Author name code: mcintosh
ADS astronomy entries on 2022-09-14
author:"McIntosh, Scott W."
------------------------------------------------------------------------
Title: Uniting The Sun's Hale Magnetic Cycle and `Extended Solar
Cycle' Paradigms
Authors: McIntosh, Scott W.; Scherrer, Phillip H.; Svalgaard, Leif;
Leamon, Robert J.
Bibcode: 2022arXiv220809026M
Altcode:
Through meticulous daily observation of the Sun's large-scale magnetic
field the Wilcox Solar Observatory (WSO) has catalogued two magnetic
(Hale) cycles of solar activity. Those two (~22-year long) Hale cycles
have yielded four ($\sim$11-year long) sunspot cycles (numbers 21
through 24). Recent research has highlighted the persistence of the
"Extended Solar Cycle" (ESC) and its connection to the fundamental Hale
Cycle - albeit through a host of proxies resulting from image analysis
of the solar photosphere, chromosphere and corona. This short manuscript
presents the correspondence of the ESC, the surface toroidal magnetic
field evolution, and the evolution of the Hale Cycle. As Sunspot Cycle
25 begins, interest in observationally mapping the Hale and Extended
cycles could not be higher given potential predictive capability that
synoptic scale observations can provide.
Title: The Eclipse Megamovie Project (2017)
Authors: Hudson, Hugh S.; Peticolas, Laura; Johnson, Calvin; White,
Vivian; Bender, Mark; Pasachoff, Jay M.; Martínez Oliveros, Juan
Carlos; Collier, Braxton; Filippenko, Alexei V.; Filippenko, Noelle;
Fraknoi, Andrew; Guevara Gómez, Juan Camilo; Koh, Justin; Konerding,
David; Krista, Larisza; Kruse, Brian; McIntosh, Scott; Mendez, Brian;
Ruderman, Igor; Yan, Darlene; Zevin, Dan
Bibcode: 2022arXiv220713704H
Altcode:
The total solar eclipse of August 21, 2017, crossed the whole width
of North America, the first occasion for this during the modern age
of consumer electronics. Accordingly, it became a great opportunity
to engage the public and to enlist volunteer observers with relatively
high-level equipment; our program ("Eclipse Megamovie") took advantage
of this as a means of creating a first-ever public database of such
eclipse photography. This resulted in a large outreach program,
involving many hundreds of individuals, supported almost entirely
on a volunteer basis and with the institutional help of Google, the
Astronomical Society of the Pacific, and the University of California,
Berkeley. The project home page is \url{http://eclipsemegamovie.org},
which contains the movie itself. We hope that our comments here will
help with planning for similar activities in the total eclipse of
April 8, 2024.
Title: Magnetoseismology for the solar corona: from 10 Gauss to
coronal magnetograms
Authors: Yang, Zihao; Gibson, Sarah; He, Jiansen; Del Zanna, Giulio;
Tomczyk, Steven; Morton, Richard; McIntosh, Scott; Wang, Linghua;
Karak, Bidya Binay; Samanta, Tanmoy; Tian, Hui; Chen, Yajie; Bethge,
Christian; Bai, Xianyong
Bibcode: 2022cosp...44.2490Y
Altcode:
Magnetoseismology, a technique of magnetic field diagnostics based
on observations of magnetohydrodynamic (MHD) waves, has been widely
used to estimate the field strengths of oscillating structures in
the solar corona. However, previously magnetoseismology was mostly
applied to occasionally occurring oscillation events, providing
an estimate of only the average field strength or one-dimensional
distribution of field strength along an oscillating structure. This
restriction could be eliminated if we apply magnetoseismology to the
pervasive propagating transverse MHD waves discovered with the Coronal
Multi-channel Polarimeter (CoMP). Using several CoMP observations of
the Fe XIII 1074.7 nm and 1079.8 nm spectral lines, we obtained maps of
the plasma density and wave phase speed in the corona, which allow us
to map both the strength and direction of the coronal magnetic field
in the plane of sky. We also examined distributions of the electron
density and magnetic field strength, and compared their variations
with height in the quiet Sun and active regions. Such measurements
could provide critical information to advance our understanding of the
Sun's magnetism and the magnetic coupling of the whole solar atmosphere.
Title: Simulating Solar Near-surface Rossby Waves by Inverse Cascade
from Supergranule Energy
Authors: Dikpati, Mausumi; Gilman, Peter A.; Guerrero, Gustavo
A.; Kosovichev, Alexander G.; McIntosh, Scott W.; Sreenivasan,
Katepalli. R.; Warnecke, Jörn; Zaqarashvili, Teimuraz V.
Bibcode: 2022ApJ...931..117D
Altcode:
Rossby waves are found at several levels in the Sun, most recently in
its supergranule layer. We show that Rossby waves in the supergranule
layer can be excited by an inverse cascade of kinetic energy from the
nearly horizontal motions in supergranules. We illustrate how this
excitation occurs using a hydrodynamic shallow-water model for a 3D
thin rotating spherical shell. We find that initial kinetic energy
at small spatial scales inverse cascades quickly to global scales,
exciting Rossby waves whose phase velocities are similar to linear
Rossby waves on the sphere originally derived by Haurwitz. Modest
departures from the Haurwitz formula originate from nonlinear finite
amplitude effects and/or the presence of differential rotation. Like
supergranules, the initial small-scale motions in our model contain
very little vorticity compared to their horizontal divergence, but the
resulting Rossby waves are almost all vortical motions. Supergranule
kinetic energy could have mainly gone into gravity waves, but we find
that most energy inverse cascades to global Rossby waves. Since kinetic
energy in supergranules is three or four orders of magnitude larger
than that of the observed Rossby waves in the supergranule layer,
there is plenty of energy available to drive the inverse-cascade
mechanism. Tachocline Rossby waves have previously been shown to
play crucial roles in causing seasons of space weather through their
nonlinear interactions with global flows and magnetic fields. We briefly
discuss how various Rossby waves in the tachocline, convection zone,
supergranule layer, and corona can be reconciled in a unified framework.
Title: Editorial: Horizons in Astronomy and Astrophysics
Authors: McIntosh, Scott W.; Marziani, Paola; Puzzarini, Cristina;
Howell, Steve B.
Bibcode: 2022FrASS...9.1370M
Altcode:
No abstract at ADS
Title: Deciphering Solar Magnetic Activity: The Solar Cycle Clock
Authors: Leamon, Robert J.; McIntosh, Scott W.; Title, Alan M.
Bibcode: 2022FrASS...9.6670L
Altcode:
The Sun's variability is controlled by the progression and interaction
of the magnetized systems that form the 22-year magnetic activity cycle
(the "Hale Cycle") as they march from their origin at ∼55° latitude
to the equator, over ∼19 years. We will discuss the end point of that
progression, dubbed "terminator" events, and our means of diagnosing
them. In this paper we expand on the Extended Solar Cycle framework to
construct a new solar activity "clock" which maps all solar magnetic
activity onto a single normalized epoch based on the terminations
of Hale Magnetic Cycles. Defining phase 0*2π on this clock as the
Terminators, then solar polar field reversals occur at ∼ 0.2*2π,
and the geomagnetically quiet intervals centered around solar minimum
start at ∼ 0.6*2π and end at the terminator, thus lasting 40% of the
cycle length. At this onset of quiescence, dubbed a "pre-terminator,"
the Sun shows a radical reduction in active region complexity and,
like the terminator events, is associated with the time when the solar
radio flux crosses F10.7 = 90 sfu. We use the terminator-based clock
to illustrate a range of phenomena that further emphasize the strong
interaction of the global-scale magnetic systems of the Hale Cycle: the
vast majority, 96%, of all X-flares happen between the Terminator and
pre-Terminator. In addition to the X-rays from violent flares, rapid
changes in the number of energetic photons—EUV spectral emission
from a hot corona and the F10.7 solar radio flux—impinging on the
atmosphere are predictable from the Terminator-normalized unit cycle,
which has implications for improving the fidelity of atmospheric
modelling.
Title: Tracking Movement of Long-lived Equatorial Coronal Holes from
Analysis of Long-term McIntosh Archive Data
Authors: Harris, Jacob; Dikpati, Mausumi; Hewins, Ian M.; Gibson,
Sarah E.; McIntosh, Scott W.; Chatterjee, Subhamoy; Kuchar, Thomas A.
Bibcode: 2022ApJ...931...54H
Altcode:
Features at the Sun's surface and atmosphere are constantly changing
due to its magnetic field. The McIntosh Archive provides a long-term
(45 yr) record of these features, digitized from hand-drawn synoptic
maps by Patrick McIntosh. Utilizing this data, we create stack plots
for coronal holes, i.e., Hovmöller-type plots of latitude bands,
for all longitudes, stacked in time, allowing tracking of coronal
hole movement. Using a newly developed two-step method of centroid
calculation, which includes a Fourier descriptor to represent a coronal
hole's boundary and calculate the centroid by the use of Green's
theorem, we calculate the centroids of 31 unique, long-lived equatorial
coronal holes for successive Carrington rotations during the entire
solar cycle 23, and estimate their slopes (time versus longitude)
as the coronal holes evolve. We compute coronal hole centroid drift
speeds from these slopes, and find an eastward (prograde) pattern
that is actually retrograde with respect to the local differential
rotation. By discussing the plausible physical mechanisms which could
cause these long-lived equatorial coronal holes to drift retrograde, we
identify either classical or magnetically modified westward-propagating
solar Rossby waves, with a speed of a few tens to a few hundreds of
meters per second, to be the best candidate for governing the drift of
deep-rooted, long-lived equatorial coronal holes. To explore plausible
physics of why long-lived equatorial coronal holes appear few in number
during solar minimum/early rising phase more statistics are required,
which will be studied in future.
Title: Probing the Physics of the Solar Atmosphere with the Multi-slit
Solar Explorer (MUSE). I. Coronal Heating
Authors: De Pontieu, Bart; Testa, Paola; Martínez-Sykora, Juan;
Antolin, Patrick; Karampelas, Konstantinos; Hansteen, Viggo; Rempel,
Matthias; Cheung, Mark C. M.; Reale, Fabio; Danilovic, Sanja; Pagano,
Paolo; Polito, Vanessa; De Moortel, Ineke; Nóbrega-Siverio, Daniel;
Van Doorsselaere, Tom; Petralia, Antonino; Asgari-Targhi, Mahboubeh;
Boerner, Paul; Carlsson, Mats; Chintzoglou, Georgios; Daw, Adrian;
DeLuca, Edward; Golub, Leon; Matsumoto, Takuma; Ugarte-Urra, Ignacio;
McIntosh, Scott W.; the MUSE Team
Bibcode: 2022ApJ...926...52D
Altcode: 2021arXiv210615584D
The Multi-slit Solar Explorer (MUSE) is a proposed mission composed of
a multislit extreme ultraviolet (EUV) spectrograph (in three spectral
bands around 171 Å, 284 Å, and 108 Å) and an EUV context imager (in
two passbands around 195 Å and 304 Å). MUSE will provide unprecedented
spectral and imaging diagnostics of the solar corona at high spatial
(≤0.″5) and temporal resolution (down to ~0.5 s for sit-and-stare
observations), thanks to its innovative multislit design. By obtaining
spectra in four bright EUV lines (Fe IX 171 Å, Fe XV 284 Å, Fe XIX-Fe
XXI 108 Å) covering a wide range of transition regions and coronal
temperatures along 37 slits simultaneously, MUSE will, for the first
time, "freeze" (at a cadence as short as 10 s) with a spectroscopic
raster the evolution of the dynamic coronal plasma over a wide range of
scales: from the spatial scales on which energy is released (≤0.″5)
to the large-scale (~170″ × 170″) atmospheric response. We use
numerical modeling to showcase how MUSE will constrain the properties of
the solar atmosphere on spatiotemporal scales (≤0.″5, ≤20 s) and
the large field of view on which state-of-the-art models of the physical
processes that drive coronal heating, flares, and coronal mass ejections
(CMEs) make distinguishing and testable predictions. We describe the
synergy between MUSE, the single-slit, high-resolution Solar-C EUVST
spectrograph, and ground-based observatories (DKIST and others), and
the critical role MUSE plays because of the multiscale nature of the
physical processes involved. In this first paper, we focus on coronal
heating mechanisms. An accompanying paper focuses on flares and CMEs.
Title: Magnetoseismology for the solar corona: from 10 Gauss to
coronal magnetograms
Authors: Yang, Zihao; Bethge, Christian; Tian, Hui; Tomczyk, Steven;
Morton, Richard; Del Zanna, Giulio; McIntosh, Scott; Karak, Bidya
Binay; Gibson, Sarah; Samanta, Tanmoy; He, Jiansen; Chen, Yajie; Bai,
Xianyong; Wang, Linghua
Bibcode: 2021AGUFMSH12C..07Y
Altcode:
Magnetoseismology, a technique of magnetic field diagnostics based
on observations of magnetohydrodynamic (MHD) waves, has been widely
used to estimate the field strengths of oscillating structures in
the solar corona. However, previously magnetoseismology was mostly
applied to occasionally occurring oscillation events, providing
an estimate of only the average field strength or one-dimensional
distribution of field strength along an oscillating structure. This
restriction could be eliminated if we apply magnetoseismology to the
pervasive propagating transverse MHD waves discovered with the Coronal
Multi-channel Polarimeter (CoMP). Using several CoMP observations of
the Fe XIII 1074.7 nm and 1079.8 nm spectral lines, we obtained maps of
the plasma density and wave phase speed in the corona, which allow us
to map both the strength and direction of the coronal magnetic field
in the plane of sky. We also examined distributions of the electron
density and magnetic field strength, and compared their variations
with height in the quiet Sun and active regions. Such measurements
could provide critical information to advance our understanding of the
Sun's magnetism and the magnetic coupling of the whole solar atmosphere.
Title: Origin of Rossby waves observed near the solar surface
Authors: Gilman, Peter; Dikpati, Mausumi; Guerrero, Gustavo;
Kosovichev, Alexander; McIntosh, Scott; Sreenivasan, Katepalli;
Warnecke, Joern; Zaqarashvili, Teimuraz
Bibcode: 2021AGUFMSH53C..04G
Altcode:
Differential rotation and toroidal magnetic bands in the tachocline
are unstable to MHD Rossby waves and may be responsible for patterns
of solar activity seen in the photosphere. Helioseismic and surface
velocity measurements reveal energetically neutral Rossby waves in the
supergranulation layer. To explore plausible sources of energy for
these Rossby waves, we study nonlinear dynamics of horizontal flows
in the supergranular layer in thepresence of rotation and differential
rotation. With a shallow-water model we show that kinetic energy, put
into smallest resolved spatial scales, very quickly 'reverse cascades'
to largest scales, exciting energetically neutral Rossby-Haurwitz type
waves, as well as energetically active ones with low longitudinal
spectral modes, depending on differential rotation. Horizontal
velocities in supergranules are known to be much larger than their
vertical motions; our shallow-water system includes a similar ratio. If
supergranules are responsible for Rossby waves seen in photosphere, it
paradoxically follows that (i) stable stratification of a thin rotating
spherical shell may be a sufficient but not a necessary condition for
Rossby waves, and (ii) small-scale convection producing global Rossby
waves in a thin differentially rotating fluid may be the first ever
example found in a celestial body.
Title: Interactions Among Magnetic Bands in Extended Solar Cycles
Authors: Belucz, Bernadett; Dikpati, Mausumi; McIntosh, Scott; Erdelyi,
Robertus; Leamon, Robert
Bibcode: 2021AGUFMSH55D1875B
Altcode:
The extended solar cycle, observationally revealed from the evolutions
of ephemeral regions, X-ray and EUV brightpoints, plages, filaments and
faculae, indicates the existence of oppositely-directed double magnetic
bands at the bottom dynamo-layer in each hemisphere. The band-pairs
in the North and South hemispheres migrate towards the equator and
plausibly evolve in amplitude as the cycle progresses. By studying
the MHD interactions of these band-pairs among themselves in each
hemisphere, as well as with their opposite-hemisphere's counterparts,
we show that the cross-equatorial interactions between the low-latitude
bands (which are essentially the active cycle's bands) in the North and
South effectively start when the band-separation across the equator is
less than 30 degrees (the bands are at 15-degree latitude or lower in
the North and South). Analyzing the properties of this interaction we
show how certain changes in the energy extractions by various stresses
from the magnetic fields can lead to the start of the declining phase
of the solar cycle.
Title: Spatio-temporal Drifts of Long-lived Equatorial Coronal Holes:
Do they follow the Local Differential Rotation or Rossby Waves?
Authors: Harris, Jacob; Hewins, Ian; Dikpati, Mausumi; Gibson, Sarah;
McIntosh, Scott; Chatterjee, Subhamoy; Kuchar, Thomas
Bibcode: 2021AGUFMSH54A..09H
Altcode:
By developing a novel centroid-calculation technique, we analyze
long-term McIntosh Archive data to compute the centroids of long-lived
coronal holes (CH) in the latitude bands of +10 to -10. The technique
involves a two-step algorithm for computing the CH-centroids: (i)
Fast Fourier Transform to determine the surface area that represents
a coronal hole in a specified latitude-band; (ii) Green's theorem
to convert the surface integral to a line-integral along the hole
boundary. After building a Hovmoller-type (longitude-time) diagram
for these CH-centroids, we estimate their latitude-longitude drift
patterns with time. We find that their spatio-temporal drift is
not determined: by the local differential rotation; instead a large
retrograde longitudinal speed of 100-150 m/s overpowers the local
differential rotation speed, causing the resultant drift-speed of these
CH-centroids in longitude with time. We reason that Rossby waves are
the most plausible candidates to cause the retrograde drift patterns
of these deep-rooted, long-lived equatorial coronal holes.
Title: Deciphering Solar Magnetic Activity: 140 Years of the `Extended
Solar Cycle' - Mapping the Hale Cycle
Authors: McIntosh, Scott W.; Leamon, Robert J.; Egeland, Ricky;
Dikpati, Mausumi; Altrock, Richard C.; Banerjee, Dipankar; Chatterjee,
Subhamoy; Srivastava, Abhishek K.; Velli, Marco
Bibcode: 2021SoPh..296..189M
Altcode: 2020arXiv201006048M
We investigate the occurrence of the "extended solar cycle" (ESC) as it
occurs in a host of observational data spanning 140 years. Investigating
coronal, chromospheric, photospheric, and interior diagnostics, we
develop a consistent picture of solar activity migration linked to the
22-year Hale (magnetic) cycle using superposed epoch analysis (SEA)
and previously identified Hale cycle termination events as the key
time for the SEA. Our analysis shows that the ESC and Hale cycle,
as highlighted by the terminator-keyed SEA, is strongly recurrent
throughout the entire observational record studied, some 140
years. Applying the same SEA method to the sunspot record confirms
that Maunder's butterfly pattern is a subset of the underlying Hale
cycle, strongly suggesting that the production of sunspots is not
the fundamental feature of the Hale cycle, but the ESC is. The ESC
(and Hale cycle) pattern highlights the importance of 55∘
latitude in the evolution, and possible production, of solar magnetism.
Title: Observational evidence of spot-producing magnetic ring's
split during MHD evolution
Authors: Norton, Aimee; Dikpati, Mausumi; McIntosh, Scott; Gilman,
Peter
Bibcode: 2021AGUFMSH55D1876N
Altcode:
Spot-producing toroidal rings of 6-degree latitudinal width, with peak
field of 15 kG, have been found to undergo dynamical splitting due
to nonlinear MHD. Split-time depends on the latitude-location of the
ring. Ring-splitting occurs fastest, within a few weeks, at latitudes
20-25 degrees. Rossby waves work as perturbations to drive instability
of spot-producing toroidal rings. The ring-split is caused by the `mixed
stress' or cross correlations of perturbation velocities and magnetic
fields, which arise due to the interaction of Rossby Waves. Mixed
stress carries magnetic energy and flux from the ring-peak to its
shoulders, eventually leading to the ring-split. The two split-rings
migrate away from each other, the high latitude counterpart slipping
poleward faster, due to migrating mixed stress and magnetic curvature
stress. Broader toroidal bands do not split. Much stronger rings of 35
kG, despite being narrow, don't split, due to rigidity from stronger
magnetic fields within the ring. The analysis of magnetograms from MDI
during solar cycle 23 indicates emergence of active regions sometimes
at the same longitudes but separated in latitude by 20-degrees or more,
which could be evidence of active regions emerging from split-rings,
which consistently contribute to occasional high latitude excursions of
observed butterfly wings during ascending, peak and descending phases of
a solar cycle. In the future, observational studies using much longer
term magnetograms including GONG and SDO/HMI can determine how often
new spots are found at higher latitudes than their lower latitude
counterparts, and how the combinations influence solar eruptions and
space weather events.
Title: Prediction of the first and last X-Flares of Cycle 25 Active
Regions
Authors: Leamon, Robert; McIntosh, Scott
Bibcode: 2021AGUFMSH55D1881L
Altcode:
The Suns variability is controlled by the progression and interaction
of the magnetized systems that form the 22-year magnetic activity cycle
(the "Hale Cycle") as they march from their origin at ~55 latitude to
the equator, over ~19 years. Recently, we introduced the concept of
"Terminators," the endpoints of those activity bands' progress, and a
new, and more insightful, way of looking at timing solar cycles than
counting spots [McIntosh et al. 2019; Leamon et al. 2020]. Rather
than the canonical minimum number of sunspots (which is arbitrary,
and depends on sum of four decreasing and increasing quantities --
the number of new and old cycle polarity spots in each hemisphere),
consider a precise date -- when there is no more old cycle polarity flux
left on the disk. Expressed in this way, a Terminator is the end of
a Hale Magnetic Cycle. Based on these Terminators, we construct a new
solar cycle phase clock which maps all solar magnetic activity onto a
single normalized epoch. If the Terminators appear at phase 0 * 2, then
solar polar field reversals occur at ~0.2 * 2, and the geomagnetically
quiet intervals centered around solar minimum, which start at 0.6 * 2
and end at the Terminator are thus 40% of the normalized cycle. These
"pre-Terminators" show a radical reduction of complexity of active
regions and (like the Terminators) are well approximated by the time
when the solar radio flux, F10.7 = 90 sfu. We demonstrate that the
vast majority, 96%, of all X-flares happen between the Terminator and
pre-Terminator; the July 2021 event appears to fall just outside this
window, but it is highly possible, if not probable that the Cycle 24
Terminator occurs between the date of abstract submission and the Fall
Meeting itself. Further, sunspot max amplitude, the aa geomagnetic
index, and F10.7 and spectral irradiance are all predictable from a
normalized unit cycle from Terminator to Terminator.
Title: Dynamical Splitting of Spot-producing Magnetic Rings in a
Nonlinear Shallow-water Model
Authors: Dikpati, Mausumi; Norton, Aimee A.; McIntosh, Scott W.;
Gilman, Peter A.
Bibcode: 2021ApJ...922...46D
Altcode:
We explore the fundamental physics of narrow toroidal rings during their
nonlinear magnetohydrodynamic evolution at tachocline depths. Using
a shallow-water model, we simulate the nonlinear evolution of
spot-producing toroidal rings of 6° latitudinal width and a peak field
of 15 kG. We find that the rings split; the split time depends on the
latitude of each ring. Ring splitting occurs fastest, within a few
weeks, at latitudes 20°-25°. Rossby waves work as perturbations to
drive the instability of spot-producing toroidal rings; the ring split
is caused by the "mixed stress" or cross-correlations of perturbation
velocities and magnetic fields, which carry magnetic energy and flux
from the ring peak to its shoulders, leading to the ring split. The two
split rings migrate away from each other, the high-latitude counterpart
slipping poleward faster due to migrating mixed stress and magnetic
curvature stress. Broader toroidal bands do not split. Much stronger
rings, despite being narrow, do not split due to rigidity from stronger
magnetic fields within the ring. Magnetogram analysis indicates the
emergence of active regions sometimes at the same longitudes but
separated in latitude by 20° or more, which could be evidence of
active regions emerging from split rings, which consistently contribute
to observed high-latitude excursions of butterfly wings during the
ascending, peak, and descending phases of a solar cycle. Observational
studies in the future can determine how often new spots are found at
higher latitudes than their lower-latitude counterparts and how the
combinations influence solar eruptions and space weather events.
Title: Response to "Limitations in the Hilbert Transform Approach
to Locating Solar Cycle Terminators" by R. Booth
Authors: Leamon, Robert J.; McIntosh, Scott W.; Chapman, Sandra C.;
Watkins, Nicholas W.
Bibcode: 2021SoPh..296..151L
Altcode:
Booth (Solar Phys.296, 108, 2021; hereafter B21) is essentially
a critique of the Hilbert transform techniques used in our paper
(Leamon et al., Solar Phys.295, 36, 2020; hereafter L20) to predict
the termination of solar cycles. Here we respond to his arguments;
our methodology and parameter choices do extract a mathematically
robust signature of terminators from the historical sunspot record. We
agree that the attempt in L20 to extrapolate beyond the sunspot record
gives a failed prediction for the next terminator of May 2020, and we
identify both a possible cause and remedy here. However, we disagree
with the B21 assessment that the likely termination of Solar Cycle 24
is two years after the date predicted in L20, and we show why.
Title: The Sun's Magnetic (Hale) Cycle and 27 Day Recurrences in
the aa Geomagnetic Index
Authors: Chapman, S. C.; McIntosh, S. W.; Leamon, R. J.; Watkins, N. W.
Bibcode: 2021ApJ...917...54C
Altcode: 2021arXiv210102569C
We construct a new solar cycle phase clock which maps each of the last
18 solar cycles onto a single normalized epoch for the approximately 22
yr Hale (magnetic polarity) cycle, using the Hilbert transform of daily
sunspot numbers (SSNs) since 1818. The occurrences of solar maxima show
almost no discernible Hale cycle dependence, consistent with the clock
being synchronized to polarity reversals. We reengineer the Sargent
R27 index and combine it with our epoch analysis to obtain a high time
resolution parameter for 27 day recurrence in aa, ⟨acv(27)⟩. This
reveals that the transition to recurrence, that is, to an ordered
solar wind dominated by high-speed streams, is fast, with an upper
bound of a few solar rotations. It resolves an extended late declining
phase which is approximately twice as long on even Schwabe cycles as
odd. Galactic cosmic ray flux rises in step with ⟨acv(27)⟩ but then
stays high. Our analysis also identifies a slow-timescale trend in
SSN that simply tracks the Gleissberg cycle. We find that this trend
is in phase with the slow-timescale trend in the modulus of sunspot
latitudes, and in antiphase with that of the R27 index.
Title: Reconciling various solar Rossby wave observations using global
(M)HD models
Authors: Dikpati, M.; Gilman, P. A.; McIntosh, S. W.; Zaqarashvili,
T. V.
Bibcode: 2021AAS...23811319D
Altcode:
Various observational analyses indicate that the Sun has Rossby
waves, which include hydrodynamic Rossby waves like that on the
Earth's atmosphere as well as magnetohydrodynamic ones, which do
not have their counterparts on the Earth. Many of us are showing,
from observations and model-calculations, that solar hydrodynamic
Rossby waves have retrograde speed and they follow Rossby-Haurwitz
type dispersion relation. However, it has also recently been shown
MHD Rossby waves can have both retrograde as well as prograde speed;
if MHD Rossby waves are retrograde they are more retrograde than their
HD counterparts, whereas if they are prograde, they are relatively
slow. Helioseismically determined Rossby waves detected so far are HD
waves that are energetically neutral. Coronal bright points as well as
long-lived coronal holes' longitudinal drift-patterns with time show
evidence of HD as well as MHD Rossby waves. We know from nonlinear
simulations of global MHD waves and instabilities that Rossby waves can
be energetically active and hence, can nonlinearly interact with the
solar differential rotation and spot-producing toroidal magnetic fields,
very much like nonlinear Orr mechanism in fluid dynamics. Is it possible
to reconcile the various solar Rossby waves observations? Certainly
different observational techniques applied to different elevations
on the Sun may be measuring different Rossby waves. Furthermore,
the different measurements may be detecting waves that originate at
different depths inside the Sun. Solar atmosphere magnetic features may
have roots deep in the convection zone and reflect MHD Rossby waves at
those depths. We will present model-simulations to show what physical
conditions are responsible for producing sectoral modes and what are
responsible for generating energetically active Rossby waves, which
have important implications in causing short-term variability in solar
activity, and in turn, in space weather. This work is supported by the
NCAR, sponsored by the NSF under cooperative agreement 1852977. MD
acknowledges support from several NASA grants, namely the LWS award
80NSSC20K0355 to NCAR, subaward to NCAR from NASA's DRIVE Center award
80NSSC20K0602 (originally awarded to Stanford) and NASA-HSR subaward
80NSSC18K1206 (originally awarded to NSO).
Title: Hinode and IRIS Synoptic Observations of Solar Cycle Transition
at Mid-Latitudes
Authors: Egeland, R.; Centeno, R.; Lacatus, D.; de Toma, G.; Bryans,
P.; McIntosh, S.
Bibcode: 2021AAS...23811324E
Altcode:
Recent observations by McIntosh et al. using SDO/AIA coronal bright
point density and the magnetogram-derived large scale open magnetic
flux "g-nodes" have traced out extended solar cycle activity bands
that originate at ~55 degrees latitude and propagate toward the
equator. When the opposite hemisphere bands "terminate" at the equator,
this event corresponds with the rapid rise of new cycle flux and active
regions at mid-latitudes, ~35 degrees. We present weekly synoptic
high-resolution observations of mid-latitude (35-40 degrees) magnetic
flux and chromospheric emission from Hinode SOT/SP and IRIS starting
from March 2017 until today, covering the end of cycle 24 and the
beginnings of cycle 25. After carefully correcting for instrumental
shifts, noise, and solar B-angle effects, we analyze time series
of mean magnetic flux, chromospheric line intensity, and statistical
properties of magnetic regions for signals of a developing cycle 25 and
the passage of the activity bands in these typically quiet mid-latitude
regions. Initial results show that the statistical properties of our
activity metrics are roughly constant over the four year period, with
a step function increase in activity that corresponds to a change to a
lower observation latitude. Finally, we investigate the correspondence
of SDO/AIA coronal bright points in our observational field of view
to chromospheric emission and photospheric magnetic features.
Title: Simulating Properties of "Seasonal" Variability in Solar
Activity And Space Weather Impacts
Authors: Dikpati, Mausumi; McIntosh, Scott W.; Wing, Simon
Bibcode: 2021FrASS...8...71D
Altcode:
Solar short-term, quasi-annual variability within a decadal
sunspot-cycle has recently been observed to strongly correlate with
major class solar flares, resulting into quasi-periodic space weather
"seasons". In search for the origin of this quasi-periodic enhanced
activity bursts, significant researches are going on. In this article
we show, by employing a 3D thin-shell shallow-water type model, that
magnetically modified Rossby waves can interact with spot-producing
toroidal fields and create certain quasi-periodic spatio-temporal
patterns, which plausibly cause a season of enhanced solar activity
followed by a relatively quiet period. This is analogous to the Earth's
lower atmosphere, where Rossby waves and jet streams are produced and
drive global terrestrial weather. Shallow-water models have been applied
to study terrestrial Rossby waves, because their generation layer in
the Earth's lower atmospheric region has a much larger horizontal than
vertical scale, one of the model-requirements. In the Sun, though Rossby
waves can be generated at various locations, particularly favorable
locations are the subadiabatic layers at/near the base of the convection
zone where the horizontal scale of the fluid and disturbances in it
can be much larger than the vertical scale. However, one important
difference with respect to terrestrial waves is that solar Rossby waves
are magnetically modified due to presence of strong magnetic fields
in the Sun. We consider plausible magnetic field configurations at
the base of the convection zone during different phases of the cycle
and describe the properties of energetically active Rossby waves
generated in our model. We also discuss their influence in causing
short-term spatio-temporal variability in solar activity and how this
variability could have space weather impacts. An example of a possible
space weather impact on the Earth's radiation belts is presented.
Title: A New View of the Solar Interface Region from the Interface
Region Imaging Spectrograph (IRIS)
Authors: De Pontieu, Bart; Polito, Vanessa; Hansteen, Viggo; Testa,
Paola; Reeves, Katharine K.; Antolin, Patrick; Nóbrega-Siverio,
Daniel Elias; Kowalski, Adam F.; Martinez-Sykora, Juan; Carlsson,
Mats; McIntosh, Scott W.; Liu, Wei; Daw, Adrian; Kankelborg, Charles C.
Bibcode: 2021SoPh..296...84D
Altcode: 2021arXiv210316109D
The Interface Region Imaging Spectrograph (IRIS) has been obtaining
near- and far-ultraviolet images and spectra of the solar atmosphere
since July 2013. IRIS is the highest resolution observatory to provide
seamless coverage of spectra and images from the photosphere into the
low corona. The unique combination of near- and far-ultraviolet spectra
and images at sub-arcsecond resolution and high cadence allows the
tracing of mass and energy through the critical interface between the
surface and the corona or solar wind. IRIS has enabled research into the
fundamental physical processes thought to play a role in the low solar
atmosphere such as ion-neutral interactions, magnetic reconnection, the
generation, propagation, and dissipation of waves, the acceleration of
non-thermal particles, and various small-scale instabilities. IRIS has
provided insights into a wide range of phenomena including the discovery
of non-thermal particles in coronal nano-flares, the formation and
impact of spicules and other jets, resonant absorption and dissipation
of Alfvénic waves, energy release and jet-like dynamics associated
with braiding of magnetic-field lines, the role of turbulence and the
tearing-mode instability in reconnection, the contribution of waves,
turbulence, and non-thermal particles in the energy deposition during
flares and smaller-scale events such as UV bursts, and the role of flux
ropes and various other mechanisms in triggering and driving CMEs. IRIS
observations have also been used to elucidate the physical mechanisms
driving the solar irradiance that impacts Earth's upper atmosphere,
and the connections between solar and stellar physics. Advances in
numerical modeling, inversion codes, and machine-learning techniques
have played a key role. With the advent of exciting new instrumentation
both on the ground, e.g. the Daniel K. Inouye Solar Telescope (DKIST)
and the Atacama Large Millimeter/submillimeter Array (ALMA), and
space-based, e.g. the Parker Solar Probe and the Solar Orbiter, we aim
to review new insights based on IRIS observations or related modeling,
and highlight some of the outstanding challenges.
Title: Termination of Solar Cycles and Correlated Tropospheric
Variability
Authors: Leamon, Robert J.; McIntosh, Scott W.; Marsh, Daniel R.
Bibcode: 2021E&SS....801223L
Altcode:
The Sun provides the energy required to sustain life on Earth and drive
our planet's atmospheric circulation. However, establishing a solid
physical connection between solar and tropospheric variability has posed
a considerable challenge. The canon of solar variability is derived
from the 400 years of observations that demonstrates the waxing and
waning number of sunspots over an 11( ish) year period. Recent research
has demonstrated the significance of the underlying 22 years magnetic
polarity cycle in establishing the shorter sunspot cycle. Integral to
the manifestation of the latter is the spatiotemporal overlapping and
migration of oppositely polarized magnetic bands. We demonstrate the
impact of "terminators"—the end of Hale magnetic cycles—on the
Sun's radiative output and particulate shielding of our atmosphere
through the rapid global reconfiguration of solar magnetism. Using
direct observation and proxies of solar activity going back some
six decades we can, with high statistical significance, demonstrate
a correlation between the occurrence of terminators and the largest
swings of Earth's oceanic indices: the transition from El Niño to La
Niña states of the central Pacific. This empirical relationship is a
potential source of increased predictive skill for the understanding
of El Niño climate variations, a high stakes societal imperative given
that El Niño impacts lives, property, and economic activity around the
globe. A forecast of the Sun's global behavior places the next solar
cycle termination in mid 2020; should a major oceanic swing follow,
then the challenge becomes: when does correlation become causation
and how does the process work?
Title: Mapping the global magnetic field in the solar corona through
magnetoseismology
Authors: Yang, Zihao; Bethge, Christian; Tian, Hui; Tomczyk, Steven;
Morton, Richard; Del Zanna, Giulio; McIntosh, Scott; Karak, Bidya
Binay; Gibson, Sarah; Samanta, Tanmoy; He, Jiansen; Chen, Yajie;
Wang, Linghua; Bai, Xianyong
Bibcode: 2021EGUGA..23..642Y
Altcode:
Magnetoseismology, a technique of magnetic field diagnostics based
on observations of magnetohydrodynamic (MHD) waves, has been widely
used to estimate the field strengths of oscillating structures in
the solar corona. However, previously magnetoseismology was mostly
applied to occasionally occurring oscillation events, providing
an estimate of only the average field strength or one-dimensional
distribution of field strength along an oscillating structure. This
restriction could be eliminated if we apply magnetoseismology to the
pervasive propagating transverse MHD waves discovered with the Coronal
Multi-channel Polarimeter (CoMP). Using several CoMP observations of
the Fe XIII 1074.7 nm and 1079.8 nm spectral lines, we obtained maps of
the plasma density and wave phase speed in the corona, which allow us
to map both the strength and direction of the coronal magnetic field
in the plane of sky. We also examined distributions of the electron
density and magnetic field strength, and compared their variations
with height in the quiet Sun and active regions. Such measurements
could provide critical information to advance our understanding of the
Sun's magnetism and the magnetic coupling of the whole solar atmosphere.
Title: A clock for the Sun's magnetic Hale cycle and 27 day
recurrences in the aa geomagnetic index
Authors: Chapman, Sandra; McIntosh, Scott; Leamon, Robert; Watkins,
Nicholas
Bibcode: 2021EGUGA..23.2555C
Altcode:
We construct a new solar cycle phase clock which maps each of the last
18 solar cycles onto a single normalized epoch for the approximately
22 year Hale (magnetic polarity) cycle, using the Hilbert transform
of daily sunspot numbers (SSN) since 1818. We use the clock to study
solar and geomagnetic climatology as seen in datasets available
over multiple solar cycles. The occurrence of solar maxima on the
clock shows almost no Hale cycle dependence, confirming that the
clock is synchronized with polarity reversals. The odd cycle minima
lead the even cycle minima by ~ 1.1 normalized years, whereas the
odd cycle terminators (when sunspot bands from opposite hemispheres
have moved to the equator and coincide, thus terminating the cycle,
McIntosh(2019)) lag the even cycle terminators by ~ 2.3 normalized
years. The average interval between each minimum and terminator is
thus relatively extended for odd cycles and shortened for even ones. We
re-engineer the R27 index that was orignally proposed by Sargent(1985)
to parameterize 27 day recurrences in the aa index. We perform an epoch
analysis of autocovariance in the aa index using the Hale cycle clock
to obtain a high time resolution parameter for 27 day recurrence,
<acv(27)>. This reveals that the transition to recurrence,
that is, to an ordered solar wind dominated by high speed streams,
is fast, occurring within 2-3 solar rotations or less. It resolves an
extended late declining phase which is approximately twice as long on
even Schwabe cycles as odd ones. We find that Galactic Cosmic Ray flux
rises in step with <acv(27)> but then stays high. Our analysis
also identifies a slow timescale trend in SSN that simply tracks the
Gleissberg cycle. We find that this trend is in phase with the slow
timescale trend in the modulus of sunspot latitudes, and in antiphase
with that of the R27 index.
