute duration of
the time series.
Title: Helio-Atmospheric Links Explorer (HALE): A MIDEX Experiment
for Exploring the Emergence of Magnetic Flux from Below the Solar
Photosphere through the Corona
Authors: Scherrer, P. H.; Title, A. M.; Bush, R. I.; Duvall, T. L.,
Jr.; Gurman, J. B.; Kosovichev, J. T.; Hoeksema, A. G.; Poland, A. I.;
Tarbell, T. D.
Bibcode: 1998ESASP.417..285S
Altcode: 1998cesh.conf..285S
No abstract at ADS
Title: The Stellar and Planetary Explorer (SPEX) Mission
Authors: Schou, J.; Scherrer, P. H.; Brown, T. M.; Frandsen, S.;
Horner, S. D.; Korzennik, S. G.; Noyes, R. W.; Tarbell, T. D.; Title,
A. M.; Walker, A. B. C., II; Weiss, W. W.; Bogart, R. S.; Bush, R. I.;
Christensen-Dalsgaard, J.; Hoeksema, J. T.; Jones, A.; Kjeldsen, H.
Bibcode: 1998ESASP.418..401S
Altcode: 1998soho....6..401S
The Stellar and Planetary Explorer (SPEX) is a mission designed
to search for terrestrial sized planets around sun-like stars using
precise photometry. The planets will be detected by searching for the
decrease in brightness associated with transits of the planets in front
of their parent stars. One of the secondary scientific objective of
SPEX is to do asteroseismology on a number of sun-like stars. SPEX
is designed as a secondary payload on a commercial communications
satellite and will have a design life time of three years. We will
provide an overview of the SPEX scientific objectives and design,
with particular emphasis on the prospects for doing asteroseismology.
Title: The Sun's Magnetic Carpet
Authors: Title, A. M.; Schrijver, C. J.
Bibcode: 1998ASPC..154..345T
Altcode: 1998csss...10..345T
Recent observations by the Michelson Doppler Imager on the Solar and
Heliospheric Observatory show that the magnetic field in the quiet
sun is replaced in about 40 hours. Flux emergence is accompanied by an
equivalent disappearance that results in a mean field in the quiet Sun
of about 2 Gauss. The kinetic balance of emergence, fragmentation,
merging, and cancellation is responsible for the magnetic network
observed in the quiet Sun. The constantly changing mixed polarity
fields in the network are potential sources for the energy release
necessary for heating the corona.
Title: A Possible Mechanism for the Origin of Emerging Flux in the
Sunspot Moat
Authors: Ryutova, M.; Shine, R.; Title, A.; Sakai, J. I.
Bibcode: 1998ApJ...492..402R
Altcode:
Mass and energy flow near sunspots are associated with the emergence
of magnetic flux, which then moves outward in the sunspot moat. We
present results of analytical and numerical studies of the interaction
of horizontal magnetic flux and plasma flows in three-dimensional
geometry. We show that nonlinear coupling of flux and plasma flows in
the presence of a gravitational field lead to nonlinear dissipative
instabilities that result in the formation of a solitary kink along
the magnetic flux. The stability of a kink and its further evolution
depend on the physical parameters of magnetic flux and the surrounding
medium. We discuss two major cases--magnetic soliton-like and shocklike
propagation along the magnetic flux--and specify the appropriate
physical conditions for their realization. In photospheric conditions,
the proposed mechanism may be a good candidate for understanding of
the dynamics of small-scale magnetic flux in the enhanced network at
the solar surface. We apply our results to the observed properties
of emerging flux in the sunspot region associated with moving magnetic
features and find reasonable qualitative and quantitative agreement.
Title: Rotation and Zonal Flows in the Solar Envelope from the
SOHO/MDI Observations
Authors: Scherrer, P. H.; Schou, J.; Bogart, R. S.; Bush, R. I.;
Hoeksema, J. T.; Kosovichev, A. G.; Antia, H. M.; Chitre, S. M.;
Christensen-Dalsgaard, J.; Larsen, R. M.; Pijpers, F. P.; Eff-Darwich,
A.; Korzennik, S. G.; Gough, D. O.; Sekii, T.; Howe, R.; Tarbell,
T.; Title, A. M.; Thompson, M. J.; Toomre, J.
Bibcode: 1997AAS...191.7310S
Altcode: 1997BAAS...29.1322S
We report on the latest inferences concerning solar differential
rotation that have been drawn from the helioseismic data that are now
available from the Solar Oscillations Investigation (SOI) using the
Michelson Doppler Imager (MDI) on the Solar and Heliospheric Observatory
(SOHO). That spacecraft is positioned in a halo orbit near the Sun-Earth
Lagrangian point L_1, in order to obtain continuous Doppler-imaged
observations of the sun with high spatial fidelity. Doppler velocity,
intensity and magnetic field images are recorded, based on modulations
of the 676.8 nm Ni I solar absorption line. The high spatial resolution
of MDI thereby permits the study of many millions of global resonant
modes of solar oscillation. Determination and subsequent inversion
of the frequencies of these modes, including the degeneracy-splitting
by the rotation of the sun, enables us to infer how the sun's angular
velocity varies throughout much of the interior. The current MDI data
are providing substantial refinements to the helioseismic deductions
that can be made about differential rotation both within the convection
zone and in its transition to the radiative interior. The shearing
layer evident in the angular velocity Omega just below the solar
surface is becoming better defined, as is the adjustment layer or
tachocline near the base of the convection zone. The MDI data are also
revealing a prominent decrease in Omega at high latitudes from the
rotation rate expressed by a simple three-term expansion in latitude
that was originally deduced from surface Doppler measurements. Further,
there are indications that a submerged polar vortex involving somewhat
faster Omega than its surroundings exists at about 75(deg) in latitudes.
Title: Photospheric flows as measured by SOI/MDI
Authors: Hurlburt, N.; Frank, Z.; Shine, R.; Tarbell, T.; Title, A.;
Simon, G.
Bibcode: 1997ASSL..225..285H
Altcode: 1997scor.proc..285H
On 2 February and 7 March 1996, MDI on the SOHO spacecraft ran several
hours to provide high resolution continuum images to map the horizontal
flows near the equator and pole by correlation tracking. Here we present
preliminary results on the performance of the tracking technique
in measuring the differential rotation profile. These preliminary
results are compared with each other and with corresponding results
of previous studies.
Title: Modeling the distribution of magnetic fluxes in field
concentrations in a solar active region
Authors: Schrijver, Carolus J.; Title, Alan M.; Hagenaar, Hermance J.;
Shine, Richard A.
Bibcode: 1997SoPh..175..329S
Altcode:
Much of the magnetic field in solar and stellar photospheres is
arranged into clusters of `flux tubes', i.e., clustered into compact
areas in which the intrinsic field strength is approximately a
kilogauss. The flux concentrations are constantly evolving as they
merge with or annihilate against other concentrations, or fragment
into smaller concentrations. These processes result in the formation
of concentrations containing widely different fluxes. Schrijver et
al. (1997, Paper I) developed a statistical model for this distribution
of fluxes, and tested it on data for the quiet Sun. In this paper we
apply that model to a magnetic plage with an average absolute flux
density that is 25 times higher than that of the quiet network studied
in Paper I. The model result matches the observed distribution for the
plage region quite accurately. The model parameter that determines the
functional form of the distribution is the ratio of the fragmentation
and collision parameters. We conclude that this ratio is the same in the
magnetic plage and in quiet network. We discuss the implications of this
for (near-)surface convection, and the applicability of the model to
stars other than the Sun and as input to the study of coronal heating.
Title: Sustaining the Quiet Photospheric Network: The Balance of
Flux Emergence, Fragmentation, Merging, and Cancellation
Authors: Schrijver, Carolus J.; Title, Alan M.; van Ballegooijen,
Adriaan A.; Hagenaar, Hermance J.; Shine, Richard A.
Bibcode: 1997ApJ...487..424S
Altcode:
The magnetic field in the solar photosphere evolves as flux
concentrations fragment in response to sheared flows, merge when they
collide with others of equal polarity, or (partially) cancel against
concentrations of opposite polarity. Newly emerging flux replaces the
canceled flux. We present a quantitative statistical model that is
consistent with the histogram of fluxes contained in concentrations
of magnetic flux in the quiet network for fluxes exceeding ~2 ×
1018 Mx, as well as with estimated collision frequencies
and fragmentation rates. This model holds for any region with weak
gradients in the magnetic flux density at scales of more than a few
supergranules. We discuss the role of this dynamic flux balance (i)
in the dispersal of flux in the photosphere, (ii) in sustaining the
network-like pattern and mixed-polarity character of the network, (iii)
in the formation of unipolar areas covering the polar caps, and (iv) on
the potential formation of large numbers of very small concentrations
by incomplete cancellation. Based on the model, we estimate that as
much flux is cancelled as is present in quiet-network elements with
fluxes exceeding ~2 × 1018 Mx in 1.5 to 3 days, which is
compatible with earlier observational estimates. This timescale is
close to the timescale for flux replacement by emergence in ephemeral
regions, so that this appears to be the most important source of flux
for the quiet-Sun network; based on the model, we cannot put significant
constraints on the amount of flux that is injected on scales that are
substantially smaller than that of the ephemeral regions. We establish
that ephemeral regions originate in the convection zone and are not
merely the result of the reemergence of previously cancelled network
flux. We also point out that the quiet, mixed-polarity network is
generated locally and that only any relatively small polarity excess
is the result of flux dispersal from active regions.
Title: Properties of the Smallest Solar Magnetic
Elements. II. Observations versus Hot Wall Models of Faculae
Authors: Topka, K. P.; Tarbell, T. D.; Title, A. M.
Bibcode: 1997ApJ...484..479T
Altcode:
Observations obtained at the Swedish Solar Observatory, La Palma,
using the Lockheed tunable filter, have been used to measure
properties of active region faculae, including contrast from disk
center to near the limb. The data consist of coregistered digital
photometric images of the line-of-sight magnetic field and of the
continuum intensity. The results are related to the structure
of the individual flux tubes comprising faculae in active regions. In
addition to center-limb contrast, the observations reveal a change in
contrast between heliocentric angles of about 45° and 60° related
to the ``turn-on'' of bright faculae. A class of models has been
constructed that describes a facula as an evacuated thin flux tube
with a hot wall and a depressed cool floor (hot wall model). The
hot wall model is very successful in predicting the observations,
including the changes observed between 45° and 60°. The model
predicts that the larger flux tubes comprising active region plage are
micropores with a Wilson depression of 100 km largely independent of
micropore diameter. Their typical diameter is 350-650 km; the largest
ones are about 1200 km across. Bright points are the major component of
active region plages by number, but micropores probably are the major
component by total magnetic flux. Bright active region faculae seen
near the limb are simply micropores viewed from the side, where the hot
wall is visible and the depressed cool floor is not. The temperature
difference between cool floor and hot wall varies from 300 to nearly
500 K, depending on tube diameter and heliocentric angle. These
results have important implications for solar irradiance variations.
Title: The Solar-B Mission
Authors: Antiochos, Spiro; Acton, Loren; Canfield, Richard; Davila,
Joseph; Davis, John; Dere, Kenneth; Doschek, George; Golub, Leon;
Harvey, John; Hathaway, David; Hudson, Hugh; Moore, Ronald; Lites,
Bruce; Rust, David; Strong, Keith; Title, Alan
Bibcode: 1997STIN...9721329A
Altcode:
Solar-B, the next ISAS mission (with major NASA participation), is
designed to address the fundamental question of how magnetic fields
interact with plasma to produce solar variability. The mission has
a number of unique capabilities that will enable it to answer the
outstanding questions of solar magnetism. First, by escaping atmospheric
seeing, it will deliver continuous observations of the solar surface
with unprecedented spatial resolution. Second, Solar-B will deliver the
first accurate measurements of all three components of the photospheric
magnetic field. Solar-B will measure both the magnetic energy driving
the photosphere and simultaneously its effects in the corona. Solar-B
offers unique programmatic opportunities to NASA. It will continue an
effective collaboration with our most reliable international partner. It
will deliver images and data that will have strong public outreach
potential. Finally, the science of Solar-B is clearly related to the
themes of origins and plasma astrophysics, and contributes directly
to the national space weather and global change programs.
Title: On the Dynamics of Magnetic Flux Concentrations in Quiet
Photospheric Network.
Authors: Sakai, J. I.; Ryutova, M.; Schrijver, K.; Shine, R.; Tarbell,
T.; Berger, T.; Title, A.; Hagenaar, H.
Bibcode: 1997SPD....28.0260S
Altcode: 1997BAAS...29..904S
Magnetic flux concentrations in the quiet photospheric network show
a complex dynamics which includes merging of colliding fluxes, the
"total" or partial cancellation of neighboring fluxes, fragmentation
and others. We propose a mechanism to explain the observed phenomena
based on the idea that magnetic flux concentrations in the photospheric
network are essentially non-collinear. We show that non-collinearity
of colliding fluxes leads to the whole new class of effects which are
observed; for example, the apparent cancellation of opposite polarity
fluxes turns into the formation of horizontal magnetic fluxes (which
later may appear as a new weaker bipoles) and is accompanied by the
shock formation and mini-flares. In the case of shock formation
the reconnection area becomes a source of the acoustic emission;
mini-flares may be seen as bright points. The energetics of these
processes strongly depends on geometry of "collision" and physical
parameters of colliding fluxes. For example, if colliding fluxes have
comparable and "small" cross sections, the reconnection results in
complete reorganization of their magnetic fields; if merging fluxes
are large enough or considerably different, magnetic flux may be
only partially reconnected and partially survived. Reconnection of
non-collinear equal polarity fluxes leads to the "scattering" processes
which include the fragmentation into several smaller fluxes if initially
colliding concentrations carried different amount of magnetic flux. We
give the example of numerical simulation for the case of merging and
fragmentation process occurring during the collision of collinear
"strong" and "weak" magnetic flux concentrations. The calculation
results shown to be consistent with observational data from both
the SOHO/MDI instrument and the Swedish Vacuum Solar Telescope on
La Palma. This research is supported by NASA contract NAG5-3077 at
Stanford University and the MDI contract PR 9162 at Lockheed.
Title: Phase-Diversity Restoration of two Simultaneous 70-minute
Photospheric Sequences.
Authors: Lofdahl, M. G.; Berger, T. E.; Shine, R. A.; Title, A. M.
Bibcode: 1997SPD....28.0218L
Altcode: 1997BAAS...29..896L
Seeing effects have been corrected in two cospatial and cotemporal
70-minute sequences of images collected in the G-band 4305 Angstroms and
wideband 4686 Angstroms. The data were obtained with the 50 cm Swedish
Vacuum Solar Telescope on the island of La Palma, Spain. The 29arcsecx
70arcsec field-of-view (FOV) near disk center contains both an enhanced
network region and an (apparently) non-magnetic ``quiet'' region of
granulation. The mean time between restored frames is 23.5 s. Each of
the 180 images is created with Phase-Diverse Speckle (PDS) imaging,
using two different focus positions sampled at the best three snapshots
of the atmospheric turbulence (seeing) during a 20-second selection
window. Wavefronts are estimated for each focused--defocused image
pair and a restored frame is produced from all six images. The average
resolution in the restored sequence is about 0farcs4 (corresponding to
spatial frequencies up to half the diffraction limit of the telescope),
which is good enough to allow detection of ~ 0farcs2 bright points. The
data is used for statistical measurements of magnetic element speed,
interaction frequency, and lifetime (see accompanying poster by
T. E. Berger et al). We show destretched and space-time filtered
movies of both the G-band and continuum images, as well as raw data
to demonstrate the effect of the restoration process. This work was
supported by NASA contracts NAS5-30386 at Stanford and NAS8-39747 and
Independent Research Funds at Lockheed-Martin. MGL was supported by
the Swedish Science Research Council.
Title: Comparison of Granulation Correlation Tracking (CT) and
Feature Tracking (FT) Results from SOHO/MDI and the Swedish Vacuum
Solar Telescope on La Palma
Authors: Shine, R.; Strous, L.; Simon, G.; Berger, T.; Hurlburt, N.;
Tarbell, T.; Title, A.; Scharmer, G.
Bibcode: 1997SPD....28.0262S
Altcode: 1997BAAS...29Q.904S
We have computed photospheric velocity flow maps from simultaneous
observations taken with MDI and at the Swedish Vacuum Solar Tower
(SVST) on La Palma on August 15, 1996. Both sets consist of a series
of photospheric images, and flow maps are computed by following the
local motions of granules. The MDI data have the important advantages
of very stable images and longer continuous coverage of the same area
of the solar surface. This longer coverage is necessary to study the
evolution of mesogranules, supergranules, and to detect possible low
amplitude motions on scales larger than supergranules. However, the
high resolution mode of MDI is limited by the small telescope size to
about 1.2 arc seconds angular resolution and uses a 0.6 arc second pixel
size. This is adequate to show granulation but has the rms constrast
significantly reduced to about 2%. Early efforts adapting techniques
that were successful with higher resolution ground based images gave
poor results and although new methods have now been developed, there
are still some problems with accuracy. On the other hand, the SVST
images have much higher angular resolution (as good as 0.2 arc second)
but suffer from variable atmospheric distortion. They also have a much
smaller field of view. By detailed comparison of the two data sets
and by using CT and FT techniques to track the motions, we hope to
understand the sources of any differences between them and to develop
credible correction parameters to the MDI data sets if necessary. This
work was supported by NASA Grant NAG5-3077 at Stanford and Lockheed
Martin, by AFOSR and the Fellows Program of AF Phillips Lab at NSO/SP,
and by the Swedish Royal Academy of Sciences.
Title: The Distribution of Cell Sizes of the Solar Chromospheric
Network
Authors: Hagenaar, Hermance J.; Schrijver, Carolus J.; Title, Alan M.
Bibcode: 1997ApJ...481..988H
Altcode:
This paper studies the cellular pattern of the supergranular network. We
present an algorithm to draw a surface-filling cell pattern on an
uninterrupted two-day sequence of Ca II K filtergrams with a 1 nm
bandpass. The 60° × 40° field of view contains both quiet and
enhanced network and plages. The algorithm uses a threshold-independent
method of steepest descent on spatially smoothed and time-averaged
images. We determine the distribution function of cell areas and
find a broad, asymmetric spectrum of areas. The distribution is
found to be invariant for different spatial smoothings if the cell
areas are normalized to a unit mean. It is this invariance that
leads us to believe we have determined the intrinsic distribution of
cell areas. Extrapolation of the average cell size to zero spatial
smoothing yields a characteristic cell diameter of L = 13-18 Mm. This
is roughly half the generally quoted supergranular length scale L ~
32 Mm as determined with autocorrelation methods. The difference
in characteristic cell size reflects the application of a different
measurement method: the autocorrelation method as used by Simon &
Leighton and others is preferentially weighted towards relatively
large cells. We find no significant dependence of cell size on local
magnetic flux density.
Title: Preliminary SoHO/MDI Observations of Supergranular Evolution
Authors: Simon, G. W.; Strous, L. H.; Matt, S.; Title, A. M.;
Schrijver, C. J.
Bibcode: 1997SPD....28.0264S
Altcode: 1997BAAS...29R.904S
We present preliminary results of a study into the evolution of
supergranules, using data from SoHO/MDI. We discuss the supergranular
size spectrum, lifetimes, and topological evolution. We compare
structures of supergranular size visible in high-resolution SoHO/MDI
dopplergrams and in divergence maps derived from tracking of features
in dopplergrams. This work was supported by NASA Grant NAG5-3077 at
Stanford and Lockheed Martin, and by AFOSR and the Fellows Program of
AF Phillips Lab at NSO/SP.
Title: Solar Irradiance Variations due to the Quiet Sun Network
Authors: Topka, K. P.; Tarbell, T. D.; Title, A. M.
Bibcode: 1997SPD....28.0263T
Altcode: 1997BAAS...29..904T
An estimate for the change in total solar irradiance due to quiet sun
network during the 11-year solar cycle is presented. The estimate is
based on measurements of the center-limb contrast function for quiet
sun magnetic elements. These measurements are the result of analysis
of near-simultaneous, co-registered, digital, photometric images of
the photospheric intensity (4300 - 6300 A) and line-of-sight magnetic
field. Images were made with the Lockheed tunable filter instrument at
the Swedish Solar Observatory, La Palma, between 1991 and 1994. The
result is of order 0.1%. The images cover only a tiny fraction of
the surface of the Sun and thus a very large extrapolation is made,
limiting the accuracy of the result. Measurements made by satellite
radiometers indicate that on the time scale of solar activity, the total
solar irradiance is greater at activity maximum than at minimum by about
0.1 to 0.15 %. Our result is consistent with this. Earlier results on
active region plage, using similar data from La Palma, indicate that it
does does not contribute significantly to long-term solar irradiance
variations. This work has been supported by NSF contract ATM-9320353,
by NASA contracts NASW-4612 and NAS8-39747, and by Lockheed IR funds.
Title: A search for interaction between magnetic fields and
supergranular flows in the network based on MDI observations
Authors: Schrijver, C. J.; Shine, R. A.; Title, A. M.; Hagenaar,
H. J.; Hurlburt, N. E.; Tarbell, T. D.; Simon, G. W.
Bibcode: 1997SPD....28.0243S
Altcode: 1997BAAS...29..901S
We study the supergranular flow field and its temporal evolution in
the quiet Sun as observed with the Michelson Doppler Imager on board
SOHO. We use the intensity images to derive the flow fields using
local correlation tracking. The data sets span one to two days with a
one--minute cadence. We separate areas with a relatively high filling
factor for magnetic concentrations from areas with a low magnetic
filling factor in order to study to what extent the flows influence
the magnetic network in the quiet Sun and vice versa. This work is
supported by NASA Grant NAG5-3077 at Stanford and Lockheed Martin,
and by AFOSR and the Fellows Program of AF Phillips Lab at NSO/SP
Title: Continuous Observations of Solar Magnetic Fields from SOI/MDI
on SOHO
Authors: Hoeksema, J. T.; Bush, R. I.; Scherrer, P. H.; Heck, C.;
Hurlburt, N.; Shine, R.; Tarbell, T.; Title, A.
Bibcode: 1997SPD....28.0127H
Altcode: 1997BAAS...29..884H
The Solar Oscillations Investigation's Michelson Doppler Imager
instrument (SOI/MDI) on SOHO measures the photospheric magnetic field
over the whole disk nearly every 96 minutes with 4" resolution and a
noise level of a few Gauss. Beginning in April 1996, this unprecedented
continuous series of frequent, uniform quality magnetograms provides
a striking view of the continual emergence, motion, evolution, and
interaction of magnetic flux everywhere on the visible solar surface
near solar minimum. These evolving photospheric fields ultimately
drive the variations of the corona and solar wind that affect the
terrestrial environment. Knowledge of the rapidly evolving photospheric
field provides a crucial input for forecasting conditions in the
corona, heliosphere, and geospace. A few magnetograms are available
each day within hours of observation through the SOHO web site at
http://sohowww.nascom.nasa.gov/. These may be used for planning and
forecasting, e.g. to compute models of the solar corona. The remainder
are generally available within a few weeks. Sometimes more focused
campaigns provide magnetic observations as often as once each minute
for up to 8 hours. Campaigns can be run with either the full disk
resolution or with 0.6" pixels in a limited field near the center of
the disk. The SOI project welcomes collaborations. More information
can be found at http://soi.stanford.edu/.
Title: Measurements of Magnetic Element Dynamics in the Network
Authors: Berger, T. E.; Lofdahl, M. G.; Shine, R. A.; Title, A. M.
