explanation blue bibcodes open ADS page with paths to full text
Author name code: mckenzie
ADS astronomy entries on 2022-09-14
author:"McKenzie, David Eugene"
---------------------------------------------------------
Title: Quiet Sun Center to Limb Variation of the Linear Polarization
Observed by CLASP2 Across the Mg II h and k Lines
Authors: Rachmeler, L. A.; Bueno, J. Trujillo; McKenzie, D. E.;
Ishikawa, R.; Auchère, F.; Kobayashi, K.; Kano, R.; Okamoto,
T. J.; Bethge, C. W.; Song, D.; Ballester, E. Alsina; Belluzzi,
L.; Pino Alemán, T. del; Ramos, A. Asensio; Yoshida, M.; Shimizu,
T.; Winebarger, A.; Kobelski, A. R.; Vigil, G. D.; Pontieu, B. De;
Narukage, N.; Kubo, M.; Sakao, T.; Hara, H.; Suematsu, Y.; Štěpán,
J.; Carlsson, M.; Leenaarts, J.
2022ApJ...936...67R Altcode: 2022arXiv220701788R
The CLASP2 (Chromospheric LAyer Spectro-Polarimeter 2) sounding rocket
mission was launched on 2019 April 11. CLASP2 measured the four Stokes
parameters of the Mg II h and k spectral region around 2800 Å along a
200″ slit at three locations on the solar disk, achieving the first
spatially and spectrally resolved observations of the solar polarization
in this near-ultraviolet region. The focus of the work presented here
is the center-to-limb variation of the linear polarization across these
resonance lines, which is produced by the scattering of anisotropic
radiation in the solar atmosphere. The linear polarization signals of
the Mg II h and k lines are sensitive to the magnetic field from the
low to the upper chromosphere through the Hanle and magneto-optical
effects. We compare the observations to theoretical predictions
from radiative transfer calculations in unmagnetized semiempirical
models, arguing that magnetic fields and horizontal inhomogeneities
are needed to explain the observed polarization signals and spatial
variations. This comparison is an important step in both validating and
refining our understanding of the physical origin of these polarization
signatures, and also in paving the way toward future space telescopes
for probing the magnetic fields of the solar upper atmosphere via
ultraviolet spectropolarimetry.
---------------------------------------------------------
Title: Parallel Plasma Loops and the Energization of the Solar Corona
Authors: Peter, Hardi; Chitta, Lakshmi Pradeep; Chen, Feng; Pontin,
David I.; Winebarger, Amy R.; Golub, Leon; Savage, Sabrina L.;
Rachmeler, Laurel A.; Kobayashi, Ken; Brooks, David H.; Cirtain,
Jonathan W.; De Pontieu, Bart; McKenzie, David E.; Morton, Richard J.;
Testa, Paola; Tiwari, Sanjiv K.; Walsh, Robert W.; Warren, Harry P.
2022ApJ...933..153P Altcode: 2022arXiv220515919P
The outer atmosphere of the Sun is composed of plasma heated to
temperatures well in excess of the visible surface. We investigate
short cool and warm (<1 MK) loops seen in the core of an active
region to address the role of field-line braiding in energizing these
structures. We report observations from the High-resolution Coronal
imager (Hi-C) that have been acquired in a coordinated campaign with
the Interface Region Imaging Spectrograph (IRIS). In the core of the
active region, the 172 Å band of Hi-C and the 1400 Å channel of IRIS
show plasma loops at different temperatures that run in parallel. There
is a small but detectable spatial offset of less than 1″ between
the loops seen in the two bands. Most importantly, we do not see
observational signatures that these loops might be twisted around each
other. Considering the scenario of magnetic braiding, our observations
of parallel loops imply that the stresses put into the magnetic field
have to relax while the braiding is applied: the magnetic field never
reaches a highly braided state on these length scales comparable to
the separation of the loops. This supports recent numerical 3D models
of loop braiding in which the effective dissipation is sufficiently
large that it keeps the magnetic field from getting highly twisted
within a loop.
---------------------------------------------------------
Title: Realizing Comprehensive 3D Observations to Probe Magnetic
Energy Storage and Release in the Corona
Authors: Caspi, A.; Seaton, D. B.; Casini, R.; Downs, C.; Gibson, S.;
Gilbert, H.; Glesener, L.; Guidoni, S.; Hughes, J. M.; McKenzie, D.;
Reeves, K.; Saint-Hilaire, P.; Shih, A. Y.; West, M.
2022heli.conf.4058C Altcode:
Understanding impulsive energy release in the solar corona requires
knowledge of the 3D coronal magnetic field and 3D signatures of
energy release through systematic multi-viewpoint observations, in
many wavelengths, including coronal magnetometry.
---------------------------------------------------------
Title: Space-Based UV Spectropolarimetry for Chromospheric Magnetic
Field Measurements
Authors: McKenzie, D. E.
2022heli.conf.4051M Altcode:
Quantitative measurements of the chromospheric magnetic field is
essential for a predictive understanding of the energy budget of the
upper solar atmosphere. UV spectropolarimetry provides a means for
making these measurements.
---------------------------------------------------------
Title: New Approaches to Integrated Mission, Data, and Modeling
Frameworks
Authors: Seaton, D. B.; Caspi, A.; Casini, R.; Downs, C.; Gibson, S.;
Gilbert, H.; Glesener, L.; Guidoni, S.; Hughes, J. M.; McKenzie, D.;
Reeves, K.; Saint-Hilaire, P.; Shih, A.; West, M.
2022heli.conf.4057S Altcode:
A new generation of heliophysics missions will require integration of
data from multiple missions with analysis tools and physics-based
models. We discuss strategies to develop a framework for
systems-integrated data and analysis environments.
---------------------------------------------------------
Title: Extreme-ultraviolet Stellar Characterization for Atmospheric
Physics and Evolution mission: motivation and overview
Authors: France, Kevin; Fleming, Brian; Youngblood, Allison; Mason,
James; Drake, Jeremy J.; Amerstorfer, Ute V.; Barstow, Martin;
Bourrier, Vincent; Champey, Patrick; Fossati, Luca; Froning, Cynthia
S.; Green, James C.; Grisé, Fabien; Gronoff, Guillaume; Hellickson,
Timothy; Jin, Meng; Koskinen, Tommi T.; Kowalski, Adam F.; Kruczek,
Nicholas; Linsky, Jeffrey L.; Lipscy, Sarah J.; McEntaffer, Randall
L.; McKenzie, David E.; Miles, Drew M.; Patton, Tom; Savage, Sabrina;
Siegmund, Oswald; Spittler, Constance; Unruh, Bryce W.; Volz, Máire
2022JATIS...8a4006F Altcode: 2022arXiv220113219F
The Extreme-ultraviolet Stellar Characterization for Atmospheric
Physics and Evolution (ESCAPE) mission is an astrophysics Small
Explorer employing ultraviolet spectroscopy (EUV: 80 to 825 Å and FUV:
1280 to 1650 Å) to explore the high-energy radiation environment
in the habitable zones around nearby stars. ESCAPE provides the
first comprehensive study of the stellar EUV and coronal mass
ejection environments that directly impact the habitability of rocky
exoplanets. In a 20-month science mission, ESCAPE will provide the
essential stellar characterization to identify exoplanetary systems
most conducive to habitability and provide a roadmap for NASA's
future life-finder missions. ESCAPE accomplishes this goal with
roughly two-order-of-magnitude gains in EUV efficiency over previous
missions. ESCAPE employs a grazing incidence telescope that feeds an
EUV and FUV spectrograph. The ESCAPE science instrument builds on
previous ultraviolet and x-ray instrumentation, grazing incidence
optical systems, and photon-counting ultraviolet detectors used on
NASA astrophysics, heliophysics, and planetary science missions. The
ESCAPE spacecraft bus is the versatile and high-heritage Ball Aerospace
BCP-Small spacecraft. Data archives will be housed at the Mikulski
Archive for Space Telescopes.
---------------------------------------------------------
Title: Demonstration of Chromospheric Magnetic Mapping with CLASP2.1
Authors: McKenzie, David; Ishikawa, Ryohko; Trujillo Bueno, Javier;
Auchere, F.; Kobayashi, Ken; Winebarger, Amy; Kano, Ryouhei; Song,
Donguk; Okamoto, Joten; Rachmeler, Laurel; De Pontieu, Bart; Vigil,
Genevieve; Belluzzi, Luca; Alsina Ballester, Ernest; del Pino Aleman,
Tanausu; Bethge, Christian; Sakao, Taro; Stepan, Jiri
2021AGUFMSH52A..06M Altcode:
Probing the magnetic nature of the Suns atmosphere requires measurement
of the Stokes I, Q, U and V profiles of relevant spectral lines (of
which Q, U and V encode the magnetic field information). Many of the
magnetically sensitive lines formed in the chromosphere and transition
region are in the ultraviolet spectrum, necessitating observations
above the absorbing terrestrial atmosphere. The Chromospheric
Layer Spectro-Polarimeter (CLASP2) sounding rocket was flown
successfully in April 2019, as a follow-on to the successful flight in
September 2015 of the Chromospheric Lyman-Alpha Spectro-Polarimeter
(CLASP). Both projects were funded by NASAs Heliophysics Technology
and Instrument Development for Science (H-TIDeS) program to develop
and test a technique for observing the Sun in ultraviolet light,
and for quantifying the polarization of that light. By demonstrating
successful measurement and interpretation of the polarization in
hydrogen Lyman-alpha and the Mg II h and k spectral lines, the CLASP
and CLASP2 missions are vital first steps towards routine quantitative
characterization of the local thermal and magnetic conditions in the
solar chromosphere. In October of 2021, we re-flew the CLASP2 payload
with a modified observing program to further demonstrate the maturity
of the UV spectropolarimetry techniques, and readiness for development
into a satellite observatory. During the reflight, called CLASP2.1,
the spectrograph slit was scanned across an active region plage to
acquire a two-dimensional map of Stokes V/I, to demonstrate the ability
of UV spectropolarimetry to yield chromospheric magnetic fields over
a large area. This presentation will display preliminary results from
the flight of CLASP2.1.
---------------------------------------------------------
Title: Preliminary Results from the Marshall Grazing Incidence X-ray
Spectrometer (MaGIXS)
Authors: Winebarger, Amy; Savage, Sabrina; Kobayashi, Ken; Champey,
Patrick; Golub, Leon; Walsh, Robert; Athiray, P. S.; Bradshaw, Stephen;
Cheimets, Peter; Cirtain, Jonathan; DeLuca, Edward; Del Zanna, Giulio;
Mason, Helen; McKenzie, David; Ramsey, Brian; Reeves, Katharine;
Testa, Paola; Vigil, Genevieve; Warren, Harry
2021AGUFMSH51A..06W Altcode:
Coronal heating mechanisms are notoriously difficult to constrain with
current observations. We present new observations from an instrument
designed to measure a critical diagnostic of the frequency heating
events in active regions. The Marshall Grazing Incidence X-ray
Spectrometer (MaGIXS) is a sounding rocket mission that aims to
observe the soft x-ray solar spectrum (0.6 2.5 nm) with both spatial
and spectral resolution. This wavelength range has several high
temperature and abundance diagnostics that can be used to infer the
coronal heating frequency. MaGIXS will observe the Sun through a 12
x 33 slot, producing “overlappograms, where the spatial and spectral
information are overlapped and must be unfolded. In this presentation,
I will report on the MaGIXS launch and data collection and provide
preliminary analysis of MaGIXS observations.
---------------------------------------------------------
Title: Opto-mechanical design of the ESCAPE Small Explorer: an EUV
spectrograph for exoplanet host star irradiance and CME activity
Authors: Fleming, Brian T.; France, Kevin; Hellickson, Timothy;
Patton, Tom; Unruh, Bryce; Kruczek, Nicholas; McKenzie, David;
Champey, Patrick; Cheimets, Peter; Hertz, Edward; Romaine, Suzanne;
McEntaffer, Randall; Grisé, Fabien; Miles, Drew; Siegmund, Oswald;
McPhate, Jason; Green, James; Beasley, Matthew
2021SPIE11821E..04F Altcode:
The University of Colorado led Extreme-ultraviolet Stellar
Characterization for Atmospheric Physics and Evolution (ESCAPE)
small explorer mission concept is designed to measure the extreme-
and far-ultraviolet (EUV; 80 - 560 A, 600 - 825 A, FUV; 1280 - 1650
A) irradiance and are activity of exoplanet host stars; essential
measurements for assessing the stability of rocky planet atmospheres
in the liquid-water habitable zone. The ESCAPE design consists of a
fixed optical configuration with a grazing incidence Gregorian, or
"Hetterick- Bowyer", telescope feeding grazing and normal incidence
spectroscopic channels. The telescope is provided by a joint NASA
Marshall Space Flight Center and Smithsonian Astrophysics Observatory
team. The grazing incidence gratings have a radial profile and are
ruled into single-crystal silicon using electron-beam lithography in
the nanofabrication laboratory at Pennsylvania State University. Normal
incidence gratings have aberration correcting holographic solutions
and are supplied by Horiba Jobin Yvon. Spectra are imaged onto a curved
microchannel plate detector supplied by the University of California,
Berkeley. ESCAPE utilizes the Ball Aerospace BCP spacecraft. The
simple, fixed configuration design of ESCAPE is projected to exceed
the effective area of the last major EUV astrophysics spectrograph,
EUV E-DS/S, by more than a factor of 50, providing unprecedented
sensitivity in this essential bandpass for exoplanet host-star
characterization. We report on the ESCAPE design, projected performance
and mission implementation plan, as well as the trade studies carried
out over Phase A to scope the first NASA EUV astrophysics mission in
nearly 30 years. If selected, ESCAPE will launch in Fall 2025.
---------------------------------------------------------
Title: Thermodynamic Evolution of Solar Flare Supra-arcade Downflows
Authors: Li, Z. F.; Cheng, X.; Ding, M. D.; Reeves, Katharine K.;
Kittrell, DeOndre; Weber, Mark; McKenzie, David E.
2021ApJ...915..124L Altcode: 2021arXiv210709215L
Solar flares are rapid energy release phenomena that appear as bright
ribbons in the chromosphere and high temperature loops in the corona,
respectively. Supra-arcade Downflows (SADs) are plasma voids that first
come out above the flare loops and then move quickly toward the flare
loop top during the decay phase of the flare. In our work, we study
20 SADs appearing in three flares. By differential emission measure
(DEM) analysis, we calculate the DEM weighted average temperature and
emission measure of the front region and the main body of SADs. It is
found that the temperatures of the SAD front and body tend to increase
during the course of SADs flowing downwards. The relationship between
the pressure and temperature fits well with the adiabatic equation for
both the SAD front and body, suggesting that the heating of SADs is
mainly caused by adiabatic compression. Moreover, we also estimate
the velocities of SADs via the Fourier Local Correlation Tracking
method and find that increase of the temperature of the SAD front
presents a correlation with the decrease of the SAD kinetic energy,
while the SAD body does not, implying that the viscous process may
also heat the SAD front in spite of a limited role.
---------------------------------------------------------
Title: Mapping of Solar Magnetic Fields from the Photosphere to the
Top of the Chromosphere with CLASP2
Authors: McKenzie, D.; Ishikawa, R.; Trujillo Bueno, J.; Auchere, F.;
del Pino Aleman, T.; Okamoto, T.; Kano, R.; Song, D.; Yoshida, M.;
Rachmeler, L.; Kobayashi, K.; Narukage, N.; Kubo, M.; Ishikawa, S.;
Hara, H.; Suematsu, Y.; Sakao, T.; Bethge, C.; De Pontieu, B.; Vigil,
G.; Winebarger, A.; Alsina Ballester, E.; Belluzzi, L.; Stepan, J.;
Asensio Ramos, A.; Carlsson, M.; Leenaarts, J.
2021AAS...23810603M Altcode:
Coronal heating, chromospheric heating, and the heating &
acceleration of the solar wind, are well-known problems in solar
physics. Additionally, knowledge of the magnetic energy that
powers solar flares and coronal mass ejections, important drivers
of space weather, is handicapped by imperfect determination of the
magnetic field in the sun's atmosphere. Extrapolation of photospheric
magnetic measurements into the corona is fraught with difficulties and
uncertainties, partly due to the vastly different plasma beta between
the photosphere and the corona. Better results in understanding
the coronal magnetic field should be derived from measurements of
the magnetic field in the chromosphere. To that end, we are pursuing
quantitative determination of the magnetic field in the chromosphere,
where plasma beta transitions from greater than unity to less than
unity, via ultraviolet spectropolarimetry. The CLASP2 mission, flown
on a sounding rocket in April 2019, succeeded in measuring all four
Stokes polarization parameters in UV spectral lines formed by singly
ionized Magnesium and neutral Manganese. Because these ions produce
spectral lines under different conditions, CLASP2 thus was able to
quantify the magnetic field properties at multiple heights in the
chromosphere simultaneously, as shown in the recent paper by Ishikawa
et al. In this presentation we will report the findings of CLASP2,
demonstrating the variation of magnetic fields along a track on
the solar surface and as a function of height in the chromosphere;
and we will illustrate what is next for the CLASP missions and the
demonstration of UV spectropolarimetry in the solar chromosphere.
---------------------------------------------------------
Title: Critical Science Plan for the Daniel K. Inouye Solar Telescope
(DKIST)
Authors: Rast, Mark P.; Bello González, Nazaret; Bellot Rubio,
Luis; Cao, Wenda; Cauzzi, Gianna; Deluca, Edward; de Pontieu, Bart;
Fletcher, Lyndsay; Gibson, Sarah E.; Judge, Philip G.; Katsukawa,
Yukio; Kazachenko, Maria D.; Khomenko, Elena; Landi, Enrico; Martínez
Pillet, Valentín; Petrie, Gordon J. D.; Qiu, Jiong; Rachmeler,
Laurel A.; Rempel, Matthias; Schmidt, Wolfgang; Scullion, Eamon; Sun,
Xudong; Welsch, Brian T.; Andretta, Vincenzo; Antolin, Patrick; Ayres,
Thomas R.; Balasubramaniam, K. S.; Ballai, Istvan; Berger, Thomas E.;
Bradshaw, Stephen J.; Campbell, Ryan J.; Carlsson, Mats; Casini,
Roberto; Centeno, Rebecca; Cranmer, Steven R.; Criscuoli, Serena;
Deforest, Craig; Deng, Yuanyong; Erdélyi, Robertus; Fedun, Viktor;
Fischer, Catherine E.; González Manrique, Sergio J.; Hahn, Michael;
Harra, Louise; Henriques, Vasco M. J.; Hurlburt, Neal E.; Jaeggli,
Sarah; Jafarzadeh, Shahin; Jain, Rekha; Jefferies, Stuart M.; Keys,
Peter H.; Kowalski, Adam F.; Kuckein, Christoph; Kuhn, Jeffrey R.;
Kuridze, David; Liu, Jiajia; Liu, Wei; Longcope, Dana; Mathioudakis,
Mihalis; McAteer, R. T. James; McIntosh, Scott W.; McKenzie, David
E.; Miralles, Mari Paz; Morton, Richard J.; Muglach, Karin; Nelson,
Chris J.; Panesar, Navdeep K.; Parenti, Susanna; Parnell, Clare E.;
Poduval, Bala; Reardon, Kevin P.; Reep, Jeffrey W.; Schad, Thomas A.;
Schmit, Donald; Sharma, Rahul; Socas-Navarro, Hector; Srivastava,
Abhishek K.; Sterling, Alphonse C.; Suematsu, Yoshinori; Tarr, Lucas
A.; Tiwari, Sanjiv; Tritschler, Alexandra; Verth, Gary; Vourlidas,
Angelos; Wang, Haimin; Wang, Yi-Ming; NSO and DKIST Project; DKIST
Instrument Scientists; DKIST Science Working Group; DKIST Critical
Science Plan Community
2021SoPh..296...70R Altcode: 2020arXiv200808203R
The National Science Foundation's Daniel K. Inouye Solar Telescope
(DKIST) will revolutionize our ability to measure, understand,
and model the basic physical processes that control the structure
and dynamics of the Sun and its atmosphere. The first-light DKIST
images, released publicly on 29 January 2020, only hint at the
extraordinary capabilities that will accompany full commissioning of
the five facility instruments. With this Critical Science Plan (CSP)
we attempt to anticipate some of what those capabilities will enable,
providing a snapshot of some of the scientific pursuits that the DKIST
hopes to engage as start-of-operations nears. The work builds on the
combined contributions of the DKIST Science Working Group (SWG) and
CSP Community members, who generously shared their experiences, plans,
knowledge, and dreams. Discussion is primarily focused on those issues
to which DKIST will uniquely contribute.
---------------------------------------------------------
Title: Mapping solar magnetic fields from the photosphere to the
base of the corona
Authors: Ishikawa, Ryohko; Bueno, Javier Trujillo; del Pino Alemán,
Tanausú; Okamoto, Takenori J.; McKenzie, David E.; Auchère,
Frédéric; Kano, Ryouhei; Song, Donguk; Yoshida, Masaki; Rachmeler,
Laurel A.; Kobayashi, Ken; Hara, Hirohisa; Kubo, Masahito; Narukage,
Noriyuki; Sakao, Taro; Shimizu, Toshifumi; Suematsu, Yoshinori; Bethge,
Christian; De Pontieu, Bart; Dalda, Alberto Sainz; Vigil, Genevieve D.;
Winebarger, Amy; Ballester, Ernest Alsina; Belluzzi, Luca; Štěpán,
Jiří; Ramos, Andrés Asensio; Carlsson, Mats; Leenaarts, Jorrit
2021SciA....7.8406I Altcode: 2021arXiv210301583I
Routine ultraviolet imaging of the Sun's upper atmosphere shows the
spectacular manifestation of solar activity; yet we remain blind to
its main driver, the magnetic field. Here we report unprecedented
spectropolarimetric observations of an active region plage and
its surrounding enhanced network, showing circular polarization in
ultraviolet (Mg II $h$ & $k$ and Mn I) and visible (Fe I) lines. We
infer the longitudinal magnetic field from the photosphere to the
very upper chromosphere. At the top of the plage chromosphere the
field strengths reach more than 300 gauss, strongly correlated with
the Mg II $k$ line core intensity and the electron pressure. This
unique mapping shows how the magnetic field couples the different
atmospheric layers and reveals the magnetic origin of the heating in
the plage chromosphere.
---------------------------------------------------------
Title: The Magnetic Skeleton of the Solar Corona Over Several Solar
Rotations: Features, Analysis, and Community Availability
Authors: Malanushenko, A. V.; Gibson, S. E.; Kucera, T. A.; McKenzie,
D. E.
2020AGUFMSH041..02M Altcode:
The magnetic field in the solar corona is thought to be the main
driver for solar eruptive events, such as flares and coronal mass
ejections. The coronal magnetic field is therefore important to study,
but it is difficult to measure directly. Usually, it is studied through
extrapolations based on photospheric magnetograms. As the corona is
thought to be mostly in a state of equilibrium, equations of low-beta
equilibria are often used in order to study the structure of the
field, or to estimate the magnetic energy. One of the complications
that arise from this approach is that the solar photosphere itself is
not a low-beta equilibrium. <P />Images of the solar corona in extreme
ultraviolet (EUV) do not directly measure the magnetic field; however,
they do reveal structures from which information about magnetic field
can be inferred. For example, coronal loops are thought to trace
out magnetic field lines, coronal cavities are bounded by magnetic
surfaces, coronal holes are areas of magnetic flux that is open to
the heliosphere, and plasma flows are also thought to follow lines
of magnetic field. In other wavelengths, coronal spectropolarimetry
(SP) can provide us with proxies for magnetic field strength and
reveal plasma flows along the line of sight, off the limb. The EUV
images and SP data are frequently used to validate magnetic field
models. Additionally, new models are emerging which can use these data
directly as additional constraints. <P />We aggregate available relevant
features seen in EUV and SP data for several solar rotations. We
apply existing techniques to infer 3D constraints on the magnetic
field from these data. The result is an interactive 3D model based on
these constraints for a full rotation, or a "magnetic skeleton". It
is modular, so individual constraints can be easily added, or only
selected constraints can be used. The features could be exported in
either graphical or numerical form. The possible uses of our approach
include validation of magnetic models that are based on extrapolations
alone. Some models allow for using additional coronal constraints
directly. These 'skeletons' can also be used in non-magnetic-modeling
applications, as a simple, interactive reference for features seen in
a given rotation. We make the models available to the community and
show how to obtain and use them.
---------------------------------------------------------
Title: Updates on the Fundamentals of Impulsive Energy Release in
the Corona Explorer (FIERCE) mission concept
Authors: Shih, A. Y.; Glesener, L.; Krucker, S.; Guidoni, S. E.;
Christe, S.; Reeves, K.; Gburek, S.; Caspi, A.; Alaoui, M.; Allred,
J. C.; Battaglia, M.; Baumgartner, W.; Dennis, B. R.; Drake, J. F.;
Goetz, K.; Golub, L.; Hannah, I. G.; Hayes, L.; Holman, G.; Inglis,
A.; Ireland, J.; Kerr, G. S.; Klimchuk, J. A.; McKenzie, D. E.; Moore,
C. S.; Musset, S.; Reep, J. W.; Ryan, D.; Saint-Hilaire, P.; Savage,
S. L.; Schwartz, R.; Seaton, D. B.; Steslicki, M.; Woods, T. N.
2020AGUFMSH0480012S Altcode:
The Fundamentals of Impulsive Energy Release in the Corona Explorer
( FIERCE ) Medium-Class Explorer (MIDEX) mission concept addresses
the following science questions: <P />What are the physical origins
of space-weather events? <P />How are particles accelerated at the
Sun? <P />How is impulsively released energy transported throughout
the solar atmosphere? <P />How is the solar corona heated? <P />FIERCE
achieves its science objectives through co-optimized X-ray and extreme
ultraviolet (EUV) observations by the following instruments: <P />FOXSI,
a focusing hard X-ray spectroscopic imager that is able to capture the
full range of emission in flares and CMEs (e.g., faint coronal sources
near bright chromospheric sources) <P />THADIS, a high-resolution,
fast-cadence EUV imager that will not saturate for even intense flares
to follow dynamic changes in the configuration of plasma structures
<P />STC, a soft X-ray spectrometer that provides detailed thermal and
elemental composition diagnostics <P />If selected, FIERCE will launch
in 2025, near the peak of the next solar cycle, which is also well timed
with perihelia of Parker Solar Probe and Solar Orbiter . We describe the
status and latest updates of the mission concept since it was proposed
to NASA last year. We also highlight the anticipated science return
from co-observations with other observatories/instruments such as the
Expanded Owens Valley Solar Array (EOVSA) or the STIX instrument on
Solar Orbiter .
---------------------------------------------------------
Title: The Solar Cruiser Solar Sail Technology Demonstration Mission:
An ESPA-class Rideshare Enabling New Capabilities for Space Science
Authors: Johnson, L.; Carr, J.; McKenzie, D. E.; Newmark, J. S.;
Turse, D.
2020AGUFMSH040..11J Altcode:
Selected by NASA as a candidate ESPA-class rideshare technology
demonstration mission to launch with the Interstellar Mapping
and Acceleration Probe (IMAP) mission in 2024, the NASA MSFC Solar
Cruiser mission would mature solar sail technology for use in future
Heliophysics missions, as well as missions of interest across a broad
user community including NOAA, Earth, and Planetary Sciences. Solar
sails, which use reflected sunlight to derive thrust, can be used to
create artificial equilibria and near-indefinite station-keeping at
locations sunward of L1 along the Sun Earth Line (SEL), or at any
desired offset from the SEL leading or trailing the Earth in its
orbit. They can change the heliocentric inclination of a spacecraft
from the ecliptic to as high as solar polar, stopping and remaining at
any intermediate inclination orbit in between or can be used around
a range of solar system bodies. <P />The Solar Cruiser mission would
fly a small spacecraft (~100 kg) with a large (>1600 square meter)
solar sail containing embedded reflectivity control devices (RCDs) and
photovoltaic cells, attaining a characteristic acceleration of >0.12
mm/s<SUP>2</SUP>. The mission concept includes successful deployment
of the solar sail, validation of all sail subsystems, controlled
station-keeping inside of the Sun-Earth L1 point, demonstration of
pointing performance for science imaging, and finally an increase in
heliocentric inclination (out of the ecliptic plane). <P />Solar
Cruiser would serve as a pathfinder for missions that observe
the solar environment from unique vantage points such sub-L1 and
at high solar inclinations, opening a fundamentally new range of
observational capabilities for the Heliophysics Program and for space
weather science and monitoring. Observations away from the SEL present
unique opportunities for answering outstanding science questions of
Heliophysics, for improving space-weather monitoring and prediction,
and for revealing new discoveries about our Sun and solar system.
---------------------------------------------------------
Title: Optical design of the Chromospheric LAyer Spectro-Polarimeter
(CLASP2)
Authors: Tsuzuki, Toshihiro; Ishikawa, Ryohko; Kano, Ryouhei; Narukage,
Noriyuki; Song, Donguk; Yoshida, Masaki; Uraguchi, Fumihiro; Okamoto,
Takenori J.; McKenzie, David; Kobayashi, Ken; Rachmeler, Laurel;
Auchere, Frederic; Trujillo Bueno, Javier
2020SPIE11444E..6WT Altcode:
Chromospheric LAyer Spectro-Polarimeter (CLASP2) was a sounding
rocket experiment, which is a follow-up mission to the Chromospheric
Lyman-Alpha Spectro-Polarimeter (CLASP1) in 2015. To measure the
magnetic fields in the upper solar atmosphere in a highly quantitative
manner, CLASP2 changes the target wavelengths from the hydrogen Ly-α
line (121.567 nm) to Mg II lines near 280 nm. We reused the main
structure and most of the optical components in the CLASP1 instrument,
which reduced the turnaround time and cost. We added a magnifying
optical system to maintain the wavelength resolution, even at the
longer wavelength of CLASP2. Here, we describe the optical design and
performance of the CLASP2 instrument.
---------------------------------------------------------
Title: The High Inclination Solar Mission (HISM)
Authors: Kobayashi, K.; Johnson, L.; Thomas, H. D.; McIntosh,
S. W.; McKenzie, D. E.; Newmark, J. S.; Wright, K. H., Jr.; Bean, Q.;
Fabisinski, L.; Capizzo, P. D.; Clements, K. R.; Carr, J.; Heaton, A.;
Baysinger, M.; Sutherlin, S. G.; Garcia, J. C.; Medina, K.; Turse, D.
2020AGUFMSH0110004K Altcode:
The High Inclination Solar Mission (HISM) is an out-of-the-ecliptic
solar sail mission concept for observing the Sun and the
heliosphere. The mission profile is based on the Solar Polar Imager
concept: initially spiraling in to a 0.48 AU ecliptic orbit,
then increasing the orbital inclination at a rate of up to 10°
degrees per year, ultimately reaching a heliographic inclination of
>75°. The orbital profile is achieved using solar sails based on
the sail design for the Solar Cruiser mission, currently in Phase-A
study at NASA Marshall Space Flight Center. <P />An initial instrument
complement was assumed for the study, consisting of a combination of
remote, in-situ, and plasma wave instruments with a total mass of 66
kg. These provide a comprehensive suite of instruments to study the
solar polar regions and connections to the heliosphere. <P />The 7,000
m<SUP>2</SUP> sail used in the mission assessment is a direct extension
of the 4-quadrant 1,666 m<SUP>2</SUP> Solar Cruiser design and employs
the same type of high strength composite boom, deployment mechanism,
and membrane technology. The sail system modeled is spun (~1 rpm) to
assure required boom characteristics with margin. The spacecraft bus
features a fine-pointing 3-axis stabilized instrument platform that
allows full science observations as soon as the spacecraft reaches
a solar distance of 0.48 AU. The spacecraft provides 95W power to
science instruments and 8 Gbit/day downlink capability.
---------------------------------------------------------
Title: The Solar Cruiser Mission Concept — Enabling New Vistas
for Heliophysics
Authors: Johnson, L.; McKenzie, D.; Newmark, J.
2020AAS...23610608J Altcode:
Selected by NASA as a candidate technology demonstration mission for
flight in 2024, the NASA MSFC Solar Cruiser mission will mature solar
sail technology for use in future Heliophysics missions, as well as
missions of interest across a broad user community including NOAA,
Earth and Planetary Sciences, etc. Solar sails can be used to create
artificial equilibria and near-indefinite station-keeping at locations
sunward of L1 along the Sun Earth Line (SEL), or at any desired offset
from the SEL leading or trailing the Earth in its orbit. They can
change the heliocentric inclination of a spacecraft from the ecliptic
to as high as solar polar, stopping and remaining at any intermediate
inclination orbit in between or can be used around a range of solar
system bodies. The Solar Cruiser mission would fly a small spacecraft
with a large (>1500 square meter) solar sail containing embedded
reflectivity control devices (RCDs) and photovoltaic cells. The mission
concept includes successful deployment of the solar sail, validation of
all sail subsystems, controlled station-keeping inside of the Sun-Earth
L1 point, demonstration of pointing performance for science imaging,
and finally an increase in heliocentric inclination (out of the ecliptic
plane).Solar Cruiser would serve as a pathfinder for missions that
observe the solar environment from unique vantage points such as a
high inclination solar mission, opening a fundamentally new range of
observational capabilities for the Heliophysics Program and for space
weather monitoring. Observations away from the Sun-Earth line (SEL)
present unique opportunities for answering the outstanding science
questions of Heliophysics, for improving space-weather monitoring and
prediction, and for revealing new discoveries about our Sun and solar
system. High solar inclinations are particularly compelling. Investment
in, and demonstration of, the technology needed to enable polar
missions is essential to making this unique vantage point a reality
in the next decade.