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
Bibcode: 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: Solar Wind Helium Abundance Heralds Solar Cycle Onset
Authors: Alterman, Benjamin L.; Kasper, Justin C.; Leamon, Robert J.;
McIntosh, Scott W.
Bibcode: 2021SoPh..296...67A
Altcode: 2020arXiv200604669A
We study the solar wind helium-to-hydrogen abundance's (AHe)
relationship to solar cycle onset. Using OMNI/Lo data, we show that
AHe increases prior to sunspot number (SSN) minima. We
also identify a rapid depletion and recovery in AHe that
occurs directly prior to cycle onset. This AHe shutoff
happens at approximately the same time across solar wind speeds
(vsw) and the time between successive AHe shutoffs
is typically on the order of the corresponding solar cycle length. In
contrast to AHe's vsw-dependent phase lag with
respect to SSN (Alterman and Kasper, 2019), AHe shutofff's
concurrence across vsw likely implies it is independent of
solar wind acceleration and driven by a mechanism near or below the
photosphere. Using brightpoint (BP) measurements to provide context,
we infer that AHe shutoff is likely related to the overlap
of adjacent solar cycles and the equatorial flux cancelation of the
older, extended solar cycle during solar minima.
Title: Deciphering the Deep Origin of Active Regions via Analysis
of Magnetograms
Authors: Dikpati, Mausumi; McIntosh, Scott W.; Chatterjee, Subhamoy;
Norton, Aimee A.; Ambroz, Pavel; Gilman, Peter A.; Jain, Kiran;
Munoz-Jaramillo, Andres
Bibcode: 2021ApJ...910...91D
Altcode:
In this work, we derive magnetic toroids from surface magnetograms
by employing a novel optimization method, based on the trust region
reflective algorithm. The toroids obtained in this way are combinations
of Fourier modes (amplitudes and phases) with low longitudinal
wavenumbers. The optimization also estimates the latitudinal width of
the toroids. We validate the method using synthetic data, generated
as random numbers along a specified toroid. We compute the shapes and
latitudinal widths of the toroids via magnetograms, generally requiring
several m's to minimize residuals. A threshold field strength is
chosen to include all active regions in the magnetograms for toroid
derivation, while avoiding non-contributing weaker fields. Higher
thresholds yield narrower toroids, with an m = 1 dominant pattern. We
determine the spatiotemporal evolution of toroids by optimally weighting
the amplitudes and phases of each Fourier mode for a sequence of five
Carrington Rotations (CRs) to achieve the best amplitude and phases for
the middle CR in the sequence. Taking more than five causes "smearing"
or degradation of the toroid structure. While this method applies no
matter the depth at which the toroids actually reside inside the Sun,
by comparing their global shape and width with analogous patterns
derived from magnetohydrodynamic (MHD) tachocline shallow water model
simulations, we infer that their origin is at/near the convection zone
base. By analyzing the "Halloween" storms as an example, we describe
features of toroids that may have caused the series of space weather
events in 2003 October-November. Calculations of toroids for several
sunspot cycles will enable us to find similarities/differences in
toroids for different major space weather events.
Title: Rossby Waves in Astrophysics
Authors: Zaqarashvili, T. V.; Albekioni, M.; Ballester, J. L.;
Bekki, Y.; Biancofiore, L.; Birch, A. C.; Dikpati, M.; Gizon, L.;
Gurgenashvili, E.; Heifetz, E.; Lanza, A. F.; McIntosh, S. W.; Ofman,
L.; Oliver, R.; Proxauf, B.; Umurhan, O. M.; Yellin-Bergovoy, R.
Bibcode: 2021SSRv..217...15Z
Altcode:
Rossby waves are a pervasive feature of the large-scale motions of the
Earth's atmosphere and oceans. These waves (also known as planetary
waves and r-modes) also play an important role in the large-scale
dynamics of different astrophysical objects such as the solar
atmosphere and interior, astrophysical discs, rapidly rotating stars,
planetary and exoplanetary atmospheres. This paper provides a review
of theoretical and observational aspects of Rossby waves on different
spatial and temporal scales in various astrophysical settings. The
physical role played by Rossby-type waves and associated instabilities
is discussed in the context of solar and stellar magnetic activity,
angular momentum transport in astrophysical discs, planet formation,
and other astrophysical processes. Possible directions of future
research in theoretical and observational aspects of astrophysical
Rossby waves are outlined.
Title: Derivation of Toroid Patterns from Analysis of Magnetograms
And Inferring Their Deep-origin
Authors: Chatterjee, S.; Dikpati, M.; McIntosh, S. W.; Norton, A. A.;
Ambroz, P.; Gilman, P.; Jain, K.; Munoz-Jaramillo, A.
Bibcode: 2020AGUFMSH0020013C
Altcode:
We employ a novel optimization method based on Trust Region Reflective
algorithm to derive magnetic toroids from surface magnetograms. Toroids
obtained are combinations of Fourier modes (amplitudes and phases)
with low longitudinal wavenumbers. After validating the method using
synthetic data generated as random numbers along a specified toroid,
we compute shapes and latitudinal-widths of toroids from magnetograms,
usually requiring several m 's to minimize residuals. By comparing
properties of these toroids with patterns produced in the bottom
toroidal band undergoing MHD evolution in a 3D thin-shell shallow-water
type model, we infer their deep origin at/near convention-zone's base
or tachocline. A threshold field-strength is chosen to include all
active regions in magnetograms for toroid derivation, while avoiding
non-contributing weaker fields. Higher thresholds yield narrower
toroids, with m = 1 dominant, implying that stronger active regions
are erupting from the core of the toroids at bottom. We determine the
spatio-temporal evolution of toroids by optimally weighting amplitudes
and phases of each Fourier mode for a sequence of 5 Carrington Rotations
(CRs) to get the best amplitude and phases for the middle CR in the
sequence. Taking more than 5 causes 'smearing' or degradation of toroid
structure. As an example case, we analyze 'Halloween' storms toroids,
and describe the features that might have caused the series of space
weather events in October-November of 2003. We compare features of
these toroids with analogous patterns derived from model-output. To find
similarities/differences in toroids for different major space weather
events, we will analyze long-term magnetograms for several solar cycles.
Title: The Hale Cycle Clock
Authors: Leamon, R. J.; McIntosh, S. W.; Chapman, S. C.; Watkins, N. W.
Bibcode: 2020AGUFMSH053..02L
Altcode:
The Sun's variability is controlled by the progression and interaction
of the magnetized systems that form the 22-year magnetic activity cycle
(the ``Hale Cycle'') as they march from their origin at ∼55 degrees
latitude to the equator, over some 19 years. We will discuss the end
point of that progression, dubbed ``terminator'' events [McIntosh et
al. 2019], and our means of diagnosing them [McIntosh et al. 2019,
Leamon et al., 2020]. Based on these terminations of Hale Magnetic
Cycles, we construct a new solar cycle phase clock which maps all
solar magnetic activity onto a single normalized epoch [Chapman et al,
2020]. If the Terminators appear at phase 0 * 2π , then solar polar
field reversals occur at ∼{}0.2 * 2π , and the geomagnetically
quiet intervals centered around solar minimum, which start at 0.6 * 2π
and end at the terminator are thus 40% of the normalized cycle. These
``pre-terminators'' show a radical reduction of complexity of active
regions and (like the terminators) are well approximated by the time
when the solar radio flux, F10.7=90 sfu. There is thus immediate
applicability for the Hale Cycle Clock to predict when the first and
last X-flares and other severe Space Weather events of Cycle 25 will be
(with the first possibly already happening before the meeting), and
we further will discuss the applicability for confirming the length
of Cycle 25 as early as its polar field reversal near maximum. McIntosh et al., "What the Sudden Death of Solar Cycles Can Tell Us
About the Nature of the Solar Interior," Solar Physics 294, 88 (2020)
Leamon et al., "Timing Terminators: Forecasting Sunspot Cycle 25
Onset," Solar Physics 295, 36 (2020)
Title: Does the Sun have a polar vortex?
Authors: McIntosh, S. W.; Dikpati, M.
Bibcode: 2020AGUFMSH014..07M
Altcode:
No abstract at ADS
Title: Investigating the Chromospheric Footpoints of the Solar Wind
Authors: Bryans, Paul; McIntosh, Scott W.; Brooks, David H.; De
Pontieu, Bart
Bibcode: 2020ApJ...905L..33B
Altcode:
Coronal holes present the source of the fast solar wind. However,
the fast solar wind is not unimodal—there are discrete, but subtle,
compositional, velocity, and density structures that differentiate
different coronal holes as well as wind streams that originate within
one coronal hole. In this Letter we exploit full-disk observational
"mosaics" performed by the Interface Region Imaging Spectrograph
(IRIS) spacecraft to demonstrate that significant spectral variation
exists within the chromospheric plasma of coronal holes. The spectral
differences outline the boundaries of some—but not all—coronal
holes. In particular, we show that the "peak separation" of the Mg
II h line at 2803 Å illustrates changes in what appear to be open
magnetic features within a coronal hole. These observations point
to a chromospheric source for the inhomogeneities found in the fast
solar wind. These chromospheric signatures can provide additional
constraints on magnetic field extrapolations close to the source,
potentially on spatial scales smaller than from traditional coronal hole
detection methods based on intensity thresholding in the corona. This
is of increased importance with the advent of Parker Solar Probe and
Solar Orbiter and the ability to accurately establish the connectivity
between their in situ measurements and remote sensing observations of
the solar atmosphere.
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.
Bibcode: 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. 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. The 7,000
m2 sail used in the mission assessment is a direct extension
of the 4-quadrant 1,666 m2 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: Overlapping Magnetic Activity Cycles and the Sunspot Number:
Forecasting Sunspot Cycle 25 Amplitude
Authors: McIntosh, Scott W.; Chapman, Sandra; Leamon, Robert J.;
Egeland, Ricky; Watkins, Nicholas W.
Bibcode: 2020SoPh..295..163M
Altcode: 2020arXiv200615263M
The Sun exhibits a well-observed modulation in the number of spots
on its disk over a period of about 11 years. From the dawn of modern
observational astronomy, sunspots have presented a challenge to
understanding—their quasi-periodic variation in number, first
noted 175 years ago, has stimulated community-wide interest to this
day. A large number of techniques are able to explain the temporal
landmarks, (geometric) shape, and amplitude of sunspot "cycles,"
however, forecasting these features accurately in advance remains
elusive. Recent observationally-motivated studies have illustrated a
relationship between the Sun's 22-year (Hale) magnetic cycle and the
production of the sunspot cycle landmarks and patterns, but not the
amplitude of the sunspot cycle. Using (discrete) Hilbert transforms on
more than 270 years of (monthly) sunspot numbers we robustly identify
the so-called "termination" events that mark the end of the previous
11-yr sunspot cycle, the enhancement/acceleration of the present cycle,
and the end of 22-yr magnetic activity cycles. Using these we extract
a relationship between the temporal spacing of terminators and the
magnitude of sunspot cycles. Given this relationship and our prediction
of a terminator event in 2020, we deduce that sunspot Solar Cycle 25
could have a magnitude that rivals the top few since records began. This
outcome would be in stark contrast to the community consensus estimate
of sunspot Solar Cycle 25 magnitude.
Title: Solar Wind Helium Abundance Heralds the Onset of Solar Cycle 25
Authors: Alterman, B. L.; Kasper, J. C.; Leamon, R. J.; McIntosh, S. W.
Bibcode: 2020AGUFMSH053..01A
Altcode:
We study the solar wind helium-to-hydrogen abundance's (Ahe)
relationship to solar cycle onset. We identify a rapid depletion
and recovery in Ahe immediately prior to sunspot number
(SSN) minima. This depletion happens at approximately the same time
across solar wind speeds, implying that it is formed by a mechanism
distinct from the one that drives Ahe's solar cycle scale
variation and speed-dependent phase offset with respect to SSN. As
Ahe's rapid depletion and recovery have already occurred
and Ahe is now increasing as it has following previous
solar minima, we infer that solar cycle 25 has already begun.
Title: MHD of double-bands representing extended solar cycle
Authors: Belucz, B.; Dikpati, M.; McIntosh, S. W.; Erdelyi, R.
Bibcode: 2020AGUFMSH0020020B
Altcode:
Along with the "butterfly diagram" of sunspots, combined observational
studies of ephemeral active regions, X-ray and EUV brightpoints, plage,
filaments, facule and prominences demonstrate a pattern, which is known
as the Extended Solar Cycle (ESC). This pattern indicates the wings of
the sunspot butterfly could be extended to much higher latitudes (about
60 degrees) and to earlier time than the start of a sunspot cycle,
hence creating a strong overlap between cycles, meaning that, during the
ongoing cycle's activity near 30-degrees latitude in each hemisphere,
the next cycle is starting at around 60-degrees. By representing these
epochs by oppositely-directed double magnetic bands in each hemisphere,
we compute the eigen modes for MHD Rossby waves at the base of the
convection zone and study how the properties of unstable MHD Rossby
waves change as these band-pairs migrate equatorward. We find that
the low-latitude band itself drives the major dynamics as the solar
activity progresses from 35 to 20 degrees. When the activity proceeds
further equatorward of 20 degrees, the next cycle's band from higher
latitudes starts taking over to drive the majority of the activity
features by interacting with the low-latitude band.
Title: Prediction of the In Situ Coronal Mass Ejection Rate for Solar
Cycle 25: Implications for Parker Solar Probe In Situ Observations
Authors: Moestl, C.; Weiss, A.; Reiss, M.; Bailey, R.; Amerstorfer,
U.; Amerstorfer, T.; Hinterreiter, J.; Bauer, M.; McIntosh, S. W.;
Lugaz, N.; Stansby, D.
Bibcode: 2020AGUFMSH0490001M
Altcode:
The Parker Solar Probe (PSP) and Solar Orbiter missions are designed to
make groundbreaking observations of the Sun and interplanetary space
within this decade. We show that a particularly interesting possible
in situ observation of an interplanetary coronal mass ejection (ICME)
by PSP may arise when PSP shortly resides at distances < 0.1~AU to
the Sun. During these close encounters, the same ICME flux rope could
be observed in situ by PSP twice, by impacting its frontal part as
well as its leg. Investigating the odds of this situation, we forecast
the yearly and monthly rate of ICME observations in solar cycle 25 (up
to the year 2032) based on 2 models for the sunspot number (SSN): (1)
the consensus prediction of an expert panel in 2019 (maximum SSN=115),
and (2) a prediction by McIntosh et al. (2020, maximum SSN = 232). We
link the SSN to the observed ICME rates in solar cycles 23 and 24 with
the Richardson and Cane list and our own ICME catalog with a linear
fit. This allows us to include several sources of uncertainties,
and the average ICME rate results in 3 to 5 events per month at
any in situ location near the solar equatorial plane during solar
maximum in 2025. Based on these results, we calculate the number of
ICMEs to be observed by PSP at distances < 0.1 AU as between 2
and 7 until the nominal end of the mission in 2025, including 1~σ
uncertainties, making a double encounter of an ICME flux rope by PSP
indeed possible. We model the potential flux rope signatures of such
a double crossing with the semi-empirical 3DCORE flux rope model,
showing a telltale elevation of the radial magnetic field component
BR, a sign reversal in the component BN normal to
the solar equator, and an otherwise almost constant field during the
second encounter, which is in contrast to the classic field rotation
in the first encounter. This holds considerable promise to determine
the structure of CMEs close to their origin in the solar corona.
Title: Deciphering Solar Magnetic Activity. The Solar Cycle Clock
Authors: Leamon, Robert; McIntosh, Scott; Title, Alan
Bibcode: 2020arXiv201215186L
Altcode:
The Sun's variability is controlled by the progression and interaction
of the magnetized systems that form the 22-year magnetic activity cycle
(the "Hale Cycle'') as they march from their origin at $\sim$55 degrees
latitude to the equator, over $\sim$19 years. We will discuss the end
point of that progression, dubbed "terminator'' events, and our means
of diagnosing them. Based on the terminations of Hale Magnetic Cycles,
we construct a new solar activity 'clock' which maps all solar magnetic
activity onto a single normalized epoch. The Terminators appear at
phase $0 * 2\pi$ on this clock (by definition), then solar polar
field reversals commence at $\sim0.2 * 2\pi$, and the geomagnetically
quiet intervals centered around solar minimum, start at $\sim0.6 *
2\pi$ and end at the terminator, lasting 40% of the normalized cycle
length. With this onset of quiescence, dubbed a "pre-terminator,''
the Sun shows a radical reduction in active region complexity and (like
the terminator events) is associated with the time when the solar radio
flux crosses F10.7=90 sfu -- effectively marking the commencement of
solar minimum conditions. In this paper we use the terminator-based
clock to illustrate a range of phenomena that further emphasize the
strong interaction of the global-scale magnetic systems of the Hale
Cycle. arXiv:2010.06048 is a companion article.
Title: Prediction of the In Situ Coronal Mass Ejection Rate for Solar
Cycle 25: Implications for Parker Solar Probe In Situ Observations
Authors: Möstl, Christian; Weiss, Andreas J.; Bailey, Rachel L.;
Reiss, Martin A.; Amerstorfer, Tanja; Hinterreiter, Jürgen; Bauer,
Maike; McIntosh, Scott W.; Lugaz, Noé; Stansby, David
Bibcode: 2020ApJ...903...92M
Altcode: 2020arXiv200714743M
The Parker Solar Probe (PSP) and Solar Orbiter missions are designed
to make groundbreaking observations of the Sun and interplanetary
space within this decade. We show that a particularly interesting in
situ observation of an interplanetary coronal mass ejection (ICME)
by PSP may arise during close solar flybys (<0.1 au). During these
times, the same magnetic flux rope inside an ICME could be observed
in situ by PSP twice, by impacting its frontal part as well as its
leg. Investigating the odds of this situation, we forecast the ICME
rate in solar cycle 25 based on two models for the sunspot number
(SSN): (1) the forecast of an expert panel in 2019 (maximum SSN =
115), and (2) a prediction by McIntosh et al. (2020, maximum SSN =
232). We link the SSN to the observed ICME rates in solar cycles 23
and 24 with the Richardson and Cane list and our own ICME catalog,
and calculate that between one and seven ICMEs will be observed by
PSP at heliocentric distances <0.1 au until 2025, including 1σ
uncertainties. We then model the potential flux rope signatures of such
a double-crossing event with the semiempirical 3DCORE flux rope model,
showing a telltale elevation of the radial magnetic field component
BR, and a sign reversal in the component BN
normal to the solar equator compared to field rotation in the first
encounter. This holds considerable promise to determine the structure
of CMEs close to their origin in the solar corona.
Title: The Evolution of Coronal Holes over Three Solar Cycles Using
the McIntosh Archive
Authors: Hewins, Ian M.; Gibson, Sarah E.; Webb, David F.; McFadden,
Robert H.; Kuchar, Thomas A.; Emery, Barbara A.; McIntosh, Scott W.
Bibcode: 2020SoPh..295..161H
Altcode:
Using the McIntosh Archive of solar features, we analyze the evolution
of coronal holes over more than three solar cycles. We demonstrate
that coronal-hole positions and lifetimes change significantly on time
scales from months to years, and that the pattern of these changes
is clearly linked to the solar-activity cycle. We demonstrate that
the lifetimes of low-latitude coronal holes are usually less than one
rotation but may extend to almost three years. When plotted over time,
the positions of low-latitude coronal holes that remain visible for
over one rotation track the sunspot butterfly diagram in terms of
their positions on the Sun over a solar cycle. Finally, we confirm
that coronal holes do not in general rigidly rotate.
Title: Global maps of the magnetic field in the solar corona
Authors: Yang, Zihao; Bethge, Christian; Tian, Hui; Tomczyk, Steven;
Morton, Richard; Del Zanna, Giulio; McIntosh, Scott W.; Karak, Bidya
Binay; Gibson, Sarah; Samanta, Tanmoy; He, Jiansen; Chen, Yajie;
Wang, Linghua
Bibcode: 2020Sci...369..694Y
Altcode: 2020arXiv200803136Y
Understanding many physical processes in the solar atmosphere requires
determination of the magnetic field in each atmospheric layer. However,
direct measurements of the magnetic field in the Sun’s corona are
difficult to obtain. Using observations with the Coronal Multi-channel
Polarimeter, we have determined the spatial distribution of the
plasma density in the corona and the phase speed of the prevailing
transverse magnetohydrodynamic waves within the plasma. We combined
these measurements to map the plane-of-sky component of the global
coronal magnetic field. The derived field strengths in the corona,
from 1.05 to 1.35 solar radii, are mostly 1 to 4 gauss. Our results
demonstrate the capability of imaging spectroscopy in coronal magnetic
field diagnostics.
Title: Quantifying the Solar Cycle Modulation of Extreme Space Weather
Authors: Chapman, S. C.; McIntosh, S. W.; Leamon, R. J.; Watkins, N. W.
Bibcode: 2020GeoRL..4787795C
Altcode:
By obtaining the analytic signal of daily sunspot numbers since 1818
we construct a new solar cycle phase clock that maps each of the last
18 solar cycles onto a single normalized 11 year epoch. This clock
orders solar coronal activity and extremes of the aa index, which
tracks geomagnetic storms at the Earth's surface over the last 14
solar cycles. We identify geomagnetically quiet intervals that are 40%
of the normalized cycle, ±2π/5 in phase or ±2.2 years around solar
minimum. Since 1868 only two severe (aa>300 nT) and one extreme
(aa>500 nT) geomagnetic storms occurred in quiet intervals; 1-3%
of severe (aa>300 nT) geomagnetic storms and 4-6% of C-, M-,
and X-class solar flares occurred in quiet intervals. This provides
quantitative support to planning resilience against space weather
impacts since only a few percent of all severe storms occur in quiet
intervals and their start and end times are quantifiable.
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.
Bibcode: 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 m2 sail
used in mission assessment is a direct extension of the 4-quadrant,
1,600 m2 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: Physics of Magnetohydrodynamic Rossby Waves in the Sun
Authors: Dikpati, Mausumi; Gilman, Peter A.; Chatterjee, Subhamoy;
McIntosh, Scott W.; Zaqarashvili, Teimuraz V.
Bibcode: 2020ApJ...896..141D
Altcode:
Evidence of the existence of hydrodynamic and MHD Rossby waves in
the Sun is accumulating rapidly. We employ an MHD Rossby wave model
for the Sun in simplified Cartesian geometry, with a uniform toroidal
field and no differential rotation, to analyze the role of each force
that contributes to Rossby wave dynamics, and compute fluid particle
trajectories followed in these waves. This analysis goes well beyond
the traditional formulation of Rossby waves in terms of conservation
of vorticity. Hydrodynamic Rossby waves propagate retrograde relative
to the rotation of the reference frame, while MHD Rossby waves can be
both prograde and retrograde. Fluid particle trajectories are either
clockwise or counterclockwise spirals, depending on where in the wave
pattern they are initiated, that track generally in the direction
of wave propagation. Retrograde propagating MHD Rossby waves move
faster than their hydrodynamic counterparts of the same wavelength,
becoming Alfvén waves at very high field strengths. Prograde MHD
Rossby waves, which have no hydrodynamic counterpart, move more slowly
eastward than retrograde MHD Rossby waves for the same toroidal field,
but with a speed that increases with toroidal field, in the high
field limit again becoming Alfvén waves. The longitude and latitude
structures of all these waves, as seen in their velocity streamlines
and perturbation field lines as well as fluid particle trajectories,
are remarkably similar for different toroidal fields, rotation,
longitudinal wavelength, and direction of propagation.
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.
Bibcode: 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
Bibcode: 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: Space Weather Challenge and Forecasting Implications of
Rossby Waves
Authors: Dikpati, Mausumi; McIntosh, Scott W.
Bibcode: 2020SpWea..1802109D
Altcode:
Rossby waves arise in thin layers within fluid regions of stars and
planets. These global wave-like patterns occur due to the variation in
Coriolis forces with latitude. In the past several years observational
evidence has indicated that there are also Rossby waves in the
Sun. Although Rossby waves have been detected in the Sun's photosphere
and corona, they most likely originate in the solar tachocline, the
sharp shear layer at the base of the solar convection zone, where the
differential rotation driven by convection transitions to the solidly
rotating radiative interior. These waves differ from their Earth's
counterparts by being strongly modified by toroidal magnetic fields
in the solar tachocline. Recent simulations of magnetohydrodynamics
of tachocline Rossby waves and magnetic fields are demonstrated to
produce strong "tachocline nonlinear oscillations," which have periods
similar to those observed in the solar atmosphere—enhanced periods
of solar activity, or "seasons"—occurring at intervals between six
months and two years. These seasonal/subseasonal bursts produce the
strongest eruptive space weather events. Thus, a key to forecasting
the timing, amplitude, and location of future activity bursts, and
hence space weather events, could lie in our ability to forecast the
phase and amplitude of Rossby waves and associated tachocline nonlinear
oscillations. Accurately forecasting the properties of solar Rossby
waves and their impact on space weather will require linking surface
activity observations to the magnetohydrodynamics of tachocline Rossby
waves, using modern data assimilation techniques. Both short-term
(hours to days) and long-term (decadal to millennial) forecasts of
space weather and climate are now being made. We highlight in this
article the potential of solar Rossby waves for forecasting space
weather on intermediate time scales, of several weeks to months up to
a few years ahead.
Title: Time-Latitude Distribution of Prominences for 10 Solar Cycles:
A Study Using Kodaikanal, Meudon, and Kanzelhohe Data
Authors: Chatterjee, Subhamoy; Hegde, Manjunath; Banerjee, Dipankar;
Ravindra, B.; McIntosh, Scott W.
Bibcode: 2020E&SS....700666C
Altcode: 2018arXiv180207556C
Solar prominences are structures of importance because of their role
in polar field reversal. We study the long-term variation of the
time latitude distribution of solar prominences in this article. To
accomplish this, we primarily used the digitized disc-blocked Ca II
K spectroheliograms as recorded from Kodaikanal Solar Observatory for
the period of 1906-2002. For improving the data statistics we included
full disc Hα images from Meudon and Kanzelhohe Observatory,
which are available after 1980. We developed an automated technique
to identify the latitudinal locations of prominences in daily images
from all three data sets. Derived time-latitude distribution clearly
depicted poleward migration of prominence structures for 10 cycles
(15-24). Unlike previous studies, we separated the rate of poleward
migration during onset and near pole, using piece-wise linear fits. In
most cases, we found acceleration in poleward migration with the
change occurring near ±70° latitudes. The derived migration rates
for such large number of solar cycles can provide important inputs
toward understanding polar field buildup process.
Title: Timing Terminators: Forecasting Sunspot Cycle 25 Onset
Authors: Leamon, Robert J.; McIntosh, Scott W.; Chapman, Sandra C.;
Watkins, Nicholas W.
Bibcode: 2020SoPh..295...36L
Altcode: 2019arXiv190906603L
Recent research has demonstrated the existence of a new type of solar
event, the "terminator." Unlike the Sun's signature events, flares and
coronal mass ejections, the terminator most likely originates in the
solar interior, at or near the tachocline. The terminator signals the
end of a magnetic activity cycle at the Sun's equator and the start
of a sunspot cycle at mid-latitudes. Observations indicate that the
time difference between these events is very short, less than a solar
rotation, in the context of the sunspot cycle. As the (definitive)
start and end point of solar activity cycles the precise timing of
terminators should permit new investigations into the meteorology of
our star's atmosphere. In this article we use a standard method in
signal processing, the Hilbert transform, to identify a mathematically
robust signature of terminators in sunspot records and in radiative
proxies. Using a linear extrapolation of the Hilbert phase of the
sunspot number and F10.7 cm solar radio flux time series we can achieve
higher fidelity historical terminator timing than previous estimates
have permitted. Further, this method presents a unique opportunity
to project, from analysis of sunspot data, when the next terminator
will occur, May 2020 (+4 , −1.5 months), and trigger the growth of
Sunspot Cycle 25.
Title: Dynamics of the Sun and Stars; Honoring the Life and Work of
Michael J. Thompson
Authors: Monteiro, Mário J. P. F. G.; García, Rafael A.;
Christensen-Dalsgaard, Jørgen; McIntosh, Scott W.
Bibcode: 2020ASSP...57.....M
Altcode:
No abstract at ADS
Title: Open Discussion
Authors: García, R. A.; Mathur, S.; Monteiro, M. J. P. F. G.;
Christensen-Dalsgaard, J.; McIntosh, S. W.
Bibcode: 2020ASSP...57..329G
Altcode:
During the last morning of the conference, a one-hour open discussion
allowed the participants to debate some of the "hot" topics presented
all along the meeting as well as on some of the key issues in the field
mostly related with the work Prof. Michael J. Thompson studied during
his carrier. The discussion covered theory and methods, current and
future modeling efforts, observations, and future instrumentation. At
the end, Dr. Robin Thompson discussed about the use of inversion
methods in his current research, of particular interest these days,
about the control of infectious disease outbreaks.
Title: Timing Terminators: Forecasting Sunspot Cycle 25 Onset,
Activity Levels and Overcoming Social Constraints That Hamper Progress
Authors: Leamon, R. J.; McIntosh, S. W.
Bibcode: 2019AGUFMSA11C3234L
Altcode:
Recent research has demonstrated the existence of a new type of
solar event, the ``terminator''. Unlike the Sun's signature events,
flares and Coronal Mass Ejections, the terminator takes place in
the solar interior. The terminator signals the end of a magnetic
activity cycle at the Sun's equator and the start of a sunspot cycle
at mid latitudes. Observations indicate that the time difference
between these events is very short, less than a solar rotation, in the
context of the sunspot cycle. As the (definitive) start and end point of
solar activity cycles the precise timing of terminators should permit
new investigations into the meteorology of our star's atmosphere. In
this letter we use a standard method in signal processing, the Hilbert
transform, to identify a mathematically robust signature of terminators
in sunspot records and in radiative proxies. Using this technique we
can achieve higher fidelity terminator timing than previous estimates
have permitted. Further, this method presents a unique opportunity to
project when the next terminator will occur, 2020.33(± 0.16), and
trigger the growth of sunspot cycle 25. We also will use this
method to show why Cycle 23 was unusually long, why the Cycle 23-24
minimum was unusually quiet, and why neither of these occurrences
will happen with the end of Cycle 24. Ignoring the wealth of
observational evidence and viewing the solar activity cycle as merely
the growth and decay of sunspot number is one ``social constraint that
hampers progress" to be overcome.
Title: Coronal Solar Magnetism Observatory Science Objectives
Authors: Gibson, S. E.; Tomczyk, S.; Burkepile, J.; Casini, R.;
DeLuca, E.; de Toma, G.; de Wijn, A.; Fan, Y.; Golub, L.; Judge,
P. G.; Landi, E.; McIntosh, S. W.; Reeves, K.; Seaton, D. B.; Zhang, J.
Bibcode: 2019AGUFMSH11C3395G
Altcode:
Space-weather forecast capability is held back by our current
lack of basic scientific understanding of CME magnetic evolution,
and the coronal magnetism that structures and drives the solar
wind. Comprehensive observations of the global magnetothermal
environment of the solar atmosphere are needed for progress. When fully
implemented, the COSMO suite of synoptic ground-based telescopes will
provide the community with comprehensive and simultaneous measurements
of magnetism, temperature, density and plasma flows and waves from the
photosphere through the chromosphere and out into the corona. We will
discuss how these observations will uniquely address a set of science
objectives that are central to the field of solar and space physics:
in particular, to understand the storage and release of magnetic energy,
to understand CME dynamics and consequences for shocks, to determine the
role of waves in solar atmospheric heating and solar wind acceleration,
to understand how the coronal magnetic field relates to the solar
dynamo, and to constrain and improve space-weather forecast models.
Title: A comprehensive three-dimensional radiative magnetohydrodynamic
simulation of a solar flare
Authors: Cheung, M. C. M.; Rempel, M.; Chintzoglou, G.; Chen, F.;
Testa, P.; Martínez-Sykora, J.; Sainz Dalda, A.; DeRosa, M. L.;
Malanushenko, A.; Hansteen, V.; De Pontieu, B.; Carlsson, M.; Gudiksen,
B.; McIntosh, S. W.
Bibcode: 2019NatAs...3..160C
Altcode: 2018NatAs...3..160C
Solar and stellar flares are the most intense emitters of X-rays and
extreme ultraviolet radiation in planetary systems1,2. On
the Sun, strong flares are usually found in newly emerging sunspot
regions3. The emergence of these magnetic sunspot groups
leads to the accumulation of magnetic energy in the corona. When
the magnetic field undergoes abrupt relaxation, the energy released
powers coronal mass ejections as well as heating plasma to temperatures
beyond tens of millions of kelvins. While recent work has shed light
on how magnetic energy and twist accumulate in the corona4
and on how three-dimensional magnetic reconnection allows for rapid
energy release5,6, a self-consistent model capturing how
such magnetic changes translate into observable diagnostics has remained
elusive. Here, we present a comprehensive radiative magnetohydrodynamics
simulation of a solar flare capturing the process from emergence to
eruption. The simulation has sufficient realism for the synthesis of
remote sensing measurements to compare with observations at visible,
ultraviolet and X-ray wavelengths. This unifying model allows us to
explain a number of well-known features of solar flares7,
including the time profile of the X-ray flux during flares, origin
and temporal evolution of chromospheric evaporation and condensation,
and sweeping of flare ribbons in the lower atmosphere. Furthermore,
the model reproduces the apparent non-thermal shape of coronal X-ray
spectra, which is the result of the superposition of multi-component
super-hot plasmas8 up to and beyond 100 million K.
Title: Spectropolarimetry of the Solar Mg II h and k Lines
Authors: Manso Sainz, R.; del Pino Alemán, T.; Casini, R.; McIntosh,
S.
Bibcode: 2019ApJ...883L..30M
Altcode: 2019arXiv190905574M
We report on spectropolarimetric observations across the Mg II h and k
lines at 2800 Å made by the Ultraviolet Spectrometer and Polarimeter
on board the Solar Maximum Mission satellite. Our analysis confirms
the strong linear polarization in the wings of both lines observed
near the limb, as previously reported, but also demonstrates the
presence of a negatively (i.e., radially oriented) polarized signal
between the two lines. We find evidence for fluctuations of the
polarization pattern over a broad spectral range, resulting in some
depolarization with respect to the pure scattering case when observed
at very low spatial and temporal resolutions. This is consistent with
recent theoretical modeling that predicts this to be the result of
redistribution effects, quantum interference between the atomic levels
of the upper term, and magneto-optical effects. A first attempt at a
quantitative exploitation of these signals for the diagnosis of magnetic
fields in the chromosphere is attempted. In active regions, we present
observations of circular polarization dominated by the Zeeman effect. We
are able to constrain the magnetic field strength in the upper active
chromosphere using an analysis based on the magnetograph formula, as
justified by theoretical modeling. We inferred a significantly strong
magnetic field (∼500 G) at the 2.5σ level on an exceptionally active,
flaring region.
Title: Investigating Coronal Magnetism with COSMO: Science on
the Critical Path To Understanding The ``Weather'' of Stars and
Stellarspheres
Authors: McIntosh, Scott; Tomczyk, Steven; Gibson, Sarah E.; Burkepile,
Joan; de Wijn, Alfred; Fan, Yuhong; deToma, Giuliana; Casini, Roberto;
Landi, Enrico; Zhang, Jie; DeLuca, Edward E.; Reeves, Katharine K.;
Golub, Leon; Raymond, John; Seaton, Daniel B.; Lin, Haosheng
Bibcode: 2019BAAS...51g.165M
Altcode: 2019astro2020U.165M
The Coronal Solar Magnetism Observatory (COSMO) is a unique ground-based
facility designed to address the shortfall in our capability to measure
magnetic fields in the solar corona.
Title: What the Sudden Death of Solar Cycles Can Tell Us About the
Nature of the Solar Interior
Authors: McIntosh, Scott W.; Leamon, Robert J.; Egeland, Ricky;
Dikpati, Mausumi; Fan, Yuhong; Rempel, Matthias
Bibcode: 2019SoPh..294...88M
Altcode: 2019arXiv190109083M
We observe the abrupt end of solar-activity cycles at the Sun's
Equator by combining almost 140 years of observations from ground and
space. These "terminator" events appear to be very closely related to
the onset of magnetic activity belonging to the next solar cycle at
mid-latitudes and the polar-reversal process at high latitudes. Using
multi-scale tracers of solar activity we examine the timing of these
events in relation to the excitation of new activity and find that the
time taken for the solar plasma to communicate this transition is of
the order of one solar rotation - but it could be shorter. Utilizing
uniquely comprehensive solar observations from the Solar Terrestrial
Relations Observatory (STEREO) and Solar Dynamics Observatory (SDO)
we see that this transitional event is strongly longitudinal in
nature. Combined, these characteristics suggest that information
is communicated through the solar interior rapidly. A range of
possibilities exist to explain such behavior: for example gravity
waves on the solar tachocline, or that the magnetic fields present
in the Sun's convection zone could be very large, with a poloidal
field strengths reaching 50 kG - considerably larger than conventional
explorations of solar and stellar dynamos estimate. Regardless of the
mechanism responsible, the rapid timescales demonstrated by the Sun's
global magnetic-field reconfiguration present strong constraints on
first-principles numerical simulations of the solar interior and,
by extension, other stars.
Title: Radiative MHD Simulation of a Solar Flare
Authors: Cheung, Mark; Rempel, Matthias D.; Chintzoglou, Georgios;
Chen, Feng; Testa, Paola; Martinez-Sykora, Juan; Sainz Dalda, Alberto;
DeRosa, Marc L.; Malanushenko, Anna; Hansteen, Viggo; Carlsson, Mats;
De Pontieu, Bart; Gudiksen, Boris; McIntosh, Scott W.