Bibcode: 1997SPD....28.0219B
Altcode: 1997BAAS...29..896B
Statistical measurements of magnetic element speed, interaction
frequency, and lifetime in an enhanced network region at disk center
are presented. The primary dataset is a 70 min time series of G-band
4305 Angstroms filtergrams taken at the 50 cm Swedish Vacuum Solar
Telescope (SVST) on the island of La Palma, Spain. A second time
series of 4686 Angstroms wide-band continuum filtergrams, cospatial
and simultaneous to within several milliseconds with the G-band
images, is also studied. The field-of-view is near Sun center and
includes a region of enhanced network activity with many G-band bright
points. Both time series are corrected for seeing to very near the
telescope diffraction limit by the technique of Phase Diverse Speckle
(PDS) restoration (see accompanying poster by M. G. Lofdahl et al). We
show destretched and space-time filtered movies of both the G-band and
continuum images in two fields-of-view: a region of quiet granulation
and the region of enhanced network activity. Within the network, local
correlation tracking measurements on a 0\farcs4 grid show the RMS
speed to be 778 m s(-1) ; outside the network the RMS speed is 1168 m
s(-1) . Corkflow simulations show that normal convective flow patterns
(granulation and mesogranulation) are absent in the network. Magnetic
elements move with modal and mean speeds of 100 m s(-1) and 815 m s(-1)
, respectively. The mean interaction frequency (time between either
merging or splitting) is 220 s. The mean lifetime of tracked magnetic
elements in the network is 9.33 min although 5% of the elements are
tracked for the entire 70 min of the times series. This work was
supported by NASA contracts NAS5-30386 at Stanford and NAS8-39747 and
Independent Research Funds at Lockheed-Martin. MGL was supported by
the Swedish Science Research Council.
Title: Dispersal of magnetic flux in the quiet network as observed
on a day-long magnetogram sequences observed with MDI on SOHO
Authors: Hagenaar, H. J.; Schrijver, C. J.; Shine, R. A.; Title, A. M.
Bibcode: 1997SPD....28.0244H
Altcode: 1997BAAS...29..901H
We study the dynamic behavior of magnetic flux elements in the quiet
solar network using high--resolution magnetograms observed with the
Michelson Doppler Imager on board SOHO. We track concentrations of
magnetic flux in uninterrupted time sequences spanning 20 to 45 hours
in order to study the dispersal of magnetic elements in the turbulent
photospheric flows. We measure the displacements and derive average
speeds as a function of time. The displacements are compared to a
random walk model. This work is supported by NASA Grant NAG5-3077 at
Stanford and Lockheed.
Title: The TRACE Mission
Authors: Wolfson, J.; Bruner, M.; Jurcevich, B.; Lemen, J.; Schrijver,
K.; Shine, R.; Strong, K.; Tarbell, T.; Title, A.; Golub, L.;
Bookbinder, J.; Deluca, E.; Acton, L.; Handy, B.; Kankelborg, C.;
Fisher, R.
Bibcode: 1997SPD....28.0143W
Altcode: 1997BAAS...29..887W
The TRACE (Transition Region and Coronal Explorer) mission will explore
the connections between fine-scale magnetic fields and plasma structures
in the coronal, transition zone and temperature minimum regions of the
sun. TRACE will collect images of solar plasmas at temperatures from
10(4) to 10(7) K, with one arc second spatial resolution and excellent
temporal resolution and continuity. With a scheduled launch date of 15
December 1997, the mission will emphasize collaborative observations
with SoHO, enabling simultaneous observations of high-resolution images,
spectra, and magnetograms. The 30 cm aperture TRACE telescope uses four
normal-incidence coatings for the EUV and UV on quadrants of the primary
and secondary mirrors. Interference filters further isolate 5 different
UV bands. The images are co-aligned and internally stabilized against
spacecraft jitter. A 1024 x 1024 lumigen-coated CCD detector collects
images over an 8.5 x 8.5 arc minute field-of-view. LMATC, SAO, and GSFC
built the TRACE instrument, which was integrated with the GSFC-produced
SMEX spacecraft on 28 February (just over two years from the start
of its development). It will be put into a Sun-synchronous orbit and
operated in coordination with the SoHO Experiment Operations Facility at
GSFC. We are committed to maintaining a publicly accessible data base
for TRACE data. Browsing and data set requesting capabilities will be
provided at Web site www.space.lockheed.com/TRACE/TRACElinks.html. This
site already contains a large volume of information on the mission
including preliminary scientific observing programs and directions
as to how to participate in the mission now and in the future. This
project is supported by NASA contract NAS5-38099.
Title: Performance of the Michelson Doppler Imager Instrument on SOHO
Authors: Scherrer, P.; Bogart, R.; Bush, R.; Duvall, T.; Hoeksema,
J. T.; Kosovichev, A.; Schou, J.; Morrison, M.; Tarbell, T.; Title, A.
Bibcode: 1997SPD....28.0207S
Altcode: 1997BAAS...29..894S
Launched on SOHO in December 1995, the MDI instrument took its 10
millionth filtergram in early April, 1997. The instrument and spacecraft
have performed admirably since commissioning, providing over a year
of virtually uninterrupted time series of velocity and intensity
measurements at moderate resolution, a continuous 60-day time series
of full disk 4" velocity and line depth maps, monthly 72+ hour time
series in various observables, a host of daily 8-hour campaigns, and
full-disk magnetograms every 96 minutes. Another uninterrupted 90-day
interval of nearly full data recovery is scheduled to be completed in
mid July. Various scientific results using MDI data are being presented
at this meeting. About a dozen terabytes of data sets have been created
and archived and normal pipeline processing is now completed soon after
retrieving the data, typically less than a month after the observations
are made. Most of the data products are generally available on the WWW,
see http://soi.stanford.edu. Selected data are available in near real
time. The SOI team welcomes collaborations. Routine and extraordinary
calibrations along with analysis of scientific data sets allow us to
make good estimates of the noise and understand many of the sources
of systematic errors in the instrument. In almost every respect the
instrument performs as well or better than expected before launch,
the primary limitations being photon noise on the short term and
fixed or slowly varying offsets on the long term. We have found that
the Michelsons are somewhat more sensitive to operational temperature
variations than was expected, adding some additional constraints on
our observing sequences.
Title: The dynamic nature of the supergranular network
Authors: Title, A. M.; Schrijver, C. J.; van Ballegooijen, A. A.;
Hagenaar, H. J.; Shine, R. A.
Bibcode: 1997SPD....28.0242T
Altcode: 1997BAAS...29..900T
The magnetic field in the quiet solar photosphere evolves as flux
concentrations fragment in response to sheared flows, merge when they
collide with others of equal polarity, or (partially) cancel against
concentrations of opposite polarity. Newly emerging flux, mostly in
ephemeral regions, replaces the canceled flux in a matter of a few
days. We present a quantitative statistical model to describe the
resulting histogram of fluxes contained in concentrations of magnetic
flux in the quiet network. We discuss this dynamic flux balance with
respect to (i) the potential dispersal of flux in the photosphere
as a function of ephemeral-region properties, (ii) sustaining the
network--like pattern and mixed--polarity character of the network,
and (iii) the formation of unipolar areas covering the polar caps. We
establish that ephemeral regions are not the result of the re-emergence
of previously cancelled network flux. Moreover, their emergence cannot
be correlated to the emergence of active regions but must instead
be relatively homogeneous. We also point out that the bulk of the
quiet, mixed-polarity network is generated locally, and that only any
relatively small polarity excess is the result of flux dispersal from
active regions.
Title: Structure and Rotation of the Solar Interior: Initial Results
from the MDI Medium-L Program
Authors: Kosovichev, A. G.; Schou, J.; Scherrer, P. H.; Bogart, R. S.;
Bush, R. I.; Hoeksema, J. T.; Aloise, J.; Bacon, L.; Burnette, A.; de
Forest, C.; Giles, P. M.; Leibrand, K.; Nigam, R.; Rubin, M.; Scott,
K.; Williams, S. D.; Basu, Sarbani; Christensen-Dalsgaard, J.; Dappen,
W.; Rhodes, E. J., Jr.; Duvall, T. L., Jr.; Howe, R.; Thompson, M. J.;
Gough, D. O.; Sekii, T.; Toomre, J.; Tarbell, T. D.; Title, A. M.;
Mathur, D.; Morrison, M.; Saba, J. L. R.; Wolfson, C. J.; Zayer, I.;
Milford, P. N.
Bibcode: 1997SoPh..170...43K
Altcode:
The medium-l program of the Michelson Doppler Imager instrument on board
SOHO provides continuous observations of oscillation modes of angular
degree, l, from 0 to ∽ 300. The data for the program are partly
processed on board because only about 3% of MDI observations can be
transmitted continuously to the ground. The on-board data processing,
the main component of which is Gaussian-weighted binning, has been
optimized to reduce the negative influence of spatial aliasing of the
high-degree oscillation modes. The data processing is completed in a
data analysis pipeline at the SOI Stanford Support Center to determine
the mean multiplet frequencies and splitting coefficients. The initial
results show that the noise in the medium-l oscillation power spectrum
is substantially lower than in ground-based measurements. This enables
us to detect lower amplitude modes and, thus, to extend the range of
measured mode frequencies. This is important for inferring the Sun's
internal structure and rotation. The MDI observations also reveal the
asymmetry of oscillation spectral lines. The line asymmetries agree
with the theory of mode excitation by acoustic sources localized in the
upper convective boundary layer. The sound-speed profile inferred from
the mean frequencies gives evidence for a sharp variation at the edge
of the energy-generating core. The results also confirm the previous
finding by the GONG (Gough et al., 1996) that, in a thin layer just
beneath the convection zone, helium appears to be less abundant than
predicted by theory. Inverting the multiplet frequency splittings from
MDI, we detect significant rotational shear in this thin layer. This
layer is likely to be the place where the solar dynamo operates. In
order to understand how the Sun works, it is extremely important to
observe the evolution of this transition layer throughout the 11-year
activity cycle.
Title: On the Patterns of the Solar Granulation and Supergranulation
Authors: Schrijver, Carolus J.; Hagenaar, Hermance J.; Title, Alan M.
Bibcode: 1997ApJ...475..328S
Altcode:
We study the cellular patterns of the white light granulation and of the
chromospheric Ca II K supergranular network. We apply a gradient-based
tessellation algorithm to define the cell outlines. The geometry of
the patterns formed by the associated granular and supergranular
flows are very similar, in spite of the substantial difference in
length scale. We compare these patterns to generalized Voronoi foams
and conclude that both convective patterns are very nearly compatible
with an essentially random distribution of upflow centers, with the
downflow boundaries determined by the competing strengths of outflows
of neighboring upwellings. There appears to be a slight clustering
in upflow positions for the granulation, consistent with the granular
evolution. This slight preference for large granules to be surrounded
by somewhat smaller ones makes the granular and supergranular patterns
differ enough to allow a correct identification in three out of four
cases by eye. The model analogy suggests that the range in outflow
strengths is remarkably small. The patterns appear to be rather
insensitive to the details of the competing forces that establish the
pattern of the downflow network: similar patterns result under very
different conditions, so that little can be learned about the details
of the forces involved by studying the geometry of these patterns only.
Title: On the dynamics of magnetic flux concentrations in quiet
photospheric network.
Authors: Sakai, J. I.; Ryutova, M.; Schrijver, K.; Shine, R. A.;
Tarbell, T. D.; Berger, T. E.; Title, A. M.; Hagenaar, H. J.
Bibcode: 1997BAAS...29T.904S
Altcode:
No abstract at ADS
Title: Internal structure and rotation of the Sun: First results
from MDI data
Authors: Kosovichev, A. G.; Schou, J.; Scherrer, P. H.; Bogart, R. S.;
Bush, R. I.; Hoeksema, J. T.; Aloise, J.; Bacon, L.; Burnette, A.;
De Forest, C.; Giles, P. M.; Leibrand, K.; Nigam, R.; Rubin, M.;
Scott, K.; Williams, S. D.; Basu, Sarbani; Christensen-Dalsgaard,
J.; Däppen, W.; Rhodes, E. J., Jr.; Duvall, T. L., Jr.; Howe, R.;
Thompson, M. J.; Gough, D. O.; Sekii, T.; Toomre, J.; Tarbell, T. D.;
Title, A. M.; Mathur, D.; Morrison, M.; Saba, J. L. R.; Wolfson,
C. J.; Zayer, I.; Milford, P. N.
Bibcode: 1997IAUS..181..203K
Altcode:
No abstract at ADS
Title: Time-Distance Helioseismology with the MDI Instrument:
Initial Results
Authors: Duvall, T. L., Jr.; Kosovichev, A. G.; Scherrer, P. H.;
Bogart, R. S.; Bush, R. I.; de Forest, C.; Hoeksema, J. T.; Schou,
J.; Saba, J. L. R.; Tarbell, T. D.; Title, A. M.; Wolfson, C. J.;
Milford, P. N.
Bibcode: 1997SoPh..170...63D
Altcode:
In time-distance helioseismology, the travel time of acoustic waves
is measured between various points on the solar surface. To some
approximation, the waves can be considered to follow ray paths that
depend only on a mean solar model, with the curvature of the ray
paths being caused by the increasing sound speed with depth below the
surface. The travel time is affected by various inhomogeneities along
the ray path, including flows, temperature inhomogeneities, and magnetic
fields. By measuring a large number of times between different locations
and using an inversion method, it is possible to construct 3-dimensional
maps of the subsurface inhomogeneities. The SOI/MDI experiment on SOHO
has several unique capabilities for time-distance helioseismology. The
great stability of the images observed without benefit of an intervening
atmosphere is quite striking. It has made it possible for us to detect
the travel time for separations of points as small as 2.4 Mm in the
high-resolution mode of MDI (0.6 arc sec pixel-1). This has
enabled the detection of the supergranulation flow. Coupled with the
inversion technique, we can now study the 3-dimensional evolution of
the flows near the solar surface.
Title: An integrated space physics instrument (ISPI) for Solar Probe
Authors: Tsurutani, B. T.; Leschly, K.; Nikzad, S.; Fossum, E. R.;
Title, A. M.; Chenette, D. L.; Mann, I.; Murphy, G.; Musmann, G.;
Gliem, F.; Tuzzolino, A. J.; Killeen, T. L.; Kennedy, B. C.; Moses,
S. L.
Bibcode: 1997AIPC..387..131T
Altcode: 1997sta..conf..131T
Instruments for the Solar Probe mission must be designed not only to
address the unique scientific measurement requirements, but must be
compatible with the modest resource dollars as well as tight constraints
on mass and power. Another unique aspect of the Solar Probe mission
is its constraint on telemetry and the fact that the prime science is
conducted in a single flyby. The instrument system must be optimized
to take advantage of the telemetry and observing time available. JPL,
together with industry and university partners, is designing
an Integrated Space Physics Instrument (ISPI) which will measure
magnetic fields, plasma waves, thermal plasma, energetic particles,
dust, and perform EUV/visible and coronal imaging for the Solar Probe
mission. ISPI uses a new architecture and incorporates technology
which not only eliminates unnecessary duplication of function, but
allows sensors to share data and optimize science. The current ISPI
design goal (for a flight package) is a 5 kilogram/10 watt payload.
Title: High-resolution spectral imaging of the Sun in the far
ultraviolet
Authors: Bruner, Marilyn E.; Tarbell, Theodore D.; Title, Alan M.;
Wuelser, J. -P.; Handy, Brian N.; Zukic, Muamer
Bibcode: 1996SPIE.2804..249B
Altcode:
The Transition Region and Coronal Explorer instrument (TRACE) will
use narrow-band interference filters together with other appropriate
band limiting elements to make high resolution images of the Sun in
the C IV lines at 154.8 and 155.0 nm. Filter observations of solar
C IV emission are complicated by the presence of UV Continuum and
nearby chromospheric lines because of the relatively wide bandpasses
of the narrowest currently available interference filters. TRACE will
use a series of filters to estimate the effects of the UV continuum
and the long-wavelength `leaks' in the blocking filters which we
show are the most important contaminants in the C IV images. Further
improvements in filtergraph performance may be realized through the use
of tunable Fabry-Perot etalons, which have been under development at
Lockheed-Martin. We present test data from a cultured quartz etalon
designed for 155 nm, and will discuss the prospects for etalons
operation at substantially shorter wavelengths.
Title: Dynamics of the Chromospheric Network: Mobility, Dispersal,
and Diffusion Coefficients
Authors: Schrijver, Carolus J.; Shine, Richard A.; Hagenaar, Hermance
J.; Hurlburt, Neal E.; Title, Alan M.; Strous, Louis H.; Jefferies,
Stuart M.; Jones, Andrew R.; Harvey, John W.; Duvall, Thomas L., Jr.
Bibcode: 1996ApJ...468..921S
Altcode:
Understanding the physics behind the dispersal of photo spheric magnetic
flux is crucial to studies of magnetoconvection, dynamos, and stellar
atmospheric activity. The rate of flux dispersal is often quantified by
a diffusion coefficient, D. Published values of D differ by more than a
factor of 2, which is more than the uncertainties allow. We propose that
the discrepancies between the published values for D are the result of
a correlation between the mobility and flux content of concentrations of
magnetic flux. This conclusion is based on measurements of displacement
velocities of Ca II K mottles using an uninterrupted 2 day sequence
of filtergrams obtained at the South Pole near cycle minimum. We
transform the Ca II K intensity to an equivalent magnetic flux density
through a power-law relationship defined by a comparison with a nearly
simultaneously observed magnetogram. One result is that, wherever the
network is clearly defined in the filtergrams, the displacement vectors
of the mottles are preferentially aligned with the network, suggesting
that network-aligned motions are more important to field dispersal than
deformation of the network pattern by cell evolution. The rms value
of the inferred velocities, R = <|v|2>½,
decreases with increasing flux, Φ, contained in the mottles, from R
≍ 240 m s-1 down to 140 s-1. The value of R(Φ)
appears to be independent of the flux surrounding the concentration,
to the extreme that it does not matter whether the concentration is
in a plage or in the network. The determination of a proper effective
diffusion coefficient requires that the function R(Φ) be weighted
by the number density n(Φ) of mottles that contain a total flux. We
find that n(Φ) decreases exponentially with Φ and propose a model
of continual random splitting and merging of concentrations of flux to
explain this dependence. Traditional methods used to measure D tend to
be biased toward the larger, more sluggish flux concentrations. Such
methods neglect or underestimate the significant effects of the
relatively large number of the more mobile, smaller concentrations. We
argue that the effective diffusion coefficient for the dispersal of
photo spheric magnetic flux is ∼600 km2 s-1.
Title: Double-Gaussian Models of Bright Points or Why Bright Points
Are Usually Dark
Authors: Title, A. M.; Berger, T. E.
Bibcode: 1996ApJ...463..797T
Altcode:
We have modeled the structure of small bright features, "bright points"
seen in an outstanding CH filter (0-band) image. In our model, bright
points consist of a Gaussian bright core centered in a Gaussian dark
surround. The basis for this approach is the observation that nearly
all of the bright points in the image exist within intergranular lanes,
vertices between granules, or local brightness depressions. Using
reasonable estimates for the size and depth of vertices and lanes, the
model predicts that bright points clearly detectable in images with
0".2 resolution will seldom be detectable in images with resolutions
beyond 0".4. This occurs because the transfer function of the telescope
and atmosphere averages the bright points with their comparably sized
dark surroundings to near zero contrast when blurred beyond 0".4. These
results explain the great rarity of images that clearly show bright
points. Furthermore, the image shows many bright points with core
diameters equal to that of the FWHM of a point-spread function of a
perfect telescope. If the intensity profiles of these bright points
were Gaussian on a flat background, then their intrinsic brightness
would have to be unrealistically high and they would not disappear
on images blurred beyond 0".4, but would simply gradually expand in
size and drop in contrast as the blur increased. Because the bright
points are sites of magnetic fields, our model helps to explain lower
resolution disk center observations that show magnetic fields occur in
regions that are dark relative to the mean continuum level. The modeling
also suggests that bright points with diameters of 0".1 or less would
be undetectable in the current generation of 0.5 m high-resolution
solar telescopes, under any seeing conditions.
Title: Solar Lite
Authors: Title, A.
Bibcode: 1996AAS...188.6702T
Altcode: 1996BAAS...28..933T
The prime goal of Solar Lite is to investigate the small- scale
structure and the variability of the magnetic field in the solar
atmosphere. Magnetic flux emerges from the interior and organizes itself
on scales that are too small to be observed effectively and consistently
through the turbulent atmosphere of the Earth, but that can be resolved
by the 1-meter Solar Lite telescope operating in space. The measurements
afforded by Solar Lite will provide solar physics with results needed
to address several long-standing fundamental problems. These include
the origin of small-scale filamentation of the magnetic field; the
dynamics of sunspots; the cause for the variation in solar luminosity
during the activity cycle; the mechanisms for heating the outer solar
atmosphere; the magnetic field and electric current configurations
responsible for solar flares; the evolution of the flux distribution
as a constraint to the solar dynamo. The main instrument is a 1-meter
optical Gregory telescope, with silicon carbide lightweight mirrors. The
telescope is under construction now at the Vavilov Optical Institute,
supported by a NASA SR&T contract. The angular resolution is 0.1
arcseconds, corresponding to 75 km on the Sun. Possible focal plane
instruments are a filter magnetograph and a spectro-polarimeter. We
will also discuss possible co-observing telescopes than can extend the
scientific value of a mission. Possible instrument accommodations on a
free-flying dedicated small satellite and on shuttle launched platforms
(Astro-SPAS or Spartan 400) will be shown.
Title: An Analytical Model for Fluted Sunspots and a New
Interpretation of Evershed Flow and X-Ray Anemones
Authors: Martens, Petrus C. H.; Hurlburt, Neal E.; Title, Alan M.;
Acton, Loren W.
Bibcode: 1996ApJ...463..372M
Altcode:
We present a force-free constant-α model for the magnetic field in and
above so-called "fluted" sunspots. This model is motivated by recent
high-resolution observations of Title et al. at the Swedish Solar
Observatory in La Palma. They observed that the inclination angle of
the magnetic field in the penumbra of sunspots oscillates rapidly
with azimuth, with a period of about 60 and an amplitude of about
18°. They further find that there is little variation in the radial
direction and in absolute field strength. The resulting phenomenon
of interlocking high- and low-inclination field lines was called
"flutedness. In our model, the parameters are chosen to reproduce
the La Palma magnetograms, and an analytical expression is obtained for
the three-dimensional magnetic field emanating from the sunspot's umbra
and penumbra. The model correctly reproduces the azimuthal variation in
inclination angle, as well as the mean constancy of the magnetic field
strength, and the appearance of a highly corrugated neutral line on
the limb side of off-center sunspots. We find that the "flutedness"
results in a highly complex topology in a boundary layer extending
from the photo sphere into the chromosphere, while the coronal field is
uniform. Title et al. demonstrated that the Evershed flow occurs
in regions of nearly horizontal magnetic field, and tacitly assumed,
as is done in most of the literature, that the dark filaments in which
the flow is observed form individual magnetic flux tubes. Our magnetic
field solution suggests that the regions of nearly horizontal field
at the photo spheric boundary may not form individual magnetic flux
tubes, but rather a series of short horizontal loops bridging a neutral
line that is stretched in the radial direction along the penumbra,
up to the outer penumbral boundary. Hence, the Evershed flow could not
be a simple siphon flow in the radial direction, but would consist of
phase-coordinated flows along the many short loops bridging the neutral
line. However, the assumption of a force-free field breaks down in
this region of the atmosphere, and the topology suggested by it may
not materialize in reality. We further demonstrate that there
are large variations in the photospheric cross sections of coronal
loops, due to the complexity of the field near their photospheric
footpoints. Under the assumption of constant energy input per unit
surface area into these loops, the variation in cross section is
qualitatively consistent with the variation in X-ray brightness of
loops in penumbral "anemones" observed by Yohkoh.
Title: TRACE: the Transition Region and Coronal Explorer
Authors: Schrijver, C.; Title, A.; Acton, L.; Bruner, M.; Fischer,
R.; Golub, L.; Harrison, R.; Lemen, J.; Rosner, R.; Scharmer, G.;
Scherrer, P.; Strong, K.; Tarbell, T.; Wolfson, J.