---------------------------------------------------------
Title: The High Inclination Solar Mission (HISM) mission concept
Authors: Kobayashi, K.; McKenzie, D.; Johnson, L.; Rachmeler, L.;
McIntosh, S.; Thomas, H. D.; Newmark, J.; Wright, K.; Curran, F.
2020AAS...23610609K Altcode:
The High Inclination Solar Mission (HISM) is a concept for
an out-of-the-ecliptic mission for observing the Sun and the
heliosphere. The mission profile is largely based on the Solar Polar
Imager concept; initially taking ~2.6 yrs to spiral in to a 0.48
AU equatorial orbit, then increasing the orbital inclination at a
rate of 10 degrees per year, ultimately reaching an inclination of
>75 degrees at the end of the mission. The orbital profile is
achieved using solar sails derived from the technology currently
being developed for the Solar Cruiser mission. HISM remote sensing
instruments comprise an imaging spectropolarimeter (Doppler imager
/ magnetograph) and a visible light coronagraph. The in-situ
instruments include a Faraday cup, an ion composition spectrometer,
and magnetometers. Plasma wave measurements are made with electrical
antennas and high speed magnetometers. The 7,000 m<SUP>2</SUP> sail
used in mission assessment is a direct extension of the 4-quadrant,
1,600 m<SUP>2</SUP> Solar Cruiser Phase-A design and employs the
same type of high strength composite boom, deployment mechanism,
and membrane technology. The sail system modelled is spun (~1 rpm)
to assure required boom characteristics with margin. The spacecraft
bus features a fine-pointing 3-axis stabilized instrument
---------------------------------------------------------
Title: Observation and Modeling of High-temperature Solar Active
Region Emission during the High-resolution Coronal Imager Flight of
2018 May 29
Authors: Warren, Harry P.; Reep, Jeffrey W.; Crump, Nicholas A.;
Ugarte-Urra, Ignacio; Brooks, David H.; Winebarger, Amy R.; Savage,
Sabrina; De Pontieu, Bart; Peter, Hardi; Cirtain, Jonathan W.; Golub,
Leon; Kobayashi, Ken; McKenzie, David; Morton, Richard; Rachmeler,
Laurel; Testa, Paola; Tiwari, Sanjiv; Walsh, Robert
2020ApJ...896...51W Altcode:
Excellent coordinated observations of NOAA active region 12712 were
obtained during the flight of the High-resolution Coronal Imager (Hi-C)
sounding rocket on 2018 May 29. This region displayed a typical active
region core structure with relatively short, high-temperature loops
crossing the polarity inversion line and bright "moss" located at the
footpoints of these loops. The differential emission measure (DEM) in
the active region core is very sharply peaked at about 4 MK. Further,
there is little evidence for impulsive heating events in the moss, even
at the high spatial resolution and cadence of Hi-C. This suggests that
active region core heating is occurring at a high frequency and keeping
the loops close to equilibrium. To create a time-dependent simulation of
the active region core, we combine nonlinear force-free extrapolations
of the measured magnetic field with a heating rate that is dependent
on the field strength and loop length and has a Poisson waiting time
distribution. We use the approximate solutions to the hydrodynamic
loop equations to simulate the full ensemble of active region core
loops for a range of heating parameters. In all cases, we find that
high-frequency heating provides the best match to the observed DEM. For
selected field lines, we solve the full hydrodynamic loop equations,
including radiative transfer in the chromosphere, to simulate transition
region and chromospheric emission. We find that for heating scenarios
consistent with the DEM, classical signatures of energy release,
such as transition region brightenings and chromospheric evaporation,
are weak, suggesting that they would be difficult to detect.
---------------------------------------------------------
Title: The High Inclination Solar Mission
Authors: Kobayashi, K.; Johnson, L.; Thomas, H.; McIntosh, S.;
McKenzie, D.; Newmark, J.; Heaton, A.; Carr, J.; Baysinger, M.; Bean,
Q.; Fabisinski, L.; Capizzo, P.; Clements, K.; Sutherlin, S.; Garcia,
J.; Medina, K.; Turse, D.
2020arXiv200603111K Altcode:
The High Inclination Solar Mission (HISM) is a concept for
an out-of-the-ecliptic mission for observing the Sun and the
heliosphere. The mission profile is largely based on the Solar Polar
Imager concept: initially spiraling in to a 0.48 AU ecliptic orbit,
then increasing the orbital inclination at a rate of $\sim 10$ degrees
per year, ultimately reaching a heliographic inclination of $>$75
degrees. The orbital profile is achieved using solar sails derived from
the technology currently being developed for the Solar Cruiser mission,
currently under development. HISM remote sensing instruments comprise an
imaging spectropolarimeter (Doppler imager / magnetograph) and a visible
light coronagraph. The in-situ instruments include a Faraday cup, an ion
composition spectrometer, and magnetometers. Plasma wave measurements
are made with electrical antennas and high speed magnetometers. The
$7,000\,\mathrm{m}^2$ sail used in the mission assessment is a direct
extension of the 4-quadrant $1,666\,\mathrm{m}^2$ Solar Cruiser design
and employs the same type of high strength composite boom, deployment
mechanism, and membrane technology. The sail system modelled is spun
(~1 rpm) to assure required boom characteristics with margin. The
spacecraft bus features a fine-pointing 3-axis stabilized instrument
platform that allows full science observations as soon as the spacecraft
reaches a solar distance of 0.48 AU.
---------------------------------------------------------
Title: The Drivers of Active Region Outflows into the Slow Solar Wind
Authors: Brooks, David H.; Winebarger, Amy R.; Savage, Sabrina; Warren,
Harry P.; De Pontieu, Bart; Peter, Hardi; Cirtain, Jonathan W.; Golub,
Leon; Kobayashi, Ken; McIntosh, Scott W.; McKenzie, David; Morton,
Richard; Rachmeler, Laurel; Testa, Paola; Tiwari, Sanjiv; Walsh, Robert
2020ApJ...894..144B Altcode: 2020arXiv200407461B
Plasma outflows from the edges of active regions have been suggested as
a possible source of the slow solar wind. Spectroscopic measurements
show that these outflows have an enhanced elemental composition,
which is a distinct signature of the slow wind. Current spectroscopic
observations, however, do not have sufficient spatial resolution to
distinguish what structures are being measured or determine the driver
of the outflows. The High-resolution Coronal Imager (Hi-C) flew on a
sounding rocket in 2018 May and observed areas of active region outflow
at the highest spatial resolution ever achieved (250 km). Here we use
the Hi-C data to disentangle the outflow composition signatures observed
with the Hinode satellite during the flight. We show that there are
two components to the outflow emission: a substantial contribution
from expanded plasma that appears to have been expelled from closed
loops in the active region core and a second contribution from dynamic
activity in active region plage, with a composition signature that
reflects solar photospheric abundances. The two competing drivers of the
outflows may explain the variable composition of the slow solar wind.
---------------------------------------------------------
Title: Is the High-Resolution Coronal Imager Resolving Coronal
Strands? Results from AR 12712
Authors: Williams, Thomas; Walsh, Robert W.; Winebarger, Amy R.;
Brooks, David H.; Cirtain, Jonathan W.; De Pontieu, Bart; Golub,
Leon; Kobayashi, Ken; McKenzie, David E.; Morton, Richard J.; Peter,
Hardi; Rachmeler, Laurel A.; Savage, Sabrina L.; Testa, Paola; Tiwari,
Sanjiv K.; Warren, Harry P.; Watkinson, Benjamin J.
2020ApJ...892..134W Altcode: 2020arXiv200111254W
Following the success of the first mission, the High-Resolution
Coronal Imager (Hi-C) was launched for a third time (Hi-C 2.1)
on 2018 May 29 from the White Sands Missile Range, NM, USA. On this
occasion, 329 s of 17.2 nm data of target active region AR 12712 were
captured with a cadence of ≈4 s, and a plate scale of 0.129 arcsec
pixel<SUP>-1</SUP>. Using data captured by Hi-C 2.1 and co-aligned
observations from SDO/AIA 17.1 nm, we investigate the widths of 49
coronal strands. We search for evidence of substructure within the
strands that is not detected by AIA, and further consider whether these
strands are fully resolved by Hi-C 2.1. With the aid of multi-scale
Gaussian normalization, strands from a region of low emission that can
only be visualized against the contrast of the darker, underlying moss
are studied. A comparison is made between these low-emission strands
and those from regions of higher emission within the target active
region. It is found that Hi-C 2.1 can resolve individual strands as
small as ≈202 km, though the more typical strand widths seen are
≈513 km. For coronal strands within the region of low emission, the
most likely width is significantly narrower than the high-emission
strands at ≈388 km. This places the low-emission coronal strands
beneath the resolving capabilities of SDO/AIA, highlighting the need
for a permanent solar observatory with the resolving power of Hi-C.
---------------------------------------------------------
Title: Hi-C 2.1 Observations of Jetlet-like Events at Edges of Solar
Magnetic Network Lanes
Authors: Panesar, Navdeep K.; Sterling, Alphonse C.; Moore, Ronald L.;
Winebarger, Amy R.; Tiwari, Sanjiv K.; Savage, Sabrina L.; Golub, Leon
E.; Rachmeler, Laurel A.; Kobayashi, Ken; Brooks, David H.; Cirtain,
Jonathan W.; De Pontieu, Bart; McKenzie, David E.; Morton, Richard J.;
Peter, Hardi; Testa, Paola; Walsh, Robert W.; Warren, Harry P.
2019ApJ...887L...8P Altcode: 2019arXiv191102331P
We present high-resolution, high-cadence observations of six,
fine-scale, on-disk jet-like events observed by the High-resolution
Coronal Imager 2.1 (Hi-C 2.1) during its sounding-rocket flight. We
combine the Hi-C 2.1 images with images from the Solar Dynamics
Observatory (SDO)/Atmospheric Imaging Assembly (AIA) and the Interface
Region Imaging Spectrograph (IRIS), and investigate each event’s
magnetic setting with co-aligned line-of-sight magnetograms from the
SDO/Helioseismic and Magnetic Imager (HMI). We find that (i) all six
events are jetlet-like (having apparent properties of jetlets), (ii)
all six are rooted at edges of magnetic network lanes, (iii) four of
the jetlet-like events stem from sites of flux cancelation between
majority-polarity network flux and merging minority-polarity flux, and
(iv) four of the jetlet-like events show brightenings at their bases
reminiscent of the base brightenings in coronal jets. The average
spire length of the six jetlet-like events (9000 ± 3000 km) is three
times shorter than that for IRIS jetlets (27,000 ± 8000 km). While
not ruling out other generation mechanisms, the observations suggest
that at least four of these events may be miniature versions of both
larger-scale coronal jets that are driven by minifilament eruptions
and still-larger-scale solar eruptions that are driven by filament
eruptions. Therefore, we propose that our Hi-C events are driven by
the eruption of a tiny sheared-field flux rope, and that the flux rope
field is built and triggered to erupt by flux cancelation.
---------------------------------------------------------
Title: Combined Next-Generation X-ray and EUV Observations with the
FIERCE Mission Concept
Authors: Shih, A. Y.; Glesener, L.; Christe, S.; Reeves, K.; Gburek,
S.; Alaoui, M.; Allred, J. C.; Baumgartner, W.; Caspi, A.; Dennis,
B. R.; Drake, J. F.; Goetz, K.; Golub, L.; Guidoni, S. E.; Inglis,
A.; Hannah, I. G.; Holman, G.; Hayes, L.; Ireland, J.; Kerr, G. S.;
Klimchuk, J. A.; Krucker, S.; McKenzie, D. E.; Moore, C. S.; Musset,
S.; Reep, J. W.; Ryan, D.; Saint-Hilaire, P.; Savage, S. L.; Seaton,
D. B.; Steslicki, M.; Woods, T. N.
2019AGUFMSH33A..08S Altcode:
While there have been significant advances in our understanding
of impulsive energy release at the Sun through the combination
of RHESSI X-ray observations and SDO/AIA EUV observations, there
is a clear science need for significantly improved X-ray and EUV
observations. These new observations must capture the full range
of emission in flares and CMEs (e.g., faint coronal sources near
bright chromospheric sources), connect the intricate evolution of
energy release with dynamic changes in the configuration of plasma
structures, and identify the signatures of impulsive energy release in
even the quiescent Sun. The Fundamentals of Impulsive Energy Release
in the Corona Explorer ( FIERCE ) MIDEX mission concept makes these
observations by combining the two instruments previously proposed on the
FOXSI SMEX mission concept - a focusing hard X-ray spectroscopic imager
and a soft X-ray spectrometer - with a high-resolution EUV imager that
will not saturate for even intense flares. All instruments observe at
high cadence to capture the initiation of solar transient events and
the fine time structure within events. FIERCE would launch in mid-2025,
near the peak of the next solar cycle, which is also well timed with
perihelions of Parker Solar Probe and Solar Orbiter.
---------------------------------------------------------
Title: Measuring and Modeling the Rate of Separator Reconnection
between an Emerging and an Existing Active Region
Authors: McCarthy, Marika I.; Longcope, Dana W.; Malanushenko, Anna;
McKenzie, David E.
2019ApJ...887..140M Altcode: 2019arXiv191106340M
Magnetic reconnection occurs when new flux emerges into the corona
and becomes incorporated into the existing coronal field. A new
active region (AR) emerging in the vicinity of an existing AR
provides a convenient laboratory in which reconnection of this kind
can be quantified. We use high time-cadence 171 Å data from Solar
Dynamics Observatory (SDO)/AIA, focused on new/old active region
pair 11147/11149, to quantify reconnection. We identify new loops
as brightenings within a strip of pixels between the regions. This
strategy is premised on the assumption that the energy responsible for
brightening a loop originates in magnetic reconnection. We catalog 301
loops observed in the 48 hr time period beginning with the emergence of
AR 11149. The rate at which these loops appear between the two ARs is
used to calculate the reconnection rate between them. We then fit these
loops with magnetic field, solving for each loop’s field strength,
geometry, and twist (via its proxy, coronal α). We find the rate of
newly brightened flux overestimates the flux that could be undergoing
reconnection. This excess can be explained by our finding that the
interconnecting region is not at its lowest energy (constant-α)
state; the extrapolations exhibit loop-to-loop variation in α. This
flux overestimate may result from the slow emergence of AR 11149,
which allows time for Taylor relaxation internal to the domain of the
reconnected flux to bring the α distribution toward a single value,
providing another mechanism for brightening loops after they are
first created.
---------------------------------------------------------
Title: The Chromospheric Layer Spectro-Polarimeter (CLASP2) Sounding
Rocket Mission: First Results
Authors: McKenzie, D. E.; Ishikawa, R.; Trujillo Bueno, J.; Auchere,
F.; Rachmeler, L.; Kano, R.; Song, D.; Okamoto, J.; Kobayashi, K.;
Yoshida, M.
2019AGUFMSH44A..06M Altcode:
A major challenge for heliophysics is to decipher the magnetic structure
of the chromosphere, because of its vital role in the transport of
energy into the corona and solar wind. Routine satellite measurements
of the chromospheric magnetic field will dramatically improve our
understanding of the chromosphere and its connection to the rest of
the solar atmosphere. Before such a satellite can be considered for
flight, we must refine the measurement techniques by exploring emission
lines with a range of magnetic sensitivities. In 2015, CLASP achieved
the first measurement of linear polarization produced by scattering
processes in a far UV resonance line (hydrogen Lyman-α), and the
first exploration of the magnetic field (via the Hanle effect) and
geometrical complexity in quiet regions of the chromosphere/corona
transition region. These measurements are a first step towards
routine quantitative characterization of the local thermal and magnetic
conditions in this key layer of the solar atmosphere. <P />Nonetheless,
Lyman-α is only one of the magnetically sensitive spectral lines in
the UV spectrum. CLASP2 extends the capability of UV spectropolarimetry
by acquiring groundbreaking measurements in the Mg II h and k spectral
lines near 280 nm, whose cores form about 100 km below the Lyman-α
core. These lines are sensitive to a larger range of field strengths
than Lyman-α, through both the Hanle and Zeeman effects. CLASP2
captures measurements of linear and circular polarization to enable
the first determination of all 4 Stokes parameters in chromospheric
UV radiation. Coupled with numerical modeling of the observed spectral
line polarization (anisotropic radiation pumping with Hanle, Zeeman and
magneto-optical effects), CLASP2 is a pathfinder for determination
of the magnetic field's strength and direction, as well as of the
geometry of the plasma in the upper solar chromosphere. <P />CLASP2
was launched from White Sands Missile Range in April 2019. In this
presentation, we will summarize the characteristics of the CLASP2
flight, the performance of the UV telescope and spectropolarimeter,
and our preliminary findings.
---------------------------------------------------------
Title: Center-to-Limb Variation of the polarization of Mg II h &
k lines as measured by CLASP2
Authors: Rachmeler, L.; McKenzie, D. E.; Ishikawa, R.; Kano, R.;
Trujillo Bueno, J.; Kobayashi, K.; Song, D.; Yoshida, M.; Auchere,
F.; Okamoto, J.
2019AGUFMSH11D3380R Altcode:
The Chromospheric LAyer SpectroPolarimeter 2 (CLASP2) is a sounding
rocket that was launched from White Sands Missile Range in April
2019. CLASP2 is a reflight of the CLASP instrument, and has been
modified to observe the polarization of the Magnesium II h & k
lines in the solar chromosphere. The instrument contains a slit-jaw
context imager at Lyman Alpha (~121.6nm) and two spectropolarimetric
cameras that capture Mg II h & k near 280nm. A rotating polarization
modulation unit allows us to capture the full polarization state of
Mg II h & k; the measured polarization signals are sensitive
to the Hanle and the Zeeman magnetic effects, and magneto-optical
effects. The center-to-limb variations (CLV) of the intensity of
these lines has been measured, but the CLV of the polarization signals
has only been investigated theoretically. The first flight of CLASP,
which measured the linear polarization of the Lyman alpha line, found
a surprising lack of CLV in the line core (Kano et al. 2017), which
has important implications for the magnetic strength and geometrical
complexity of the chromosphere-corona transition region (Trujillo Bueno
et al. 2018). We present here initial results on the CLV of the Mg II
polarization signals.
---------------------------------------------------------
Title: Fine-scale Explosive Energy Release at Sites of Prospective
Magnetic Flux Cancellation in the Core of the Solar Active Region
Observed by Hi-C 2.1, IRIS, and SDO
Authors: Tiwari, Sanjiv K.; Panesar, Navdeep K.; Moore, Ronald L.;
De Pontieu, Bart; Winebarger, Amy R.; Golub, Leon; Savage, Sabrina L.;
Rachmeler, Laurel A.; Kobayashi, Ken; Testa, Paola; Warren, Harry P.;
Brooks, David H.; Cirtain, Jonathan W.; McKenzie, David E.; Morton,
Richard J.; Peter, Hardi; Walsh, Robert W.
2019ApJ...887...56T Altcode: 2019arXiv191101424T
The second Hi-C flight (Hi-C 2.1) provided unprecedentedly high spatial
and temporal resolution (∼250 km, 4.4 s) coronal EUV images of Fe IX/X
emission at 172 Å of AR 12712 on 2018 May 29, during 18:56:21-19:01:56
UT. Three morphologically different types (I: dot-like; II: loop-like;
III: surge/jet-like) of fine-scale sudden-brightening events (tiny
microflares) are seen within and at the ends of an arch filament system
in the core of the AR. Although type Is (not reported before) resemble
IRIS bombs (in size, and brightness with respect to surroundings),
our dot-like events are apparently much hotter and shorter in span
(70 s). We complement the 5 minute duration Hi-C 2.1 data with SDO/HMI
magnetograms, SDO/AIA EUV images, and IRIS UV spectra and slit-jaw
images to examine, at the sites of these events, brightenings and
flows in the transition region and corona and evolution of magnetic
flux in the photosphere. Most, if not all, of the events are seated
at sites of opposite-polarity magnetic flux convergence (sometimes
driven by adjacent flux emergence), implying likely flux cancellation
at the microflare’s polarity inversion line. In the IRIS spectra
and images, we find confirming evidence of field-aligned outflow from
brightenings at the ends of loops of the arch filament system. In types
I and II the explosion is confined, while in type III the explosion
is ejective and drives jet-like outflow. The light curves from Hi-C,
AIA, and IRIS peak nearly simultaneously for many of these events,
and none of the events display a systematic cooling sequence as seen in
typical coronal flares, suggesting that these tiny brightening events
have chromospheric/transition region origin.
---------------------------------------------------------
Title: The High-Resolution Coronal Imager, Flight 2.1
Authors: Rachmeler, Laurel A.; Winebarger, Amy R.; Savage, Sabrina L.;
Golub, Leon; Kobayashi, Ken; Vigil, Genevieve D.; Brooks, David H.;
Cirtain, Jonathan W.; De Pontieu, Bart; McKenzie, David E.; Morton,
Richard J.; Peter, Hardi; Testa, Paola; Tiwari, Sanjiv K.; Walsh,
Robert W.; Warren, Harry P.; Alexander, Caroline; Ansell, Darren;
Beabout, Brent L.; Beabout, Dyana L.; Bethge, Christian W.; Champey,
Patrick R.; Cheimets, Peter N.; Cooper, Mark A.; Creel, Helen K.;
Gates, Richard; Gomez, Carlos; Guillory, Anthony; Haight, Harlan;
Hogue, William D.; Holloway, Todd; Hyde, David W.; Kenyon, Richard;
Marshall, Joseph N.; McCracken, Jeff E.; McCracken, Kenneth; Mitchell,
Karen O.; Ordway, Mark; Owen, Tim; Ranganathan, Jagan; Robertson,
Bryan A.; Payne, M. Janie; Podgorski, William; Pryor, Jonathan; Samra,
Jenna; Sloan, Mark D.; Soohoo, Howard A.; Steele, D. Brandon; Thompson,
Furman V.; Thornton, Gary S.; Watkinson, Benjamin; Windt, David
2019SoPh..294..174R Altcode: 2019arXiv190905942R
The third flight of the High-Resolution Coronal Imager (Hi-C 2.1)
occurred on May 29, 2018; the Sounding Rocket was launched from White
Sands Missile Range in New Mexico. The instrument has been modified
from its original configuration (Hi-C 1) to observe the solar corona
in a passband that peaks near 172 Å, and uses a new, custom-built
low-noise camera. The instrument targeted Active Region 12712, and
captured 78 images at a cadence of 4.4 s (18:56:22 - 19:01:57 UT; 5
min and 35 s observing time). The image spatial resolution varies due
to quasi-periodic motion blur from the rocket; sharp images contain
resolved features of at least 0.47 arcsec. There are coordinated
observations from multiple ground- and space-based telescopes providing
an unprecedented opportunity to observe the mass and energy coupling
between the chromosphere and the corona. Details of the instrument
and the data set are presented in this paper.
---------------------------------------------------------
Title: Examination of Separator Reconnection Rates in a Series of
Adjacent Emerging/Existing Active Region Pairs
Authors: McCarthy, M.; Longcope, D. W.; Malanushenko, A. V.; McKenzie,
D. E.
2019AGUFMSH11D3387M Altcode:
Changes in magnetic field line topology must be occurring when new flux
emerges in the solar corona in order for it to become incorporated
in the existing coronal field. Magnetic reconnection is the process
responsible for this incorporation. We have previously quantified
this process using a system in which a new active region (AR) emerges
in the vicinity of an existing one by cataloging the loops formed
between them. We make a spatial/temporal stack plot of the region
between the ARs by extracting the pixels along a virtual slit. A
persistent, bright streak in such a plot indicates a coronal loop
connecting the newly emerging flux to the existing AR. We assert that
loops formed post-emergence between the ARs are initially the result of
reconnection. This work presents an extension of our data set to include
12 new emergence events using high time-cadence data from SDO/AIA. Our
data set includes several events in which no reconnected loops seem
to form between the two ARs. We present an improved method of our loop
cataloging procedure. Previous studies of such events have both under
and over-sampled the expected reconnected flux formed between the two
regions, and included a variety of delays between the emergence of the
new AR and the onset of reconnection. To elucidate such discrepancies,
we fit loops using a linear force-free field (LFFF) model which we
then use to construct a full, non-linear force-free field (NLFFF)
model of the system. <P />This work was supported by NASA's HGI program.
---------------------------------------------------------
Title: FIERCE Science: Expected Results From a High-Energy
Medium-Class Explorer
Authors: Glesener, L.; Shih, A. Y.; Christe, S.; Reeves, K.; Gburek,
S.; Alaoui, M.; Allred, J. C.; Baumgartner, W.; Caspi, A.; Dennis,
B. R.; Drake, J. F.; Golub, L.; Goetz, K.; Guidoni, S. E.; Hannah,
I. G.; Hayes, L.; Holman, G.; Inglis, A.; Ireland, J.; Kerr, G. S.;
Klimchuk, J. A.; Krucker, S.; McKenzie, D. E.; Moore, C. S.; Musset,
S.; Reep, J. W.; Ryan, D.; Saint-Hilaire, P.; Savage, S. L.; Seaton,
D. B.; Steslicki, M.; Woods, T. N.
2019AGUFMSH31C3313G Altcode:
A variety of individual X-ray and EUV instruments have probed
high-energy aspects of the Sun over the decades, each contributing
pieces to the puzzles of the energization, heating, and acceleration of
solar plasma and particles. But fundamental difficulties in sensitivity
and dynamic range impart big challenges in probing the details of
particle acceleration sites, understanding how eruptions and flares are
initiated, and tracking the intricacies of energy transfer as flares
evolve. The Fundamentals of Impulsive Energy Release in the Corona
Explorer ( FIERCE ) mission will make substantial leaps forward in
these scientific ventures by combining a variety of instruments into
one platform, each optimized to have high sensitivity and dynamic
range. FIERCE is a proposed NASA Heliophysics Medium-Class Explorer
that will investigate high-energy solar phenomena across a variety
of spectral and spatial dimensions. It combines hard X-ray imaging
spectroscopy (via focusing, for the first time for a solar-dedicated
spacecraft), spatially integrated soft X-ray spectroscopy, and fast,
high-resolution extreme ultraviolet imaging at coronal and flare
temperatures. FIERCE uses this array of instruments to make important
contributions toward probing the genesis of space weather events,
the acceleration of particles, the transport of flare energy, and the
heating of the corona. Here, we present some of the expected science
outcomes for the FIERCE observatory, concentrating on the ways in which
FIERCE can probe confined and eruptive events, particle acceleration
everywhere it may occur on the Sun, and the connections of solar
high-energy phenomena to the heliosphere.
---------------------------------------------------------
Title: Heating Features of Interesting Supra-arcade Downflows
Authors: Li, Z.; Kittrell, D.; Reeves, K.; Weber, M.; McKenzie, D. E.;
Freed, M.
2019AGUFMSH11D3378L Altcode:
Supra-arcade downflows (SADs) have been observed above flare loops
during the decay phase of flare. They appear as tadpole-like dark plasma
voids traveling towards the Sun. In areas surrounding where they appear,
temperatures are often high. We aim to investigate temperature and
heating mechanism of SADs. We apply our analysis to the M1.7 flare
that occurred on 2012 July 12 and was observed by the Atmospheric
Imaging Assembly (AIA) on the Solar Dynamics Observatory. There
are many obvious SADs above the arcade during this event in the AIA
131 Å channel. We calculate velocities of SADs using the Fourier
Local Correlation Tracking (FLCT, Fisher & Welsch, 2008) method
to derive velocities in the supra-arcade region. Using corks to track
the calculated velocities, we find our velocity results are consistent
with the SAD motions in the AIA 131 Å intensity movie. We use the
velocities to derive the adiabatic heating caused by the compression of
plasma. Preliminary results indicate that there is adiabatic heating
in front of the SADs. <P />This work supported by the NSF-REU solar
physics program at SAO, grant number AGS-1560313, the NSF SHINE program
AGS-1723425, and NASA grant number 80NSSC18K0732.
---------------------------------------------------------
Title: The Chromospheric Layer Spectro-Polarimeter (CLASP2) Sounding
Rocket Mission: First Results
Authors: McKenzie, David Eugene; Ishikawa, Ryohko; Kano, Ryouhei;
Rachmeler, Laurel; Trujillo Bueno, Javier; Kobayashi, Ken; Song,
Donguk; Yoshida, Masaki; Auchere, Frederic; Okamoto, Takenori
2019AAS...23412601M Altcode:
A major challenge for heliophysics is to decipher the magnetic structure
of the chromosphere, because of its vital role in the transport of
energy into the corona and solar wind. Routine satellite measurements
of the chromospheric magnetic field will dramatically improve our
understanding of the chromosphere and its connection to the rest of
the solar atmosphere. Before such a satellite can be considered for
flight, we must refine the measurement techniques by exploring emission
lines with a range of magnetic sensitivities. In 2015, CLASP achieved
the first measurement of linear polarization produced by scattering
processes in a far UV resonance line (hydrogen Lyman-α), and the
first exploration of the magnetic field (via the Hanle effect) and
geometrical complexity in quiet regions of the chromosphere-corona
transition region. These measurements are a first step towards
routine quantitative characterization of the local thermal and magnetic
conditions in this key layer of the solar atmosphere. <P />Nonetheless,
Lyman-α is only one of the magnetically sensitive spectral lines in the
UV spectrum. CLASP2 extends the capability of UV spectropolarimetry by
acquiring ground-breaking measurements in the Mg II h and k spectral
lines near 280 nm, whose cores form about 100 km below the Lyman-α
core. These lines are sensitive to a larger range of field strengths
than Lyman-α, through both the Hanle and Zeeman effects. CLASP2 will
capture measurements of linear and circular polarization to enable the
first determination of all 4 Stokes parameters in chromospheric UV
radiation. Coupled with numerical modeling of the observed spectral
line polarization (anisotropic radiation pumping with Hanle, Zeeman
and magneto-optical effects), CLASP2 is a pathfinder for determination
of the magnetic field's strength and direction, as well as of the
geometry of the plasma in the upper solar chromosphere. <P />CLASP2
will launch from White Sands Missile Range in April 2019. In this
presentation, we will summarize the characteristics of the CLASP2
flight, the performance of the UV telescope and spectropolarimeter,
and our preliminary findings.
---------------------------------------------------------
Title: Lyman-α imaging polarimetry with the CLASP2 sounding rocket
mission
Authors: Kano, Ryouhei; Ishikawa, Ryohko; McKenzie, David Eugene;
Trujillo Bueno, Javier; Song, Donguk; Yoshida, Masaki; Okamoto,
Takenori; Rachmeler, Laurel; Kobayashi, Ken; Auchere, Frederic
2019AAS...23430216K Altcode:
Ultraviolet polarimetry offers a unique opportunity to explore the upper
solar chromosphere and the transition region (TR) to the million-degree
corona. These outer atmospheric regions play a key role in the transfer
of mass and energy from the solar photosphere to the corona. With
a sounding rocket experiment called the Chromospheric Lyman-Alpha
Spectro-Polarimeter (CLASP), in September 2015 we succeeded in obtaining
the first measurement of the linear polarization produced by scattering
processes in the hydrogen Lyman-α line of the solar disk radiation. The
analysis and interpretation of such spectro-polarimetric observation
allowed us to obtain information on the geometrical complexity of
the corrugated surface that delineates the TR, as well as on the
magnetic field strength via the Hanle effect. At the same time, the
CLASP slit-jaw (SJ) optics system, which is a Lyman-α filter imager
characterized by a FWHM= 7 nm, allowed us to obtain broad-band Stokes-I
and Q/I images over a large field of view. The obtained broad-band
Q/I images are dominated by the scattering polarization signals of the
Lyman-α wings, and not by the much weaker line-center signals where
the Hanle effect operates. Recently, Alsina Ballester et al. (2019,
ApJ, in press) showed that the scattering polarization signals of the
Lyman-α wings are sensitive to chromospheric magnetic fields via the
magneto-optical effects. Therefore, Lyman-α imaging polarimetry is of
scientific interest also for magnetic-field investigations. On April
11, 2019, we performed another sounding rocket experiment, called
the Chromospheric LAyer Spectro-Polarimeter (CLASP2). We used the
same instrument after significant modifications in order to obtain
spectro-polarimetric observations of a plage and a quiet region in
the ionized magnesium lines around 280 nm (i.e., the Mg II h &
k lines). At the same time, the CLASP2 SJ optics system allowed us to
obtain broad-band Q/I and U/I images at the Lyman-α wavelength, in
addition to the well-known SJ intensity images. In this presentation,
we provide a first overview of the CLASP2 SJ data.
---------------------------------------------------------
Title: Measuring and modeling the rate of separator reconnection
between an emerging and existing active region
Authors: McCarthy, Marika; Longcope, Dana; Malanushenko, Anna;
McKenzie, David Eugene
2019AAS...23411705M Altcode:
Magnetic reconnection must occur when new flux emerges into the corona
and becomes incorporated into the existing coronal field. A new active
region (AR) emerging in the vicinity of an existing AR provides
a convenient laboratory in which reconnection of this kind can be
quantified. We perform such a measurement using high time-cadence
171 Å data from SDO/AIA of active region NOAA AR11149 which emerged
in the vicinity of AR11147 beginning on 20 January 2011. We make a
spatial/temporal stack plot of the region between the ARs by extracting
the pixels along a virtual slit. A persistent, bright streak in such
a plot indicates a bright coronal loop connecting the newly emerging
flux to the existing AR. This loop must have been formed through a
process of coronal reconnection across the separator separating the
four topologically distinct flux systems. We assume further that energy
released during that reconnection is responsible for its brightening. We
catalog 205 loops observed in the a 48-hour time period beginning
with the emergence of AR 11149. The rate at which new magnetic flux
appears is used to calculate the rate of separator reconnection. We
can further fit these cataloged field lines using a linear force-free
field (LFFF) extrapolation, solving for an individual loop's field
strength and twist. Ultimately, we find the rate of newly-brightened
flux overestimates the flux which could be undergoing reconnection. This
excess can be explained by our finding that the interconnecting region
is not at its lowest energy (constant-α) state; the LFFF modeling
shows a variation in values of α. This overestimate might be the result
of the region's unusually slow emergence, providing time for internal
Taylor-relaxation reconnection of the interconnecting flux following
its initial formation by reconnection. We support this hypothesis by
computing the rates of brightening within the plane of the virtual
slit. This work was supported by NASA's HGI program.