Bibcode: 2019AAS...23431005C
Altcode:
We present a radiative MHD simulation of a solar flare. The
computational domain captures the near-surface layers of the convection
zone and overlying atmosphere. Inspired by the observed evolution of
NOAA Active Region (AR) 12017, a parasitic bipolar region is imposed
to emerge in the vicinity of a pre-existing sunspot. The emergence of
twisted magnetic flux generates shear flows that create a pre-existing
flux rope underneath the canopy field of the sunspot. Following erosion
of the overlying bootstrapping field, the flux rope erupts. Rapid
release of magnetic energy results in multi-wavelength synthetic
observables (including X-ray spectra, narrowband EUV images, Doppler
shifts of EUV lines) that are consistent with flare observations. This
works suggests the super-position of multi-thermal, superhot (up
to 100 MK) plasma may be partially responsible for the apparent
non-thermal shape of coronal X-ray sources in flares. Implications
for remote sensing observations of other astrophysical objects is also
discussed. This work is an important stepping stone toward high-fidelity
data-driven MHD models.
Title: Terminators: Predicting the end of sunspot cycle 24 and its
impacts on space weather, weather and climate.
Authors: Leamon, Robert; McIntosh, Scott W.
Bibcode: 2019AAS...23430503L
Altcode:
Recent research has demonstrated the existence of a new type of solar
"event." Unlike the signature events in the corona, flares and Coronal
Mass Ejections, this event, the Terminator, takes place in the solar
interior (at the Sun's equator), signalling the end of a magnetic
activity cycle and the start of a sunspot cycle at mid latitudes -
all at the same time. Observations indicate that the hand-over between
the termination of the magnetic activity cycle and the blooming of the
next sunspot cycle could be very short, possibly much less than a solar
rotation. Here we demonstrate the impact of these terminators on
the Sun's radiative output and particulate shielding of our atmosphere
through the dramatically rapid reconfiguration of solar magnetism. Using
direct observation and proxies of solar activity going back six decades
we can, with high statistical significance, demonstrate an apparent
correlation between the solar cycle terminations and the largest swings
of Earth's oceanic indices - a previously overlooked correspondence. We then use a standard method in signal processing, the Hilbert
transform, to investigate the presence, and identify the signature, of
terminators in solar magnetic and radiative proxies. Using many decades
of such data we can achieve higher fidelity on terminator timing than
previous estimates have allowed. The distinct signature presents
a unique opportunity to project when the next terminator will occur,
April 2020 (± two months) and sunspot cycle 25 will commence its growth
phase. Further, April 2020 implies cycle 24 will only be 9.25 years
long; we offer an explanation as to why cycle 24 is short (or rather,
why cycle 23 and its "unusual solar minimum" was so long). Finally,
should a major ENSO swing follow next year, our challenge becomes:
when does correlation become causation and how does the process work?
Title: Eclipse Megamovie 2017 Successes and Potential For Future Work
Authors: Peticolas, L.; Hudson, H.; Johnson, C.; Zevin, D.; White,
V.; Oliveros, J. C. M.; Ruderman, I.; Koh, J.; Konerding, D.; Bender,
M.; Cable, C.; Kruse, B.; Yan, D.; Krista, L.; Collier, B.; Fraknoi,
A.; Pasachoff, J. M.; Filippenko, A. V.; Mendez, B.; McIntosh, S. W.;
Filippenko, N. L.
Bibcode: 2019ASPC..516..337P
Altcode:
In 2011, an "Eclipse Megamovie" was envisioned for the 2017 total
solar eclipse that would be created using the public's photographs of
the Sun's corona as frames in a movie illuminating dynamic changes in
the chromosphere and corona. On August 21, 2017, our team collected
photographs of the total solar eclipse from thousands of volunteers
with telescopes, DSLR (Digital Single-Lens Reflex) cameras, and mobile
device cameras setup across the path of totality. Our efforts resulted
in 1,190 photographers contributing 50,016 DSLR photographs in a final
open-source, public archive that is 766 GB in size. All photographs
in this archive are Creative Commons zero (CC0), making them freely
available for public use. From mobile devices, we obtained an archive
of 60,000 images, 211 GB in size. The first Eclipse Megamovie video
was compiled and made available to the public a few hours after the
Moon's shadow left the U.S. East Coast. For two weeks, additional
images were added to this video, as volunteers uploaded them to the
project server. The project also resulted in a comprehensive website
with 12,749 users sufficiently interested in the project to each create
a user profile on the website, several short documentaries, 190 articles
and press releases, open-source code for use in future related efforts,
and hundreds of public presentations across the country prior to the
eclipse. Information on how to access these resources is included in
this paper.
Title: COSMO Science
Authors: Gibson, Sarah; Tomczyk, Steven; Burkepile, Joan; Casini,
Roberto; Deluca, Ed; de Toma, Giuliana; deWijn, Alfred; Fan, Yuhong;
Golub, Leon; Judge, Philip; Landi, Enrico; Lin, Haosheng; McIntosh,
Scott; Reeves, Kathy; Seaton, Dan; Zhang, Jie
Bibcode: 2019shin.confE..32G
Altcode:
Space-weather forecast capability is held back by our current
lack of basic scientific understanding of CME magnetic evolution,
and the coronal magnetism that structures and drives the solar
wind. Comprehensive observations of the global magnetothermal
environment of the solar atmosphere are needed for progress. When fully
implemented, the COSMO suite of synoptic ground-based telescopes will
provide the community with comprehensive and simultaneous measurements
of magnetism, temperature, density and plasma flows and waves from the
photosphere through the chromosphere and out into the corona. We will
discuss how these observations will uniquely address a set of science
objectives that are central to the field of solar and space physics:
in particular, to understand the storage and release of magnetic energy,
to understand CME dynamics and consequences for shocks, to determine the
role of waves in solar atmospheric heating and solar wind acceleration,
to understand how the coronal magnetic field relates to the solar
dynamo, and to constrain and improve space-weather forecast models.
Title: Investigating Coronal Magnetism with COSMO: Science on
the Critical Path To Understanding The "Weather" of Stars and
Stellarspheres
Authors: McIntosh, Scott; Tomczyk, Steven
Bibcode: 2019BAAS...51c.407M
Altcode: 2019astro2020T.407M
The white paper discusses the measurement of coronal magnetism as
a gateway to improving our understanding of the heliosphere, drive
improvements in space weather and ultimately understanding stellar
coronae and stellar weather.
Title: Impact of solar Rossby waves in driving space weather
Authors: Dikpati, Mausumi; McIntosh, Scott W.
Bibcode: 2019shin.confE.103D
Altcode:
Forecasting our weather was built on the recognition that Rossby
waves are largely responsible for the jet streams, winter storms
and cold outbreaks. Over the past 75 years, there have been enormous
improvements in our ability to forecast important weather events up to
a week or more in advance, using increasingly complex computational
models that use all available observations of the weather, by means
of data assimilation. Solar Rossby waves have been discovered, so
something very similar is possible for forecasting the 'space weather'
created in the Sun that has so much impact on our technology-dependent
society. In the solar case, Rossby waves, influenced by strong magnetic
fields near the base of the Sun's convection zone at the tachocline,
interact with the differential rotation there to create Tachocline
Nonlinear Oscillations (TNOs) that can be responsible for the 'bursts'
of space weather we see at the solar surface, which extend out into the
heliosphere in the form of flares and coronal mass ejections. Bursty
'seasons' of activity are followed several months later by a quiet
season. These quasi-periodic bursty seasons are the origin of most
of the strongest space weather events that impact the Earth. Our TNO
model shows that most emergence of new magnetic flux to the surface
to create solar activity should occur when the amplitude of Rossby
waves is at or near its maximum, when the tachocline has the largest
'bulges' into the convection zone above. Toroidal field in these bulges
is more likely to reach the photosphere than fields at other longitudes
and latitudes and at times when the Rossby waves are weaker. We will
describe how future TNOs and associated solar activity can be simulated
and forecast by linking surface activity observations to the tachocline
MHD, using modern data assimilation techniques."
Title: Signature of Extended Solar Cycles as Detected from Ca II K
Synoptic Maps of Kodaikanal and Mount Wilson Observatory
Authors: Chatterjee, Subhamoy; Banerjee, Dipankar; McIntosh, Scott
W.; Leamon, Robert J.; Dikpati, Mausumi; Srivastava, Abhishek K.;
Bertello, Luca
Bibcode: 2019ApJ...874L...4C
Altcode: 2019arXiv190303598C
In recent years there has been a resurgence of the study of extended
solar cycles (ESCs) through observational proxies mainly in extreme
ultraviolet. But most of them are limited only to the space-based era
covering only about two solar cycles. Long-term historical data sets
are worth examining for the consistency of ESCs. The Kodaikanal Solar
Observatory (KSO) and the Mount Wilson Observatory (MWO) are two major
sources of long-term Ca II K digitized spectroheliograms covering the
temporal spans of 1907-2007 and 1915-1985 respectively. In this study,
we detected supergranule boundaries, commonly known as networks, using
the Carrington maps from both KSO and MWO data sets. Subsequently
we excluded the plage areas to consider only the quiet Sun (QS) and
detected small-scale bright features through intensity thresholding
over the QS network. Latitudinal density of those features, which we
named “Network Bright Elements,” could clearly depict the existence
of overlapping cycles with equatorward branches starting at latitude
≈55° and taking about 15 ± 1 yr to reach the equator. We performed
a superposed epoch analysis to depict the similarity of those extended
cycles. Knowledge of such equatorward band interaction, for several
cycles, may provide critical constraints on solar dynamo models.
Title: Triggering The Birth of New Cycle's Sunspots by Solar Tsunami
Authors: Dikpati, Mausumi; McIntosh, Scott W.; Chatterjee, Subhamoy;
Banerjee, Dipankar; Yellin-Bergovoy, Ron; Srivastava, Abhishek
Bibcode: 2019NatSR...9.2035D
Altcode:
When will a new cycle's sunspots appear? We demonstrate a novel
physical mechanism, namely, that a "solar tsunami" occurring in the
Sun's interior shear-fluid layer can trigger new cycle's magnetic
flux emergence at high latitudes, a few weeks after the cessation of
old cycle's flux emergence near the equator. This tsunami is excited
at the equator when magnetic dams, created by the oppositely-directed
old cycle's toroidal field in North and South hemispheres, break due
to mutual annihilation of toroidal flux there. The fluid supported
by these dams rushes to the equator; the surplus of fluid cannot be
contained there, so it reflects back towards high latitudes, causing
a tsunami. This tsunami propagates poleward at a speed of 300 m/s
until it encounters the new cycle's spot-producing toroidal fields
in mid-latitudes, where it perturbs the fields, triggering their
surface-eruption in the form of new cycle spots. A new sunspot cycle
is preceded for several years by other forms of high-latitude magnetic
activity, such as coronal bright points and ephemeral regions, until
the tsunami causes the birth of new cycle's spots. The next tsunami
is due by 2020, portending the start of intense `space weather' that
can adversely impact the Earth.
Title: Termination of Solar Cycles and Correlated Tropospheric
Variability
Authors: Leamon, Robert J; McIntosh, Scott W.; Marsh, Daniel R.
Bibcode: 2018arXiv181202692L
Altcode:
The Sun provides the energy required to sustain life on Earth and
drive our planet's atmospheric circulation. However, establishing a
solid physical connection between solar and tropospheric variability
has posed a considerable challenge across the spectrum of Earth-system
science. The canon of solar variability, the solar fiducial clock, lies
almost exclusively with the 400 years of human telescopic observations
that demonstrates the waxing and waning number of sunspots, over an
11(ish) year period. Recent research has demonstrated the critical
importance of the underlying 22-year magnetic polarity cycle in
establishing the shorter sunspot cycle. Integral to the manifestation
of the latter is the spatio-temporal overlapping and migration of
oppositely polarized magnetic bands. The points when these bands emerge
at high solar latitudes and cancel at the equator are separated by
almost 20 years. Here we demonstrate the impact of these "termination"
points on the Sun's radiative output and particulate shielding of
our atmosphere through the dramatically rapid reconfiguration of solar
magnetism. These events reset the Sun's fiducial clock and present a new
portal to explore the Sun-Earth connection. Using direct observation
and proxies of solar activity going back six decades we can, with
high statistical significance, demonstrate an apparent correlation
between the solar cycle terminations and the largest swings of Earth's
oceanic indices---a previously overlooked correspondence. Forecasting
the Sun's global behavior places the next solar termination in early
2020; should a major oceanic swing follow, our challenge becomes:
when does correlation become causation and how does the process work?
Title: The Extended Solar Cycle: Muddying the Waters of Solar/Stellar
Dynamo Modeling Or Providing Crucial Observational Constraints?
Authors: Srivastava, Abhishek K.; McIntosh, Scott W.; Arge,
N.; Banerjee, Dipankar; Dikpati, Mausumi; Dwivedi, Bhola N.;
Guhathakurta, Madhulika; Karak, B. B.; Leamon, Robert J.; Matthew,
Shibu K.; Munoz-Jaramillo, Andres; Nandy, D.; Norton, Aimee; Upton,
L.; Chatterjee, S.; Mazumder, Rakesh; Rao, Yamini K.; Yadav, Rahul
Bibcode: 2018FrASS...5...38S
Altcode: 2018arXiv180707601S
In 1844 Schwabe discovered that the number of sunspots increased and
decreased over a period of about 11 years, that variation became known
as the sunspot cycle. Almost eighty years later, Hale described the
nature of the Sun's magnetic field, identifying that it takes about 22
years for the Sun's magnetic polarity to cycle. It was also identified
that the latitudinal distribution of sunspots resembles the wings of
a butterfly showing migration of sunspots in each hemisphere that
abruptly start at mid-latitudes (about ±35(o) ) towards the Sun's
equator over the next 11 years. These sunspot patterns were shown
to be asymmetric across the equator. In intervening years, it was
deduced that the Sun (and sun-like stars) possess magnetic activity
cycles that are assumed to be the physical manifestation of a dynamo
process that results from complex circulatory transport processes in
the star's interior. Understanding the Sun's magnetism, its origin
and its variation, has become a fundamental scientific objective
the distribution of magnetism, and its interaction with convective
processes, drives various plasma processes in the outer atmosphere
that generate particulate, radiative, eruptive phenomena and shape the
heliosphere. In the past few decades, a range of diagnostic techniques
have been employed to systematically study finer scale magnetized
objects, and associated phenomena. The patterns discerned became
known as the ``Extended Solar Cycle'' (ESC). The patterns of the ESC
appeared to extend the wings of the activity butterfly back in time,
nearly a decade before the formation of the sunspot pattern, and to
much higher solar latitudes. In this short review, we describe their
observational patterns of the ESC and discuss possible connections
to the solar dynamo as we depart on a multi-national collaboration to
investigate the origins of solar magnetism through a blend of archived
and contemporary data analysis with the goal of improving solar dynamo
understanding and modeling.
Title: Roadmap for Reliable Ensemble Forecasting of the Sun-Earth
System
Authors: Nita, Gelu; Angryk, Rafal; Aydin, Berkay; Banda, Juan;
Bastian, Tim; Berger, Tom; Bindi, Veronica; Boucheron, Laura; Cao,
Wenda; Christian, Eric; de Nolfo, Georgia; DeLuca, Edward; DeRosa,
Marc; Downs, Cooper; Fleishman, Gregory; Fuentes, Olac; Gary, Dale;
Hill, Frank; Hoeksema, Todd; Hu, Qiang; Ilie, Raluca; Ireland,
Jack; Kamalabadi, Farzad; Korreck, Kelly; Kosovichev, Alexander;
Lin, Jessica; Lugaz, Noe; Mannucci, Anthony; Mansour, Nagi; Martens,
Petrus; Mays, Leila; McAteer, James; McIntosh, Scott W.; Oria, Vincent;
Pan, David; Panesi, Marco; Pesnell, W. Dean; Pevtsov, Alexei; Pillet,
Valentin; Rachmeler, Laurel; Ridley, Aaron; Scherliess, Ludger; Toth,
Gabor; Velli, Marco; White, Stephen; Zhang, Jie; Zou, Shasha
Bibcode: 2018arXiv181008728N
Altcode:
The authors of this report met on 28-30 March 2018 at the New Jersey
Institute of Technology, Newark, New Jersey, for a 3-day workshop
that brought together a group of data providers, expert modelers, and
computer and data scientists, in the solar discipline. Their objective
was to identify challenges in the path towards building an effective
framework to achieve transformative advances in the understanding
and forecasting of the Sun-Earth system from the upper convection
zone of the Sun to the Earth's magnetosphere. The workshop aimed to
develop a research roadmap that targets the scientific challenge
of coupling observations and modeling with emerging data-science
research to extract knowledge from the large volumes of data (observed
and simulated) while stimulating computer science with new research
applications. The desire among the attendees was to promote future
trans-disciplinary collaborations and identify areas of convergence
across disciplines. The workshop combined a set of plenary sessions
featuring invited introductory talks and workshop progress reports,
interleaved with a set of breakout sessions focused on specific topics
of interest. Each breakout group generated short documents, listing
the challenges identified during their discussions in addition to
possible ways of attacking them collectively. These documents were
combined into this report-wherein a list of prioritized activities
have been collated, shared and endorsed.
Title: Solar Physics from Unconventional Viewpoints
Authors: Gibson, Sarah E.; Vourlidas, Angelos; Hassler, Donald M.;
Rachmeler, Laurel A.; Thompson, Michael J.; Newmark, Jeffrey; Velli,
Marco; Title, Alan; McIntosh, Scott W.
Bibcode: 2018FrASS...5...32G
Altcode: 2018arXiv180509452G
We explore new opportunities for solar physics that could be realized
by future missions providing sustained observations from vantage
points away from the Sun-Earth line. These include observations from
the far side of the Sun, at high latitudes including over the solar
poles, or from near-quadrature angles relative to the Earth (e.g.,
the Sun-Earth L4 and L5 Lagrangian points). Such observations fill
known holes in our scientific understanding of the three-dimensional,
time-evolving Sun and heliosphere, and have the potential to open new
frontiers through discoveries enabled by novel viewpoints.
Title: Phase Speed of Magnetized Rossby Waves that Cause Solar Seasons
Authors: Dikpati, Mausumi; Belucz, Bernadett; Gilman, Peter A.;
McIntosh, Scott W.
Bibcode: 2018ApJ...862..159D
Altcode:
Motivated by recent analysis of solar observations that show evidence of
propagating Rossby waves in coronal holes and bright points, we compute
the longitudinal phase velocities of unstable MHD Rossby waves found in
an MHD shallow-water model of the solar tachocline (both overshoot and
radiative parts). We demonstrate that phase propagation is a typical
characteristic of tachocline nonlinear oscillations that are created by
unstable MHD Rossby waves, responsible for producing solar seasons. For
toroidal field bands placed at latitudes between 5° and 75°, we find
that phase velocities occur in a range similar to the observations,
with more retrograde speeds (relative to the solar core rotation rate)
for bands placed at higher latitudes, just as coronal holes have at high
latitudes compared to low ones. The phase speeds of these waves are
relatively insensitive to the toroidal field peak amplitude. Rossby
waves for single bands at 25° are slightly prograde. However, at
latitudes lower than 25° they are very retrograde, but much less so if
a second band is included at a much higher latitude. This double-band
configuration is suggested by evidence of an extended solar cycle,
containing a high-latitude band in its early stages that does not
yet produce spots, while the spot-producing low-latitude band is
active. Collectively, our results indicate a strong connection between
longitudinally propagating MHD Rossby waves in the tachocline and
surface manifestations in the form of similarly propagating coronal
holes and patterns of bright points.
Title: The Coronal Solar Magnetism Observatory
Authors: Thompson, Michael J.; Tomczyk, Steven; Gibson, Sarah E.;
McIntosh, Scott W.; Landi, Enrico
Bibcode: 2018IAUS..335..359T
Altcode:
The Coronal Solar Magnetism Observatory (CoSMO) is a proposed new
facility led by the High Altitude Observatory and a consortium of
partners to measure magnetic field and plasma properties in a large
(one degree) field of view extending down to the inner parts of the
solar corona. CoSMO is intended as a research facility that will
advance the understanding and prediction of space weather. The
instrumentation elements of CoSMO are: a white-light coronagraph
(KCor), already operational at the Mauna Loa Solar Observatory
(MLSO); the Chromosphere and Prominence Magnetometer (ChroMag), due
for deployment to MLSO next year; and the CoSMO Large Coronagraph (LC)
which has completed Preliminary Design Review.
Title: The latitudinal drift of solar coronal holes
Authors: Krista, Larisza Diana; McIntosh, Scott
Bibcode: 2018shin.confE.259K
Altcode:
In 2011, three satellites - the Solar-Terrestrial RElations Observatory
(STEREO) A & B, and the Solar Dynamics Observatory (SDO) - were in a
unique spatial alignment that allowed a 360 degree view of the Sun. This
alignment lasted until 2014, the peak of solar cycle 24. Using extreme
ultraviolet images and Hovmoller diagrams, we studied the lifetimes
and propagation characteristics of coronal holes (CHs) in longitude
over several solar rotations.
Title: The Heliospheric Meteorology Mission: A Mission to DRIVE our
Understanding of Heliospheric Variability
Authors: McIntosh, Scott W.; Leamon, Robert J.
Bibcode: 2018FrASS...5...21M
Altcode:
To make transformational scientific progress with the space weather
enterprise the Sun, Earth, and heliosphere must be studied as
a coupled system, comprehensively. Rapid advances were made in the
study, and forecasting, of terrestrial meteorology half a century ago
that accompanied the dawn of earth observing satellites. Those assets
provided a global perspective on the Earth's weather systems and the
ability to look ahead of the observer's local time. From a heliospheric,
or space, weather perspective we have the same fundamental limitation
as the terrestrial meteorologists had - by far the majority of our
observing assets are tied to the Sun-Earth line - our planet's "local
time" with respect to the Sun. This perspective intrinsically limits
our ability to "see what is coming around the solar limb" far less to
gain any insight into the global patterns of solar weather and how they
guide weather throughout the heliosphere. We propose a mission concept
- the Heliospheric Meteorology Mission (HMM) - to sample the complete
magnetic and thermodynamic state of the heliosphere inside 1AU using
a distributed network of deep space hardened smallsats that encompass
the Sun. The observations and in situ plasma measurements made by the
fleet of HMM smallsats would be collected, and assimilated into current
operational space weather models. Further, the HMM measurements would
also being used in an nationally coordinated research effort - at the
frontier of understanding the coupled heliospheric system.
Title: Solar Observations Away from the Sun-Earth Line
Authors: Gibson, Sarah E.; McIntosh, Scott William; Rachmeler,
Laurel; Thompson, Michael J.; Title, Alan M.; Velli, Marco C. M.;
Vourlidas, Angelos
Bibcode: 2018tess.conf40340G
Altcode:
Observations from satellite missions have transformed the field of solar
physics. High-resolution observations with near-continuous temporal
coverage have greatly extended our capability for studying long-term
and transient phenomena, and the opening of new regions of the solar
spectrum has made detailed investigation of the solar atmosphere
possible. However, to date most solar space-based missions
have been restricted to an observational vantage in the vicinity of
the Sun-Earth line, either in orbit around the Earth or from the L1
Lagrangian point. As a result, observations from these satellites
represent the same geometrical view of the Sun that is accessible
from the Earth. Understanding the deep interior structure of the
Sun and the full development of solar activity would really benefit
from fully three-dimensional monitoring of the solar atmosphere and
heliosphere. On the one hand, simultaneous spacecraft observations
from multiple vantage points would allow studies of the deep interior
structure of the sun via stereoscopic helioseismology; on the other,
distributed observations would allow the understanding of the complete
evolution of activity complexes and enhance space weather predictions
dramatically. Presently, observations of the Sun away from Earth
are obtained by the STEREO pair of satellites, which have provided
an unprecedented global view by orbiting around to the far side of
the Sun, and the Ulysses mission, which achieved a high-inclination
(80˚) near-polar orbit (but which, however, did not include any solar
imaging instruments). The forthcoming Solar Orbiter mission, which
will orbit the sun and reach a maximum inclination of 34˚ out of the
ecliptic should provide the first detailed mapping of the sun's polar
fields. In addition, Solar Probe Plus will explore the outer corona
and inner Heliosphere with very rapid solar encounters at a minimum
perihelion 9.86 solar radii from the center of the Sun. We explore
some of the new opportunities for solar physics that can be realized
by future missions that provide sustained observations from vantage
points away from the Sun-Earth line (and in some cases the ecliptic
plane): observations from the far side of the Sun, over its poles,
or from the L5 Lagrangian point.
Title: The Longitudinal Evolution of Equatorial Coronal Holes
Authors: Krista, Larisza D.; McIntosh, Scott W.; Leamon, Robert J.
Bibcode: 2018AJ....155..153K
Altcode:
In 2011, three satellites—the Solar-Terrestrial RElations Observatory
A & B, and the Solar Dynamics Observatory (SDO)—were in a
unique spatial alignment that allowed a 360° view of the Sun. This
alignment lasted until 2014, the peak of solar cycle 24. Using extreme
ultraviolet images and Hovmöller diagrams, we studied the lifetimes
and propagation characteristics of coronal holes (CHs) in longitude
over several solar rotations. Our initial results show at least three
distinct populations of “low-latitude” or “equatorial” CHs
(below 65^\circ latitude). One population rotates in retrograde
direction and coincides with a group of long-lived (over sixty days)
CHs in each hemisphere. These are typically located between 30°
and 55^\circ , and display velocities of ∼55 m s-1
slower than the local differential rotation rate. A second, smaller
population of CHs rotate prograde, with velocities between ∼20 and
45 m s-1. This population is also long-lived, but observed
±10° from the solar equator. A third population of CHs are short-lived
(less than two solar rotations), and they appear over a wide range
of latitudes (±65°) and exhibit velocities between -140 and 80 m
s-1. The CH “butterfly diagram” we developed shows a
systematic evolution of the longer-lived holes; however, the sample
is too short in time to draw conclusions about possible connections
to dynamo-related phenomena. An extension of the present work to the
22 years of the combined SOHO-SDO archives is necessary to understand
the contribution of CHs to the decadal-scale evolution of the Sun.
Title: Erratum: “On the Magnetic and Energy
Characteristics of Homologous Jets From an Emerging Flux” (2016, ApJ, 833,
150)
Authors: Liu, Jiajia; Wang, Yuming; Erdélyi, Robertus; Liu, Rui;
McIntosh, Scott W.; Gou, Tingyu; Chen, Jun; Liu, Kai; Liu, Lijuan;
Pan, Zonghao
Bibcode: 2018ApJ...853..201L
Altcode:
No abstract at ADS
Title: Role of Interaction between Magnetic Rossby Waves and
Tachocline Differential Rotation in Producing Solar Seasons
Authors: Dikpati, Mausumi; McIntosh, Scott W.; Bothun, Gregory; Cally,
Paul S.; Ghosh, Siddhartha S.; Gilman, Peter A.; Umurhan, Orkan M.
Bibcode: 2018ApJ...853..144D
Altcode:
We present a nonlinear magnetohydrodynamic shallow-water model
for the solar tachocline (MHD-SWT) that generates quasi-periodic
tachocline nonlinear oscillations (TNOs) that can be identified with
the recently discovered solar “seasons.” We discuss the properties
of the hydrodynamic and magnetohydrodynamic Rossby waves that interact
with the differential rotation and toroidal fields to sustain these
oscillations, which occur due to back-and-forth energy exchanges among
potential, kinetic, and magnetic energies. We perform model simulations
for a few years, for selected example cases, in both hydrodynamic and
magnetohydrodynamic regimes and show that the TNOs are robust features
of the MHD-SWT model, occurring with periods of 2-20 months. We find
that in certain cases multiple unstable shallow-water modes govern
the dynamics, and TNO periods vary with time. In hydrodynamically
governed TNOs, the energy exchange mechanism is simple, occurring
between the Rossby waves and differential rotation. But in MHD cases,
energy exchange becomes much more complex, involving energy flow among
six energy reservoirs by means of eight different energy conversion
processes. For toroidal magnetic bands of 5 and 35 kG peak amplitudes,
both placed at 45° latitude and oppositely directed in north and south
hemispheres, we show that the energy transfers responsible for TNO, as
well as westward phase propagation, are evident in synoptic maps of the
flow, magnetic field, and tachocline top-surface deformations. Nonlinear
mode-mode interaction is particularly dramatic in the strong-field
case. We also find that the TNO period increases with a decrease in
rotation rate, implying that the younger Sun had more frequent seasons.
Title: Terminator 2020: Get Ready for the "Event" of The Next Decade
Authors: McIntosh, S. W.; Leamon, R. J.; Fan, Y.; Rempel, M.;
Dikpati, M.
Bibcode: 2017AGUFMSH22B..06M
Altcode:
The abrupt end of solar activity cycles 22 and 23 at the Sun's
equator are observed with instruments from the Solar and Heliospheric
Observatory (SOHO), Solar Terrestrial Relations Observatory (STEREO),
and Solar Dynamics Observatory (SDO). These events are remarkable in
that they rapidly trigger the onset of magnetic activity belonging
to the next solar cycle at mid-latitudes. The triggered onset of new
cycle flux emergence leads to blossoming of the new cycle shortly
thereafter. Using small-scale tracers of magnetic solar activity we
examine the timing of the cycle ``termination points'' in relation
to the excitation of new activity and find that the time taken
for the solar plasma to communicate this transition is less than
one solar rotation, and possibly as little as a eight days. This
very short transition time implies that the mean magnetic field
present in the Sun's convection zone is approximately 80 kG. This
value may be considerably larger than conventional explorations
estimate and therefore, have a significant dynamical impact on the
physical appearance of solar activity, and considerably impacting
our ability to perform first-principles numerical simulations of the
same. Should solar cycle 24 [and 25] continue in their progression
we anticipate that a termination event of this type should occur in
the 2020 timeframe. PSP will have a front row seat to observe this
systemic flip in solar magnetism and the induced changes in our star's
radiative and partiuculate output. Such observations may prove to be
critical in assessing the Sun's ability to force short term evolution
in the Earth's atmosphere.
Title: Multi-wavelength observations of the solar atmosphere from
the August 21, 2017 total solar eclipse
Authors: Tomczyk, S.; Boll, A.; Bryans, P.; Burkepile, J.; Casini,
R.; DeLuca, E.; Gibson, K. L.; Judge, P. G.; McIntosh, S. W.; Samra,
J.; Sewell, S. D.
Bibcode: 2017AGUFMSH24A..04T
Altcode:
We will conduct three experiments at the August 21, 2017 total
solar eclipse that we call the Rosetta Stone experiments. First,
we will obtain narrow-bandpass images at infrared wavelengths of the
magnetically sensitive coronal emission lines of Fe IX 2855 nm, Mg VIII
3028 nm and Si IX 3935 nm with a FLIR thermal imager. Information on the
brightness of these lines is important for identifying the optimal lines
for coronal magnetometry. These images will also serve as context images
for the airborne AirSpec IR coronal spectroscopy experiment (Samra et
al). Second, we will obtain linear polarization images of the visible
emission lines of Fe X 637 nm and Fe XI 789 nm as well as the continuum
polarization near 735 nm. These will be obtained with a novel detector
with an integral array of linear micro-polarizers oriented at four
different angles that enable polarization images without the need for
liquid crystals or rotating elements. These measurements will provide
information on the orientation of magnetic fields in the corona and
serve to demonstrate the new detector technology. Lastly, we will obtain
high cadence spectra as the moon covers and uncovers the chromosphere
immediately after 2nd contact and before third contact. This so-called
flash spectrum will be used to obtain information about chromospheric
structure at a spatial resolution higher than is possible by other
means. In this talk, we will describe the instrumentation used in these
experiments and present initial results obtained with them. This work
is supported by a grant from NASA, through NSF base funding of HAO/NCAR
and by generous loans of equipment from our corporate partners, FLIR,
4D Technologies and Avantes.
Title: Observations and Modeling of Transition Region and Coronal
Heating Associated with Spicules
Authors: De Pontieu, B.; Martinez-Sykora, J.; De Moortel, I.;
Chintzoglou, G.; McIntosh, S. W.
Bibcode: 2017AGUFMSH43A2793D
Altcode:
Spicules have been proposed as significant contributorsto the coronal
energy and mass balance. While previous observationshave provided
a glimpse of short-lived transient brightenings in thecorona that
are associated with spicules, these observations have beencontested
and are the subject of a vigorous debate both on the modelingand
the observational side so that it remains unclear whether plasmais
heated to coronal temperatures in association with spicules. We use
high-resolution observations of the chromosphere and transition region
with the Interface Region Imaging Spectrograph (IRIS) and ofthe corona
with the Atmospheric Imaging Assembly (AIA) onboard theSolar Dynamics
Observatory (SDO) to show evidence of the formation of coronal
structures as a result of spicular mass ejections andheating of
plasma to transition region and coronaltemperatures. Our observations
suggest that a significant fraction of the highly dynamic loop fan
environment associated with plage regions may be the result of the
formation of such new coronal strands, a process that previously had
been interpreted as the propagation of transient propagating coronal
disturbances (PCD)s. Our observationsare supported by 2.5D radiative
MHD simulations that show heating tocoronal temperatures in association
with spicules. Our results suggest that heating and strong flows play
an important role in maintaining the substructure of loop fans, in
addition to the waves that permeate this low coronal environment. Our
models also matches observations ofTR counterparts of spicules and
provides an elegant explanation forthe high apparent speeds of these
"network jets".
Title: ASPIRE - Airborne Spectro-Polarization InfraRed Experiment
Authors: DeLuca, E.; Cheimets, P.; Golub, L.; Madsen, C. A.; Marquez,
V.; Bryans, P.; Judge, P. G.; Lussier, L.; McIntosh, S. W.; Tomczyk, S.
Bibcode: 2017AGUFMSH13B2480D
Altcode:
Direct measurements of coronal magnetic fields are critical for
taking the next step in active region and solar wind modeling and
for building the next generation of physics-based space-weather
models. We are proposing a new airborne instrument to make these key
observations. Building on the successful Airborne InfraRed Spectrograph
(AIR-Spec) experiment for the 2017 eclipse, we will design and build a
spectro-polarimeter to measure coronal magnetic field during the 2019
South Pacific eclipse. The new instrument will use the AIR-Spec optical
bench and the proven pointing, tracking, and stabilization optics. A new
cryogenic spectro-polarimeter will be built focusing on the strongest
emission lines observed during the eclipse. The AIR-Spec IR camera,
slit jaw camera and data acquisition system will all be reused. The
poster will outline the optical design and the science goals for ASPIRE.
Title: Does the Sun Have A Polar Dynamo?
Authors: McIntosh, S. W.
Bibcode: 2017AGUFMSH11C..02M
Altcode:
Why do the "polar predictor" methods of solar cycle prediction appear
to work so well? It seems like there is a semi-empirical replationship
between the polar magnetic field at preceding solar minimum and the
strength of the upcoming cycle in each hemisphere. This relationship
seems to perform better, statistically, than kinematic dynamo models
or full 3D MHD models that cycle but don't propagate, or propagate but
don't cycle. In this retrospective session we'll look at polar magnetic
observations and a whole host of other synoptic-scale observations
that provide a physical underpinning to the idea that we have been
looking under the wrong conceptual lamp-post for the solar dynamo for
a long time and that the dynamo action itself takes place at high and
not mid-latitudes.
Title: Predicting the La Niña of 2020-21: Termination of Solar
Cycles and Correlated Variance in Solar and Atmospheric Variability
Authors: Leamon, R. J.; McIntosh, S. W.
Bibcode: 2017AGUFMSH42A..05L
Altcode:
Establishing a solid physical connection between solar and tropospheric
variability has posed a considerable challenge across the spectrum
of Earth-system science. Over the past few years a new picture
to describe solar variability has developed, based on observing,
understanding and tracing the progression, interaction and intrinsic
variability of the magnetized activity bands that belong to the Sun's
22-year magnetic activity cycle. The intra- and extra-hemispheric
interaction of these magnetic bands appear to explain the occurrence
of decadal scale variability that primarily manifests itself in the
sunspot cycle. However, on timescales of ten months or so, those bands
posses their own internal variability with an amplitude of the same
order of magnitude as the decadal scale. The latter have been tied to
the existence of magnetized Rossby waves in the solar convection zone
that result in surges of magnetic flux emergence that correspondingly
modulate our star's radiative and particulate output. One of the most
important events in the progression of these bands is their (apparent)
termination at the solar equator that signals a global increase in
magnetic flux emergence that becomes the new solar cycle. We look at
the particulate and radiative implications of these termination points,
their temporal recurrence and signature, from the Sun to the Earth,
and show the correlated signature of solar cycle termination events and
major oceanic oscillations that extend back many decades. A combined
one-two punch of reduced particulate forcing and increased radiative
forcing that result from the termination of one solar cycle and rapid
blossoming of another correlates strongly with a shift from El Niño to
La Niña conditions in the Pacific Ocean. This shift does not occur at
solar minima, nor solar maxima, but at a particular, non-periodic, time
in between. The failure to identify these termination points, and their
relative irregularity, have inhibited a correlation to be observed and
physical processes to be studied. This result potentially opens the door
to a broader understanding of solar variability on our planet and its
weather. Ongoing tracking of solar magnetic band migration indicates
that Cycle 24 will terminate in the 2020 timeframe and thus we may
expect to see an attendant shift to La Niña conditions at that time.
Title: The Origin of the "Seasons" in Space Weather
Authors: Dikpati, Mausumi; Cally, Paul S.; McIntosh, Scott W.;
Heifetz, Eyal
Bibcode: 2017NatSR...714750D
Altcode:
Powerful `space weather' events caused by solar activity pose
serious risks to human health, safety, economic activity and national
security. Spikes in deaths due to heart attacks, strokes and other
diseases occurred during prolonged power outages. Currently it is
hard to prepare for and mitigate the impact of space weather because
it is impossible to forecast the solar eruptions that can cause these
terrestrial events until they are seen on the Sun. However, as recently
reported in Nature, eruptive events like coronal mass ejections and
solar flares, are organized into quasi-periodic "seasons", which
include enhanced bursts of eruptions for several months, followed by
quiet periods. We explored the dynamics of sunspot-producing magnetic
fields and discovered for the first time that bursty and quiet
seasons, manifested in surface magnetic structures, can be caused by
quasi-periodic energy-exchange among magnetic fields, Rossby waves
and differential rotation of the solar interior shear-layer (called
tachocline). Our results for the first time provide a quantitative
physical mechanism for forecasting the strength and duration of
bursty seasons several months in advance, which can greatly enhance
our ability to warn humans about dangerous solar bursts and prevent
damage to satellites and power stations from space weather events.