Bibcode: 1996AAS...188.6704S
Altcode: 1996BAAS...28..934S
The TRACE mission is designed to obtain images of the solar
transition region and corona of unprecedented quality. With these
images we will be able to explore quantitatively the connections
between the photospheric magnetic field and the associated hot and
tenuous structures in the outer atmosphere. The TRACE telescope has
an aperture of 30 cm, and will observe an 8.5 x 8.5 arcminute field of
view with a resolution of one arcsecond. Finely tuned coatings on four
quadrants on the primary and secondary normal--incidence mirrors will
allow observations in narrow EUV and UV spectral bands. The passbands
are set to Fe IX, XII, and XV lines in the EUV band, while filters
allow observations in C IV, Ly alpha , and the UV continuum using
the UV mirror quadrant. The data thus cover temperatures from 10(4)
K up to 10(7) K. The Sun--synchronous orbit allows long intervals of
uninterrupted viewing. Observations at different wavelengths can be
made in rapid succession with an alignment of 0.1 arcsec. Coordinated
observing with TRACE, SoHO and YOHKOH will give us the first opportunity
to observe all temperature regimes in the solar atmosphere, including
magnetograms, simultaneously from space. TRACE is currently scheduled
to be launched in October 1997. More information can be found on the
web at ``http://pore1.space.lockheed.com/TRACE/welcome.html''.
Title: What is the size scale of the solar supergranular network?
Authors: Hagenaar, H.; Schrijver, C.; Title, A.
Bibcode: 1996AAS...188.0201H
Altcode: 1996BAAS...28..820H
We developed an algorithm to outline the chromospheric network on a
2-day sequence of Ca II K observations made from the South Pole, in
order to study the sizes of supergranulation cells. We find an average
cell diameter that is substantially smaller than the generally quoted
value of 30--35 Mm, as first determined by Simon and Leighton (1964)
from autocorrelation curves of the line--of--sight velocities. We
argue that the autocorrelation method is preferentially weighted
towards large cells, which results in an estimated size that is
approximately 1.5 to 2 times larger than the true average cell
diameter. A comparable difference should occur in studies of the size
scale of the chromospheric network. In addition, we find that secondary
maxima to the autocorrelation peaks of the Doppler signal imply that
the correlation between cell size and flow velocity is weak at best. If
such a correlation should exist, it would be too weak to affect the
spacing of the secondary maxima of the autocorrelation function.
Title: On the Dynamics of Small-Scale Solar Magnetic Elements
Authors: Berger, T. E.; Title, A. M.
Bibcode: 1996ApJ...463..365B
Altcode:
We report on the dynamics of the small-scale solar magnetic field, based
on analysis of very high resolution images of the solar photosphere
obtained at the Swedish Vacuum Solar Telescope. The data sets are
movies from 1 to 4 hr in length, taken in several wavelength bands
with a typical time between frames of 20 5. The primary method of
tracking small-scale magnetic elements is with very high contrast
images of photospheric bright points, taken through a 12 Å bandpass
filter centered at 4305 Å in the Fraunhofer "G band." Previous studies
have established that such bright points are unambiguously associated
with sites of small-scale magnetic flux in the photosphere, although
the details of the mechanism responsible for the brightening of the
flux elements remain uncertain. The G band bright points move in the
intergranular lanes at speeds from 0.5 to 5 km s-1. The
motions appear to be constrained to the intergranular lanes and are
primarily driven by the evolution of the local granular convection flow
field. Continual fragmentation and merging of flux is the fundamental
evolutionary mode of small-scale magnetic structures in the solar
photosphere. Rotation and folding of chains or groups of bright points
are also observed. The timescale for magnetic flux evolution in active
region plage is on the order of the correlation time of granulation
(typically 6-8 minutes), but significant morphological changes can occur
on timescales as short as 100 5. Smaller fragments are occasionally
seen to fade beyond observable contrast. The concept of a stable,
isolated subarcsecond magnetic "flux tube" in the solar photosphere
is inconsistent with the observations presented here.
Title: A Possible Mechanism for the Origin Emerging Flux in the
Sunspot Moat
Authors: Sakai, Jun-Ichi; Shine, R.; Title, A.; Ryutova, M.
Bibcode: 1996AAS...188.3502S
Altcode: 1996BAAS...28R.871S
Mass and energy flow near sunspots is associated with the emergence
of magnetic flux which then moves outward in the sunspot moat. We
present results of analytical and numerical studies of the interaction
of horizontal magnetic flux and plasma flows in 3D-geometry. We show
that nonlinear coupling of flux and plasma flows in the presence of
a gravitational field lead to nonlinear dissipative instabilities
which result in the formation of a solitary kink along the magnetic
flux. The stability of a kink and its further evolution depends on the
physical parameters of magnetic flux and surrounding medium. We discuss
two major cases, magnetic soliton- and shock-like propagation along
the magnetic flux, and specify the appropriate physical conditions for
their realization. For example, under conditions in a sunspot moat, when
the mass flow velocity exceeds about 0.5 v_A there occurs a magnetic
soliton-like kink, propagating with a velocity less than the external
mass flow velocity. The larger the radius of a flux tube, the larger the
``width'' of a soliton, and the lower the velocity of its propagation;
the width of a soliton corresponds to the separation of ``legs'' of a
kink which appear as magnetic field of the opposite polarities - the
nearest to sunspot has obviously the same polarity. When the external
mass flow velocity is less than about 0.5 v_A, a magnetic shock-like
perturbation can propagate with a velocity larger than the external
mass flow velocity. We apply these results to the observed properties
of emerging flux and find reasonable qualitative and quantitative
agreement. This research was supported by NASA contract NAG5-3077 at
Stanford University (M.R.) and NASA contract NAS8-39747 at
Title: Initial Results from SOI/MDI High Resolution Magnetograms
Authors: Title, A.; Tarbell, T.; Frank, Z.; Schrijver, C.; Shine,
R.; Wolfson, J.; Zayer, I.; Scherrer, P.; Bush, R.; Deforest, C.;
Hoeksema, T.
Bibcode: 1996AAS...188.6915T
Altcode: 1996BAAS...28..938T
The Michelson Doppler Imager (MDI) on SoHO takes magnetogram
s with resolutions of 1.2 (high resolution) and 4 (full disk)
arcseconds. Movies of 16 hour duration have been constructed in full
disk and high resolution mode. High resolution movies of the south
polar region also have been obtained. In sums of nine high resolution
magnetograms it is possible to detect fields as low as 5 gauss and
total fluxes as low as 5 10(1) 6 Mx. In mid latitude regions new flux
is observed to emerge everywhere. At all latitudes below 60 degrees
flux is mixed on the scale of supergranulation. In the polar region
above 60 degrees only fields of a single polarity are observed above
the detection limit.
Title: The Global Oscillation Network Group (GONG) Project
Authors: Harvey, J. W.; Hill, F.; Hubbard, R. P.; Kennedy, J. R.;
Leibacher, J. W.; Pintar, J. A.; Gilman, P. A.; Noyes, R. W.; Title,
A. M.; Toomre, J.; Ulrich, R. K.; Bhatnagar, A.; Kennewell, J. A.;
Marquette, W.; Patron, J.; Saa, O.; Yasukawa, E.
Bibcode: 1996Sci...272.1284H
Altcode:
Helioseismology requires nearly continuous observations of the
oscillations of the solar surface for long periods of time in
order to obtain precise measurements of the sun's normal modes of
oscillation. The GONG project acquires velocity images from a network
of six identical instruments distributed around the world. The GONG
network began full operation in October 1995. It has achieved a duty
cycle of 89 percent and reduced the magnitude of spectral artifacts by
a factor of 280 in power, compared with single-site observations. The
instrumental noise is less than the observed solar background.
Title: Preliminary SOI/MDI Observations of Surface Flows by
Correlation Tracking in the Quiet Solar Photosphere and an Emerging
Active Region
Authors: Tarbell, T.; Frank, Z.; Hurlburt, N.; Saba, J.; Schrijver,
C.; Shine, R.; Title, A.; Simon, G.; Strous, L.
Bibcode: 1996AAS...188.6914T
Altcode: 1996BAAS...28..937T
The extended observation of the solar surface with frequent sampling
provided by MDI on SoHO offers the chance to observe the evolution of
supergranules and to measure surface flows associated with active
regions and perhaps larger scale zonal and meridonal flows. We
have used local correlation tracking of the granulation pattern for
measuring surface flows from MDI high resolution continuum images. The
datasets consist of 1024 x 1024 pixel images collected with a cadence
of one minute and extending many hours each. The images are typically
centered upon the central meridian of the sun and offset to the north
of sun center, spanning roughly 40 degrees of solar longitude and from
approximately -10 to +30 degrees of solar latitude. The latitude
dependence of the differential rotation is evident. We present
preliminary results of our search for signatures of mesogranules,
supergranules and giant cells. On 23 Feb. 1996, we obtained a 12-hour
continuous sequence including quiet sun near disk center and NOAA
region 7946 at about N08 E30. The active region grew rapidly over this
interval, forming several sunpots. We show preliminary comparisons of
the measured flow fields with coaligned SOI/MDI magnetograms taken
at 15-minute intervals. The SOI/MDI program is supported by NASA
grant NAG5-3077.
Title: SOI/MDI Measurements of Horizontal Flows in the South Polar
Region of the Sun by Correlation Tracking and Doppler Shifts
Authors: Simon, G.; Frank, Z.; Hurlburt, N.; Schrijver, C.; Shine,
R.; Tarbell, T.; Title, A.; Deforest, C.
Bibcode: 1996AAS...188.6913S
Altcode: 1996BAAS...28R.937S
On 7 March 1996, the SOHO spacecraft was offset from its usual
disk center pointing for an 11-hour observation of the South
Polar region. MDI took a continuous time series of high resolution
longitudinal magnetograms during this period, in support of the
SOHO-wide Joint Observing Program on polar plumes. It also ran several
hours each of two other programs: one to map the horizontal flows near
the pole by correlation tracking and Doppler shifts, and another to
study wave propagation (e.g., by time-distance helioseismology) at
these high latitudes. In this poster we present preliminary results
from the first program. Both techniques yield measurements of the
differential rotation profile near the pole and of horizontal flows of
supergranulation. These results are compared with each other and with
corresponding measurements in low latitudes. The location of magnetic
features in the horizontal flows is also shown. The SOI/MDI program
is supported by NASA grant NAG5-3077.
Title: Photospheric Surface Flows and Small Magnetic Structures in
Sunspot Moats
Authors: Shine, R. A.; Title, A.; Frank, Zoe; Scharmer, G.
Bibcode: 1996AAS...188.3501S
Altcode: 1996BAAS...28Q.871S
We have computed horizontal flow maps of the photosphere around
and within three different sunspots using high spatial resolution
continuum movies obtained at the Swedish Vacuum Solar Telescope on
La Palma on June 5, 1993, August 29, 1993, and July 14, 1994. Two
of the data sets also included magnetograms and dopplergrams. A new
feature found in the flow maps is azimuthal structure in the moat
flows surrounding sunspots. Instead of a simple radial flow, there
are zones of azimuthal divergence and convergence resulting in radial
``spokes'' of convergence. These are not uniformly distinct around the
entire circumference but are seen in part of the surrounding area for
all 3 sunspots. The angular spacing is about 10 to 20 degrees and the
pattern persists for several hours. For one of the sunspots, we have
concurrent movies made with a 3 Angstrom wide K line filter. A time
average of these images shows bright spokes in the K line congruent with
the convergence spokes. Much of the magnetic flux that is continually
emerging and moving outward in the moat is in the vicinity of the
``spokes.'' In addition, these data show several good examples of
so called ``streakers.'' These are small bright structures seen in
continuum movies that appear to be emitted from the outer edge of the
penumbral and travel a few thousand km at about 2 to 3 km/s before
fading. We find that these are associated with a magnetic field of
opposite polarity to the sunspot and that they travel toward another
larger and slower moving magnetic feature with the same polarity as
the sunspot. When the streaker catches up, it disappears, sometimes
coincident with a brightening of the merged feature which continues
outward at the previous velocity, about 0.5 km/s. This work was
supported by NSF grant ATM-9213879, NASA contracts NAS8-39746 and
NAS8-39747, Lockheed Independent Research Funds, and the Swedish Royal
Academy of Sciences.
Title: Calibration and Performance of the Michelson Doppler Imager
on SOHO.
Authors: Zayer, I.; Morrison, M.; Tarbell, T. D.; Title, A.; Wolfson,
C. J.; MDI Engineering Team; Bogart, R. S.; Bush, R. I.; Hoeksema,
J. T.; Duvall, T.; Sa, L. A. D.; Scherrer, P. H.; Schou, J.
Bibcode: 1996AAS...188.3712Z
Altcode: 1996BAAS...28..879Z
The Michelson Doppler Imager (MDI) instrument probes the interior
of the Sun by measuring the photospheric manifestations of solar
oscillations. MDI was launched in December, 1995, on the Solar and
Heliospheric Observatory (SOHO) and has been successfully observing the
Sun since then. The instrument images the Sun on a 1024 x 1024 pixel CCD
camera through a series of increasingly narrow spectral filters. The
final elements, a pair of tunable Michelson interferometers, enable
MDI to record filtergrams with FWHM bandwidth of 94 m Angstroms with
a resolution of 4 arcseconds over the whole disk. Images can also be
collected in MDI's higher resolution (1.25 arcsecond) field centered
about 160 arcseconds north of the equator. An extensive calibration
program has verified the end-to-end performance of the instrument
in flight. MDI is working very well; we present the most important
calibration results and a sample of early science observations. The
Image Stabilization System (ISS) maintains overall pointing to
better than ca. 0.01 arcsec, while the ISS' diagnostic mode allows
us to measure spectrally narrow pointing jitter down to less than
1 mili-arcsec. We have confirmed the linearity of each CCD pixel to
lie within 0.5%\ (the FWHM of the distribution is 0.2% ), and have to
date not detected any contamination on the detector, which is cooled
to -72 C. The noise in a single Dopplergram is of the order of 20 m/s,
and initial measurements of transverse velocities are reliable to 100
m/s. The sensitivity of magnetograms reach 5G in a 10 minute average
(15G in a single magnetogram). MDI's primary observable, the p-modes
from full-disk medium-l data, are of very high quality out to l=300
as seen in the initial l-nu diagram. The SOI-MDI program is supported
by NASA contract NAG5-3077.
Title: Phenomena in an emerging active region. I. Horizontal dynamics.
Authors: Strous, L. H.; Scharmer, G.; Tarbell, T. D.; Title, A. M.;
Zwaan, C.
Bibcode: 1996A&A...306..947S
Altcode:
Horizontal dynamics in observations of NOAA AR 5617 are studied by
tracking individual elements through the field of view. Small magnetic
elements of both magnetic polarities occur everywhere in the active
region, and define unipolar thread-like concentrations of magnetic
field of up to 15Mm length. The horizontal granular flow field in
the active region is divergent (e-time scale 2.1hours) and clockwise
(time scale 32hours). Facular elements are tracers of (clumps of)
fluxtubes. A hierarchy of movement of magnetic elements appears:
Facular elements everywhere in the active region move obliquely toward
the edges of the active region of the same polarity as their own, faster
than those edges (as defined by strings of pores) move apart. The pores
move along the edges toward the major sunspots of their own polarity,
and the major sunspots of either polarity move apart. The separation
velocity of both polarities of facular elements is about 0.84km/s, of
pores about 0.73km/s, and that of the major sunspots is about 0.50km/s.
Title: Interaction of magnetic fields and convective flows in the
solar atmosphere
Authors: Title, A.
Bibcode: 1996ASPC..109...79T
Altcode: 1996csss....9...79T
No abstract at ADS
Title: SPLIT: a large spectro-polarimetric space instrument for
solar observations.
Authors: Schmidt, W.; Kentischer, T.; Title, A. M.; Lites, B. W.
Bibcode: 1996AGAb...12...88S
Altcode:
No abstract at ADS
Title: Heating of Active Region Corona by Transient Brightenings
(Microflares)
Authors: Shimizu, T.; Tsuneta, T.; Title, A.; Tarbell, T.; Shine,
R.; Frank, Z.
Bibcode: 1996mpsa.conf...37S
Altcode: 1996IAUCo.153...37S
No abstract at ADS
Title: The Solar Oscillations Investigation - Michelson Doppler Imager
Authors: Scherrer, P. H.; Bogart, R. S.; Bush, R. I.; Hoeksema, J. T.;
Kosovichev, A. G.; Schou, J.; Rosenberg, W.; Springer, L.; Tarbell,
T. D.; Title, A.; Wolfson, C. J.; Zayer, I.; MDI Engineering Team
Bibcode: 1995SoPh..162..129S
Altcode:
The Solar Oscillations Investigation (SOI) uses the Michelson Doppler
Imager (MDI) instrument to probe the interior of the Sun by measuring
the photospheric manifestations of solar oscillations. Characteristics
of the modes reveal the static and dynamic properties of the
convection zone and core. Knowledge of these properties will improve
our understanding of the solar cycle and of stellar evolution. Other
photospheric observations will contribute to our knowledge of the
solar magnetic field and surface motions. The investigation consists
of coordinated efforts by several teams pursuing specific scientific
objectives.
Title: The TRACE Mission
Authors: Title, A.; Bruner, M.; Jurcevich, B.; Lemen, J.; Strong,
K.; Tarbell, T.; Wolfson, J.; Golub, L.; Fisher, R.
Bibcode: 1995AAS...18710107T
Altcode: 1995BAAS...27.1427T
We have seen significant progress in the flight preparation of the
TRACE (Transition Region and Coronal Explorer) instrument during
the last few months. TRACE, approved for 1997 launch, will collect
images of solar plasmas at temperatures from 10(4) to 10(7) K, with
one arc second spatial resolution and excellent temporal resolution
and continuity. TRACE will explore the connections between fine-scale
magnetic fields and plasma structures in the coronal, transition
zone and temperature minimum regions of the sun. The 1997 launch
opportunity allows for collaborative observations from Earth orbit
with the SoHO instruments stationed at L1. Simultaneous observations
including high-resolution images, spectra, and magnetograms are
possible. The 30 cm aperture TRACE telescope uses four normal-incidence
coatings for the EUV and UV on quadrants of the primary and secondary
mirrors. Interference filters further isolate 5 different UV bands. The
images are coaligned and internally stabilized against spacecraft
jitter. A 1024 x 1024 CCD detector collects images over an 8.5 x 8.5
arc minute field-of-view. TRACE is launched on a GSFC SMEX spacecraft
into a Sun-synchronous orbit. It will operate in coordination with
the SoHO Experiment Operations Facility at GSFC. We are committed to
maintaining an publicly accessible data base for TRACE data. Browsing
and data set requesting capabilities will be included at our World
Wide Web site (see http://www.space.lockheed.com/TRACE/welcome.html).
Title: Precise Photometry Mission -- Measuring Stellar
Microvariability from Space
Authors: Brown, T. M.; Borucki, W.; Frandsen, S.; Gilliland, R. L.;
Jones, A.; Noyes, R. W.; Tarbell, T.; Title, A.; Ulrich, R. K.
Bibcode: 1995AAS...187.7111B
Altcode: 1995BAAS...27R1385B
Atmospheric scintillation limits the precision attainable by
ground-based photometry; this limitation is a major obstacle to
progress in several fields, notably asteroseismology of Sun-like
stars. A space-borne photometric telescope could operate near the shot
noise limit, removing this obstacle and providing new opportunities
for inquiry. As part of the program for New Mission Concepts in
Astrophysics, we are studying the scientific rewards and technological
challenges associated with a Precise Photometry Mission (PPM). The
baseline performance goal for the PPM is to measure solar-like
pulsations (amplitude 3 mu mag) in G stars in the Hyades with a S/N
ratio of 4 in 10 days of observing time. This performance would also
allow detection of transits of Earth-sized planets of main-sequence
stars, extremely precise characterization of the light curves of
micro-lensing events, and other novel applications. The technical
approach envisioned for the PPM is wide-band CCD photometry. The study
that is underway focuses on two aspects of the required technology: (1)
Are CCD detectors able to provide the necessary very high S/N within
the spacecraft operating environment? (2) Can new lightweight mirror
and telescope structure technology be applied to yield significant
reductions in mission cost? We are addressing both questions with
laboratory tests, including time-series performance tests of suitable
CCDs, and thermal and mechanical tests of a SiC telescope mirror. In
addition to describing PPM's scientific aims and technical rationale,
we report preliminary results of the CCD tests.
Title: Motion and Evolution of Solar Magnetic Elements
Authors: Berger, T. E.; Schrijver, C. J.; Shine, R. S.; Tarbell,
T. D.; Title, A. M.; Scharmer, G.
Bibcode: 1995AAS...18710104B
Altcode: 1995BAAS...27.1426B
The dynamics of sub-arcsecond solar magnetic flux tubes are analyzed
based on very-high resolution movies of photospheric bright points
obtained in 1994 at the 50-cm Swedish Solar Vacuum Telescope (SVST)
on the island of La Palma, Spain. The bright points are imaged using
a 12 Angstroms bandpass interference filter centered at 4305 Angstroms
in the ``G Band'' molecular bandhead of the CH molecule. The image sets
typically consist of up to 4 hours of consecutive images taken at a 10
to 20 second cadence. Spatial resolution throughout the movies averages
less than 0\arcsec.5 and many frames in the sets exhibit resolution
down to 0\arcsec.25. Magnetic flux elements in the photosphere are
shown to move continually along the intergranular lanes at speeds
of up to 5 km/sec and ranges up to several thousand km. Evolution of
individual magnetic elements is dominated by the local evolution of
surrounding granules. Fragmentation and merging is the fundamental
mode of evolution of the majority of magnetic elements seen in our
data. Rotation and folding of chains or groups of elements is also
frequently observed. The time scale for the fragmentation/merging
evolution of the elements is on the order of the lifetime of granulation
(6--8 minutes), but significant morphological changes are seen to
occur on time scales as short as 100 seconds. The concept of a stable,
isolated, sub-arcsecond magnetic flux element in the solar photosphere
is inconsistent with the observations presented here.
Title: Solar Lite
Authors: Rosenberg, W. J.; Title, A. M.; Tarbell, T. D.
Bibcode: 1995AAS...187.7406R
Altcode: 1995BAAS...27.1390R
Solar Lite is a one meter diameter Gregorian diffraction limited
solar telescope using Silicon Carbide optics that is currently being
fabricated by the Vavilov Optical Institute in St. Petersburg,
Russia. The mirror is made of a two phase ceramic that is 83%
SiC and 17% Si. A 63 cm, f/1.5 test sphere has been fabricated and
polished. The test mirror weighs 12 Kg, the surface error 1/40 wave RMS,
and the surface roughness is 18 angstroms RMS. The telescope structure
is a corrugated aluminum tube (bellows) with Invar stringers. This
approach is possible because Russian material technology is capable
of producing thin Invar sheets with a coefficient of linear expansion
of 3x10(-7) . The primary mirror has a design weight of 30 kg and the
entire telescope has a total weight of 150 kg. A preliminary design
review has been completed. The detailed design of the telescope will be
completed in January 1996. We hope to fly the telescope with a vector
magnetograph in a sun synchronous orbit. The completion date for the
telescope is July 1997.