---------------------------------------------------------
Title: CLASP2: The Chromospheric LAyer Spectro-Polarimeter
Authors: McKenzie, D. E.; Ishikawa, R.; Trujillo Bueno, J.; Auchére,
F.; Rachmeler, L. A.; Kubo, M.; Kobayashi, K.; Winebarger, A. R.;
Bethge, C. W.; Narukage, N.; Kano, R.; Ishikawa, S.; de Pontieu,
B.; Carlsson, M.; Yoshida, M.; Belluzzi, L.; Štěpán, J.; del Pino
Alemán, T.; Alsina Ballester, E.; Asensio Ramos, A.
2019ASPC..526..361M Altcode:
The hydrogen Lyman-α line at 121.6 nm and the Mg k line at 279.5
nm are especially relevant for deciphering the magnetic structure
of the chromosphere since their line-center signals are formed in
the chromosphere and transition region, with unique sensitivities to
magnetic fields. We propose the Chromospheric LAyer Spectro-Polarimeter
(CLASP2), to build upon the success of the first CLASP flight, which
measured the linear polarization in H I Lyman-α. The existing CLASP
instrument will be refitted to measure all four Stokes parameters in
the 280 nm range, including variations due to the anisotropic radiation
pumping, the Hanle effect, and the Zeeman effect.
---------------------------------------------------------
Title: Quantifying Turbulent Dynamics Found within the Plasma Sheets
of Multiple Solar Flares
Authors: Freed, Michael S.; McKenzie, David E.
2018ApJ...866...29F Altcode:
It is vital to our understanding of solar flares that we discern how
turbulent motion can affect the magnetic reconnection process. The
objective of this study is to quantify the velocity and vorticity
structures inherent in the observed motions found in a plasma sheet
above arcades during a solar flare. The most noticeable features
in these plasma sheets are the supra-arcade downflows (SADs) that
sporadically enter the field of view. This work is also attempting
to ascertain what effect these SADs have on the flow of plasma at
different length scales. Contrast-enhanced images from five flares
observed with the Solar Dynamics Observatory/Atmospheric Imaging
Assembly (SDO/AIA) and Transition Region and Coronal Explorer (TRACE)
were used to construct velocity maps—in the plane of the sky—via
a Fourier local correlation tracking program. Power-law indices (α)
were calculated from the power spectral densities (PSDs) associated
with the intensity, kinetic energy, and enstrophy structures of these
plasma sheets. Velocity oscillations are observed to be approximately
three times stronger for velocities that are perpendicular (V <SUB>
ϕ </SUB>) instead of parallel (V <SUB> ρ </SUB>) to the magnetic
field’s direction. Four of the flares observed were used for producing
the following plasma sheet properties: kinetic energy PSD indices with
only V <SUB> ρ </SUB> were -0.15 ≤ α <SUB> ρ </SUB> ≤ 0.08,
kinetic energy PSD indices with only V <SUB> ϕ </SUB> were -1.59 ≤
α <SUB> ϕ </SUB> ≤ -1.46, kinetic energy PSD indices with both
velocities were -0.89 ≤ α ≤ -0.83, enstrophy PSD indices were
0.87 ≤ α ≤ 0.97, kinetic energy density was 16.6 km<SUP>2</SUP>
s<SUP>-2</SUP> ≤ ɛ ≤ 60.0 km<SUP>2</SUP> s<SUP>-2</SUP>, and
enstrophy density was 1.2 × 10<SUP>-6</SUP> s<SUP>-2</SUP> ≤ ω
≤ 2.8 × 10<SUP>-6</SUP> s<SUP>-2</SUP>.
---------------------------------------------------------
Title: "Building a Magnetic Skeleton of the Solar Corona: Towards
Better 3-D Constraints on the Coronal Magnetic Field
Authors: Malanushenko, Anna; Gibson, Sarah; Kucera, Therese; McKenzie,
David
2018cosp...42E2139M Altcode:
The energy stored in the solar magnetic field is what is powering many
violent explosive events in the solar atmosphere, or the corona. Some
of these events result in the coronal mass ejections (CME's) released
into the interplanetary space. The magnetic field in the solar corona
is therefore very important to know, yet it is very difficult to
measure. Most of the time it is modeled with the magnetic maps at
the solar surface used as boundary conditions. The magnetic maps on
the surface are therefore also important to know, yet the full vector
of the field on the surface is also difficult to measure. Once such
measurements are made, constructing a model capable of predicting
eruptive potential of a given region is on its own a complicated
task. One of the problems arising is that that the equations for
low-beta equilibria, which are often used to describe the coronal
field, do not, strictly speaking, work for the solar surface. In
short, we need better inputs to model the solar corona. The use of
non-magnetic and non-surface constraints on the magnetic field becomes
increasingly popular. For example, the paths of filaments can be used
to guide flux rope trajectories; the loops of active regions, seen
in extreme ultraviolet (EUV) can be used to obtain 3-D trajectories
of magnetic field lines and estimate electric currents flowing along
them. We are currently exploring ways to use other sources of data,
such as flows in prominences and coronal spectropolarimetric data, in a
similar fashion. I will talk about this work, and about our project of
aggregating many different sources of non-magnetic 3-D constraints on
the magnetic field. The resulting 'skeleton' can be used to constraint
global field models, or to validate models obtained in traditional
ways. We intend to develop a pipeline and assemble several skeletons
for several instances in time of the Sun, which we will then release
to community.
---------------------------------------------------------
Title: Current State of UV Spectro-Polarimetry and its Future
Direction
Authors: Ishikawa, Ryohko; Sakao, Taro; Katsukawa, Yukio; Hara,
Hirohisa; Ichimoto, Kiyoshi; Shimizu, Toshifumi; Kubo, Masahito;
Auchere, Frederic; De Pontieu, Bart; Winebarger, Amy; Kobayashi,
. Ken; Kano, Ryouhei; Narukage, Noriyuki; Trujillo Bueno, Javier;
Song, Dong-uk; Manso Sainz, Rafael; Asensio Ramos, Andres; Leenaarts,
Jorritt; Carlsson, Mats; Bando, Takamasa; Ishikawa, Shin-nosuke;
Tsuneta, Saku; Belluzzi, Luca; Suematsu, Yoshinori; Giono, Gabriel;
Yoshida, Masaki; Goto, Motoshi; Del Pino Aleman, Tanausu; Stepan,
Jiri; Okamoto, Joten; Tsuzuki, Toshihiro; Uraguchi, Fumihiro; Champey,
Patrick; Alsina Ballester, Ernest; Casini, Roberto; McKenzie, David;
Rachmeler, Laurel; Bethge, Christian
2018cosp...42E1564I Altcode:
To obtain quantitative information on the magnetic field in low beta
regions (i.e., upper chromosphere and above) has been increasingly
important to understand the energetic phenomena of the outer
solar atmosphere such as flare, coronal heating, and the solar wind
acceleration. In the UV range, there are abundant spectral lines that
originate in the upper chromosphere and transition region. However,
the Zeeman effect in these spectral lines does not give rise to easily
measurable polarization signals because of the weak magnetic field
strength and the larger Doppler broadening compared with the Zeeman
effect. Instead, the Hanle effect in UV lines is expected to be a
suitable diagnostic tool of the magnetic field in the upper atmospheric
layers. To investigate the validity of UV spectro-polarimetry and
the Hanle effect, the Chromospheric Lyman-Alpha Spectro-Polarimeter
(CLASP), which is a NASA sounding- rocket experiment, was launched at
White Sands in US on September 3, 2015. During its 5 minutes ballistic
flight, it successfully performed spectro-polarimetric observations
of the hydrogen Lyman-alpha line (121.57 nm) with an unprecedentedly
high polarization sensitivity of 0.1% in this wavelength range. CLASP
observed the linear polarization produced by scattering process in VUV
lines for the first time and detected the polarization signals which
indicate the operation of the Hanle effect. Following the success
of CLASP, we are confident that UV spectro-polarimetry is the way
to proceed, and we are planning the second flight of CLASP (CLASP2:
Chromospheric LAyer SpectroPolarimeter 2). For this second flight we
will carry out spectro-polarimetry in the Mg II h and k lines around
280 nm, with minimum modifications of the CLASP1 instrument. The linear
polarization in the Mg II k line is induced by scattering processes and
the Hanle effect, being sensitive to magnetic field strengths of 5 to 50
G. In addition, the circular polarizations in the Mg II h and k lines
induced by the Zeeman effect can be measurable in at least plage and
active regions. The combination of the Hanle and Zeeman effects could
help us to more reliably infer the magnetic fields of the upper solar
chromosphere. CLASP2 was selected for flight and is being developed for
launch in the spring of 2019.Based on these sounding rocket experiments
(CLASP1 and 2), we aim at establishing the strategy and refining the
instrument concept for future space missions to explore the enigmatic
atmospheric layers via UV spectro-polarimetry.
---------------------------------------------------------
Title: Wavefront error measurements and alignment of CLASP2 telescope
with a dual-band pass cold mirror coated primary mirror
Authors: Yoshida, Masaki; Song, Donguk; Ishikawa, Ryoko; Kano, Ryouhei;
Katsukawa, Yukio; Suematsu, Yoshinori; Narukage, Noriyuki; Kubo,
Masahito; Shinoda, Kazuya; Okamoto, Takenori J.; McKenzie, David E.;
Rachmeler, Laurel A.; Auchère, Frédéric; Trujillo Bueno, Javier
2018SPIE10699E..30Y Altcode:
"Chromospheric LAyer Spectro-Polarimeter (CLASP2)" is the next sounding
rocket experiment of the "Chromospheric Lyman-Alpha Spectro-Polarimeter
(CLASP)" that succeeded in observing for the first time the linear
polarization spectra in the hydrogen Lyman-α line (121.6 nm) and is
scheduled to be launched in 2019. In CLASP2, we will carry out full
Stokes-vector spectropolarimetric observations in the Mg ii h and k
lines near 280 nm with the spectro-polarimeter (SP), while imaging
observations in the Lyman-α line will be conducted with the slitjaw
optics (SJ). For the wavelength selection of CLASP2, the primary
mirror of the telescope uses a new dual-band pass cold mirror coating
targeting both at 121.6 nm and 280 nm. Therefore, we have to perform
again the alignment of the telescope after the installation of the
recoated primary mirror. Before unmounting the primary mirror from
the telescope structure, we measured the wave-front error (WFE) of the
telescope. The measured WFE map was consistent with what we had before
the CLASP flight, clearly indicating that the telescope alignment has
been maintained even after the flight. After the re-coated primary
mirror was installed the WFE was measured, and coma aberration was
found to be larger. Finally, the secondary mirror shim adjustments
were carried out based on the WFE measurements. In CLASP2 telescope,
we improved a fitting method of WFE map (applying 8th terms circular
Zernike polynomial fitting instead of 37th terms circular Zernike
fitting) and the improved method enables to achieve better performance
than CLASP telescope. Indeed, WFE map obtained after the final shim
adjustment indicated that the required specification (< 5.5 μm
RMS spot radius) that is more stringent than CLASP telescope was met.
---------------------------------------------------------
Title: Optical alignment of the high-precision UV spectro-polarimeter
(CLASP2)
Authors: Song, Donguk; Ishikawa, Ryohko; Kano, Ryouhei; Yoshida,
Masaki; Tsuzuki, Toshihiro; Uraguchi, Fumihiro; Shinoda, Kazuya;
Hara, Hirohisa; Okamoto, Takenori J.; Auchère, Frédéric; McKenzie,
David E.; Rachmeler, Laurel A.; Trujillo Bueno, Javier
2018SPIE10699E..2WS Altcode:
Chromospheric LAyer Spectro-Polarimeter (CLASP2) is our next sounding
rocket experiment after the success of Chromospheric Lyman-Alpha
Spectro-Polarimeter (CLASP1). CLASP2 is scheduled to launch in 2019,
and aims to achieve high precision measurements (< 0.1 %) of the
linear and circular polarizations in the Mg ii h and k lines near the
280 nm, whose line cores originate in the upper solar chromosphere. The
CLASP2 spectro-polarimeter follows very successful design concept of
the CLASP1 instrument with the minimal modification. A new grating was
fabricated with the same radius of curvature as the CLASP1 grating, but
with a different ruling density. This allows us to essentially reuse
the CLASP1 mechanical structures and layout of the optics. However,
because the observing wavelength of CLASP2 is twice longer than that
of CLASP1, a magnifier optical system was newly added in front of the
cameras to double the focal length of CLASP2 and to maintain the same
wavelength resolution as CLASP1 (0.01 nm). Meanwhile, a careful optical
alignment of the spectro-polarimeter is required to reach the 0.01 nm
wavelength resolution. Therefore, we established an efficient alignment
procedure for the CLASP2 spectro-polarimeter based on an experience
of CLASP1. Here, we explain in detail the methods for achieving the
optical alignment of the CLASP2 spectro-polarimeter and discuss our
results by comparing with the performance requirements.
---------------------------------------------------------
Title: Using DSG to build the capability of space weather forecasting
in deep space.
Authors: DeLuca, Edward; Golub, Leon; Korreck, Kelly; Savage, Sabrina
L.; McKenzie, David E.; Rachmeler, Laurel; Winebarger, Amy R.; Martens,
Petrus C.
2018tess.conf22002D Altcode:
The prospect of astronaut missions to deep space and off the
sun-earth line raises new challenges for space weather awareness
and forecasting. Combined efforts of the science and human flight
communities are needed to identify the requirements and identify
pathways that will allow us to address the requirements for protecting
human life and equipment, on a timescale consistent with the deep space
exploration program. <p class="p1" The Deep Space Gateway provides
a platform where we can develop, test and validate a combined space
weather instrumentation, analysis and forecasting system that can be
used when out of routine contact with near earth based assets. This
presentation will attempt to outline the bounds of the problem and start
the discussion about how to build an independent space weather program.
---------------------------------------------------------
Title: Measuring separator reconnection between emerging and existing
active regions using extreme ultraviolet imaging observations
Authors: McCarthy, Marika; Longcope, Dana; McKenzie, David E.;
Malanushenko, Anna V.
2018tess.conf20545M Altcode:
Magnetic reconnection must be occurring when new flux emerges into the
corona, in order that the flux become incorporated into the existing
corona. The most evident, and easily quantified, example of this
occurs when a new active region (AR) emerges in the vicinity of an
existing AR. In a study of such emergence observed by TRACE, Longcope et
al. (2005) found a delay of approximately 24 hours between the new AR
emerging and its reconnection with the field of the existing AR. This
turned out to be the only suitable event in the TRACE archive. Here
we apply the same method to events observed by SDO/AIA. Using high
time-cadence images in one EUV wavelength, such as 171 A, we make
a spatial/temporal stack plot of the region between the ARs by
extracting the pixel in a virtual slit. A persistent, bright streak
indicates a bright coronal loop connecting the newly emerging flux
to the existing AR. This loop must have been formed through a process
of coronal reconnection across the separator separating the two flux
systems. The rate at which new loops appear is used to compute the
rate of separator reconnection. The continuous, high-cadence data from
AIA permits flux transfer to be quantified for intervals exceeding 48
hours. <P />This work was supported by NASA's HGI program.
---------------------------------------------------------
Title: CisLunar Interchangeable Observatory for Heliophysics (CLIOH):
A Deep Space Gateway Solar Viewing Platform for Technology Development
and Research Payloads
Authors: Savage, S.; DeLuca, E.; Cheimets, P.; Golub, L.; Kobayashi,
K.; McKenzie, D.; Rachmeler, L.; Winebarger, A.
2018LPICo2063.3061S Altcode:
The Deep Space Gateway offers an unparalleled opportunity to test
and operate solar instrumentation in a radiation hard environment,
which can be achieved via an external pointing platform designed to
accommodate multiple interchangeable payloads.
---------------------------------------------------------
Title: The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS)
Authors: Winebarger, A. R.; Savage, S. L.; Kobayashi, K.; Champey,
P. R.; McKenzie, D. E.; Golub, L.; Testa, P.; Reeves, K.; Cheimets,
P.; Cirtain, J. W.; Walsh, R. W.; Bradshaw, S. J.; Warren, H.; Mason,
H. E.; Del Zanna, G.
2017AGUFMSH44A..06W Altcode:
For over four decades, X-ray, EUV, and UV spectral observations have
been used to measure physical properties of the solar atmosphere. At
wavelengths below 10 nm, however, observations of the solar corona
with simultaneous spatial and spectral resolution are limited,
and not since the late 1970's have spatially resolved solar X-ray
spectra been measured. Because the soft X-ray regime is dominated
by emission lines formed at high temperatures, X-ray spectroscopic
techniques yield insights to fundamental physical processes that are
not accessible by any other means. Using a novel implementation of
corrective optics, the Marshall Grazing Incidence X-ray Spectrometer
(MaGIXS) will measure, for the first time, the solar spectrum from 0.6-
2.4 nm with a 6 arcsec resolution over an 8 arcmin slit. The MaGIXS
mission will address on of the fundamental problems of coronal physics:
the nature of coronal heating. There are several observables in the
MaGIXS wavelength range that will constrain the heating frequency and
hence discriminate between competing coronal heating theories. In this
presentation, we will present the MaGIXS scientific motivation and
provide an update on instrument development. MaGIXS will be launched
from White Sands Missile Range in the summer of 2019.
---------------------------------------------------------
Title: High-cadence Hinode/XRT observations for studying coronal
events with very short timescales
Authors: McKenzie, David Eugene; Kobelski, Adam; Savage, Sabrina
2017SPD....4830406M Altcode:
The Hinode X-Ray Telescope’s capability for high time cadence
observations makes it an excellent tool for probing highly variable
conditions in the corona, including wave-like activity, dynamic
plasma motions, and short-duration transient events. XRT is capable
of producing images at cadences faster than one image per 10 seconds,
which is comparable to the energy release timescales, and/or ionization
evolution timescales, predicted by a range of models of coronal
activity. In the present work, we demonstrate XRT’s high-cadence
capability through observations of active region AR 10923 (2006
November), with cadences of 6-20 seconds. The image sequences, made
sequentially with multiple analysis filters, reveal many transient
brightenings (i.e., microflares), for which we derive heating and
cooling timescales. We also forward model the observed light curves to
estimate the temperature, density, filling factors, and lengths of the
observed loops. These estimates allow us to prioritize different heating
mechanisms, and to better understand the unresolved structures within
the observations. This study provides a test of capabilities, which
have still not yet been fully utilized by the ten-year-old Hinode X-Ray
Telescope, and thus provides a starting point for future investigations
of short-timescale/high-frequency variations in coronal X-ray intensity.
---------------------------------------------------------
Title: CLASP2: The Chromospheric LAyer Spectro-Polarimeter
Authors: Rachmeler, Laurel A.; McKenzie, D. E.; Ishikawa, R.;
Trujillo-Bueno, J.; Auchere, F.; Kobayashi, K.; Winebarger, A.;
Bethge, C.; Kano, R.; Kubo, M.; Song, D.; Narukage, N.; Ishikawa, S.;
De Pontieu, B.; Carlsson, M.; Yoshida, M.; Belluzzi, L.; Stepan, J.;
del Pino Alemán, T.; Alsina Ballester, E.; Asensio Ramos, A.
2017shin.confE..79R Altcode:
We present the instrument, science case, and timeline of the CLASP2
sounding rocket mission. The successful CLASP (Chromospheric Lyman-Alpha
Spectro-Polarimeter) sounding rocket flight in 2015 resulted in
the first-ever linear polarization measurements of solar hydrogen
Lyman-alpha line, which is sensitive to the Hanle effect and can be used
to constrain the magnetic field and geometric complexity of the upper
chromosphere. Ly-alpha is one of several upper chromospheric lines that
contain magnetic information. In the spring of 2019, we will re-fly
the modified CLASP telescope to measure the full Stokes profile of Mg
II h & k near 280 nm. This set of lines is sensitive to the upper
chromospheric magnetic field via both the Hanle and the Zeeman effects.
---------------------------------------------------------
Title: A Bayesian Approach to Period Searching in Solar Coronal Loops
Authors: Scherrer, Bryan; McKenzie, David
2017ApJ...837...24S Altcode:
We have applied a Bayesian generalized Lomb-Scargle period searching
algorithm to movies of coronal loop images obtained with the Hinode
X-ray Telescope (XRT) to search for evidence of periodicities that
would indicate resonant heating of the loops. The algorithm makes as
its only assumption that there is a single sinusoidal signal within
each light curve of the data. Both the amplitudes and noise are
taken as free parameters. It is argued that this procedure should
be used alongside Fourier and wavelet analyses to more accurately
extract periodic intensity modulations in coronal loops. The data
analyzed are from XRT Observation Program #129C: “MHD Wave Heating
(Thin Filters),” which occurred during 2006 November 13 and focused
on active region 10293, which included coronal loops. The first data
set spans approximately 10 min with an average cadence of 2 s, 2″
per pixel resolution, and used the Al-mesh analysis filter. The second
data set spans approximately 4 min with a 3 s average cadence, 1″ per
pixel resolution, and used the Al-poly analysis filter. The final data
set spans approximately 22 min at a 6 s average cadence, and used the
Al-poly analysis filter. In total, 55 periods of sinusoidal coronal
loop oscillations between 5.5 and 59.6 s are discussed, supporting
proposals in the literature that resonant absorption of magnetic waves
is a viable mechanism for depositing energy in the corona.
---------------------------------------------------------
Title: An Exploration of Heating Mechanisms in a Supra-arcade Plasma
Sheet Formed after a Coronal Mass Ejection
Authors: Reeves, Katharine K.; Freed, Michael S.; McKenzie, David E.;
Savage, Sabrina L.
2017ApJ...836...55R Altcode: 2017arXiv170103497R
We perform a detailed analysis of the thermal structure of the
region above the post-eruption arcade for a flare that occurred on
2011 October 22. During this event, a sheet of hot plasma is visible
above the flare loops in the 131 Å bandpass of the Atmospheric Imaging
Assembly (AIA) on the Solar Dynamics Observatory. Supra-arcade downflows
(SADs) are observed traveling sunward through the post-eruption plasma
sheet. We calculate differential emission measures using the AIA data
and derive an emission measure weighted average temperature in the
supra-arcade region. In areas where many SADs occur, the temperature
of the supra-arcade plasma tends to increase, while in areas where no
SADs are observed, the temperature tends to decrease. We calculate
the plane-of-sky velocities in the supra-arcade plasma and use them
to determine the potential heating due to adiabatic compression and
viscous heating. Of the 13 SADs studied, 10 have noticeable signatures
in both the adiabatic and the viscous terms. The adiabatic heating due
to compression of plasma in front of the SADs is on the order of 0.1-0.2
MK/s, which is similar in magnitude to the estimated conductive cooling
rate. This result supports the notion that SADs contribute locally to
the heating of plasma in the supra-arcade region. We also find that
in the region without SADs, the plasma cools at a rate that is slower
than the estimated conductive cooling, indicating that additional
heating mechanisms may act globally to keep the plasma temperature high.
---------------------------------------------------------
Title: Numerical Simulations of Plasma Dynamics in the Vicinity of
a Retracting Flux Tube
Authors: Scott, Roger B.; Longcope, Dana W.; McKenzie, David E.
2016ApJ...831...94S Altcode:
In a previous paper, we presented an analytical, zero-β model for
supra-arcade downflows in which a retracting flux tube deforms the
surrounding magnetic field, constricting the flow of plasma along
affected field lines and, in some cases, forcing the plasma to exhibit
collimated shocks. Here we present a numerical simulation based on
the same model construction—a retracting flux tube is treated as
a rigid boundary around which the plasma is forced to flow and the
magnetic field and plasma evolve according to the governing equations
of magnetohydrodynamics. We find that the collimated shocks described
in our previous study are recovered for plasma β in the range of
0 ≤ β ≲ 1, while for 1 ≲ β the behavior is similar to the
simpler hydrodynamic case, with classical bow shocks forming when
the acoustic Mach number approaches or exceeds unity. Furthermore, we
find that while the plasma β is important for identifying the various
types of behaviors, more important still is the Alfvén Mach number,
which, if large, implies that the bulk kinetic energy of the fluid
exceeds the internal energy of the magnetic field, thereby leading to
the formation of unconfined, fast-mode magnetosonic shocks, even in
the limit of small β.
---------------------------------------------------------
Title: Chromospheric LAyer SpectroPolarimeter (CLASP2)
Authors: Narukage, Noriyuki; McKenzie, David E.; Ishikawa, Ryoko;
Trujillo-Bueno, Javier; De Pontieu, Bart; Kubo, Masahito; Ishikawa,
Shin-nosuke; Kano, Ryouhei; Suematsu, Yoshinori; Yoshida, Masaki;
Rachmeler, Laurel A.; Kobayashi, Ken; Cirtain, Jonathan W.; Winebarger,
Amy R.; Asensio Ramos, Andres; del Pino Aleman, Tanausu; Štępán,
Jiri; Belluzzi, Luca; Larruquert, Juan Ignacio; Auchère, Frédéric;
Leenaarts, Jorrit; Carlsson, Mattias J. L.
2016SPIE.9905E..08N Altcode:
The sounding rocket Chromospheric Lyman-Alpha SpectroPolarimeter
(CLASP) was launched on September 3rd, 2015, and successfully detected
(with a polarization accuracy of 0.1 %) the linear polarization signals
(Stokes Q and U) that scattering processes were predicted to produce
in the hydrogen Lyman-alpha line (Lyα 121.567 nm). Via the Hanle
effect, this unique data set may provide novel information about the
magnetic structure and energetics in the upper solar chromosphere. The
CLASP instrument was safely recovered without any damage and we have
recently proposed to dedicate its second flight to observe the four
Stokes profiles in the spectral region of the Mg II h and k lines
around 280 nm; in these lines the polarization signals result from
scattering processes and the Hanle and Zeeman effects. Here we describe
the modifications needed to develop this new instrument called the
"Chromospheric LAyer SpectroPolarimeter" (CLASP2).
---------------------------------------------------------
Title: An Evaluation of Motions Found in Multiple Supra-Arcade Plasma
Sheets with Local Correlation Tracking
Authors: Freed, Michael; McKenzie, David Eugene
2016SPD....4730501F Altcode:
Plasma sheets can be seen in the corona above arcade loops that form
shortly after the eruption phase of a solar flare. These structures
are considered to be the location where current sheets can form,
which are a key component for magnetic reconnection to take place. The
objective of this study is to quantify the motion seen in these plasma
sheets and to determine how these characteristics might vary over
multiple length scales. We use contrast-enhanced EUV observations
of five different plasma sheets to construct velocity maps of plasma
motion — in the plane of the sky — via a Fourier local correlation
tracking program. These derived velocities were then used to calculate
angle-integrated power spectral density of intensity, kinetic energy,
and enstrophy to determine if any self-similarity exists. The derived
velocity fields also allowed for measurements of the kinetic energy
density, enstrophy density, and magnetic diffusivity. We will also
present the first reported observational evidence of Kelvin-Helmholtz
instabilities forming at the interface of supra-arcade downflows (SADs)
and the surrounding supra-arcade plasma.
---------------------------------------------------------
Title: Inferring the Magnetohydrodynamic Structure of Solar Flare
Supra-Arcade Plasmas from a Data-assimilated Field Transport Model
Authors: Scott, Roger B.; McKenzie, David E.; Longcope, Dana W.
2016ApJ...819...56S Altcode:
Supra-arcade fans are highly dynamic structures that form in the
region above post-reconnection flare arcades. In these features the
plasma density and temperature evolve on the scale of a few seconds,
despite the much slower dynamics of the underlying arcade. Further,
the motion of supra-arcade plasma plumes appears to be inconsistent
with the low-beta conditions that are often assumed to exist in the
solar corona. In order to understand the nature of these highly debated
structures, it is, therefore, important to investigate the interplay
of the magnetic field with the plasma. Here we present a technique for
inferring the underlying magnetohydrodynamic processes that might lead
to the types of motions seen in supra-arcade structures. Taking as a
case study the 2011 October 22 event, we begin with extreme-ultraviolet
observations and develop a time-dependent velocity field that is
consistent with both continuity and local correlation tracking. We then
assimilate this velocity field into a simplified magnetohydrodynamic
simulation, which deals simultaneously with regions of high and low
signal-to-noise ratio, thereby allowing the magnetic field to evolve
self-consistently with the fluid. Ultimately, we extract the missing
contributions from the momentum equation in order to estimate the
relative strength of the various forcing terms. In this way we are
able to make estimates of the plasma beta, as well as predict the
spectral character and total power of Alfvén waves radiated from the
supra-arcade region.
---------------------------------------------------------
Title: Analysis of Flows inside Quiescent Prominences as Captured
by Hinode/Solar Optical Telescope
Authors: Freed, M. S.; McKenzie, D. E.; Longcope, D. W.; Wilburn, M.
2016ApJ...818...57F Altcode: 2016arXiv160203821F
Developing an understanding of how magnetic fields can become entangled
in a prominence is important for predicting a possible eruption. This
work investigates the kinetic energy and vorticity associated with
plasma motion residing inside quiescent prominences (QPs). These plasma
flow characteristics can be utilized to improve our understanding of how
the prominence maintains a stable magnetic field configuration. Three
different contrast-enhanced solar prominence observations from
Hinode/Solar Optical Telescope were used to construct velocity
maps—in the plane of the sky—via a Fourier local correlation
tracking program. The resulting velocities were then used to perform the
first-ever analysis of the two-dimensional kinetic energy and enstrophy
spectra of a prominence. Enstrophy is introduced here as a means of
quantifying the vorticity that has been observed in many QPs. The
kinetic energy power spectral density (PSD) produced indices ranging
from -1.00 to -1.60. There was a consistent anisotropy in the kinetic
energy spectrum of all three prominences examined. Examination of the
intensity PSD reveals that a different scaling relationship exists
between the observed prominence structure and velocity maps. All of
the prominences exhibited an inertial range of at least 0.8≤slant
k≤slant 2.0 {rads} {{Mm}}<SUP>-1</SUP>. Quasi-periodic oscillations
were also detected in the centroid of the velocity distributions for one
prominence. Additionally, a lower limit was placed on the kinetic energy
density (ɛ ∼ 0.22-7.04 {{km}}<SUP>2</SUP> {{{s}}}<SUP>-2</SUP>)
and enstrophy density (ω ∼ 1.43-13.69 × \quad {10}<SUP>-16</SUP>
{{{s}}}<SUP>-2</SUP>) associated with each prominence.
---------------------------------------------------------
Title: Calibration of Hinode/XRT for Coalignment
Authors: Yoshimura, Keiji; McKenzie, David E.
2015SoPh..290.2355Y Altcode: 2015SoPh..tmp..106Y
We present coalignment calibration procedures for the X-ray Telescope
(XRT) onboard the Hinode satellite. We performed not only an XRT
stand-alone calibration, but also cross calibration using data from
the Helioseismic and Magnetic Imager (HMI) and the Atmospheric Imaging
Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). Several
new methods we describe here may also be useful for the coalignment
calibration of other instruments. We have developed a database of
coalignment coefficients and software to access it, so that all XRT
images can be easily and accurately overlaid onto the images from
other instruments, especially AIA and HMI.
---------------------------------------------------------
Title: How Can We Recognize Tearing Mode Signatures When They Occur?
Authors: McKenzie, David E.
2015shin.confE..10M Altcode:
The tearing mode instability offers a route to accelerated reconnection
in sheared magnetic fields, including in current sheets. Many 2D
treatments of tearing-unstable current sheets reveal populations of
magnetic islands, and suggest that the evolutions/distributions of
these 2D islands should tell us something about how reconnection is
progressing. But how will we recognize the islands in 3D? In recent
years observational studies-both in situ and remote sensing-claim to
have detected islands; some of these reports are promising. In this
'scene-setting' talk, I will review the observations, including some
very recent observations from IRIS, with the objective of sparking a
discussion about observable features of the tearing mode, logical tests
for the presence of the tearing mode, and ultimately empirical studies
of the conditions controlling reconnection within the current sheet.
---------------------------------------------------------
Title: Hinode/XRT Measurements of Turbulent Velocities in Flare
Plasma Sheets
Authors: McKenzie, David; Freed, Michael
2015TESS....120310M Altcode:
The turbulent, dynamic motions that we observe in the hot plasma
surrounding current sheets very likely distort the embedded magnetic
fields, resulting in reduced length scales and locally augmented
resistivities. These conditions may help to accelerate and/or prolong
the reconnection in solar flares. Although we cannot as yet measure
directly the magnetic fields in the corona, the velocity fields within
the flare plasma sheets provide a means to study the conditions
that control the spatial and temporal scales of reconnection, in
the locations and at the times that are relevant to structuring the
magnetic fields.The plasma sheets are observable in many flares in
soft X-ray and EUV wavelengths, due to their high temperatures. For
two recent flares observed with the Hinode X-Ray Telescope (XRT), we
have analyzed the velocity fields with a local correlation tracking
technique, and compared to measurements from the Solar Dynamics
Observatory Atmospheric Imaging Assembly (SDO/AIA).This work is
supported by NASA under contract NNM07AB07C with the Smithsonian
Astrophysical Observatory, and by grant NNX14AD43G.