Title: Realistic radiative MHD simulation of a solar flare
Authors: Rempel, Matthias D.; Cheung, Mark; Chintzoglou, Georgios;
Chen, Feng; Testa, Paola; Martinez-Sykora, Juan; Sainz Dalda, Alberto;
DeRosa, Marc L.; Viktorovna Malanushenko, Anna; Hansteen, Viggo H.;
De Pontieu, Bart; Carlsson, Mats; Gudiksen, Boris; McIntosh, Scott W.
Bibcode: 2017SPD....4840001R
Altcode:
We present a recently developed version of the MURaM radiative
MHD code that includes coronal physics in terms of optically thin
radiative loss and field aligned heat conduction. The code employs
the "Boris correction" (semi-relativistic MHD with a reduced speed
of light) and a hyperbolic treatment of heat conduction, which allow
for efficient simulations of the photosphere/corona system by avoiding
the severe time-step constraints arising from Alfven wave propagation
and heat conduction. We demonstrate that this approach can be used
even in dynamic phases such as a flare. We consider a setup in which
a flare is triggered by flux emergence into a pre-existing bipolar
active region. After the coronal energy release, efficient transport
of energy along field lines leads to the formation of flare ribbons
within seconds. In the flare ribbons we find downflows for temperatures
lower than ~5 MK and upflows at higher temperatures. The resulting
soft X-ray emission shows a fast rise and slow decay, reaching a peak
corresponding to a mid C-class flare. The post reconnection energy
release in the corona leads to average particle energies reaching 50
keV (500 MK under the assumption of a thermal plasma). We show that
hard X-ray emission from the corona computed under the assumption of
thermal bremsstrahlung can produce a power-law spectrum due to the
multi-thermal nature of the plasma. The electron energy flux into the
flare ribbons (classic heat conduction with free streaming limit) is
highly inhomogeneous and reaches peak values of about 3x1011
erg/cm2/s in a small fraction of the ribbons, indicating
regions that could potentially produce hard X-ray footpoint sources. We
demonstrate that these findings are robust by comparing simulations
computed with different values of the saturation heat flux as well as
the "reduced speed of light".
Title: Observations and Numerical Models of Solar Coronal Heating
Associated with Spicules
Authors: De Pontieu, B.; De Moortel, I.; Martinez-Sykora, J.; McIntosh,
S. W.
Bibcode: 2017ApJ...845L..18D
Altcode: 2017arXiv171006790D
Spicules have been proposed as significant contributors to the mass
and energy balance of the corona. While previous observations have
provided a glimpse of short-lived transient brightenings in the
corona that are associated with spicules, these observations have
been contested and are the subject of a vigorous debate both on the
modeling and the observational side. Therefore, it remains unclear
whether plasma is heated to coronal temperatures in association with
spicules. We use high-resolution observations of the chromosphere and
transition region (TR) with the Interface Region Imaging Spectrograph
and of the corona with the Atmospheric Imaging Assembly on board
the Solar Dynamics Observatory to show evidence of the formation
of coronal structures associated with spicular mass ejections and
heating of plasma to TR and coronal temperatures. Our observations
suggest that a significant fraction of the highly dynamic loop fan
environment associated with plage regions may be the result of the
formation of such new coronal strands, a process that previously had
been interpreted as the propagation of transient propagating coronal
disturbances. Our observations are supported by 2.5D radiative MHD
simulations that show heating to coronal temperatures in association
with spicules. Our results suggest that heating and strong flows
play an important role in maintaining the substructure of loop fans,
in addition to the waves that permeate this low coronal environment.
Title: North-South Asymmetry in Rieger-type Periodicity during Solar
Cycles 19-23
Authors: Gurgenashvili, Eka; Zaqarashvili, Teimuraz V.; Kukhianidze,
Vasil; Oliver, Ramon; Ballester, Jose Luis; Dikpati, Mausumi; McIntosh,
Scott W.
Bibcode: 2017ApJ...845..137G
Altcode: 2017arXiv170708615G
Rieger-type periodicity has been detected in different activity
indices over many solar cycles. It was recently shown that the
periodicity correlates with solar activity having a shorter period
during stronger cycles. Solar activity level is generally asymmetric
between northern and southern hemispheres, which could suggest the
presence of a similar behavior in the Rieger-type periodicity. We
analyze the sunspot area/number and the total magnetic flux data for
northern and southern hemispheres during solar cycles 19-23, which had
remarkable north-south asymmetry. Using wavelet analysis of sunspot
area and number during the north-dominated cycles (19-20), we obtained
the periodicity of 160-165 days in the stronger northern hemisphere
and 180-190 days in the weaker southern hemisphere. On the other hand,
south-dominated cycles (21-23) display the periodicity of 155-160 days
in the stronger southern hemisphere and 175-188 days in the weaker
northern hemisphere. Therefore, the Rieger-type periodicity has the
north-south asymmetry in sunspot area/number data during solar cycles
with strong hemispheric asymmetry. We suggest that the periodicity is
caused by magnetic Rossby waves in the internal dynamo layer. Using
the dispersion relation of magnetic Rossby waves and observed Rieger
periodicity, we estimated the magnetic field strength in the layer as
45-49 kG in more active hemispheres (north during cycles 19-20 and
south during cycles 21-23) and 33-40 kG in weaker hemispheres. The
estimated difference in the hemispheric field strength is around
10 kG, which provides a challenge for dynamo models. Total magnetic
flux data during cycles 20-23 reveals no clear north-south asymmetry,
which needs to be explained in the future.
Title: Deciphering Solar Magnetic Activity: Spotting Solar Cycle 25
Authors: McIntosh, Scott W.; Leamon, Robert J.
Bibcode: 2017FrASS...4....4M
Altcode: 2017arXiv170204414M
We present observational signatures of solar cycle 25 onset. Those
signatures are visibly following a migratory path from high to
low latitudes. They had starting points that are asymmetrically
offset in each hemisphere at times that are 21-22 years after the
corresponding, same polarity, activity bands of solar cycle 23 started
their migration. Those bands define the so-called "extended solar
cycle." The four magnetic bands currently present in the system are
approaching a mutually cancelling configuration, and solar minimum
conditions are imminent. Further, using a tuned analysis of the daily
band latitude-time diagnostics, we are able to utilize the longitudinal
wave number (m=1) variation in the data to more clearly reveal the
presence of the solar cycle 25 bands. This clarification illustrates
that prevalently active longitudes (different in each hemisphere) exist
at mid-latitudes presently, lasting many solar rotations, that can be
used for detailed study over the next several years with instruments
like the Spectrograph on IRIS, the Spectropolarimeter on Hinode, and,
when they come online, similar instruments on the Daniel K. Inouye
Solar Telescope (DKIST) as we watch those bands evolve following the
cancellation of the solar cycle 24 activity bands at the equator late
in 2019.
Title: The detection of Rossby-like waves on the Sun
Authors: McIntosh, Scott W.; Cramer, William J.; Pichardo Marcano,
Manuel; Leamon, Robert J.
Bibcode: 2017NatAs...1E..86M
Altcode:
Rossby waves are a type of global-scale wave that develops in planetary
atmospheres, driven by the planet's rotation1. They propagate
westward owing to the Coriolis force, and their characterization enables
more precise forecasting of weather on Earth2,3. Despite
the massive reservoir of rotational energy available in the Sun's
interior and decades of observational investigation, their solar
analogue defies unambiguous identification4-6. Here we
analyse a combined set of images obtained by the Solar TErrestrial
RElations Observatory (STEREO) and the Solar Dynamics Observatory (SDO)
spacecraft between 2011 and 2013 in order to follow the evolution
of small bright features, called brightpoints, which are tracers of
rotationally driven large-scale convection7. We report the
detection of persistent, global-scale bands of magnetized activity
on the Sun that slowly meander westward in longitude and display
Rossby-wave-like behaviour. These magnetized Rossby waves allow us to
make direct connections between decadal-scale solar activity and that
on much shorter timescales. Monitoring the properties of these waves,
and the wavenumber of the disturbances that they generate, has the
potential to yield a considerable improvement in forecast capability
for solar activity and related space weather phenomena.
Title: Magnetic and Energy Characteristics of Recurrent Homologous
Jets from an Emerging Flux
Authors: Liu, J.; Wang, Y.; Erdelyi, R.; Liu, R.; Mcintosh, S. W.;
Gou, T.; Chen, J.; Liu, K.; Liu, L.; Pan, Z.
Bibcode: 2016AGUFMSH12B..02L
Altcode:
We present the detailed analysis of recurrent homologous jets
originating from an emerging negative magnetic flux at the edge of an
Active Region. Detailed investigation of the related Poynting flux
across the photosphere employing the HMI vector magnetic field data
confirms the vital role of the emerging flux in accumulating the
necessary free magnetic energy for the associated reconnection to
initiate jets. The observed jets show multi-thermal features. Their
evolution shows high consistence with the characteristic parameters
of the emerging flux, suggesting that with more free magnetic energy,
the eruptions tend to be more violent, frequent and blowout-like. The
average temperature, average electron number density and axial speed
are found to be similar for different jets, indicating that they
should have been formed by plasmas from similar origins. Statistical
analysis of the jets and their footpoint region conditions reveals a
strong positive relationship between the footpoint region total 131 Å
intensity enhancement and jets' length/width. Stronger linearly positive
relationships also exist between the total intensity enhancement/thermal
energy of the footpoint regions and jets' mass/kinetic/thermal energy,
with higher cross-correlation coefficients. All the above results,
together, confirm the direct relationship between the magnetic
reconnection and the jets, and validate the important role of magnetic
reconnection in transporting large amount of free magnetic energy
into jets. It is also suggested that there should be more free energy
released during the magnetic reconnection of blowout than of standard
jet events.
Title: IRIS and SDO/AIA observations of coronal heating associated
with spicules
Authors: De Pontieu, B.; De Moortel, I.; Mcintosh, S. W.
Bibcode: 2016AGUFMSH42B..07D
Altcode:
Chromospheric spicules have been proposed as significant contributors
to the coronal energy and mass balance. While previous observations
have provided a glimpse of short-lived transient brightenings in
the corona that are associated with spicules, these observations
have been contested and the subject of a vigorous debate both on the
modeling and the observational side so that it remains unclear whether
plasma associated with spicules is heated to coronal temperatures. We
use high-resolution observations of the chromosphere and transition
region with the Interface Region Imaging Spectrograph (IRIS) and of
the corona with the Atmospheric Imaging Assembly (AIA) onboard the
Solar Dynamics Observatory (SDO) to show evidence of the formation of
coronal structures as a result of spicular mass ejections and subsequent
heating of plasma first to transition region and later to coronal
temperatures. Our observations suggest that much of the highly dynamic
loop fan environment associated with plage regions may be the result
of the formation of such new coronal strands, a process that previously
had been interpreted as the propagation of transient propagating coronal
disturbances (PCD)s. Our results suggest that heating and strong flows
play an important role in maintaining the substructure of loop fans,
in addition to the waves that permeate this low coronal environment.
Title: On the Magnetic and Energy Characteristics of Recurrent
Homologous Jets from An Emerging Flux
Authors: Liu, Jiajia; Wang, Yuming; Erdélyi, Robertus; Liu, Rui;
McIntosh, Scott W.; Gou, Tingyu; Chen, Jun; Liu, Kai; Liu, Lijuan;
Pan, Zonghao
Bibcode: 2016ApJ...833..150L
Altcode: 2016arXiv160807705L
In this paper, we present the detailed analysis of recurrent homologous
jets originating from an emerging negative magnetic flux at the edge of
an active region. The observed jets show multithermal features. Their
evolution shows high consistence with the characteristic parameters
of the emerging flux, suggesting that with more free magnetic energy,
the eruptions tend to be more violent, frequent, and blowout-like. The
average temperature, average electron number density, and axial speed
are found to be similar for different jets, indicating that they
should have been formed by plasmas from similar origins. Statistical
analysis of the jets and their footpoint region conditions reveals
a strong positive relationship between the footpoint region total
131 Å intensity enhancement and jets’ length/width. Stronger
linearly positive relationships also exist between the total
intensity enhancement/thermal energy of the footpoint regions and
jets’ mass/kinetic/thermal energy, with higher cross-correlation
coefficients. All the above results together confirm the direct
relationship between the magnetic reconnection and the jets and
validate the important role of magnetic reconnection in transporting
large amounts of free magnetic energy into jets. It is also suggested
that there should be more free energy released during the magnetic
reconnection of blowout than of standard jet events.
Title: The importance of high-resolution observations of the solar
corona
Authors: Winebarger, A. R.; Cirtain, J. W.; Golub, L.; Walsh, R. W.;
De Pontieu, B.; Savage, S. L.; Rachmeler, L.; Kobayashi, K.; Testa,
P.; Brooks, D.; Warren, H.; Mcintosh, S. W.; Peter, H.; Morton, R. J.;
Alexander, C. E.; Tiwari, S. K.
Bibcode: 2016AGUFMSH31B2577W
Altcode:
The spatial and temporal resolutions of the available coronal
observatories are inadequate to resolve the signatures of coronal
heating. High-resolution and high-cadence observations available with
the Interface Region Imaging Spectrograph (IRIS) and the High-resolution
Coronal Imager (Hi-C) instrument hint that 0.3 arcsec resolution images
and < 10 s cadence provide the necessary resolution to detect
heating events. Hi-C was launched from White Sands Missile Range on
July 11, 2012 (before the launch with IRIS) and obtained images of
a solar active region in the 19.3 nm passband. In this presentation,
I will discuss the potential of combining a flight in Hi-C with a 17.1
nm passband, in conjunction with IRIS. This combination will provide,
for the first time, a definitive method of tracing the energy flow
between the chromosphere and corona and vice versa.
Title: Driving the Heliospheric Jellyfish
Authors: Leamon, R. J.; Mcintosh, S. W.
Bibcode: 2016AGUFMSH31B2550L
Altcode:
Recent observational work has demonstrated that the enigmatic
sunspotcycle and global magnetic environment of the Sun which source
theeruptive events and modulate the solar wind, respectively,
can beexplained in terms of the intra- and extra-hemispheric
interaction ofmagnetic activity bands that belong to the 22-year
magnetic polaritycycle. Those activity bands appear to be anchored
deep in the Sun'sconvective interior and governed by the rotation of
our star's radiativezone. We have also observed that those magnetic
bands exhibit strongquasi-annual variability in the rotating convecting
system which resultsin a significant local modulation of solar surface
magnetism, forcingthe production of large eruptive events in each
hemisphere that mouldsthe global-scale solar magnetic field and the
solar-wind-inflatedheliosphere. Together with significant changes
in the Sun's ultraviolet(UV), extreme ultraviolet (EUV), and X-Ray
irradiance, these eruptivefluctuations ensnare all the Heliosphere
(all of Heliophysics) like thetentacles of a jellyfish, and can be
inferred in variations of suchwide-ranging phenomena as the South
Atlantic Anomaly, the thermosphere,the radiation belts, and the can
address ``Has Voyager left theHeliosphere?''
Title: Exploring Coronal Dynamics: A Next Generation Solar Physics
Mission white paper
Authors: Morton, R. J.; Scullion, E.; Bloomfield, D. S.; McLaughlin,
J. A.; Regnier, S.; McIntosh, S. W.; Tomczyk, S.; Young, P.
Bibcode: 2016arXiv161106149M
Altcode:
Determining the mechanisms responsible for the heating of the
coronal plasma and maintaining and accelerating the solar wind
are long standing goals in solar physics. There is a clear need to
constrain the energy, mass and momentum flux through the solar corona
and advance our knowledge of the physical process contributing to
these fluxes. Furthermore, the accurate forecasting of Space Weather
conditions at the near-Earth environment and, more generally, the
plasma conditions of the solar wind throughout the heliosphere, require
detailed knowledge of these fluxes in the near-Sun corona. Here we
present a short case for a space-based imaging-spectrometer coronagraph,
which will have the ability to provide synoptic information on the
coronal environment and provide strict constraints on the mass, energy,
and momentum flux through the corona. The instrument would ideally
achieve cadences of $\sim10$~s, spatial resolution of 1" and observe the
corona out to 2~$R_{\sun}$. Such an instrument will enable significant
progress in our understanding of MHD waves throughout complex plasmas,
as well as potentially providing routine data products to aid Space
Weather forecasting.
Title: On the Connection between Propagating Solar Coronal
Disturbances and Chromospheric Footpoints
Authors: Bryans, P.; McIntosh, S. W.; De Moortel, I.; De Pontieu, B.
Bibcode: 2016ApJ...829L..18B
Altcode:
The Interface Region Imaging Spectrograph (IRIS) provides an
unparalleled opportunity to explore the (thermal) interface between the
chromosphere, transition region, and the coronal plasma observed by the
Atmospheric Imaging Assembly (AIA) of the Solar Dynamics Observatory
(SDO). The SDO/AIA observations of coronal loop footpoints show
strong recurring upward propagating signals—“propagating coronal
disturbances” (PCDs) with apparent speeds of the order of 100-120 km
s-1. That signal has a clear signature in the slit-jaw images
of IRIS in addition to identifiable spectral signatures and diagnostics
in the Mg iih (2803 Å) line. In analyzing the Mg iih line, we are able
to observe the presence of magnetoacoustic shock waves that are also
present in the vicinity of the coronal loop footpoints. We see there is
enough of a correspondence between the shock propagation in Mg iih, the
evolution of the Si IV line profiles, and the PCD evolution to indicate
that these waves are an important ingredient for PCDs. In addition, the
strong flows in the jet-like features in the IRIS Si IV slit-jaw images
are also associated with PCDs, such that waves and flows both appear
to be contributing to the signals observed at the footpoints of PCDs.
Title: Scientific objectives and capabilities of the Coronal Solar
Magnetism Observatory
Authors: Tomczyk, S.; Landi, E.; Burkepile, J. T.; Casini, R.; DeLuca,
E. E.; Fan, Y.; Gibson, S. E.; Lin, H.; McIntosh, S. W.; Solomon,
S. C.; Toma, G.; Wijn, A. G.; Zhang, J.
Bibcode: 2016JGRA..121.7470T
Altcode:
Magnetic influences increase in importance in the solar atmosphere
from the photosphere out into the corona, yet our ability to routinely
measure magnetic fields in the outer solar atmosphere is lacking. We
describe the scientific objectives and capabilities of the COronal Solar
Magnetism Observatory (COSMO), a proposed synoptic facility designed
to measure magnetic fields and plasma properties in the large-scale
solar atmosphere. COSMO comprises a suite of three instruments chosen
to enable the study of the solar atmosphere as a coupled system: (1)
a coronagraph with a 1.5 m aperture to measure the magnetic field,
temperature, density, and dynamics of the corona; (2) an instrument
for diagnostics of chromospheric and prominence magnetic fields and
plasma properties; and (3) a white light K-coronagraph to measure
the density structure and dynamics of the corona and coronal mass
ejections. COSMO will provide a unique combination of magnetic field,
density, temperature, and velocity observations in the corona and
chromosphere that have the potential to transform our understanding
of fundamental physical processes in the solar atmosphere and their
role in the origins of solar variability and space weather.
Title: Physics & Diagnostics of the Drivers of Solar Eruptions
Authors: Cheung, Mark; Rempel, Matthias D.; Martinez-Sykora, Juan;
Testa, Paola; Hansteen, Viggo H.; Viktorovna Malanushenko, Anna;
Sainz Dalda, Alberto; DeRosa, Marc L.; De Pontieu, Bart; Carlsson,
Mats; Chen, Feng; McIntosh, Scott W.; Gudiksen, Boris
Bibcode: 2016SPD....47.0607C
Altcode:
We provide an update on our NASA Heliophysics Grand Challenges Research
(HGCR) project on the ‘Physics & Diagnostics of the Drivers of
Solar Eruptions’. This presentation will focus on results from a
data-inspired, 3D radiative MHD model of a solar flare. The model
flare results from the interaction of newly emerging flux with a
pre-existing active region. Synthetic observables from the model
reproduce observational features compatible with actual flares. These
include signatures of coronal magnetic reconnection, chromospheric
evaporation, EUV flare arcades, sweeping motion of flare ribbons
and sunquakes.
Title: On the Observation and Simulation of Solar Coronal Twin Jets
Authors: Liu, Jiajia; Fang, Fang; Wang, Yuming; McIntosh, Scott W.;
Fan, Yuhong; Zhang, Quanhao
Bibcode: 2016ApJ...817..126L
Altcode: 2016arXiv160807759L
We present the first observation, analysis, and modeling of solar
coronal twin jets, which occurred after a preceding jet. Detailed
analysis on the kinetics of the preceding jet reveals its blowout-jet
nature, which resembles the one studied in Liu et al. However, the
erupting process and kinetics of the twin jets appear to be different
from the preceding one. Lacking detailed information on the magnetic
fields in the twin jet region, we instead use a numerical simulation
using a three-dimensional (3D) MHD model as described in Fang et
al., and find that in the simulation a pair of twin jets form due
to reconnection between the ambient open fields and a highly twisted
sigmoidal magnetic flux, which is the outcome of the further evolution
of the magnetic fields following the preceding blowout jet. Based
on the similarity between the synthesized and observed emission,
we propose this mechanism as a possible explanation for the observed
twin jets. Combining our observation and simulation, we suggest that
with continuous energy transport from the subsurface convection zone
into the corona, solar coronal twin jets could be generated in the
same fashion addressed above.
Title: Waves and Magnetism in the Solar Atmosphere (WAMIS)
Authors: Ko, Yuan-Kuen; Moses, John; Laming, John; Strachan, Leonard;
Tun Beltran, Samuel; Tomczyk, Steven; Gibson, Sarah; Auchere, Frederic;
Casini, Roberto; Fineschi, Silvano; Knoelker, Michael; Korendyke,
Clarence; McIntosh, Scott; Romoli, Marco; Rybak, Jan; Socker, Dennis;
Vourlidas, Angelos; Wu, Qian
Bibcode: 2016FrASS...3....1K
Altcode:
Comprehensive measurements of magnetic fields in the solar corona have
a long history as an important scientific goal. Besides being crucial
to understanding coronal structures and the Sun’s generation of space
weather, direct measurements of their strength and direction are also
crucial steps in understanding observed wave motions. In this regard,
the remote sensing instrumentation used to make coronal magnetic field
measurements is well suited to measuring the Doppler signature of waves
in the solar structures. In this paper, we describe the design and
scientific values of the Waves and Magnetism in the Solar Atmosphere
(WAMIS) investigation. WAMIS, taking advantage of greatly improved
infrared filters and detectors, forward models, advanced diagnostic
tools and inversion codes, is a long-duration high-altitude balloon
payload designed to obtain a breakthrough in the measurement of
coronal magnetic fields and in advancing the understanding of the
interaction of these fields with space plasmas. It consists of a 20 cm
aperture coronagraph with a visible-IR spectro-polarimeter focal plane
assembly. The balloon altitude would provide minimum sky background and
atmospheric scattering at the wavelengths in which these observations
are made. It would also enable continuous measurements of the strength
and direction of coronal magnetic fields without interruptions from
the day-night cycle and weather. These measurements will be made
over a large field-of-view allowing one to distinguish the magnetic
signatures of different coronal structures, and at the spatial and
temporal resolutions required to address outstanding problems in
coronal physics. Additionally, WAMIS could obtain near simultaneous
observations of the electron scattered K-corona for context and to
obtain the electron density. These comprehensive observations are not
provided by any current single ground-based or space observatory. The
fundamental advancements achieved by the near-space observations of
WAMIS on coronal field would point the way for future ground based
and orbital instrumentation.
Title: Modified Rossby Waves in the Solar Interior: The Need For A
Solar Meteorology Mission
Authors: Mcintosh, S. W.
Bibcode: 2015AGUFMSH33D..04M
Altcode:
Using a combination of STEREO/SECCHI/EUVI and SDO/AIA imaging we reveal
patterns in the imaging data that are consistent in appearance with
global scale rotationally driven waves on the activity bands of the
solar magnetic polarity cycle. These observations point to new insight
into the root causes of space weather and motivate a new multi-viewpoint
study of the entire solar atmosphere.
Title: On the Observation and Simulation of Solar Coronal Twin Jets
Authors: Liu, J.; Fang, F.; Wang, Y.; Mcintosh, S. W.; Fan, Y.;
Zhang, Q.
Bibcode: 2015AGUFMSH31B2405L
Altcode:
We present the first observation, analysis and modeling on solar coronal
twin jets, which occurred after a preceding jet. Detailed analysis
on the kinetics of the preceding jet reveals its blowout-jet nature,
which resembles the study by Liu et al. 2014. However the erupting
process and kinetics of the twin jets appear to be different from
the preceding one. To address the triggering mechanism of the twins,
we continue the 3D MHD numerical simulation work in Fang et al. 2014
after the eruption of a blowout jet. Numerical simulation shows that
the resulting sigmoidal magnetic fields after the blowout jet keep
reconnecting with the ambient fields, producing the observed twin
jets. Combining our observation and simulation, we suggest that with
the continuous energy transport from the subsurface convection zone into
the corona, solar coronal twin jets could be generated by reconnection
between a sigmoidal magnetic structure and the open ambient fields.
Title: Space Weather Observaitons @ HAO : Past, Present and Future
Authors: Mcintosh, S. W.
Bibcode: 2015AGUFMSM41B2484M
Altcode:
In 2015 the High Altitude Observatory (HAO) celbrates its 75th
anniversary. From the early years of the observatory at Cimax Pass to
the current facility at the Mauna Loa Solar Observatory [MLSO] we will
highlight the techniques and methodologies developed to monitor solar
actiity and its evolition. In the coming years we hope to develop
a new community facility - COSMO - to push space weather montioring
into the data assimilation age. We will provide an overview of the
requirements and capbiliites of the COSMO facility.
Title: Observed Variability of the Solar Mg II h Spectral Line
Authors: Schmit, D.; Bryans, P.; De Pontieu, B.; McIntosh, S.;
Leenaarts, J.; Carlsson, M.
Bibcode: 2015ApJ...811..127S
Altcode: 2015arXiv150804714S
The Mg ii h&k doublet are two of the primary spectral lines observed
by the Sun-pointing Interface Region Imaging Spectrograph (IRIS). These
lines are tracers of the magnetic and thermal environment that spans
from the photosphere to the upper chromosphere. We use a double-Gaussian
model to fit the Mg ii h profile for a full-Sun mosaic data set taken
on 2014 August 24. We use the ensemble of high-quality profile fits to
conduct a statistical study on the variability of the line profile as
it relates the magnetic structure, dynamics, and center-to-limb viewing
angle. The average internetwork profile contains a deeply reversed
core and is weakly asymmetric at h2. In the internetwork, we find a
strong correlation between h3 wavelength and profile asymmetry as well
as h1 width and h2 width. The average reversal depth of the h3 core
is inversely related to the magnetic field. Plage and sunspots exhibit
many profiles that do not contain a reversal. These profiles also occur
infrequently in the internetwork. We see indications of magnetically
aligned structures in plage and network in statistics associated with
the line core, but these structures are not clear or extended in the
internetwork. The center-to-limb variations are compared to predictions
of semi-empirical model atmospheres. We measure a pronounced limb
darkening in the line core that is not predicted by the model. The
aim of this work is to provide a comprehensive measurement baseline
and preliminary analysis on the observed structure and formation of
the Mg ii profiles observed by IRIS.
Title: Waves and Magnetism in the Solar Atmosphere (WAMIS)
Authors: Strachan, L.; Ko, Y. -K.; Moses, J. D.; Laming, J. M.;
Auchere, F.; Casini, R.; Fineschi, S.; Gibson, S.; Knoelker, M.;
Korendyke, C.; Mcintosh, S.; Romoli, M.; Rybak, J.; Socker, D.;
Tomczyk, S.; Vourlidas, A.; Wu, Q.
Bibcode: 2015IAUS..305..121S
Altcode:
Magnetic fields in the solar atmosphere provide the energy for most
varieties of solar activity, including high-energy electromagnetic
radiation, solar energetic particles, flares, and coronal mass
ejections, as well as powering the solar wind. Despite the fundamental
role of magnetic fields in solar and heliospheric physics, there
exist only very limited measurements of the field above the base of
the corona. What is needed are direct measurements of not only the
strength and orientation of the magnetic field but also the signatures
of wave motions in order to better understand coronal structure, solar
activity, and the role of MHD waves in heating and accelerating the
solar wind. Fortunately, the remote sensing instrumentation used to make
magnetic field measurements is also well suited to measure the Doppler
signature of waves in the solar structures. We present here a mission
concept for the Waves And Magnetism In the Solar Atmosphere (WAMIS)
experiment which is proposed for a NASA long-duration balloon flight.
Title: The Standardisation and Sequencing of Solar Eclipse Images
for the Eclipse Megamovie Project
Authors: Krista, Larisza D.; McIntosh, Scott W.
Bibcode: 2015SoPh..290.2381K
Altcode: 2015SoPh..tmp..110K; 2015arXiv151008941K
We present a new tool, the Solar Eclipse Image Standardisation and
Sequencing (SEISS), developed to process multi-source total solar
eclipse images by adjusting them to the same standard of size,
resolution, and orientation. Furthermore, by analysing the eclipse
images, we can determine the relative time between the observations
and order them to create a movie of the observed total solar eclipse
sequence. We successfully processed images taken at the 14 November
2012 total solar eclipse that occurred in Queensland, Australia, and
created a short eclipse proto-movie. The SEISS tool was developed
for the Eclipse Megamovie Project (EMP: www.eclipsemegamovie.org),
with the goal of processing thousands of images taken by the public
during solar eclipse events. EMP is a collaboration among multiple
institutes aiming to engage and advance the public interest in solar
eclipses and the science of the Sun-Earth connection.
Title: Deciphering Solar Magnetic Activity: On Grand Minima in
Solar Activity
Authors: Mcintosh, Scott; Leamon, Robert
Bibcode: 2015FrASS...2....2M
Altcode: 2015arXiv150502326M
The Sun provides the energy necessary to sustain our existence. While
the Sun provides for us, it is also capable of taking away. The weather
and climatic scales of solar evolution and the Sun-Earth connection are
not well understood. There has been tremendous progress in the century
since the discovery of solar magnetism - magnetism that ultimately
drives the electromagnetic, particulate and eruptive forcing of our
planetary system. There is contemporary evidence of a decrease in solar
magnetism, perhaps even indicators of a significant downward trend,
over recent decades. Are we entering a minimum in solar activity that is
deeper and longer than a typical solar minimum, a "grand minimum"? How
could we tell if we are? What is a grand minimum and how does the Sun
recover? These are very pertinent questions for modern civilization. In
this paper we present a hypothetical demonstration of entry and exit
from grand minimum conditions based on a recent analysis of solar
features over the past 20 years and their possible connection to the
origins of the 11(-ish) year solar activity cycle.
Title: On the Parallel and Perpendicular Propagating Motions Visible
inPolar Plumes: An Incubator For (Fast) Solar Wind Acceleration?
Authors: Liu, Jiajia; McIntosh, Scott W.; De Moortel, Ineke; Wang,
Yuming
Bibcode: 2015ApJ...806..273L
Altcode: 2015arXiv150700143L
We combine observations of the Coronal Multi-channel Polarimeter and the
Atmospheric Imaging Assembly on board the Solar Dynamics Observatory
to study the characteristic properties of (propagating) Alfvénic
motions and quasi-periodic intensity disturbances in polar plumes. This
unique combination of instruments highlights the physical richness of
the processes taking place at the base of the (fast) solar wind. The
(parallel) intensity perturbations with intensity enhancements around
1% have an apparent speed of 120 km s-1 (in both the 171
and 193 Å passbands) and a periodicity of 15 minutes, while the
(perpendicular) Alfvénic wave motions have a velocity amplitude
of 0.5 km s-1, a phase speed of 830 km s-1,
and a shorter period of 5 minutes on the same structures. These
observations illustrate a scenario where the excited Alfvénic
motions are propagating along an inhomogeneously loaded magnetic field
structure such that the combination could be a potential progenitor
of the magnetohydrodynamic turbulence required to accelerate the fast
solar wind.
Title: The Quasi-Annual Forcing of The Sun’s Eruptive, Radiative,
and Particulate Output: Pervasive Throughout The Heliosphere
Authors: Leamon, Robert J.; McIntosh, Scott W.
Bibcode: 2015TESS....130806L
Altcode:
The eruptive, radiative, and particulate output of the Sun are modulated
by our star’s enigmatic 11-year sunspot cycle. Over the past year
we have identified observational signatures which illustrate the ebb
and flow of the 11-year cycle - arising from the temporal overlap of
migrating activity bands which belong to the 22-year magnetic activity
cycle. (At the 2012 Fall AGU Meeting, Leamon & McIntosh presented
a prediction of minimum conditions developing in 2017 and Cycle 25
sunspots first appearing in late 2019.) As a consequence of this work we
have deduced that the latitudinal interaction of the oppositely signed
magnetic activity bands in each hemisphere (and across the equator near
solar minimum) dramatically impacts the production of Space Weather
events such as flares and Coronal Mass Ejections (CMEs). The same set
of observations also permits us to identify a quasi-annual variability
in the rotating convecting system which results in a significant local
modulation of solar surface magnetism. That modulation, in turn, forces
prolonged periods of significantly increased flare and CME production,
as well as significant changes in the Sun's ultraviolet (UV), extreme
ultraviolet (EUV), and X-Ray irradiance. These fluctuations manifest
themselves throughout the Heliosphere (throughout Heliophysics)
and can be inferred in variations of such wide-ranging phenomena as
the South Atlantic Anomaly, the thermosphere, the radiation belts,
and the can address "Has Voyager left the Heliosphere?"
Title: Modified Rossby Waves in the Solar Interior
Authors: McIntosh, Scott W.; Title, Alan M.; Leamon, Robert J.
Bibcode: 2015TESS....110501M
Altcode:
Using a combination of STEREO/SECCHI/EUVI and SDO/AIA imaging we reveal
patterns in the imaging data that are consistent in appearance with
global scale rotationally driven waves on the activity bands of the
solar magnetic polarity cycle.
Title: The solar magnetic activity band interaction and instabilities
that shape quasi-periodic variability
Authors: McIntosh, Scott W.; Leamon, Robert J.; Krista, Larisza D.;
Title, Alan M.; Hudson, Hugh S.; Riley, Pete; Harder, Jerald W.; Kopp,
Greg; Snow, Martin; Woods, Thomas N.; Kasper, Justin C.; Stevens,
Michael L.; Ulrich, Roger K.
Bibcode: 2015NatCo...6.6491M
Altcode: 2015NatCo...6E6491M
Solar magnetism displays a host of variational timescales of which
the enigmatic 11-year sunspot cycle is most prominent. Recent work
has demonstrated that the sunspot cycle can be explained in terms of
the intra- and extra-hemispheric interaction between the overlapping
activity bands of the 22-year magnetic polarity cycle. Those
activity bands appear to be driven by the rotation of the Sun's
deep interior. Here we deduce that activity band interaction can
qualitatively explain the `Gnevyshev Gap'--a well-established feature
of flare and sunspot occurrence. Strong quasi-annual variability in the
number of flares, coronal mass ejections, the radiative and particulate
environment of the heliosphere is also observed. We infer that this
secondary variability is driven by surges of magnetism from the activity
bands. Understanding the formation, interaction and instability of
these activity bands will considerably improve forecast capability in
space weather and solar activity over a range of timescales.
Title: Full-Sun IRIS observations and what they reveal about
chromosphere and transition region variation across the disk
Authors: Bryans, Paul; McIntosh, Scott W.
Bibcode: 2015TESS....120313B
Altcode:
The recent launch of the Interface Region Imaging Spectrometer
(IRIS) has resulted in the first high-resolution spectroscopy of the
chromosphere and transition region. The wavelength range sampled by IRIS
allows us to measure emission and absorption lines across a range of
heights in the lower solar atmosphere. However, the IRIS field-of-view
is limited to 175 arcsec2, so simultaneous observations of
these spectral lines is not possible across the entire disk. To overcome
this problem we have performed full-disk mosaics, where we build up
observations of the entire Sun using 184 different IRIS pointings. An
analysis of these mosaics has highlighted interesting variations in
the spectral line profiles across the disk. In this presentation we
will summarize these findings and speculate on what physical insights
they reveal.
Title: Why is Non-Thermal Line Broadening of Spectral Lines in the
Lower Transition Region of the Sun Independent of Spatial Resolution?
Authors: De Pontieu, B.; McIntosh, S.; Martinez-Sykora, J.; Peter,
H.; Pereira, T. M. D.
Bibcode: 2015ApJ...799L..12D
Altcode: 2017arXiv171006807D
Spectral observations of the solar transition region (TR) and
corona show broadening of spectral lines beyond what is expected
from thermal and instrumental broadening. The remaining non-thermal
broadening is significant (5-30 km s-1) and correlated with
intensity. Here we study spectra of the TR Si iv 1403 Å line obtained
at high resolution with the Interface Region Imaging Spectrograph
(IRIS). We find that the large improvement in spatial resolution
(0.″33) of IRIS compared to previous spectrographs (2″) does
not resolve the non-thermal line broadening which, in most regions,
remains at pre-IRIS levels of about 20 km s-1. This
invariance to spatial resolution indicates that the processes behind
the broadening occur along the line-of-sight (LOS) and/or on spatial
scales (perpendicular to the LOS) smaller than 250 km. Both effects
appear to play a role. Comparison with IRIS chromospheric observations
shows that, in regions where the LOS is more parallel to the field,
magneto-acoustic shocks driven from below impact the TR and can lead
to significant non-thermal line broadening. This scenario is supported
by MHD simulations. While these do not show enough non-thermal line
broadening, they do reproduce the long-known puzzling correlation
between non-thermal line broadening and intensity. This correlation
is caused by the shocks, but only if non-equilibrium ionization is
taken into account. In regions where the LOS is more perpendicular
to the field, the prevalence of small-scale twist is likely to play
a significant role in explaining the invariance and correlation with
intensity.
Title: Grand Minima: Is The Sun Going To Sleep?
Authors: Mcintosh, S. W.; Leamon, R. J.