Title: New Observations of Subarcsecond Photospheric Bright Points
Authors: Berger, T. E.; Schrijver, C. J.; Shine, R. A.; Tarbell,
T. D.; Title, A. M.; Scharmer, G.
Bibcode: 1995ApJ...454..531B
Altcode:
We have used an interference filter centered at 4305 Å within the
bandhead of the CH radical (the "G band") and real-time image selection
at the Swedish Vacuum Solar Telescope on La Palma to produce very
high contrast images of subarcsecond photospheric bright points at all
locations on the solar disk. During the 6 day period of 1993 September
15-20 we observed active region NOAA 7581 from its appearance on the
East limb to a near disk-center position on September 20. A total of
1804 bright points were selected for analysis from the disk center image
using feature extraction image processing techniques. The measured FWHM
distribution of the bright points in the image is subnormal with a modal
value of 220 km (0".30) and an average value of 250 km (0".35). The
smallest measured bright point diameter is 120 km (0".17) and the
largest is 600 km (0".69). Approximately 60% of the measured bright
points are circular (eccentricity ∼1.0), the average eccentricity
is 1.5, and the maximum eccentricity corresponding to filigree in
the image is 6.5. The peak contrast of the measured bright points is
normally distributed. The contrast distribution variance is much greater
than the measurement accuracy, indicating a large spread in intrinsic
bright-point contrast. When referenced to an averaged "quiet-Sun area 1n
the image, the modal contrast is 29% and the maximum value is 75%; when
referenced to an average intergranular lane brightness in the image,
the distribution has a modal value of 61 % and a maximum of 119%. The
bin-averaged contrast of G-band bright points is constant across the
entire measured size range. The measured area of the bright points,
corrected for population and selection effects, covers about 1.8% of
the total image area. Large pores and micropores occupy an additional
2% of the image area, implying a total area fraction of magnetic
proxy features in the image of 3.8%. We discuss the implications of
this area fraction measurement in the context of previously published
measurements which show that typical active region plage has a magnetic
filling factor on the order of 10% or greater. The results suggest that
in the active region analyzed here, less than 50% of the small-scale
magnetic flux tubes are demarcated by visible proxies such as bright
points or pores.
Title: Vorticity and Divergence in the Solar Photosphere
Authors: Wang, Yi; Noyes, Robert W.; Tarbell, Theodore D.; Title,
Alan M.
Bibcode: 1995ApJ...447..419W
Altcode:
We have studied an outstanding sequence of continuum images of the
solar granulation from Pic du Midi Observatory. We have calculated the
horizontal vector flow field using a correlation tracking algorithm,
and from this determined three scalar fields: the vertical component of
the curl, the horizontal divergence, and the horizontal flow speed. The
divergence field has substantially longer coherence time and more power
than does the curl field. Statistically, curl is better correlated
with regions of negative divergence that is, the vertical vorticity is
higher in downflow regions, suggesting excess vorticity in intergranular
lanes. The average value of the divergence is largest (i.e., outflow
is largest) where the horizontal speed is large; we associate these
regions with exploding granules. A numerical simulation of general
convection also shows similar statistical differences between curl
and divergence. Some individual small bright points in the granulation
pattern show large local vorticities.
Title: The Transition Region and Coronal Explorer (trace)
Authors: Title, A.; Bruner, M.; Jurcevich, B.; Lemen, J.; Strong,
K.; Tarbell, T.; Wolfson, J.; Golub, L.; Bookbinder, J.; Fisher, R.
Bibcode: 1995ESASP.376b.505T
Altcode: 1995help.confP.505T; 1995soho....2..505T
No abstract at ADS
Title: Simulated MDI Observations of Convection
Authors: Hurlburt, N. E.; Schrijver, C. J.; Shine, R. A.; Title, A. M.
Bibcode: 1995ESASP.376b.239H
Altcode: 1995soho....2..239H; 1995help.confP.239H
No abstract at ADS
Title: Soi/mdi Studies of Active-Region Seismology and Evolution
Authors: Tarbell, T. D.; Title, A.; Hoeksema, J. T.; Scherrer, P.;
Zweibel, E.
Bibcode: 1995ESASP.376b..99T
Altcode: 1995help.confP..99T; 1995soho....2...99T
The Solar Oscillations Investigation (SOI) will study active regions
in many ways using both helioseismic and conventional observing
techniques. The Michelson Doppler Imager (MDI) instrument can
make Doppler, continuum and line depth images and also longitudinal
magnetograms, showing either the full disk or a high resolution field of
view. There will be a Dynamics Program of continuous full disk Doppler
observations for two months per year, many Campaign Programs of 8 hours
continuous observing per day, and a synoptic Magnetic Program of about
15 full disk magnetograms per day. This paper gives a brief description
of some of the scientific plans, measurements, and observing programs.
Title: Kinematic Models of Supergranular Diffusion on the Sun
Authors: Simon, G. W.; Title, A. M.; Weiss, N. O.
Bibcode: 1995ApJ...442..886S
Altcode:
We develop kinematic models of diffusion generated by supergranulation
at the solar surface. These models use current observations for the
size, horizontal velocity, and lifetime of supergranules. Because there
is no observational description of the appearance and disappearance of
supergranules, we investigate models using several plausible evolution
processes, including the effect of different lifetime distribution
functions for the cells. The results are quite insensitive to the
methods chosen to replace old supergranules, the distribution of cell
lifetimes, and even the cell lifetime itself, for mean lifetimes between
15 to 30 hr. Calculated diffusion coefficients range between 500 and 700
sq km/s, in agreement with the best fit diffusion coefficients used by
Sheeley and his collaborators to model the large-scale distribution
of magnetic fields over the solar surface. However, our models do
not explain the field distribution in plage, and they predict that
virtually all the strong field in quiet Sun exists in relatively
isolated clumps. We suggest possible mechanisms for the creation of
plage and the bright network seen in quiet Sun.
Title: The Transition Region And Coronal Explorer (TRACE)
Authors: Title, A.
Bibcode: 1995SPD....26..606T
Altcode: 1995BAAS...27..962T
No abstract at ADS
Title: Solar Irradiance Variations due to Active Region Faculae
Authors: Topka, K. P.; Tarbell, T. D.; Title, A. M.
Bibcode: 1995SPD....26..512T
Altcode: 1995BAAS...27..959T
No abstract at ADS
Title: Frame Selection Techniques for Solar Movies
Authors: Shine, R. A.; Tarbell, T.; Title, A.; Scharmer, G.; Simon,
G.; Brandt, P.; Berger, T.
Bibcode: 1995SPD....26..506S
Altcode: 1995BAAS...27..957S
No abstract at ADS
Title: Flux Emergence in a Sunspot Moat and Young Active Region
Authors: Title, A. M.; Frank, Z. A.; Shine, R. A.; Tarbell, T. D.;
Simon, G. W.; Brandt, P. N.
Bibcode: 1995SPD....26.1007T
Altcode: 1995BAAS...27..978T
No abstract at ADS
Title: Properties of Sub-Arcsecond Facular Bright Points
Authors: Berger, T.; Schrijver, C.; Shine, R.; Tarbell, T.; Title,
A.; Scharmer, G.
Bibcode: 1995SPD....26..505B
Altcode: 1995BAAS...27..957B
No abstract at ADS
Title: Michelson Doppler Imager (MDI) Performance Characteristics
Authors: Zayer, I.; Morrison, M.; Pope, T.; Rosenberg, W.; Tarbell,
T.; Title, A.; Wolfson, J.; Bogart, R. S.; Hoeksema, J. T.; Milford,
P.; Scherrer, P. H.; Schou, J.
Bibcode: 1995ASPC...76..456Z
Altcode: 1995gong.conf..456Z
No abstract at ADS
Title: Observations of Convection
Authors: Title, A. M.; Hurlburt, N.; Schrijver, C.; Shine, R.;
Tarbell, T.
Bibcode: 1995ESASP.376a.113T
Altcode: 1995heli.conf..113T; 1995soho....1..113T
The primary goal of the Solar Oscillations Investigation is
to understand the interior of the Sun using the techniques of
helioseismology. In addition the Michelson Doppler Imager produces
images of the solar surface with sufficient resolution to measure
surface flows via the technique of local correlation tracking and
magnetograms which allow feature tracking of magnetic fields. It will
be possible to measure the evolution of meso and supergranulation, the
evolution of the meso and supergranulation patterns, and the motion of
magnetic elements in the flow field. With observing periods of 8 hours
one should be able to detect large scale flow fields of 10 m/s second
or less. The magnetograms will provide the data to understand how the
cell patterns evolve as a function of magnetic field configuration.
Title: Status of the Solar Oscillations Investigation - Michelson
Doppler Imager
Authors: Scherrer, P. H.; Bogart, R. S.; Bush, R. I.; Hoeksema,
J. T.; Milford, P.; Schou, J.; Pope, T.; Rosenberg, W.; Springer,
L.; Tarbell, T.; Title, A.; Wolfson, J.; Zayer, I.
Bibcode: 1995ASPC...76..402S
Altcode: 1995gong.conf..402S
No abstract at ADS
Title: The transition region and coronal explorer (TRACE)
Authors: Tarbell, T. D.; Bruner, M.; Jurcevich, B.; Lemen, J.; Strong,
K.; Title, A.; Wolfson, J.
Bibcode: 1994ESASP.373..375T
Altcode: 1994soho....3..375T
No abstract at ADS
Title: On the Relation Between Facular Bright Points and the
Magnetic Field
Authors: Berger, Thomas; Shine, Richard; Tarbell, Theodore; Title,
Alan; Scharmer, Goran
Bibcode: 1994AAS...185.8607B
Altcode: 1994BAAS...26.1465B
Multi-spectral images of magnetic structures in the solar photosphere
are presented. The images were obtained in the summers of 1993 and
1994 at the Swedish Solar Telescope on La Palma using the tunable
birefringent Solar Optical Universal Polarimeter (SOUP filter), a 10
Angstroms wide interference filter tuned to 4304 Angstroms in the band
head of the CH radical (the Fraunhofer G-band), and a 3 Angstroms wide
interference filter centered on the Ca II--K absorption line. Three
large format CCD cameras with shuttered exposures on the order of
10 msec and frame rates of up to 7 frames per second were used to
create time series of both quiet and active region evolution. The
full field--of--view is 60times 80 arcseconds (44times 58 Mm). With
the best seeing, structures as small as 0.22 arcseconds (160 km) in
diameter are clearly resolved. Post--processing of the images results
in rigid coalignment of the image sets to an accuracy comparable to the
spatial resolution. Facular bright points with mean diameters of 0.35
arcseconds (250 km) and elongated filaments with lengths on the order
of arcseconds (10(3) km) are imaged with contrast values of up to 60
% by the G--band filter. Overlay of these images on contemporal Fe I
6302 Angstroms magnetograms and Ca II K images reveals that the bright
points occur, without exception, on sites of magnetic flux through the
photosphere. However, instances of concentrated and diffuse magnetic
flux and Ca II K emission without associated bright points are common,
leading to the conclusion that the presence of magnetic flux is a
necessary but not sufficient condition for the occurence of resolvable
facular bright points. Comparison of the G--band and continuum images
shows a complex relation between structures in the two bandwidths:
bright points exceeding 350 km in extent correspond to distinct
bright structures in the continuum; smaller bright points show no
clear relation to continuum structures. Size and contrast statistical
cross--comparisons compiled from measurements of over two-thousand
bright point structures are presented. Preliminary analysis of the time
evolution of bright points in the G--band reveals that the dominant mode
of bright point evolution is fission of larger structures into smaller
ones and fusion of small structures into conglomerate structures. The
characteristic time scale for the fission/fusion process is on the
order of minutes.
Title: Facular Contrast and Hot Wall Models of Flux Tubes
Authors: Topka, K. P.; Tarbell, T. D.; Title, A. M.
Bibcode: 1994AAS...185.8606T
Altcode: 1994BAAS...26.1465T
Solar rotation causes features on its surface to be viewed at different
angles. The appearance of active region faculae changes dramatically
with viewing angle. They have minimum contrast at disk center, but
appear bright near the limb. The nature of this center-limb variation
is related to the structure of the individual flux tubes comprising
faculae. One class of models depict a facula as an evacuated flux tube
with hot walls and a depressed cool floor (hot wall model). Another
depicts them as hot clouds, because of internal heating. Both can
explain the observed center-limb variation in contrast. In this paper
we ask whether there are other observable phenomena that can help
differentiate between these models. The observations were obtained at
the Swedish Solar Observatory, La Palma, using the Lockheed tunable
filter. The data consist of co-registered images of line-of-sight
magnetic field and of continuum intensity. The correlation between
strong magnetic field and continuum intensity in active region faculae
shows a remarkable and reproducible change between heliocentric angles
of 50deg and 60deg . These results support the hot wall model, but not
the hot cloud model. Hybrid models in which the flux tube has properties
of both models cannot by ruled out. This work has been supported by
NSF contract ATM-9320353, by NASA contracts NASW-4612 and NAS8-39747,
and by Lockheed IR funds.
Title: Flux Emergence in the Sunspot Moat
Authors: Title, A. M.; Shine, R. A.; Frank, Z. A.; Simon, G. W.;
Brandt, P. N.
Bibcode: 1994AAS...185.8602T
Altcode: 1994BAAS...26.1464T
On 13-15 June 1994 we obtained simultaneous movies of a sunspot in
NOAA active region 7731 through a 3 Angstroms band K line filter, the
LPARL tunable filter, and an 8 Angstroms G band filter. The data sets
allow us to make aligned magnetic, continuum, Doppler, K line, and
G band movies. The sunspot had a well developed moat. Flux emergence
occured throughout the moat. The initial signature of the emergence
was a transient dark elongated structure in the K line images that was
aligned radially with respect to the spot. Bright point pairs appeared
at the ends of these features in the K line and G band shortly after
their emergence. Magnetic field is observed cospatial with the K line
bright point pairs. The magnetic polarity of the end of the pair closest
to the spot is the same as the spot. The pairs of bright points move
across the moat in a radial direction away from the spot. When the
pairs reach the moat boundary the leading bright point merges with a
moat feature and the two disappear. The leading bright point's field
and the moat field cancel, since the moat boundary and the spot have
the same polarity. We believe that these features are different from
the long observed moving magnetic features associated with sunspots.
Title: Trace — The transition region and coronal explorer
Authors: Strong, K.; Bruner, M.; Tarbell, T.; Title, A.; Wolfson, C. J.
Bibcode: 1994SSRv...70..119S
Altcode:
TRACE is a single-instrument solar mission that will be put into
a Sunsynchronous polar orbit and will obtain continuous solar
observations for about 8 months per year. It will collect images of
solar plasmas at temperatures from 104 to 107
K, with 1-arcsec spatial resolution and excellent temporal resolution
and continuity. With such data, we expect to gain a new understanding
of many solar and stellar problems ranging from coronal heating to
impulsive magnetohydrodynamic phenomena.
Title: High-Resolution Observations of the Evershed Effect in Sunspots
Authors: Shine, R. A.; Title, A. M.; Tarbell, T. D.; Smith, K.; Frank,
Z. A.; Scharmer, Goran
Bibcode: 1994ApJ...430..413S
Altcode:
High spatial resolution movies of sunspots taken at the Swedish
Solar Observatory on La Palma reveal that the Evershed effect is time
dependent. Outward proper motions are visible in both the continuum
and Dopplergrams. These can be tracked over most of the width of
the penumbra and overlap regions that show inward moving penubral
grains. The radial spacing between the moving structures is about 2000
km, and they exhibit irregular repetitive behavior with a typical
interval of 10 minutes. These are probably the cause of 10 minutes
oscillations sometimes seen in a penumbral power spectra. Higher
velocities are spatially correlated with the relatively darker regions
between bright filaments. Regions with a strong variation in the Doppler
signal show peak-to-peak modulations of 1 km/s on an average velocity
of about 3-4 km/s. The proper motion velocity is approximately constant
from the iner penumbra and generally larger than the Doppler velocity
when both are interpreted as projections of horizontal motion. Regions
where thay are consistent suggest a typical horizontal velocity of
3.5 km/s. Some proper motion velocites as high as 7 km/s are seen,
but these are less certain. The temporal behavoir shows a correlation
between increased Doppler signal and increased continuum intensity,
the opposite of the spatial correlation. When spatially averaged
across filaments and over time, the averaged Evershed effect has a peak
horizontal component near the outer edge of the penumbra of 2.0 km/s
with evidence for a 200-400 m/s upward component. The latter depends
on an uncertain absolute velocity calibration. If real it could be
an actual upward component or a penumbral analogue of the convective
blueshift seen in the quiet Sun.
Title: Kinematic modelling of magnetoconvection
Authors: Simon, G. W.; Title, A. M.; Weiss, N. O.; Ginet, G. P.
Bibcode: 1994smf..conf..276S
Altcode:
No abstract at ADS
Title: Dynamics of the Evershed effect
Authors: Shine, R. A.; Title, A. M.; Tarbell, T. D.; Smith, K.; Frank,
Z. A.; Scharmer, G.
Bibcode: 1994ASIC..433..197S
Altcode:
No abstract at ADS
Title: An Analytical Model for Fluted Sunspots and its Relation with
Evershed Flow and X-Ray Anemone
Authors: Hurlburt, Neal E.; Martens, Petrus C.; Title, Alan M.;
Acton, Loren
Bibcode: 1994ASPC...68..300H
Altcode: 1994sare.conf..300H
No abstract at ADS
Title: Kinematic Modeling of Magnetic Field Diffusion at the Solar
Surface
Authors: Title, Alan M.; Simon, George W.; Weiss, Nigel O.
Bibcode: 1994ASPC...68...87T
Altcode: 1994sare.conf...87T
No abstract at ADS
Title: Movies of and Comments on the Organization of Flows and Fields
in Active Regions
Authors: Title, Alan
Bibcode: 1994ASPC...68...44T
Altcode: 1994sare.conf...44T
No abstract at ADS
Title: High resolution studies of sunspots and flux tubes
Authors: Title, Alan
Bibcode: 1994lock.reptR....T
Altcode:
This contract is for a three-year research study of sunspots and
magnetic flux tubes in the solar atmosphere, using tunable filter
images collected with a CCD camera during observing runs at the Canary
Islands observatories in Spain. The best observations are analyzed and
compared with theoretical models, to study the structure and dynamics
of sunspots, their connections with surrounding magnetic fields, and
the properties and evolution of smaller flux tubes in plage and quiet
sun. Scientific results are reported at conferences and published
in the appropriate journals. The contract is being performed by the
Solar and Astrophysics Laboratory, part of the Lockheed Palo Alto
Research Laboratory (LPARL) of the Research and Development Division
(RDD) of Lockheed Missiles and Space Co., Inc. (LMSC). The principal
investigator is Dr. Alan Title, and the research is done by him and
other scientific staff at LPARL and Solar Physics Research Corporation
(SPRC), often in collaboration with visiting scientists and students
from other institutions. Highlights during this reporting period include
completing the final version of a paper on the Evershed effect, writing
a paper on magnetic diffusion, continuing work on contrast of small
flux tubes, and work on the development of new models to interpret
our sunspots observations.
Title: An analytical model for fluted sunspots and a new
interpretation of Evershed flow
Authors: Martens, P. C.; Hurlburt, N.; Title, A. M.; Acton, L. A.
Bibcode: 1994ASIC..433..237M
Altcode:
No abstract at ADS
Title: The Solar Oscillation Investigation - Michelson Doppler Imager
(SOI-MDI)
Authors: Hoeksema, J. T.; Bogart, R. S.; Bush, R. I.; Milford, P. N.;
Pope, T.; Rosenberg, W.; Scherrer, P. H.; Springer, L.; Tarbell, T.;
Title, A.; Wolfson, J.; Zayer, I.
Bibcode: 1993BAAS...25.1192H
Altcode:
No abstract at ADS
Title: A Force-Free Model for Fluted Sunspots
Authors: Martens, P. C. H.; Hurlburt, N.; Title, A. M.
Bibcode: 1993BAAS...25R1218M
Altcode:
No abstract at ADS
Title: High Resolution Observations of the Evershed Flow in Sunspots
Authors: Shine, R.; Title, A.; Smith, K.; Scharmer, G.
Bibcode: 1993BAAS...25.1183S
Altcode:
No abstract at ADS
Title: The Quiet Sun Network and Solar Irradiance Variations
Authors: Topka, K. P.; Tarbell, T. D.; Title, A. M.
Bibcode: 1993BAAS...25R1183T
Altcode:
No abstract at ADS
Title: Diffusion of "Corks" Over the Solar Surface
Authors: Title, A. M.; Simon, G. W.; Weiss, N. O.
Bibcode: 1993BAAS...25Q1183T
Altcode:
No abstract at ADS
Title: Why put visible solar telescopes in space?
Authors: Title, A.
Bibcode: 1993ESASP1157..161T
Altcode: 1993srfs.book..161T
This paper will clarify why space observations are necessary and
also suggests some complementary ground and space solar physics
experiments. This paper does not, however, discuss the issue of whether
valuable science can be done with the data that visible telescopes
produce.
Title: Solar Coronal Magnetic Field Topology Inferred from High
Resolution Optical and X-ray Movies
Authors: Tarbell, T.; Frank, Z.; Hurlburt, N.; Morrison, M.; Shine,
R.; Title, A.; Acton, L.
Bibcode: 1993BAAS...25.1208T
Altcode:
No abstract at ADS
Title: La Palma Observations During the CoMStOC'92 Campaign
Authors: Shine, R.; Tarbell, T.; Topka, K.; Frank, Z.; Title, A.;
Scharmer, G.
Bibcode: 1993BAAS...25S1223S
Altcode:
No abstract at ADS
Title: Inclination of the Magnetic Lines-of-Force of Quiet Sun Network
Authors: Topka, K. P.; Tarball, T. D.; Title, A. M.; Lawrence, J.
Bibcode: 1993AAS...182.4803T
Altcode: 1993BAAS...25R.879T
Photometric measurements of the continuum contrast of active region
plage, after carefully removing all sunspots and pores, has been
obtained for several years from the Swedish Solar Observatory, La
Palma. More recently, similar measurements have been obtained for
magnetic elements in the network far from active regions. These data
were taken with the Lockheed tunable filter instrument using a CCD
camera. The measurements indicate that at disk center active region
plage is dark (negative contrast: intensity less than the surrounding
quiet sun), while the network is bright. Furthermore, active region
plage rapidly turns bright toward the limb; the network also brightens
but more slowly. We have constructed a simple model that assumes
that the magnetic lines-of-force are approximately vertical in active
region plage, while those in the quiet sun network are inclined at the
photosphere. This model correctly predicts the continuum contrast of
network at disk center, and also its variation from center-to-limb. This
provides evidence that the network is often inclined from vertical by
30 degrees or more. This work was supported by Lockheed IR Funds, by
NASA contracts NAS8-32805 (SOUP), NAS5-26813 (OSL), NAS5-30386 (MDI),
and NAS8-38106 (BSOUP), and NSF contract ATM-8912841.
Title: ``The Active Sun'': Educational Videotapes on Solar Physics
for College Astronomy
Authors: Hurlburt, N.; Title, A.; Tarbell, T.; Frank, Z.; Topka, K.;
Shine, R.
Bibcode: 1993AAS...182.1002H
Altcode: 1993BAAS...25..809H
We present a series of short, educational documentaries on solar
physics aimed at college-level general astronomy courses. These
tapes highlight recent advances in high-resolution solar astronomy
and in theoretical and computational modeling of solar physics
with particular focus on dynamical phenomena. The relevant physical
mechanisms, theoretical interpretations and observational techniques
are discussed. These include granulation, the theory of convection,
five-minute oscillations, sunspots, magnetic fields, seeing and
dopplergrams. VHS tapes are available to researchers and educators
through a variety of distributors. This work supported by Lockheed
Independent Research Funds.
Title: Solar Coronal Magnetic Field Topology Inferred from High
Resolution Optical and X-ray Movies
Authors: Tarbell, T.; Frank, Z.; Hurlburt, N.; Morrison, M.; Shine,
R.; Title, A.; Acton, L.
Bibcode: 1993AAS...182.4805T
Altcode: 1993BAAS...25R.880T
We are using high resolution digital movies of solar active regions
in optical and X-ray wavelengths to study solar flares and other
transients. The optical movies were collected at the Swedish Solar
Observatory on La Palma using the Lockheed tunable filtergraph
system, in May - July, 1992. They include longitudinal and transverse
magnetograms, H-alpha Doppler and intensity images at many wavelengths,
Ca K, Na D, and white light images. Simultaneous X-ray images from
Yohkoh are available much of the time. We are learning several ways to
establish the connectivity of some coronal magnetic field lines. Some
of the clues available are: magnetic footpoint polarities and transverse
field directions; H-alpha fibrils and loops seen in several wavelengths;
proper motion and Doppler shifts of blobs moving along field lines;
footpoint brightening in micro-flares; spreading of flare ribbons
during gradual phases of flares; X-ray morphology and correlations with
H-alpha; and draining of flare loops. Examples of each of these will
be shown on video. This work is supported by NASA Contracts NASW-4612
and NAS8-37334 and by Lockheed Independent Research Funds.