---------------------------------------------------------
Title: Spectral Analysis of Velocities in Quiescent Prominences
Observed with Hinode
Authors: McKenzie, David; Freed, Michael
2015TESS....130305M Altcode:
High-resolution observations of solar prominences, especially with the
Solar Optical Telescope (SOT) on Hinode, reveal the presence of upward
and downward flows consistent with convection, at length scales that
were not accessible with previous telescopes. Since prominences are
magnetic structures, the strength and arrangement of their magnetic
fields are crucial for determining whether a given prominence will
erupt into a coronal mass ejection. Convective flows can twist and
tangle those magnetic fields. However, the magnetic fields within the
prominences are extremely difficult to measure; therefore measurements
of the dynamics of the magnetized plasma in prominences, and the
balance between magnetic and gas-pressure forces, are valuable for
understanding how these apparently stable structures can evolve to
become suddenly eruptive. We will show our findings from analysis
of the dynamics in a few solar prominences using local correlation
tracking, and make estimates of the kinetic energy, diffusivity, and
vorticity.This work is supported by NASA under contract NNM07AB07C
with the Smithsonian Astrophysical Observatory.
---------------------------------------------------------
Title: On the Magnetohydrodynamics of Supra-Arcade Fan Structures
Authors: Scott, Roger B.; McKenzie, David; Longcope, Dana
2015TESS....140705S Altcode:
Supra-Arcade Fan Structures are highly dynamic regions that form above
post-reconnection arcades. In these regions, the plasma density and
thermal structure evolve on the scale of a few seconds, despite the
much slower dynamics of the underlying arcade. Further, the motion
of supra-arcade plasma plumes appears to be inconsistent with the
low-beta conditions that many authors assume to exist in the solar
corona. In order to understand the nature of these highly debated
structures it is, therefore, important to investigate the interplay
of the magnetic field with the plasma. Here we present a technique
for inferring the underlying MagnetoHydroDynamic processes that might
lead to the types of motions seen in supra-arcade structures. We begin
with EUV observations and develop a time dependent velocity field
that is consistent with both mass conservation and local correlation
tracking. We then assimilate this velocity field into a simplified
MHD code, which deals simultaneously with regions of high and low SNR,
thereby allowing the magnetic field to evolve self-consistently with
the fluid. Ultimately, we extract the missing contributions from the
underlying momentum equation in order to estimate the relative strength
of forcing terms. In this way we are able to make estimates of the
plasma beta as well as predicting the spectral character of radiated
Alfvén waves. It is our hope that this work will help to improve
our understanding of the energy balance in these complex regions
and, thereby, contribute to our knowledge of the solar corona as a
whole. This work is supported by NASA under contract NNM07AB07C with
the Smithsonian Astrophysical Observatory, and by grant NNX14AD43G.
---------------------------------------------------------
Title: Three-Year Global Survey of Coronal Null Points from
Potential-Field-Source-Surface (PFSS) Modeling and Solar Dynamics
Observatory (SDO) Observations
Authors: Freed, M. S.; Longcope, D. W.; McKenzie, D. E.
2015SoPh..290..467F Altcode: 2014SoPh..tmp..136F; 2014arXiv1410.4493F
This article compiles and examines a comprehensive coronal
magnetic-null-point survey created by potential-field-source-surface
(PFSS) modeling and Solar Dynamics Observatory/Atmospheric Imaging
Assembly (SDO/AIA) observations. The locations of 582 potential magnetic
null points in the corona were predicted from the PFSS model between
Carrington Rotations (CR) 2098 (June 2010) and 2139 (July 2013). These
locations were manually inspected, using contrast-enhanced SDO/AIA
images in 171 Å at the East and West solar limb, for structures
associated with nulls. A Kolmogorov-Smirnov (K-S) test showed a
statistically significant difference between observed and predicted
latitudinal distributions of null points. This finding is explored
further to show that the observability of null points could be affected
by the Sun's asymmetric hemisphere activity. Additional K-S tests show
no effect on observability related to eigenvalues associated with the
fan and spine structure surrounding null points or to the orientation
of the spine. We find that approximately 31 % of nulls obtained from
the PFSS model were observed in SDO/AIA images at one of the solar
limbs. An observed null on the East solar limb had a 51.6 % chance
of being observed on the West solar limb. Predicted null points going
back to CR 1893 (March 1995) were also used for comparing radial and
latitudinal distributions of nulls to previous work and to test for
correlation of solar activity to the number of predicted nulls.
---------------------------------------------------------
Title: Temperature and Electron Density Diagnostics of a
Candle-flame-shaped Flare
Authors: Guidoni, S. E.; McKenzie, D. E.; Longcope, D. W.; Plowman,
J. E.; Yoshimura, K.
2015ApJ...800...54G Altcode:
Candle-flame-shaped flares are archetypical structures that provide
indirect evidence of magnetic reconnection. A flare resembling Tsuneta's
famous 1992 candle-flame flare occurred on 2011 January 28; we present
its temperature and electron density diagnostics. This flare was
observed with Solar Dynamics Observatory/Atmospheric Imaging Assembly
(SDO/AIA), Hinode/X-Ray Telescope (XRT), and Solar Terrestrial Relations
Observatory Ahead (STEREO-A)/Extreme Ultraviolet Imager, resulting
in high-resolution, broad temperature coverage, and stereoscopic
views of this iconic structure. The high-temperature images reveal
a brightening that grows in size to form a tower-like structure at
the top of the posteruption flare arcade, a feature that has been
observed in other long-duration events. Despite the extensive work on
the standard reconnection scenario, there is no complete agreement
among models regarding the nature of this high-intensity elongated
structure. Electron density maps reveal that reconnected loops that are
successively connected at their tops to the tower develop a density
asymmetry of about a factor of two between the two legs, giving the
appearance of "half-loops." We calculate average temperatures with a
new fast differential emission measure (DEM) method that uses SDO/AIA
data and analyze the heating and cooling of salient features of the
flare. Using STEREO observations, we show that the tower and the
half-loop brightenings are not a line-of-sight projection effect of
the type studied by Forbes & Acton. This conclusion opens the door
for physics-based explanations of these puzzling, recurrent solar flare
features, previously attributed to projection effects. We corroborate
the results of our DEM analysis by comparing them with temperature
analyses from Hinode/XRT.
---------------------------------------------------------
Title: The Space Public Outreach Team (SPOT): Adapting a successful
outreach programme to a new region
Authors: Williamson, K.; Jardins, A. D.; Grimberg, I.; Larson, S. L.;
Key, J.; Larson, M. B.; Heatherly, S. A.; McKenzie, D.; Littenberg,
T. B.
2014CAPJ...16....8W Altcode:
The Space Public Outreach Team (SPOT) recruits and trains
undergraduate ambassadors from all disciplines to deliver astronomy
and space-science-themed interactive presentations. They deliver these
presentations to primary and secondary schools and organisations across
the state of Montana, USA. SPOT was started in 1996 by physics graduate
students at Montana State University, USA, and it has grown to reach
an average of 10 000 students per year for a low institutional cost of
less than five dollars (four euros) per student. In the last year, the
Montana SPOT model has been adopted in the state of West Virginia. The
West Virginia SPOT programme also shows great potential, with eleven
ambassadors trained to give two new feature presentations, reaching
over 2600 students. In this paper, we describe how the Montana SPOT
model works in practice and discuss how this model was adapted with new
resources, and for a new audience, such that others may also adapt the
programme to inspire space science interest for their own particular
setting. We invite these groups to plug into the SPOT brand to broaden
the impact of astronomy and space programmes and applications in their
own region.
---------------------------------------------------------
Title: Characterizing Turbulent Flow in Quiescent Prominences
Authors: Freed, M.; Wilburn, M.; McKenzie, D. E.
2014AGUFMSH11D..01F Altcode:
Understanding the motion of plasma in quiescent prominences is
important in determining how the magnetic field structure can become
entangled to trigger eruptions. Hinode/Solar Optical Telescope (SOT)
observations have already demonstrated the existence of convective
flows and Kelvin-Helmholtz instabilities around the plume component
inside these prominences. Our research uses the same observations to
make quantitative measurements of the turbulent diffusive flows in
these coronal structures. Fourier local correlation tracking (FLCT)
is used to derive velocity fields from SOT observations of prominence
plasma sheets. Analysis of these velocity fields in turn provides a
measurement of the temporal and/or spatial length scales associated
with the energy dissipation and diffusivity.
---------------------------------------------------------
Title: Thermal Structure and Dynamics in Supra-arcade Downflows and
Flare Plasma Sheets
Authors: Reeves, K.; Hanneman, W.; Freed, M.; McKenzie, D. E.
2014AGUFMSM44B..01R Altcode:
During a long duration solar flare, a hot plasma sheet is commonly
formed above the flare loops. Often produced within this sheet are
down-flowing voids referred to as supra-arcade downflows, thought to
be the products of a patchy reconnection process. Models differ on the
question of whether the downflows should be hotter than the surrounding
plasma or not. We use imaging data from Hinode/XRT and SDO/AIA to
determine the thermal structure of the plasma sheet and downflows. We
find that the temperatures of the plasma within the downflows are either
roughly the same as or lower than the surrounding fan plasma. This
result implies that a mechanism for forming the voids that involves a
sunward directed hydrodynamic shock pattern combined with perpendicular
magnetic shock is unlikely. Additionally, we use the high cadence AIA
data to trace the velocity fields in these regions through the use of
a local correlation tracking algorithm. Through these measurements, we
can determine areas of diverging velocity fields, as well as velocity
shear fields and correlate them with temperature changes in order to
understand the heating mechanisms in the plasma sheet. This work is
supported by under contract SP02H1701R from Lockheed-Martin to SAO,
contract NNM07AB07C from NASA to SAO and NASA grant numbers NNX13AG54G
and NNX14AD43G
---------------------------------------------------------
Title: Forward Modeling Transient Brightenings and Microflares around
an Active Region Observed with Hi-C
Authors: Kobelski, Adam R.; McKenzie, David E.
2014ApJ...794..119K Altcode: 2014arXiv1408.5440K
Small-scale flare-like brightenings around active regions are among
the smallest and most fundamental of energetic transient events in
the corona, providing a testbed for models of heating and active
region dynamics. In a previous study, we modeled a large collection
of these microflares observed with Hinode/X-Ray Telescope (XRT) using
EBTEL and found that they required multiple heating events, but could
not distinguish between multiple heating events on a single strand,
or multiple strands each experiencing a single heating event. We
present here a similar study, but with extreme-ultraviolet data of
Active Region 11520 from the High Resolution Coronal Imager (Hi-C)
sounding rocket. Hi-C provides an order of magnitude improvement to
the spatial resolution of XRT, and a cooler temperature sensitivity,
which combine to provide significant improvements to our ability to
detect and model microflare activity around active regions. We have
found that at the spatial resolution of Hi-C (≈0.”3), the events
occur much more frequently than expected (57 events detected, only 1
or 2 expected), and are most likely made from strands of the order
of 100 km wide, each of which is impulsively heated with multiple
heating events. These findings tend to support bursty reconnection as
the cause of the energy release responsible for the brightenings.
---------------------------------------------------------
Title: Quiescent Reconnection Rate Between Emerging Active Regions
and Preexisting Field, with Associated Heating: NOAA AR 11112
Authors: Tarr, Lucas A.; Longcope, Dana W.; McKenzie, David E.;
Yoshimura, Keiji
2014SoPh..289.3331T Altcode: 2013arXiv1311.3705T; 2014SoPh..tmp....1T
When magnetic flux emerges from beneath the photosphere, it displaces
the preexisting field in the corona, and a current sheet generally forms
at the boundary between the old and new magnetic domains. Reconnection
in the current sheet relaxes this highly stressed configuration to
a lower energy state. This scenario is most familiar and most often
studied in flares, where the flux transfer is rapid. We present here
a study of steady, quiescent flux transfer occurring at a rate three
orders of magnitude lower than that in a large flare. In particular,
we quantify the reconnection rate and the related energy release that
occurred as the new polarity emerged to form NOAA Active Region 11112
(SOL16 October 2010T00:00:00L205C117) within a region of preexisting
flux. A bright, low-lying kernel of coronal loops above the emerging
polarity, observed with the Atmospheric Imaging Assembly onboard the
Solar Dynamics Observatory and the X-ray Telescope onboard Hinode,
originally showed magnetic connectivity only between regions of newly
emerged flux when overlaid on magnetograms from the Helioseismic and
Magnetic Imager. Over the course of several days, this bright kernel
advanced into the preexisting flux. The advancement of an easily
visible boundary into the old flux regions allows measuring the rate
of reconnection between old and new magnetic domains. We compare the
reconnection rate with the inferred heating of the coronal plasma. To
our knowledge, this is the first measurement of steady, quiescent
heating related to reconnection. We determined that the newly emerged
flux reconnects at a fairly steady rate of 0.38×10<SUP>16</SUP> Mx
s<SUP>−1</SUP> over two days, while the radiated power varies between
(2 - 8)×10<SUP>25</SUP> erg s<SUP>−1</SUP> over the same time. We
found that as much as 40 % of the total emerged flux at any given
time may have reconnected. The total amounts of transferred flux (∼
1×10<SUP>21</SUP> Mx) and radiated energy (∼ 7.2×10<SUP>30</SUP>
ergs) are comparable to that of a large M- or small X-class flare,
but are stretched out over 45 hours.
---------------------------------------------------------
Title: Calibrating Data from the Hinode/X-Ray Telescope and Associated
Uncertainties
Authors: Kobelski, Adam R.; Saar, Steven H.; Weber, Mark A.; McKenzie,
David E.; Reeves, Katharine K.
2014SoPh..289.2781K Altcode: 2013arXiv1312.4850K; 2014SoPh..tmp...27K
The X-Ray Telescope (XRT) onboard the Hinode satellite, launched 23
September 2006 by the Japan Aerospace Exploration Agency (JAXA), is a
joint mission of Japan, the United States, and the United Kingdom to
study the solar corona. In particular, XRT was designed to study solar
plasmas with temperatures between 1 and 10 MK with ≈ 1″ pixels
(≈ 2″ resolution). Prior to analysis, the data product from this
instrument must be properly calibrated and data values quantified to
accurately assess the information contained within. We present here
the standard methods of calibration for these data. The calibration
was performed on an empirical basis that uses the least complicated
correction that accurately describes the data while suppressing
spurious features. By analyzing the uncertainties remaining in the
data after calibration, we conclude that the procedure is successful,
because the remaining uncertainty after calibration is dominated by
photon noise. This calibration software is available in the SolarSoft
software library.
---------------------------------------------------------
Title: Advection of Magnetic Field Lines in Supra-Arcade Fan
Structures
Authors: Scott, Roger B.; Freed, Michael; McKenzie, David Eugene;
Longcope, Dana
2014AAS...22432344S Altcode:
Recent attempts to characterize the apparent motion of supra-arcade
fan structures have revealed bulk velocity and displacement spectra
that may give insights into the energy distribution in supra-arcade
plasma sheets. In order to form a more complete picture of the energy
balance in these structures it is important to understand the magnetic
field on a similar scale. In this work we used velocity maps found
through local correlation tracking (LCT) as source functions for a 2D,
time-dependent, ideal induction equation. We began with an assumed
initial configuration and then evolved the magnetic field in order
to maintain the frozen-in condition. We then characterized the energy
deposition into the field as well as the field strength spectrum and
several other quantities of interest. It is our hope that this study
will serve to improve our understanding of the interplay between the
plasma and the magnetic field in the supra-arcade region.
---------------------------------------------------------
Title: The Heating of Active Regions Using Active Region Transient
Brightenings Observed with XRT and Hi-C
Authors: Kobelski, Adam; McKenzie, David Eugene
2014AAS...22431201K Altcode:
Active region transient brightentings (ARTBs) are among the smallest
and most fundamental of energetic transient events in the corona; as
such, they provide a testbed for models of heating and active region
dynamics. We have modeled a large collection of ARTBs observed with
Hinode/XRT and with Hi-C as both (a) multi-stranded loops and (b)
monolithic loops which experience multiple heating events, to explore
the energetic ramifications and characteristics in active region
dynamics. Even for these small, short-lived transients, our modeling
indicates that multiple heating events are required for each ARTB. We
compare the quality of model fits for two different temporal envelopes
of the heating function, and discuss whether the results more strongly
favor nanoflare or wave-absorption heating.
---------------------------------------------------------
Title: Plasma Dynamics Above Solar Flare Soft X-Ray Loop Tops
Authors: Doschek, G. A.; McKenzie, D. E.; Warren, H. P.
2014ApJ...788...26D Altcode:
We measure non-thermal motions in flare loop tops and above the loop
tops using profiles of highly ionized spectral lines of Fe XXIV and Fe
XXIII formed at multimillion-degree temperatures. Non-thermal motions
that may be due to turbulence or multiple flow regions along the line of
sight are extracted from the line profiles. The non-thermal motions are
measured for four flares seen at or close to the solar limb. The profile
data are obtained using the Extreme-ultraviolet Imaging Spectrometer on
the Hinode spacecraft. The multimillion-degree non-thermal motions are
between 20 and 60 km s<SUP>-1</SUP> and appear to increase with height
above the loop tops. Motions determined from coronal lines (i.e., lines
formed at about 1.5 MK) tend to be smaller. The multimillion-degree
temperatures in the loop tops and above range from about 11 MK to 15 MK
and also tend to increase with height above the bright X-ray-emitting
loop tops. The non-thermal motions measured along the line of sight,
as well as their apparent increase with height, are supported by
Solar Dynamics Observatory Atmospheric Imaging Assembly measurements
of turbulent velocities in the plane of the sky.
---------------------------------------------------------
Title: Empirical Study of Turbulent Diffusion in Flare Plasma Sheets
Authors: McKenzie, David Eugene; Freed, Michael
2014AAS...22410401M Altcode:
Velocity fields in the hot (>10 MK) plasma sheets above post-eruption
flare arcades have the hallmarks of turbulent flow. Tracking and
measuring these velocity fields enables empirical estimation of
transport parameters, e.g. turbulent diffusivity, that are important
for determining the spectrum of length scales present in the plasma
sheet. These transport parameters thus help to set the rate of magnetic
reconnection, and may help us to understand how reconnection can be
triggered, accelerated, and prolonged in eruptive flares. In this work
we show measurements, for the first time, of transport parameters in
flare plasma sheets, enabled by high-resolution observations from SDO
and local correlation tracking.
---------------------------------------------------------
Title: Findings from a Three Year Survey of Coronal Null Points
Authors: Freed, Michael; Longcope, Dana; McKenzie, David Eugene
2014AAS...22432329F Altcode:
We report the findings from a comprehensive coronal magnetic null point
survey created by Potential Field Source Surface (PFSS) modeling &
Solar Dynamic Observatory/Atmospheric Imaging Assembly (SDO/AIA)
observations. Locations of magnetic null points in the corona were
predicted from the PFSS model from Carrington Rotation 2098 to 2139
and manually compared to contrast enhanced SDO/AIA images in 171
angstroms. Statistical results will be presented that illustrate
the characteristics associated with the observed and predicted null
points. These characteristics include the radial & latitudinal
distribution; eigenvalues associated with null point structure; and
the effect spine orientation has on observability.
---------------------------------------------------------
Title: Non-thermal Motions in and Above Flare Loop Tops Measured by
the Extreme-ultraviolet Imaging Spectrometer (EIS) on Hinode
Authors: Doschek, George A.; McKenzie, David Eugene; Warren, Harry P
2014AAS...22411105D Altcode:
The plasma volume above the soft X-ray emitting loop tops is of
particular interest for studying the formation of flare loops. We
present EIS observations of non-thermal motions (turbulence) determined
from spectral line profiles of Fe XXIII and Fe XXIV ions for three
well-observed flares near the solar limb. We compare the non-thermal
motions at temperatures near 10 MK with the motions along the same
lines-of-sight determined from lines of coronal ions such as Fe XII, Fe
XIV, and Fe XV formed at 1-2 MK. The take-away is that the non-thermal
motions obtained from Fe XXIII and Fe XXIV lines increase with height
towards the reconnection region, up to speeds of about 50-60 km/s
for the largest heights that we can observe. The implication is that
considerable plasma heating occurs outside the reconnection region. In
addition, we discuss the implications of results obtained for flares
from earlier X-ray Yohkoh observations of line profiles of Fe XXV and
Ca XIX on the current results from EIS and AIA. Fe XXV is formed at
significantly higher temperatures than any strong flare EUV spectral
line observed by EIS or by imaging telescopes such as AIA or TRACE. This
work is supported by NASA grants.
---------------------------------------------------------
Title: Modeling Active Region Transient Brightenings Observed with
X-Ray Telescope as Multi-stranded Loops
Authors: Kobelski, Adam R.; McKenzie, David E.; Donachie, Martin
2014ApJ...786...82K Altcode: 2014arXiv1403.7834K
Strong evidence exists that coronal loops as observed in extreme
ultraviolet and soft X-rays may not be monolithic isotropic structures,
but can often be more accurately modeled as bundles of independent
strands. Modeling the observed active region transient brightenings
(ARTBs) within this framework allows for the exploration of the
energetic ramifications and characteristics of these stratified
structures. Here we present a simple method of detecting and modeling
ARTBs observed with the Hinode X-Ray Telescope (XRT) as groups of
zero-dimensional strands, which allows us to probe parameter space to
better understand the spatial and temporal dependence of strand heating
in impulsively heated loops. This partially automated method can be
used to analyze a large number of observations to gain a statistical
insight into the parameters of coronal structures, including the number
of heating events required in a given model to fit the observations. In
this article, we present the methodology and demonstrate its use in
detecting and modeling ARTBs in a sample data set from Hinode/XRT. These
initial results show that, in general, multiple heating events are
necessary to reproduce observed ARTBs, but the spatial dependence of
these heating events cannot yet be established.
---------------------------------------------------------
Title: Peristaltic Pumping near Post-coronal Mass Ejection
Supra-arcade Current Sheets
Authors: Scott, Roger B.; Longcope, Dana W.; McKenzie, David E.
2013ApJ...776...54S Altcode: 2013arXiv1308.5026S
Temperature and density measurements near supra-arcade current sheets
suggest that plasma on unreconnected field lines may experience
some degree of "pre-heating" and "pre-densification" prior to
reconnection. Models of patchy reconnection allow for heating and
acceleration of plasma along reconnected field lines but do not offer
a mechanism for transport of thermal energy across field lines. Here,
we present a model in which a reconnected flux tube retracts, deforming
the surrounding layer of unreconnected field. The deformation creates
constrictions that act as peristaltic pumps, driving plasma flow along
affected field lines. Under certain circumstances, these flows lead to
shocks that can extend far out into the unreconnected field, altering
the plasma properties in the affected region. These findings have
direct implications for observations in the solar corona, particularly
in regard to such phenomena as high temperatures near current sheets
in eruptive solar flares and wakes seen in the form of descending
regions of density depletion or supra-arcade downflows.
---------------------------------------------------------
Title: On the Chromospheric Evaporation Observed during an X1.4
Flare of 12-July, 2012
Authors: Takeda, Aki; Yoshimura, K.; McKenzie, D. E.
2013SPD....44...87T Altcode:
A GOES-class X1.4 flare from the NOAA active region 11520 was
observed with Hinode/XRT on 12-July, 2012. This region showed
sigmoidal structure, which was developed between a group of two major
positive-polarity sunspots and an area of small scattered sunspots with
negative-polarity. In the course of this flare, a long flare ribbon
(typically observed in the light of 304A or H-alpha) was formed on
the negative side of the polarity inversion line, while its positive
counter part appeared to be concentrated in a brightening around one of
the major sunspots. Two notable phenomena were observed associated with
this event: (1) Soft X-ray brightening was observed at the foot points
of the post flare loops which started to grow ~30 minutes later. (2)
Strong and narrow extension of dark lanes (or ejections of low-density
plasma) were observed from the both ends of the sigmoid loops at the
maximum phase of the flare. As neither of these phenomena are previously
reported, proper description and explanation need to be given.Abstract
(2,250 Maximum Characters): A GOES-class X1.4 flare from the NOAA active
region 11520 was observed with Hinode/XRT on 12-July, 2012. This region
showed sigmoidal structure, which was developed between a group of two
major positive-polarity sunspots and an area of small scattered sunspots
with negative-polarity. In the course of this flare, a long flare ribbon
(typically observed in the light of 304A or H-alpha) was formed on
the negative side of the polarity inversion line, while its positive
counter part appeared to be concentrated in a brightening around one of
the major sunspots. Two notable phenomena were observed associated with
this event: (1) Soft X-ray brightening was observed at the foot points
of the post flare loops which started to grow ~30 minutes later. (2)
Strong and narrow extension of dark lanes (or ejections of low-density
plasma) were observed from the both ends of the sigmoid loops at the
maximum phase of the flare. As neither of these phenomena are previously
reported, proper description and explanation need to be given.
---------------------------------------------------------
Title: Multi--Instrument Estimation Of The Non--Flaring Heating And
Reconnection Rates Of Emerging Active Region NOAA AR11112
Authors: Tarr, Lucas; Longcope, D.; McKenzie, D. E.; Yoshimura, K.
2013SPD....4430202T Altcode:
In NOAA Active Region 11112, a small bipole emerges into an area of
preexisting, unipolar flux. The bright, low lying kernel of coronal
loops above the emerging field, observed with AIA and XRT, originally
show magnetic connectivity only between regions of newly emerged flux
when overlaid on HMI magnetograms. Over the course of several days,
this bright kernel advances into the preexisting flux. The advancement
of this easily visible boundary into the old flux regions over time
provides a quantifiable rate of reconnection between old and new
magnetic domains. We compare the reconnection rate to the inferred
heating of the coronal plasma. To our knowledge, this is the first
measurement of steady, quiescent heating related to reconnection. While
AR11112 does produce an M3.0 flare on Oct 16th, 2010, the implied
reconnection we focus on here predates the flare by several days,
and does not result in any observable flaring active of its own, such
as increases in the GOES light curve, chromospheric flare ribbons, or
post--flare loops. We determine that the newly emerged flux reconnects
at a fairly steady average rate of 3.5e16 Mx/s over two days, while
the radiated power varies between 2-8e25erg/s over the same time.
---------------------------------------------------------
Title: Turbulence in the Flare Reconnection Region
Authors: Doschek, George A.; McKenzie, D. E.; Warren, H.
2013SPD....4430401D Altcode:
The physical conditions such as temperature, density, and dynamical
properties in the flare reconnection region, located above the bright
soft X-ray loops, are basically not known although there have been
measurements of non-thermal hard X-ray emission properties by RHESSI
and earlier by HXT on Yohkoh. The advent of Hinode and the Solar
Dynamics Observatory (SDO) spatially resolved observations, however,
has changed this and it is now possible to measure in more detail some
of the properties of the reconnection region. AIA imagery on SDO and
the Extreme-ultraviolet Imaging Spectrometer (EIS) and X-ray Telescope
(XRT) on Hinode allow values of non-thermal motions or turbulence in
the reconnection region to be determined. Turbulence is predicted by
theoretical models of magnetic reconnection in flares (e.g., see Liu et
al. 2008, ApJ, 676, 704) and has long been inferred spectroscopically
from non-thermal broadening of flare emission lines. Studies with
Hinode/XRT and SDO/AIA demonstrate that two-dimensional investigations
of flare velocity fields can be made, by imaging the plasma sheets
above post-CME flare arcades. These measurements are made possible
through the use of local correlation tracking (LCT), as shown by
McKenzie (2013), ApJ, 766, 39, and reveal signatures of turbulence,
including temporally and spatially varying vorticity. For some flares
the AIA and XRT results can be combined with Doppler measurements of
turbulence obtained with EIS. EIS data consist of raster scans that
include the reconnection region for flares on the limb or near the
limb. A set of spectral lines are observed that cover temperatures
from 0.25 MK up to ~20 MK. A temperature in the reconnection region
is calculated from the Fe XXIII/Fe XXIV line ratio and the thermal
Doppler and instrumental widths are subtracted from the total line
widths. The remainder is non-thermal motions or turbulence. We will
present coordinated analyses of EIS and AIA observations of plasma
sheets in post-CME flares, and demonstrate that the turbulent speeds
found by LCT are about the same magnitude as those derived from EIS
spectral line profiles obtained in the same or nearby locations.
---------------------------------------------------------
Title: Thermal Structure of Supra-arcade Downflows and Flare Plasma
Sheets
Authors: Reeves, Kathy; Hanneman, W.; McKenzie, D. E.
2013SPD....4430404R Altcode:
We use Hinode/XRT and SDO/AIA data to determine the thermal structure of
supra arcade downflows as well as the surrounding plasma sheet. Using
the multiple filters and broad temperature coverage provided by the
combination of these two telescopes, we construct DEMs in the fan plasma
and the supra-arcade downflows. Several models have indicated that
the plasma inside the supra-arcade downflows should be significantly
hotter than the surrounding plasma, but about an order of magnitude
less dense. However, we find that the temperatures of the plasma
within the downflows are either roughly the same as or lower than the
surrounding fan plasma, with only one exception. We also compare the
thermal structure of the supra-arcade plasma with calculations of the
divergence of the velocity of the plasma in the sheet in order to locate
evidence of adiabatic cooling and heating. The velocity fields are
calculated using local correlation tracking applied to high-resolution
sequences of AIA images. We find preliminary evidence that diverging
velocity fields are cooler and less dense than the surrounding plasma.
---------------------------------------------------------
Title: Calibration of Hinode/XRT for Coalignment II: Comparison of
Three Different Methods
Authors: Yoshimura, Keiji; McKenzie, D. E.
2013SPD....44...98Y Altcode:
The coalignment of solar images from various observational instruments
is an important step to study solar features/phenomena when using
data acquired from multiple telescopes or wavelengths. We have been
working on the calibration of XRT/Hinode to get coalignment parameters,
i.e., plate scale, roll angle in the plane of the sky, and pointing
information. We are developing a table of the parameters for every
single XRT image, so that all users of XRT data can easily utilize our
results for their coalignment. There are three different approaches to
get the XRT pointing information: (1) applying the cross correlation
technique to the X-ray images from XRT and the EUV images from AIA/SDO
(2) combination of solar limb fitting and cross correlation between
XRT full and partial disk images (3) using outputs from the sun sensor
(Ultra Fine Sun Sensor, UFSS) on-board Hinode We discuss the advantages
and disadvantages of each method and estimate the errors through the
cross comparison. In preparing our table of coalignment coefficients
we combine the strengths of each of these methods to provide the most
reliable resource. We also discuss the accuracy of the plate scale
of X-ray data from XRT, which can be derived from the comparison
between XRT and AIA images.Abstract (2,250 Maximum Characters): The
coalignment of solar images from various observational instruments
is an important step to study solar features/phenomena when using
data acquired from multiple telescopes or wavelengths. We have been
working on the calibration of XRT/Hinode to get coalignment parameters,
i.e., plate scale, roll angle in the plane of the sky, and pointing
information. We are developing a table of the parameters for every
single XRT image, so that all users of XRT data can easily utilize our
results for their coalignment. There are three different approaches to
get the XRT pointing information: (1) applying the cross correlation
technique to the X-ray images from XRT and the EUV images from AIA/SDO
(2) combination of solar limb fitting and cross correlation between
XRT full and partial disk images (3) using outputs from the sun sensor
(Ultra Fine Sun Sensor, UFSS) on-board Hinode We discuss the advantages
and disadvantages of each method and estimate the errors through the
cross comparison. In preparing our table of coalignment coefficients
we combine the strengths of each of these methods to provide the most
reliable resource. We also discuss the accuracy of the plate scale of
X-ray data from XRT, which can be derived from the comparison between
XRT and AIA images.
---------------------------------------------------------
Title: Peristaltic Pumping near Post-CME Supra-Arcade Current Sheets
Authors: Scott, Roger B.; Longcope, D.; McKenzie, D. E.
2013SPD....4430402S Altcode:
Measurements of temperature and density near supra-arcade current
sheets suggest that plasma on unreconnected field lines may experience
some degree of “pre-heating” and “pre-densification” prior to
their reconnection. Models of patchy reconnection allow for heating and
acceleration of plasma along reconnected field lines but do not offer a
mechanism for transport of energy and momentum across field lines. Here
we present a model in which a reconnected flux tube retracts, deforming
the surrounding layer of unreconnected field. The deformation creates
constrictions that act as peristaltic pumps, driving plasma flow along
affected field lines. Under certain circumstances these flows lead to
shocks that can extend far out into the unreconnected field, altering
the plasma properties in the affected region. These findings have
direct implications for observations in the solar corona, particularly
in regard to such phenomena as wakes seen behind supra-arcade downflows
and high temperatures near current sheets in eruptive solar flares. This
work was supported by NASA, the NSF and the DOE.
---------------------------------------------------------
Title: Survey of Coronal Null Points with SDO/AIA & WSO
Authors: Freed, Michael; McKenzie, D. E.; Longcope, D.
2013SPD....44...21F Altcode:
Magnetic fields in the corona can be approximated by using PFSS
(Potential Field Source Surface) model in conjunction with magnetogram
measurements of the photosphere. This approach is incorporated here to
find locations of magnetic null points in the solar corona. Observations
from WSO (Wilcox Solar Observatory) provide the necessary harmonic
coefficients for a PFSS model. We located all magnetic null points in
the PFSS model going back to Carrington Rotation 2098. The time and
location where they cross the West limb is compared to high resolution
observations made by SDO/AIA. Variations in predicted and observed
null point locations, and estimates of the duration of each null,
will be examined. This work will provide a catalog of coronal nulls
observed by SDO that can be examined further for interesting dynamical
behavior or variations in neighboring plasma.