Bibcode: 2014AGUFMSH21C4128M
Altcode:
We explore recent observational work which indicate that the energetics
of the sun's outer atmosphere have been on a steady decline for the past
decade and perhaps longer. Futher, we show that new investigations into
evolution of the Sun's global magnetic activity appear to demonstrate a
path through which the Sun can go into, and exit from, a grand activity
minimum without great difficulty while retaining an activity cycle -
only losing sunspots. Are we at the begining of a new grand(-ish)
minimum? Naturally, only time will tell, but the observational
evidence hint that one may not be far off to what impact on the
Sun-Earth Connection.
Title: The solar cycle dependence of the weak internetwork flux
Authors: Lites, Bruce W.; Centeno, Rebecca; McIntosh, Scott W.
Bibcode: 2014PASJ...66S...4L
Altcode: 2014PASJ..tmp..109L
We examine data from the Hinode Observing Program 79 (the "HOP 79"
irradiance program) as observed using the Hinode Solar Optical
Telescope Spectro-Polarimeter for systematic changes in the weakest
observable magnetic flux during the period 2008-2013. At moderate
latitudes we find no evidence for systematic changes as a function
of time and solar latitude in either the unsigned line-of-sight flux
or in the measures of the transverse flux. However, in the polar
regions, changes are apparent in the measure of signed magnetic flux
corresponding to reversal of the polarity of the poles, changes that
persist even for the weakest observed flux. Also evident in measures
of the weakest signed flux are preferences for positive (negative)
polarity at mid-north (mid-south) latitudes (20°-60°). Center-limb
variations in various measures of the weak flux appear to be independent
of the solar cycle. The results are consistent with the operation of
a small-scale solar dynamo operating within and just below the solar
photosphere, but the measures of the weakest signed flux still contain
small signatures of the global solar cycle.
Title: Statistical Evidence for the Existence of Alfvénic Turbulence
in Solar Coronal Loops
Authors: Liu, Jiajia; McIntosh, Scott W.; De Moortel, Ineke; Threlfall,
James; Bethge, Christian
Bibcode: 2014ApJ...797....7L
Altcode: 2014arXiv1411.5094L
Recent observations have demonstrated that waves capable of
carrying large amounts of energy are ubiquitous throughout the solar
corona. However, the question of how this wave energy is dissipated
(on which timescales and length scales) and released into the plasma
remains largely unanswered. Both analytic and numerical models have
previously shown that Alfvénic turbulence may play a key role not
only in the generation of the fast solar wind, but in the heating
of coronal loops. In an effort to bridge the gap between theory and
observations, we expand on a recent study by analyzing 37 clearly
isolated coronal loops using data from the Coronal Multi-channel
Polarimeter instrument. We observe Alfvénic perturbations with phase
speeds which range from 250 to 750 km s-1 and periods from
140 to 270 s for the chosen loops. While excesses of high-frequency wave
power are observed near the apex of some loops (tentatively supporting
the onset of Alfvénic turbulence), we show that this excess depends on
loop length and the wavelength of the observed oscillations. In deriving
a proportional relationship between the loop length/wavelength ratio
and the enhanced wave power at the loop apex, and from the analysis
of the line widths associated with these loops, our findings are
supportive of the existence of Alfvénic turbulence in coronal loops.
Title: Computer Vision: Discovery And Opportunity Await
Authors: Mcintosh, S. W.
Bibcode: 2014AGUFMSH34A..03M
Altcode:
Current solar image archives contain information, lots of information,
often so much information that "end-point science" is not immediately
clear at the start of a project to survey them. However, in such
datasets and their metadata, significant scientific could be hidden
just a few queries below the surface. We will discuss quite possibly
the largest astronomical database, the "EUV Brightpoint Database",
which contains information about over 200 million individual features
that are ubiquitously observed in the Sun's corona - EUV Brightpoints
(or BPs). While end-point science was not clear in 2002 when the project
to catalog the Sun's BPs in the archive of SOHO's Extreme Ultraviolet
Telescope (EIT) images began the impact of those few queries could
cause a quite a stir in the field. Our systematic analysis of BPs,
and the magnetic scale on which they appear to form, allowed us to
demonstrate that the landmarks of sunspot cycle 23 could be explained in
terms of the evolution and interaction of latitudinally and temporally
overlapping bands of magnetic activity. Those bands appear to belong
to the Sun's 22-year magnetic activity cycle. The patterns that these
bands make closely match helioseismic inference of the Sun's torsional
oscillation - a signature of rotational anomalies taking place the Sun's
interior. The high-latitude origin and start dates preceding sunspot
formation by more than a decade - on the same activity band - pose a
significant challenge to our understanding of the processes responsible
for the production of the Sun's quasi-decadal variability. We sincerely
doubt that the BP database is alone in containing information of such
potential scientific value. Often one just has to get lucky, before
being able to formulate the correct queries. We hope that the material
presented in this talk can motivate a scientific exploitation of the
computer vision databases currently being built from the stunning
images of our star in addition to some retrospective investigations.
Title: A catalog of Dimming Regions from the SDO AIA mission
Authors: Davey, A. R.; Mcintosh, S. W.
Bibcode: 2014AGUFMSH21A4086D
Altcode:
Created as part of the SDO Feature Finding Team's (FFT) work, the
DimmingRegion Module has been running automatically at SAO on processed
Level 1.5AIA 193 A data. It has also been run retroactively over a
large percentageof the the previous data from the mission. A database
of the dimming regionsand their associated properties will shortly
be available, linking dimmingregion detections, output from the FFT
flare detective module and theability to access the data used directly
via the VSO.(http://helio.cfa.harvard.edu/FFT/modules/dimmings/). Does
this databaseprovide anything more than catalog pointing to events that
the user may beinterested in downloading and studying? We examine the
possible scientificpotential from the current database. We look at
the effects of theassumptions used to create an autonomous dimming
regions detection module,such as reduced cadence and resolution,
and smoothing. We do this bycomparing to sample events run at full
cadence and resolution. We considerwhat effect other choices such
as minimum dimming size and dimming depthhave on scientific value
of the database. Although the module detects alldimmings types,
including Thermal Dimmings, Rotation and EvolutionArtifacts, it is
Eruptive Dimmings which are the events of real interest.Unfortunately
differentiating these dimming types automatically is one ofthe
many challenges that still exist to creating a fully automated
dimmingregions module, one that would be more effective in Space
Weather Warningscenarios
Title: Coronal Eruptions in Simulations of Magnetic Flux Emergence
from the Convection Zone
Authors: Fang, F.; Fan, Y.; Mcintosh, S. W.
Bibcode: 2014AGUFMSH44A..06F
Altcode:
Solar magnetic fields permeate various layers of the Sun from the
interior to the corona and interact with the local plasma. The physical
properties of the plasma vary drastically from the convection zone
to the corona, with a density drop of 14 orders of magnitude. The
interaction between the plasma and magnetic fields strongly distort
the field structure during the emergence. The emerged fields dominate
the dynamics in the corona and may drive magnetic eruptions, with
significant release of magnetic energy into thermal and kinetic energy
of the plasma. Here we present numerical simulations of flux emergence
into pre-existing fields in a coupled convection-zone-corona system,
and study the resulting eruption of the magnetic fields in the corona,
e.g. blowout jets. Analysis of the simulation results illustrates
how the mass and energy is transferred from the interior into outer
atmosphere during the eruptions. Comparison with modern observations
provides us a physical understanding of the observed coronal eruptions
in flux emerging regions.
Title: Waves and Magnetism in the Solar Atmosphere (WAMIS)
Authors: Ko, Y. K.; Auchere, F.; Casini, R.; Fineschi, S.; Gibson,
S. E.; Knoelker, M.; Korendyke, C.; Laming, J. M.; Mcintosh, S. W.;
Moses, J. D.; Romoli, M.; Rybak, J.; Socker, D. G.; Strachan, L.;
Tomczyk, S.; Vourlidas, A.; Wu, Q.
Bibcode: 2014AGUFMSH53B4221K
Altcode:
Magnetic fields in the solar atmosphere provide the energy for most
varieties of solar activity, including high-energy electromagnetic
radiation, solar energetic particles, flares, and coronal mass
ejections, as well as powering the solar wind. Despite the fundamental
role of magnetic fields in solar and heliospheric physics, there
exists only very limited measurements of the field above the base of
the corona. What is needed are direct measurements of not only the
strength and orientation of the magnetic field but also the signatures
of wave motions in order to better understand coronal structure,
solar activity and the role of MHD waves in heating and accelerating
the solar wind. Fortunately, the remote sensing instrumentation used
to make magnetic field measurements is also well suited for measuring
the Doppler signature of waves in the solar structures. With this
in mind, we are proposing the WAMIS (Waves and Magnetism in the
Solar Atmosphere) investigation. WAMIS will take advantage of greatly
improved infrared (IR) detectors, forward models, advanced diagnostic
tools and inversion codes to obtain a breakthrough in the measurement
of coronal magnetic fields and in the understanding of the interaction
of these fields with space plasmas. This will be achieved with a high
altitude balloon borne payload consisting of a coronagraph with an IR
spectro-polarimeter focal plane assembly. The balloon platform provides
minimum atmospheric absorption and scattering at the IR wavelengths in
which these observations are made. Additionally, a NASA long duration
balloon flight mission from the Antarctic can achieve continuous
observations over most of a solar rotation, covering all of the key
time scales for the evolution of coronal magnetic fields. With these
improvements in key technologies along with experience gained from
current ground-based instrumentation, WAMIS will provide a low-cost
mission with a high technology readiness leve.
Title: Why Is Non-thermal Line Broadening of Lower Transition Region
Lines Independent of Spatial Resolution?
Authors: De Pontieu, B.; Mcintosh, S. W.; Martínez-Sykora, J.; Peter,
H.; Pereira, T. M. D.
Bibcode: 2014AGUFMSH51C4175D
Altcode:
Spectral observations of the solar transition region (TR) and
corona typically show broadening of the spectral lines beyond what
is expected from thermal and instrumental broadening. The remaining
non-thermal broadening is significant (10-30 km/s), correlated with
the intensity, and has been attributed to waves, macro and micro
turbulence, nanoflares, etc... Here we study spectra of the low
TR Si IV 1403 Angstrom line obtained at high spatial and spectral
resolution with the Interface Region Imaging Spectrograph (IRIS). We
find that the large improvement in spatial resolution (0.33 arcsec)
of IRIS compared to previous spectrographs (2 arcsec) does not resolve
the non-thermal line broadening which remains at pre-IRIS levels of
20 km/s. This surprising invariance to spatial resolution indicates
that the physical processes behind the non-thermal line broadening
either occur along the line-of-sight (LOS) and/or on spatial scales
(perpendicular to the LOS) smaller than 250 km. Both effects appear
to play a role. Comparison with IRIS chromospheric observations
shows that, in regions where the LOS is more parallel to the field,
magneto-acoustic shocks driven from below impact the low TR leading to
strong non-thermal line broadening from line-of-sight integration across
the shock at the time of impact. This scenario is confirmed by advanced
MHD simulations. In regions where the LOS is perpendicular to the field,
the prevalence of small-scale twist is likely to play a significant
role in explaining the invariance and the correlation with intensity.
Title: On Magnetic Activity Band Overlap, Interaction, and the
Formation of Complex Solar Active Regions
Authors: McIntosh, Scott W.; Leamon, Robert J.
Bibcode: 2014ApJ...796L..19M
Altcode: 2014arXiv1410.6411M
Recent work has revealed a phenomenological picture of the how the
~11 yr sunspot cycle of the Sun arises. The production and destruction
of sunspots is a consequence of the latitudinal-temporal overlap and
interaction of the toroidal magnetic flux systems that belong to the 22
yr magnetic activity cycle and are rooted deep in the Sun's convective
interior. We present a conceptually simple extension of this work,
presenting a hypothesis on how complex active regions can form as a
direct consequence of the intra- and extra-hemispheric interaction
taking place in the solar interior. Furthermore, during specific
portions of the sunspot cycle, we anticipate that those complex active
regions may be particularly susceptible to profoundly catastrophic
breakdown, producing flares and coronal mass ejections of the most
severe magnitude.
Title: Prevalence of small-scale jets from the networks of the solar
transition region and chromosphere
Authors: Tian, H.; DeLuca, E. E.; Cranmer, S. R.; De Pontieu, B.;
Peter, H.; Martínez-Sykora, J.; Golub, L.; McKillop, S.; Reeves,
K. K.; Miralles, M. P.; McCauley, P.; Saar, S.; Testa, P.; Weber,
M.; Murphy, N.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt, N.;
Tarbell, T. D.; Wuelser, J. P.; Kleint, L.; Kankelborg, C.; Jaeggli,
S.; Carlsson, M.; Hansteen, V.; McIntosh, S. W.
Bibcode: 2014Sci...346A.315T
Altcode: 2014arXiv1410.6143T
As the interface between the Sun’s photosphere and corona, the
chromosphere and transition region play a key role in the formation and
acceleration of the solar wind. Observations from the Interface Region
Imaging Spectrograph reveal the prevalence of intermittent small-scale
jets with speeds of 80 to 250 kilometers per second from the narrow
bright network lanes of this interface region. These jets have lifetimes
of 20 to 80 seconds and widths of ≤300 kilometers. They originate from
small-scale bright regions, often preceded by footpoint brightenings
and accompanied by transverse waves with amplitudes of ~20 kilometers
per second. Many jets reach temperatures of at least ~105
kelvin and constitute an important element of the transition region
structures. They are likely an intermittent but persistent source of
mass and energy for the solar wind.
Title: On the prevalence of small-scale twist in the solar
chromosphere and transition region
Authors: De Pontieu, B.; Rouppe van der Voort, L.; McIntosh, S. W.;
Pereira, T. M. D.; Carlsson, M.; Hansteen, V.; Skogsrud, H.; Lemen,
J.; Title, A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser,
J. P.; De Luca, E. E.; Golub, L.; McKillop, S.; Reeves, K.; Saar,
S.; Testa, P.; Tian, H.; Kankelborg, C.; Jaeggli, S.; Kleint, L.;
Martinez-Sykora, J.
Bibcode: 2014Sci...346D.315D
Altcode: 2014arXiv1410.6862D
The solar chromosphere and transition region (TR) form an interface
between the Sun’s surface and its hot outer atmosphere. There,
most of the nonthermal energy that powers the solar atmosphere
is transformed into heat, although the detailed mechanism remains
elusive. High-resolution (0.33-arc second) observations with NASA’s
Interface Region Imaging Spectrograph (IRIS) reveal a chromosphere
and TR that are replete with twist or torsional motions on sub-arc
second scales, occurring in active regions, quiet Sun regions, and
coronal holes alike. We coordinated observations with the Swedish
1-meter Solar Telescope (SST) to quantify these twisting motions and
their association with rapid heating to at least TR temperatures. This
view of the interface region provides insight into what heats the low
solar atmosphere.
Title: Deciphering Solar Magnetic Activity. I. On the Relationship
between the Sunspot Cycle and the Evolution of Small Magnetic Features
Authors: McIntosh, Scott W.; Wang, Xin; Leamon, Robert J.; Davey,
Alisdair R.; Howe, Rachel; Krista, Larisza D.; Malanushenko, Anna V.;
Markel, Robert S.; Cirtain, Jonathan W.; Gurman, Joseph B.; Pesnell,
William D.; Thompson, Michael J.
Bibcode: 2014ApJ...792...12M
Altcode: 2014arXiv1403.3071M
Sunspots are a canonical marker of the Sun's internal magnetic
field which flips polarity every ~22 yr. The principal variation of
sunspots, an ~11 yr variation, modulates the amount of the magnetic
field that pierces the solar surface and drives significant variations
in our star's radiative, particulate, and eruptive output over that
period. This paper presents observations from the Solar and Heliospheric
Observatory and Solar Dynamics Observatory indicating that the 11
yr sunspot variation is intrinsically tied to the spatio-temporal
overlap of the activity bands belonging to the 22 yr magnetic activity
cycle. Using a systematic analysis of ubiquitous coronal brightpoints
and the magnetic scale on which they appear to form, we show that the
landmarks of sunspot cycle 23 can be explained by considering the
evolution and interaction of the overlapping activity bands of the
longer-scale variability.
Title: Rotating Solar Jets in Simulations of Flux Emergence with
Thermal Conduction
Authors: Fang, Fang; Fan, Yuhong; McIntosh, Scott W.
Bibcode: 2014ApJ...789L..19F
Altcode: 2014arXiv1406.2220F
We study the formation of coronal jets through numerical simulation of
the emergence of a twisted magnetic flux rope into a pre-existing open
magnetic field. Reconnection inside the emerging flux rope in addition
to that between the emerging and pre-existing fields give rise to the
violent eruption studied. The simulated event closely resembles the
coronal jets ubiquitously observed by the X-Ray Telescope on board
Hinode and demonstrates that heated plasma is driven into the extended
atmosphere above. Thermal conduction implemented in the model allows
us to qualitatively compare simulated and observed emission from such
events. We find that untwisting field lines after the reconnection
drive spinning outflows of plasma in the jet column. The Poynting flux
in the simulated jet is dominated by the untwisting motions of the
magnetic fields loaded with high-density plasma. The simulated jet
is comprised of "spires" of untwisting field that are loaded with a
mixture of cold and hot plasma and exhibit rotational motion of order
20 km s-1 and match contemporary observations.
Title: The Interface Region Imaging Spectrograph (IRIS)
Authors: De Pontieu, B.; Title, A. M.; Lemen, J. R.; Kushner, G. D.;
Akin, D. J.; Allard, B.; Berger, T.; Boerner, P.; Cheung, M.; Chou,
C.; Drake, J. F.; Duncan, D. W.; Freeland, S.; Heyman, G. F.; Hoffman,
C.; Hurlburt, N. E.; Lindgren, R. W.; Mathur, D.; Rehse, R.; Sabolish,
D.; Seguin, R.; Schrijver, C. J.; Tarbell, T. D.; Wülser, J. -P.;
Wolfson, C. J.; Yanari, C.; Mudge, J.; Nguyen-Phuc, N.; Timmons,
R.; van Bezooijen, R.; Weingrod, I.; Brookner, R.; Butcher, G.;
Dougherty, B.; Eder, J.; Knagenhjelm, V.; Larsen, S.; Mansir, D.;
Phan, L.; Boyle, P.; Cheimets, P. N.; DeLuca, E. E.; Golub, L.;
Gates, R.; Hertz, E.; McKillop, S.; Park, S.; Perry, T.; Podgorski,
W. A.; Reeves, K.; Saar, S.; Testa, P.; Tian, H.; Weber, M.; Dunn, C.;
Eccles, S.; Jaeggli, S. A.; Kankelborg, C. C.; Mashburn, K.; Pust, N.;
Springer, L.; Carvalho, R.; Kleint, L.; Marmie, J.; Mazmanian, E.;
Pereira, T. M. D.; Sawyer, S.; Strong, J.; Worden, S. P.; Carlsson,
M.; Hansteen, V. H.; Leenaarts, J.; Wiesmann, M.; Aloise, J.; Chu,
K. -C.; Bush, R. I.; Scherrer, P. H.; Brekke, P.; Martinez-Sykora,
J.; Lites, B. W.; McIntosh, S. W.; Uitenbroek, H.; Okamoto, T. J.;
Gummin, M. A.; Auker, G.; Jerram, P.; Pool, P.; Waltham, N.
Bibcode: 2014SoPh..289.2733D
Altcode: 2014arXiv1401.2491D; 2014SoPh..tmp...25D
The Interface Region Imaging Spectrograph (IRIS) small explorer
spacecraft provides simultaneous spectra and images of the photosphere,
chromosphere, transition region, and corona with 0.33 - 0.4 arcsec
spatial resolution, two-second temporal resolution, and 1 km
s−1 velocity resolution over a field-of-view of up to
175 arcsec × 175 arcsec. IRIS was launched into a Sun-synchronous
orbit on 27 June 2013 using a Pegasus-XL rocket and consists of a
19-cm UV telescope that feeds a slit-based dual-bandpass imaging
spectrograph. IRIS obtains spectra in passbands from 1332 - 1358 Å,
1389 - 1407 Å, and 2783 - 2834 Å, including bright spectral lines
formed in the chromosphere (Mg II h 2803 Å and Mg II k 2796 Å) and
transition region (C II 1334/1335 Å and Si IV 1394/1403 Å). Slit-jaw
images in four different passbands (C II 1330, Si IV 1400, Mg II k
2796, and Mg II wing 2830 Å) can be taken simultaneously with spectral
rasters that sample regions up to 130 arcsec × 175 arcsec at a variety
of spatial samplings (from 0.33 arcsec and up). IRIS is sensitive to
emission from plasma at temperatures between 5000 K and 10 MK and will
advance our understanding of the flow of mass and energy through an
interface region, formed by the chromosphere and transition region,
between the photosphere and corona. This highly structured and dynamic
region not only acts as the conduit of all mass and energy feeding
into the corona and solar wind, it also requires an order of magnitude
more energy to heat than the corona and solar wind combined. The
IRIS investigation includes a strong numerical modeling component
based on advanced radiative-MHD codes to facilitate interpretation of
observations of this complex region. Approximately eight Gbytes of data
(after compression) are acquired by IRIS each day and made available
for unrestricted use within a few days of the observation.
Title: IRIS Observations of Twist in the Low Solar Atmosphere
Authors: De Pontieu, Bart; Rouppe van der Voort, Luc; Pereira,
Tiago M. D.; Skogsrud, Haakon; McIntosh, Scott W.; Carlsson, Mats;
Hansteen, Viggo
Bibcode: 2014AAS...22431302D
Altcode:
The Interface Region Imaging Spectrograph (IRIS) small explorer
was launched in June 2013. IRIS’s high-resolution (0.33 arcsec),
high-cadence (2s) images and spectra reveal a solar chromosphere and
transition region that is riddled with twist. This is evidenced by the
presence of ubiquitous torsional motions on very small (subarcsec)
spatial scales. These motions occur in active regions, quiet Sun
and coronal holes on a variety of structures such as spicules at
the limb, rapid-blue/red-shifted events (RBEs and RREs) as well as
low-lying loops. We use IRIS data and observations from the Swedish
Solar Telescope (SST) in La Palma, Spain to describe these motions
quantitatively, study their propagation, and illustrate how such
strong twisting motions are often associated with significant and
rapid heating to at least transition region temperatures.
Title: The Quasi-Annual Forcing of The Sun’s Eruptive, Radiative,
and Particulate Output
Authors: Leamon, Robert; McIntosh, Scott W.
Bibcode: 2014AAS...22442205L
Altcode:
The eruptive, radiative, and particulate output of the Sun are modulated
by our star’s enigmatic 11-year sunspot cycle. Over the past year
we have identified observational signatures which illustrate the ebb
and flow of the 11-year cycle - arising from the temporal overlap of
migrating activity bands which belong to the 22-year magnetic activity
cycle. (At the 2012 Fall AGU Meeting, Leamon & McIntosh presented
a prediction of minimum conditions developing in 2017 and Cycle 25
sunspots first appearing in late 2019.) As a consequence of this work we
have deduced that the latitudinal interaction of the oppositely signed
magnetic activity bands in each hemisphere (and across the equator near
solar minimum) dramatically impacts the production of Space Weather
events such as flares and Coronal Mass Ejections (CMEs). The same set
of observations also permits us to identify a quasi-annual variability
in the rotating convecting system which results in a significant local
modulation of solar surface magnetism. That modulation, in turn,
forces prolonged periods of significantly increased flare and CME
production, as well as significant changes in the Sun's ultraviolet
(UV), extreme ultraviolet (EUV), and X-Ray irradiance.
Title: Active region 11748: Recurring X-class flares, large scale
dimmings and waves.
Authors: Davey, Alisdair R.; Malanushenko, Anna; McIntosh, Scott W.
Bibcode: 2014AAS...22421818D
Altcode:
AR 11748 was a relatively compact active region that crossed the solar
disk between 05/14/2013 and 05/26/2013. Despite its size it produced
a number X-class flares, and global scale eruptive events that were
captured by the SDO Feature Finding Team's (FFT) Dimming Region
Detector. Using the results of this module and other FFT modules,
we present an analysis of the this AR region and investigate why it
was so globally impactful.
Title: The Chromosphere and Prominence Magnetometer
Authors: de Wijn, Alfred G.; McIntosh, Scott W.; Tomczyk, Steven
Bibcode: 2014shin.confE..76D
Altcode:
The Chromosphere and Prominence Magnetometer (ChroMag) is a synoptic
instrument with the goal of quantifying the intertwined dynamics
and magnetism of the solar chromosphere and in prominences through
imaging spectro-polarimetry of the full solar disk in a synoptic
fashion. The picture of chromospheric magnetism and dynamics is
rapidly developing, and a pressing need exists for breakthrough
observations of chromospheric vector magnetic field measurements
at the true lower boundary of the heliospheric system. ChroMag will
provide measurements that will enable scientists to study and better
understand the energetics of the solar atmosphere, how prominences are
formed, how energy is stored in the magnetic field structure of the
atmosphere and how it is released during space weather events like
flares and coronal mass ejections. An essential part of the ChroMag
program is a commitment to develop and provide community access to the
`inversion' tools necessary to interpret the measurements and derive
the magneto-hydrodynamic parameters of the plasma. Measurements of an
instrument like ChroMag provide critical physical context for the Solar
Dynamics Observatory (SDO) and Interface Region Imaging Spectrograph
(IRIS) as well as ground-based observatories such as the future Daniel
K. Inouye Solar Telescope (DKIST). A prototype is currently
deployed in Boulder, CO, USA. We will present an overview of instrument
capabilities and a progress update on the ChroMag development.
Title: Exploring the Components of IRIS Spectra: More Shift, Twist,
and Sway Than Shake, Rattle, and Roll
Authors: McIntosh, Scott W.; De Pontieu, Bart; Peter, Hardi
Bibcode: 2014AAS...22431304M
Altcode:
The beautifully rich spectra of the IRIS spacecraft offer an
unparalleled avenue to explore the mass and energy transport processes
which sustain the Sun's outer atmosphere. In this presentation we will
look in detail at the various components of the spectrographic data
and place them in context with Slit-Jaw imaging and EUV imaging from
SDO/AIA. We will show that the line profiles display many intriguing
features including the clear signatures of strong line-of-sight flows
(in all magnetized regions) that are almost always accompanied by
transverse and torsional motions at the finest resolvable scales. We
will demonstrate that many interesting relationships develop when
studying the spectra statistically. These relationships indicate IRIS's
ability to spectrally and temporally resolve the energetic processes
affecting the outer solar atmosphere.
Title: High-resolution Observations of the Shock Wave Behavior for
Sunspot Oscillations with the Interface Region Imaging Spectrograph
Authors: Tian, H.; DeLuca, E.; Reeves, K. K.; McKillop, S.; De Pontieu,
B.; Martínez-Sykora, J.; Carlsson, M.; Hansteen, V.; Kleint, L.;
Cheung, M.; Golub, L.; Saar, S.; Testa, P.; Weber, M.; Lemen, J.;
Title, A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser, J. P.;
Kankelborg, C.; Jaeggli, S.; McIntosh, S. W.
Bibcode: 2014ApJ...786..137T
Altcode: 2014arXiv1404.6291T
We present the first results of sunspot oscillations from observations
by the Interface Region Imaging Spectrograph. The strongly nonlinear
oscillation is identified in both the slit-jaw images and the
spectra of several emission lines formed in the transition region and
chromosphere. We first apply a single Gaussian fit to the profiles of
the Mg II 2796.35 Å, C II 1335.71 Å, and Si IV 1393.76 Å lines in the
sunspot. The intensity change is ~30%. The Doppler shift oscillation
reveals a sawtooth pattern with an amplitude of ~10 km s-1
in Si IV. The Si IV oscillation lags those of C II and Mg II by ~3 and
~12 s, respectively. The line width suddenly increases as the Doppler
shift changes from redshift to blueshift. However, we demonstrate
that this increase is caused by the superposition of two emission
components. We then perform detailed analysis of the line profiles at
a few selected locations on the slit. The temporal evolution of the
line core is dominated by the following behavior: a rapid excursion
to the blue side, accompanied by an intensity increase, followed by a
linear decrease of the velocity to the red side. The maximum intensity
slightly lags the maximum blueshift in Si IV, whereas the intensity
enhancement slightly precedes the maximum blueshift in Mg II. We find
a positive correlation between the maximum velocity and deceleration,
a result that is consistent with numerical simulations of upward
propagating magnetoacoustic shock waves.
Title: Identifying Potential Markers of the Sun's Giant Convective
Scale
Authors: McIntosh, Scott W.; Wang, Xin; Leamon, Robert J.; Scherrer,
Philip H.
Bibcode: 2014ApJ...784L..32M
Altcode: 2014arXiv1403.0692M
Line-of-sight magnetograms from the Helioseismic and Magnetic Imager
(HMI) of the Solar Dynamics Observatory (SDO) are analyzed using a
diagnostic known as the magnetic range of influence (MRoI). The MRoI
is a measure of the length over which a photospheric magnetogram
is balanced and so its application gives the user a sense of the
connective length scales in the outer solar atmosphere. The MRoI maps
and histograms inferred from the SDO/HMI magnetograms primarily exhibit
four scales: a scale of a few megameters that can be associated with
granulation, a scale of a few tens of megameters that can be associated
with super-granulation, a scale of many hundreds to thousands of
megameters that can be associated with coronal holes and active regions,
and a hitherto unnoticed scale that ranges from 100 to 250 Mm. We
infer that this final scale is an imprint of the (rotationally driven)
giant convective scale on photospheric magnetism. This scale appears
in MRoI maps as well-defined, spatially distributed concentrations that
we have dubbed "g-nodes." Furthermore, using coronal observations from
the Atmospheric Imaging Assembly on SDO, we see that the vicinity of
these g-nodes appears to be a preferred location for the formation of
extreme-ultraviolet (and likely X-Ray) brightpoints. These observations
and straightforward diagnostics offer the potential of a near real-time
mapping of the Sun's largest convective scale, a scale that possibly
reaches to the very bottom of the convective zone.
Title: Potential Evidence for the Onset of Alfvénic Turbulence in
Trans-equatorial Coronal Loops
Authors: De Moortel, I.; McIntosh, S. W.; Threlfall, J.; Bethge, C.;
Liu, J.
Bibcode: 2014ApJ...782L..34D
Altcode:
This study investigates Coronal Multi-channel Polarimeter Doppler-shift
observations of a large, off-limb, trans-equatorial loop system observed
on 2012 April 10-11. Doppler-shift oscillations with a broad range of
frequencies are found to propagate along the loop with a speed of about
500 km s-1. The power spectrum of perturbations travelling
up from both loop footpoints is remarkably symmetric, probably due to
the almost perfect north-south alignment of the loop system. Compared
to the power spectrum at the footpoints of the loop, the Fourier power
at the apex appears to be higher in the high-frequency part of the
spectrum than expected from theoretical models. We suggest this excess
high-frequency power could be tentative evidence for the onset of a
cascade of the low-to-mid frequency waves into (Alfvénic) turbulence.
Title: Using IRIS to Study Our Star's Outer Atmosphere's Mass Cycle
Authors: McIntosh, Scott; De Pontieu, Bart
Bibcode: 2014cosp...40E2049M
Altcode:
Through the analysis of IRIS FUV, NUV, and Slit-Jaw Imaging we will
explore the mass cycle of the Sun's outer atmosphere in conjunction
with observations from the Solar Dynamics Observatory and Hinode
Missions. IRIS readily observes upflows, downflows, and a persistent
flux of upward propagating hydrodynamic and magneto-hydrodynamic
waves. We will characterize the statistical and temporal variability
in the components of the various sources in the puzzle.
Title: Observations of Coronal Mass Ejections with the Coronal
Multichannel Polarimeter
Authors: Tian, H.; Tomczyk, S.; McIntosh, S. W.; Bethge, C.; de Toma,
G.; Gibson, S.
Bibcode: 2013SoPh..288..637T
Altcode: 2013arXiv1303.4647T
The Coronal Multichannel Polarimeter (CoMP) measures not only the
polarization of coronal emission, but also the full radiance profiles of
coronal emission lines. For the first time, CoMP observations provide
high-cadence image sequences of the coronal line intensity, Doppler
shift, and line width simultaneously over a large field of view. By
studying the Doppler shift and line width we may explore more of the
physical processes of the initiation and propagation of coronal mass
ejections (CMEs). Here we identify a list of CMEs observed by CoMP
and present the first results of these observations. Our preliminary
analysis shows that CMEs are usually associated with greatly increased
Doppler shift and enhanced line width. These new observations provide
not only valuable information to constrain CME models and probe
various processes during the initial propagation of CMEs in the low
corona, but also offer a possible cost-effective and low-risk means
of space-weather monitoring.
Title: The Evolving Magnetic Scales of the Outer Solar Atmosphere
and Their Potential Impact on Heliospheric Turbulence
Authors: McIntosh, Scott W.; Bethge, Christian; Threlfall, James;
De Moortel, Ineke; Leamon, Robert J.; Tian, Hui
Bibcode: 2013arXiv1311.2538M
Altcode:
The presence of turbulent phenomena in the outer solar atmosphere
is a given. However, because we are reduced to remotely sensing the
atmosphere of a star with instruments of limited spatial and/or spectral
resolution, we can only infer the physical progression from macroscopic
to microscopic phenomena. Even so, we know that many, if not all,
of the turbulent phenomena that pervade interplanetary space have
physical origins at the Sun and so in this brief article we consider
some recent measurements which point to sustained potential source(s)
of heliospheric turbulence in the magnetic and thermal domains. In
particular, we look at the scales of magnetism that are imprinted on
the outer solar atmosphere by the relentless magneto-convection of the
solar interior and combine state-of-the-art observations from the Solar
Dynamics Observatory (SDO) and the Coronal Multi-channel Polarimeter
(CoMP) which are beginning to hint at the origins of the wave/plasma
interplay prevalent closer to the Earth. While linking these disparate
scales of observation and understanding of their connection is near
to impossible, it is clear that the constant evolution of subsurface
magnetism on a host of scales guides and governs the flow of mass
and energy at the smallest scales. In the near future significant
progress in this area will be made by linking observations from high
resolution platforms like the Interface Region Imaging Spectrograph
(IRIS) and Advanced Technology Solar Telescope (ATST) with full-disk
synoptic observations such as those presented herein.
Title: Temperature dependence of ultraviolet line parameters in
network and internetwork regions of the quiet Sun and coronal holes
Authors: Wang, X.; McIntosh, S. W.; Curdt, W.; Tian, H.; Peter, H.;
Xia, L. -D.
Bibcode: 2013A&A...557A.126W
Altcode:
Aims: We study the temperature dependence of the average Doppler
shift and the non-thermal line width in network and internetwork
regions for both the quiet Sun (QS) and the coronal hole (CH), by
using observations of the Solar Ultraviolet Measurements of Emitted
Radiation instrument onboard the Solar and Heliospheric Observatory
spacecraft.
Methods: We obtain the average Doppler shift and
non-thermal line width in the network regions of QS, internetwork
regions of QS, network regions of CH, and internetwork regions of CH by
applying a single-Gaussian fit to the line profiles averaged in each
of the four regions. The formation temperatures of the lines we use
cover the range from 104 to 1.2 × 106 K. Two
simple scenarios are proposed to explain the temperature dependence of
the line parameters in the network regions. In one of the scenarios,
the spectral line consists of three components: a rapid, weak upflow
generated in the lower atmosphere, a nearly static background, and
a slow cooling downflow. In the other scenario, there are just two
components, which include a bright core component and a faint wide tail
one.
Results: An enhancement of the Doppler shift magnitude
and the non-thermal line width in network regions compared to the
internetwork regions is reported. We also report that most transition
region lines are less redshifted (by 0-8 km s-1) and broader
(by 0-5 km s-1) in CH compared to the counterparts of QS. In
internetwork regions, the difference in the Doppler shifts between the
coronal hole and the QS is slightly smaller, especially for the lines
with formation temperatures lower than 2 × 105 K. And the
two simple scenarios can reproduce the variation in the line parameters
with the temperature very well.
Conclusions: Our results suggest
that the physical processes in network and internetwork regions are
different and that one needs to separate network and internetwork when
discussing dynamics and physical properties of the solar atmosphere. The
agreement between the results of the observation and our scenarios
suggests that the temperature dependence of Doppler shifts and line
widths might be caused by the different relative contributions of the
three components at different temperatures. The results may shed new
light on our understanding of the complex chromosphere-corona mass
cycle. However, the existing observational results do not allow us to
distinguish between the two scenarios. At this stage, a high-resolution
instrument Interface Region Imaging Spectrograph is highly desirable.
Title: First comparison of wave observations from CoMP and AIA/SDO
Authors: Threlfall, J.; De Moortel, I.; McIntosh, S. W.; Bethge, C.
Bibcode: 2013A&A...556A.124T
Altcode: 2013arXiv1306.3354T
Context. Waves have long been thought to contribute to the heating
of the solar corona and the generation of the solar wind. Recent
observations have demonstrated evidence of quasi-periodic longitudinal
disturbances and ubiquitous transverse wave propagation in many
different coronal environments.
Aims: This paper investigates
signatures of different types of oscillatory behaviour, both above
the solar limb and on-disk, by comparing findings from the Coronal
Multi-channel Polarimeter (CoMP) and the Atmospheric Imaging
Assembly (AIA) on-board the Solar Dynamics Observatory (SDO) for
the same active region.
Methods: We study both transverse and
longitudinal motion by comparing and contrasting time-distance images
of parallel and perpendicular cuts along/across active region fan
loops. Comparisons between parallel space-time diagram features in
CoMP Doppler velocity and transverse oscillations in AIA images are
made, together with space-time analysis of propagating quasi-periodic
intensity features seen near the base of loops in AIA.
Results:
Signatures of transverse motions are observed along the same magnetic
structure using CoMP Doppler velocity (vphase = 600 → 750
km s-1, P = 3 → 6 min) and in AIA/SDO above the limb (P =
3 → 8 min). Quasi-periodic intensity features (vphase =
100 → 200 km s-1, P = 6 → 11 min) also travel along the
base of the same structure. On the disk, signatures of both transverse
and longitudinal intensity features were observed by AIA, and both show
similar properties to signatures found along structures anchored in
the same active region three days earlier above the limb. Correlated
features are recovered by space-time analysis of neighbouring tracks
over perpendicular distances of ≲2.6 Mm.