Title: Diffusion of ``Corks'' Over the Solar Surface
Authors: Title, A. M.; Simon, G. W.; Weiss, N. O.
Bibcode: 1993AAS...182.4804T
Altcode: 1993BAAS...25Q.880T
Test particles in flow fields generated by correlation tracking of
movies of the solar surface and kinematic models of the solar surface
quickly collect in stagnation points of the flow fields and remain
there. Test particles do not form a quasi-stable network pattern. The
diffusion coefficients generated from a net of kinematic models with a
range of cell sizes and lifetimes are not proportional to the cell size
squared divided by the cell lifetime as commonally assumed. Reasonable
estimates of cell sizes and lifetimes yield diffusiion coefficients that
are lower than the 600 km(2) /s used by Sheeley and his collaborators in
their surface diffusion models. We conclude that: 1) The appearance of
plages and enhanced network can not be explained by adjustment of the
cell sizes or surface velocities; and 2) diffusion is not sufficient
to explain the appearance of plages and enhanced network.
Title: On the Magnetic and Velocity Field Geometry of Simple Sunspots
Authors: Title, Alan M.; Frank, Zoe A.; Shine, Richard A.; Tarbell,
Theodore D.; Topka, Kenneth P.; Scharmer, Goran; Schmidt, Wolfgang
Bibcode: 1993ApJ...403..780T
Altcode:
It is presently shown that a simple sunspot model with azimuthal
variations in inclination, but lacking azimuthal field-strength
variations, is free from azimuthal Lorentz forces. The meridional
currents arising from the inclination variations are parallel to the
field lines, suggesting that a cylindrically symmetric magnetostatic
sunspot model can be perturbed into one with azimuthal variations in
inclination with adjustment of the meridional force balance.
Title: Observations of High Frequency and High Wavenumber Solar
Oscillations
Authors: Fernandes, D.; Scherrer, P.; Tarbell, T.; Title, A.
Bibcode: 1993ASPC...42..101F
Altcode: 1993gong.conf..101F
No abstract at ADS
Title: White-light movies of the solar photosphere from the SOUP
instrument on Spacelab 2 (Advances in Space Research 1986)
Authors: Title, A. M.; Tarbell, T. D.; Simon, G. W.; Acton, L.;
Duncan, D.; Ferguson, S.; Finch, M.; Frank, Z.; Kelly, G.; Lindgren,
R.; Morrill, M.; Pope, T.; Reeves, R.; Rehse, R.; Shine, R.; Topka,
K.; Harvey, J.; Leibacher, J.; Livingston, W.; November, L.
Bibcode: 1993inas.book..100T
Altcode:
No abstract at ADS
Title: The solar oscillations investigation - Michelson Doppler
Imager.
Authors: Hoeksema, J. Todd; Scherrer, P. H.; Bush, R. I.; Title, A.;
Tarbell, T.
Bibcode: 1992ESASP.348....9H
Altcode: 1992cscl.work....9H
The Solar Oscillations Investigation (SOI) has developed the Michelson
Doppler Imager (MDI) to investigate the properties of solar interior
using the tools of helioseismology and of the photosphere and
corona using more conventional techniques. A fundamental goal is
to understand the Sun by determining its structure and observing its
dynamics. The basic observables, velocity, intensity and magnetic field,
are computed on board from up to twenty 1024 by 1024 filtergrams made
each minute. Subsequent analysis will extend the region one can explore
downward into the solar interior and upward into the corona. While
the instrument is dedicated to producing an uninterrupted series
of helioseismology data, several magnetograms will be made each day
and special 8-hour campaigns are being developed to address specific
scientific questions, some in coordination with other SOHO instruments.
Title: Properties of the Smallest Solar Magnetic Elements. I. Facular
Contrast near Sun Center
Authors: Topka, K. P.; Tarbell, T. D.; Title, A. M.
Bibcode: 1992ApJ...396..351T
Altcode:
Measurements are presented which indicate that the continuum intensity
of facular areas in solar active regions, outside sunspots and pores, is
less than that of the quiet sun very near disk center. It is shown that
the observed continuum intensity of faculae at disk center near 5000
A is nearly 3 percent less than that of the quiet sun. The continuum
contrast increases rapidly away from disk center, reaching +2 percent
at 45 deg. The zero-crossing point, where the contrast changes sign,
occurs at 20-degree heliocentric angle. This is contrary to many earlier
observations. The constraint these observations place on the size
of flux tubes depends upon the value of the zero-crossing point. It
is proposed that most of the flux tubes in solar faculae may be very
small, in the range 50-100 km in diameter, and that inclination from
local vertical of about 10 deg at the photosphere is common on the
sun. Footpoints of opposite polarity tend to tilt toward one another.
Title: Comparison of Active Region Facular Contrast Measurements to
Simple Models
Authors: Topka, K. P.; Title, A. M.
Bibcode: 1992AAS...181.8104T
Altcode: 1992BAAS...24.1252T
No abstract at ADS
Title: A solar magnetic and velocity field measurement system for
Spacelab 2: The solar optical universal polarimeter (SOUP)
Authors: Tarbell, Theodore D.; Title, Alan M.
Bibcode: 1992lock.reptS....T
Altcode:
The Solar Optical Universal Polarimeter flew on the Shuttle Mission
Spacelab 2 (STS-51F) in August, 1985, and collected historic solar
observations. SOUP is the only solar telescope on either a spacecraft
or balloon which has delivered long sequences of diffraction-limited
images. These movies led to several discoveries about the solar
atmosphere which were published in the scientific journals. After
Spacelab 2, reflights were planned on the Space Shuttle Sunlab
Mission, which was cancelled after the Challenger disaster, and on
balloon flights, which were also cancelled for funding reasons. In
the meantime, the instrument was used in a productive program of
ground-based observing, which collected excellent scientific data
and served as instrument tests. This report gives an overview of
the history of the SOUP program, the scientific discoveries, and the
instrument design and performance.
Title: A solar magnetic and velocity field measurement system for
Spacelab 2: The Solar Optical Universal Polarimeter (SOUP)
Authors: Tarbell, Theodore D.; Title, Alan M.
Bibcode: 1992lock.reptR....T
Altcode:
The Solar Optical Universal Polarimeter (SOUP) flew on the shuttle
mission Spacelab 2 (STS-51F) in August, 1985, and collected
historic solar observations. SOUP is the only solar telescope on
either a spacecraft or balloon which has delivered long sequences of
diffraction-limited images. These movies led to several discoveries
about the solar atmosphere which were published in the scientific
journals. After Spacelab 2, reflights were planned on the shuttle Sunlab
mission, which was cancelled after the Challenger disaster, and on a
balloon flights, which were also cancelled for funding reasons. In
the meantime, the instrument was used in a productive program of
ground-based observing, which collected excellent scientific data and
served as instrument tests. Given here is an overview of the history
of the SOUP program, the scientific discoveries, and the instrument
design and performance.
Title: On the Differences between Plage and Quiet Sun in the Solar
Photosphere
Authors: Title, Alan M.; Topka, Kenneth P.; Tarbell, Theodore D.;
Schmidt, Wolfgang; Balke, Christiaan; Scharmer, Goran
Bibcode: 1992ApJ...393..782T
Altcode:
Time sequences of interleaved observations of the continuum intensity,
longitudinal magnetic field, vertical velocity in the midphotosphere,
and the line-center intensity in Ni I 6768 A were obtained in an
active-region plage and the surrounding relatively field-free area near
disk center. Spacetime Fourier filtering techniques are used to separate
the convective and oscillatory components of the solar atmosphere. The
properties of the photosphere are found to differ qualitatively and
quantitatively between the plage, where the field is 150 G or more,
and its quiet surroundings. The scale of granulation is smaller, the
contrast lower, and the temporal evolution slower in the plage than the
quiet sun. In the plage, the vertical velocity is reduced in amplitude
compared to the quiet sun, and there is little evidence of a granulation
pattern, while in the quiet sun the vertical flow pattern is similar in
size and shape to the underlying granulation pattern in the continuum.
Title: Observations of High-Frequency and High-Wavenumber Solar
Oscillations
Authors: Fernandes, D. N.; Scherrer, P. H.; Tarbell, T. D.; Title,
A. M.
Bibcode: 1992ApJ...392..736F
Altcode:
Doppler shift measurements of the Na D1 absorption line reveal solar
oscillations in a new regime of frequency and wavenumber. Oscillations
of vertical velocities in the temperature minimum and low chromosphere
of the sun are observed with frequencies ranging up to 9.5 mHz. The
fundamental modes appear with wavenumbers up to 5.33/Mm (equivalent
spherical harmonic degree 3710). No evidence for chromospheric modes
of 3-minute period is reported.
Title: Facular Contrast Near Solar Disk Center and the Inclination
of Magnetic Lines of Force from Local Vertical
Authors: Topka, K. P.; Tarbell, T. D.; Title, A. M.
Bibcode: 1992AAS...180.4004T
Altcode: 1992BAAS...24..793T
No abstract at ADS
Title: The Solar Oscillation Imager-Michelson Doppler Imager for SoHO
Authors: Title, A.; Tarbell, T.; Wolfson, J.; Scherrer, P.; Bush,
R.; Hoeksema, T.
Bibcode: 1992AAS...180.0606T
Altcode: 1992BAAS...24Q.737T
No abstract at ADS
Title: Optical Components of the Solar Oscillations Imager-Michelson
Doppler Imager
Authors: Tarbell, T.; Rosenberg, W.; Pope, T.; Huff, L.; Torgerson,
D.; Title, A.; Wolfson, J.; Scherrer, P.; Bush, R.; Hoeksema, T.
Bibcode: 1992AAS...180.0607T
Altcode: 1992BAAS...24R.737T
No abstract at ADS
Title: Kinematic Modeling of Active Region Decay
Authors: Simon, G. W.; Title, A. M.; Weiss, N. O.
Bibcode: 1992AAS...180.1101S
Altcode: 1992BAAS...24..746S
No abstract at ADS
Title: High resolution observations: the state of the art and beyond.
Authors: Title, A.; Tarbell, T.; Shine, R.; Topka, K.; Frank, Z.
Bibcode: 1992ESASP.344....9T
Altcode: 1992spai.rept....9T
Excellent telescopes on excellent sites with fast digital CCD cameras
and special purpose computers allow the collection of broad band images
at just the instants of good seeing. This has resulted in nearly optimal
movies of the solar surface for several hours. When longer exposures
are required for narrowband filtergrams or spectra it is not enough to
capture single images. However, big fast memories allow the collection
of many selected low signal-to-noise ratio images in real time, which
can be summed to achieve the desired signal to noise ratios. Adaptive
optics shows promise of diffraction limited images for limited fields
of view. Nevertheless, groundbased observations will always be limited
in their duration, uniformity, and resolution qualities which are
essential for understanding the development and evolution of small scale
processes. Until there are observations in space we will not be able
to completely understand either the processes in the solar atmosphere
or how processes occurring at different height are interrelated.
Title: Evolution and advection of solar mesogranulation
Authors: Muller, Richard; Auffret, Herve; Roudier, Thierry; Vigneau,
Jean; Simon, George W.; Frank, Zoe; Shine, Richard A.; Title, Alan M.
Bibcode: 1992Natur.356..322M
Altcode:
GRANULAR structure on the Sun's surface, with a typical scale
of 1-2 Mm, has been known since 1800, and one hundred years ago,
with the first observations by spectroheliograph1,2,
a mesh-like bright network was found with a characteristic scale
of 30 Mm (40''). This pattern was found, thirty years ago, to be
coincident with close-packed convective cells ('supergranulation')
revealed by Doppler observations3-5 to be nestling inside
the bright network. More recently6,7 an intermediate
'mesogranular' structure was found, with a characteristic scale of
3-10 Mm. We have obtained a three-hour sequence of observations at
the Pic du Midi observatory which shows the evolution of mesogranules
from appearance to disappearance with unprecedented clarity. We see
that the supergranules, which are known to carry along (advect) the
granules with their convective motion, also advect the mesogranules to
their boundaries. This process controls the evolution and disappearance
of mesogranules.
Title: Design Rationale of the Solar Ultraviolet Network / Sun
Authors: Dame, L.; Acton, L.; Bruner, M. E.; Connes, P.; Cornwell,
T. J.; Curdt, W.; Foing, B. H.; Hammer, R.; Harrison, R.; Heyvaerts,
J.; Karabin, M.; Marsch, E.; Martic, M.; Mattic, W.; Muller, R.;
Patchett, B.; Roca-Cortes, T.; Rutten, R. J.; Schmidt, W.; Title,
A. M.; Tondello, G.; Vial, J. C.; Visser, H.
Bibcode: 1992ESOC...39..995D
Altcode: 1992hrii.conf..995D
No abstract at ADS
Title: Observations of high frequency and high wavenumber solar
oscillations
Authors: Fernandes, D. N.; Scherrer, P. H.; Tarbell, T. D.; Title,
A. M.
Bibcode: 1992STIN...9232488F
Altcode:
Doppler shift measurements of the Na D1 absorption line
have revealed solar oscillations in a new regime of frequency and
wavenumber. Oscillations of vertical velocities in the temperature
minimum and low chromosphere of the Sun are observed with frequencies
ranging up to 9.5 mHz. The fundamental modes appear with wavenumbers
up to 5.33 M/m (equivalent spherical harmonic degree, 3710). We find
no evidence for chromospheric modes of a 3-minute period.
Title: High Resolution Observations of the Magnetic and Velocity
Field of Simple Sunspots
Authors: Title, Alan M.; Frank, Zoe A.; Shine, Richard A.; Tarbell,
T. D.; Topka, K. P.; Scharmer, Goran; Schmidt, Wolfgang
Bibcode: 1992ASIC..375..195T
Altcode: 1992sto..work..195T
We have observed the disk passage of relatively simple round sunspots
using a narrowband filter and a large format CCD detector and have
created magnetograms, Dopplergrams, and continuum images nearly
simultaneously. In addition the spectral resolution of the filter
allows the construction of 'spectra' for all points in the field of
view. The mean inclination of the magnetic field increases from 45-50
deg to 70-75 deg across the penumbra and there is a fluctuation of the
inclination angle about the mean of about 4 +/- 18 deg. The variation in
inclination is large enough that substantial amounts of magnetic field
are parallel to the solar surface from the mid to outer penumbra. The
Evershed flow tends to occur in the regions where the magnetic field
is horizontal. This suggests that the Evershed flow is confined to the
regions of horizontal fields. We show that a simple sunspot model with
azimuthal variations in inclination but no azimuthal variations of
field strength is free from azimuthal Lorentz forces. The meridional
component of the currents which arise from the azimuthal variation
in inclination are parallel to the field lines. This suggests that a
cylindrically symmetric magnetostatic sunspot model can be perturbed
into one with azimuthal variations in inclination with some adjustment
in the meridional force balance.
Title: Low-Cost Space Missions in Solar Physics or Astrophysics
Using Mass-Produced Spacecraft
Authors: Tarbell, T. D.; Jurcevich, B. K.; Title, A. M.; Topka, K. P.
Bibcode: 1991BAAS...23.1317T
Altcode:
No abstract at ADS
Title: Properties of the Smallest Magnetic Elements on the Sun
Authors: Topka, K. P.; Smith, K. L.; Tarbell, T. D.; Title, A. M.;
Scharmer, G.
Bibcode: 1991BAAS...23.1388T
Altcode:
No abstract at ADS
Title: Modeling Mesogranules and Exploders on the Solar Surface
Authors: Simon, G. W.; Title, A. M.; Weiss, N. O.
Bibcode: 1991ApJ...375..775S
Altcode:
Radial outflows in exploders and mesogranules can be modeled by
superposing Gaussian source functions. This model is used to explore
the relationship between mesogranules and exploders. Although it
is demonstarted that there is a mathematical equivalence between
mesogranules and exploders distributed normally about the mesogranule
centers, the results indicate that the observed mesogranular velocity
pattern is not consistent with a flow pattern generated by exploders
dropped randomly on the solar surface. Detailed comparisons with
observations suggest that the averaged mesogranular velocity is produced
by a combination of a persistent outflow from a source together with
exploders distributed randomly about its center. Similar analysis
also shows supergranules are not the result of random occurrences
of mesogranules.
Title: Observations of the Birth and Death of Mesogranules
Authors: Simon, G. W.; Title, A. M.; Shine, R. A.; Frank, Z.; Muller,
R.; Auffret, H.
Bibcode: 1991BAAS...23.1034S
Altcode:
No abstract at ADS
Title: Field Geometry of Sunspots Inferred from Inclination Effects
Authors: Title, A. M.; Frank, Z. A.; Shine, R. A.; Tarbell, T. D.
Bibcode: 1991BAAS...23R1052T
Altcode:
No abstract at ADS
Title: Sunspot Umbral and Penumbral Oscillations in Hα
Authors: Shine, R.; Tarbell, T.; Title, A.; Topka, K.; Frank, Z.;
Smith, K.
Bibcode: 1991BAAS...23.1033S
Altcode:
No abstract at ADS
Title: 1024 x 1024 CCD Cameras under Development and Operation at
Lockheed PARL
Authors: Zayer, I.; Duncan, D.; Edwards, C.; Kelly, G.; Levay, M.;
Morrill, M.; Title, A.; Tarbell, T.; Wolfson, J.; Rosenberg, W.
Bibcode: 1991BAAS...23.1056Z
Altcode:
No abstract at ADS
Title: Stokes Polarimetry of a Sunspot from the Swedish Solar
Observatory at La Palma
Authors: Topka, K. P.; Frank, Z. A.; Tarbell, T. D.; Title, A. M.;
Scharmer, G.
Bibcode: 1991BAAS...23Q1052T
Altcode:
No abstract at ADS
Title: A solar interferometric mission for ultrahigh resolution
imaging and spectroscopy: SIMURIS
Authors: Damé, L.; Acton, L.; Bruner, M.; Connes, P.; Cornwell, T.;
Foing, B. H.; Heyvaerts, J.; Lemaire, P.; Martić, M.; Muller, R.;
Porteneuve, J.; Roca Cortés, T.; Riehl, J.; Rutten, R.; Séchaud,
M.; Smith, P.; Thorne, A. P.; Title, A. M.; Vial, J. -C.; Visser,
H.; Weigelt, G.
Bibcode: 1991AdSpR..11a.383D
Altcode: 1991AdSpR..11..383D
SIMURIS is an interferometric investigation of the very fine structure
of the solar atmosphere from the photosphere to the corona. It was
proposed to ESA /1/, November 30 1989, for the Next Medium Size
Mission - M2, and accepted in February 1990 for an Assessment Study
in the context of the Space Station. The main scientific objectives
will be outlined, and the ambitious model payload featuring the Solar
Ultraviolet Network (SUN), a 2 m long monolithic array of 4 telescopes
of Ø20 cm, and the Imaging Fourier Transform Spectrometer (IFTS),
an UV and Visible Imaging Fourier Transform Spectrometer coupled to
a Ø40 cm Gregory, described.
Title: Solar physics at ultrahigh resolution from the space station
with the Solar Ultraviolet Network (SUN)
Authors: Damé, L.; Acton, L.; Bruner, M.; Connes, P.; Cornwell,
T.; Foing, B.; Heyvaerts, J.; Lemaire, P.; Martić, M.; Muller, R.;
Roca Cortés, T.; Riehl, J.; Rutten, R.; Title, A. M.; Vial, J. -C.;
Visser, H.; Weigelt, G.
Bibcode: 1991AdSpR..11e.267D
Altcode: 1991AdSpR..11..267D
The SUN experiment is a UV and visible Space Interferometer aimed at
ultra-high resolution in the solar atmosphere. It has been proposed
to ESA as part of the SIMURIS Mission Proposal which has recently
been accepted for an Assessment Study in the framework of the
Space Station. The 4 × 20 cm telescopes of the SUN linear array are
non-redundantly placed to cover a 2 m baseline, and the instrument makes
full use of stabilized interferometry potential, the 4 telescopes being
co-aligned and co-phased on a reference field on the sun. After a brief
outline of the scientific objectives, the concept of the instrument
is described, and its image reconstruction potential is illustrated.
Title: Results from high resolution solar images and spectra obtained
at the Pic du Midi Observatory (1986-1990)
Authors: Roudier, Th.; Muller, R.; Vigneau, J.; Auffret, H.; Espagnet,
O.; Simon, G. W.; Title, A. M.; Frank, Z.; Shine, R. A.; Tarbell,
T. D.; Mein, P.; Malherbe, J. M.
Bibcode: 1991AdSpR..11e.205R
Altcode: 1991AdSpR..11..205R
We present an overview of our recent results about solar granulation and
mesogranulation, obtained with Pic du Midi observations. These results
were obtained during 1986-1990 using image and spectrographic analysis
of high spatial resolution data. The study of the solar granulation,
with 2 Dim. ``Multichannel Subtractive Double Pass'' (M.S.D.P.) spectra,
shows a clear change of the dynamical regime at 3'' (⋍ 2200 km)
of the photospheric velocity field when oscillatory components are
filtered out. A three hour movie obtained on film at Pic du Midi
Observatory and analyzed at the Lockheed Research Laboratory and the
National Solar Observatory (Sacramento Peak) was used to calculate
the horizontal flow pattern. The mean lifetime of the diverging areas
related to mesogranulation is estimated at 3 hours; these diverging
areas are swept by the supergranulation flow towards the supergranule
boundary with a mean speed of 0.4 km/s.
Title: Simulating exploding granules and mesogranular flows
Authors: Simon, G. W.; Title, A. M.; Weiss, N. O.
Bibcode: 1991AdSpR..11e.259S
Altcode: 1991AdSpR..11..259S
Cellular convective motion at the solar surface can be simulated by a
suitable distribution of axisymmetric sources /1/. With this model we
represent randomly distributed exploding granules or mesogranules. The
effect of a given velocity field on the magnetic field is modelled
by inserting test particles (``corks'') and following their resultant
motions. An important question raised by the observations is whether
mesogranular flows are generated entirely by exploding granules
which recur in approximately the same location or whether there is a
persistent underlying circulation. Our model calculations suggest
that a combination of systematic cellular motion on a mesogranular scale
and recurrent exploding granules located near the mesogranular centers
is compatible with observed magnetic structures. We also generate
randomly-distributed exploders not tethered to mesogranular sites, and
the resulting cork patterns do not resemble those observed on the solar
surface. Finally we introduce a large-scale persistent supergranular
flow which transports the mesogranules and exploders towards the
supergranular network and obtain patterns not unlike those seen on
the Sun. Operated by the National Optical Astronomy Observatories
for the Association of Universities for Research in Astronomy, Inc.,
under contract with the National Science Foundation. Partial Support
for the National Solar Observatory is provided by the USAF under a
Memorandum of Understanding with the NSF.
Title: High-resolution observations of the solar granulation.
Authors: Topka, K. P.; Title, A. M.
Bibcode: 1991sia..book..727T
Altcode:
The opportunity to observe the solar surface from space and from
excellent groundbased sites, combined with enhanced digital image
recording and computer technology, has led to improved high-resolution
observations of solar granulation in the last decade. Today, granulation
movies over 1 hr long are available with spatial resolution of nearly
1/3″(=240 km on the solar surface). These new data have modified our
conception of solar granulation by showing it to be a more complicated
combination of different phenomena than was previously appreciated. The
smaller granules, for example, may be the result of the fragmentation
of larger granules due to turbulent small-scale flows. The new data
have been used to detect large-scale horizontal flows on the Sun's
surface, by the direct measurement of the proper motion of granules
during their lifetimes. These new results may also have important
implications for the heating of the solar chromosphere and corona.