---------------------------------------------------------
Title: Modeling Active Region Transient Brightenings Observed with
XRT as Multistranded Loops
Authors: Kobelski, Adam; McKenzie, D. E.
2013SPD....44...77K Altcode:
Strong evidence exists that coronal loops as observed in EUV and soft
X-rays are not monolithic isotropic structures, but are more accurately
modeled as bundles of independent strands. Modeling the observed
active region transient brightenings (ARTBs) within this framework
allows exploration of the energetic ramifications and characteristics
of these stratified structures. Here we present a simple method of
detecting and modeling ARTBs observed with the Hinode X-Ray Telescope
(XRT) as groups of simple 0-dimensional strands. We probe parameter
space to understand better the spatial and temporal dependence of
strand heating in impulsively heated loops. We present results from
using this partially automated method to analyze observations and gain
a statistical insight into the heating of these structures.
---------------------------------------------------------
Title: Turbulent Dynamics in Solar Flare Sheet Structures Measured
with Local Correlation Tracking
Authors: McKenzie, D. E.
2013ApJ...766...39M Altcode:
High-resolution observations of the Sun's corona in extreme
ultraviolet and soft X-rays have revealed a new world of complexity
in the sheet-like structures connecting coronal mass ejections (CMEs)
to the post-eruption flare arcades. This article presents initial
findings from an exploration of dynamic flows in two flares observed
with Hinode/XRT and SDO/AIA. The flows are observed in the hot (gsim
10 MK) plasma above the post-eruption arcades and measured with local
correlation tracking. The observations demonstrate significant shears
in velocity, giving the appearance of vortices and stagnations. Plasma
diagnostics indicate that the plasma β exceeds unity in at least
one of the studied events, suggesting that the coronal magnetic
fields may be significantly affected by the turbulent flows. Although
reconnection models of eruptive flares tend to predict a macroscopic
current sheet in the region between the CME and the flare arcade,
it is not yet clear whether the observed sheet-like structures are
identifiable as the current sheets or "thermal halos" surrounding the
current sheets. Regardless, the relationship between the turbulent
motions and the embedded magnetic field is likely to be complicated,
involving dynamic fluid processes that produce small length scales
in the current sheet. Such processes may be crucial for triggering,
accelerating, and/or prolonging reconnection in the corona.
---------------------------------------------------------
Title: Imaging Turbulent Dynamics in Post-CME Current Sheet Structures
Authors: McKenzie, David E.
2013enss.confE..38M Altcode:
Turbulence in current sheets is hypothesized to produce cascades from
large to small length scales, both in terms of tangled or "stochastic"
magnetic fields and in the creation of "micro-current sheets". The
resulting conditions are likely to have profound effects on the
rate of magnetic reconnection. Whereas current sheet turbulence has
historically been inferred from spectroscopic measurements of, say,
nonthermal broadening, recent developments in high-resolution EUV and
X-ray imaging have brought turbulence into a new light, revealing a
new world of complex dynamics in the sheet-like structures connecting
CMEs to post-eruption flare arcades. The image sequences demonstrate
significant shears in velocity, giving the appearance of vortices and
stagnations; and plasma diagnostics indicate that the plasma beta
can exceed unity, suggesting that the coronal magnetic fields are
significantly affected by turbulent fluid processes which produce small
length scales in the current sheet. Observational characterization
of the turbulent conditions will help to guide modeling efforts of
post-CME current sheets, particularly in regards to cascades from CME
length scales to much smaller sizes. I will present findings from an
exploration of the velocity fields in the supra-arcade sheet structures,
as imaged by SDO/AIA and measured with local correlation tracking.
---------------------------------------------------------
Title: Success of Solar Dynamics Observatory (SDO) Education &
Public Outreach (E/PO) in Montana
Authors: Freed, M. S.; Lowder, S. C.; McKenzie, D. E.
2013enss.confE..66F Altcode:
The Space Public Outreach Team (SPOT) program at Montana State
University (MSU) is the main component of SDO E/PO efforts in
Montana. SPOT brings energetic presentations of recent science &
NASA missions to students in primary & secondary schools. Presenters
are university undergraduates that visit a diverse group of K-12
students from both rural & urban areas of Montana. This program
is extremely cost effective, a valuable service-learning experience
for undergraduates at MSU and has repeatedly received praise from
both teachers and students. A complementary effort for training
schoolteachers entitled NASA Education Activity Training (NEAT) is
also employed. NEAT illustrates to teachers inexpensive and highly
effective methods for demonstrating difficult science concepts to
their students. We will highlight the successes and lessons learned
from SPOT & NEAT, so that other E/PO programs can use it as a
template to further science literacy in our nation's schools.
---------------------------------------------------------
Title: Temperature and Electron Density Diagnostics of a Candle-Flame
Shaped Flare. Asymmetric Reconnection Evidence
Authors: Guidoni, Silvina E.; McKenzie, David E.; Longcope, Dana W.;
Plowman, Joseph E.; Yoshimura, Keiji
2013enss.confE..62G Altcode:
Candle-flame shaped flares are archetypical structures that represent
indirect evidence of magnetic reconnection. For long-lived events, most
of their observed features can be explained with the classic magnetic
reconnection model of solar flares, the CSHKP model. A flare resembling
1992 Tsuneta's famous candle-flame flare occurred on January 28 2011;
we present its temperature and electron density diagnostics. This flare
was observed with Hinode/XRT, SDO/AIA, and STEREO (A)/EUVI, resulting
in high resolution, broad temperature coverage, and stereoscopic
views of this iconic structure. Our XRT filter-ratio temperature and
density maps corroborate the general reconnection scenario. The high
temperature images reveal a brightening that grows in size to form a
tower-like structure at the top of the post-flare arcade, a feature
that has been observed in other long duration events. This tower is
a localized density increase, as shown by our XRT electron density
maps. Despite the extensive work on the standard reconnection scenario,
there is no complete agreement among models regarding the nature of
this tower-like structure. The XRT maps also reveal that reconnected
loops that are successively connected at their tops to this tower
develop a density increase in one of their legs that can reach over
2 times the density value of the other leg, giving the appearance of
“half-loops”. Their density is nevertheless still lower than at
the tower. These jumps in density last longer than several acoustic
transit times along the loops. We use STEREO images to show that the
half-loop brightening is not a line-of- sight projection effect of the
type suggested by Forbes and Acton (1996). This would indicate that
asymmetric reconnection took place between loops originally belonging
to systems with different magnetic field strengths, densities, and
temperatures. We hypothesize that the heat generated by reconnection's
slow shocks is then transferred to each leg of the loop at different
rates. Therefore, the increase in electron density due to chromospheric
evaporation is different in each leg. Thermal pressure balance between
the legs is prevented by shocked plasma at the top of the loops. We also
present preliminary results comparing a new fast DEM method that uses
SDO/AIA data with the XRT filter ratio method. Both methods complement
each other, they agree at the overlap between their instruments'
temperature response functions (3-12 MK) while the SDO/AIA method
works well at lower temperatures and the XRT one at higher temperatures.
---------------------------------------------------------
Title: Shrinking Loops Observations for the 2008 April 9 Flare
Authors: Savage, S. L.; McKenzie, D. E.; Reeves, K. K.; Forbes, T. G.
2012ASPC..454..295S Altcode:
Supra-arcade downflows (SADs) have been observed with Yohkoh/SXT (soft
X-rays (SXR)), TRACE (extreme ultra-violet (EUV)), SoHO/LASCO (white
light), SoHO/SUMER (EUV spectra), and Hinode/XRT (SXR). Characteristics
such as low emissivity and trajectories which slow as they reach the
top of the arcade are consistent with post-reconnection magnetic flux
tubes. The magnetic flux within the tubes provides pressure against
filling with plasma. As with the standard model of reconnection,
the tubes retract from a reconnection site high in the corona until
they reach a more potential magnetic configuration. Viewed from a
perpendicular angle, SADs should appear as shrinking loops rather
than downflowing voids. We will present observations of supra-arcade
downflowing loops (SADLs) and show that their speeds and decelerations
are consistent with those determined for SADs.
---------------------------------------------------------
Title: Inferring Nonthermal Particle Characteristics from Thermal
Emission Signatures
Authors: Kobelski, A. R.; McKenzie, D. E.; Winter, H. D.
2012ASPC..454..333K Altcode:
Much work has been done in characterizing the nonthermal particle
beams found in flares. Most of this work has concentrated on the
interpretation of hard X-ray (HXR) emission. While HXR emission does
have a direct connection to the nonthermal particle beam, there
are other emission mechanisms that can also provide insight into
the nature of the nonthermal beam. In the impulsive phase of solar
flares the primary source of plasma heating is collisions between
the nonthermal particles and the ambient, thermal plasma in the flare
loop. The properties of the nonthermal particle beam directly affect
the heating of the thermal plasma. Thus the thermal emission (e.g.,
soft X-rays) can also yield clues to the properties of the nonthermal
beam. Recent flare modeling in the dissertation of Winter (2009)
makes specific predictions about the behavior of the soft X-ray (SXR)
emission from the flaring loop, depending on the properties of the
nonthermal particle beam. As an initial test of the applicability of
these predictions to real flares, we have undertaken a comparison to HXR
and SXR observations from the Yohkoh mission. We present preliminary
results from the analysis of Yohkoh-observed solar flares, which show
consistent temporal profiles in the apex to footpoint ratio.
---------------------------------------------------------
Title: Experimental Flat-Field for Correction of XRT Contamination
Spots
Authors: McKenzie, D. E.; Fox, J. L.; Kankelborg, C.
2012ASPC..454..453M Altcode:
Beginning in mid-2007, the XRT images are marred by dark spots due
to beads of congealed contaminant. While programs are available for
improving the cosmetic appearance of the images, no method has yet
been demonstrated for a quantitative correction. We have employed a
flatfielding method developed for MSU's MOSES sounding rocket payload,
in an attempt to restore capabilities for quantitative photometry in the
affected pixels. Initial results are encouraging; characterization of
the uncertainties in the photometric correction are ongoing. We report
on the degree to which this flatfielding attempt has been successful.
---------------------------------------------------------
Title: Low-altitude Reconnection Inflow-Outflow Observations during
a 2010 November 3 Solar Eruption
Authors: Savage, Sabrina L.; Holman, Gordon; Reeves, Katharine K.;
Seaton, Daniel B.; McKenzie, David E.; Su, Yang
2012ApJ...754...13S Altcode: 2011arXiv1111.1945S
For a solar flare occurring on 2010 November 3, we present observations
using several SDO/AIA extreme-ultraviolet (EUV) passbands of an erupting
flux rope followed by inflows sweeping into a current sheet region. The
inflows are soon followed by outflows appearing to originate from
near the termination point of the inflowing motion—an observation
in line with standard magnetic reconnection models. We measure average
inflow plane-of-sky speeds to range from ~150 to 690 km s<SUP>-1</SUP>
with the initial, high-temperature inflows being the fastest. Using the
inflow speeds and a range of Alfvén speeds, we estimate the Alfvénic
Mach number which appears to decrease with time. We also provide inflow
and outflow times with respect to RHESSI count rates and find that the
fast, high-temperature inflows occur simultaneously with a peak in the
RHESSI thermal light curve. Five candidate inflow-outflow pairs are
identified with no more than a minute delay between detections. The
inflow speeds of these pairs are measured to be ~10<SUP>2</SUP>
km s<SUP>-1</SUP> with outflow speeds ranging from ~10<SUP>2</SUP>
to 10<SUP>3</SUP> km s<SUP>-1</SUP>—indicating acceleration during
the reconnection process. The fastest of these outflows are in the
form of apparently traveling density enhancements along the legs of
the loops rather than the loop apexes themselves. These flows could
possibly either be accelerated plasma, shocks, or waves prompted
by reconnection. The measurements presented here show an order of
magnitude difference between the retraction speeds of the loops and
the speed of the density enhancements within the loops—presumably
exiting the reconnection site.
---------------------------------------------------------
Title: Dynamic Fluid Flows in Supra-Arcade Current Sheets/Thermal
Halos
Authors: McKenzie, David E.
2012shin.confE..65M Altcode:
High-resolution observations in EUV and X-rays have revealed a new
world of complexity in the sheet-like structures connecting CMEs
to the post-eruption flare arcades. The observations demonstrate
vortices, shears in velocity, and -- for perhaps the first time --
fragmentation of supra-arcade downflows. Although it is not yet clear
whether the emission is produced in the current sheet itself or in a
'thermal halo' surrounding the current sheet, the relationship between
the motions and the magnetic field associated with the current sheet
is, perforce, complicated. In particular, the vortical motions must
significantly contort the embedded magnetic field; and the fragmentation
of supra-arcade downflows suggests the presence of fluid processes
that contribute to the reduction of spatial scales in the current
sheet/thermal halo. Such processes may be crucial for triggering,
accelerating, and/or prolonging reconnection.Given that the plasma
conditions in the supra-arcade region are still imperfectly known,
such that low densities and long mean free paths complicate our
understanding of the fluidity of the flows, it is imperative that we
make the most of the opportunity provided by SDO and Hinode to chart
this dynamic regime. I will present findings from an exploration of
the velocity fields in the supra-arcade current sheet/thermal halo,
as imaged by SDO/AIA and Hinode/XRT.
---------------------------------------------------------
Title: Nozzle Driven Shocks in Post-CME Plasma
Authors: Scott, Roger B.; Longcope, D. W.; McKenzie, D. E.
2012AAS...22020407S Altcode:
Models of patchy reconnection allow for heating and acceleration of
plasma along reconnected field lines but do not offer a mechanism for
transport of energy and momentum across field lines. Here we present a
simple 2D model in which a localized region of reconnected flux creates
an apparent constriction in the surrounding layer of unreconnected
field. The moving constriction acts as a de Laval nozzle and ultimately
leads to shocks which can extend out to several times the diameter of
the flux tube, altering the density and temperature of the plasma in
that region. These findings have direct implications for observations in
the solar corona, particularly in regard to such phenomena as wakes seen
behind supra-arcade downflows and high temperatures in post-CME current
sheets. This work was supported by a joint grant from the NSF and DOE.
---------------------------------------------------------
Title: Complex Dynamic Flows in Solar Flare Sheet Structures
Authors: McKenzie, David Eugene; Reeves, K. K.; Savage, S. L.
2012AAS...22020422M Altcode:
Observations of high-energy emission from solar flares often reveal
the presence of large sheet-like structures, sometimes extending over a
space comparable to the Sun's radius. Given that these structures are
found between a departing coronal mass ejection and the post-eruption
flare arcade, it is natural to associate the structure with a
current sheet; though the relationship is unclear. Moreover, recent
high-resolution observations have begun to reveal that the motions
in this region are highly complex, including reconnection outflows,
oscillations, and apparent wakes and eddies. We present a detailed
first look at the complicated dynamics within this supra-arcade
plasma, and consider implications for the interrelationship between
the plasma and its embedded magnetic field. <P />This work is supported
by NASA under contract SP02H3901R from Lockheed-Martin to MSU (DMcK),
contract SP02H1701R from Lockheed-Martin to SAO (KKR), and contract
NNM07AB07C with the Harvard-Smithsonian Astrophysical Observatory. SLS
is supported via a NASA/GSFC NPP appointment administered by Oak Ridge
Associated Universities and under the mentorship of G. Holman.
---------------------------------------------------------
Title: Current Sheet and Reconnection Inflow-Outflow Observations
During Solar Eruptions
Authors: Savage, S. L.; Holman, G.; Reeves, K. K.; Seaton, D. B.;
McKenzie, D. E.; Su, Y.
2012ASPC..456..169S Altcode:
Magnetic reconnection is widely accepted as being associated with energy
release during solar flares; however, observations of it have been
indirect and/or incomplete. Using the suite of instruments available
spanning wavelength space, we provide observations and measurements of
both the inputs and outputs predicted from reconnection in the form of
inflows preceding outflows (i.e. supra-arcade downflows, supra-arcade
downflowing loops, upflows, and disconnection events). We also present
evidence for current sheets through which reconnection is expected to
occur and discuss current sheet motion during flare progression.
---------------------------------------------------------
Title: Elemental Abundances as a New Source of Uncertainty of the
Hinode/XRT Filter-ratio T and EM Analysis
Authors: Takeda, A.; Kobelski, A.; McKenzie, D. E.; Yoshimura, K.
2012ASPC..456..133T Altcode:
We calculated the Hinode/XRT temperature response functions with
different assumptions of elemental abundances. The enhancement of
the low FIP elements significantly affects the amplitude of the XRT
response curves. This yields a significant difference in the emission
measures calculated from the filter ratio method, while the effect on
derived temperatures is relatively small.
---------------------------------------------------------
Title: A Multi-Wavelength Statistical Study of Supra-Arcade Downflows
Authors: Savage, S. L.; McKenzie, D. E.
2012ASPC..455..305S Altcode: 2012arXiv1201.5246S
Sunward-flowing voids above post-coronal mass ejection flare
arcades, also known as supra-arcade downflows (SADs), have
characteristics consistent with post-reconnection magnetic flux tube
cross-sections. Applying semi-automatic detection and analysis software
to a large sample of flares using several instruments (e.g., Hinode/XRT,
Yohkoh/SXT, TRACE, and SOHO/LASCO), we have estimated parameters such as
speeds, sizes, heights, magnetic flux, and relaxation energy associated
with SADs, which we interpret as reconnection outflows. We also present
speed and height measurements of shrinking loops in comparison to the
SAD observations. We briefly discuss these measurements and what impact
they have on reconnection models.
---------------------------------------------------------
Title: Photometric Uncertainties within Hinode XRT
Authors: Kobelski, Adam; Saar, S. H.; Weber, M. A.; McKenzie, D. E.;
Reeves, K. K.
2012AAS...22020126K Altcode:
We have developed estimates of the systematic uncertainties for
the X-Ray Telescope (XRT) on Hinode. These estimates are included
as optional returns from the standard XRT data reduction software,
xrt_prep.pro. Included in these software estimates are uncertainties
from instrument vignetting, dark current subtraction, split bias
leveling, Fourier filtering and JPEG compression. Sources of uncertainty
that rely heavily on models of plasma radiation or assumptions of
elemental abundances, such as photon noise, are discussed, but not
included in the software. It will be shown that the photon noise
is much larger than the systematic uncertainty. <P />This work is
supported by NASA under contract NNM07AB07C with the Harvard-Smithsonian
Astrophysical Observatory
---------------------------------------------------------
Title: Calibration of Hinode/XRT for Coalignment
Authors: Yoshimura, Keiji; McKenzie, D. E.
2012AAS...22020129Y Altcode:
When someone tries to understand some phenomena on the Sun, a comparison
between the data from different types of observation for the same target
would be a good way. Fortunately various kinds of data, from satellite
and ground-based telescopes, are available for us these days. While
it is necessary to coalign the data from different instruments for the
analysis, it is often difficult to achieve sufficient accuracy with a
simple method. For the coalignment, we need to know the plate scales,
rotation angle in the plane of the sky, and pointing information
for the images, at least. To augment the information provided by the
Hinode/XRT FITS headers, we are calibrating the XRT data as accurately
as possible by means of limb fitting and cross correlation techniques,
yielding a table of coalignment parameters for every single XRT
image. The final goal of the project is to provide an easy and precise
<P />coalignment method to users of the XRT data. We also do a cross
calibration between XRT and AIA on-board SDO. Since we can find many
similar structures in some of the images from both of the instruments,
a cross correlation technique is useful for improving the accuracy of
the coalignment. Our parameter tables will include the results from
the cross calibration too.
---------------------------------------------------------
Title: Flare Half-Loops: What Are They?
Authors: McKenzie, David Eugene; Guidoni, S. E.; Longcope, D. W.;
Yoshimura, K.
2012AAS...22032201M Altcode:
The M1.4 flare of 28 January 2011 has a remarkable resemblance to
the famous "Tsuneta candle-flame" flare of 1992. It was observed
with Hinode/XRT, SDO/AIA, and STEREO (A)/EUVI, resulting in higher
resolution, greater temperature coverage, and stereoscopic views of
this iconic structure. The high temperature images reveal a brightening
that grows in size to form a tower-like structure at the top of the
arcade. They also show that loops which are successively connected to
this tower develop a density increase in one of their legs that can
exceed twice the density of the other leg, giving the appearance of
"half loops". These jumps in density last for an extended period of
time. On the other hand, XRT filter ratios suggest that temperature
is approximately uniform along the entire loop. XRT filter-ratio
density maps corroborate that the brighter legs have higher density
than the fainter halves. The tower is associated with a localized
density increase, with even higher densities than either leg of the
loop. This spatial variation of density may correspond to a shock
at the top of the loops. We use STEREO images to show that the half
loop brightening is not a line-of-sight projection effect of the type
suggested by Forbes & Acton. This work is supported under contract
SP02H3901R from Lockheed-Martin to MSU, and under contract NNM07AB07C
with the Harvard-Smithsonian Astrophysical Observatory.
---------------------------------------------------------
Title: NASA Education Activity Training (NEAT): Professional
Development for Montana K-12 Teachers
Authors: Williamson, Kathryn; McKenzie, D.; Des Jardins, A.; Key,
J.; Kanode, C.; Willoughby, S.
2012AAS...22010805W Altcode:
Piloted during the 2011-2012 academic year, the NASA Education Activity
Training (NEAT) teacher workshop program has introduced five solar
astronomy and space weather activities to over forty Montana K-12
teachers. Because many Montana schools are geographically isolated
(40% of Montana students live more than 50 miles from a city)
and/or serve traditionally underrepresented groups (primarily Native
Americans), professional development for teachers can be costly and
time consuming. However, with funding shared by the Atmospheric Imaging
Assembly EPO team and the Montana Space Grant Consortium, graduate
student specialists are able to host the two-hour NEAT workshops
on-site at the schools free of charge, and participating teachers earn
two continuing education credits. Leveraging the existing catalogue
of research-based NASA activities, the featured NEAT activities were
chosen for their ease-of-use and applicability to Montana science
standards. These include three advanced activities for older students,
such as a paper plate activity for the June 5th, 2012 Transit of Venus,
Kinesthetic Astronomy, and the Herschel Infrared experiment, along with
two simpler activities for the younger students, such as Solar Cookies
and the Electromagnetic War card game. Feedback surveys show that NEAT
workshop participants were interested and engaged in the activities
and planned on using the activities in their classrooms. With such
positive responses, the NEAT program has been a huge success and can
serve as a model for other institutions looking to increase their
space public outreach and education.
---------------------------------------------------------
Title: Multi-Stranded Coronal Loops - A Statistical Forward Model
Authors: Kobelski, Adam; McKenzie, D. E.
2012AAS...22020431K Altcode:
Strong evidence currently exists that coronal loops as observed in
EUVs and soft X-rays are not monolithic structures, but actually exist
as bundles of independent strands. It is of significant importance
to determine the size and number density of these strands in order
to better understand the spatial and temporal scales of magnetic
reconnection in the corona. In order to empirically estimate these
parameters, we have developed software to forward model the cooling
of flaring loops as bundles of strands in order to estimate their
observational signatures. By applying this forward model to a large
database of flares observed by Yohkoh/SXT, we employ a statistical
analysis to constrain the parameters in flaring coronal plasma. Results
of this analysis will be presented.
---------------------------------------------------------
Title: Thermal Structure of Supra-Arcade Plasma in Two Solar Flares
Authors: Reeves, Kathy; Savage, S. L.; McKenzie, D. E.; Weber, M. A.
2012AAS...22020405R Altcode:
In this work, we use Hinode/XRT and SDO/AIA data to determine the
thermal structure of supra-arcade plasma in two solar flares. The
first flare is a M1.2 flare that occurred on November 5, 2010 on the
east limb. This flare was one of a series of flares from AR 11121,
published in Reeves & Golub (2011). The second flare is an X1.7
flare that occurred on January 27, 2012 on the west limb. This flare
exhibits visible supra-arcade downflows (SADs), where the November
2010 flare does not. For these two flares we combine XRT and AIA
data to calculate DEMs of each pixel in the supra-arcade plasma,
giving insight into the temperature and density structures in the fan
of plasma above the post-flare arcade. We find in each case that the
supra-arcade plasma is around 10 MK, and there is a marked decrease in
the emission measure in the SADs. We also compare the DEMs calculated
with the combined AIA/XRT dataset to those calculated using AIA alone.
---------------------------------------------------------
Title: Re-interpretation Of Supra-arcade Downflows In Solar Flares
Authors: Savage, Sabrina; McKenzie, D. E.; Reeves, K. K.
2012AAS...22051602S Altcode:
Following the eruption of a filament from a flaring active region,
sunward-flowing voids are often seen above developing post-eruption
arcades. First discovered using the soft X-ray telescope aboard Yohkoh,
these supra-arcade downflows (SADs) are now an expected observation of
extreme ultra-violet and soft X-ray coronal imagers and spectrographs
(e.g, TRACE, SOHO/SUMER, Hinode/XRT, SDO/AIA). Observations made prior
to the operation of AIA suggested that these plasma voids (which
are seen in contrast to bright, high-temperature plasma associated
with current sheets) are the cross-sections of evacuated flux tubes
retracting from reconnection sites high in the corona. The high
temperature imaging afforded by AIA's 131, 94, and 193 Angstrom channels
coupled with the fast temporal cadence allows for unprecedented scrutiny
of the voids. For a flare occurring on 2011 October 22, we provide
evidence suggesting that SADs, instead of being the cross-sections
of relatively large, evacuated flux tubes, are actually wakes (i.e.,
trailing regions of low density) created by the retraction of much
thinner tubes. This re-interpretation is a significant shift in the
fundamental understanding of SADs, as the features once thought to
be identifiable as the shrinking loops themselves now appear to be
"side effects" of the passage of the loops through the supra-arcade
plasma. In light of the fact that previous measurements have attributed
to the shrinking loops characteristics that may instead belong to
their wakes, we discuss the implications of this new interpretation
on previous parameter estimations and on reconnection theory.
---------------------------------------------------------
Title: Measuring Uncertainties in the Hinode X-Ray Telescope
Authors: Kobelski, A.; Saar, S.; McKenzie, D. E.; Weber, M.; Reeves,
K.; DeLuca, E.
2012ASPC..456..241K Altcode:
We have developed estimates of the systematic photometric uncertainties
the X-Ray Telescope (Kano et al. (2008)) on Hinode (Kosugi et
al.(2007)). These estimates are included as optional returns from the
standard XRT data reduction software, xrt_prep.pro. Included in the
software estimates are uncertainties from instrument vignetting, dark
current subtraction, split bias leveling, fourier filtering and JPEG
compression. We show that these uncertainties are generally smaller
than the photon counting uncertainty. However, due to the reliance
on assumptions of plasma radiation models and elemental abundances,
photon counting is not included in the software.
---------------------------------------------------------
Title: Post-Flare Half-Loops: What are They?
Authors: Guidoni, Silvina E.; McKenzie, David E.; Longcope, Dana W.
2012decs.confE..12G Altcode:
The M1.4 flare of Jan 28, 2011 has a remarkable resemblance to the
famous Tsuneta flare of 1992. It was observed with Hinode/XRT, SDO/AIA,
and STEREO (A)/EUVI, giving us higher resolution, greater temperature
coverage, and stereoscopic views of this iconic structure. The high
temperature images reveal a brightening that grows in size to form
a tower-like structure at the top of the post-flare arcade. They
also show that loops that are successively connected to this tower
develop a density increase in one of their legs that can reach 4
times the density value of the other leg, giving the appearance of
"half loops". These jumps in density last for an extended period of
time. On the other hand, XRT filter ratios suggest that temperature
is approximately uniform along the entire loop. XRT filter-ratio
density maps corroborate that the brighter legs have higher density
than the rest of the loop. The tower is a localized density increase
at even higher densities than the brighter side of the loop. This may
correspond to a shock at the top of the loops. We use STEREO images to
show that the half loop brightening is not a line-of-sight projection
effect of the type suggested by Forbes & Acton.
---------------------------------------------------------
Title: Re-interpretation of Supra-arcade Downflows in Solar Flares
Authors: Savage, Sabrina L.; McKenzie, David E.; Reeves, Katharine K.
2012ApJ...747L..40S Altcode: 2011arXiv1112.3088S
Following the eruption of a filament from a flaring active region,
sunward-flowing voids are often seen above developing post-eruption
arcades. First discovered using the soft X-ray telescope aboard Yohkoh,
these supra-arcade downflows (SADs) are now an expected observation of
extreme ultra-violet and soft X-ray coronal imagers and spectrographs
(e.g, TRACE, SOHO/SUMER, Hinode/XRT, SDO/AIA). Observations made
prior to the operation of AIA suggested that these plasma voids
(which are seen in contrast to bright, high-temperature plasma
associated with current sheets) are the cross-sections of evacuated
flux tubes retracting from reconnection sites high in the corona. The
high temperature imaging afforded by AIA's 131, 94, and 193 Å channels
coupled with the fast temporal cadence allows for unprecedented scrutiny
of the voids. For a flare occurring on 2011 October 22, we provide
evidence suggesting that SADs, instead of being the cross-sections
of relatively large, evacuated flux tubes, are actually wakes (i.e.,
trailing regions of low density) created by the retraction of much
thinner tubes. This re-interpretation is a significant shift in the
fundamental understanding of SADs, as the features once thought to
be identifiable as the shrinking loops themselves now appear to be
"side effects" of the passage of the loops through the supra-arcade
plasma. In light of the fact that previous measurements have attributed
to the shrinking loops characteristics that may instead belong to
their wakes, we discuss the implications of this new interpretation
on previous parameter estimations and on reconnection theory.
---------------------------------------------------------
Title: SDO Education and Public Outreach
Authors: Wawro, M.; Scherrer, D.; McKenzie, D.; Kellagher, E.; Van
Norden, W.; Durscher, R.; Winter, H.; Myers, D.
2012decs.confE..70W Altcode:
With the huge inflow of SDO data, the SDO E/PO team has focused its
efforts on finding solutions that put SDO data into the hands of the
public including classrooms and informal education programs. After
summarizing the highlights of our post-launch activities, we will
reintroduce the SDO E/PO team, describe current efforts aimed at
increasing the number of people exposed to SDO data, and and the
quality of programs using data, as well as start a dialog around how
we as a community would like to move forward.
---------------------------------------------------------
Title: EUV Analysis of a Quasi-static Coronal Loop Structure
Authors: Scott, J. T.; Martens, P. C. H.; McKenzie, D. E.
2012SoPh..276..113S Altcode: 2011arXiv1110.5560S
Decaying active region 10942 is investigated from 4:00 - 16:00 UT on
24 February 2007 using a suite of EUV observing instruments. Results
from Hinode/EIS, STEREO and TRACE show that, although the active region
has decayed and no sunspot is present, the physical mechanisms that
produce distinguishable loop structures, spectral line broadening,
and plasma flows still occur. A coronal loop that appears as a
blue-shifted structure in Doppler maps is apparent in intensity
images of log(T)=6.0 - 6.3 ions. The loop structure is found to be
anti-correlated with spectral line broadening generally attributed to
non-thermal velocities. This coronal loop structure is investigated
physically (temperature, density, geometry) and temporally. Light
curves created from imaging instruments show brightening and dimming
of the loop structure on two different time scales; short pulses of
10 - 20 min and long duration dimming of two - four hours until its
disappearance. The coronal loop structure, formed from relatively
blue-shifted material that is anti-correlated with spectral line
broadening, shows a density of 10<SUP>10</SUP> to 10<SUP>9.3</SUP>
cm<SUP>−3</SUP> and is visible for longer than characteristic cooling
times. The maximum non-thermal spectral line broadenings are found to
be adjacent to the footpoint of the coronal loop structure.
---------------------------------------------------------
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
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: The Solar Dynamics Observatory (SDO) Education and Outreach
(E/PO) Program: Changing Perceptions One Program at a Time
Authors: Drobnes, E.; Littleton, A.; Pesnell, W. D.; Beck, K.; Buhr,
S.; Durscher, R.; Hill, S.; McCaffrey, M.; McKenzie, D. E.; Myers,
D.; Scherrer, D.; Wawro, M.; Wolt, A.
2012SoPh..275..391D Altcode: 2011SoPh..tmp..420D; 2011SoPh..tmp..424D; 2011SoPh..tmp..367P
We outline the context and overall philosophy for the combined Solar
Dynamics Observatory (SDO) Education and Public Outreach (E/PO)
program, present a brief overview of all SDO E/PO programs along with
more detailed highlights of a few key programs, followed by a review
of our results to date, conclude a summary of the successes, failures,
and lessons learned, which future missions can use as a guide, while
incorporating their own content to enhance the public's knowledge
and appreciation of science and technology as well as its benefit
to society.
---------------------------------------------------------
Title: Observational studies of reconnection in the solar corona
Authors: McKenzie, David E.
2011PhPl...18k1205M Altcode:
In recent years, observational studies of the corona have shifted
focus. Where they were once purely qualitative morphological
explorations seeking to support the presence of reconnection, more
investigations are providing empirical estimates of the physical
conditions in the reconnecting corona. These studies are enabled
and enhanced by orbiting telescopes with high angular and temporal
resolution. In this article, some recent findings about the empirical
quantities are reviewed, including recent estimates of the flux
transferred in individual patchy reconnection episodes, the size
distribution of post-reconnection flux tubes, and the energy released
by the flux tubes as they shrink.
---------------------------------------------------------
Title: Distribution Functions of Sizes and Fluxes Determined from
Supra-arcade Downflows
Authors: McKenzie, D. E.; Savage, S. L.