Title: A Detailed Comparison between the Observed and Synthesized
Properties of a Simulated Type II Spicule
Authors: Martínez-Sykora, Juan; De Pontieu, Bart; Leenaarts, Jorrit;
Pereira, Tiago M. D.; Carlsson, Mats; Hansteen, Viggo; Stern, Julie
V.; Tian, Hui; McIntosh, Scott W.; Rouppe van der Voort, Luc
Bibcode: 2013ApJ...771...66M
Altcode: 2013arXiv1305.2397M
We have performed a three-dimensional radiative MHD simulation of the
solar atmosphere. This simulation shows a jet-like feature that shows
similarities to the type II spicules observed for the first time with
Hinode's Solar Optical Telescope. Rapid blueshifted events (RBEs) on the
solar disk are associated with these spicules. Observational results
suggest they may contribute significantly in supplying the corona
with hot plasma. We perform a detailed comparison of the properties
of the simulated jet with those of type II spicules (observed with
Hinode) and RBEs (with ground-based instruments). We analyze a wide
variety of synthetic emission and absorption lines from the simulations
including chromospheric (Ca II 8542 Å, Ca II H, and Hα) to transition
region and coronal temperatures (10,000 K to several million K). We
compare their synthetic intensities, line profiles, Doppler shifts,
line widths, and asymmetries with observations from Hinode/SOT and
EIS, SOHO/SUMER, the Swedish 1 m Solar Telescope, and SDO/AIA. Many
properties of the synthetic observables resemble the observations,
and we describe in detail the physical processes that lead to these
observables. Detailed analysis of the synthetic observables provides
insight into how observations should be analyzed to derive information
about physical variables in such a dynamic event. For example, we
find that line-of-sight superposition in the optically thin atmosphere
requires the combination of Doppler shifts and spectral line asymmetry
to determine the velocity in the jet. In our simulated type II spicule,
the lifetime of the asymmetry of the transition region lines is shorter
than that of the coronal lines. Other properties differ from the
observations, especially in the chromospheric lines. The mass density
of the part of the spicule with a chromospheric temperature is too low
to produce significant opacity in chromospheric lines. The synthetic
Ca II 8542 Å and Hα profiles therefore do not show signal resembling
RBEs. These and other discrepancies are described in detail, and we
discuss which mechanisms and physical processes may need to be included
in the MHD simulations to mimic the thermodynamic processes of the
chromosphere and corona, in particular to reproduce type II spicules.
Title: The Chromosphere and Prominence Magnetometer
Authors: de Wijn, Alfred; Bethge, Christian; McIntosh, Scott; Tomczyk,
Steven; Burkepile, Joan
Bibcode: 2013EGUGA..1512765D
Altcode:
The Chromosphere and Prominence Magnetometer (ChroMag) is a synoptic
instrument with the goal of quantifying the intertwined dynamics
and magnetism of the solar chromosphere and in prominences through
imaging spectro-polarimetry of the full solar disk in a synoptic
fashion. The picture of chromospheric magnetism and dynamics is
rapidly developing, and a pressing need exists for breakthrough
observations of chromospheric vector magnetic field measurements
at the true lower boundary of the heliospheric system. ChroMag will
provide measurements that will enable scientists to study and better
understand the energetics of the solar atmosphere, how prominences are
formed, how energy is stored in the magnetic field structure of the
atmosphere and how it is released during space weather events like
flares and coronal mass ejections. An essential part of the ChroMag
program is a commitment to develop and provide community access to the
`inversion' tools necessary to interpret the measurements and derive
the magneto-hydrodynamic parameters of the plasma. Measurements of an
instrument like ChroMag provide critical physical context for the Solar
Dynamics Observatory (SDO) and Interface Region Imaging Spectrograph
(IRIS) as well as ground-based observatories such as the future Advanced
Technology Solar Telescope (ATST). A prototype is currently under
construction at the High Altitude Observatory of the National Center
for Atmospheric Research in Boulder, CO, USA. The heart of the ChroMag
instrument is an electro-optically tunable wide-fielded narrow-band
birefringent six-stage Lyot filter with a built-in polarimeter. We
will present a progress update on the ChroMag design, and present
results from the prototype instrument.
Title: On the Modulation of the Solar Activity Cycles, and Hemispheric
Asymmetry of Solar Magnetism during the Cycle 23/24 Minimum
Authors: Leamon, Robert J.; McIntosh, Scott W.
Bibcode: 2013enss.confE.140L
Altcode:
We address the origin of the 11-year (quasi-)periodicity of the sunspot
cycle by tying it to the significant temporal overlap of activity bands
belonging to the 22-year magnetic activity cycle. Using a systematic
analysis of ubiquitous coronal brightpoints, and the prevalent
magnetic scale on which they form, we are able to observationally
demonstrate the entirety of the 22-year magnetic activity cycle. The
phases of the sunspot cycle occur as landmarks in the interaction and
evolution of the overlapping activity bands in each hemisphere. The
unusual conditions of the recent Cycle 23/24 minimum can be directly
attributed to the asymmetry (southern lag) between the two hemispheres
of the sun. The work presented establishes significant observational
constraints for models of the origins of solar magnetic activity and
will, as a result, improve our understanding of the structure of the
heliosphere and the modulation of our star's radiative and particulate
output. We demonstrate how the Sun can descend into, and recover from,
Grand Minima. Even if that is not where we're headed, we show why
Cycle 25 is likely to be even weaker than Cycle 24.
Title: Hemispheric Asymmetries of Solar Photospheric Magnetism:
Radiative, Particulate, and Heliospheric Impacts
Authors: McIntosh, Scott W.; Leamon, Robert J.; Gurman, Joseph B.;
Olive, Jean-Philippe; Cirtain, Jonathan W.; Hathaway, David H.;
Burkepile, Joan; Miesch, Mark; Markel, Robert S.; Sitongia, Leonard
Bibcode: 2013ApJ...765..146M
Altcode: 2013arXiv1302.1081M
Among many other measurable quantities, the summer of 2009 saw
a considerable low in the radiative output of the Sun that was
temporally coincident with the largest cosmic-ray flux ever measured
at 1 AU. Combining measurements and observations made by the Solar and
Heliospheric Observatory (SOHO) and Solar Dynamics Observatory (SDO)
spacecraft we begin to explore the complexities of the descending phase
of solar cycle 23, through the 2009 minimum into the ascending phase of
solar cycle 24. A hemispheric asymmetry in magnetic activity is clearly
observed and its evolution monitored and the resulting (prolonged)
magnetic imbalance must have had a considerable impact on the structure
and energetics of the heliosphere. While we cannot uniquely tie the
variance and scale of the surface magnetism to the dwindling radiative
and particulate output of the star, or the increased cosmic-ray flux
through the 2009 minimum, the timing of the decline and rapid recovery
in early 2010 would appear to inextricably link them. These observations
support a picture where the Sun's hemispheres are significantly out
of phase with each other. Studying historical sunspot records with
this picture in mind shows that the northern hemisphere has been
leading since the middle of the last century and that the hemispheric
"dominance" has changed twice in the past 130 years. The observations
presented give clear cause for concern, especially with respect to
our present understanding of the processes that produce the surface
magnetism in the (hidden) solar interior—hemispheric asymmetry is the
normal state—the strong symmetry shown in 1996 was abnormal. Further,
these observations show that the mechanism(s) which create and transport
the magnetic flux are slowly changing with time and, it appears, with
only loose coupling across the equator such that those asymmetries can
persist for a considerable time. As the current asymmetry persists and
the basal energetics of the system continue to dwindle we anticipate
new radiative and particulate lows coupled with increased cosmic-ray
fluxes heading into the next solar minimum.
Title: Recent Observations of Plasma and Alfvénic Wave Energy
Injection at the Base of the Fast Solar Wind
Authors: McIntosh, Scott W.
Bibcode: 2013mspc.book...69M
Altcode:
No abstract at ADS
Title: A Coral Sea Rehearsal for the Eclipse Megamovie
Authors: Hudson, H. S.; Davey, A. R.; Ireland, J.; Jones, L.; Mcintosh,
S. W.; Paglierani, R.; Pasachoff, J. M.; Peticolas, L. M.; Russell,
R. M.; Suarez Sola, F. I.; Sutherland, L.; Thompson, M. J.
Bibcode: 2012AGUFMSH11C..06H
Altcode:
The "Eclipse on the Coral Sea" - 13/14 November 2012 (GMT/Australia)
- will have happened already. Our intention is to have used this
opportunity as a trial run for the eclipse in 2017, which features
1.5 hours of totality across the whole width of the continental
US. Conceived first and foremost as an education and public outreach
activity, the plan is to engage the public in solar science and
technology by providing a way for them to include images they have taken
of the solar eclipse, into a movie representation of coronal evolution
in time. This project will assimilate as much eclipse photography as
possible from the public. The resulting movie(s) will cover all ranges
of expertise, and at the basic smartphone or hand-held digital camera
level, we expect to have obtained a huge number of images in the case
of good weather conditions. The capability of modern digital technology
to handle such a data flow is new. The basic purpose of this and the
2017 Megamovie observations is to explore this capability and its
ability to engage people from many different communities in the solar
science, astronomy, mathematics, and technology. The movie in 2017,
especially, may also have important science impact because of the
uniqueness of the corona as seen under eclipse conditions. In this
presentation we will describe our smartphone application development
(see the "Transit of Venus" app for a role model here). We will also
summarize data acquisition via both the app and more traditional web
interfaces. Although for the Coral Sea eclipse event we don't expect to
have a movie product by the time of the AGU, for the 2017 event we do
intend to assemble the heterogenous data into beautiful movies within a
short space of time after the eclipse. These movies may have relatively
low resolution but would extend to the base of the corona. We encourage
participation in the 2012 observations, noting that no total eclipse,
prior to 2017, will occur in a region with good infrastructure for
extended observations. The National Center for Atmospheric Research is
sponsored by the National Science Foundation. The Megamovie project
is supported by NSF grant AGS-1247226, and JMP's eclipse work about
the eclipses of 2012 is supported by NSF grant AGS-1047726.
Title: Understanding the Mass-cycle of the Outer Solar Atmosphere
Authors: Mcintosh, S. W.
Bibcode: 2012AGUFMSH32A..01M
Altcode:
The observations of Hinode and SDO have provided insight into the
processes and timescales governing the mass-transport into (and out
of) the outer solar atmosphere. Understanding these processes is
vital to understanding the radiative and particulate output of our
star. We will look at the analysis of the imaging and spectroscopic
data that are available to the community, and how we are pushing the
limitations of those data. What can we learn about the "mass-cycle"
from the observations that we have and what does the near (IRIS)
and extended future (Solar Orbiter, Solar-C) hold in store?
Title: A Hemispheric Asymmetry of Solar Photospheric Magnetism:
Radiative, Particulate and Heliospheric Impacts
Authors: Mcintosh, S. W.
Bibcode: 2012AGUFMSH52C..02M
Altcode:
Among many other measurable quantities the summer of 2009 saw
a considerable low in the radiative output of the Sun that was
temporally coincident with the largest cosmic ray flux ever measured
at 1AU. Combining measurements and observations made by the Solar and
Heliospheric Observatory and Solar Dynamics Observatory spacecraft we
begin to explore the complexities of the descending phase of solar cycle
23, through the 2009 minimum into the ascending phase of solar cycle
24. A hemispheric asymmetry in magnetic activity is clearly observed and
its evolution monitored and the resulting (prolonged) magnetic imbalance
must have had a considerable impact on the structure and energetics of
the heliosphere. While we cannot uniquely tie the variance and scale
of the surface magnetism to the dwindling radiative and particulate
output of the star, or the increased cosmic ray flux through the 2009
minimum, the timing of the decline and rapid recovery in early 2010
would appear to inextricably link them. These observations would appear
to lend support to a picture where the hemispheres of the Sun have a
(slightly) different meridional circulation rates and, furthermore,
that the hemispheres are vary out of phase with each other. Studying
historical sunspot records with this picture in mind shows that the
northern hemisphere has been leading since the middle of the last
century and that the hemispheric "dominance" has changed twice in the
past 130 years. The observations presented give clear cause for concern,
especially with respect to our present understanding of the processes
that produce the surface magnetism in the (hidden) solar interior -
only time will tell if our concern is well founded or not with the
apparent dwindling of the radiative and particulate output over the
past 30 years.
Title: Estimating the "Dark" Energy Content of the Solar Corona
Authors: McIntosh, Scott W.; De Pontieu, Bart
Bibcode: 2012ApJ...761..138M
Altcode: 2012arXiv1211.4178M
The discovery of ubiquitous low-frequency (3-5 mHz) Alfvénic waves
in the solar chromosphere (with Hinode/Solar Optical Telescope)
and corona (with CoMP and SDO) has provided some insight into the
non-thermal energy content of the outer solar atmosphere. However,
many questions remain about the true magnitude of the energy flux
carried by these waves. Here we explore the apparent discrepancy in
the resolved coronal Alfvénic wave amplitude (~0.5 km s-1)
measured by the Coronal Multi-channel Polarimeter (CoMP) compared to
those of the Hinode and the Solar Dynamics Observatory (SDO) near the
limb (~20 km s-1). We use a blend of observational data and
a simple forward model of Alfvénic wave propagation to resolve this
discrepancy and determine the Alfvénic wave energy content of the
corona. Our results indicate that enormous line-of-sight superposition
within the coarse spatio-temporal sampling of CoMP hides the strong
wave flux observed by Hinode and SDO and leads to the large non-thermal
line broadening observed. While this scenario has been assumed in
the past, our observations with CoMP of a strong correlation between
the non-thermal line broadening with the low-amplitude, low-frequency
Alfvénic waves observed in the corona provide the first direct evidence
of a wave-related non-thermal line broadening. By reconciling the
diverse measurements of Alfvénic waves, we establish large coronal
non-thermal line widths as direct signatures of the hidden, or "dark,"
energy content in the corona and provide preliminary constraints on
the energy content of the wave motions observed.
Title: Recent Observations of Plasma and Alfvénic Wave Energy
Injection at the Base of the Fast Solar Wind
Authors: McIntosh, Scott W.
Bibcode: 2012SSRv..172...69M
Altcode: 2012arXiv1205.3821M; 2012SSRv..tmp...30M; 2012SSRv..tmp...37M
We take stock of recent observations that identify the episodic plasma
heating and injection of Alfvénic energy at the base of fast solar wind
(in coronal holes). The plasma heating is associated with the occurrence
of chromospheric spicules that leave the lower solar atmosphere at
speeds of order 100 km/s, the hotter coronal counterpart of the spicule
emits radiation characteristic of root heating that rapidly reaches
temperatures of the order of 1 MK. Furthermore, the same spicules and
their coronal counterparts ("Propagating Coronal Disturbances"; PCD)
exhibit large amplitude, high speed, Alfvénic (transverse) motion of
sufficient energy content to accelerate the material to high speeds. We
propose that these (disjointed) heating and accelerating components
form a one-two punch to supply, and then accelerate, the fast solar
wind. We consider some compositional constraints on this concept,
extend the premise to the slow solar wind, and identify future avenues
of exploration.
Title: Persistent Doppler Shift Oscillations Observed with Hinode/EIS
in the Solar Corona: Spectroscopic Signatures of Alfvénic Waves
and Recurring Upflows
Authors: Tian, Hui; McIntosh, Scott W.; Wang, Tongjiang; Ofman, Leon;
De Pontieu, Bart; Innes, Davina E.; Peter, Hardi
Bibcode: 2012ApJ...759..144T
Altcode: 2012arXiv1209.5286T
Using data obtained by the EUV Imaging Spectrometer on board Hinode,
we have performed a survey of obvious and persistent (without
significant damping) Doppler shift oscillations in the corona. We
have found mainly two types of oscillations from February to April
in 2007. One type is found at loop footpoint regions, with a dominant
period around 10 minutes. They are characterized by coherent behavior
of all line parameters (line intensity, Doppler shift, line width,
and profile asymmetry), and apparent blueshift and blueward asymmetry
throughout almost the entire duration. Such oscillations are likely to
be signatures of quasi-periodic upflows (small-scale jets, or coronal
counterpart of type-II spicules), which may play an important role
in the supply of mass and energy to the hot corona. The other type of
oscillation is usually associated with the upper part of loops. They are
most clearly seen in the Doppler shift of coronal lines with formation
temperatures between one and two million degrees. The global wavelets
of these oscillations usually peak sharply around a period in the range
of three to six minutes. No obvious profile asymmetry is found and
the variation of the line width is typically very small. The intensity
variation is often less than 2%. These oscillations are more likely to
be signatures of kink/Alfvén waves rather than flows. In a few cases,
there seems to be a π/2 phase shift between the intensity and Doppler
shift oscillations, which may suggest the presence of slow-mode standing
waves according to wave theories. However, we demonstrate that such a
phase shift could also be produced by loops moving into and out of a
spatial pixel as a result of Alfvénic oscillations. In this scenario,
the intensity oscillations associated with Alfvénic waves are caused by
loop displacement rather than density change. These coronal waves may be
used to investigate properties of the coronal plasma and magnetic field.
Title: The chromosphere and prominence magnetometer
Authors: de Wijn, Alfred G.; Bethge, Christian; Tomczyk, Steven;
McIntosh, Scott
Bibcode: 2012SPIE.8446E..78D
Altcode: 2012arXiv1207.0969D
The Chromosphere and Prominence Magnetometer (ChroMag) is conceived
with the goal of quantifying the intertwined dynamics and magnetism
of the solar chromosphere and in prominences through imaging spectro-
polarimetry of the full solar disk. The picture of chromospheric
magnetism and dynamics is rapidly developing, and a pressing need
exists for breakthrough observations of chromospheric vector magnetic
field measurements at the true lower boundary of the heliospheric
system. ChroMag will provide measurements that will enable scientists
to study and better understand the energetics of the solar atmosphere,
how prominences are formed, how energy is stored in the magnetic field
structure of the atmosphere and how it is released during space weather
events like flares and coronal mass ejections. An integral part of the
ChroMag program is a commitment to develop and provide community access
to the "inversion" tools necessary for the difficult interpretation
of the measurements and derive the magneto-hydrodynamic parameters of
the plasma. Measurements of an instrument like ChroMag provide critical
physical context for the Solar Dynamics Observatory (SDO) and Interface
Region Imaging Spectrograph (IRIS) as well as ground-based observatories
such as the future Advanced Technology Solar Telescope (ATST).
Title: Propagating Disturbances in Coronal Loops: A Detailed Analysis
of Propagation Speeds
Authors: Kiddie, G.; De Moortel, I.; Del Zanna, G.; McIntosh, S. W.;
Whittaker, I.
Bibcode: 2012SoPh..279..427K
Altcode: 2012arXiv1205.0891K
Quasi-periodic disturbances have been observed in the outer solar
atmosphere for many years. Although first interpreted as upflows
(Schrijver et al., Solar Phys.187, 261, 1999), they have been widely
regarded as slow magneto-acoustic waves, due to their observed
velocities and periods. However, recent observations have questioned
this interpretation, as periodic disturbances in Doppler velocity,
line width, and profile asymmetry were found to be in phase with the
intensity oscillations (De Pontieu and McIntosh, Astrophys. J.722,
1013, 2010; Tian, McIntosh, and De Pontieu, Astrophys. J. Lett.727,
L37, 2011), suggesting that the disturbances could be quasi-periodic
upflows. Here we conduct a detailed analysis of the velocities of
these disturbances across several wavelengths using the Atmospheric
Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). We
analysed 41 examples, including both sunspot and non-sunspot regions
of the Sun. We found that the velocities of propagating disturbances
(PDs) located at sunspots are more likely to be temperature dependent,
whereas the velocities of PDs at non-sunspot locations do not show a
clear temperature dependence. This suggests an interpretation in terms
of slow magneto-acoustic waves in sunspots but the nature of PDs in
non-sunspot (plage) regions remains unclear. We also considered on
what scale the underlying driver is affecting the properties of the
PDs. Finally, we found that removing the contribution due to the cooler
ions in the 193 Å wavelength suggests that a substantial part of the
193 Å emission of sunspot PDs can be attributed to the cool component
of 193 Å.
Title: Temperature Dependence of UV Line Parameters in Network and
Internetwork Regions of the Quiet Sun and Coronal holes
Authors: Wang, Xin; McIntosh, Scott W.; Tian, Hui
Bibcode: 2012shin.confE...7W
Altcode:
By using observations of SUMER on board the SOHO spacecraft, we study
the temperature dependence of the Doppler shift, non-thermal width in
network and internetwork regions for both the quiet Sun (QS) and the
coronal hole (CH). In network regions, most of the transition region
(TR) line profiles are more red shifted (by 0-5km/s) and narrower (by
1-6km/s) in QS than in CH. Our results suggest that the mass cycle
between the chromosphere and corona mainly occurs in the network
and one needs to separate network and internetwork when discussing
thermal and dynamic properties of the solar atmosphere. In addition, a
three-component toy model is built to explain the temperature dependence
of the line parameters, which includes a rapid, weak upflow generated
in the lower atmosphere, a nearly static background, and a slow cooling
downflow. The agreement between the results of the observation and our
model suggests that the temperature dependence of Doppler shifts and
line widths might be caused by the different relative contributions of
the three components at different temperatures and will shed a new light
on our understanding of the complex chromosphere-coronal mass cycle.
Title: Two components of the coronal emission revealed by both
spectroscopic and imaging observations
Authors: Tian, Hui; McIntosh, Scott W.; De Pontieu, Bart
Bibcode: 2012shin.confE...1T
Altcode:
Boundaries of active regions have been suggested to be possible sources
of the slow solar wind. X-ray and EUV imaging observations often reveal
high-speed ( 100 km/s) quasi-periodic propagating disturbances (PDs)
along the fan-like structures at edges of active regions. Meanwhile EUV
spectroscopic observations of active region boundaries usually reveal
a blue shift of the order of 20 km/s and no periodicity. We think that
the key to solve these discrepancies is the asymmetry of the emission
line profile. The ubiquitous presence of blueward asymmetries of EUV
emission line profiles suggests at least two emission components:
a primary component accounting for the background coronal emission
and a weak secondary component associated with high-speed ( 100 km/s)
upflows. Through jointed imaging and spectroscopic observations, we have
demonstrated that the PDs are responsible for the secondary component
of line profiles and suggested that they may be an efficient means to
provide heated mass into the corona and solar wind. The intermittent
nature of these high-speed outflows (fine-scale jets) suggests that
the mass supply to the corona and solar wind is episodic rather than
continuous. Similar spectroscopic signatures have also been found in
CME-induced dimming regions, suggesting possible solar wind streams from
dimming regions. Unresolved problems include the production mechanism
of these high-speed outflows and the connection between these outflows
to the interplanetary space.
Title: New insight into CME processes revealed by CoMP observations
Authors: Tian, Hui; McIntosh, Scott W.; Bethge, Christian; Tomczyk,
Steve; Sitongia, Leonard E.
Bibcode: 2012shin.confE..11T
Altcode:
CoMP measures not only the polarization of coronal emission, but also
measures the full radiance profiles of coronal emission lines. For the
first time, CoMP observations provide high-cadence image sequences
of the coronal intensity, Doppler shift, line width and linear
polarization simultaneously. These measurements may help us explore
more of the physical processes at the onset of solar eruptions such
as CMEs and flares. They should also provide important constraints to
models of solar eruptions. Our preliminary analysis shows that CMEs are
usually associated with greatly increased Doppler shift and enhanced
line width. The linear polarization in CMEs measured by CoMP has also
been investigated.
Title: What can we Learn about Solar Coronal Mass Ejections,
Coronal Dimmings, and Extreme-Ultraviolet Jets Through Spectroscopic
Observations?
Authors: Tian, Hui; McIntosh, Scott W.; Xia, L. -D.; He, J. -S.;
Wang, X.
Bibcode: 2012shin.confE..10T
Altcode:
Solar eruptions, particularly coronal mass ejections (CMEs) and
extreme-ultraviolet (EUV) jets, have rarely been investigated with
spectroscopic observations. We analyze several data sets obtained by
the EUV Imaging Spectrometer onboard Hinode and find various types of
flows during CMEs and jet eruptions. We found weak high-speed ( 100
km/s) outflows in CME induced dimming regions, temperature-dependent
outflows (speed increases with temperature) immediately outside the
dimming region, and strong high-speed ( 200 km/s) outflows associated
with the CME ejecta and EUV jets. We have made plasma diagnostics
(density, temperature, mass) for the dimming regions and CME/jet
ejecta. Our results suggest that spectroscopic observations can provide
useful information on the kinematics and plasma properties of solar
mass eruptions.
Title: The Chromospheric Magnetometer ChroMag
Authors: Bethge, Christian; de Wijn, A. G.; McIntosh, S. W.; Tomczyk,
S.; Casini, R.
Bibcode: 2012AAS...22013506B
Altcode:
We present the Chromosphere Magnetometer (ChroMag), which is part of
the Coronal Solar Magnetism Observatory (COSMO) proposed by the High
Altitude Observatory (HAO) in collaboration with the University of
Hawaii and the University of Michigan. ChroMag will perform routine
measurements of chromospheric magnetic fields in a synoptic manner. A prototype is currently being assembled at HAO. The main component of
the instrument is a Lyot-type filtergraph polarimeter for both on-disk
and off-limb polarization measurements in the spectral lines of
H alpha at 656.3 nm, Fe I 617.3 nm, Ca II 854.2 nm, He I 587.6 nm,
and He I 1083.0 nm. The Lyot filter is tunable at a fast rate. This
allows to determine line-of-sight velocities in addition to the
magnetic field measurements. The instrument has a field-of-view of
up to 2.5 solar radii and will acquire data at a cadence of less than
1 minute and at a spatial resolution of 2 arcsec. The community will
have open access to the data as well as to a set of inversion tools
for an easier interpretation of the measurements. We show an overview
of the proposed instrument and first results from the protoype.
Title: The Journey of Sungrazing Comet Lovejoy
Authors: Bryans, Paul; A'Hearn, M.; Battams, K.; Biesecker, D.;
Bodewits, D.; Boice, D.; Brown, J.; Caspi, A.; Chodas, P.; Hudson,
H.; Jia, Y.; Jones, G.; Keller, H. U.; Knight, M.; Linker, J.; Lisse,
C.; Liu, W.; McIntosh, S.; Pesnell, W. D.; Raymond, J.; Saar, S.;
Saint-Hilaire, P.; Schrijver, C.; Snow, M.; Tarbell, T.; Thompson,
W.; Weissman, P.; Comet Lovejoy Collaboration Team
Bibcode: 2012AAS...22052507B
Altcode:
Comet Lovejoy (C/2011 W3) was the first sungrazing comet, observed
by space-based instruments, to survive perihelion passage. First
observed by ground-based telescopes several weeks prior to perihelion,
its journey towards the Sun was subsequently recorded by several solar
observatories, before being observed in the weeks after perihelion by
a further array of space- and ground-based instruments. Such a surfeit
of wide-ranging observations provides an unprecedented insight into
both sungrazing comets themselves, and the solar atmosphere through
which they pass. This paper will summarize what we have learnt from the
observations thus far and offer some thoughts on what future sungrazing
comets may reveal about comets, the Sun, and their interaction.
Title: Recent Results from the Coronal Multi-Channel Polarimeter
Authors: Tomczyk, Steven; Bethge, C.; Gibson, S. E.; McIntosh, S. W.;
Rachmeler, L. A.; Tian, H.
Bibcode: 2012AAS...22031001T
Altcode:
The Coronal Multi-Channel Polarimeter (CoMP) instrument is a
ground-based filter/polarimeter which can image the solar corona at
wavelengths around the emission lines of FeXIII at 1074.7 and 1079.8
nm and the chromospheric emission line of HeI at 1083.0 nm. The
instrument consists of a 20-cm aperture coronagraph followed by a
Stokes polarimeter and a Lyot birefringent filter with a passband
of 0.14 nm width. Both the polarimeter and filter employ liquid
crystals for rapid electro-optical tuning. This instrument measures
the line-of-sight strength of the coronal magnetic field through the
Zeeman effect and the plane-of-sky direction of the magnetic field via
resonance scattering. The line-of-sight velocity can also be determined
from the Doppler shift. The CoMP has obtained daily observations from
the Mauna Loa Solar Observatory for almost one year. We will present
recent measurements of the polarization signatures seen with the
CoMP and a comparison with models that allow us to constrain coronal
structure. We also will present observations of coronal waves taken
with the CoMP and discuss their implications for the heating of the
solar corona and the acceleration of the solar wind.
Title: Hinode/EIS Line Profile Asymmetries and Their Relationship with
the Distribution of SDO/AIA Propagating Coronal Disturbance Velocities
Authors: Sechler, M.; McIntosh, S. W.; Tian, H.; De Pontieu, B.
Bibcode: 2012ASPC..455..361S
Altcode: 2012arXiv1201.5028S
Using joint observations from Hinode/EIS and the Atmospheric Imaging
Array (AIA) on the Solar Dynamics Observatory (SDO) we explore the
asymmetry of coronal EUV line profiles. We find that asymmetries exist
in all of the spectral lines studied, and not just the hottest lines
as has been recently reported in the literature. Those asymmetries
indicate that the velocities of the second emission component are
relatively consistent across temperature and consistent with the
apparent speed at which material is being inserted from the lower
atmosphere that is visible in the SDO/AIA images as propagating coronal
disturbances. Further, the observed asymmetries are of similar magnitude
(a few percent) and width (determined from the RB analysis) across the
temperature space sampled and in the small region studied. Clearly,
there are two components of emission in the locations where the
asymmetries are identified in the RB analysis, their characteristics
are consistent with those determined from the SDO/AIA data. There is
no evidence from our analysis that this second component is broader
than the main component of the line.
Title: Two Components of the Coronal Emission Revealed by Both
Spectroscopic and Imaging Observations
Authors: Tian, H.; McIntosh, S. W.; De Pontieu, B.
Bibcode: 2012ASPC..456...97T
Altcode:
X-ray and EUV imaging observations often reveal quasi-periodic
propagating disturbances along the fan-like structures at edges of
active regions. These disturbances have historically been interpreted
as being signatures of slow-mode magnetoacoustic waves propagating
into the corona. Recent spectroscopic observations have revealed
the ubiquitous presence of blueward asymmetries of EUV emission line
profiles. Such asymmetries suggest that there are at least two emission
components: a primary component accounting for the background emission
and a secondary component associated with high-speed upflows. Thus, a
single Gaussian fit can not reflect the real physics here. Through joint
imaging and spectroscopic observations, we find a clear association
of the secondary component with the upward propagating disturbances
and conclude that they are more likely to be real plasma outflows
(small-scale recurring jets) rather than slow waves. These outflows
may result from impulsive heating processes in the lower transition
region or chromosphere and could be an efficient means to provide hot
plasma into the corona and possibly also solar wind.
Title: On the Doppler Velocity of Emission Line Profiles Formed in
the "Coronal Contraflow" that Is the Chromosphere-Corona Mass Cycle
Authors: McIntosh, Scott W.; Tian, Hui; Sechler, Marybeth; De Pontieu,
Bart
Bibcode: 2012ApJ...749...60M
Altcode: 2012arXiv1202.1248M
This analysis begins to explore the complex chromosphere-corona mass
cycle using a blend of imaging and spectroscopic diagnostics. Single
Gaussian fits (SGFs) to hot emission line profiles (formed above 1 MK)
at the base of coronal loop structures indicate material blueshifts
of 5-10 km s-1, while cool emission line profiles (formed
below 1 MK) yield redshifts of a similar magnitude—indicating, to
zeroth order, that a temperature-dependent bifurcating flow exists
on coronal structures. Image sequences of the same region reveal
weakly emitting upward propagating disturbances in both hot and cool
emission with apparent speeds of 50-150 km s-1. Spectroscopic
observations indicate that these propagating disturbances produce a weak
emission component in the blue wing at commensurate speed, but that they
contribute only a few percent to the (ensemble) emission line profile
in a single spatio-temporal resolution element. Subsequent analysis of
imaging data shows material "draining" slowly (~10 km s-1)
out of the corona, but only in the cooler passbands. We interpret
the draining as the return flow of coronal material at the end of
the complex chromosphere-corona mass cycle. Further, we suggest that
the efficient radiative cooling of the draining material produces a
significant contribution to the red wing of cool emission lines that is
ultimately responsible for their systematic redshift as derived from an
SGF when compared to those formed in hotter (conductively dominated)
domains. The presence of counterstreaming flows complicates the line
profiles, their interpretation, and asymmetry diagnoses, but allows
a different physical picture of the lower corona to develop.
Title: What can We Learn about Solar Coronal Mass Ejections,
Coronal Dimmings, and Extreme-ultraviolet Jets through Spectroscopic
Observations?
Authors: Tian, Hui; McIntosh, Scott W.; Xia, Lidong; He, Jiansen;
Wang, Xin
Bibcode: 2012ApJ...748..106T
Altcode: 2012arXiv1201.2204T
Solar eruptions, particularly coronal mass ejections (CMEs) and
extreme-ultraviolet (EUV) jets, have rarely been investigated with
spectroscopic observations. We analyze several data sets obtained
by the EUV Imaging Spectrometer on board Hinode and find various
types of flows during CMEs and jet eruptions. CME-induced dimming
regions are found to be characterized by significant blueshift and
enhanced line width by using a single Gaussian fit, while a red-blue
(RB) asymmetry analysis and an RB-guided double Gaussian fit of
the coronal line profiles indicate that these are likely caused by
the superposition of a strong background emission component and a
relatively weak (~10%), high-speed (~100 km s-1) upflow
component. This finding suggests that the outflow velocity in the
dimming region is probably of the order of 100 km s-1, not
~20 km s-1 as reported previously. These weak, high-speed
outflows may provide a significant amount of mass to refill the corona
after the eruption of CMEs, and part of them may experience further
acceleration and eventually become solar wind streams that can serve
as an additional momentum source of the associated CMEs. Density and
temperature diagnostics of the dimming region suggest that dimming
is primarily an effect of density decrease rather than temperature
change. The mass losses in dimming regions as estimated from different
methods are roughly consistent with each other, and they are 20%-60%
of the masses of the associated CMEs. With the guide of RB asymmetry
analysis, we also find several temperature-dependent outflows (speed
increases with temperature) immediately outside the (deepest) dimming
region. These outflows may be evaporation flows that are caused by
the enhanced thermal conduction or nonthermal electron beams along
reconnecting field lines, or induced by the interaction between the
opened field lines in the dimming region and the closed loops in
the surrounding plage region. In an erupted CME loop and an EUV jet,
profiles of emission lines formed at coronal and transition region
temperatures are found to exhibit two well-separated components, an
almost stationary component accounting for the background emission and
a highly blueshifted (~200 km s-1) component representing
emission from the erupting material. The two components can easily
be decomposed through a double Gaussian fit, and we can diagnose the
electron density, temperature, and mass of the ejecta. Combining the
speed of the blueshifted component and the projected speed of the
erupting material derived from simultaneous imaging observations,
we can calculate the real speed of the ejecta.
Title: Spectroscopic observations of coronal mass ejections, coronal
dimming and EUV jets
Authors: Tian, Hui; McIntosh, Scott W.
Bibcode: 2012decs.confE..10T
Altcode:
Solar eruptions, particularly coronal mass ejections (CMEs) and
extreme-ultraviolet (EUV) jets, have rarely been investigated with
spectroscopic observations. We analyze several data sets obtained by
the EUV Imaging Spectrometer onboard Hinode and find various types of
flows during CMEs and jet eruptions. CME-induced dimming regions are
found to be characterized by significant blueshift and enhanced line
width by using a single Gaussian fit. While a red-blue (RB) asymmetry
analysis and a RB-guided double Gaussian fit of the coronal line
profiles indicate that these are likely caused by the superposition
of a strong background emission component and a relatively weak ( 10%)
high-speed ( 100 km s-1) upflow component. This finding suggests that
the outflow velocity in the dimming region is probably of the order
of 100 km s-1, not 20 km s-1 as reported previously. Density and
temperature diagnostics of the dimming region suggest that dimming
is primarily an effect of density decrease rather than temperature
change. The mass losses in dimming regions as estimated from different
methods are roughly consistent with each other and they are 20%-60%
of the masses of the associated CMEs. With the guide of RB asymmetry
analysis, we also find several temperature-dependent outflows (speed
increases with temperature) immediately outside the (deepest) dimming
region. These outflows may be evaporation flows which are caused by
the enhanced thermal conduction or nonthermal electron beams along
reconnecting field lines, or induced by the interaction between the
opened field lines in the dimming region and the closed loops in
the surrounding plage region. In an erupted CME loop and an EUV jet,
profiles of emission lines formed at coronal and transition region
temperatures are found to exhibit two well-separated components, an
almost stationary component accounting for the background emission
and a highly blueshifted ( 200 km s-1) component representing
emission from the erupting material. The two components can easily
be decomposed through a double Gaussian fit and we can diagnose the
electron density, temperature and mass of the ejecta. Combining the
speed of the blueshifted component and the projected speed of the
erupting material derived from simultaneous imaging observations,
we can calculate the real speed of the ejecta.
Title: The Chromosphere and Prominence Magnetometer
Authors: de Wijn, Alfred; Bethge, Christian; McIntosh, Scott; Tomczyk,
Steven; Casini, Roberto
Bibcode: 2012decs.confE..63D
Altcode:
ChroMag is an imaging polarimeter designed to measure on-disk
chromosphere and off-disk prominence magnetic fields using the
spectral lines of He I (587.6 and 1083 nm). It is part of the planned
CoSMO suite, which includes two more instruments: a large 1.5-m
refracting coronagraph for coronal magnetic field measurements, and
the K-Coronagraph for measurement of the coronal density. ChroMag
will provide insights in the energetics of the solar atmosphere,
how prominences are formed, and how energy is stored and released
in the magnetic field structure of the atmosphere. An essential
part of the ChroMag program is a commitment to develop and provide
community access to the "inversion" tools necessary to interpret the
measurements and derive the magneto-hydrodynamic parameters of the
plasma. A prototype instrument is currently under construction at the
High Altitude Observatory. We will present an overview of the ChroMag
instrument concept, target science, and prototype status.
Title: Synoptic measurements of chromospheric and prominence magnetic
fields with the Chromosphere Magnetometer ChroMag
Authors: Bethge, C.; de Wijn, A. G.; McIntosh, S. W.; Tomczyk, S.;
Casini, R.