Title: SOUP Observations of Solar Activity
Authors: Shine, R. A.; Scharmer, G.; Tarbell, T. D.; Title, A. M.;
Topka, K. P.
Bibcode: 1991max..conf..295S
Altcode:
No abstract at ADS
Title: Solar magnetic field strength determinations from high spatial
resolution filtergrams
Authors: Keller, C. U.; Stenflo, J. O.; Solanki, S. K.; Tarbell,
T. D.; Title, A. M.
Bibcode: 1990A&A...236..250K
Altcode:
Circularly polarized images with high spatial resolution (better than 1
arcsec) of a solar active region, obtained with a tunable filter in the
wings of Fe I 5247.1 A and Fe I 5250.2 A, have been analyzed in terms of
the magnetic line ratio technique introduced by Stenflo (1973). Whenever
a measurable amount of polarization is present, the distribution of
the observed magnetic-line ratio is compatible with a unique value,
which is randomly blurred by noise due to the photon statistics,
the CCD camera, and atmospheric distortions. There is no need for a
distribution of field strengths to explain the observed distribution of
the magnetic line ratio. Consequently, the observations are compatible
with a unique magnetic field strength in solar small-scale magnetic
elements of about 1000 G at the level of line formation. For a thin
flux tube, this corresponds to a field strength of approximately 2000
G at the level of continuum formation, which is in excellent agreement
with previous field strength determinations from low spatial resolution
spectra (4-10 arcsec).
Title: Kinematic Modeling of the Relations Among Exploders,
Mesogranules, and Supergranules
Authors: Simon, G. W.; Title, A. M.; Weiss, N. O.
Bibcode: 1990BAAS...22R1225S
Altcode:
No abstract at ADS
Title: Detailed Comparison of Quiet and Magnetic Sun
Authors: Topka, K.; Ferguson, S.; Shine, R.; Tarbell, T.; Title, A.;
Balke, C.; Scharmer, G.; Schmidt, W.
Bibcode: 1990BAAS...22R.879T
Altcode:
No abstract at ADS
Title: Penumbral Flows and Magnetic Fields
Authors: Shine, R.; Smith, K.; Tarbell, T.; Title, A.; Scharmer, G.
Bibcode: 1990BAAS...22..878S
Altcode:
No abstract at ADS
Title: Intermittency of Fine Scale Solar Magnetic Fields in the
Photosphere
Authors: Tarbell, T.; Acton, S.; Topka, K.; Title, A.; Schmidt, W.;
Scharmer, G.
Bibcode: 1990BAAS...22..878T
Altcode:
No abstract at ADS
Title: An Overview of the CIP
Authors: Title, A. M.
Bibcode: 1990BAAS...22..844T
Altcode:
No abstract at ADS
Title: Magnetic flux tubes and their relation to continuum and
photospheric features
Authors: Title, A.; Tarbell, T.; Topka, K.; Cauffman, D.; Balke, C.;
Scharmer, G.
Bibcode: 1990GMS....58..171T
Altcode:
An investigation is made of the relationship between photospheric
'filigree' light points, line-center brightness, and magnetic field,
as inferred from sets of individual images and films showing a distinct
difference between two classes of magnetic regions. While in the first
such region the vertical velocity field is average and the magnetic
field is mostly confined in narrow lanes, the granulation pattern
of the second scale is much smaller, the vertical velocity is lower,
and the magnetic field is less compact. Where granulation is normal,
excellent correlation is obtained between bright continuum, line-center,
and magnetic field line structure.
Title: High-Resolution Observations of Emerging Magnetic Fields and
Flux Tubes in Active Region Photosphere
Authors: Tarbell, T.; Ferguson, S.; Frank, Z.; Shine, R.; Title, A.;
Topka, K.; Scharmer, G.
Bibcode: 1990IAUS..138..147T
Altcode:
No abstract at ADS
Title: High Resolution Solar Physics from the Space Station with
Interferometric Techniques: The Solar Ultraviolet Network (SUN) -
Instrument &Objectives
Authors: Damé, L.; Acton, L.; Bruner, M.; Connes, P.; Cornwell, T.;
Foing, B.; Heyvaerts, J.; Jalin, R.; Lemaire, Ph.; Martic, M.; Moreau,
B.; Muller, R.; Roca Cortés, T.; Riehl, J.; Rutten, R.; Title, A. M.;
Vial, J. -C.; Visser, H.; Weigelt, G.
Bibcode: 1990PDHO....7..262D
Altcode: 1990dysu.conf..262D; 1990ESPM....6..262D
No abstract at ADS
Title: Structure and Evolution of the Large Scale Granulation
Authors: Muller, R.; Roudier, Th.; Vigneau, J.; Frank, Z.; Shine,
R.; Tarbell, T.; Title, A.; Simon, G.
Bibcode: 1990PDHO....7...44M
Altcode: 1990dysu.conf...44M; 1990ESPM....6...44M
A granulation movie of 3 hours has been performed at the Pic du Midi
Observatory on September 20, 1988.
Title: Solar convection.
Authors: Spruit, H. C.; Nordlund, A.; Title, A. M.
Bibcode: 1990ARA&A..28..263S
Altcode:
The current understanding of solar convection is examined in connection
with optical observations of the surface, helioseismological
observations of the interior, and theories and simulations of
compressible convection. Recent progress in these fields has been
documented in workshops on solar granulation, the solar photosphere,
and helioseismology.
Title: High Resolution Observations of the Photosphere
Authors: Title, A. M.; Shine, R. A.; Tarbell, T. D.; Topka, K. P.;
Scharmer, G. B.
Bibcode: 1990IAUS..138...49T
Altcode:
No abstract at ADS
Title: Formation of Network Bright Points by Granule Compression
Authors: Muller, R.; Roudier, Th.; Vigneau, J.; Frank, Z.; Shine,
R.; Tarbell, T.; Title, A.; Simon, G.
Bibcode: 1990PDHO....7..150M
Altcode: 1990dysu.conf..150M; 1990ESPM....6..150M
No abstract at ADS
Title: Intial Results of the Lockheed 1989 La Palma Observing Campaign
Authors: Topka, K.; Frank, Z.; Shine, R.; Smith, K.; Tarbell, T.;
Title, A.; Scharmer, G.
Bibcode: 1989BAAS...21.1111T
Altcode:
No abstract at ADS
Title: Solar Ultraviolet Network: an interferometric investigation
of the fundamental solar astrophysical scales
Authors: Dame, Luc; Moreau, Bernard G.; Cornwell, Timothy J.;
Visser, H.; Title, Alan M.; Acton, Loren W.; Aime, Claude; Braam,
Bart M.; Bruner, Marilyn E.; Connes, Pierre; Faucherre, Michel; Foing,
B. H.; Haisch, Bernhard M.; Hoekstra, Roel; Heyvaerts, Jean; Jalin,
Rene; Lemaire, Philippe; Martic, Milena; Muller, R.; Noens, J. C.;
Porteneuve, Jacques; Schulz-Luepertz, E.; von der Luehe, Oskar
Bibcode: 1989SPIE.1130..126D
Altcode:
The Solar UV Network (SUN) presently proposed is an interferometric
system, based on the principles of stabilized interferometry, which
will be capable of solar observations with spatial resolutions better
than 0.013 arcsec. SUN will consist of four 20-cm diameter telescopes
aligned nonredundantly on a 2-m baseline. SUN is judged to be ideally
deployable by the NASA Space Station, if implemented on a pointing
platform whose performance is of the order of the Instrument Pointing
System flown on Spacelab 2. The compact, nonredundant configuration of
SUN's telescopes will allow high-resolution imaging of a 2 x 2 arcsec
field on the solar disk.
Title: High - resolution observations of emerging magnetic flux
Authors: Tarbell, T. D.; Topka, K.; Ferguson, S.; Frank, Z.; Title,
A. M.
Bibcode: 1989hsrs.conf..506T
Altcode:
No abstract at ADS
Title: An overview of the Orbiting Solar Laboratory
Authors: Title, A. M.
Bibcode: 1989hsrs.conf...35T
Altcode:
No abstract at ADS
Title: Variation of granulation properties on a meso-granular scale
Authors: Brandt, P. N.; Ferguson, S.; Scharmer, G. B.; Shine, R. A.;
Tarbell, T. D.; Title, A. M.; Topka, K.
Bibcode: 1989hsrs.conf..473B
Altcode:
No abstract at ADS
Title: Proper Motion and Lifetime of Mesogranules
Authors: Frank, Z.; Muller, R.; Roudier, T.; Vigneau, J.; Shine, R.;
Tarbell, T.; Title, A.; Topka, K.; Simon, G.
Bibcode: 1989BAAS...21..841F
Altcode:
No abstract at ADS
Title: Short Term Evolution of Fine Scale Magnetic Structures
Authors: Topka, K.; Frank, Z.; Shine, R.; Tarbell, T.; Title, A.;
Scharmer, G.; Balke, A.
Bibcode: 1989BAAS...21..842T
Altcode:
No abstract at ADS
Title: Magnetic Field Inclination in Penumbra of a Round Sunspot
Observed at Very High Spatial Resolution
Authors: Title, A. M.; Frank, Z. A.; Shine, R. A.; Tarbell, T. D.;
Scharmer, G.
Bibcode: 1989BAAS...21Q.837T
Altcode:
No abstract at ADS
Title: Investigation of Active Regions at High Resolution by Balloon
Flights of the Solar Optical Universal Polarimeter (SOUP)
Authors: Tarbell, T.; Gilbreth, C.; Shine, R.; Title, A.; Topka, K.;
Wolfson, J.
Bibcode: 1989BAAS...21R.837T
Altcode:
No abstract at ADS
Title: Observations of Running Penumbral Waves
Authors: Shine, R.; Tarbell, T.; Title, A.; Topka, K.; Frank, Z.;
Scharmer, G.
Bibcode: 1989BAAS...21..837S
Altcode:
No abstract at ADS
Title: 1024 X 1024 Pixel Cameras for Imaging the Sun in Visible,
Near-UV,and Near-IR Wavelengths
Authors: Duncan, D.; Edwards, C.; Levay, M.; Morrill, M.; Title, A.;
Wolfson, J.; Hovland, L.
Bibcode: 1989BAAS...21R.848D
Altcode:
No abstract at ADS
Title: An Overview of the Orbiting Solar Laboratory
Authors: Title, A. M.
Bibcode: 1989BAAS...21..832T
Altcode:
No abstract at ADS
Title: Ground-Based Tunable Filter Observations
Authors: Title, A. M.; Tarbell, T. D.; Wolfson, C. J.
Bibcode: 1989ASIC..263...25T
Altcode: 1989ssg..conf...25T
No abstract at ADS
Title: Active Optics, Anisoplanatism, and the Correction of
Astronomical Images
Authors: Peri, M. L.; Smithson, R. C.; Acton, D. S.; Frank, Z. A.;
Title, A. M.
Bibcode: 1989ASIC..263...77P
Altcode: 1989ssg..conf...77P
No abstract at ADS
Title: An Overview of the Orbiting Solar Laboratory
Authors: Title, A. M.
Bibcode: 1989ASIC..263...29T
Altcode: 1989ssg..conf...29T
No abstract at ADS
Title: Details of Large Scale Solar Motions Revealed by Granulation
Test Particles
Authors: Simon, G. W.; November, L. J.; Ferguson, S. H.; Shine, R. A.;
Tarbell, T. D.; Title, A. M.; Topka, K. P.; Zirin, H.
Bibcode: 1989ASIC..263..371S
Altcode: 1989ssg..conf..371S
No abstract at ADS
Title: Statistical Properties of Solar Granulation Derived from the
SOUP Instrument on Spacelab 2
Authors: Title, A. M.; Tarbell, T. D.; Topka, K. P.; Ferguson, S. H.;
Shine, R. A.; SOUP Team
Bibcode: 1989ApJ...336..475T
Altcode:
Computer algorithms and statistical techniques were used to identify,
measure, and quantify the properties of solar granulation derived
from movies collected by the Solar Optical Universal Polarimeter on
Spacelab 2. The results show that there is neither a typical solar
granule nor a typical granule evolution. A granule's evolution is
dependent on local magnetic flux density, its position with respect to
the active region plage, its position in the mesogranulation pattern,
and the evolution of granules in its immediate neighborhood.
Title: Optical disk processing of solar images.
Authors: Title, A.; Tarbell, T.
Bibcode: 1989GMS....54...31T
Altcode: 1989sspp.conf...31T
The current generation of space and ground-based experiments in solar
physics produces many megabyte-sized image data arrays. Optical
disk technology is the leading candidate for convenient analysis,
distribution, and archiving of these data. The authors have been
developing data analysis procedures which use both analog and digital
optical disks for the study of solar phenomena.
Title: Flows, Random Motions and Oscillations in Solar Granulation
Derived from the SOUP Instrument on Spacelab 2
Authors: Title, A. M.; Tarbell, T. D.; Topka, K. P.; Ferguson, S. H.;
Shine, R. A.; SOUP Team
Bibcode: 1989ASIC..263..225T
Altcode: 1989ssg..conf..225T
No abstract at ADS
Title: Magnetoconvection on the solar surface.
Authors: Simon, G. W.; Title, A. M.; Topka, K. P.; Tarbell, T. D.;
Shine, R. A.; Ferguson, S. H.; Zirin, H.
Bibcode: 1989GMS....54...53S
Altcode: 1989sspp.conf...53S
The authors describe and illustrate the first high-resolution
observations of horizontal flows on the solar surface and their relation
to magnetic field structure seen in the Sun's photosphere.
Title: Vortex Motion of the Solar Granulation
Authors: Brandt, P. N.; Scharmer, G. B.; Ferguson, S. H.; Shine,
R. A.; Tarbell, T. D.; Title, A. M.
Bibcode: 1989ASIC..263..305B
Altcode: 1989ssg..conf..305B
No abstract at ADS
Title: Investigation of active regions at high resolution by balloon
flights of the Solar Optical Universal Polarimeter (SOUP)
Authors: Tarbell, T.; Frank, Z.; Gilbreth, C.; Shine, R.; Title, A.;
Topka, K.; Wolfson, J.
Bibcode: 1989dots.work..310T
Altcode:
SOUP is a versatile, visible-light solar observatory, built for space
or balloon flight. It is designed to study magnetic and velocity
fields in the solar atmosphere with high spatial resolution and
temporal uniformity, which cannot be achieved from the surface of the
earth. The SOUP investigation is carried out by the Lockheed Palo Alto
Research Laboratory, under contract to NASA's Marshall Space Flight
Center. Co-investigators include staff members at a dozen observatories
and universities in the U.S. and Europe. The primary objectives of the
SOUP experiment are: to measure vector magnetic and velocity fields in
the solar atmosphere with much better spatial resolution than can be
achieved from the ground; to study the physical processes that store
magnetic energy in active regions and the conditions that trigger
its release; and to understand how magnetic flux emerges, evolves,
combines, and disappears on spatial scales of 400 to 100,000 km. SOUP
is designed to study intensity, magnetic, and velocity fields in the
photosphere and low chromosphere with 0.5 arcsec resolution, free of
atmospheric disturbances. The instrument includes: a 30 cm Cassegrain
telescope; an active mirror for image stabilization; broadband film
and TV cameras; a birefringent filter, tunable over 5100 to 6600 A
with 0.05 A bandpass; a 35 mm film camera and a digital CCD camera
behind the filter; and a high-speed digital image processor.
Title: The Michelson Doppler imager for the solar oscillations imager
program on SOHO.
Authors: Hoeksema, J. T.; Scherrer, Philip H.; Title, A. M.; Tarbell,
T. D.
Bibcode: 1988ESASP.286..407H
Altcode: 1988ssls.rept..407H
The Michelson Doppler Imager (MDI) will be the instrument used
in the Solar Oscillations Imager Program on SOHO. MDI will make a
line-of-sight velocity map of the full solar disk with 2 arc-second
pixels each minute. The instrument will be a modification of the
Fourier Tachometer and will operate by using narrow bandpass solar
images at four wavelengths to measure the line profile of the Ni
I line at 6768 Å. This method is relatively insensitive to line
profile changes and has a linear response to velocity. The instrument
is also capable of making partial maps with 0.7 arc-sec pixels. All
data will be transmitted to the ground for two continuous months
each year and 8 hours each day (160 kilobits/sec). At all times the
on-board computer will compute and transmit a selection of modes
(5 kilobits/sec) to take full advantage of the advantages of a space
based telescope. Line-of-sight magnetic fields will also be measured
regularly. The flight instrument will be built by the Lockheed Palo
Alto Research Laboratory.
Title: Observations of f- and p-mode oscillations of high degree
(500 < l < 2500) in quiet and active Sun.
Authors: Tarbell, T. D.; Peri, M.; Frank, Z.; Shine, R.; Title, A. M.
Bibcode: 1988ESASP.286..315T
Altcode: 1988ssls.rept..315T
Spectra (l-ν diagrams) from high resolution observations taken at
the Vacuum Tower Telescope (NSO/Sunspot) are presented. The raw data
are CCD images taken through the SOUP narrowband filter in Fe I 5576
Å. Four filtergrams spaced through the spectral line are combined to
form velocity movies. Spectra for 80 minutes of data with 0.5 - 1.5
arcsecond resolution are presented for the entire field-of-view and
for quiet and magnetic (plage) subregions. Ridges f and p1 -
p5 are evident in velocity spectra, extending to l = 2500(f),
l = 1800(p1), and l = 1200(p2). Much less power is
seen in the magnetic region than in the quiet sun. Three-dimensional
Fourier filtering shows that oscillation velocity amplitude drops
sharply at the boundary of the active region for each family of modes
considered.
Title: SOI: The Solar Oscillations Imager on SOHO
Authors: Scherrer, P. H.; Hoeksema, J. T.; Bogart, R. S.; Walker,
A. B. C., Jr.; Title, A. M.; Tarbell, T. D.; Wolfson, C. J.; Brown,
T. M., Jr.; Christensen-Dalsgaard, J.; Gough, D. O.
Bibcode: 1988sohi.rept...25S
Altcode:
The Solar Oscillations Imager (SOI) program for SOHO (solar and
heliospheric observatory) is described. It will consist of a Michelson
Doppler Imager (MDI) instrument, a facility providing data reduction
and analysis capability, and a coordinated set of investigations
designed to address a set of science objectives. The MDI is designed
to take advantage of the anticipated SOHO telemetry by organizing
the observations into four observation programs: structure (at all
times), dynamics (two months per year), campaign (eight hours per day,
ten months per year), and magnetic fields (few minutes per day). The
MDI will measure line-of-sight velocity by Doppler shift, transverse
velocity by local correlation tracking, line and continuum intensity,
and line-of-sight magnetic fields with both 4 and 1.4 arc-second
resolution (2 and 0.7 arc-sec pixels respectively).
Title: High-resolution digital movies of emerging flux and horizontal
flows in active regions on the sun
Authors: Topka, K.; Ferguson, S.; Frank, Z.; Tarbell, T.; Title, A.
Bibcode: 1988fnsm.work..283T
Altcode:
High-resolution observations of active regions in many wavelength bands
obtained at the Vacuum Tower Telescope of NSO/Sunspot (Sacramento Peak)
are presented. The SOUP tunable filter, HRSO 1024 x 1024 CCD camera,
and a sunspot tracker for image stabilization were used. Subarrays of
512 x 512 pixels were processed digitally and recorded on videodisk
in movie format. The movies with 0.5 to 1 arcsecond resolution of
the following simultaneous observations were shown: green continuum,
longitudinal magnetogram, Doppler velocity, Fe I 5576 A line center,
H alpha wings, and H alpha line center. The best set of movies show a
90 x 90 arcsecond field-of-view of an active region at S29, W11. When
viewed at speeds of a few thousand times real-time, the photospheric
movies clearly show the active region fields being distorted by a
remarkable combination of systematic flows and small eruptions of new
flux. Flux emergence is most easily discovered in line center movies:
an elongated dark feature appears first, followed soon after by bright
points at one or both ends. A brief, strong upflow is seen when the
dark feature first appears; downflow in the bright points persists
much longer. The magnetic flux appears to increase gradually over this
extended period. Some of the flux emergence events were studied in
detail, with measurements of horizontal and vertical velocities and
magnetic flux versus time within one footpoint of the loop.
Title: Statistical properties of solar granulation from the SOUP
instrument on Spacelab 2
Authors: Topka, K.; Title, A.; Tarbell, T.; Ferguson, S.; Shine, R.
Bibcode: 1988fnsm.work..294T
Altcode:
The Solar Optical Universal Polarimeter (SOUP) on Spacelab 2 collected
movies of solar granulation completely free from atmospheric blurring,
and are not degraded by pointint jitter (the pointing stability
was 0.003 sec root mean square). The movies illustrate that the
solar five minute oscillation has a major role in the appearance of
solar granulation and that exploding granules are a common feature
of the granule evolution. Using 3-D Fourier filtering techniques
the oscillations were removed and it was demonstrated that the
autocorrelation lifetime of granulation is a factor of two greater
in magnetic field regions than in field-free quiet sun. Horizontal
velocities were measured and flow patterns were observed on the scale of
meso- and super granulation. In quiet regions the mean flow velocity
is 370 m/s while in the magnetic regions it is about 125 m/s. It
was also found that the root mean square (RMS) fluctuating horizonal
velocity field is substantially greater in quiet sun than in strong
magnetic field regions. By superimposing the location of exploding
granules on the average flow maps it was found that they appear almost
exclusively in the center of mesogranulation size flow cells. Because
of the nonuniformity of the distribution of exploding granules, the
evolution of the granulation pattern in mesogranule cell centers and
boundaries differs fundamentally. It is clear from this study there
is neither a typical granule nor a typical granule evolution.
Title: Observations of photospheric magnetic fields and shear flows
in flaring active regions
Authors: Tarbell, T.; Ferguson, S.; Frank, Z.; Title, A.; Topka, K.
Bibcode: 1988fnsm.work...50T
Altcode:
Horizontal flows in the photosphere and subsurface convection zone move
the footpoints of coronal magnetic field lines. Magnetic energy to power
flares can be stored in the corona if the flows drive the fields far
from the potential configuration. Videodisk movies were shown with 0.5
to 1 arcsecond resolution of the following simultaneous observations:
green continuum, longitudinal magnetogram, Fe I 5576 A line center
(mid-photosphere), H alpha wings, and H alpha line center. The movies
show a 90 x 90 arcsecond field of view of an active region at S29,
W11. When viewed at speeds of a few thousand times real-time, the
photospheric movies clearly show the active region fields being
distorted by a remarkable combination of systematic flows and small
eruptions of new flux. Magnetic bipoles are emerging over a large area,
and the polarities are systematically flowing apart. The horizontal
flows were mapped in detail from the continuum movies, and these may
be used to predict the future evolution of the region. The horizontal
flows are not discernable in H alpha. The H alpha movies strongly
suggest reconnection processes in the fibrils joining opposite
polarities. When viewed in combination with the magnetic movies,
the cause for this evolution is apparent: opposite polarity fields
collide and partially cancel, and the fibrils reconnect above the
surface. This type of reconnection, driven by subphotospheric flows,
complicates the chromospheric and coronal fields, causing visible
braiding and twisting of the fibrils. Some of the transient emission
events in the fibrils and adjacent plage may also be related.
Title: Fractal Geometry of Convective Flows and Magnetic Fields in
the Solar Atmosphere
Authors: Tarbell, T.; Ferguson, S.; Title, A.; Scharmer, G.; Brandt, P.
Bibcode: 1988BAAS...20Q1010T
Altcode:
No abstract at ADS
Title: Observations of Granulation in Quiet and Magnetic Sun from
the Swedish Solar Observatory on LaPalma
Authors: Topka, K.; Ferguson, S.; Frank, Z.; Shine, R.; Tarbell, T.;
Title, A.; Wolfson, J.; Scharmer, G.; Brandt, P.