2011ApJ...735L...6M Altcode: 2011arXiv1106.4567M
The frequency distributions of sizes and fluxes of supra-arcade
downflows (SADs) provide information about the process of their
creation. For example, a fractal creation process may be expected
to yield a power-law distribution of sizes and/or fluxes. We examine
120 cross-sectional areas and magnetic flux estimates found by Savage
& McKenzie for SADs, and find that (1) the areas are consistent
with a log-normal distribution and (2) the fluxes are consistent with
both a log-normal and an exponential distribution. Neither set of
measurements is compatible with a power-law distribution nor a normal
distribution. As a demonstration of the applicability of these findings
to improved understanding of reconnection, we consider a simple SAD
growth scenario with minimal assumptions, capable of producing a
log-normal distribution.
---------------------------------------------------------
Title: Forward Modeling for Unresolved Flaring Loops
Authors: Kobelski, Adam; McKenzie, D. E.
2011SPD....42.1824K Altcode: 2011BAAS..43S.1824K
The apparent width of observed coronal loops can have
significant effects on the perceived evolution of flaring active
regions. Frequently, comparing a model flare to observation requires an
estimate of the filling factor of loops contributing to the signal. If
the analysis assumes the loops are resolved, the cooling times
derived from the observations are often much longer than predicted
by models. We have developed software to forward model the cooling
of flaring loops, and estimate their observational signatures. This
allows exploration of the physical parameters necessary within a given
model to reproduce the observations. We can then estimate the number of
unresolved strands contained within the observed flare loop. We will
present early results from this study using data from Yohkoh/SXT. The
implementation of Hinode/XRT observations to improve our spatial
resolution and thermal range will also discussed. <P />This work is
supported by NASA under contract NNM07AB07C with the Harvard-Smithsonian
Astrophysical Observatory. Yohkoh data are provided courtesy of the
NASA-supported Yohkoh Legacy Archive at Montana State University.
---------------------------------------------------------
Title: The Distributions of Post-Reconnection Flux Tube Sizes and
Fluxes Determined from Supra-Arcade Downflows
Authors: McKenzie, David Eugene; Savage, S. L.
2011SPD....42.2210M Altcode: 2011BAAS..43S.2210M
Supra-arcade downflows (SADs) are downward-moving features observed
in the hot, low-density region above posteruption flare arcades. They
are believed to be created by patchy reconnection in the post-CME
current sheet. The sizes and fluxes of SADs provide information about
the process of their creation. For example, the "fractal current sheet"
scenario proposed in the literature may be expected to yield a power-law
distribution of sizes and/or fluxes. We examine 120 cross-sectional
areas and magnetic flux estimates from observations of SADs, and find
that (1) the areas are consistent with a log-normal distribution,
and (2) the fluxes are consistent with both a log-normal and an
exponential distribution. Neither set of measurements is compatible
with a power-law distribution, and so the data do not appear to support
a fractal process for SAD creation. As an alternative, we consider
a simple SAD growth scenario with minimal assumptions, capable of
producing a log-normal distribution.
---------------------------------------------------------
Title: Quantitative Examination of a Large Sample of Supra-arcade
Downflows in Eruptive Solar Flares
Authors: Savage, Sabrina L.; McKenzie, David E.
2011ApJ...730...98S Altcode: 2011arXiv1101.1540S
Sunward-flowing voids above post-coronal mass ejection flare arcades
were first discovered using the soft X-ray telescope aboard Yohkoh
and have since been observed with TRACE (extreme ultraviolet (EUV)),
SOHO/LASCO (white light), SOHO/SUMER (EUV spectra), and Hinode/XRT
(soft X-rays). Supra-arcade downflow (SAD) observations suggest that
they are the cross-sections of thin flux tubes retracting from a
reconnection site high in the corona. Supra-arcade downflowing loops
(SADLs) have also been observed under similar circumstances and
are theorized to be SADs viewed from a perpendicular angle. Although
previous studies have focused on dark flows because they are easier to
detect and complementary spectral data analysis reveals their magnetic
nature, the signal intensity of the flows actually ranges from dark to
bright. This implies that newly reconnected coronal loops can contain a
range of hot plasma density. Previous studies have presented detailed
SAD observations for a small number of flares. In this paper, we
present a substantial SADs and SADLs flare catalog. We have applied
semi-automatic detection software to several of these events to
detect and track individual downflows thereby providing statistically
significant samples of parameters such as velocity, acceleration, area,
magnetic flux, shrinkage energy, and reconnection rate. We discuss
these measurements (particularly the unexpected result of the speeds
being an order of magnitude slower than the assumed Alfvén speed),
how they were obtained, and potential impact on reconnection models.
---------------------------------------------------------
Title: Earthquake distribution patterns in Africa: their relationship
to variations in lithospheric and geological structure, and their
rheological implications
Authors: Craig, T. J.; Jackson, J. A.; Priestley, K.; McKenzie, D.
2011GeoJI.185..403C Altcode: 2011GeoJI.tmp...74C
We use teleseismic waveform inversion, along with depth phase analysis,
to constrain the centroid depths and source parameters of large African
earthquakes. The majority of seismic activity is concentrated along
the East African Rift System, with additional active regions along
stretches of the continental margins in north and east Africa, and in
the Congo Basin. We examine variations in the seismogenic thickness
across Africa, based on a total of 227 well-determined earthquake
depths, 112 of which are new to this study. Seismogenic thickness
varies in correspondence with lithospheric thickness, as determined
from surface wave tomography, with regions of thick lithosphere being
associated with seismogenic thicknesses of up to 40 km. In regions of
thin lithosphere, the seismogenic thickness is typically limited to
≤20 km. Larger seismogenic thicknesses also correlate with regions
that have dominant tectonothermal ages of ≥1500 Ma, where the East
African Rift passes around the Archean cratons of Africa, through the
older Proterozoic mobile belts. These correlations are likely to be
related to the production, affected by method and age of basement
formation, and preservation, affected by lithospheric thickness,
of a strong, anhydrous lower crust. The Congo Basin contains the only
compressional earthquakes in the continental interior. Simple modelling
of the forces induced by convective support of the African plate,
based on long-wavelength free-air gravity anomalies, indicates that
epeirogenic effects are sufficient to account for the localization
and occurrence of both extensional and compressional deformation in
Africa. Seismicity along the margins of Africa reflects a mixture
between oceanic and continental seismogenic characteristics, with
earthquakes in places extending to 40 km depth.
---------------------------------------------------------
Title: Earthquake depth distributions in central Asia, and their
relations with lithosphere thickness, shortening and extension
Authors: Sloan, R. A.; Jackson, J. A.; McKenzie, D.; Priestley, K.
2011GeoJI.185....1S Altcode: 2011GeoJI.tmp...44S
This paper examines the relationship between seismogenic thickness,
lithosphere structure and rheology in central and northeastern
Asia. We accurately determine earthquake depth distributions which
reveal important rheological variations in the lower crust. These
variations exert a fundamental control on the active tectonics and the
morphological evolution of the continents. We consider 323 earthquakes
across the Tibetan Plateau, the Tien Shan and their forelands as well as
the Baikal Rift, NE Siberia and the Laptev Sea and present the source
parameters of 94 of these here for the first time. These parameters
have been determined through body wave inversion, the identification
of depth phases or the modelling of regional waveforms. Lower crustal
earthquakes are found to be restricted to the forelands in areas
undergoing shortening, and to locations where rifting coincides with
abrupt changes in lithosphere thickness, such as the NE Baikal Rift
and W Laptev Sea. The lower crust in these areas is seismogenic at
temperatures that may be as high as 600°C, suggesting that it is
anhydrous, and is likely to have great long-term strength. Lower
crustal earthquakes are therefore a useful proxy indicating strong
lithosphere in places that are too small in areal extent for this to
be confirmed independently by estimating effective elastic thickness
from gravity-topography relations. The variation in crustal rheology
indicated by the distribution of lower-crustal earthquakes has
many implications ranging from the support of mountain belts and the
formation of steep mountain fronts, to the localization and orientation
of rifting. In combination, these processes can also be responsible
for the separation of the front of the thin-skinned mountain belts
from their hinterlands when continents separate.
---------------------------------------------------------
Title: An Invitation to the Improved Yohkoh Legacy data Archive
Authors: Takeda, A.; Acton, L. W.; McKenzie, D.; Yoshimura, K.;
Freeland, S. L.
2010AGUFMSH11B1645T Altcode:
The Yohkoh Legacy data Archive (YLA) is a unique source of solar X-ray
images and spectra obtained with the Yohkoh satellite(1991-2001). The
archive consists of four levels of data products from raw to highly
value added, with ample amount of documentation and user-friendly web
interface (http://solar.physics.montana.edu/ylegacy). The YLA is also
unique in that quality and variety of the products and services have
been constantly improved through these nine years after the completion
of the satellite mission. Our recent improvements are: (1) Completion of
the stray light correction, applied to the data after the SXT entrance
filter failure in 1992. (2) Completion of the satellite attitude data
correction. (3) E-mail based individual user support (E-consultant
service). (4) New FITS header definition with World Coordinate System
compliance. (5) Update of SXT response function based on the latest
atomic data and models (Chianti 6.0.1). (6) Introduction of a new
data category, Level 3, for co-aligned composite images suitable for
browsing in movie mode. The main body of our archive (data from the
Soft X-ray Telescope) are provided in both Yohkoh-specific (XDA) and
FITS formats. The XDA format is convenient for analysis with existing
SSW/Yohkoh software that runs under IDL. The more general FITS format
enables use of advanced SSW applications developed in the various
missions after Yohkoh. FITS products do not specifically require IDL
to read and view images, which allows our products to be accessed from
a wide range of communities. Our products can be accessed through our
quick-look and data-search web services, and also through the Virtual
Solar Observatory data search. Since 2009, YLA is funded as one of
NASA's Resident Archives in Virtual Observatories for Heliophysics Data
program. Through the funds, we take responsibility for maintaining
the best corrected data sets, and providing the easy access and user
support. The top page of the YLA web interface
---------------------------------------------------------
Title: Science Objectives for an X-Ray Microcalorimeter Observing
the Sun
Authors: Laming, J. Martin; Adams, J.; Alexander, D.; Aschwanden, M;
Bailey, C.; Bandler, S.; Bookbinder, J.; Bradshaw, S.; Brickhouse,
N.; Chervenak, J.; Christe, S.; Cirtain, J.; Cranmer, S.; Deiker, S.;
DeLuca, E.; Del Zanna, G.; Dennis, B.; Doschek, G.; Eckart, M.; Fludra,
A.; Finkbeiner, F.; Grigis, P.; Harrison, R.; Ji, L.; Kankelborg,
C.; Kashyap, V.; Kelly, D.; Kelley, R.; Kilbourne, C.; Klimchuk, J.;
Ko, Y. -K.; Landi, E.; Linton, M.; Longcope, D.; Lukin, V.; Mariska,
J.; Martinez-Galarce, D.; Mason, H.; McKenzie, D.; Osten, R.; Peres,
G.; Pevtsov, A.; Porter, K. Phillips F. S.; Rabin, D.; Rakowski, C.;
Raymond, J.; Reale, F.; Reeves, K.; Sadleir, J.; Savin, D.; Schmelz,
J.; Smith, R. K.; Smith, S.; Stern, R.; Sylwester, J.; Tripathi, D.;
Ugarte-Urra, I.; Young, P.; Warren, H.; Wood, B.
2010arXiv1011.4052L Altcode:
We present the science case for a broadband X-ray imager with
high-resolution spectroscopy, including simulations of X-ray spectral
diagnostics of both active regions and solar flares. This is part of
a trilogy of white papers discussing science, instrument (Bandler et
al. 2010), and missions (Bookbinder et al. 2010) to exploit major
advances recently made in transition-edge sensor (TES) detector
technology that enable resolution better than 2 eV in an array that
can handle high count rates. Combined with a modest X-ray mirror, this
instrument would combine arcsecondscale imaging with high-resolution
spectra over a field of view sufficiently large for the study of
active regions and flares, enabling a wide range of studies such as
the detection of microheating in active regions, ion-resolved velocity
flows, and the presence of non-thermal electrons in hot plasmas. It
would also enable more direct comparisons between solar and stellar
soft X-ray spectra, a waveband in which (unusually) we currently have
much better stellar data than we do of the Sun.
---------------------------------------------------------
Title: Reconnection Outflows and Current Sheet Observed with
Hinode/XRT in the 2008 April 9 "Cartwheel CME" Flare
Authors: Savage, Sabrina L.; McKenzie, David E.; Reeves, Katharine K.;
Forbes, Terry G.; Longcope, Dana W.
2010ApJ...722..329S Altcode: 2010arXiv1003.4758S
Supra-arcade downflows (SADs) have been observed with Yohkoh/SXT (soft
X-rays (SXR)), TRACE (extreme ultraviolet (EUV)), SOHO/LASCO (white
light), SOHO/SUMER (EUV spectra), and Hinode/XRT (SXR). Characteristics
such as low emissivity and trajectories, which slow as they reach the
top of the arcade, are consistent with post-reconnection magnetic flux
tubes retracting from a reconnection site high in the corona until they
reach a lower-energy magnetic configuration. Viewed from a perpendicular
angle, SADs should appear as shrinking loops rather than downflowing
voids. We present X-ray Telescope (XRT) observations of supra-arcade
downflowing loops (SADLs) following a coronal mass ejection (CME) on
2008 April 9 and show that their speeds and decelerations are consistent
with those determined for SADs. We also present evidence for a possible
current sheet observed during this flare that extends between the
flare arcade and the CME. Additionally, we show a correlation between
reconnection outflows observed with XRT and outgoing flows observed
with LASCO.
---------------------------------------------------------
Title: Inferring Nonthermal Particle Characteristics from Thermal
Emission Signatures: Temperature Evolution
Authors: Kobelski, Adam; Winter, H.; McKenzie, D. E.
2010AAS...21640422K Altcode: 2010BAAS...41..903K
In the impulsive phase of solar flares the primary source of plasma
heating is collisions between the nonthermal particles and the ambient,
thermal plasma in the flare loop. Thus the thermal emission (e.g.,
soft X-rays) can yield clues to the properties of the nonthermal
beam. We have undertaken a study of the nonthermal particle signatures
contained within the thermal emission of a flaring coronal loop to
test predictions modeled in the dissertation of Winter (2009). Here we
study loops as observed in thermal soft X-ray (SXR) emission by the
Yohkoh satellite. We present the temperature evolution as viewed in
SXR to that predicted by the model, and continue an analysis of the
temporal profile of the SXR emission.
---------------------------------------------------------
Title: Reconnection Outflows and Current Sheet Observed with
Hinode/XRT in the April 9 2008 "Cartwheel CME" Flare
Authors: Savage, Sabrina; McKenzie, D. E.; Reeves, K. K.; Forbes,
T. G.; Longcope, D. W.
2010AAS...21640423S Altcode: 2010BAAS...41R.903S
Supra-arcade downflows (SADs) have been observed with Yohkoh/SXT (soft
X-rays (SXR)), TRACE (extreme ultra-violet (EUV)), SoHO/LASCO (white
light), SoHO/SUMER (EUV spectra), and Hinode/XRT (SXR). Characteristics
such as low emissivity and trajectories which slow as they reach the
top of the arcade are consistent with post-reconnection magnetic flux
tubes. The magnetic flux within the tubes provides pressure against
filling with plasma. As with the standard model of reconnection,
the tubes then retract from a reconnection site high in the corona
until they reach a more potential magnetic configuration. Viewed from
a perpendicular angle, SADs should appear as shrinking loops rather
than downflowing voids. We will present observations of supra-arcade
downflowing loops (SADLs) following a CME on April 9, 2008 with XRT
and show that their speeds and decelerations are consistent with those
determined for SADs. We will also present evidence for a possible
current sheet observed during this flare that extends between the CME
and the flare arcade. Additionally, we will show a correlation between
reconnection outflows observed with XRT and outgoing flows observed
with LASCO.
---------------------------------------------------------
Title: Quantifying Separator Reconnection Between Emerging and
Existing Active Regions
Authors: Malanushenko, Anna; Longcope, D. W.; McKenzie, D. E.; Yusuf,
M. H.
2010AAS...21640507M Altcode: 2010BAAS...41..890M
When one active region emerges close to an older active region,
coronal loops connecting the two regions are often observed in
extreme ultraviolet (EUV). This signifies the occurrence of magnetic
reconnection, an important mechanism in other contexts, such as solar
flares and coronal mass ejections. We measure the rate of the magnetic
reconnection by identifying each coronal loop observed in EUV that
connects the existing and the emerging active regions. For each loop we
estimate amount of magnetic flux it carries by measuring its apparent
width in EUV and the magnetic field strength in the same location using
(non)-linear force-free field reconstruction (Malanushenko et. al.,
2009). We find that the amount of reconnected flux apparent on EUV
is smaller than the flux through the separator surface in the point
charge magnetic model (Longcope, 2005). This discrepancy provides a
means to estimate the fraction of reconnecting loops that would appear
in the EUV bandpass. We measure the delay time between the noticeable
beginning of the emergence and the reconnection apparent in EUV. We
apply this analysis to five emergence events. This work expands and
improves the method described by Longcope et. al. (2005).
---------------------------------------------------------
Title: Reconnection outflows and current sheet observed with
Hinode/XRT in the April 9 2008 "Cartwheel CME" flare
Authors: McKenzie, David; Savage, Sabrina; Reeves, Kathy; Forbes,
Terry; Longcope, Dana
2010cosp...38.1952M Altcode: 2010cosp.meet.1952M
The "Cartwheel CME" event of April 9, 2008, presents an exemplary
view of motions and structures consistent with the commonly held view
of magnetic reconnection. Following the eruption of the coronal mass
ejection from the southwest limb of the Sun, an X-ray-bright arcade
was observed to form. Hinode/XRT observed coronal loops shrinking into
the top of the arcade, consistent with the reconnection picture. We
present measurements of the speeds and decelerations of these
shrinking loops, and demonstrate that the measurements are consistent
with those determined for supra-arcade downflows in other eruptive
flares. Moreover, we present evidence for a possible current sheet
observed during this flare, extending between the CME and the flare
arcade. The shrinking loops, and also outflows moving radially away
from the Sun, were observed to move along this current sheet. Finally,
we show a correlation between the anti-Sunward reconnection outflows
observed with XRT and identifiable features in the CME observed
with LASCO. This work is supported by NASA contracts NNM07AB07C and
NNX08AG44G, and NSF con-tract ATM-0837841.
---------------------------------------------------------
Title: Flare Physics in the Hinode Era (Keynote)
Authors: McKenzie, D. E.
2009ASPC..415..427M Altcode:
Hinode's manifest of instrumentation was conceived to investigate
the magnetic connections through the photosphere, lower atmosphere,
and corona. The complementarity of the instruments is indeed useful,
as demonstrated in numerous flares and eruptions in just the first two
years of operation. I will review some of the findings from Hinode's
observations of flares to date. <P />It is true, of course, that
Hinode's capabilities have evolved since launch. These changes cause
the planning of observations to be more complex, and the analysis to
be less straightforward; but they do not diminish Hinode's ability
to produce important observations of solar flares. On the contrary,
Hinode is poised to make truly surprising discoveries. I will explain
why this is so, and why we should look forward to the challenge of
the coming activity cycle.
---------------------------------------------------------
Title: Reconstructing the Local Twist of Coronal Magnetic Fields and
the Three-Dimensional Shape of the Field Lines from Coronal Loops
in Extreme-Ultraviolet and X-Ray Images
Authors: Malanushenko, A.; Longcope, D. W.; McKenzie, D. E.
2009ApJ...707.1044M Altcode: 2009arXiv0909.5141M
Nonlinear force-free fields are the most general case of force-free
fields, but the hardest to model as well. There are numerous methods
of computing such fields by extrapolating vector magnetograms from the
photosphere, but very few attempts have so far made quantitative use of
coronal morphology. We present a method to make such quantitative use
of X-ray and EUV images of coronal loops. Each individual loop is fit
to a field line of a linear force-free field, allowing the estimation
of the field line's twist, three-dimensional geometry, and the field
strength along it. We assess the validity of such a reconstruction
since the actual corona is probably not a linear force-free field,
and that the superposition of linear force-free fields is generally
not itself a force-free field. To do so, we perform a series of tests
on nonlinear force-free fields, described in Low & Lou. For model
loops we project field lines onto the photosphere. We compare several
results of the method with the original field, in particular the
three-dimensional loop shapes, local twist (coronal α), distribution
of twist in the model photosphere, and strength of the magnetic
field. We find that (1) for these trial fields, the method reconstructs
twist with a mean absolute deviation of at most 15% of the range of
photospheric twist, (2) heights of the loops are reconstructed with a
mean absolute deviation of at most 5% of the range of trial heights,
and (3) the magnitude of non-potential contribution to a photospheric
field is reconstructed with a mean absolute deviation of at most 10%
of the maximal value.
---------------------------------------------------------
Title: Detecting and Measuring Reconnection Outflows in the Hinode Era
Authors: Savage, S. L.; McKenzie, D. E.
2009ASPC..415..455S Altcode:
Our aim has been to provide direct quantitative measurements of
reconnection signatures during solar flaring events in order to
constrain the properties of flare energetics. Reconnection outflows
are observed as sunward-flowing voids during long-duration flares,
consistent with 3D reconnection models. Through the use of our automatic
detection software, we have obtained trajectories, velocities, sizes,
and magnetic flux information for outflows in several flares from
various instruments. Several limitations have been encountered with
instruments prior to the availability of Hinode, and it is the purpose
of this work to show the progress we have made in detecting reconnection
signatures in the form of supra-arcade downflows (SADs) and to emphasize
the potential of making better detections and measurements with Hinode's
X-ray Telescope (XRT).
---------------------------------------------------------
Title: Inferring Nonthermal Particle Characteristics from Thermal
Emission Signatures
Authors: Kobelski, A.; Winter, H. D.; McKenzie, D. E.
2009AGUFMSH23A1528K Altcode:
Much work has been done in characterizing the nonthermal particle
beams found in flares. Most of this work has concentrated on the
interpretation of hard X-ray (HXR) emission. While HXR emission does
have a direct connection to the nonthermal particle beam, there
are other emission mechanisms that can also provide insight into
the nature of the nonthermal beam. In the impulsive phase of solar
flares the primary source of plasma heating is collisions between
the nonthermal particles and the ambient, thermal plasma in the flare
loop. The properties of the nonthermal particle beam directly affect
the heating of the thermal plasma. Thus the thermal emission (e.g.,
soft X-rays) can also yield clues to the properties of the nonthermal
beam. Recent flare modeling in the dissertation of Winter (2009)
makes specific predictions about the behavior of the soft X-ray (SXR)
emission from the flaring loop, depending on the properties of the
nonthermal particle beam. As an initial test of the applicability of
these predictions to real flares, we have undertaken a comparison to HXR
and SXR observations from the Yohkoh mission. We present preliminary
results from the analysis of Yohkoh-observed solar flares, pursuant
to the predictions of the model.
---------------------------------------------------------
Title: An analysis of young ocean depth, gravity and global residual
topography
Authors: Crosby, A. G.; McKenzie, D.
2009GeoJI.178.1198C Altcode:
The variation of ocean depth with age in the absence of crustal
thickening and dynamic support places valuable constraints on
the thermal and rheological properties of the lithosphere and
asthenosphere. We have attempted to estimate this variation using
a global data set of shiptracks, with particular emphasis on young
ocean floor. In this respect, this paper extends a previous study
published in this journal by the same authors, which concentrated on
the older parts of the ocean basins. We find that, prior to 80 Ma,
subsidence patterns are reasonably consistent, with gradients of
325 +/- 20 m Ma <SUP>-1/2</SUP> and zero-age depths of 2600 +/- 200
m. There is a strong inverse correlation between zero-age depth and
the gradient of depth with the square root of age which is unrelated
to local variations in dynamic support. Global depth-age trends to 160
Ma are not significantly different to those for the individual ocean
basins. Within corridors of similar basement age, gravity-topography
correlations are consistently 30 +/- 5 mGal km<SUP>-1</SUP>. Simple
isostatic theory and numerical modelling of mantle plumes suggests
that, if the minimum depth of convection is defined by the base of
the mechanical boundary layer, the admittance should be a function
of plate age. The observation that it is not implies that the active
convective upwelling beneath young lithosphere ceases at the same depth
as it does beneath old oceanic plates. This result is consistent with
geochemical modelling of melts near mid-ocean ridges. We have examined
the relationship between residual topography and gravity worldwide,
and have found that good spatial correlations are restricted to the
Atlantic, North Pacific and youngest Indian ocean basins. By contrast,
residual topography and gravity are poorly or negatively correlated
in the South and young North Pacific Ocean and in the older Indian
Ocean. Away from regions of thick crust and flexure, histograms of
residual topography and gravity have symmetric distributions about
zero. We then use this residual topography to estimate the volume
and buoyancy flux of seven major plume swells. In Hawaii, the clear
correlation between melt and swell volumes in discrete age corridors
is evidence that the horizontal velocity of the hot plume material far
downstream from the plume is similar to the plate spreading velocity
and that the plume pulses over time. Finally, comparison with seismic
tomographic models suggests that the long-wavelength (>2000 km)
residual topographic and gravity anomalies have an origin deeper than
250 km. This result is consistent with observations that the admittance
is approximately constant at wavelengths longer than 800 km.
---------------------------------------------------------
Title: Detecting and Measuring Reconnection Outflows in the Hinode Era
Authors: Savage, Sabrina Leah; McKenzie, David E.
2009shin.confE.192S Altcode:
Our aim has been to provide direct quantitative measurements of
reconnection signatures during solar flaring events in order to
constrain the properties of flare energetics. Reconnection outflows are
observed as voids flowing towards the sun during long-duration flares
which is consistent with 3D reconnection models. Through the use of
our semi-automatic detection software, we have obtained trajectories,
velocities, sizes, magnetic fluxes, and loop shrinkage energies for
outflows in several flares from various instruments including SXT,
TRACE, and LASCO. Several limitations, such as poor spatial resolution
for high energy wavelengths and slow cadence compared to the flow speed,
have been encountered with instruments prior to the availability of
Hinode, and it is the purpose of this work to show the progress we have
made in detecting reconnection signatures in the form of supra-arcade
downflows (SADs) and to emphasize the potential of making better
detections and measurements with Hinode's X-ray telescope (XRT).
---------------------------------------------------------
Title: Quantitative Examination of Supra-arcade Downflows in Eruptive
Solar Flares
Authors: McKenzie, D. E.; Savage, Sabrina L.
2009ApJ...697.1569M Altcode:
Downward motions above post-coronal mass ejection flare arcades are an
unanticipated discovery of the Yohkoh mission, and have subsequently
been detected with TRACE, SOHO/LASCO, SOHO/SUMER, and Hinode/XRT. These
supra-arcade downflows are interpreted as outflows from magnetic
reconnection, consistent with a three-dimensional generalization
of the standard reconnection model of solar flares. We present
results from our observational analyses of downflows, which include a
semiautomated scheme for detection and measurement of speeds, sizes,
and—for the first time—estimates of the magnetic flux associated
with each shrinking flux tube. Though model dependent, these findings
provide an empirical estimate of the magnetic flux participating in
individual episodes of patchy magnetic reconnection, and the energy
associated with the shrinkage of magnetic flux tubes.
---------------------------------------------------------
Title: Inferring Local Twist of the Coronal Magnetic Field from
Coronal Loops in EUV and X-ray Images
Authors: Malanushenko, Anna; Longcope, D. W.; McKenzie, D. E.
2009SPD....40.2902M Altcode:
Non-linear force-free fields are the most general case of force-free
fields, but the hardest to model as well. There are numerous methods
of computing such fields by extrapolating vector magnetograms from
the photosphere, but very few attempts have so far made quantitative
use of coronal morphology. We present an improved method which infers
properties of the force-free field from X-Ray and EUV images of active
region coronal loops. Each loop evident in an image is fit to field
lines from constant-alpha fields. Our algorithm thereby estimates
the three-dimensional geometry of each loop as well its local twist
(alpha) and the magnetic field strength over its length. We assess
the performance of this method by applying it to known examples of
3D non-linear force free fields. We demonstrate that at least some
features of the local twist distribution could be reconstructed using
this method.
---------------------------------------------------------
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.
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: Properties of a Coronal Loop Structure with EIS, TRACE,
and STEREO
Authors: Scott, Jason; Martens, P. C. H.; McKenzie, D.
2009SPD....40.1217S Altcode:
The physical properties of a coronal loop structure are investigated
using three EUV observing instruments. The density, thermal width,
and lifetime of a loop structure are found. Spectral coverage from
EIS provides density and thermal information. Observations from TRACE
and STEREO show the structure's geometry and intensity as a function
of time in multiple wavebands. The isolated loop is straightened
and characterized by a Gaussian fit to perpendicular cross-cuts of
the observed structure. This allows for the extraction of background
subtracted intensities which is important when isolating the coronal
structure for analysis. These background subtracted intensities are
then used to determine the thermal characteristics (temperature,
emission measure ), density, structure width, and lifetime. These
results provide much needed measurements of coronal loop structure.
---------------------------------------------------------
Title: Modeling the Evolving Magnetic Field in a Coronal Sigmoid
Authors: McKenzie, David Eugene; Malanushenko, A.; Longcope, D.
2009SPD....40.1203M Altcode:
The importance of coronal sigmoids as progenitors of eruptions and
mass ejections is well established. However, the storage of magnetic
energy prior to a sigmoid's eruption is difficult to quantify. While
the non-potentiality of the coronal force-free fields is clearly
responsible for the free energy, models of the field are difficult to
verify. We utilize a method, developed at Montana State University and
described at this meeting by A. Malanushenko, to model the force-free
field within a coronal sigmoid observed by TRACE and Hinode/XRT. By
modeling the twist in the sigmoid's field over the span of a few days
leading up to its eruption, it is hoped that such a model can yield
insight to the buildup of energy. This work is supported by NASA
contract NNX07AI01G, and by SAO contract SV7-77003.
---------------------------------------------------------
Title: Observations and analysis of the April 9, 2008 CME using
STEREO, Hinode TRACE and SoHO data
Authors: Reeves, K. K.; Patsourakos, S.; Stenborg, G.; Miralles, M.;
Deluca, E.; Forbes, T.; Golub, L.; Kasper, J.; Landi, E.; McKenzie,
D.; Narukage, N.; Raymond, J.; Savage, S.; Su, Y.; van Ballegooijen,
A.; Vourlidas, A.; Webb, D.
2008AGUFMSH12A..04R Altcode:
On April 9, 2008 a CME originating from an active region behind the limb
was well-observed by STEREO, Hinode, TRACE and SoHO. Several interesting
features connected to this eruption were observed. (1) The interaction
of the CME with open field lines from a nearby coronal hole appeared
to cause an abrupt change in the direction of the CME ejecta. (2) The
prominence material was heated, as evidenced by a change from absorption
to emission in the EUV wavelengths. (3) Because the active region was
behind the limb, the X-Ray Telescope on Hinode was able to take long
enough exposure times to observe a faint current- sheet like structure,
and it was able to monitor the dynamics of the plasma surrounding this
structure. This event is also being studied in the context of activity
that occurred during the Whole Heliosphere Interval (WHI).
---------------------------------------------------------
Title: The Yohkoh Legacy Archive
Authors: Acton, L. W.; Takeda, A.; McKenzie, D. E.
2008AGUFMSA53A1563A Altcode:
Yohkoh was a Japan/US/UK mission for the study of high energy
processes on the sun. Scientific operation extended from September
1991 until 14 December 2001, nearly an entire solar activity
cycle. Observations included full-disk soft and hard x-ray imaging,
hard x-ray spectroscopy, and high resolution flare spectroscopy in
S XV, Ca XIX, Fe XXV and Fe XXVI from the Bent Crystal Spectrometer
(BCS). The Yohkoh Legacy Archive (YLA) brings together all Yohkoh
observational data along with extensive documentation required for
a full understanding of instrumentation, mission operations, and
data reduction and correction. Extensive meta-data aid the user in
efficiently accessing the data base. Creation of the YLA has been the
work of 8 years; the top objective has been to present the extensive
Yohkoh database in a form fully usable for scientists or students who
are unfamiliar with Yohkoh instrumentation. The YLA may be accessed
at http://solar.physics.montana.edu/ylegacy or through the Virtual
Solar Observatory (VSO), although the VSO capability is still under
development. Data from the Yohkoh hard x-ray instruments and BCS are
presented in flare list formats. The Soft X-ray Telescope (SXT) images
are available in quantitative and movie formats. This long, uniform,
archive of SXT images is especially useful for solar cycle studies as
well as high resolution soft x-ray flare studies. Examples of YLA data
products and research enabled by the archive will be presented.
---------------------------------------------------------
Title: Topography associated with crustal flow in continental
collisions, with application to Tibet
Authors: Bendick, R.; McKenzie, D.; Etienne, J.
2008GeoJI.175..375B Altcode: 2008GeoJI.tmp..185B
Collision between an undeformable indenter and a viscous region
generates isostatically compensated topography by solid-state
flow. We model this process numerically, using a finite element
scheme. The slope, amplitude and symmetry of the topographic signal
depend on the indenter size and the Argand number of the viscous
region, a dimensionless ratio of gravitational body forces to viscous
forces. When applied to convergent continental settings, these scaling
rules provide estimates of the position of an indenter at depth and
the mechanical properties of the viscous region, especially effective
viscosity. In Tibet, forward modelling suggests that some elevated,
low relief topography within the northern plateau may be attributed
to lower crustal flow, stimulated by a crustal indenter, possibly
Indian lithosphere. The best-fit model constrains the northernmost
limit of this indenter to 33.7°N and the maximum effective viscosity
of Eurasian middle and lower crust to 1 × 10<SUP>20</SUP> +/- 0.3 ×
10<SUP>20</SUP> Pa s.