Bibcode: 2012decs.confE..62B
Altcode:
The Chromosphere Magnetometer is part of the Coronal Solar Magnetism
Observatory (COSMO) proposed by the High Altitude Observatory (HAO)
in collaboration with the University of Hawaii and the University of
Michigan. Routine measurements of chromospheric and coronal magnetic
fields are vital if we want to understand fundamental problems like
the energy and mass balance of the corona, the onset and acceleration
of the solar wind, the emergence of CMEs, and how these phenomena
influence space weather. ChroMag is designed as a Lyot-type filtergraph
polarimeter with an FOV of 2.5 solar radii, i.e., it will be capable of
both on-disk and off-limb polarimetric measurements. The Lyot filter
- currently being built at HAO - is tunable at a fast rate, which
allows to determine line-of-sight velocities. This will be done in
the spectral lines of H alpha at 656.3 nm, Fe I 617.3 nm, Ca II 854.2
nm, He I 587.6 nm, and He I 1083.0 nm at a high cadence of less than
1 minute, and at a moderate spatial resolution of 2 arcsec. ChroMag
data will be freely accessible to the community, along with inversion
tools for an easier interpretation of the data. A protoype instrument
for ChroMag is currently being assembled at HAO and is expected to
perform first measurements at the Boulder Mesa Lab in Summer 2012. We
present an overview of the ChroMag instrument and the current status
of the protoype.
Title: Temperature dependence of EUV line parameters in network and
internetwork regions for quiet Sun and coronal hole
Authors: Wang, Xin; McIntosh, Scott W.; Tian, Hui
Bibcode: 2012decs.confE.107W
Altcode:
By using SUMER observations, we study the temperature dependence
of the intensity contrast, Doppler shift, non-thermal width and
profile asymmetry in network and internetwork regions for both the
quiet Sun (QS) and coronal holes (CHs). In network regions, most of
the transition region (TR) line profiles are more red shifted (by
0-5km/s) and narrower (by 1-6km/s) in QS than in CH. In the network,
the RB asymmetries of all the selected TR and coronal line profiles
are smaller (more blueward) in CH than in QS. While in the interwork
region the difference disappears. In addition, we also systematically
investigate differential emission measures (DEM) and electron densities
and found different behavior in network and internetwork regions by
using joint observations of SUMER and EIS. Our results suggest that
the mass cycle between the chromosphere and corona mainly occurs in
the network and one needs to separate network and internetwork when
discussing thermal and dynamic properties of the solar atmosphere.
Title: Observational Evidence of Magnetic Waves in the Solar
Atmosphere
Authors: McIntosh, Scott W.
Bibcode: 2012decs.confE..86M
Altcode:
The observational evidence in supporting the presence of magnetic waves
in the outer solar atmosphere is growing rapidly - we will discuss
recent observations and place them in context with salient observations
made in the past. While the clear delineation of these magnetic wave
"modes" is unclear, much can be learned about the environment in which
they originated and possibly how they are removed from the system from
the observations. Their diagnostic power is, as yet, untapped and their
energy content (both as a mechanical source for the heating of coronal
material and acceleration of the solar wind) remains in question,
but can be probed observationally - raising challenges for modeling
efforts. We look forward to the IRIS mission by proposing some sample
observing sequences to help resolve some of the zoological issues
present in the literature.
Title: Estimating the (Dark) Energy Content of the Solar Corona
Authors: McIntosh, Scott W.; De Pontieu, Bart
Bibcode: 2012decs.confE.102M
Altcode:
Exploiting the recent discovery of ubiquitous low-frequency (3-5mHz)
Alfvénic waves in the solar chromosphere (with Hinode/SOT), and corona
(with the ground-based CoMP and SDO/AIA) we report on the Alfvénic wave
energy content of the corona using a blend of observational data and
a simple forward model of Alfvénic wave propagation. We explore the
apparent discrepancy in the resolved coronal Alfvénic wave amplitude
( 0.5km/s) measure by CoMP compared to those of the Hinode and SDO
near the limb ( 20km/s).We see that the temporal invariance of the
CoMP coronal non-thermal line widths ably capture the presence of the
hidden, or dark, energy content in the corona. Exploiting the fact
that the magnetic field permeating the corona is ubiquitously carrying
Alfvénic motions of non-negligible amplitude we construct a simple
model of wave propagation using the SOT and AIA measurements as strong
constraints. This model reproduces the key spectroscopic measurements
of the CoMP observations and allows us to place preliminary constraints
on the impact of the coronal magnetic filling factor, the input wave
spectrum, the dissipation on the wave motions observed, in addition
to their energy content.
Title: The Connection of Type II Spicules to the Corona
Authors: Judge, Philip G.; de Pontieu, Bart; McIntosh, Scott W.;
Olluri, Kosovare
Bibcode: 2012ApJ...746..158J
Altcode: 2011arXiv1112.6174D; 2011arXiv1112.6174J
We examine the hypothesis that plasma associated with "Type II"
spicules is heated to coronal temperatures, and that the upward
moving hot plasma constitutes a significant mass supply to the solar
corona. One-dimensional hydrodynamical models including time-dependent
ionization are brought to bear on the problem. These calculations
indicate that heating of field-aligned spicule flows should produce
significant differential Doppler shifts between emission lines formed
in the chromosphere, transition region, and corona. At present,
observational evidence for the computed 60-90 km s-1
differential shifts is weak, but the data are limited by difficulties
in comparing the proper motion of Type II spicules with spectral
and kinematic properties of an associated transition region and
coronal emission lines. Future observations with the upcoming infrared
interferometer spectrometer instrument should clarify if Doppler shifts
are consistent with the dynamics modeled here.
Title: Solar Cycle Variations in the Elemental Abundance of Helium
and Fractionation of Iron in the Fast Solar Wind - Indicators of an
Evolving Energetic Release of Mass from the Lower Solar Atmosphere
Authors: Kiefer, K. K.; Mcintosh, S. W.; Leamon, R. J.; Kasper, J. C.;
Stevens, M. L.
Bibcode: 2011AGUFMSH21B1915K
Altcode:
We present and discuss the strong correspondence between evolution of
the emission length scale in the lower transition region and in situ
measurements of the fast solar wind composition during this most recent
solar minimum. We combine recent analyses demonstrating the variance
in the (supergranular) network emission length scale measured by SOHO
(and STEREO) with that of the Helium abundance (from WIND) and the
degree of Iron fractionation in the solar wind (from the ACE and Ulysses
spacecrafts). The net picture developing is one where a decrease in the
Helium abundance and the degree of fractionation (approaching values
expected of the photosphere) in the fast wind indicate a significant
change in the process loading material into the fast solar wind during
the recent solar minimum. This result is compounded by a study of the
Helium abundance during the space age using the NASA OMNI database
which shows a slowly decaying amount of Helium being driven into the
heliosphere over the course of several solar cycles.
Title: Segmentation of EUV spectroheliograms to track and measure
solar EUVI variability within a solar cycle
Authors: Martinez-Galarce, D. S.; Slater, G. L.; Mcintosh, S. W.
Bibcode: 2011AGUFMGC23A0929M
Altcode:
Solar Extreme Ultraviolet Irradiation (EUVI) is known to be the
primary source of energy that drives the photochemistry, ionization and
heating of the Earth's upper atmosphere above ~ 100 km, contributing
to Earth's delicate heating balance and therefore its weather, and
over longer periods, its climate. Changes in atmospheric density
caused by EUVI (e.g. a thickening of the ionosphere) also affect
space-based satellites by "dragging" them to lower orbits and lowering
their expected operational lifetimes. A priori knowledge of EUVI
variation in conjunction with satellite tracking models would assist
satellite operators in countering such affects. Therefore, accurate
determination of EUVI is useful for weather, climate and geospace
modelers wishing to improve their prediction of solar EUVI effects
on the Earth's thermosphere, ionosphere and atmospheric composition,
as well as how it affects and modulates Earth weather and climate. It
is known that the source of EUVI is the solar atmosphere, where this
radiation is produced by varying ionic species of plasmas that lie at
temperatures ranging from ~10^4-10^7 K. However, our understanding of
the physical mechanisms that heat these plasmas to such temperatures
continues to be an active area of investigation and debate, and
to understand long-term EUVI effects on Earth and human engineered
assets, it is necessary to see what, if any, variability is observed
in the solar atmosphere that may be associated with terrestrial
effects. Herein, we show initial results from the application of
the Coronal Image Segmentation Algorithm (CorISA) to the SoHO EIT
database to identify and segment solar features observed in EIT narrow
bandpass spectroheliograms. These spectroheliograms were recorded at
EUV wavelengths whose bandpasses are centered at 171, 195, 284 and
304 Å to observe line emission produced by plasmas: Fe IX/X, Fe XII,
Fe XV and He II, respectively. The EIT database currently consists of
observations covering a period of ~1.3 solar cycles (~16 years). Using
this segmented imaging approach the goal of the study is to determine
solar EUVI variability observed in each EIT bandpass, as a function of
areal identification (e.g., active vs. coronal hole EUV variability),
over the entire period of observations.
Title: The highest cosmic ray fluxes ever recorded: What happened
to the earth's deflector shield?
Authors: Leamon, R. J.; Mcintosh, S. W.; Burkepile, J.; Sitongia,
L.; Markel, R. S.; Gurman, J. B.; Olive, J.
Bibcode: 2011AGUFMSH23D..08L
Altcode:
The summer of 2009 saw the largest cosmic ray flux ever measured
at 1AU. Observed by neutron monitors this solar minimum flux was
6% larger than that of the last solar minimum in 1996, and 4%
larger than the previous high of the space age. Clearly, something
dramatically affected the cosmic ray "deflector shield" of the Earth
this time around, but what was it? Using a combination of serendipitous
observations made by the solid state recorder of the SOHO spacecraft,
an analysis of SOHO/MDI magnetograms combined with SOHO/EIT and SDO/AIA
coronal imaging, we deduce that a pronounced north-south asymmetry
in the meridional circulation flow resulted in the evolution of
the photospheric magnetic to a prolonged prevalence of the negative
magnetic polarity in the equatorial region that were the root cause
of the observed cosmic ray flux increase. The negative sign, weakness
and low rigidity of the interplanetary magnetic field, driven by the
excess of open magnetic flux resulting from the flow asymmetry in the
solar interior, enabled more cosmic rays of the energy range measured
at Earth to creep into our atmosphere than previously measured.
Title: The Whole Heliosphere Interval in the Context of a Long and
Structured Solar Minimum: An Overview from Sun to Earth
Authors: Gibson, S. E.; de Toma, G.; Emery, B.; Riley, P.; Zhao, L.;
Elsworth, Y.; Leamon, R. J.; Lei, J.; McIntosh, S.; Mewaldt, R. A.;
Thompson, B. J.; Webb, D.
Bibcode: 2011SoPh..274....5G
Altcode: 2011SoPh..tmp..427G
Throughout months of extremely low solar activity during the recent
extended solar-cycle minimum, structural evolution continued to be
observed from the Sun through the solar wind and to the Earth. In
2008, the presence of long-lived and large low-latitude coronal holes
meant that geospace was periodically impacted by high-speed streams,
even though solar irradiance, activity, and interplanetary magnetic
fields had reached levels as low as, or lower than, observed in past
minima. This time period, which includes the first Whole Heliosphere
Interval (WHI 1: Carrington Rotation (CR) 2068), illustrates the
effects of fast solar-wind streams on the Earth in an otherwise quiet
heliosphere. By the end of 2008, sunspots and solar irradiance had
reached their lowest levels for this minimum (e.g., WHI 2: CR 2078),
and continued solar magnetic-flux evolution had led to a flattening
of the heliospheric current sheet and the decay of the low-latitude
coronal holes and associated Earth-intersecting high-speed solar-wind
streams. As the new solar cycle slowly began, solar-wind and geospace
observables stayed low or continued to decline, reaching very low
levels by June - July 2009. At this point (e.g., WHI 3: CR 2085) the
Sun-Earth system, taken as a whole, was at its quietest. In this article
we present an overview of observations that span the period 2008 -
2009, with highlighted discussion of CRs 2068, 2078, and 2085. We show
side-by-side observables from the Sun's interior through its surface and
atmosphere, through the solar wind and heliosphere and to the Earth's
space environment and upper atmosphere, and reference detailed studies
of these various regimes within this topical issue and elsewhere.
Title: Lyman Alpha Spicule Observatory (LASO)
Authors: Chamberlin, P. C.; Allred, J. C.; Airapetian, V.; Gong, Q.;
Mcintosh, S. W.; De Pontieu, B.; Fontenla, J. M.
Bibcode: 2011AGUFMSH33B2064C
Altcode:
The Lyman Alpha Spicule Observatory (LASO) sounding rocket will observe
small-scale eruptive events called "Rapid Blue-shifted Events" (RBEs)
[Rouppe van der Voort et al., 2009], the on-disk equivalent of Type-II
spicules, and extend observations that explore their role in the solar
coronal heating problem [De Pontieu et al., 2011]. LASO utilizes a
new and novel optical design to simultaneously observe two spatial
dimensions at 4.2" spatial resolution (2.1" pixels) over a 2'x2' field
of view with high spectral resolution of 66mÅ (33mÅ pixels) across a
broad 20Å spectral window. This spectral window contains three strong
chromospheric and transition region emissions and is centered on the
strong Hydrogen Lyman-α emission at 1216Å. This instrument makes
it possible to obtain new data crucial to the physical understanding
of these phenomena and their role in the overall energy and momentum
balance from the upper chromosphere to lower corona. LASO was submitted
March 2011 in response to the ROSES SHP-LCAS call.
Title: Two Components of the Coronal Emission Revealed by
Extreme-Ultraviolet Spectroscopic Observations
Authors: Tian, H.; Mcintosh, S. W.; De Pontieu, B.; Martinez-Sykora,
J.; Wang, X.; Sechler, M.
Bibcode: 2011AGUFMSH33A2027T
Altcode:
Recent spectroscopic observations have revealed the ubiquitous presence
of blueward asymmetries of emission lines formed in the solar corona
and transition region. These asymmetries are most prominent in loop
footpoint regions, where a clear correlation of the asymmetry with the
Doppler shift and line width determined from the single-Gaussian fit
is found. Such asymmetries suggest at least two emission components: a
primary component accounting for the background emission and a secondary
component associated with high-speed upflows. The latter has been
proposed to play a vital role in the coronal heating process and there
is no agreement on its properties. Here we slightly modify the initially
developed technique of red-blue (RB) asymmetry analysis and apply it to
both artificial spectra and spectra observed by the Extreme-ultraviolet
Imaging Spectrometer on board Hinode, and demonstrate that the secondary
component usually contributes a few percent of the total emission, has
a velocity ranging from 50 to 150 km/s, and a Gaussian width comparable
to that of the primary one in loop footpoint regions. The results of
the RB asymmetry analysis are then used to guide a double-Gaussian fit
and we find that the obtained properties of the secondary component
are generally consistent with those obtained from the RB asymmetry
analysis. Through a comparison of the location, relative intensity,
and velocity distribution of the blueward secondary component with
the properties of the upward propagating disturbances revealed in
simultaneous images from the Atmospheric Imaging Assembly on board
the Solar Dynamics Observatory, we find a clear association of the
secondary component with the propagating disturbances.
Title: Solar Cycle Variations in the Elemental Abundance of Helium
and Fractionation of Iron in the Fast Solar Wind: Indicators of an
Evolving Energetic Release of Mass from the Lower Solar Atmosphere
Authors: McIntosh, Scott W.; Kiefer, Kandace K.; Leamon, Robert J.;
Kasper, Justin C.; Stevens, Michael L.
Bibcode: 2011ApJ...740L..23M
Altcode: 2011arXiv1109.1408M
We present and discuss the strong correspondence between evolution of
the emission length scale in the lower transition region and in situ
measurements of the fast solar wind composition during the most recent
solar minimum. We combine recent analyses demonstrating the variance
in the (supergranular) network emission length scale measured by the
Solar and Heliospheric Observatory (and STEREO) with that of the helium
abundance (from Wind) and the degree of iron fractionation in the solar
wind (from the Advanced Composition Explorer and Ulysses). The net
picture developing is one where a decrease in the helium abundance
and the degree of iron fractionation (approaching values expected
of the photosphere) in the fast wind indicate a significant change
in the process loading material into the fast solar wind during the
recent solar minimum. This result is compounded by a study of the
helium abundance during the space age using the NASA OMNI database,
which shows a slowly decaying amount of helium being driven into the
heliosphere over the course of several solar cycles.
Title: Two Components of the Solar Coronal Emission Revealed by
Extreme-ultraviolet Spectroscopic Observations
Authors: Tian, Hui; McIntosh, Scott W.; De Pontieu, Bart;
Martínez-Sykora, Juan; Sechler, Marybeth; Wang, Xin
Bibcode: 2011ApJ...738...18T
Altcode: 2011arXiv1106.1141T
Recent spectroscopic observations have revealed the ubiquitous presence
of blueward asymmetries of emission lines formed in the solar corona
and transition region. These asymmetries are most prominent in loop
footpoint regions, where a clear correlation of the asymmetry with the
Doppler shift and line width determined from the single-Gaussian fit
is found. Such asymmetries suggest at least two emission components: a
primary component accounting for the background emission and a secondary
component associated with high-speed upflows. The latter has been
proposed to play a vital role in the coronal heating process and there
is no agreement on its properties. Here we slightly modify the initially
developed technique of red-blue (RB) asymmetry analysis and apply it to
both artificial spectra and spectra observed by the Extreme-ultraviolet
Imaging Spectrometer on board Hinode, and demonstrate that the secondary
component usually contributes a few percent of the total emission,
and has a velocity ranging from 50 to 150 km s-1 and a
Gaussian width comparable to that of the primary one in loop footpoint
regions. The results of the RB asymmetry analysis are then used to
guide a double-Gaussian fit and we find that the obtained properties of
the secondary component are generally consistent with those obtained
from the RB asymmetry analysis. Through a comparison of the location,
relative intensity, and velocity distribution of the blueward secondary
component with the properties of the upward propagating disturbances
revealed in simultaneous images from the Atmospheric Imaging Assembly
on board the Solar Dynamics Observatory, we find a clear association
of the secondary component with the propagating disturbances.
Title: Observation of High-speed Outflow on Plume-like
Structures of the Quiet Sun and Coronal Holes with Solar Dynamics
Observatory/Atmospheric Imaging Assembly
Authors: Tian, Hui; McIntosh, Scott W.; Habbal, Shadia Rifai; He,
Jiansen
Bibcode: 2011ApJ...736..130T
Altcode: 2011arXiv1105.3119T
Observations from the Atmospheric Imaging Assembly onboard the Solar
Dynamics Observatory reveal ubiquitous episodic outflows (jets)
with an average speed around 120 km s-1 at temperatures
often exceeding a million degree in plume-like structures, rooted in
magnetized regions of the quiet solar atmosphere. These outflows are not
restricted to the well-known plumes visible in polar coronal holes, but
are also present in plume-like structures originating from equatorial
coronal holes and quiet-Sun (QS) regions. Outflows are also visible
in the "inter-plume" regions throughout the atmosphere. Furthermore,
the structures traced out by these flows in both plume and inter-plume
regions continually exhibit transverse (Alfvénic) motion. Our finding
suggests that high-speed outflows originate mainly from the magnetic
network of the QS and coronal holes (CHs), and that the plume flows
observed are highlighted by the denser plasma contained therein. These
outflows might be an efficient means to provide heated mass into the
corona and serve as an important source of mass supply to the solar
wind. We demonstrate that the QS plume flows can sometimes significantly
contaminate the spectroscopic observations of the adjacent CHs—greatly
affecting the Doppler shifts observed, thus potentially impacting
significant investigations of such regions.
Title: The U.S. Eclipse Megamovie in 2017: a white paper on a unique
outreach event
Authors: Hudson, Hugh S.; McIntosh, Scott W.; Habbal, Shadia R.;
Pasachoff, Jay M.; Peticolas, Laura
Bibcode: 2011arXiv1108.3486H
Altcode:
Totality during the solar eclipse of 2017 traverses the entire breadth
of the continental United States, from Oregon to South Carolina. It thus
provides the opportunity to assemble a very large number of images,
obtained by amateur observers all along the path, into a continuous
record of coronal evolution in time; totality lasts for an hour and
a half over the continental U.S. While we describe this event here as
an opportunity for public education and outreach, such a movie -with
very high time resolution and extending to the chromosphere - will also
contain unprecedented information about the physics of the solar corona.
Title: Observation of High-speed Outflow on Plume-like Structures
of the Quiet Sun and Coronal Holes with SDO/AIA
Authors: Tian, Hui; McIntosh, Scott W.; Habbal, Shadia Rifal; He,
Jiansen
Bibcode: 2011shin.confE.161T
Altcode:
Observations from the Atmospheric Imaging Assembly (AIA) onboard the
Solar Dynamics Observatory (SDO) reveal ubiquitous episodic outflows
(jets) with an average speed around 120 km s-1 at temperatures
often exceeding a million degree in plume-like structures, rooted in
magnetized regions of the quiet solar atmosphere. These outflows are not
restricted to the well-known plumes visible in polar coronal holes, but
are also present in plume-like structures originating from equatorial
coronal holes and quiet-Sun regions. Outflows are also visible in
the "interplume" regions throughout the atmosphere. Furthermore, the
structures traced out by these flows in both plume and inter-plume
regions continually exhibit transverse (Alfvéenic) motion. Our finding
suggests that high-speed outflows originate mainly from the magnetic
network of the quiet Sun and coronal holes, and that the plume flows
observed are highlighted by the denser plasma contained therein. These
outflows might be an efficient means to provide heated mass into the
corona and serve as an important source of mass supply to the solar
wind. We demonstrate that the quiet-Sun plume flows can sometimes
significantly contaminate the spectroscopic observations of the adjacent
coronal holes - greatly affecting the Doppler shifts observed, thus
potentially impacting significant investigations of such regions.
Title: Alfvénic waves with sufficient energy to power the quiet
solar corona and fast solar wind
Authors: McIntosh, Scott W.; de Pontieu, Bart; Carlsson, Mats;
Hansteen, Viggo; Boerner, Paul; Goossens, Marcel
Bibcode: 2011Natur.475..477M
Altcode:
Energy is required to heat the outer solar atmosphere to millions of
degrees (refs 1, 2) and to accelerate the solar wind to hundreds of
kilometres per second (refs 2-6). Alfvén waves (travelling oscillations
of ions and magnetic field) have been invoked as a possible mechanism
to transport magneto-convective energy upwards along the Sun's magnetic
field lines into the corona. Previous observations of Alfvénic waves
in the corona revealed amplitudes far too small (0.5kms-1)
to supply the energy flux (100-200Wm-2) required to
drive the fast solar wind or balance the radiative losses of the
quiet corona. Here we report observations of the transition region
(between the chromosphere and the corona) and of the corona that
reveal how Alfvénic motions permeate the dynamic and finely structured
outer solar atmosphere. The ubiquitous outward-propagating Alfvénic
motions observed have amplitudes of the order of 20kms-1 and
periods of the order of 100-500s throughout the quiescent atmosphere
(compatible with recent investigations), and are energetic enough to
accelerate the fast solar wind and heat the quiet corona.
Title: Lyman Alpha Spicule Observatory (LASO)
Authors: Chamberlin, Phillip C.; Allred, J.; Airapetian, V.; Gong,
Q.; Fontenla, J.; McIntosh, S.; de Pontieu, B.
Bibcode: 2011SPD....42.1506C
Altcode: 2011BAAS..43S.1506C
The Lyman Alpha Spicule Observatory (LASO) sounding rocket will observe
small-scale eruptive events called "Rapid Blue-shifted Events” (RBEs),
the on-disk equivalent of Type-II spicules, and extend observations that
explore their role in the solar coronal heating problem. LASO utilizes
a new and novel optical design to simultaneously observe two spatial
dimensions at 4.2" spatial resolution (2.1” pixels) over a 2'x2'
field of view with high spectral resolution of 66mÅ (33mÅ pixels)
across a broad 20Å spectral window. This spectral window contains three
strong chromospheric and transition region emissions and is centered on
the strong Hydrogen Lyman-α emission at 1216Å. This instrument makes
it possible to obtain new data crucial to the physical understanding
of these phenomena and their role in the overall energy and momentum
balance from the upper chromosphere to lower corona. LASO was submitted
March 2011 in response to the ROSES SHP-LCAS call.
Title: What do Spectral Line Profile Asymmetries Tell us About the
Solar Atmosphere?
Authors: Martínez-Sykora, Juan; De Pontieu, Bart; Hansteen, Viggo;
McIntosh, Scott W.
Bibcode: 2011ApJ...732...84M
Altcode:
Recently, analysis of solar spectra obtained with the EUV Imaging
Spectrograph (EIS) onboard the Hinode satellite has revealed the
ubiquitous presence of asymmetries in transition region (TR) and coronal
spectral line profiles. These asymmetries have been observed especially
at the footpoints of coronal loops and have been associated with strong
upflows that may play a significant role in providing the corona with
hot plasma. Here, we perform a detailed study of the various processes
that can lead to spectral line asymmetries, using both simple forward
models and state-of-the-art three-dimensional radiative MHD simulations
of the solar atmosphere using the Bifrost code. We describe a novel
technique to determine the presence and properties of faint secondary
components in the wings of spectral line profiles. This method is based
on least-squares fitting of observed so-called R(ed)B(lue) asymmetry
profiles with pre-calculated RB asymmetry profiles for a wide variety
of secondary component properties. We illustrate how this method could
be used to perform reliable double Gaussian fits that are not over- or
under-constrained. We also find that spectral line asymmetries appear
in TR and coronal lines that are synthesized from our three-dimensional
MHD simulations. Our models show that the spectral asymmetries are a
sensitive measure of the velocity gradient with height in the TR of
coronal loops. The modeled TR shows a large gradient of velocity that
increases with height: this occurs as a consequence of ubiquitous,
episodic heating at low heights in the model atmosphere. We show
that the contribution function of spectral lines as a function of
temperature is critical for sensitivity to velocity gradients and thus
line asymmetries: lines that are formed over a temperature range that
includes most of the TR are the most sensitive. As a result, lines from
lithium-like ions (e.g., O VI) are found to be the most sensitive to
line asymmetries. We compare the simulated line profiles directly with
line profiles observed in the quiet Sun with SOHO/SUMER and Hinode/EIS
and find that the shape of the profiles is very similar. In addition,
the simulated profiles with the strongest blueward asymmetry occur in
footpoint regions of coronal loops, which is similar to what we observe
with SUMER and EIS. There is however a significant discrepancy between
the simulations and observations: the simulated RB asymmetries are
an order of magnitude smaller than the observations. We discuss the
possible reasons for this discrepancy. In summary, our analysis shows
that observations of spectral line asymmetries can provide a powerful
new diagnostic to help constrain coronal heating models.
Title: Coupling The Dynamics Of The Outer Atmosphere With Atst
Authors: McIntosh, Scott W.
Bibcode: 2011SPD....42.0803M
Altcode: 2011BAAS..43S.0803M
ATST will permit the detailed observation of the physical processes that
drive the relentlessly violent energy release in the engine room of
the outer solar atmosphere. We will discuss the outstanding questions
that require the uniquely detailed observations that ATST's large
aperture and the first light instrumentation will make possible. We
will use contemporary observational cues to illustrate the potential
for discovery and understanding.
Title: Observing Evolution in the Supergranular Network Length Scale
During Periods of Low Solar Activity
Authors: McIntosh, Scott W.; Leamon, Robert J.; Hock, Rachel A.;
Rast, Mark P.; Ulrich, Roger K.
Bibcode: 2011ApJ...730L...3M
Altcode: 2011arXiv1102.0303M
We present the initial results of an observational study into the
variation of the dominant length scale of quiet solar emission:
supergranulation. The distribution of magnetic elements in the lanes
that from the network affects, and reflects, the radiative energy in
the plasma of the upper solar chromosphere and transition region at
the magnetic network boundaries forming as a result of the relentless
interaction of magnetic fields and convective motions of the Suns'
interior. We demonstrate that a net difference of ~0.5 Mm in the
supergranular emission length scale occurs when comparing observation
cycle 22/23 and cycle 23/24 minima. This variation in scale is
reproduced in the data sets of multiple space- and ground-based
instruments and using different diagnostic measures. By means of
extension, we consider the variation of the supergranular length
scale over multiple solar minima by analyzing a subset of the Mount
Wilson Solar Observatory Ca II K image record. The observations and
analysis presented provide a tantalizing look at solar activity in
the absence of large-scale flux emergence, offering insight into
times of "extreme" solar minimum and general behavior such as the
phasing and cross-dependence of different components of the spectral
irradiance. Given that the modulation of the supergranular scale
imprints itself in variations of the Suns' spectral irradiance, as well
as in the mass and energy transport into the entire outer atmosphere,
this preliminary investigation is an important step in understanding
the impact of the quiet Sun on the heliospheric system.
Title: The Spectroscopic Signature of Quasi-periodic Upflows in
Active Region Timeseries
Authors: Tian, Hui; McIntosh, Scott W.; De Pontieu, Bart
Bibcode: 2011ApJ...727L..37T
Altcode: 2010arXiv1012.5112T
Quasi-periodic propagating disturbances are frequently observed in
coronal intensity image sequences. These disturbances have historically
been interpreted as being the signature of slow-mode magnetoacoustic
waves propagating into the corona. The detailed analysis of Hinode EUV
Imaging Spectrometer (EIS) timeseries observations of an active region
(known to contain propagating disturbances) shows strongly correlated,
quasi-periodic, oscillations in intensity, Doppler shift, and line
width. No frequency doubling is visible in the latter. The enhancements
in the moments of the line profile are generally accompanied by a faint,
quasi-periodically occurring, excess emission at ~100 km s-1
in the blue wing of coronal emission lines. The correspondence of
quasi-periodic excess wing emission and the moments of the line profile
indicates that repetitive high-velocity upflows are responsible for
the oscillatory behavior observed. Furthermore, we show that the same
quasi-periodic upflows can be directly identified in a simultaneous
image sequence obtained by the Hinode X-Ray Telescope. These results
are consistent with the recent assertion of De Pontieu & McIntosh
that the wave interpretation of the data is not unique. Indeed, given
that several instances are seen to propagate along the direction of
the EIS slit that clearly shows in-phase, quasi-periodic variations of
intensity, velocity, width (without frequency doubling), and blue wing
enhanced emission, this data set would appear to provide a compelling
example that upflows are more likely to be the main cause of the
quasi-periodicities observed here, as such correspondences are hard
to reconcile in the wave paradigm.
Title: The Spectroscopic Footprint of the Fast Solar Wind
Authors: McIntosh, Scott W.; Leamon, Robert J.; De Pontieu, Bart
Bibcode: 2011ApJ...727....7M
Altcode: 2010arXiv1011.3066M
We analyze a large, complex equatorial coronal hole (ECH) and its
immediate surroundings with a focus on the roots of the fast solar
wind. We start by demonstrating that our ECH is indeed a source of the
fast solar wind at 1 AU by examining in situ plasma measurements in
conjunction with recently developed measures of magnetic conditions
of the photosphere, inner heliosphere, and the mapping of the solar
wind source region. We focus the bulk of our analysis on interpreting
the thermal and spatial dependence of the non-thermal line widths
in the ECH as measured by SOHO/SUMER by placing the measurements in
context with recent studies of ubiquitous Alfvén waves in the solar
atmosphere and line profile asymmetries (indicative of episodic heating
and mass loading of the coronal plasma) that originate in the strong,
unipolar magnetic flux concentrations that comprise the supergranular
network. The results presented in this paper are consistent with a
picture where a significant portion of the energy responsible for
the transport of heated mass into the fast solar wind is provided by
episodically occurring small-scale events (likely driven by magnetic
reconnection) in the upper chromosphere and transition region of the
strong magnetic flux regions that comprise the supergranular network.
Title: The Origins of Hot Plasma in the Solar Corona
Authors: De Pontieu, B.; McIntosh, S. W.; Carlsson, M.; Hansteen,
V. H.; Tarbell, T. D.; Boerner, P.; Martinez-Sykora, J.; Schrijver,
C. J.; Title, A. M.
Bibcode: 2011Sci...331...55D
Altcode:
The Sun's outer atmosphere, or corona, is heated to millions of degrees,
considerably hotter than its surface or photosphere. Explanations for
this enigma typically invoke the deposition in the corona of nonthermal
energy generated by magnetoconvection. However, the coronal heating
mechanism remains unknown. We used observations from the Solar Dynamics
Observatory and the Hinode solar physics mission to reveal a ubiquitous
coronal mass supply in which chromospheric plasma in fountainlike jets
or spicules is accelerated upward into the corona, with much of the
plasma heated to temperatures between ~0.02 and 0.1 million kelvin (MK)
and a small but sufficient fraction to temperatures above 1 MK. These
observations provide constraints on the coronal heating mechanism(s)
and highlight the importance of the interface region between photosphere
and corona.
Title: Automated detection of oscillatory signals in the solar
atmosphere: first results from SDO-AIA data
Authors: Ireland, J.; Young, C.; de Pontieu, B.; McIntosh, S. W.
Bibcode: 2010AGUFMSH11A1615I
Altcode:
Ireland et al. (2010) recently published a Bayesian-probability
based automated oscillation detection algorithm that finds areas
of the solar corona that support spatially contiguous oscillatory
signals. The major advantages of this algorithm are that it requires no
special knowledge of the noise characteristics or possible frequency
content of the signal, yet can calculate a probability that a time
series supports a signal in a given frequency range. This leads to
an algorithm which detects pixel areas where each pixel has a high
probability of supporting an oscillatory signal; however, the pixels
in these areas are not necessarily oscillating coherently. Earlier,
McIntosh et al. (2008) described another algorithm that first Fourier
filters time series data around a known frequency, and then calculates
the local coherence of the filtered signals in order to find areas
of the solar corona that exhibit locally strongly coherent signals
in narrow frequency ranges. The major advantages of this algorithm
are that locally coherent signals are found, and that it is simple
to calculate other parameters such as the phase speed. This leads to
an algorithm that finds groups of pixels that are coherent in narrow
frequency ranges, but that are not necessarily oscillatory in nature. In
this work we combine these two recently published automated oscillatory
signal detection algorithms and compare the new hybrid algorithm to the
progenitor algorithms. The new algorithm is applied to Advanced Imaging
Assembly (AIA) 94, 131, 171, 193, 211 and 335 Å data from the Solar
Dynamics Observatory, and we will give some first results. We also
discuss the use of this algorithm in a detection pipeline to provide
near-real time measurements of groups of coherently oscillating pixels.
Title: Ubiquitous Alfvenic Motions in Quiet Sun, Coronal Hole and
Active Region Corona
Authors: McIntosh, S. W.; de Pontieu, B.; Carlsson, M.; Hansteen,
V. H.; Sdo/Aia Mission Team
Bibcode: 2010AGUFMSH14A..01M
Altcode:
We use observations with AIA onboard SDO and report the discovery of
ubiquitous Alfvenic oscillations in the corona of quiet Sun, active
regions and coronal holes. These Alfvenic oscillations have significant
power, and seem to be connected to the chromospheric Alfvenic
oscillations previously reported with Hinode. We use Monte Carlo
simulations to determine the strength and periods of the waves. Using
unique joint observations of Hinode, the Solar Dynamics Observatory, and
HAO's CoMP instrument we study the excitation of transverse oscillations
as a function of space, time, and temperature. We will discuss the
energetic impact and diagnostic capabilities of this ever-present
process and how it can be used to build a more self-consistent picture
of energy transport into the inner heliosphere. Transverse Oscillations
Observed Above the Solar North Pole in the He II 304Å (bottom) and Fe
IX 171Å (top) channels. Studying the progression of such points with
altitude yields important information about wave propagation into the
magnetically open corona.
Title: First results for the Solar Ultraviolet Magnetograph
Investigation (SUMI)
Authors: Moore, R. L.; Cirtain, J. W.; West, E.; Kobayashi, K.;
Robinson, B.; Winebarger, A. R.; Tarbell, T. D.; de Pontieu, B.;
McIntosh, S. W.
Bibcode: 2010AGUFMSH11B1655M
Altcode:
On July 31, 2010 SUMI was launched to 286km above the White
Sands Missile Range to observe active region 11092. SUMI is a
spectro-polarimeter capable of measuring the spectrum for Mg II h &
k at 280 nm and C IV at 155 nm. Simultaneous observations with Hinode
and SDO provide total coverage of the region from the photosphere into
the corona, a very unique and original data set. We will present the
initial results from this first flight of the experiment and demonstrate
the utility of further observations by SUMI.
Title: The Highest Cosmic Ray Fluxes Ever Recorded: What Happened
to the Earth's Deflector Shield?
Authors: Burkepile, J.; McIntosh, S. W.; Gurman, J. B.; Leamon, R. J.
Bibcode: 2010AGUFMSH51B1676B
Altcode:
The summer of 2009 saw the largest cosmic ray flux ever measured at
Earth. Cosmic ray intensities in the 270-450 MeV/nucleon range were
nearly 20% larger than anything previously recorded. Clearly, something
dramatically affected the cosmic ray 'deflector shield' of the Earth
during the most recent solar activity minimum. We explore the cause
of this marked increase by examining properties of the global solar
magnetic field and conditions in the solar wind during the previous
solar minimum and compare these to previous solar cycles using in-situ
and remote sensing observations.
Title: The role of the chromosphere in filling the corona with hot
plasma (Invited)
Authors: de Pontieu, B.; McIntosh, S. W.; Carlsson, M.; Hansteen,
V. H.; Tarbell, T. D.; Boerner, P.; Martinez-Sykora, J.; Schrijver,
C. J.; Title, A. M.
Bibcode: 2010AGUFMSH21C..03D
Altcode:
We use coordinated observations from the Solar Dynamics Observatory
(SDO), Hinode and the Swedish Solar Telescope (SST) to show how
plasma is heated to coronal temperatures from its source in the
chromosphere. Our observations reveal a ubiquitous mass supply
for the solar corona in which chromospheric plasma is accelerated
upward into the corona with much of the plasma heated to transition
region temperatures, and a small, but significant fraction heated
to temperatures in excess of 1 million K. Our observations show,
for the first time, how chromospheric spicules, fountain-like jets
that have long been considered potential candidates for coronal
heating, are directly associated with heating of plasma to coronal
temperatures. These results provide strong physical constraints on
the mechanism(s) responsible for coronal heating and do not seem
compatible with current models. The association with chromospheric
spicules highlights the importance of the interface region between
the photosphere and corona to gain a full understanding of the coronal
heating problem.
Title: Line profile asymmetries in the transition region: models
and observations
Authors: Martinez-Sykora, J.; de Pontieu, B.; Hansteen, V. H.;
McIntosh, S. W.