Bibcode: 1988BAAS...20S1010T
Altcode:
No abstract at ADS
Title: On the Feasibility of Correlation Tracking at Moderate
Resolution
Authors: Bogart, R. S.; Ferguson, S. H.; Scherrer, P. H.; Tarbell,
T. D.; Title, A. M.
Bibcode: 1988SoPh..116..205B
Altcode:
The SOUP experiment demonstrated that photospheric surface flows can
be measured by correlation tracking of white-light intensity features
at high resolution (November et al., 1987). In order to assess
the feasibility of this technique with observations made at lower
resolution, we have applied it to the same SOUP data artificially
degraded, but still free of seeing distortion. Comparison with the
velocity structures inferred from the original data shows generally
good agreement when the resolution is better than about 2″. The
radial outflow from a sunspot penumbra, however, can only be seen with
resolution of better than 1″. With resolution of worse than 2″,
the inferred velocity fields rapidly lose coherence, while resolution of
better than 1″ yields little improvement. We conclude that apertures
as small as 10-14 cm on a space-based platform will be useful for the
measurement of large-scale horizontal motions.
Title: Solar Activity and Flare Observations from the Swedish Solar
Observatory on La Palma
Authors: Wolfson, J.; Ferguson, S.; Frank, Z.; Shine, R.; Tarbell,
T.; Title, A.; Topka, K.; Scharmer, G.; Brandt, P.; Gurman, J.
Bibcode: 1988BAAS...20..978W
Altcode:
No abstract at ADS
Title: Measurements of Turbulent Diffusion by Solar Granulation in
Quiet and Magnetic Areas
Authors: Title, A.; Ferguson, S.; Tarbell, T.; Scharmer, G.; Brandt, P.
Bibcode: 1988BAAS...20R1010T
Altcode:
No abstract at ADS
Title: Vortex flow in the solar photosphere
Authors: Brandt, P. N.; Scharmer, G. B.; Ferguson, S.; Shine, R. A.;
Tarbell, T. D.; Title, A. M.
Bibcode: 1988Natur.335..238B
Altcode:
Convective flow fields in the solar atmosphere play a key role in the
concentration and dispersal of magnetic flux1, but because
the individual flow elements-the solar granules-are a few arcsec or less
in size, studies of their motions have been limited by the distortion
and blurring of the Earth's atmosphere ('seeing'). We report here a
very high-quality series of granulation images taken at the new Swedish
Solar Observatory on La Palma (Canary Islands) which have permitted
flow measurements at the sub-arcsec level. These movies show a vortex
structure which visibly dominates the motion of the granules in its
neighbourhood and persists for the 1.5 h duration of the movie. If such
vortices are a common feature of the solar convective zone, they may
provide an important mechanism for the heating of stellar chromospheres
and coronae by twisting the footprints of magnetic flux tubes.
Title: Polar observatories
Authors: Spruit, H. C.; Title, A. M.; Peterson, R. C.
Bibcode: 1988Natur.334..466S
Altcode:
No abstract at ADS
Title: On the Relation between Photospheric Flow Fields and the
Magnetic Field Distribution on the Solar Surface
Authors: Simon, George W.; Title, A. M.; Topka, K. P.; Tarbell, T. D.;
Shine, R. A.; Ferguson, S. H.; Zirin, H.; SOUP Team
Bibcode: 1988ApJ...327..964S
Altcode:
Using the technique of local correlation tracking on a 28 minute time
sequence of white-light images of solar granulation, the horizontal
flow field on the solar surface is measured. The time series was
obtained by the Solar Optical Universal Polarimeter (SOUP) on Spacelab 2
(Space Shuttle flight 51-F) and is free from atmospheric blurring and
distortion. The SOUP flow fields have been compared with carefully
aligned magnetograms taken over a nine hour period at the Big Bear
Solar Observatory before, during, and after the SOUP images. The flow
field and the magnetic field agree in considerable detail: vectors which
define the flow of the white-light intensity pattern (granulation) point
toward magnetic field regions, magnetic fields surround flow cells, and
magnetic features move along the flow arrows. The projected locations
of free particles ('corks') in the measured flow field congregate at
the same locations where the magnetic field is observed.
Title: Observations of F-and P-Mode Oscillations of High Degree
(500< <3500) in Quiet and Active Sun
Authors: Peri, M.; Frank, Z.; Shine, R.; Tarbell, T.; Title, A.
Bibcode: 1988BAAS...20..702P
Altcode:
No abstract at ADS
Title: Observations of Photospheric Magnetic Fields and Shear Flows
in Flaring Active Regions
Authors: Tarbell, T.; Ferguson, S.; Frank, Z.; Title, A.; Topka, K.
Bibcode: 1988BAAS...20..744T
Altcode:
No abstract at ADS
Title: High-Resolution Digital Movies of Emerging Flux and Horizontal
Flows in Active Regions on the Sun
Authors: Tarbell, T.; Ferguson, S.; Frank, Z.; Title, A.; Topka, K.
Bibcode: 1988BAAS...20..680T
Altcode:
No abstract at ADS
Title: Solar Granulation Movies of Exceptional Spatial Resolution:
Observations and Simulations of Horizontal Convective Flows
Authors: Title, A.; Shine, R.; Ferguson, S.; Tarbell, T.; Brandt,
P.; Scharmer, G.
Bibcode: 1988BAAS...20R.679T
Altcode:
No abstract at ADS
Title: Statistical Properties of Solar Granulation from the SOUP
Instrument on Spacelab 2
Authors: Topka, K.; Title, A.; Tarbell, T.; Ferguson, S.; Shine, R.
Bibcode: 1988BAAS...20Q.679T
Altcode:
No abstract at ADS
Title: Variability of solar mesogranulation
Authors: Simon, G. W.; November, L. J.; Acton, L. W.; Ferguson, S. H.;
Shine, R. A.; Tarbell, T. D.; Title, A. M.; Topka, K. P.; Zirin, H.
Bibcode: 1988AdSpR...8g.169S
Altcode: 1988AdSpR...8..169S
From white-light photographs of solar granulation obtained with the
SOUP instrument on Space Shuttle Flight STS-19 we have measured the
motions of granules using local correlation tracking techniques. The
granules are organized into larger-scale structures (mesogranular and
supergranular) which exhibit outflow from upwellings, convergence into
sinks, as well as significant vorticity. Magnetic fields follow these
same flow patterns. We describe these velocity structures, and suggest
that their effect on magnetic field structures may be important to
the solar flare buildup process.
Title: Correlation Lifetimes of Quiet and Magnetic Granulation from
the SOUP Instrument on Spacelab 2
Authors: Title, A.; Tarbell, T.; Topka, K.; Acton, L.; Duncan, D.;
Ferguson, S.; Finch, M.; Frank, Z.; Kelly, G.; Lindgren, R.; Morrill,
M.; Pope, T.; Reeves, R.; Rehse, R.; Shine, R.; Simon, G.; Harvey,
J.; Leibacher, J.; Livingston, W.; November, L.; Zirker, J.
Bibcode: 1988ApL&C..27..141T
Altcode:
The time sequences of diffraction limited granulation images obtained by
the Solar Optical Universal Polarimeter on Spacelab 2 are presented. The
uncorrection autocorrelation limetime in magnetic regions is dominated
by the 5-min oscillation. The removal of this oscillation causes the
autocorrelation lifetime to increase by more than a factor of 2. The
results suggest that a significant fraction of granule lifetimes are
terminated by nearby explosions. Horizontal displacements and transverse
velocities in the intensity field are measured. Lower limits to the
lifetime in the quiet and magnetic sun are set at 440 s and 950 s,
respectively.
Title: The relation between convection flows and magnetic structure
at the solar surface
Authors: Simon, G. W.; November, L. J.; Acton, L. W.; Title, A. M.;
Tarbell, T. D.; Topka, K. P.; Shine, R. A.; Ferguson, S. H.; Weiss,
N. O.; Zirin, H.
Bibcode: 1988AdSpR...8k.133S
Altcode: 1988AdSpR...8..133S
We describe recent results from the comparison of data from the Solar
Optical Universal Polarimeter instrument on Spacelab 2 and magnetograms
from Big Bear Solar Observatory. We show that the Sun's surface velocity
field governs the structure of the observed magnetic field over the
entire solar surface outside sunspots and pores. We attempt to describe
the observed flows by a simple axisymmetric plume model. Finally,
we suggest that these observations may have important implications
for the prediction of solar flares, mass ejections, and coronal heating.
Title: More than a solar cycle of synoptic solar and coronal data:
a video presentation.
Authors: Hoeksema, J. T.; Herant, M.; Scherrer, P. H.; Title, A. M.
Bibcode: 1988sscd.conf..376H
Altcode:
Color video movies of synoptic observations of the sun and corona
can now be created. Individual analog frames on laser disc can be
referenced digitally and played back at any speed. The authors have
brought together photospheric magnetic field data from the Wilcox Solar
Observatory at Standford and the National Solar Observatory, model
computations of the coronal magnetic field, and coronal data from the
Sacramento Peak coronagraph and the Mauna Loa K-coronameter and made a
series of movies presenting the data sets individually and in comparison
with one another. This paper presents a description of each of the data
sets and movies developed thus far and briefly outlines some of the
more interesting and obvious features observed when viewing the movies.
Title: More than a solar cycle of synoptic solar and coronal data:
A video presentation
Authors: Hoeksema, J. T.; Herant, M.; Scherrer, P. H.; Title, A. M.
Bibcode: 1987STIN...8829708H
Altcode:
Color video movies of synoptic observations of the sun and corona
can now be created. Individual analog frames on laser discs can be
referenced digitally and played back at any speed. We have brought
together photospheric magnetic field data from the Wilcox Solar
Observatory at Stanford and the National Solar Observatory, model
computations of the coronal magnetic field, and coronal data from the
Sacramento Peak coronagraph and the Mauna Loa K-coronameter and made a
series of movies presenting the data sets individually and in comparison
with one another. This paper presents a description of each of the data
sets and movies developed thus far and briefly outlines some of the
more interesting and obvious features observed when viewing the movies.
Title: White Light Sunspot Observations from the Solar Optical
Universal Polarimeter on Spacelab-2
Authors: Shine, R. A.; Title, A. M.; Tarbell, T. D.; Topka, K. P.
Bibcode: 1987Sci...238.1264S
Altcode:
The flight of the Solar Optical Universal Polarimeter on Spacelab-2
provided the opportunity for the collection of time sequences of
diffraction-limited (0.5 arc second) solar images with excellent
pointing stability (0.003 arc second) and with freedom from the
distortion that plagues ground-based images. A series of white-light
images of active region 4682 were obtained on 5 August 1985, and
the area containing the sunspot has been analyzed. These data have
been digitally processed to remove noise and to separate waves from
low-velocity material motions. The results include (i) proper motion
measurements of a radial outflow in the photospheric granulation
pattern just outside the penumbra; (ii) discovery of occasional bright
structures (``streakers'') that appear to be ejected outward from the
penumbra; (iii) broad dark ``clouds'' moving outward in the penumbra,
in addition to the well-known bright penumbral grains moving inward;
(iv) apparent extensions and contractions of penumbral filaments over
the photosphere; and (v) observation of a faint bubble or looplike
structure that seems to expand from two bright penumbral filaments
into the photosphere.
Title: Vortex Flow in Granulation
Authors: Scharmer, G.; Brandt, P.; Title, A.; Shine, R.; Ferguson, S.
Bibcode: 1987BAAS...19Q1118S
Altcode:
No abstract at ADS
Title: High-Resolution CCD Observations of Doppler and Magnetic
Images in the Solar Photosphere
Authors: Tarbell, T. D.; Frank, Z. A.; Morrill, M. E.; Shine, R. A.;
Topka, K. P.; Title, A. M.
Bibcode: 1987BAAS...19.1117T
Altcode:
No abstract at ADS
Title: Power Spectra of Solar Granulation
Authors: Acton, D. S.; Brandt, P.; Scharmer, G.; Dunn, D.; Tarbell,
T. D.; Title, A. M.; Smithson, R. C.
Bibcode: 1987BAAS...19.1118A
Altcode:
No abstract at ADS
Title: Sunspot observations from the SOUP instrument on Spacelab 2.
Authors: Shine, R. A.; Title, A. M.; Tarbell, T. D.; Acton, L.; Duncan,
D.; Ferguson, S. H.; Finch, M.; Frank, Z.; Kelly, G.; Lindgren, R.
Bibcode: 1987NASCP2483..133S
Altcode: 1987tphr.conf..133S
A series of white light images obtained by the SOUP instrument on
Spacelab 2 of active region 4682 on August 5, 1985 were analyzed
in the area containing sunspots. Although the umbra of the spot is
underexposed, the film is well exposed in the penumbral regions. These
data were digitally processed to remove noise and to separate p-mode
oscillations from low velocity material motions. The results of this
preliminary investigation include: (1) proper motion measurements of
a radial outflow in the photospheric granulation pattern just outside
the penumbra; (2) discovery of occasional bright structures (streakers)
that appear to be ejected outward from the penumbra; (3) broad dark
clouds moving outward in the penumbra in addition to the well known
bright penumbral grains moving inward; (4) apparent extensions and
contractions of penumbral filaments over the photosphere; and (5)
observation of a faint bubble or loop-like structure which seems to
expand from two bright penumbral filaments into the photosphere.
Title: Large-scale horizontal flows from SOUP observations of solar
granulation.
Authors: November, L. J.; Simon, G. W.; Tarbell, T. D.; Title, A. M.;
Ferguson, S. H.
Bibcode: 1987NASCP2483..121N
Altcode: 1987tphr.conf..121N
Using high-resolution time-sequence photographs of solar granulation
from the SOUP experiment on Spacelab 2 the authors observed large-scale
horizontal flows in the solar surface. The measurement method is
based upon a local spatial cross correlation analysis. The horizontal
motions have amplitudes in the range 300 to 1000 m/s. Radial outflow of
granulation from a sunspot penumbra into the surrounding photosphere is
a striking new discovery. Both the supergranulation pattern and cellular
structures having the scale of mesogranulation are seen. The vertical
flows that are inferred by continuity of mass from these observed
horizontal flows have larger upflow amplitudes in cell centers than
downflow amplitudes at cell boundaries.
Title: First results on quiet and magnetic granulation from SOUP.
Authors: Title, A. M.; Tarbell, T. D.; Acton, L.; Duncan, D.; Ferguson,
S. H.; Finch, M.; Frank, Z.; Kelly, G.; Lindgren, R.; Morrill, M.
Bibcode: 1987NASCP2483...55T
Altcode: 1987tphr.conf...55T
The flight of Solar Optical Universal Polarimeter (SOUP) on Spacelab
2 allowed the collection of time sequences of diffraction limited (0.5
arc sec) granulation images with excellent pointing (0.003 arc sec) and
completely free of the distortion that plagues groundbased images. The
p-mode oscillations are clearly seen in the data. Using Fourier
transforms in the temporal and spatial domain, it was shown that the
p-modes dominate the autocorrelation lifetime in magnetic regions. When
these oscillations are removed the autocorrelation lifetime is found
to be 500 sec in quiet and 950 sec in magnetic regions. In quiet
areas exploding granules are seen to be common. It is speculated that
a significant fraction of granule lifetimes are terminated by nearby
explosions. Using local correlation tracking techniques it was able to
measure horizontal displacements, and thus transverse velocities, in
the magnetic field. In quiet sun it is possible to detect both super
and mesogranulation. Horizontal velocities are as great as 1000 m/s
and the average velocity is 400 m/s. In magnetic regions horizontal
velocities are much less, about 100 m/s.
Title: On the Relation between Magnetic Field Structures and
Granulation
Authors: Title, A. M.; Tarbell, T. D.; Topka, K. P.
Bibcode: 1987ApJ...317..892T
Altcode:
Narrow-band observations of a solar emerging-flux region, obtained
at 525.02 nm with resolution 0.5 arcsec using the Sacramento Peak
vacuum-tower telescope and the Spacelab 2 tunable filter on December
10, 1979, are reported. The data are presented in histograms and
characterized in detail. Magnetic-flux concentrations of 600-1000 G
are found to be located in areas of suppressed downflow near holes or
pores in the granulation pattern, while 100-500-G concentrations occur
in areas with stronger downdrafts, in cell-like structures of diameter
2-5 arcsec, the fields being aligned with dark intergranular lanes. It
is inferred that granulation concentrates the magnetic field in the
downflow lanes (as found in numerical simulations by Nordlund, 1983),
and that the magnetic structures are more diffuse and longer-lasting
than the bright spots; thus bright-point maps are contained in, rather
than equivalent to, magnetic-field maps.
Title: a Large Format Charge Coupled Device Camera for the NASA High
Resolution Solar Observatory
Authors: Morrill, M. E.; Duncan, D.; Title, A. M.; Wolfson, C. J.
Bibcode: 1987BAAS...19..927M
Altcode:
No abstract at ADS
Title: On the Relation Between Large-Scale Granular Flows and
Supergranules and Mesogranules
Authors: Simon, G.; Ferguson, S.; Tarbell, T.; Title, A.; Topka, K.;
November, L.; Zirin, H.
Bibcode: 1987BAAS...19R.935S
Altcode:
No abstract at ADS
Title: The Meridional Flow Inferred from the Shape of Large-scale
Magnetic Structures in the Photosphere
Authors: Hoeksema, J. T.; Herant, M.; Scherrer, P. H.; Title, A. M.
Bibcode: 1987BAAS...19S.935H
Altcode:
No abstract at ADS
Title: Simultaneous Observations of Emerging Flux from the Big Bear
Solar Observatory and the SOUP Instrument on Spacelab 2
Authors: Topka, K.; Ferguson, S.; Title, A.; Tarbell, T.; Zirin, H.;
Simon, G.; November, L.
Bibcode: 1987BAAS...19R.927T
Altcode:
No abstract at ADS
Title: On the Feasibility of Correlation Tracking at Moderate
Resolution
Authors: Bogart, R. S.; Scherrer, P. H.; Ferguson, S. H.; Tarbell,
T. D.; Title, A. M.
Bibcode: 1987BAAS...19..941B
Altcode:
No abstract at ADS
Title: Simultaneous Sunspot Observations from the SOUP Instrument
on Spacelab 2 and the Big Bear Solar Observatory
Authors: Shine, R. A.; Title, A. M.; Topka, K. P.; Tarbell, T. D.;
Zirin, H.
Bibcode: 1987BAAS...19..927S
Altcode:
No abstract at ADS
Title: The Correlation Tracker Image Stabilization System for HRSO
Authors: Edwards, C. G.; Levay, M.; Gilbreth, C. W.; Tarbell, T. D.;
Title, A. M.; Wolfson, C. J.; Torgerson, D. D.
Bibcode: 1987BAAS...19..929E
Altcode:
No abstract at ADS
Title: Ocean Waves in the Photosphere: Measurements of Oscillations
with Wavelengths of 1 - 10 Mm from SOUP White Light Images
Authors: Tarbell, T. D.; Shine, R. A.; Ferguson, S. H.; Title, A. M.;
Leibacher, J. W.
Bibcode: 1987BAAS...19Q.936T
Altcode:
No abstract at ADS
Title: Exploding and Elongated Granules
Authors: Title, A. M.; Tarbell, T. D.; Ferguson, S. H.; Topka, K. P.
Bibcode: 1987BAAS...19Q.927T
Altcode:
No abstract at ADS
Title: Is there a weak mixed polarity background field? Theoretical
arguments
Authors: Spruit, H. C.; Title, A. M.; van Ballegooijen, A. A.
Bibcode: 1987SoPh..110..115S
Altcode:
A number of processes associated with the formation of active regions
produce `U-loops': fluxtubes having two ends at the photosphere but
otherwise still embedded in the convection zone. The mass trapped on the
field lines of such loops makes them behave in a qualitative different
way from the `omega-loops' that form active regions. It is shown that
U-loops will disperse though the convection zone and form a weak (down
to a few gauss) field that covers a significant fraction of the solar
surface. This field is tentatively identified with the inner-network
fields observed at Kitt Peak and Big Bear. The process by which these
fields escape through the surface is described; a remarkable property is
that it can make active regions fields apparently disappear in situ. The
mixed polarity moving magnetic features near sunspots are interpreted
as a locally intense form of this disappearance by escape of U-loops.
Title: New Ideas About Granulation Based on Data from the Solar
Optical Universal Polarimeter Instrument on Spacelab 2 and Magnetic
Data from Big Bear Solar Observatory
Authors: Title, A. M.; Tarbell, T. D.; Topka, K. P.; Shine, R. A.;
Simon, G. W.; Zirin, H.; SOUP Team
Bibcode: 1987LNP...292..173T
Altcode: 1987ssp..conf..173T
The SOUP flow fields have been compared with carefully aligned
magnetograms taken at the BBSO before, during, and after the SOUP
images. The magnetic field is observed to exist in locations where
either the flow is convergent or on the boundaries of the outflow from
a flow cell center. Streamlines calculated from the flow field agree
very well with the observed motions of the magnetic field in the BBSO
magnetogram movies.
Title: Is there a weak mixed polarity background field? Theoretical
arguments.
Authors: Spruit, H. C.; Title, A. M.; van Ballegooijen, A. A.
Bibcode: 1987MPARp.271.....S
Altcode:
No abstract at ADS
Title: High resolution techniques at Lockheed Solar Observatory.
Authors: Title, A. M.; Peri, M. L.; Smithson, R. C.; Edwards, C. G.
Bibcode: 1987LFTR...28..107T
Altcode:
The authors have been doing simulations of adaptive optical
systems, developing correlation trackers, and developing linear PZT
actuators. The simulations have yielded the somewhat surprising result
that even when r0 is much smaller than the projected segment
size (spacing between actuators) the core of the point spread function
retains the full width at half maximum of the full aperture. In general
the point spread function consists of a diffraction limited shape plus
a broad halo, whose width is determined by r0. Unless the
segment size is on the order of r0, adaptive optics do not
significantly decrease the diameter of the circle which contains 50%
of the energy. A correlation tracker with a kilohertz control signal
has been successfully operated.
Title: Types of Magnetic Flux Emergence
Authors: Title, A.
Bibcode: 1987rfsm.conf..118T
Altcode:
A significant fraction of solar flux emerges from subsurface sources,
which have their own characteristic rotation rate and which last
years. The existence of these sources means that flux emergence
can not be studied as an isolated phenomena. Consideration must
be given to preexisting flux structures both above and below the
surface. Emergence, recombination, and submergence may not be treated
as separate processes. New very sensitive video magnetographs have
shown that there exists a weak component (1 to 40 gauss) of the solar
magnetic field. Perhaps this weak field component is a major factor
in the entire picture of flux emergence.
Title: Properties of Granulation from Filtered Movies of Spacelab
2 SOUP Images
Authors: Title, A. M.; Tarbell, T. D.
Bibcode: 1986BAAS...18Q.992T
Altcode:
No abstract at ADS
Title: Measurements of Transverse Flows in the Solar Photosphere
from Spacelab 2 SOUP Images
Authors: Tarbell, T. D.; Title, A. M.; Ferguson, S. H.; November,
L. J.; Simon, G. W.
Bibcode: 1986BAAS...18R.992T
Altcode:
No abstract at ADS
Title: High-Resolution Observations of Changing Magnetic Features
on the Sun
Authors: Topka, K. P.; Tarbell, T. D.; Title, A. M.
Bibcode: 1986ApJ...306..304T
Altcode:
The total magnetic flux present in 28 small isolated unipolar features
that surround an active region has been measured on a well-registered
sequence of high-resolution magnetograms. Seventeen features showed no
changes, but the rest showed changes in measured flux with time that
were much greater than the uncertainty in the flux determination. Two
magnetic features showed evidence for increases in flux with time,
while nine others showed decay. In some cases the decaying features
appear to be canceling with nearby opposite polarity flux, which may
represent the submergence of flux below the photosphere. In others,
the observed decay occurs in regions that are strictly unipolar,
with no observable opposite polarity flux present. Some evidence for
the outward diffusion of flux from a decaying feature in a unipolar
region was found.
Title: Results from the SOUP Experiment on Spacelab 2
Authors: Title, A. M.