---------------------------------------------------------
Title: Hinode XRT observations of a long-lasting coronal sigmoid
Authors: McKenzie, D. E.; Canfield, R. C.
2008A&A...481L..65M Altcode:
Aims:Coronal sigmoids are important sources of eruptions into
interplanetary space, and a handful of models have been proposed
to explain their characteristic S shape. However, the coronal X-ray
images available to date have generally not had sufficient resolution to
distinguish between these models. The goal of the present investigation
is to determine whether the new observations from Hinode can help
us to make such a distinction. <BR />Methods: We present the first
observations of a persistent coronal sigmoid obtained with the Hinode
X-Ray Telescope (XRT). The excellent angular resolution of XRT (1 arcsec
per pixel) and the sigmoid's location near disk center combined to
provide an unprecedented view of the formation and eruption of this
phenomenon. We compared the observed morphology with expectations
inferred from two popular models of sigmoid formation, the bald-patch
separatrix surface model and the kinking flux rope model. <BR />Results:
The images during the pre-eruptive phase show that the overall S
shape of the sigmoid comprises two separate J-shaped bundles of many
loops. The straight sections of the two J patterns lie anti-parallel to
one another in the middle of the S, on opposite sides of the magnetic
polarity inversion line. The images during the eruptive phase reveal
that, before any soft X-ray flaring begins, a diffuse linear structure
almost as long as the sigmoid lifts off from the middle of the S. It
shows slight clockwise rotation. The X-ray flare begins with the
appearance of a sheared arcade of short loops, in the area centered
between the two J-shaped patterns of the sigmoid. <BR />Conclusions:
Taken together, the observational findings provide strong support for
the bald-patch separatrix surface model for this sigmoid.
---------------------------------------------------------
Title: Semi-Automatic Detection Software for Supra-Arcade Downflows
Authors: Savage, S. L.; McKenzie, D. E.; McLaughlin, L.
2007AGUFMSH44A1730S Altcode:
Detectable signatures of magnetic reconnection, a possible
source of solar coronal heating, aid in constraining flare
energetics. Supra-arcade downflows (SADs), first detected during the
Yohkoh mission, are an example of an observable consequence of magnetic
flux tube reconnection. These sunward-traveling voids above arcade loops
are consistent with outflows resulting in standard 3D reconnection
models of solar flares. We have developed semi-automated detection
software to detect downflows and analyze their trajectories, speeds,
sizes, and magnetic flux in order to constrain parameters for flare
modeling. We will present these measurements as observed primarily
by SXT and TRACE supplemented with new XRT observations and discuss
their implications.
---------------------------------------------------------
Title: Supra-Arcade Downflows: Results from Observational Analysis
Authors: McKenzie, D. E.; Savage, S.; Tolan, J. E.
2007ASPC..369..489M Altcode:
Downward motions above post-CME flare arcades are an exciting discovery
of the Yohkoh mission, and have subsequently been detected with TRACE,
SOHO/LASCO, SOHO/SUMER, and GOES/SXI. These “supra-arcade downflows"
have been interpreted as outflows from flux tube reconnection,
consistent with a 3D generalization of the standard reconnection model
of solar flares. We will present results from our observational analyses
of downflows, including measured speeds and other aspects related to 3D
patchy reconnection. We will also indicate the limitations of present
observations, and motivations for utilizing the Solar-B instruments
for measurements of these reconnection signatures.
---------------------------------------------------------
Title: Temperature Structure of Active Region Coronal Loops as seen
by Hinode
Authors: Scott, Jason; Winter, H.; Cirtain, J.; Martens, P. C.;
McKenzie, D.
2007AAS...210.9437S Altcode: 2007BAAS...39..327S
We present preliminary results from Hinode of coronal loops. MSU's
SEMAST code is used to perform differential emission measure analysis
along active region coronal loops. The differential emission measures
are then used to investigate the temperature and density structure
of the loops. The results are then entered into the coronal loop
database and compared to theoretical models for scaling laws and
heating mechanisms. <P />This work is supported by NASA GSRP fellowship
NNG05GK64H
---------------------------------------------------------
Title: Erratum
Authors: Emmerson, B.; Jackson, J.; McKenzie, D.; Priestley, K.
2007GeoJI.169.1300. Altcode:
No abstract at ADS
---------------------------------------------------------
Title: EIS/Hinode Look At Active Region Dynamics
Authors: Ugarte-Urra, Ignacio; Warren, H. P.; Brooks, D. H.; Williams,
D. R.; Cirtain, J. W.; McKenzie, D. E.; Weber, M.; Hara, H.; Harra,
L. K.
2007AAS...210.9429U Altcode: 2007BAAS...39..222U
We present some initial results from the Hinode EUV Imaging Spectrometer
(EIS) on the heating and cooling of active region loops. The events
we observe are part of the short term active region evolution within
the span of 50 hours of sit-and-stare observations. We investigate
the temporal evolution of the intensity and Doppler shift of spectral
lines formed at different temperatures. We then determine time lags
and cooling times at various temperature regimes and discuss the
results in the context of previous results provided by earlier space
missions. This effort is considered a first step into the hydrodynamic
modeling of the loop structures. The morphology of the structures is
obtained from X-Ray Telescope (XRT) and TRACE images.
---------------------------------------------------------
Title: Semi-Automatic Detection Software For Supra-Arcade Downflows
Authors: Savage, Sabrina; McKenzie, D. E.; McLaughlin, L.
2007AAS...210.2518S Altcode: 2007BAAS...39..134S
It is widely believed that magnetic reconnection is a key mechanism
in coronal activity and flare energy release. Due to the spatial and
temporal scales involved with observing structures in this extremely
faint and dynamic regime, determining the physical characteristics of
reconnection using appropriate observable signatures has proven to be
challenging. Supra-arcade downflows (SADs), first detected during the
Yohkoh mission, are just such an example of an observable consequence
of magnetic flux tube reconnection. These sunward-traveling voids above
post-eruption coronal arcades are consistent with outflows predicted by
3D reconnection models of solar flares. We have developed semi-automated
software to detect downflows and analyze their trajectories, speeds,
sizes, and magnetic flux in order to constrain parameters for flare
modeling. We will present these measurements as observed primarily by
SXT and TRACE and discuss their implications.
---------------------------------------------------------
Title: Hinode/XRT Observations of a Coronal Sigmoid
Authors: McKenzie, David E.; Canfield, R. C.
2007AAS...210.7208M Altcode: 2007BAAS...39Q.180M
We present the first observations of an X-ray sigmoid made with
the Hinode X-Ray Telescope, co-aligned with those of TRACE and
SoHO/MDI. XRT's extraordinary angular resolution (1 arcsec/pixel)
and the sigmoid's location near disk center combined to provide an
unprecedented view of the formation and eruption of this phenomenon. XRT
observed the sigmoid over several days, with cadences as high as 1 image
per 10--30 seconds. The first motions associated with eruption of the
sigmoid started at 0600UT on 12-Feb-2007; the first brightening of the
ensuing X-ray arcade was seen at 0740UT. <P />The images during the
pre-eruptive phase, which ends with the onset of large-scale motions,
show:<ul><li>The overall S shape of the sigmoid is not
defined by any single X-ray loop. Rather, many individual loops
collectively comprise an S-shaped pattern.<li>The S shape is
comprised of two separate J shapes, whose straight sections lie
anti-parallel to one another in the middle of the S, on opposite
sides of the magnetic polarity inversion line. <li>During
the several-day span of the XRT observation, the S shape gradually
becomes better defined.</ul>The images during the eruptive
phase show:<ul><li>Approximately 100 minutes before any
soft X-ray flaring begins, a diffuse linear structure, almost as long
as the sigmoid, lifts off from the middle of the S. It shows slight
clockwise rotation.<li>The X-ray flare begins with the appearance
of a sheared arcade of short loops, in the area centered between the
two J-shaped patterns of the sigmoid. <li>Within 16 hours of
the start of the flare, no S shape remains.</ul>Taken together,
these features provide strong support for the Bald-Patch Separatrix
Surface model of sigmoids put forth by Titov & Demoulin (1999).
---------------------------------------------------------
Title: A Model for E/PO Success: The Space Public Outreach Team
Authors: Littenberg, Tyson; Shapiro Key, J.; McKenzie, D. E.
2007AAS...21011601L Altcode: 2007BAAS...39..241L
The Space Public Outreach Team (SPOT) program at Montana State
University brings presentations about current and future NASA missions
to Montana K-12 students at no cost to the schools. Formerly the Mars
Public Outreach Program (MPOP), this Education and Public Outreach model
of undergraduate presenters, graduate student managers, and faculty
advisers has been field tested in Montana for over ten years and is
now exportable to other institutions. The SPOT program is a proven
success, garnering rave reviews from students and teachers alike,
while reaching geographically isolated and underserved populations
for the low institutional cost of approximately four dollars per
participant. We will outline the SPOT model and highlight some of the
program's successes.
---------------------------------------------------------
Title: The relationship between depth, age and gravity in the oceans
Authors: Crosby, A. G.; McKenzie, D.; Sclater, J. G.
2006GeoJI.166..553C Altcode: 2006GeoJI.tmp..146C
We reassess the applicability of the thermal plate cooling model
to the subsidence of the North Pacific, Atlantic and North Indian
Ocean Basins. We use a new numerical plate model in which the
thermophysical parameters of the lithosphere vary with temperature
according to the results of laboratory experiments, and the ridge
temperature structure is consistent with the thickness of the oceanic
crust. We first attempt to exclude thickened crust from our data set,
and then to exclude swells and downwellings by masking regions of the
data that remains that have significant gravity anomalies when there
exists a clear regional correlation between intermediate-wavelength
gravity and topography. We find that the average variation of depth
with age is consistent with conventional half-space models until
about 90 Myr. Thereafter, the departure from the half-space cooling
curve is more rapid than predicted using simple conductive plate
cooling models. The depth-age curves in the Pacific and Atlantic
show ~250 m of temporary shallowing between the ages of 90-130 Myr,
a result consistent with the outcome of experiments on the initiation
of small-scale boundary layer convection. The results do not change
significantly if the estimated component of the gravity arising from
plate cooling is subtracted prior to calculation of the correlation
between gravity and topography. A 90-km-thick conductive plate is
nevertheless a reasonable model for the average temperature structure
of the oldest part of the Pacific ocean lithosphere. In the Pacific, the
broad topographic undulations associated with the Line Island Swell, the
Hawaiian Swell and surrounding basins have correlated gravity anomalies
and an admittance of approximately 30 mGal km<SUP>-1</SUP> and are
likely to result from convective circulation in the upper mantle. In
the Northeast Atlantic, the intermediate-wavelength admittance over
the Cape Verde swell is similar; in the Northwest Atlantic over the
Bermuda Swell it is slightly larger but not as well constrained.
---------------------------------------------------------
Title: 3D Reconnection Simulations of Descending Coronal Voids
Authors: Linton, Mark; Longcope, D.; Warren, H.; McKenzie, D.
2006SPD....37.0123L Altcode: 2006BAAS...38R.219L
We will present simulations of a highly localized, finite durationburst
of 3D reconnection in a post-CME current sheet. Suchreconnection forms
a pair of 3D reconnected flux tubes piercing thecurrent sheet. These
tubes retract from the reconnection region,pushing their way through
the surrounding magnetic field to form apost-reconnection arcade below
the reconnection region. We willdiscuss how the evolution of these
reconnected flux tubes can formthe descending, post-eruption voids
which have been seen in thehigh corona by the Yohkoh, TRACE and LASCO
instruments. Wewill compare the velocities and deceleration profiles of
theobserved voids with those of the simulated reconnected flux tubes.We
will also show how the presence of multiple reconnectionregions in a
single current sheet affects the dynamics of thereconnected tubes.
---------------------------------------------------------
Title: Quantitative Examination of Observed Reconnection Outflows
Authors: McKenzie, David E.; Savage, S.
2006SPD....37.2403M Altcode: 2006BAAS...38..251M
Downward motions above post-CME flare arcades--the supra-arcade
downflows--are important signatures of magnetic reconnection in
flares. As tracers of reconnection outflow, their characteristics are
indicative of the parameters of 3D patchy reconnection, including the
size of participating flux tubes, and, by extension, the characteristic
size of the localized diffusion region. As we will show, application of
automated feature-tracking programs to flare images from SXT and TRACE
yields empirical estimates of important quantities for understanding
patchy reconnection, including speeds, locations, size distributions,
and even the amount of flux participating in a typical reconnection.This
work is supported by NASA Grant NNG04GB74G.
---------------------------------------------------------
Title: Observations of Separator Reconnection to an Emerging Active
Region
Authors: Longcope, D. W.; McKenzie, D. E.; Cirtain, J.; Scott, J.
2005ApJ...630..596L Altcode:
Extreme-ultraviolet (EUV) observations of an emerging active region are
used to study separator reconnection in the corona. We identify each EUV
loop connecting the emerging polarity to a nearby existing active region
over the 41 hr period beginning at emergence onset. Their geometrical
resemblance to post-reconnection field lines from a magnetic model
of the active region pair implicates separator reconnection in their
production. While some reconnection is evident within 7 hr of emergence
onset, the most intense period occurs after a 1 day delay. The sum of
cross sections of all observed loops accounts for only one-fifth of the
transferred magnetic flux predicted by the model. We suggest that the
remaining loops remain at temperatures too high, or at densities too
low, to be detected in our EUV data. The most intense reconnection
requires as much as 10<SUP>9</SUP> V along the coronal separator;
however, the observed loops suggests that the flux is transferred as
discrete bundles of ~4×10<SUP>18</SUP> Mx each. The reconnection
appears to directly dissipate only a small fraction of the energy
released, while the rest is dissipated within the post-reconnection
flux over the ensuing 6 or more hours the loops remain visible. The
net energy released, and ultimately dissipated, is consistent with
the amount that could be stored magnetically during the 24 hr delay
between emergence and reconnection.
---------------------------------------------------------
Title: Education & Public Outreach in Montana, Supporting the
Solar Dynamics Observatory
Authors: Winter, H. D.; McKenzie, D. E.
2005AGUSMSH13D..03W Altcode:
In the Space Public Outreach Team (SPOT) program at Montana State
University (MSU), currently a major component of SDO Education and
Public Outreach at MSU, the hallmark of the program has been the
presentation of cutting-edge science regarding topics of current
interest. The program, under the management of Montana Space Grant
Consortium since 1996, is a proven way to bring the excitement of NASA
space science investigations to primary and secondary schools, while
simultaneously involving university students in E/PO. The program is
remarkably cost-effective, useful as a service-learning device, and
extremely popular. We will outline the mechanisms of the SPOT program,
including the involvement of a diverse group of undergraduates, and
its recent expansion to reach more of Montana's students.
---------------------------------------------------------
Title: Statistical Relationships in Characteristics of a Sample of
Interplanetary Coronal Mass Ejections Detected Near Earth
Authors: McKenzie, D. E.; Wilson, K. G.; Leamon, R. J.
2005AGUSMSH32A..02M Altcode:
Using in situ measurements of solar wind conditions near Earth, we
compared the signatures of a sample of transients, which we tentatively
identify as magnetic clouds. Images from several solar observatories
were utilized to identify the source eruptions which launched each
ICME from the Sun. The plasma conditions within these structures were
compared, and trends were sought that would correlate with the type of
solar progenitor structure that spawned the eruptions. Additionally,
a magnetic model was fitted to the measurements of each ICME detected
near Earth. We present findings that suggest a systematic difference
in cloud structure, depending on progenitor type; also, we present
results indicating a relationship between the speed of transit from
Sun to Earth and the magnetic field strength in the ICME.
---------------------------------------------------------
Title: Observations of Separator Reconnection to an Emerging Active
Region
Authors: Longcope, D. W.; Cirtain, J.; McKenzie, D.; Scott, J.
2004AGUFMSH13A1140L Altcode:
Extreme ultraviolet (EUV) observations of an emerging active region
are used to study separator reconnection in the corona. We follow each
EUV loop connecting the emerging polarity to a nearby existing active
region. Their geometrical resemblance to post-reconnection field lines
from a magnetic model of the active region pair implicates separator
reconnection in their production. While some reconnection is evident
within 7 hours of emergence onset, the most intense period occurs
after a one-day delay. The sum of cross sections of all observed
loops accounts for only one-fifth of the magnetic flux whose transfer
the model predicts. We suggest that the remaining loops remain at
temperatures too high, or at densities too low, to be detected in
our EUV data. The most intense reconnection requires as much as
260 MV along the coronal separator, however, the observed loops
suggests that the flux is transfered as discrete bundles of 1.0e18
Mx each. The reconnection appears to directly dissipate only a small
fraction of the energy released, while the rest is dissipated within
the post-reconnection flux over the ensuing 6 or more hours, during
which the flux remains visible. The net energy released, and ultimately
disiipated, is consistent with the amount which could be stored during
the 24-hour delay between emergence and reconnection. This work was
supported by NASA grant NAG5-10489
---------------------------------------------------------
Title: Periodic Variations in X-Ray Emission Intensity of Coronal
Loops
Authors: McKenzie, D. E.; Pollock, E.; Lane, C.
2004ESASP.575..422M Altcode: 2004soho...15..422M
No abstract at ADS
---------------------------------------------------------
Title: Geoeffective CMEs, Filaments, and Sigmoids
Authors: McKenzie, D. E.; Leamon, R. J.
2004AAS...204.3801M Altcode: 2004BAAS...36..712M
Coronal mass ejections--particularly those with flux rope
structures--have the potential to trigger geomagnetic storms, depending
on the properties of the flux ropes. Eruptions of both filaments and
coronal sigmoids have been indicated as important drivers of space
weather, and both filaments and sigmoids have been modeled with flux
rope structure. However, the analysis reported by Leamon et al. (2002)
suggested that magnetic clouds associated with filament eruptions are
different from magnetic clouds associated with erupting sigmoids. In
this investigation, we are exploring the possibility of predicting
the geoeffectiveness of CMEs through analysis of the pre-eruption
magnetic structures.
---------------------------------------------------------
Title: SUMER spectral observations of post-flare supra-arcade inflows
Authors: Innes, D. E.; McKenzie, D. E.; Wang, Tongjiang
2003SoPh..217..247I Altcode:
On 21 April 2002 a large eruptive flare on the west limb of the Sun
developed a bright, very dynamic, post-flare arcade. In TRACE 195
Å images, a series of dark, sunward moving flows were seen against
the bright extreme ultraviolet (EUV) arcade. SUMER obtained a series
of spectra of the dark EUV flows in the lines C ii, Fe xii, and Fe
xxi at a fixed position above the limb. These spectra give spatially
resolved line-of-sight velocities and emission measures for the arcade
plasma over a temperature range 2×10<SUP>4</SUP> to 10<SUP>7</SUP>
K. The flows are dark in all SUMER lines. The UV continuum longward
(∼ 1350 Å) and shortward (∼ 675 Å) of the hydrogen Lyman limit
is used to determine whether the dark 195 Å inflows are due to regions
of low plasma density (plasma voids) or cold absorbing material. There
is some evidence of absorption near the front of one of the inflows;
however, along most of the dark channels there is no change in continuum
ratio and we therefore conclude, as originally suggested by McKenzie
and Hudson (1999), that they are plasma voids.
---------------------------------------------------------
Title: Observations of 1000 km s<SUP>−1</SUP> Doppler shifts in
10<SUP>7</SUP> K solar flare supra-arcade
Authors: Innes, D. E.; McKenzie, D. E.; Wang, Tongjiang
2003SoPh..217..267I Altcode:
An X1.5 flare on the west limb of the Sun on 21 April 2002 developed
a large supra-arcade about 30 min after flare onset. The growth of
the supra-arcade can be followed in both TRACE 195 Å images and SUMER
spectra. Its growth seems to be associated with dark (in TRACE images),
sunward moving channels that descend onto the arcade from above. SUMER
recorded Doppler shifts of 800-1000 km s<SUP>−1</SUP> in Fe xxi 1354
Å from positions where this sunward flow interacts with the arcade
tops. We describe the observations, focusing on the relationship of
the high Fe xxi line shifts to the sunward moving dark flows.
---------------------------------------------------------
Title: Simultaneous SUMER and TRACE Observations of Supra-arcade
Downflows and Oscillations
Authors: McKenzie, D. E.; Innes, D. E.; Wang, T.
2003SPD....34.1510M Altcode: 2003BAAS...35..832M
The 21 April 2002 X-class solar flare exhibited supra-arcade downflows
of the type described by McKenzie and Hudson (1999). The flare was
observed simultaneously by several observatories, and the downflows
were clearly imaged by TRACE and SOHO/SUMER. We present a comparison
of the TRACE and SUMER data concerning the supra-arcade downflows, and
demonstrate that the dark downflow features are consistent with regions
of locally depressed plasma density. Furthermore, the implications
of the oscillatory behavior of the supra-arcade spikes for coronal
seismology will be considered. <P />We gratefully acknowledge support
from NASA, DARA, CNES, and ESA.
---------------------------------------------------------
Title: Five years of Yohkoh science nuggets
Authors: Hudson, H. S.; McKenzie, D. E.; Nitta, N. V.
2002AGUFMSH52A0453H Altcode:
The Yohkoh "science nuggets", weekly Web-based reports emphasizing
current Yohkoh observations, began October 24, 1997. Many writers
(the SXT "chief observers" in particular) contributed, and over the
years a characteristic style developed: these were educational pieces
rather than public-relations puffs, and they each attempted to describe
a particular item for a technically savvy non-specialist. In this poster
we summarize the nugget philosophy and point out some of our favorites,
such as the remarkable "triple jet." This and many other interesting
observations have not yet otherwise been published. Since December 2001
we have gradually broadened our science basis to include SOHO, TRACE,
and now RHESSI input. The topic index lists more than 60 categories,
and there is a general search facility. We present this poster partly
to encourage discussion of the future development of the series.
---------------------------------------------------------
Title: The Point Spread Function of the Yohkoh Soft X-ray Telescope
Authors: McKenzie, D. E.; Gburek, S.; Acton, L. W.; Martens, P. C.
2002AAS...200.5502M Altcode: 2002BAAS...34Q.732M
The point spread function (PSF) of the Yohkoh solar observatory's Soft
X-ray Telescope has two primary components, a sharply defined core
and a diffuse wing due to photon scattering. Because the extent of the
PSF is significantly wider than a single pixel, its characterization is
useful for improvement of the quality of the SXT images. We will present
results from analyses of the two PSF components, and demonstrate our
best model of the core and scattering wing of the SXT point spread
function. An example of PSF deconvolution to remove the effects of
photon scattering will be given.
---------------------------------------------------------
Title: Signatures of Reconnection in Eruptive Flares [Invited]
Authors: McKenzie, D. E.
2002mwoc.conf..155M Altcode:
Solar flares are defined by magnetism. The energy that is stored up,
transferred, and released is done so in and by the magnetic fields
of the Sun; the structures in which the flares occur are wholly
dependent on the configuration of magnetic connections; and it is the
rearrangement of these connections that we believe plays such a large
and important role in many of the processes observed in flares. Many
of our theoretical pictures of flare mechanisms rely in some part on
magnetic reconnection, and one by one the observable signatures of these
models are being uncovered in chromospheric and coronal data. These
data, in turn, introduce observational constraints that help to drive
the models. I will summarize some key observations that have helped
to support the case for reconnection, and that have helped us to peer
more deeply into the behavior of coronal plasmas and magnetic fields.
---------------------------------------------------------
Title: Reconnection observed: 2d and 3d elements
Authors: McKenzie, David
2002ocnd.confE..20M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Modeling the coronal loop of an X-ray bright point
Authors: McMullen, R.; Longcope, D.; McKenzie, D.; Kankelborg, C.;
Klimchuk, J.
2002ocnd.confE..28M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Yohkoh Public Outreach Project
Authors: Larson, M. B.; Slater, T.; McKenzie, D.; Acton, L.; Alexander,
D.; Lemen, J.; Freeland, S.; Metcalf, T.
2002mwoc.conf..117L Altcode:
The NASA funded Yohkoh Public Outreach Project (YPOP) began in 1995
with the goal of providing public access to high quality Yohkoh
SXT data via the World Wide Web. The project utilizes the intrinsic
excitement of the SXT data, and in particular the SXT movies, to develop
science learning tools and classroom activities. The WWW site at URL:
http://www.lmsal.com/YPOP/ uses a movie theater theme to highlight
available Yohkoh movies in a format that is entertaining and inviting
to non-scientists and well received by scientists. We will discuss
the wide range of people YPOP has reached over the past six years,
as well as lessons learned during the development of the project.
---------------------------------------------------------
Title: The Yohkoh Public Outreach Project: A Space Science Resource
for Formal and Informal Education
Authors: Lemen, J. R.; Alexander, D.; Metcalf, T. R.; Freeland, S. L.;
Acton, L. W.; Larson, M.; McKenzie, D.; Slater, T.
2001AGUFMED12A0160L Altcode:
The Yohkoh Public Outreach Project (YPOP) is a NASA-funded web site
maintained by scientists and educators at Lockheed Martin Solar and
Astrophysics Lab. and Montana State University. YPOP includes a range
of activities for youngsters, parents, teachers and anyone interested
in learning more about the Sun. YPOP utilizes a number of approaches
to the dissemination of solar data which incorporates elements of both
formaleducation, via a number of lesson plans and classroom activities,
and informal education, via access to the latest solar images, a
solar tour, and updated movies. This combination has proved extremely
effective in providing quality access to scientific data for a broad
audience with a wide range of interests. The Yohkoh Public Outreach
Project can be found at http://www.LMSAL.com/YPOP.
---------------------------------------------------------
Title: Simulations of an X-Ray Bright Point's Evolution
Authors: McMullen, R. A.; Longcope, D. W.; McKenzie, D. E.; Kankelborg,
C. K.
2001AGUFMSH11C0726M Altcode:
We study the spatial structure and temporal evolution of an X-ray
bright point loop in order to understand the role of magnetic energy
dissipation. We use a time-dependent gasdynamic model to simulate
the corona and transition region in the x-ray bright point's coronal
loop. For this work we model a bright point observed by TRACE, Yohkoh
and SOHO on June 17, 1998, where the magnetic field geometry is derived
from an extrapolation of magnetograms. We study the effects of various
spatial and temporal distributions of heat deposition within the
loop. The quantity of energy deposited and the location of the energy
release is constrained by a model equilibrium magnetic field. We model
the observed transient brightening of the bright point as a series of
nanoflare events.
---------------------------------------------------------
Title: Hard X-rays from Slow Flares
Authors: Hudson, H. S.; McKenzie, D. E.
2001EP&S...53..581H Altcode:
"Slow LDEs" are those for which the rise phase is slow, as well as
the decay phase. Such flares follow the Neupert effect, which implies
that the non-thermal energy release has a similar relationship to
heating as in a normal impulsive flare. Based on a sample of 53
slow LDEs during the first nine years of Yohkoh observations, we
find 19 for which substantial overlap occurs with BATSE hard X-ray
observations. These events tend strongly to have extended hard X-ray
emission even though their hard X-ray emission does not tend to be
"impulsive" in the sense of rapid variation. The hard X-ray fluences
for these 19 events correlate with the soft X-ray peak fluxes, implying
strong non-thermal particle acceleration even for these relatively slow
energy-release rates. These events often correspond to the occurrence of
"supra-arcade downflows," a phenomenon consistent with the classical
reconnection model for gradual-phase flare energy release. This
correspondence suggests a close relationship, not depending strongly
upon time scale, between large-scale reconnection and the acceleration
of non-thermal electrons.
---------------------------------------------------------
Title: Downflows and structure above LDE arcades: Possible signatures
of reconnection?
Authors: McKenzie, D. E.; Hudson, H. S.
2001EP&S...53..577M Altcode:
We will introduce a set of observations made during the decay phase of
long duration event (LDE) flares on the Sun. In a number of events,
the soft X-ray images from Yohkoh SXT indicate a downward directed
flow field in the region immediately above the flare arcade. These
are tentatively identified as evidence of reconnection outflows. The
prototypical event is the M5 flare of 20 January 1999, presented by
McKenzie and Hudson (1999); since the time that paper was completed,
sixteen more events have been found in the interval April 1998 to
February 2000. As in the 20 January event, the speeds of downflow are
35-500 km s<SUP>-1</SUP>, lower than both the freefall speed and the
typically assumed Alfvén speed. The motion is evidenced by both dark
and bright (i.e., X-ray emitting) features, some of which may have a
looplike morphology; no cool counterparts have been detected in Hα
or EUV observations. Movies depicting some of the LDE downflows were
presented at this meeting; these also appear in the journal Solar
Physics (McKenzie, 2000), since they cannot be presented in these
Proceedings.
---------------------------------------------------------
Title: Melt Generation and Movement Beneath Theistareykir,
N.E. Iceland
Authors: McKenzie, D.; Slater, L.; Gronvold, K.; Shimizu, N. N.
2001eag..conf.3605M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Simultaneous Magnetographic and XUV Observations of a
Coronal Jet
Authors: McKenzie, D. E.; DeForest, C.
2001AGUSM..SH41A14M Altcode:
On 03 November 2000, a jet of hot plasma appeared in the solar corona,
and was observed by the Yohkoh Soft X-ray Telescope (SXT) and the
TRACE coronal imager. The jet of magnetically channeled plasma,
measuring over 280 megameters in length, serendipitously occurred
within the high-resolution field of view of the SOHO Michelson Doppler
Interferometer (MDI). We present the X-ray, extreme ultraviolet, and
magnetographic observations, and attempt to draw conclusions about
the evolution of the jet based upon the evolution of the magnetic field.
---------------------------------------------------------
Title: Active region transient brightenings. A simultaneous view by
SXT, EIT and TRACE
Authors: Berghmans, D.; McKenzie, D.; Clette, F.
2001A&A...369..291B Altcode:
This paper reports on a qualitative study on the weakest flarelike
brightenings in active region that can be observed with current
coronal imagers. Specificallly, we investigate the correspondence of
the “active region transient brightenings” (ARTB) first observed
almost a decade ago with SXT with similar brightenings in the EUV
that are now observed by EIT and TRACE. For this goal, exceptionally
high cadence image sequences were acquired of a small but rapidly
evolving active region (NOAA 8218), simultaneously by SXT, EIT, and
TRACE. Within the timeframe of this coordinated campaign, we detected
41 soft X-ray brightenings and 373 EUV brightenings. We find that the
strongest brightenings observed by EIT are indeed the EUV counterparts
of the ARTBs seen by SXT. Weaker brightenings seen by EIT often do not
have an X-ray counterpart. Among the brightenings detected with SXT we
discover a new subpopulation, consisting of events that brighten in soft
X-rays only, at a footpoint of a pre-existing SXT loop shortly after
an ARTB occurred at the other footpoint. The propagation speed of the
perturbation suggests an interpretation in terms of slow mode MHD waves.
---------------------------------------------------------
Title: Large Doppler Shifts in X-Ray Plasma: An Explosive Start to
Coronal Mass Ejection
Authors: Innes, D. E.; Curdt, W.; Schwenn, R.; Solanki, S.; Stenborg,
G.; McKenzie, D. E.
2001ApJ...549L.249I Altcode:
We report observations, taken with the Solar Ultraviolet Measurements
of Emitted Radiation spectrometer, of spatially resolved high red and
blue Doppler shifts (up to 650 km s<SUP>-1</SUP>) from X-ray-emitting
plasma in the corona above a flare. The high Doppler shifts are seen
minutes after a fast, faint optical front is seen racing through the
same part of the corona in images taken with the Mirror Coronagraph
for Argentina. The association of the large-scale fast optical emission
front with soft X-ray emission and high Doppler shifts suggests plasma
heating and acceleration in the wake of a shock.
---------------------------------------------------------
Title: Velocity Fields and Structure above LDE arcades: Possible
Observational Signatures of Reconnection
Authors: McKenzie, D. E.
2000SPD....31.0150M Altcode: 2000BAAS...32S1289M
In a growing number of CME events, the X-ray images from Yohkoh SXT
reveal velocity fields above the eruption site, directed downward into
the top of the flare arcade. These motions, with plane-of-sky speeds
typically between 50 -- 500 km s<SUP>-1</SUP>, are evidenced by both
dark (in X-rays) and bright (i.e., X-ray emitting) features, some
of which appear to have a looplike morphology. No counterparts have
been detected in simultaneous Hα or EUV imagery. The “supra-arcade
downflows" are tentatively interpreted as resulting from magnetic
field line shrinkage, a signature of outflow from reconnection sites
above the post-eruption arcade. I will present a summary of the flare
events in which these velocity fields have been detected (to date,
17 in the last two years), and movies showing the structure and motion
above some of the flare arcades. This work was supported by NASA under
Marshall Space Flight Center contract NAS8-40801 with the Lockheed
Martin Advanced Technology Center.
---------------------------------------------------------
Title: Observations of solar wave/instability phenomena as imaged
by EIT/SOHO, TRACE and Yohkoh/SXT
Authors: Berghmans, D.; McKenzie, D.
2000AIPC..537..168B Altcode: 2000wdss.conf..168B
On May 13 1998, active region NOAA 8218 was observed in the context
of the SOHO/JOP80 campaign by an array of 8 different ground-based and
space-born instruments. The emphasis was set on imaging of small-scale
dynamics in this relatively small but rapidly evolving AR. In
particular, SOHO/EIT (195 Å), TRACE (171 Å) and YOHKOH/SXT produced
subfield image sequences at their respective highest possible rates. We
searched for wave and instability phenomena by using an automated
recognition scheme. This result in a wide inventory of propagating
disturbances and localized transient brightenings. By comparing the
soft X-ray signature as recorded by SXT with the EUV-signature as
collected by EIT and TRACE, we are able to distinguish between various
types of active region transients. As such we find that the strongest
brightenings observed by EIT are indeed the EUV counterparts of the
previously reported ARTBs seen by SXT. Weaker brightenings seen by
EIT do often not have an X-ray counterpart. Moreover, in an extended
system of faint quasi-open loops, we find propagating disturbances, with
speeds of the order of 100 km/s, both in EIT and TRACE images. These are
interpreted as sonic perturbations. The brightenings will be discussed
in this paper while the propagating disturbances are described in the
presentation by Eva Robbrecht at this conference. .