Bibcode: 1986BAAS...18..673T
Altcode:
No abstract at ADS
Title: Measurements of the Lifetimes of Individual Granules from
SOUP Data
Authors: Title, A. M.; Tarbell, T. D.; SOUP Team
Bibcode: 1986BAAS...18Q.661T
Altcode:
No abstract at ADS
Title: Videodisk Movies of the Solar Photosphere from the SOUP
Instrument on Spacelab 2
Authors: Tarbell, T. D.; Title, A. M.; SOUP Team
Bibcode: 1986BAAS...18R.661T
Altcode:
No abstract at ADS
Title: Precise Proper Motion Measurement of Solar Granulation
Authors: November, L. J.; Simon, G. W.; Tarbell, T. D.; Title, A. M.
Bibcode: 1986BAAS...18..665N
Altcode:
No abstract at ADS
Title: White-light movies of the solar photosphere from the soup
instrument on spacelab 2
Authors: Title, A. M.; Tarbell, T. D.; Simon, G. W.; Acton, L.;
Duncan, D.; Ferguson, S.; Finch, M.; Frank, Z.; Kelly, G.; Lindgren,
R.; Morrill, M.; Pope, T.; Reeves, R.; Rehse, R.; Shine, R.; Topka,
K.; Harvey, J.; Leibacher, J.; Livingston, W.; November, L.
Bibcode: 1986AdSpR...6h.253T
Altcode: 1986AdSpR...6..253T
We present initial results on solar granulation, pores and sunspots
from the white-light films obtained by the Solar Optical Universal
Polarimeter (SOUP) instrument on Spacelab 2. SOUP contains a
30-cm Cassegrain telescope, an active secondary mirror for image
stabilization, and a white-light optical system with 35-mm film
and video cameras. Outputs from the fine guidance servo provided
engineering data on the performance of the ESA Instrument Pointing
System (IPS). Several hours of movies were taken at various
disk and limb positions in quiet and active regions. The images
are diffraction-limited at 0.5 arc second resolution and are, of
course, free of atmospheric seeing and distortion. Properties of the
granulation in magnetic and non-magnetic regions are compared and are
found to differ significantly in size, rate of intensity variation,
and lifetime. In quiet sun on the order of fifty percent of the area
has at least one ``exploding granule'' occurring in it during a 25
minute period. Local correlation tracking has detected several types
of transverse flows, including systematic outflow from the penumbral
boundary of a spot, motion of penumbral filaments, and cellular flow
patterns of supergranular and mesogranular size. Feature tracking has
shown that in quiet sun the average granule fragment has a velocity
of about one kilometer per second.
Title: An Initial Study of Granulation Using Data from the SOUP
Instrument on SpaceLab 2
Authors: Tarbell, T. D.; Title, A. M.; SOUP Team
Bibcode: 1985BAAS...17..833T
Altcode:
No abstract at ADS
Title: A High Quality Movie from the SOUP Instrument on SpaceLab 2
Authors: Title, A. M.; Tarbell, T. D.; SOUP Team
Bibcode: 1985BAAS...17..896T
Altcode:
No abstract at ADS
Title: Soup White Light Images
Authors: Title, A.
Bibcode: 1985tphr.conf...28T
Altcode:
No abstract at ADS
Title: Granules and Magnetic Field Observations
Authors: Title, A.
Bibcode: 1985tphr.conf..124T
Altcode:
No abstract at ADS
Title: Scientific Observing Plans for the SOUP Instrument on Spacelab
2 in July, 1985
Authors: Tarbell, T. D.; Finch, M. L.; Title, A. M.
Bibcode: 1985BAAS...17..641T
Altcode:
No abstract at ADS
Title: SOUP white light images.
Authors: Title, A. M.
Bibcode: 1985MPARp.212...28T
Altcode:
No abstract at ADS
Title: High Resolution Solar Observations
Authors: Title, A.
Bibcode: 1985LNP...233...51T
Altcode: 1985hrsp.proc...51T
Traditionally the way to get high quality images has been to find a good
seeing site and establish a high quality observatory. It now appears
that this procedure can be improved by installing active mirrors which
correct real time wavefront tilt, and adaptive mirrors which correct,
at least for a limited field of view, wavefront distortions introduced
by the atmosphere. Space telescopes offer the further advantage of
completely eliminating the blurring and distortions introduced by
the atmosphere. Further space operations offer the possibility of
uninterrupted observing sequences of many days or weeks.
Title: Formation of an international program for solar astrophysics
(IPSA).
Authors: Title, A.; Schmidt, H. U.
Bibcode: 1985MPARp.212..338T
Altcode:
Following the workshops a SOT co-investigator's meeting was held at
the Max-Planck-Institut für Astrophysik in Garching. Directions for
future theoretical work in preparation for SOT were formulated in five
study groups. It was felt by the participants of these groups that an
organizational basis for this work was needed and the formation of an
international program for solar astrophysics agreed upon.
Title: Granules and magnetic field observations.
Authors: Title, A. M.
Bibcode: 1985MPARp.212..124T
Altcode:
No abstract at ADS
Title: Magnetic Fields, Downdrafts, and Granulation in the Solar
Photosphere
Authors: Title, A. M.; Tarbell, T. D.
Bibcode: 1984BAAS...16.1001T
Altcode:
No abstract at ADS
Title: Observations of the Decay of a Small Sunspot
Authors: Title, Alan M.; Topka, Ken P.
Bibcode: 1984BAAS...16R.408T
Altcode:
No abstract at ADS
Title: The Solar Optical Universal Polarimeter
Authors: Finch, Mike L.; Tarbell, Ted D.; Title, Alan M.
Bibcode: 1984BAAS...16..404F
Altcode:
No abstract at ADS
Title: The SOUP and CIP instruments
Authors: Title, A.
Bibcode: 1984AdSpR...4h..67T
Altcode: 1984AdSpR...4R..67T
Solar physics is about to undergo a revolution in the amount and quality
of undistorted high resolution filter-grams and spectra available for
study. Spacelab 2 will obtain UV and visible data comparable to the best
obtained on Earth, but free of both blurring and image distortion. The
goals of the Spacelab 2 flight are to collect data on the evolution
of the solar magnetic and velocity fields on time scales of seconds
to days. In the first part of the next decade, the 1.3 meter aperture
Solar Optical Telescope will have sufficient spatial resolution to
collect data on the scale of the solar density scale height [~ 100 km]
which should be sufficient to study the basic physical processes in
the solar atmosphere.
Title: The Coordinated Instrument Package for the Solar Optical
Telescope
Authors: Wolfson, C. J.; Tarbell, T. D.; Topka, K. P.; Title, A. M.
Bibcode: 1983BAAS...15R.718W
Altcode:
No abstract at ADS
Title: The Coordinated Instrument Package (CIP)
Authors: Title, A. M.; Torgerson, D. D.
Bibcode: 1983BAAS...15S.709T
Altcode:
No abstract at ADS
Title: Fine Structure in the Solar Magnetic Field
Authors: Tarbell, T. D.; Title, A. M.
Bibcode: 1982BAAS...14..924T
Altcode:
No abstract at ADS
Title: Low noise imaging photon counter for astronomy
Authors: Mertz, Lawrence N.; Tarbell, Theodore D.; Title, Alan M.
Bibcode: 1982ApOpt..21..628M
Altcode:
No abstract at ADS
Title: Variations of Birefringent Filters for Solar and Stellar
Applications
Authors: Title, A.; Rosenberg, W.
Bibcode: 1981siwn.conf..326T
Altcode:
No abstract at ADS
Title: The Compact Magnetograph: Preliminary Results
Authors: Gillespie, B. A.; Title, A. M.
Bibcode: 1981BAAS...13R.888G
Altcode:
No abstract at ADS
Title: Image Photon Counting System
Authors: Mertz, L.; Title, A.; Tarbell, T. D.
Bibcode: 1981BAAS...13..840M
Altcode:
No abstract at ADS
Title: A Simple Image Motion Compensation System for Solar
Observations
Authors: Smithson, R. C.; Tarbell, T. D.; Title, A. M.
Bibcode: 1980BAAS...12..915S
Altcode:
No abstract at ADS
Title: Status of the Spacelab 2 Solar Optical Universal Polarimeter
(SOUP)
Authors: Tarbell, T. D.; Finch, M. L.; Ramsey, H. E.; Schoolman,
S. A.; Title, A. M.
Bibcode: 1980BAAS...12..915T
Altcode:
No abstract at ADS
Title: Narrow Band Wide Field Filters for 1500 - 3000 Å Wavelengths
Authors: Rosenberg, W. J.; Title, A. M.
Bibcode: 1980BAAS...12..915R
Altcode:
No abstract at ADS
Title: Improvements in birefringent filters. 6: Analog birefringent
elements
Authors: Title, Alan M.; Ramsey, H. E.
Bibcode: 1980ApOpt..19.2046T
Altcode:
No abstract at ADS
Title: Using Tunable Filters for Two-Dimensional Solar Spectroscopy
Authors: Ramsey, H. B.; Schoolman, S. A.; Smithson, R. C.; Tarbell,
T. D.; Title, A. M.
Bibcode: 1979BAAS...11..640R
Altcode:
No abstract at ADS
Title: In search of the perfect magnetogram.
Authors: Ramsey, H. E.; Schoolman, S. A.; Smithson, R. C.; Tarbell,
T. D.; Title, A. M.
Bibcode: 1979BAAS...11..611R
Altcode:
No abstract at ADS
Title: Weak and strong magnetic fields in the solar photosphere.
Authors: Tarbell, T. D.; Title, A. M.; Schoolman, S. A.
Bibcode: 1979ApJ...229..387T
Altcode:
Very high-resolution (0.5 arcsec) magnetograms of the quiet sun
and a plage are discussed which were obtained by using a tunable
birefringent filter in Fe I 6302A. A search for a turbulent bipolar
field with the use of co-added and spatially filtered frames is
unsuccessful. Statistical analysis sets an upper limit of 50 gauss on
the rms vertical component of such a field and probably rules out the
possibility of field strengths exceeding 100 gauss in the inner network
field observed at Kitt Peak. The area, total flux, and energy content
of the strong (kilogauss) network fields are measured and compared with
the upper limits for these properties of a hypothetical widespread
weak field. In the quiet photosphere, a weak background field may
contain interesting amounts of flux and energy, but the strong fields
are dominant at higher levels and in the plage. The total magnetic
energy in the quiet photospheric is roughly equal to the kinetic
energy of granular and oscillatory velocities at the same level. By
flux conservation, field strengths in the transition region are greater
than 25 gauss in the quiet network and 100 gauss in the plage.
Title: Research on spectroscopic imaging. Volume 2: Reference
literature
Authors: Title, A.; Rosenberg, W.
Bibcode: 1979rsi.....2.....T
Altcode:
Translations of scientific papers on birefringent filters by Lyot
and Solc are presented along with the texts of 15 recent treaties on
filter techniques.
Title: Magnetic field measurements from the solar probe
Authors: Title, A. M.
Bibcode: 1978clus.nasa..155T
Altcode:
An optical system for the solar probe is described as well as its
capability for improvements in spatial resolution. A magnetograph
for measuring the elementary flux tube and obtaining vector geometry
field geometry offers the possibility of looking for low contrast weak
structure. With the probe's orbit passing over the pole, the structure
of the polar field can be directly measured. The detector plane of the
system receives a telecentric image of the objective. Because there is
an aperture in this focal plane that can both move and change size,
polarized line profiles can be obtained at arbitrary points with
variable spatial resolution. The telescope microprocessor searches
for the magnetic elements and then constructs the vector field.
Title: Tunable filters for spaceflight.
Authors: Title, A. M.
Bibcode: 1978JOSA...68Q1431T
Altcode: 1978OSAJ...68Q1431T
No abstract at ADS
Title: Solar magnetic fields study
Authors: Smithson, R. C.; Title, A. M.
Bibcode: 1977lock.reptQ....S
Altcode:
High resolution observations of quiet sun magnetic fields have been
made at Sacramento Peak Observatory using the Lockheed Universal
Filter. The existence of 'salt and pepper' fields described by other
observers has been called into question.
Title: On the size, structure, and strength of the small-scale solar
magnetic field.
Authors: Ramsey, H. E.; Schoolman, S. A.; Title, A. M.
Bibcode: 1977ApJ...215L..41R
Altcode:
High-resolution magnetograms place an upper limit of 0.33 arcsec on
the smallest magnetic-field structures. These magnetograms show that
the active-region field is organized into roughly cellular patterns 2-3
arcsec in diameter and that the field structures occur in the centers of
'abnormal' granules. Comparison of these data and other magnetograms
with high signal-to-noise ratio indicates that there exists another
component of the field that is diffuse on the scale of an arc second
and has a maximum strength of less than 500 gauss.
Title: Measurements of magnetic fluxes and field strengths in the
photospheric network.
Authors: Tarbell, T. D.; Title, A. M.
Bibcode: 1977SoPh...52...13T
Altcode:
We present digital pictures of an active region network cell in five
quantities, measured simultaneously: continuum intensity, line-center
intensity, equivalent width, magnetogram signal, and magnetic field
strength. These maps are derived from computer analysis of circularly
polarized line profiles of FeI λ 5250.2; spectral and spatial
resolution are 1/40 Å and 1.5″, respectively. Measured Zeeman
splittings show the existence of strong magnetic fields (1000-1800 G)
at nearly all points with a magnetogram signal exceeding 125 G. The
mean and rms deviation of the field strengths change by less than
20% over a factor-of-four range of fluxes. From the significant
disparity between measured fluxes and field strengths, we conclude
that large flux patches (up to 4″ across) consist of closely-packed
unresolved filaments. The smallest filaments must be less than 0.7″
in diameter. We also observe the dark component of the photospheric
network, which appears to contain sizable transverse fields.
Title: The Lockheed Universal Filter.
Authors: Title, A. M.; Ramsey, H. E.; Schoolman, S. A.
Bibcode: 1976BAAS....8R.535T
Altcode:
No abstract at ADS
Title: Magnetic Field Strengths in Photospheric Filaments.
Authors: Tarbell, T. D.; Title, A. M.
Bibcode: 1976BAAS....8..501T
Altcode:
No abstract at ADS
Title: The Fine Scale Magnetic Structure of Plages.
Authors: Schoolman, S. A.; Title, A. M.; Ramsey, H. E.
Bibcode: 1976BAAS....8..500S
Altcode:
No abstract at ADS
Title: Measurements of solar magnetic fields by Fourier transform
techniques. II. Saturated and blended lines.
Authors: Tarbell, T. D.; Title, A. M.
Bibcode: 1976SoPh...47..563T
Altcode:
The Fourier techniques of Paper I have been exhaustively calibrated
using Unno's results for the absorption profile of a simple Zeeman
triplet. If a simple transformation is applied to the normalized line
depths, then magnetic field strengths and inclination angles can be
measured very accurately from noisy, saturated line profiles. Systematic
errors caused by saturation effects can be estimated and reduced by
varying one parameter. When a significant fraction of the line profile
is unsplit and unpolarized, large errors may be made in measurements
of low fields, unless the line is sufficiently weak. For a weak line,
a vertical field of 1600 gauss can be measured to 10% accuracy even
when 70% of the line profile is stray light. These stray light
errors are troublesome in measuring fields of gaps and pores but
not sunspots. Numerical results of our error analysis are presented
graphically.
Title: Total reduction of distorted echelle spectrograms: an
automatic procedure
Authors: Peterson, R. C.; Title, A. M.
Bibcode: 1975ApOpt..14.2527P
Altcode:
A total reduction procedure, notable for its use of a
computer-controlled microdensitometer for semi-automatically tracing
curved spectra, is applied to distorted high-dispersion echelle
spectra recorded by an image tube. Microdensitometer specifications are
presented and the FORTRAN, TRACEN and SPOTS programs are outlined. The
intensity spectrum of the photographic or electrographic plate is
plotted on a graphic display. The time requirements are discussed
in detail.
Title: The Temporal and Spatial Extent of the Isoplanatic Patch.
Authors: Title, A.; Pope, T.; Schoolman, S.
Bibcode: 1975BAAS....7..462T
Altcode:
No abstract at ADS
Title: High Resolution Observations of Photospheric Network Magnetic
Fields.
Authors: Tarbell, T. D.; Title, A. M.
Bibcode: 1975BAAS....7..459T
Altcode:
No abstract at ADS
Title: Measurement of Solar Magnetic Fields by Fourier Transform
Techniques. I: Unsaturated Lines
Authors: Title, A. M.; Tarbell, T. D.
Bibcode: 1975SoPh...41..255T
Altcode:
If the basic profile shapes of the normal Zeeman triplet do not have
zeros in their Fourier transform, the magnetic field splitting can
be determined independent of the profile shape. When the ratio of
the splitting of the components is greater than the intrinsic FWHM
of the component profiles the magnetic splitting can be determined
with significantly greater accuracy than the measurement accuracy of
the original profile. For Gaussian shaped components and a ratio of
magnetic splitting to FWHM of 1.5 the noise reduction factor is 25.
Title: Measurement of Magnetic Fields Using Fourier Transform
Techniques
Authors: Title, A. M.
Bibcode: 1975BAAS....7R.350T
Altcode:
No abstract at ADS
Title: Improvement of birefringent filters. 3: Effect of errors on
wide field elements
Authors: Title, A. M.
Bibcode: 1975ApOpt..14..445T
Altcode:
The properties of nontunable and tunable Lyot wide-field elements are
examined when the components of the elements deviate from their proper
values. Special emphasis is put on determining what variations cause
light to be transmitted at the transmission minima. The analysis shows
that the nine- and ten-element plastic waveplates described in Paper
II of this series can be used to make a Lyot filter that is tunable
from 3500 A to 10,000 A.
Title: Drift in interference filters. 2: Radiation effects.
Authors: Title, A. M.
Bibcode: 1974ApOpt..13.2680T
Altcode:
Studies of peak transmission drift in narrow-band interference
filters have shown that there exist two mechanisms that cause drift
toward shorter wavelengths. One is dependent on the thermal history
of the filter and is discussed in Part 1 of this paper. The other is
dependent on the exposure of the filter to radiation. For ZnS-cryolite
filters of particular design, it is experimentally demonstrated that
the filters are most sensitive to radiation in a 100-A band centered
at approximately 3900 A. The drift rate in the focal plane of an f/20
solar image is approximately 3 A/100 hr of exposure. Further, it is
also shown by model calculations that the observed radiation-induced
drift is consistent with the hypothesis that the optical thickness of
ZnS decreases in proportion to the radiant energy absorbed.
Title: Drift in interference filters. Part I.
Authors: Title, A. M.; Pope, T. P.; Andelin, J. P., Jr.
Bibcode: 1974ApOpt..13.2675T
Altcode:
Studies of narrow-band interference filters have shown that two
mechanisms exist that cause drift to shorter wavelengths. One is
dependent on the thermal history of the filter, and the other depends on
the radiation history. The present paper presents experimental results
on thermal effects; and it is shown that by a proper bake cycle,
ZnS-cryolite filters are stable for years if stored at less than 38 C.
Title: Partial Polaroids in Birefringent Filters
Authors: Title, A. M.
Bibcode: 1974SoPh...38..523T
Altcode:
It is demonstrated that a single partial polaroid in a Lyot filter
behaves in much the same manner as a contrast element. Use of a partial
polaroid with a transmission ratio of 10 to 1 results in a factor of
10 decrease in the principal secondary maxima. An explanation of the
effect of the partial polaroids is presented in terms of the pulse
response of the birefringent network.
Title: Effective Index of Calcite and Quartz
Authors: Title, A. M.
Bibcode: 1974SoPh...39..505T
Altcode:
The thickness of calcite or quartz required for an element of a
given half width (FWHM) depends not only on the wavelength and index
difference of the birefringent material, but also the first derivative
of the index difference with wavelength. For calcite, the effective
index difference can differ by as much as 50% from published values.
Title: Sensitivity Variations of Silicon Vidicons
Authors: Title, Alan M.
Bibcode: 1974SoPh...35..233T
Altcode:
Local peak to peak sensitivity fluctuations of Si vidicon targets that
can exceed 100% in the red have been observed. These fluctuations are
due to Fabry-Pérot interference in the target.
Title: Improvement of Birefringent Filters
Authors: Title, Alan M.
Bibcode: 1974BAAS....6T.295T
Altcode:
No abstract at ADS
Title: Drift in Interference Filters
Authors: Title, Alan M.; Pope, Thomas P.
Bibcode: 1974BAAS....6U.295T
Altcode:
No abstract at ADS
Title: Spectral characteristics of flares.
Authors: Schoolman, S.; Title, A.
Bibcode: 1974sowi.conf..147S
Altcode:
A technique is presented for obtaining H-alpha spectral profiles of
solar flares. A multislit spectrograph, which can take spectra every
15 seconds, is described along with a data reduction method utilizing a
very fast microdensometer and a computer. The technique is illustrated
with a spectral analysis of the solar flare of September 5, 1973.
Title: Improvement of Birefringent Filters. I: Reduction of Scatter
in Polaroid Materials
Authors: Title, Alan M.
Bibcode: 1973SoPh...33..521T
Altcode:
No abstract at ADS
Title: Sensitivity Variations of Silicon Vidicon in the Red Region
of The Spectrum.
Authors: Title, A.
Bibcode: 1973BAAS....5..390T
Altcode:
No abstract at ADS
Title: Lyot Filters with Partial Polaroids
Authors: Title, Alan M.
Bibcode: 1973BAAS....5S.281T
Altcode:
No abstract at ADS
Title: Hα Chromospheric Oscillations above Sunspot Umbrae
Authors: Phillis, Gary L.; Ramsey, Harry E.; Title, Alan M.
Bibcode: 1973BAAS....5R.278P
Altcode:
No abstract at ADS
Title: Methods for Measurement of High Fields
Authors: Title, A. M.
Bibcode: 1972BAAS....4Q.394T
Altcode:
No abstract at ADS
Title: A new kind of interference filter.
Authors: Title, A. M.
Bibcode: 1971BAAS....3Q.264T
Altcode:
No abstract at ADS
Title: Spectra-Spectroheliograph Observations
Authors: Title, A. M.; Andelin, J. P., Jr.
Bibcode: 1971IAUS...43..298T
Altcode:
No abstract at ADS
Title: FABRY-PéROT Interferometers as Narrow and Optical Filters
Authors: Title, A. M.
Bibcode: 1971IAUS...41..325T
Altcode:
No abstract at ADS
Title: Spectraspectroheliograph Observations
Authors: Andelin, John; Title, Alan
Bibcode: 1970BAAS....2R.291A
Altcode:
No abstract at ADS
Title: Initial Results of the Spectra-Spectroheliograph System.
Authors: Title, Alan
Bibcode: 1968AJS....73R..80T
Altcode:
A high-speed framing camera mounted on the Sacramento Peak Universal
Spectrograph has been used to take sequences of spectra while the
solar image was stepped across the entrance slit. Spectroheliograms
and velocity spectroheliograms have been constructed from these
spectra. Preliminary analysis of an Ha series has shown the existence
of a region near a spot that was 10 X 30 sec of arc in extent that
exhibits a steady downward flow of 60 km/sec for the length of the
observing 40 min. During part of the time the region also flowed upward
at 70 to 90 km/sec. The line shapes from the high-speed regions except
for their displacement, are normal absorbing profiles that are not
significantly broadened. Comparison of the high-velocity grams and
spectroheliograms constructed at line center show the velocity field
pattern similar in shape to a bright region in the line center, but
shifted by 6 sec of arc. Observations have also been made in Ca+K,
but they have not yet been analyzed.
Title: Velocity fields in the Solar atmosphere
Authors: Title, A.
Bibcode: 1967AJ.....72R.323T
Altcode:
No abstract at ADS
Title: A Study of Velocity Fields in the Hydrogen-Alpha Chromosphere
by Means of Time-Lapse Doppler Movies.
Authors: Title, Alan Morton
Bibcode: 1966PhDT.........1T
Altcode:
No abstract at ADS