---------------------------------------------------------
Title: Supra-arcade Downflows in Long-Duration Solar Flare Events
Authors: McKenzie, D. E.
2000SoPh..195..381M Altcode:
This report seeks to introduce the reader to a set of observations
made during the decay phase of long-duration event (LDE) flares
on the Sun. In a number of events, the soft X-ray images from
Yohkoh SXT indicate a downward-directed flow field in the region
immediately above the flare arcade. The prototypical event is the M5
flare of 20 January 1999, presented by McKenzie and Hudson (1999);
since the time that paper was completed, eleven more events, all
related to coronal mass ejections, have been found in the interval 1
January 1998 to 8 May 1999. As in the 20 January event, the speeds of
downflow are 45-500 km s<SUP>−1</SUP>, lower than both the free fall
speed and the typically assumed Alfvén speed. A comparison is drawn
between the SXT observations and the EUV and Hα data, where such are
available. Important additions to our knowledge since the first paper
are: (i) the motion is evidenced by both dark and bright (i.e., X-ray
emitting) features, some of which may have a loop-like morphology; (ii)
no cool counterparts have been detected in Hα or EUV observations. The
data are compared to the expected appearance according to two likely
(and opposing) interpretations: an `above-the-arcade coronal rain'
interpretation and a `shrinking magnetic flux tube' interpretation. In
the current standard explanation of the formation of post-CME arcades,
motion of the latter type may be related to outflow from a reconnection
site. Movies depicting some of the flare events are on the accompanying
CD-ROM.
---------------------------------------------------------
Title: Flexure of Venusian Lithosphere Measured from Residual
Topography
Authors: Barnett, D. N.; McKenzie, D.
2000LPI....31.1254B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Hard X-rays from "Slow LDEs"
Authors: Hudson, H. S.; McKenzie, D. E.
2000ASPC..206..221H Altcode: 2000hesp.conf..221H
No abstract at ADS
---------------------------------------------------------
Title: Multi-Imager Study of Transients and Propagating Disturbances
in Active Region Loops (SOHO JOP80 Campaign)
Authors: Berghmans, D.; Clette, F.; Robbrecht, E.; McKenzie, D.
1999ESASP.448..575B Altcode: 1999ESPM....9..575B; 1999mfsp.conf..575B
No abstract at ADS
---------------------------------------------------------
Title: Active Region Transient Brightenings : EIT Versus SXT
Authors: Berghmans, D.; McKenzie, D.; Clette, F.
1999ESASP.446..173B Altcode: 1999soho....8..173B
On May 13, 1998, the Extreme-Ultraviolet Imaging Telescope (EIT,
on board SOHO) has produced a unique image sequence operating in
'shutterless mode' (SOHO JOP 80). In JOP 80, EIT is the leading
instrument, followed by several space born instruments (SXT, TRACE,
MDI, CDS, SUMER), as well as two observatories on the ground (in La
Palma and Sac Peak). The target of the campaign was a relatively small
but rapidly evolving active region (AR 8218). For the EIT contribution,
a 15 s cadence was achieved in the Fe XII bandpass at 195 deg by leaving
EIT's shutter open for 1 hour and operating the CCD in frame transfer
mode. We have started the analysis of the huge data set, by making an
inventory of the transients observed in the EIT image sequence. These
transients range from a B3.5 flare producing a large plasma flow along
pre-existing loops, to smaller EUV brightenings of active region
loops. In addition, a new class of weaker footpoint brightenings
was discovered that produce wave-like disturbances propagating along
quasi-open field lines (see the presentation by Eva Robbrecht at this
workshop). In this paper we take the opportunity provided by JOP 80,
to investigate the correspondence of the transient brightenings observed
by EIT in this active region, with the ARTB previously observed by SXT
and studied by Shimizu (1992). Within the simultaneous high cadence
SOHO JOP 80 image sequences, both EIT and SXT accummulated a few tens
of brightening events. At the time of the writing of this abstract,
we can say that most of the SXT events have indeed 1 or more EIT
counterparts. Typically the SXT events are somewhat bigger than the EIT
events where the latter are ussualy located toward the point of origin
of the SXT events. Whereas a few brightenings exist in one dataset
without any trace in the other dataset (in both directions), we have
additionally for a few brightenings in the SXT data, a corresponding
EIT darkening as if the plasma is suddenly heated and dissappears from
the EIT passband.
---------------------------------------------------------
Title: X-Ray Observations of Motions and Structure above a Solar
Flare Arcade
Authors: McKenzie, D. E.; Hudson, H. S.
1999ApJ...519L..93M Altcode:
In this Letter, we describe a solar flare that was observed by Yohkoh
in 1999 January 20. This long-duration event is notable because the
Yohkoh images show not only the formation of the arcade associated
with the coronal mass ejection but also a considerable amount of motion
above the arcade in the region normally identified with a large-scale
current sheet or the outflow from magnetic reconnection in the current
sheet. A number of arcade events of this morphological type (i.e.,
a fan of spikelike “rays” above the posteruption loops) have been
seen by Yohkoh, but in this case we have a much clearer view of mass
motions in the region above the arcade. The motions indicate field-line
retraction without the formation of long-lasting cusps during the rise
phase of the flare, and a downward flow above the arcade during the
decay phase. The late-phase downward motion is in the form of X-ray
dark voids moving at 100-200 km s<SUP>-1</SUP>, i.e., at velocities
much smaller than the free-fall speed or the assumed Alfvén speed. We
interpret the voids as cross sections of evacuated flux tubes resulting
from intermittent reconnection following the associated coronal mass
ejection. We believe these data represent the first direct evidence
of high-speed flows in the region immediately above the flare loops.
---------------------------------------------------------
Title: Making YOHKOH SXT Images Available to the Public: The YOHKOH
Public Outreach Project
Authors: Larson, M. B.; McKenzie, D.; Slater, T.; Acton, L.; Alexander,
D.; Freeland, S.; Lemen, J.; Metcalf, T.
1999AAS...194.7024L Altcode: 1999BAAS...31..941L
The NASA funded Yohkoh Public Outreach Project (YPOP) provides public
access to high quality Yohkoh SXT data via the World Wide Web. The
products of this effort are available to the scientific research
community, K-12 schools, and informal education centers including
planetaria, museums, and libraries. The project utilizes the intrinsic
excitement of the SXT data, and in particular the SXT movies, to develop
science learning tools and classroom activities. The WWW site at URL:
http://solar.physics.montana.edu/YPOP/ uses a movie theater theme to
highlight available Yohkoh movies in a format that is entertaining and
inviting to non-scientists. The site features informational tours of
the Sun as a star, the solar magnetic field, the internal structure
and the Sun's general features. The on-line Solar Classroom has proven
very popular, showcasing hand-on activities about image filtering,
the solar cycle, satellite orbits, image processing, construction of a
model Yohkoh satellite, solar rotation, measuring sunspots and building
a portable sundial. The YPOP Guestbook has been helpful in evaluating
the usefulness of the site with over 300 detailed comments to date.
---------------------------------------------------------
Title: Arcade Structure and Dynamics in the 20-Jan-99 M5 Solar Flare
Authors: McKenzie, D. E.; Hudson, H. S.
1999AAS...19410108M Altcode: 1999BAAS...31..999M
We present observations of a remarkable solar flare which was observed
by Yohkoh on 20-Jan-99. This long duration event is notable because the
Yohkoh images show not only the formation of the arcade associated with
the coronal mass ejection, but also a considerable amount of structure
and motion in the current sheet above the arcade. Though not unique, the
structure of this arcade is different from the majority of flare arcades
observed by Yohkoh. The motions indicate field line shrinkage during the
rise phase of the flare, and downward flow above the arcade during the
decay phase. The late-phase downward motion suggests the possibility
either of a high-Beta regime in the current sheet, or of shrinkage of
evacuated flux tubes downward through the current sheet. This research
is supported by NASA under MSFC contract NAS8-40801.
---------------------------------------------------------
Title: Crustal and Elastic Thickness Estimates for the Moon
Authors: Nimmo, F.; McKenzie, D.
1999LPI....30.1325N Altcode:
The crustal thickness of non-mascon lunar areas is about 45 km,
assuming isostasy. The elastic thickness of the South Pole-Aitken
Basin is about 5 km. These areas are weak, implying they must have
formed early in the Moon's history.
---------------------------------------------------------
Title: A Stable Filament Cavity with a Hot Core
Authors: Hudson, H. S.; Acton, L. W.; Harvey, K. L.; McKenzie, D. E.
1999ApJ...513L..83H Altcode:
We present observations of a long-lived solar filament cavity with
soft X-ray sources along its axis. This structure appeared above the
southern polar crown polarity-inversion line for approximately three
rotations during 1997 June-August, centered at a west-limb passage on
approximately July 3. At the limb, the Yohkoh soft X-ray data showed
a bright region situated above and around the projected filament
location but near the axis of the cavity. We describe measurements
of the geometry of the cavity, which we interpret as a flux rope that
is partially embedded in the photosphere, and use the Yohkoh data to
describe the physical parameters of the structure. We find that the
core consists of an unresolved mass of filamentary substructures, with a
volume filling factor significantly less than unity for the soft X-ray
telescope (SXT) resolution. The core has a higher temperature than the
cavity surrounding it, ruling out explanations in terms of a transition
region supported by thermal conduction. Transient activity occurred in
the polar crown region, but no detectable destabilization or eruption
of the cavity structure resulted from it. We suggest that the bright
structure at the core of the cavity corresponds to higher altitude
coronal segments of the field lines that support the filament material.
---------------------------------------------------------
Title: Sigmoidal morphology and eruptive solar activity
Authors: Canfield, Richard C.; Hudson, Hugh S.; McKenzie, David E.
1999GeoRL..26..627C Altcode:
Soft X-ray images of solar active regions frequently show S- or
inverse-S (sigmoidal) morphology. We have studied the Yohkoh Soft
X-Ray Telescope video movie for 1993 and 1997. We have classified
active regions according to morphology (sigmoidal or non-sigmoidal)
and nature of activity (eruptive or non-eruptive). As well, we have
used NOAA sunspot areas for each region as a measure of size. We find
that regions are significantly more likely to be eruptive if they are
either sigmoidal or large.
---------------------------------------------------------
Title: Deglaciation effects on mantle melting under Iceland: results
from the northern volcanic zone
Authors: Slater, L.; Jull, M.; McKenzie, D.; Gronvöld, K.
1998E&PSL.164..151S Altcode:
A striking feature of Icelandic volcanism is the effect that the last
ice age had on volcanic activity. After the final retreat of ice ∼11
kyr BP, the average eruption rate is estimated to have been 20-30 times
greater than it is today. This increase has been attributed to the
release of pooled magma through differential tectonic movements during
the unloading of ice. However recent work has shown that deglaciation
can account for the increase in mantle melting by decreasing the
pressure in the upper mantle. We present geochemical data and volume
estimates of erupted magmas from Iceland's northern neovolcanic zone
which show that the average composition of magmas erupted during
the last glacial period in Iceland are significantly more enriched
in incompatible trace elements than postglacial and interglacial
lavas. The difference in light rare earth element concentrations
cannot be accounted for by liquid-crystal fractionation. Averaging
the compositions of glacial and postglacial magmas also eliminates
the likelihood that the compositional change is due to variations in
source composition. An increase in mantle melting from deglaciation
can account for both the magma eruption rate and observed changes in
trace element concentrations. Finite transport times for magma to
travel from the source region to the surface can be estimated from
the delay in timing of the increased eruption rates and the end of the
last glacial period. This gives transport times of about 1-3 kyr and
is consistent with estimates from ( <SUP>226</SUP>Ra/ <SUP>230</SUP>Th)
activity ratios measured in ocean island and mid-ocean ridge basalts.
---------------------------------------------------------
Title: A space-age portrait of the active sun
Authors: McKenzie, David E.; Slater, Timothy F.
1998PhTea..36..403M Altcode:
Recent observations from space observatories focused on high energy
emission from the Sun has provided both exciting science and beautiful
pictures, particularly in X-ray wavelengths. This manuscript is adapted
from an invited Frontiers in Astronomy talk given at the AAPT Winter
Meeting, New Orleans, January 1998 on current research in solar physics.
---------------------------------------------------------
Title: Modelling Plume-related Uplift, Gravity and Melting on Mars
Authors: Nimmo, F.; McKenzie, D.
1998LPI....29.1783N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Martian Dikes, Outflow Channels and Valles Marineris
Authors: McKenzie, D.; Nimmo, F.
1998LPI....29.1778M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Volcanism and Tectonics on Venus
Authors: Nimmo, F.; McKenzie, D.
1998AREPS..26...23N Altcode:
We review recent developments in the study of volcanism and tectonics
on Venus. Venus's crust is basaltic, dry, and probably about 30~km
thick. The mantle convects, giving rise to plumes, and has a similar
composition and mean temperature (~1300 deg C), but a higher viscosity
(~10^20 Pa s), than that of the Earth. Inferred melt generation rates
constrain the lithospheric thickness to between 80 and 200 km. The
elastic thickness of the lithosphere is about 30 km on average. The
present-day lack of plate tectonics may be due to strong faults and the
high viscosity of the mantle. Most of the differences between Earth
and Venus processes can be explained by the absence of water. Venus
underwent a global resurfacing event 300--600 Ma ago, the cause and
nature of which remains uncertain. The present-day surface heat flux on
Venus is about half the likely radiogenic heat generation rate, which
suggests that Venus has been heating up since the resurfacing event.
---------------------------------------------------------
Title: Periodic Modulation of X-Ray Intensity from Coronal Loops -
Heating by Resonant Absorption?
Authors: McKenzie, D. E.; Mullan, D. J.
1997SoPh..176..127M Altcode:
We have applied time-series analysis to sequences of coronal loop images
obtained with the Yohkoh soft X-ray telescope (SXT). Using images
obtained in fast-cadence mode (δ t = 4 s), we have generated X-ray
light curves and power spectra for multiple subregions of a number
of coronal loops. Our analysis indicates that out of 544 spectra
of loops which range in length L from 40 Mm to 150 Mm, there are
16 cases where the X-ray brightness is modulated periodically with
≥99.5% confidence. The periods τ range from 9.6 s to 61.6 s, and
the amplitudes range from 0.4% to 1.8%. Our result is statistically
significant at the 8σ level.
---------------------------------------------------------
Title: Search for Periodicity in Image Sequences from YOHKOH Soft
X-Ray Telescope
Authors: McKenzie, David Eugene
1997PhDT.........9M Altcode:
The process by which the Sun's corona is heated is not well known. A
leading model is the resonant absorption of Alfvenic surface waves. In
order to be efficient as a heating mechanism, this process depends on
the surface waves being well matched to the length of the coronal loop
through the condition of global-mode resonance: v<SUB> Alfvén</SUB>
= 2L/period (Davila 1987). The Yohkoh Soft X-Ray Telescope provides a
means of recording the behavior and evolution of structures in the solar
corona. Relatively fast-cadence sequences of CCD images become movies
depicting the changing conditions in the X-ray emitting regions. By
using software provided by the Yohkoh science team to measure the
brightness of a selected subset of pixels in all the images of a movie,
we can generate an X-ray light curve of a small portion of a given
coronal structure. For the present dissertation, a number of SXT image
sequences were selected from the Yohkoh archives. Light curves were
generated in the manner outlined above, and these light curves were then
examined for periodic modulations. It is shown that periodic modulations
of X-ray brightness were detected with amplitudes of about 1%, and that
the speeds implied by global-mode resonance are in the neighborhood of
1800-14000 km/s, consistent with Alfven wave speeds but much higher than
sound speeds implied by the temperatures measured from the images. The
wave speeds and the modulation amplitudes imply plasma beta values in
the range β<SUB> p</SUB> ≈ 10<SUP>-3</SUP>-10<SUP>-2</SUP>. Tests
for correlations among physical conditions (loop length L, temperature
T, pressure p, modulation depth ΔI/I, quality Q, and period τ) in
the periodically modulated loops tentatively support relationships
like T ~ (pL)<SUP>1/3</SUP>, after Rosner et al. (1978), and Q ~
(Δ I/I)<SUP>-2</SUP>, after Zaitsev & Stepanov (1989), but do
not support relationships like L ~ τ,/ L ~ p,/ L ~ T, or p ~ τ.
---------------------------------------------------------
Title: Search for Periodicity in Image Sequences from the Yokoh Soft
X-Ray Telescope
Authors: McKenzie, D. E.
1997PASP..109..739M Altcode:
The process by which the Sun's corona is heated is not well known. A
leading model is the resonant absorption of Alfvénic surface waves. In
order to be efficient as a heating mechanism, this process depends on
the surface waves being well matched ot the length of the coronal loop
through the condition of global-mode resonance: $v_{Alfv\acute{e}n}$
= 2L/period (Davila, 1987). The Yohkoh Soft X-Ray Telescope (SXT)
provides a means of recording the behavior and evolution of structures
in the solar corona. Relatively fast-cadence sequences of CCD images
become movies depicting the changing conditions in the X-ray emitting
regions. By using software provided by the Yohkoh science team to
measure the brightness of a selected subset of pixels in all the images
of a movie, we can generate an X-ray light curve of a small portion of a
given coronal structure. For the present dissertation, a number of SXT
image sequences were selected from the Yohkoh archives. Light curves
were generated in the manner outlined above, and these light curves
were then examined for periodic modulations. It is shown that periodic
modulations of X-ray brightness were detected with amplitudes of nearly
1\%, and that the speeds inferred from interpreting these oscillations
as global-mode resonance are in the neighborhood of 1800 -- 14000 km/s,
consistent with Alfvén wave speeds but much higher than sound speeds
implied by the temperatures measured from the images. The wave speeds
and the modulation amplitudes imply plasma beta values in the range
$\beta_p \approx 10^{-3} -- 10^{-2}$. (SECTION: Dissertation Summaries)
---------------------------------------------------------
Title: Search for Periodicity in Image Sequences from YOHKOH Soft
X-Ray Telescope
Authors: McKenzie, D. E.
1997SPD....28.0704M Altcode: 1997BAAS...29..911M
We have applied time-series analysis to sequences of coronal loop
images obtained with the Yohkoh Soft X-Ray Telescope (SXT). Using images
obtained in fast-cadence mode (Delta t = 4 sec), we have generated X-ray
light curves and power spectra for multiple subregions of a number
of coronal loops. Our analysis indicates that out of 544 spectra of
loops which range in length L from 40 Mm to 150 Mm, there are 16 cases
where the X-ray brightness is modulated periodically with >=99.5%
confidence. The periods tau range from 9.6 sec to 61.6 sec, and the
amplitudes range from 0.4% to 1.8%. Our result is statistically
significant at the 8sigma level. The observed periods can hardly
be due to fluctuations in gas pressure: temperatures estimated from
image ratios indicate sound speeds of 200 -- 280 km/sec, with loop
crossing times of hundreds of seconds. On the other hand, the ratio
2 L / tau yields “velocities" of 2 -- 14 Mm/sec: these overlap with
published estimates of Alfven speeds v_A in coronal loops, 3.5 -- 37
Mm/sec (Schmelz et al., 1994, ApJ, 434, 786). Now, in the context of
coronal loop heating by resonant absorption of MHD waves, the period
tau_g ~ 2 L / v_A plays a key role: loops which are oscillating in
their global mode (with period tau_g ) are maximally efficient at
absorbing energy (Steinolfson and Davila, 1993, ApJ, 415, 354). We
suggest that the loops which we have found to be modulated periodically
are oscillating in their global mode. With this interpetation, we find
that the plasma beta in the loops lies in the range beta _p = 0.001 --
0.045. According to the oscillating loop model of Zaitsev and Stepanov
(1989, Sov. Astron. Letters, 15, 66), loops with such beta _p values
should be modulated with amplitudes of 1.1% or less: our data are
consistent with at least the upper limit of this prediction.
---------------------------------------------------------
Title: Using the WWW to Make YOHKOH SXT Images Available to the
Public: The YOHKOH Public Outreach Project
Authors: Larson, M.; McKenzie, D.; Slater, T.; Acton, L.; Alexander,
D.; Freeland, S.; Lemen, J.; Metcalf, T.
1997SPD....28.0231L Altcode: 1997BAAS...29..898L
The Yohkoh Public Outreach Project (YPOP) is funded by NASA as one of
the Information Infrastructure Technology and Applications Cooperative
Agreement Teams to create public access to high quality Yohkoh SXT data
via the World Wide Web. These products are being made available to the
scientific research community, K-12 schools, and informal education
centers including planetaria, museums, and libraries. The project aims
to utilize the intrinsic excitement of the SXT data, and in particular
the SXT movies, to develop science learning tools and classroom
activities. The WWW site at URL: http://www.space.lockheed.com/YPOP/
uses a movie theater theme to highlight available Yohkoh movies in a
non-intimidating and entertaining format for non-scientists. The site
features lesson plans, 'solar' activities, slide shows and, of course,
a variety of movies about the Sun. Classroom activities are currently
undergoing development with a team of scientists and K-12 teachers
for distribution in late 1997. We will display the products currently
online, which include a solar classroom with activities for teachers,
background resources, and a virtual tour of our Sun.
---------------------------------------------------------
Title: Using the World Wide Web to Make YOHKOH SXT Images Available
to the Public: The YOHKOH Public Outreach Project
Authors: McKenzie, D.; Larson, M. B.; Slater, T.; Acton, L.; Alexander,
D.; Freeland, S.; Lemen, J.; Metcalf, T.
1997ESASP.404..561M Altcode: 1997cswn.conf..561M
No abstract at ADS
---------------------------------------------------------
Title: Modeling plume-related melting, uplift and gravity on Venus
Authors: Nimmo, F.; McKenzie, D.
1997E&PSL.145..109N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Average lithospheric structure of southern Africa
Authors: Qiu, X.; Priestley, K.; McKenzie, D.
1996GeoJI.127..563Q Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Magnetic Wave Resonance in Solar Coronal Structures
Authors: McKenzie, D. E.
1995SPD....26..703M Altcode: 1995BAAS...27..966M
No abstract at ADS
---------------------------------------------------------
Title: Ultralow temperature resonant-mass gravitational radiation
detectors: current status of the Stanford program.
Authors: Michelson, P. F.; Mann, L.; Penny, R.; Henderson, J.;
McKenzie, D.; Zhou, C.
1995gwe..conf..195M Altcode: 1995grwa.conf..195M
The main focus of the Stanford program during the past year has
been on completing the design of a second generation resonant-mass
detector designed to operate at 50 mK with an rms noise level for
burst detection approaching h ≡ 10<SUP>-20</SUP>. The design is
complete and final detector assembly is underway. It is expected
to begin initial operation in the first quarter of next year. After
establishing reliable operation of the new detector, the principal
goal during the next few years is to operate it in coincidence with
other gravitational radiation detectors including a similar ultralow
temperature detector that has been constructed by the University of
Rome. Improving energy sensitivity by about four orders-of-magnitude
beyond that currently available from resonant-mass detectors (now
routinely operating at 4 K) will be a major milestone for the field.
---------------------------------------------------------
Title: Radioactive disequilibria from 2D models of melt generation
by plumes and ridges
Authors: Richardson, C.; McKenzie, D.
1994E&PSL.128..425R Altcode:
We present a simple method of calculating radiogenic excesses caused by
the melting process in 2D models of melting regions. <SUP>238</SUP>U
series disequilibrium in basalt from recent Hawaiian eruptions can be
explained using an axisymmetric plume model and a melt parameterisation
based on laboratory experiments. The model is also applied to mid-ocean
ridges and shows that the disequilibria are controlled by the mean
melting rate at the base of the melting region and by the melt
fraction present during melting. ( <SUP>230</SUP>Th/<SUP>235</SUP>U)
data constrains the mean melting rate at the onset of melting to
less than 8 × 10 <SUP>-8</SUP> yr <SUP>-1</SUP>, which is consistent
with that expected from the experimental parameterisation. Limited (
<SUP>231</SUP>Pa/<SUP>235</SUP>U) data give a maximum initial melting
rate of 0.4 × 10 <SUP>-8</SUP> yr <SUP>-1</SUP>. Melting begins in
the garnet peridotite stability field and melt extraction is rapid (
∼ 2000 yr). Extraction on this time scale is most easily explained if
melt transport is by channel flow. The geochemical observations require
the melt fraction in the region where U, Th and Ra are extracted from
the source to be ∼ 0.1%, in agreement with estimates from a simple
fluid dynamical model of melt separation.
---------------------------------------------------------
Title: Transient Period Found in the BY Dra Variable OU Geminorum
Authors: McKenzie, D. E.; Herr, R. B.
1994IBVS.4014....1M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Reply to the comment by R. Westaway on 'Active tectonics of the
north and central Aegean Sea' by T. Taymaz, J. Jackson and D. McKenzie
Authors: Taymaz, T.; Jackson, J.; McKenzie, D.
1992GeoJI.110..623T Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Venus Tectonics: Initial Analysis from Magellan
Authors: Solomon, S. C.; Head, J. W.; Kaula, W. M.; McKenzie, D.;
Parsons, B.; Phillips, R. J.; Schubert, G.; Talwani, M.
1991Sci...252..297S Altcode:
Radar imaging and altimetry data from the Magellan mission have
revealed a diversity of deformational features at a variety of spatial
scales on the Venus surface. The plains record a superposition of
different episodes of deformation and volcanism; strain is both areally
distributed and concentrated into zones of extension and shortening. The
common coherence of strain patterns over hundreds of kilometers
implies that many features in the plains reflect a crustal response
to mantle dynamic processes. Ridge belts and mountain belts represent
successive degrees of lithospheric shortening and crustal thickening;
the mountain belts also show widespread evidence for extension and
collapse both during and following crustal compression. Venus displays
two geometrical patterns of concentrated lithospheric extension:
quasi-circular coronae and broad rises with linear rift zones; both
are sites of significant volcanism. No long, large-offset strike-slip
faults have been observed, although limited local horizontal shear
is accommodated across many zones of crustal shortening. In general,
tectonic features on Venus are unlike those in Earth's oceanic regions
in that strain typically is distributed across broad zones that are
one to a few hundred kilometers wide, and separated by stronger and
less deformed blocks hundreds of kilometers in width, as in actively
deforming continental regions on Earth.
---------------------------------------------------------
Title: Venus Tectonics: The Perspective from Magellan at the
Half-way Point
Authors: Solomon, S. C.; Head, J. W.; Kaula, W. M.; McKenzie, D.;
Parsons, B. E.; Phillips, R. J.; Schubert, G.; Squyres, S. W.;
Talwani, M.
1991LPI....22.1299S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Tectonic Evolution of Lavinia Planitia, Venus
Authors: Squyres, S. W.; Frank, S. L.; McGill, G. E.; McKenzie, D.;
Parsons, B. E.; Solomon, S. C.
1991LPI....22.1309S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Melt generation by plumes: A study of Hawaiian volcanism
Authors: Watson, S.; McKenzie, D.
1991JPet...32..501W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Ultralow temperature resonant-mass gravitational radiation
detectors: current status and future prospects
Authors: Michelson, P. F.; Aldcroft, T.; Chiang, J.; Debra, D.;
Henderson, J.; Mann, L.; McKenzie, D.; McLoughlin, F.; Paik, H. J.;
Penny, R.; Price, J. C.; Stevenson, T.; Vaughan, B.; Zhou, C.; Hansen,
W. W.
1991gaid.conf...14M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The volume and composition of melt generated by extension of
the lithosphere
Authors: McKenzie, D.; Bickle, M. J.
1988JPet...29..625M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The existence of a thin low-viscosity layer beneath the
lithosphere
Authors: Craig, C. H.; McKenzie, D.
1986E&PSL..78..420C Altcode:
The horizontal temperature gradient at the base of the lithosphere at
an oceanic fracture zone, where plate of different ages is juxtaposed,
is expected to drive a local circulation, the characteristics of which
can be constrained by the amplitude, wavelength and age-dependence of
the geoid. Two-dimensional numerical models of convection in a fluid
layer overlain by a solid conducting lid have been used to generate
theoretical geoid profiles at right angles to the fracture zone. Only
a thin, low-viscosity layer provides a reasonable fit to the data. The
best model so far obtained has a fluid layer 150 km thick with viscosity
1.5 × 10 <SUP>19</SUP> Pa s under a 75 km lid. Such a layer, which
is incapable of transmitting strong horizontal shear stresses, could
provide the decoupling mechanism between plate and deep mantle flow
required to balance the forces on the plates.
---------------------------------------------------------
Title: A possible mechanism for epeirogenic uplift
Authors: McKenzie, D.
1984Natur.307..616M Altcode:
Continental geology is dominated by vertical movements, some of these
are the result of crustal shortening and extension associated with
large horizontal displacements, involving processes which are now
understood, at least in outline. However, both uplift and subsidence
can occur without associated shortening or extension of the continental
crust. Most investigations of such epeirogenic movements have been
concerned with subsidence, partly because of the economic importance of
the resulting sedimentary basins, and partly because of the existence
of a simple model for the process<SUP>1</SUP> which can account for the
development of several basins in some detail<SUP>2-4</SUP>. However,
uplift has been relatively neglected and cannot be produced by the same
mechanism. The purpose of this paper is to examine whether epeirogenic
uplift can result from the intrusion of large thicknesses of basic
magma into the lower part of continental crust. This suggestion was
considered as a possible mechanism for the regional uplift of the
Colorado Plateau by Gilbert<SUP>5</SUP> more than 100 years ago, and
also by Holmes<SUP>6</SUP> (though both rejected the idea). However, a
recent discussion of no less than 14 different mechanisms for generating
uplift<SUP>7</SUP> did not include this process, even though it seems
able to produce the observed vertical motions and also to account for
some of the features of the evolution of sedimentary basins that cannot
be explained by the uniform stretching model<SUP>3,8,9</SUP>. Although
the suggestion is not new, the argument used here to support it is,
and depends on an understanding of the relationship between ocean
island volcanoes and mantle circulation.
---------------------------------------------------------
Title: The generation and compaction of partially molten rock
Authors: McKenzie, D.
1984JPet....5..713M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The depth of seismicity in the Kermanshah region of the Zagros
Mountains (Iran)
Authors: Niazi, M.; Asudeh, I.; Ballard, G.; Jackson, J.; King, G.;
McKenzie, D.
1978E&PSL..40..270N Altcode:
A detailed microearthquake survey in a small region of the Zagros
Mountains in Iran failed to detect any shocks whose depths were greater
than 20 km. One third of the shocks in the same area have depths greater
than 50 km when located using teleseismic observations. Because of
poor azimuthal coverage and lack of local stations these teleseismic
locations are probably in error. There is therefore no reliable seismic
evidence for the existence of oceanic lithosphere beneath the Zagros
fold belt.
---------------------------------------------------------
Title: Surface deformation, gravity anomalies and convection.
Authors: McKenzie, D.
1977GeoJ...48..211M Altcode: 1977GeoJI..48..211M
No abstract at ADS
---------------------------------------------------------
Title: Geomagnetism in Marine Geology. V. Vacquier, 1972. Elsevier,
Amsterdam, 1972, 200 pp., Ofl.42.50
Authors: McKenzie, D.
1973ESRv....9Q.289M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A Comparison of Thermal and Non-thermal Solar Flare X-ray
Emission Observed on OSO-7
Authors: Datlowe, D.; McKenzie, D.
1972BAAS....4Q.380D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: De-Occultation X-Ray Events of 2 December, 1967
Authors: Zirin, Harold; Ingham, William; Hudson, Hugh; McKenzie, David
1969SoPh....9..269Z Altcode:
A flare rising from behind the solar limb was recorded simultaneously
by the UCSD X-ray detector on OSO-III (7.7-200 keV) and the Caltech
photoheliograph on Robinson Laboratory roof (Hα). The de-occultation
gives excellent spatial resolution of the X-ray source. Spectra
suggest that the material was already heated to 27 000 000° and that
the increase in flux was due to the de-occultation. The flux rise to
maximum was proportional to the apparent area. The uniformity of this
rise shows that there was no special kernel of emission. Comparison
of the deduced volume with the bremsstrahlung formula gives a density
of about 10<SUP>10</SUP> for the 27 000 000° component of the flare;
this is confirmed by consideration of the maximum possible coulomb
braking. The actual decay is more likely by escape rather than coulomb
braking.
---------------------------------------------------------
Title: De-occultation x-Ray Event of 2 December 1967
Authors: Hudson, Hugh; McKenzie, David; Zirin, Harold; Ingham, William
1969BAAS....1T.280H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Upper Limit Solar Gamma-Ray Spectrum to 10 Mev
Authors: Peterson, Laurence E.; Schwartz, Daniel A.; Pelling, R. M.;
McKenzie, David
1966JGR....71.5778P Altcode:
In this Letter we wish to report new upper limits on solar γ rays
obtained from a balloon flight series in February 1966. These
results, when combined with other recent work, form a composite
upper-limit γ-ray spectrum from the quiet sun over the range 20 kev
to 10 Mev, which is about a factor of 30 lower than that previously
available. Since several experimental techniques were used to cover
this large energy range, the results in the 20-200-kev range will be
presented first, followed by the 1-10-Mev work. Upper limits in the
130-800-kev region are available from previous work [Frost et al.,
1966].