Bibcode: 2010AGUFMSH31A1784M
Altcode:
Asymmetries in spectral line profiles provide a wealth of
information on the properties of the emitting plasma along the
line-of-sight. Asymmetries can be produced by the superposition
of profiles with different line-of-sight velocities and/or widths
resulting from the variation of the velocity and/or temperature from
emission sources along the line of sight. Spectral line asymmetries
from synthetic transition region and coronal lines constructed
from realistic 3D models appear similar to those observed with
Hinode/EIS. The simulations span the upper layer of the convection zone
to the lower corona and include horizontal magnetic flux emergence. We
use the state of the art Bifrost code to solve the full MHD equations
with non-grey and non-LTE radiative transfer and thermal conduction
along the magnetic field line. Here, we perform a detailed study of
the various physical, dynamical and observational processes that can
lead to spectral line asymmetries at the transition region footpoints
of loops in 3D radiative MHD simulations of the solar atmosphere and
compare these with observations. Our models show that the spectral
asymmetries are a sensitive measure of the velocity gradient with
height in the transition region of coronal loops. In our models the
TR shows a large gradient of velocity that increases with height:
this occurs as a natural consequence of ubiquitous, episodic heating
at low heights in the model atmosphere.
Title: Quasi-periodic Propagating Signals in the Solar Corona:
The Signature of Magnetoacoustic Waves or High-velocity Upflows?
Authors: De Pontieu, Bart; McIntosh, Scott W.
Bibcode: 2010ApJ...722.1013D
Altcode: 2010arXiv1008.5300D
Since the discovery of quasi-periodic propagating oscillations
with periods of order 3-10 minutes in coronal loops with TRACE and
SOHO/EIT (and later with STEREO/EUVI and Hinode/EIS), they have been
almost universally interpreted as evidence for propagating slow-mode
magnetoacoustic waves in the low plasma β coronal environment. Here
we show that this interpretation is not unique, and that for coronal
loops associated with plage regions (as opposed to sunspots), the
presence of magnetoacoustic waves may not be the only cause for the
observed quasi-periodicities. We focus instead on the ubiquitous, faint
upflows at 50-150 km s-1 that were recently discovered as
blueward asymmetries of spectral line profiles in footpoint regions
of coronal loops, and as faint disturbances propagating along coronal
loops in EUV/X-ray imaging time series. These faint upflows are most
likely driven from below and have been associated with chromospheric
jets that are (partially) rapidly heated to coronal temperatures at
low heights. These two scenarios (waves versus flows) are difficult to
differentiate using only imaging data, but careful analysis of spectral
line profiles indicates that faint upflows are likely responsible
for some of the observed quasi-periodic oscillatory signals in the
corona. We show that recent EIS measurements of intensity and velocity
oscillations of coronal lines (which had previously been interpreted
as direct evidence for propagating waves) are actually accompanied
by significant oscillations in the line width that are driven by a
quasi-periodically varying component of emission in the blue wing of
the line. This faint additional component of blue-shifted emission
quasi-periodically modulates the peak intensity and line centroid
of a single Gaussian fit to the spectral profile with the same small
amplitudes (respectively a few percent of background intensity and a
few km s-1) that were previously used to infer the presence
of slow-mode magnetoacoustic waves. Our results indicate that it
is possible that a significant fraction of the quasi-periodicities
observed with coronal imagers and spectrographs that have previously
been interpreted as propagating magnetoacoustic waves are instead
caused by these upflows. The different physical cause for coronal
oscillations would significantly impact the prospects of successful
coronal seismology using propagating disturbances in coronal loops.
Title: The Impact of New EUV Diagnostics on CME-Related Kinematics
Authors: McIntosh, Scott W.; De Pontieu, Bart; Leamon, Robert J.
Bibcode: 2010SoPh..265....5M
Altcode: 2010SoPh..tmp...74M; 2010arXiv1001.2022M
We present the application of novel diagnostics to the spectroscopic
observation of a Coronal Mass Ejection (CME) on disk by the Extreme
Ultraviolet Imaging Spectrometer (EIS) on the Hinode spacecraft. We
apply a recently developed line profile asymmetry analysis to the
spectroscopic observation of NOAA AR 10930 on 14 - 15 December 2006
to three raster observations before and during the eruption of a 1000
km s−1 halo CME. We see the impact that the observer's
line-of-sight and magnetic field geometry have on the diagnostics
used. Further, and more importantly, we identify the on-disk signature
of a high-speed outflow behind the CME in the dimming region arising
as a result of the eruption. Supported by recent coronal observations
of the STEREO spacecraft, we speculate about the momentum flux
resulting from this outflow as a secondary momentum source to the
CME. The results presented highlight the importance of spectroscopic
measurements in relation to CME kinematics, and the need for full-disk
synoptic spectroscopic observations of the coronal and chromospheric
plasmas to capture the signature of such explosive energy release as
a way of providing better constraints of CME propagation times to L1,
or any other point of interest in the heliosphere.
Title: Comparison of Coronal Density from CoMP and Mk4
Authors: Sitongia, Leonard; Burkepile, Joan; McIntosh, Scott;
Tomczyk, Steve
Bibcode: 2010shin.confE..90S
Altcode:
The High Altitude Observatory's Coronal Multi-channel Polarimeter
(CoMP) can measure coronal densities through the ratio of FeXIII
1074.7nm and 1079.8nm lines. A preliminary analysis of this is done
for one day of observations. This is compared to the density from the
Mk4 K-Coronameter.
Title: New coronal observations from the High Altitude Observatory
/ NCAR
Authors: Kolinski, Donald John; Burkepile, Joan; Tomczyk, Steve;
Nelson, Peter; Sitongia, Leonard; deToma, Giuliana; McIntosh, Scott;
Lecinski, Alice; Judge, Phil
Bibcode: 2010shin.confE.154K
Altcode:
The Mauna Loa Solar Observatory (MLSO) has been observing the sun and
providing the data to the community for almost 45 years. Currently,
we offer H-alpha images of the solar disk and limb, He-I images of the
disk, and white light images of the corona, all with a nominal 3 minute
cadence. However, new developments are afoot. MLSO will soon be
home to new instruments that will help increase our understanding of
the solar corona. The first, already deployed to MLSO, is a coronal
polarimeter that is able to measure the complete Stokes polarization
state and perform inversions of the coronal magnetic field. It is
awaiting final calibration and will be serving data soon through the
MLSO web site (http://mlso.hao.ucar.edu). The second, proposed to be
deployed before the end of 2012, is the Next Generation K-Coronagraph,
offering superior signal-to-noise, high time cadence, uniform spatial
resolution, and observations lower in the corona. Look for posters at
SHINE 2010 by Leonard Sitongia et al. and Joan Burkepile et al. that
more thoroughly describe these exciting new instruments. We
will also be bringing new data products to the community through our
recently updated website. HAO has been working to provide a uniform
archive of digitized images of eclipses going back to 1869, including
images processed with new techniques by M. Druckmüller (see the new
archive at http://mlso.hao.ucar.edu/mlso_eclipse_archive.html). We
are also developing a page to archive animations of solar activity
such as EPs and CMEs.
Title: STEREO quadrature observations of coronal dimming at the
onset of mini-CMEs
Authors: Innes, D. E.; McIntosh, S. W.; Pietarila, A.
Bibcode: 2010A&A...517L...7I
Altcode: 2010arXiv1005.2097I
Context. Using unique quadrature observations with the two STEREO
spacecraft, we investigate coronal dimmings at the onset of small-scale
eruptions. In CMEs they are believed to indicate the opening up of
the coronal magnetic fields at the start of the eruption.
Aims: It is to determine whether coronal dimming seen in small-scale
eruptions starts before or after chromospheric plasma ejection.
Methods: One STEREO spacecraft obtained high cadence, 75 s, images in
the He II 304 Å channel, and the other simultaneous images in the
Fe IX/Fe X 171 Å channel. We concentrate on two well-positioned
chromospheric eruptions that occurred at disk center in the 171
Å images, and on the limb in 304 Å. One was in the quiet Sun and
the other was in an equatorial coronal hole. We compare the timing
of chromospheric eruption seen in the 304 Å limb images with the
brightenings and dimmings seen on disk in the 171 Å images. Further
we use off-limb images of the low frequency 171 Å power to infer
the coronal structure near the eruptions.
Results: In both
the quiet Sun and the coronal hole eruption, on disk 171 Å dimming
was seen before the chromospheric eruption, and in both cases it
extends beyond the site of the chromospheric eruption. The quiet
Sun eruption occurred on the outer edge of the enclosing magnetic
field of a prominence and may be related to a small disruption of
the prominence just before the 171 Å dimming.
Conclusions:
These small-scale chromospheric eruptions started with a dimming in
coronal emission just like their larger counterparts. We therefore
suggest that a fundamental step in triggering them was the removal of
overlying coronal field. Movies are only available in electronic
form at http://www.aanda.org
Title: NCAR COSMO K-Coronagraph and Chromospheric Magnetometer
Authors: Burkepile, Joan T.; Tomczyk, Steve; Nelson, Pete; de Wijn,
Alfred; Sewell, Scott; Casini, Roberto; Elmore, David; McIntosh,
Scott; Kolinski, Don; Summers, Rich
Bibcode: 2010shin.confE...3B
Altcode:
We discuss the status of the COronal Solar Magnetism Observatory
(COSMO), a proposed facility dedicated to studying coronal and
chromospheric magnetic fields and their role in driving solar
activity such as coronal mass ejections (CMEs). COSMO is comprised of
3 instruments: 1) a 1.5 m coronagraph dedicated to the study of coronal
magnetic fields; 2) a chromospheric and prominence magnetometer; and 3)
a K-coronagraph designed to study the formation of CMEs and the density
structure of the low corona. The National Center for Atmospheric
Research (NCAR) is fully funding the COSMO K-coronagraph which will
be deployed at the end of 2012. It will observe the white light solar
corona from 1.05 to 3 solar radii at 15 second time cadence in order to
the formation of coronal mass ejections (CMEs) and their interactions
with surrounding coronal structures and related activity (e.g. flares,
prominence eruptions and shock waves). The COSMO K-coronagraph will
replace the aging Mauna Loa Solar Observatory (MLSO) K-coronameter which
has been in operation since 1980. The High Altitude Observatory
(HAO) is funding the design and fabrication of the prototype for the
chromospheric magnetometer. This prototype will include the narrow-band
fully tunable Lyot filter capable of observing from the optical
into the near infrared that is required by the COSMO Chromospheric
Magnetometer. The prototype for the COSMO 1.5 m coronagraph is
the Coronal Multi-Channel Polarimeter (CoMP), designed and funded by
HAO and NCAR. Scientific results from this fully operational prototype
have been reported (e.g. Tomczyk et al. 2007). CoMP has recently been
deployed to MLSO for full time operations (see poster by Sitongia et
al.) The COSMO facility will be designed, built and operated by
the High Altitude Observatory of the National Center for Atmospheric
Research in collaboration with the University of Hawaii and the
University of Michigan. It will replace the current Mauna Loa Solar
Observatory which has been collecting observations of the corona,
chromosphere and photosphere since 1945. NCAR science is supported by
the National Science Foundation (NSF).
Title: New Observations Of The Solar Coronal Magnetism And Waves
With HAO/CoMP
Authors: McIntosh, Scott W.; Tomczyk, S.
Bibcode: 2010AAS...21630201M
Altcode:
We will present details of the observations made by the HAO Coronal
Multi-channel Polarimeter (CoMP) following its recent deployment at the
Mauna Loa Solar Observatory. As well as presenting the synoptic data
products, measurements, and data access we will discuss monitoring of
solar coronal magnetism, its evolution and MHD wave properties with
this unique instrumentation.
Title: Supergranule variability in Mt. Wilson Ca II K images
Authors: Hock, Rachel; Eparvier, F. G.; McIntosh, S. W.; Rast, M. P.
Bibcode: 2010AAS...21640107H
Altcode: 2010BAAS...41Q.858H
We examined the Mt. Wilson Ca II K archive to quantify the long-term
changes in the average size of supergranules over five solar cycles
from 1930 to 1985. We determined that, although the Mt. Wilson Ca II K
images are limited by atmospheric seeing, there is sufficient contrast
in the images to identify supergranules. In general, we found that
supergranule size increases during the rising phase of a solar cycle,
reaching a peak at solar maximum. In the declining phase of a solar
cycle, supergranule size has a larger second peak, becoming out of
phase with the solar cycle for several years.
Title: Quasi-periodic Signatures in the Transition Region and Corona:
Waves or Flows?
Authors: McIntosh, Scott W.; De Pontieu, B.
Bibcode: 2010AAS...21630502M
Altcode:
Since the discovery of quasi-periodic oscillations with periods of order
3-10 minutes in coronal loops with TRACE and EIT (and later with EUVI
and EIS), these oscillations have mostly been interpreted as evidence
for propagating slow-mode magnetoacoustic waves in a low plasma beta
environment originating, most-likely, in the chromosphere. We show that
this interpretation is not unique, and that at least for plage-related
coronal loops, it may not be the most likely cause for the observed
quasi-periodicities. We use Monte Carlo simulations to show that current
oscillation detection methods based on wavelet analysis, and wave
tracking cannot distinguish the quasi-periodic signals of such waves
in coronal imaging timeseries with those caused by the faint signal
from upflows at 50-150 km/s that have lifetimes of order 1-2 minutes
and that occur randomly in time and occur on granular timescales. Such
upflows were recently discovered as blueward line asymmetries with
EIS and have been linked to chromospheric, spicular upflows that
are rapidly heated to coronal temperatures. We use EIS and SUMER
spectra to show that these faint upflows at the footpoints of coronal
loops sometimes occur quasi-periodically on timescales of order 5-15
minutes. Finally, we show that recent EIS measurements of intensity and
velocity oscillations, that have been interpreted as direct evidence for
propagating waves, are fully compatible with a scenario in which faint
upflows at high speed occur quasi-periodically. We show evidence from
spectral line asymmetry analysis that support this scenario. We suggest
that a significant fraction of the quasi-periodicities observed with
coronal imagers and spectrographs that have previously been interpreted
as propagating magnetoacoustic waves, may instead be caused by these
upflows. The uncertainty in the identification of the physical cause for
coronal oscillations significantly impacts the prospects of successful
coronal seismology using propagating, slow-mode magneto-acoustic waves.
Title: The Solar Brightpoint Database: A Proxy For Supergranular
and Small-Scale Dynamo Evolution?
Authors: McIntosh, Scott W.; Markel, R. J.; Sitongia, L.
Bibcode: 2010AAS...21640106M
Altcode: 2010BAAS...41Q.858M
Combining information derived from Yohkoh/SXT, SOHO/EIT, Hinode/XRT,
and the twin STEREO/SECCHI/EUVI broadband imagers of the solar corona we
investigate the behavior of one of the corona's ubiquitous small-scale
features, Bright Points. In an extension and improvement on previous
efforts we have information spanning from 1991 to the present day that
is providing interesting physical detail about the workings of the
small-scale corona over more than one solar cycle. We are unlocking
a myriad of information about the "coronal" differential rotation
inferred from bright points, their migration, lifetime and other
features over this time period. To the best of our knowledge these
features have never been consistently investigated. As a highlight we
will study the peculiar "m=1" asymmetry in bright point distributions
that occurred in the depths of the recent solar minimum and tie it to
other behavior when the quiet solar activity dominates the heliosphere.
Title: Prevalence And Temperature Dependence Of Ubiquitous High
Speed Upflows In Transition Region And Corona
Authors: De Pontieu, Bart; McIntosh, S.
Bibcode: 2010AAS...21640301D
Altcode: 2010BAAS...41R.877D
Recent observations and analysis have revealed the presence of
ubiquitous rapid upflows with velocities of order 50-150 km/s in the
lower solar atmosphere. We have found signatures of these events in
data from a broad range of imaging and spectroscopic instruments in the
chromosphere, in the form of spicules, and in the transition region
(TR) and corona, in the form of blueward asymmetries of TR/coronal
spectral line profiles, and propagating disturbances in coronal
imaging. Preliminary analysis suggests that these upflows are part
of a previously undetected, but relentless transfer of mass between
the dense lower atmosphere and tenuous corona in which a potentially
significant amount of plasma may be heated to coronal temperatures
at very low heights, in the upper chromosphere, TR and low corona. There are many unresolved issues regarding the properties, formation
mechanism and impact of these rapid upflow events. How ubiquitous are
they? Do they occur at the footpoint regions of loops across whole
active regions, or only at the edges? How do the upflow speeds vary
with temperature? We perform a large sample study of active regions
observed with Hinode/EIS and study the asymmetry of the TR and coronal
lines for a large number of viewing angles (from center to limb) and
magnetic field configurations. We also use double fits of gaussians to
determine the velocity of high velocity component, and its variation
as a function of temperature. These measurements can provide direct
constraints for coronal heating models.
Title: STEREO observations of quasi-periodically driven high velocity
outflows in polar plumes
Authors: McIntosh, S. W.; Innes, D. E.; de Pontieu, B.; Leamon, R. J.
Bibcode: 2010A&A...510L...2M
Altcode: 2010arXiv1001.3377M
Context. Plumes are one of the most ubiquitous features seen at the
limb in polar coronal holes and are considered to be a source of
high density plasma streams to the fast solar wind.
Aims: We
analyze STEREO observations of plumes and aim to reinterpret and place
observations with previous generations of EUV imagers within a new
context that was recently developed from Hinode observations.
Methods: We exploit the higher signal-to-noise, spatial and temporal
resolution of the EUVI telescopes over that of SOHO/EIT to study
the temporal variation of polar plumes in high detail. We employ
recently developed insight from imaging (and spectral) diagnostics of
active region, plage, and quiet Sun plasmas to identify the presence
of apparent motions as high-speed upflows in magnetic regions as
opposed to previous interpretations of propagating waves.
Results: In almost all polar plumes observed at the limb in these
STEREO sequences, in all coronal passbands, we observe high speed
jets of plasma traveling along the structures with a mean velocity of
135 km s-1 at a range of temperatures from 0.5-1.5 MK. The
jets have an apparent brightness enhancement of ~5% above that of the
plumes they travel on and repeat quasi-periodically, with repeat-times
ranging from five to twenty-five minutes. We also notice a very
weak, fine scale, rapidly evolving, but ubiquitous companion of the
plumes that covers the entire coronal hole limb.
Conclusions:
The observed jets are remarkably similar in intensity enhancement,
periodicity and velocity to those observed in other magnetic regions
of the solar atmosphere. They are multi-thermal in nature. We infer
that the jets observed on the plumes are a source of heated mass
to the fast solar wind. Further, based on the previous results that
motivated this study, we suggest that these jets originated in the
upper chromosphere. Five movies are only available in electronic
form at http://www.aanda.org
Title: STEREO quadrature observations of mass flows in prominences
Authors: Innes, Davina; McIntosh, Scott; Pietarila, Anna
Bibcode: 2010cosp...38.2917I
Altcode: 2010cosp.meet.2917I
Understanding the structure and dynamics of prominences is much
easier when both the promi-nence on the limb and the filament on
the disk are seen together. In February 2009, we obtained STEREO
quadrature observations with a cadence of 75 s and simultaneous images
of promi-nences in 304 A at the limb, and 171 A at disk center. We show
how the observed flows in the prominence are associated with microflares
seen in 171 at disk center for a couple of representative cases.
Title: Propagating disturbances in the corona: flows or waves?
Authors: de Pontieu, Bart; McIntosh, Scott
Bibcode: 2010cosp...38.2925D
Altcode: 2010cosp.meet.2925D
Since the discovery of quasi-periodic oscillations with periods of
order 3-10 minutes in coronal loops with TRACE and EIT (and later
with STEREO/EUVI and Hinode/EIS), these oscil-lations have mostly been
interpreted as evidence for propagating slow-mode magnetoacoustic waves
in a low plasma β environment. We show that this interpretation is
not unique, and that at least for plage-related coronal loops, it may
not be the most likely cause for the ob-served quasi-periodicities. We
use Monte Carlo simulations to show that current oscillation detection
methods based on wavelet analysis, wave tracking and Bayesian statistics
cannot distinguish the quasi-periodic signals of such waves in coronal
imaging timeseries with those caused by the faint signal from upflows
at 50-150 km/s that have lifetimes of order 1-2 min-utes and that occur
randomly in time and occur on granular timescales. Such upflows were
recently discovered as blueward line asymmetries with EIS and have been
linked to chromo-spheric, spicular upflows that are rapidly heated
to coronal temperatures. We use EIS and SUMER spectra to show that
these faint upflows at the footpoints of coronal loops sometimes occur
quasi-periodically on timescales of order 5-15 minutes. Finally, we show
that recent EIS measurements of intensity and velocity oscillations,
that have been interpreted as direct evi-dence for propagating waves,
are fully compatible with a scenario in which faint upflows at high
speed occur quasi-periodically. We show evidence from spectral line
asymmetry analysis that supports this scenario. We suggest that a
significant fraction of the quasi-periodicities observed with coronal
imagers and spectrographs that have previously been interpreted as
propagating magnetoacoustic waves, may instead be caused by these
upflows. The uncertainty in the identi-fication of the physical cause
for coronal oscillations impacts the prospects of successful coronal
seismology using propagating, slow-mode magneto-acoustic waves.
Title: STEREO quadrature observations of coronal dimming at the
onset of mini-CMEs
Authors: Innes, Davina; McIntosh, Scott
Bibcode: 2010cosp...38.1821I
Altcode: 2010cosp.meet.1821I
We study small solar eruptions using observations from the STEREO
spacecraft in quadrature. One spacecraft obtained images through the
171 A filter and the other simultaneously through the 304 A filter,
with a cadence 75 s. By co-aligning the disk center 171 A images
with the limb 304 A images, we investigate the temporal and spatial
relationship for the emissions at the different wavelengths from the
different perspectives. We concentrate on two small eruptions: one
in a coronal hole and one in the quiet Sun. In each case dimming in
the 171 A filter precedes and surrounds brightening at 171 A and the
chromospheric eruption. Similar coronal dimmings are often associated
with the onset of large CMEs just before and simultaneous with flares
and/or filament eruptions. The observations reinforce the idea of a
single, scale-free process for solar eruption.
Title: Toward the analysis of waves in the solar atmosphere based
on NLTE spectral synthesis from 3D MHD simulations.
Authors: Haberreiter, M.; Finsterle, W.; McIntosh, S.; Wedemeyer-Böhm,
S.
Bibcode: 2010MmSAI..81..782H
Altcode: 2010arXiv1001.5086H
From the analysis of Dopplergrams in the K I 7699 Å and Na I 5890
Å spectral lines observed with the Magneto-Optical filter at Two
Heights (MOTH) experiment during the austral summer in 2002-03 we find
upward traveling waves in magnetic regions. Our analysis shows that
the dispersion relation of these waves strongly depends on whether
the wave is detected in the low-beta or high-beta regime. Moreover,
the observed dispersion relation does not show the expected decrease
of the acoustic cut-off frequency for the field guided slow magnetic
wave. Instead, we detected an increase of the travel times below the
acoustic cut-off frequency and at the same time a decrease of the travel
time above it. To study the formation height of the spectral lines
employed by MOTH in greater detail we are currently in the process of
employing 3D MHD simulations carried out with CO5BOLD to
perform NLTE spectral synthesis.
Title: On the propagation of p-modes into the solar chromosphere
Authors: de Wijn, A. G.; McIntosh, S. W.; De Pontieu, B.
Bibcode: 2010MmSAI..81..588D
Altcode:
We employ tomographic observations of a small region of plage to study
the propagation of waves from the solar photosphere to the chromosphere
using a Fourier phase-difference analysis. Our results show the expected
vertical propagation for waves with periods of 3 minutes. Waves with
5-minute periods, i.e., above the acoustic cut-off period, are found to
propagate only at the periphery of the plage, and only in the direction
in which the field can be reasonably expected to expand. We conclude
that field inclination is critically important in the leakage of p-mode
oscillations from the photosphere into the chromosphere.
Title: More of the Inconvenient Truth About Coronal Dimmings
Authors: McIntosh, S. W.; Burkepile, J.; Leamon, R. J.
Bibcode: 2009ASPC..415..393M
Altcode: 2009arXiv0901.2817M
We continue the investigation of a CME-driven coronal dimming
from December 14 2006 using unique high resolution imaging of the
chromosphere and corona from the Hinode spacecraft. Over the course
of the dimming event we observe the dynamic increase of non-thermal
line broadening of multiple emission lines as the CME is released
and the corona opens; reaching levels seen in coronal holes. As
the corona begins to close, refill and brighten, we see a reduction
of the non-thermal broadening towards the pre-eruption level. The
dynamic evolution of non-thermal broadening is consistent with the
expected change of Alfvén wave amplitudes in the magnetically open
rarefied dimming region, compared to the dense closed corona prior to
the CME. The presented data reinforce the belief that coronal dimmings
must be temporary sources of the fast solar wind. It is unclear if such
a rapid transition in the thermodynamics of the corona to a solar wind
state has an effect on the CME itself.
Title: High-Speed Transition Region and Coronal Upflows in the
Quiet Sun
Authors: McIntosh, Scott W.; De Pontieu, Bart
Bibcode: 2009ApJ...707..524M
Altcode: 2009arXiv0910.5191M
We study the line profiles of a range of transition region (TR)
emission lines observed in typical quiet-Sun regions. In magnetic
network regions, the Si IV 1402 Å, C IV 1548 Å, N V 1238 Å, O VI
1031 Å, and Ne VIII 770 Å spectral lines show significant asymmetry
in the blue wing of the emission line profiles. We interpret these
high-velocity upflows in the lower and upper TR as the quiet-Sun
equivalent of the recently discovered upflows in the low corona above
plage regions. The latter have been shown to be directly associated
with high-velocity chromospheric spicules that are (partially) heated
to coronal temperatures and play a significant role in supplying the
active region corona with hot plasma. We show that a similar process
likely dominates the quiet-Sun network. We provide a new interpretation
of the observed quiet-Sun TR emission in terms of the relentless
mass transport between the chromosphere and corona—a mixture of
emission from dynamic episodic heating and mass injection into the
corona as well as that from the previously filled, slowly cooling,
coronal plasma. Analysis of the observed upflow component shows that
it carries enough hot plasma to play a significant role in the energy
and mass balance of the quiet corona. We determine the temperature
dependence of the upflow velocities to constrain the acceleration and
heating mechanism that drives these upflows. We also show that the
temporal characteristics of these upflows suggest an episodic driver
that sometimes leads to quasi-periodic signals. We suggest that at
least some of the quasi-periodicities observed with coronal imagers
and spectrographs that have previously been interpreted as propagating
magnetoacoustic waves, may instead be caused by these upflows.
Title: Interactions Between Reversed Granulation, p-Modes, and
Magnetism?
Authors: de Wijn, A. G.; McIntosh, S. W.; de Pontieu, B.
Bibcode: 2009ASPC..415...36D
Altcode: 2009arXiv0902.1966D
We investigate features that are observed in Ca II H sequences from
Hinode in places where reversed granulation seems to interact with
p-modes. These features appear ubiquitously in the quiet sun. They
are co-spatial with reversed granulation, and display similar
general properties, but have sharper edges and show fast brightness
changes. They also appear predominantly above wide intergranular
lanes, indicating a potential connection with magnetism. We report on
the appearance and dynamics of these features using high-resolution,
high-cadence observations from Hinode, and we discuss their possible
origin.
Title: What Goes Up Doesn't Necessarily Come Down! Connecting the
Dynamics of the Chromosphere and Transition Region with TRACE,
Hinode and SUMER
Authors: McIntosh, S. W.; de Pontieu, B.
Bibcode: 2009ASPC..415...24M
Altcode: 2009arXiv0901.2814M
We explore joint observations of the South-East limb made by
Hinode, TRACE and SOHO/SUMER on April 12, 2008 as part of the Whole
Heliosphere Interval (WHI) Quiet Sun Characterization targeted observing
program. During the sequence a large, 10Mm long, macro-spicule was sent
upward and crossed the line-of-sight of the SUMER slit, an event that
affords us an opportunity to study the coupling of cooler chromospheric
material to transition region emission formed as hot as 600,000K. This
short article provides preliminary results of the data analysis.
Title: On the Role of Acoustic-Gravity Waves in the Energetics of
the Solar Atmosphere
Authors: Straus, T.; Fleck, B.; Jefferies, S. M.; McIntosh, S. W.;
Severino, G.; Steffen, M.; Tarbell, T. D.
Bibcode: 2009ASPC..415...95S
Altcode: 2010arXiv1003.3773S
In a recent paper (Straus et al. 2008) we determined the energy
flux of internal gravity waves in the lower solar atmosphere using
a combination of 3D numerical simulations and observations obtained
with the IBIS instrument operated at the Dunn Solar Telescope and
the Michelson Doppler Imager (MDI) on SOHO. In this paper we extend
these studies using coordinated observations from SOT/NFI and SOT/SP
on Hinode and MDI. The new measurements confirm that gravity waves
are the dominant phenomenon in the quiet middle/upper photosphere and
that they transport more mechanical energy than the high-frequency
(> 5 mHz) acoustic waves, even though we find an acoustic flux 3-5
times larger than the upper limit estimate of Fossum & Carlsson
(2006). It therefore appears justified to reconsider the significance of
(non-M)HD waves for the energy balance of the solar chromosphere.
Title: Observing the Roots of Coronal Heating - in the Chromosphere
Authors: McIntosh, S. W.; de Pontieu, B.; Hansteen, V. H.; Schrjver, K.
Bibcode: 2009AGUFMSH44A..01M
Altcode:
I will discuss recent results using Hinode/SOT-EIS-XRT, SOHO/SUMER,
CRISP (at the Swedish Solar Telescope) and TRACE that provide a
direct connection between coronal dynamics and those of the lower
atmosphere. We use chromospheric measurements (H-alpha and Ca II
8542 spectral imaging, and Ca II H images), as well as UV spectra
(EIS and SUMER), and EUV/X-ray images (XRT and TRACE) to show that
faint, high-speed upflows at velocities of 50-100 km/s across a wide
range of temperatures from chromospheric (10,000 K), through lower
and upper transition region (0.1 to 0.7 MK) and coronal temperatures
(2 MK) are associated with significant mass-loading of the corona with
hot plasma. Our observations are incompatible with current models in
which coronal heating occurs as a result of nanoflares at coronal
heights. Instead we suggest that a significant fraction of heating
of plasma to coronal temperatures may occur at chromospheric heights
in association with jets driven from below (the recently discovered
type II spicules). Illustrating the mass and energy transport between
the chromosphere, transition region and corona, as deduced from Hinode
observations. Convective flows and oscillations in the convection zone
and photosphere of the Sun buffet the magnetic field of the Sun. This
leads to at least two different kinds of jets in the chromosphere:
Type I, and II spicules. Type II spicules drive matter upward violently
and likely form when magnetic field reconnects because of stresses
introduced by convective flows. A significant fraction of the plasma
in type II spicules is heated to coronal temperatures (>1MK),
providing the corona with hot plasma. The correlation between the
chromospheric and coronal parts of the spicules depends greatly on the
viewing angle between the line-of-sight and the direction of the upward
flows. Order of magnitude estimates indicate that the mass supplied
by type II spicules plays a significant role in supplying the corona
with hot plasma.
Title: Observing Episodic Coronal Heating Events Rooted in
Chromospheric Activity
Authors: McIntosh, Scott W.; De Pontieu, Bart
Bibcode: 2009ApJ...706L..80M
Altcode: 2009arXiv0910.2452M
We present the results of a multi-wavelength study of episodic plasma
injection into the corona of active region (AR) 10942. We exploit
long-exposure images of the Hinode and Transition Region and Coronal
Explorer spacecraft to study the properties of faint, episodic,
"blobs" of plasma that are propelled upward along coronal loops
that are rooted in the AR plage. We find that the source location
and characteristic velocities of these episodic upflow events match
those expected from recent spectroscopic observations of faint coronal
upflows that are associated with upper chromospheric activity, in the
form of highly dynamic spicules. The analysis presented ties together
observations from coronal and chromospheric spectrographs and imagers,
providing more evidence of the connection of discrete coronal mass
heating and injection events with their source, dynamic spicules,
in the chromosphere.
Title: On the Propagation of p-Modes Into the Solar Chromosphere
Authors: de Wijn, A. G.; McIntosh, S. W.; De Pontieu, B.
Bibcode: 2009ApJ...702L.168D
Altcode: 2009arXiv0908.1383D
We employ tomographic observations of a small region of plage to study
the propagation of waves from the solar photosphere to the chromosphere
using a Fourier phase-difference analysis. Our results show the expected
vertical propagation for waves with periods of 3 minutes. Waves with
5 minute periods, i.e., above the acoustic cutoff period, are found to
propagate only at the periphery of the plage, and only in the direction
in which the field can be reasonably expected to expand. We conclude
that field inclination is critically important in the leakage of p-mode
oscillations from the photosphere into the chromosphere.
Title: Estimating the Chromospheric Absorption of Transition Region
Moss Emission
Authors: De Pontieu, Bart; Hansteen, Viggo H.; McIntosh, Scott W.;
Patsourakos, Spiros
Bibcode: 2009ApJ...702.1016D
Altcode: 2009arXiv0907.1883D
Many models for coronal loops have difficulty explaining the observed
EUV brightness of the transition region, which is often significantly
less than theoretical models predict. This discrepancy has been
addressed by a variety of approaches including filling factors and
time-dependent heating, with varying degrees of success. Here, we
focus on an effect that has been ignored so far: the absorption of
EUV light with wavelengths below 912 Å by the resonance continua
of neutral hydrogen and helium. Such absorption is expected to occur
in the low-lying transition region of hot, active region loops that
is colocated with cool chromospheric features and called "moss" as a
result of the reticulated appearance resulting from the absorption. We
use cotemporal and cospatial spectroheliograms obtained with the Solar
and Heliospheric Observatory/SUMER and Hinode/EIS of Fe XII 1242 Å,
195 Å, and 186.88 Å, and compare the density determination from
the 186/195 Å line ratio to that resulting from the 195/1242 Å line
ratio. We find that while coronal loops have compatible density values
from these two line pairs, upper transition region moss has conflicting
density determinations. This discrepancy can be resolved by taking
into account significant absorption of 195 Å emission caused by
the chromospheric inclusions in the moss. We find that the amount of
absorption is generally of the order of a factor of 2. We compare to
numerical models and show that the observed effect is well reproduced
by three-dimensional radiative MHD models of the transition region
and corona. We use STEREO A/B data of the same active region and find
that increased angles between line of sight and local vertical cause
additional absorption. Our determination of the amount of chromospheric
absorption of TR emission can be used to better constrain coronal
heating models.
Title: Observing the Roots of Solar Coronal Heating—in the
Chromosphere
Authors: De Pontieu, Bart; McIntosh, Scott W.; Hansteen, Viggo H.;
Schrijver, Carolus J.
Bibcode: 2009ApJ...701L...1D
Altcode: 2009arXiv0906.5434D
The Sun's corona is millions of degrees hotter than its 5000 K
photosphere. This heating enigma is typically addressed by invoking
the deposition at coronal heights of nonthermal energy generated
by the interplay between convection and magnetic field near the
photosphere. However, it remains unclear how and where coronal heating
occurs and how the corona is filled with hot plasma. We show that energy
deposition at coronal heights cannot be the only source of coronal
heating by revealing a significant coronal mass supply mechanism that
is driven from below, in the chromosphere. We quantify the asymmetry
of spectral lines observed with Hinode and SOHO and identify faint
but ubiquitous upflows with velocities that are similar (50-100 km
s-1) across a wide range of magnetic field configurations and
for temperatures from 100,000 to several million degrees. These upflows
are spatiotemporally correlated with and have similar upward velocities
as recently discovered, cool (10,000 K) chromospheric jets or (type II)
spicules. We find these upflows to be pervasive and universal. Order
of magnitude estimates constrained by conservation of mass and observed
emission measures indicate that the mass supplied by these spicules can
play a significant role in supplying the corona with hot plasma. The
properties of these events are incompatible with coronal loop models
that include only nanoflares at coronal heights. Our results suggest
that a significant part of the heating and energizing of the corona
occurs at chromospheric heights, in association with chromospheric jets.
Title: Time-Distance Seismology of the Solar Corona with CoMP
Authors: Tomczyk, Steven; McIntosh, Scott W.
Bibcode: 2009ApJ...697.1384T
Altcode: 2009arXiv0903.2002T
We employ a sequence of Doppler images obtained with the Coronal
Multi-channel Polarimeter (CoMP) instrument to perform time-distance
seismology of the solar corona. We construct the first k-ω diagrams of
the region. These allow us to separate outward and inward propagating
waves and estimate the spatial variation of the plane-of-sky-projected
phase speed, and the relative amount of outward and inward directed
wave power. The disparity between outward and inward wave power and the
slope of the observed power-law spectrum indicate that low-frequency
Alfvénic motions suffer significant attenuation as they propagate,
consistent with isotropic MHD turbulence.
Title: Reconciling Chromospheric and Coronal Observations of
Alfvenic Waves
Authors: McIntosh, Scott W.; De Pontieu, B.; Tomczyk, S.
Bibcode: 2009SPD....40.1303M
Altcode:
We review the properties of the Alfvenic waves that were discovered
with Hinode/SOT and that have been shown to permeate the upper
chromosphere. Statistical analysis shows that, if they penetrate into
the corona, these waves carry enough energy to impact the energy balance
of the solar wind and quiet Sun corona. However, CoMP observations
of Alfven waves show much smaller resolved amplitudes than would be
expected from the leakage of chromospheric waves into the corona. We
use Monte Carlo simulations to show that line-of-sight superposition
of a mix of Alfvenic waves with properties similar to those observed
with Hinode/SOT and CoMP can reproduce the low wave amplitudes and
enhanced non-thermal line broadening observed with CoMP. Our analysis
indicates that the CoMP observations are compatible with a scenario
in which low-frequency Alfvenic waves are responsible for a large
fraction of the non-thermal broadening seen in the corona although
some portion remains from the power spectrum of the wave generation
process. This suggests that the flux carried by Alfvenic waves, in the
finely structured corona, is significant enough to impact the energy
balance of the corona and solar wind.
Title: Observing the Roots of Solar Coronal Heating in the
Chromosphere
Authors: McIntosh, Scott W.; De Pontieu, B.; Hansteen, V.; Schrijver,
C. J.
Bibcode: 2009SPD....40.2602M
Altcode:
The Sun's atmosphere or corona is millions of degrees hotter than
its 5,000 K surface or photosphere. This heating enigma is typically
addressed by invoking the deposition at coronal heights of non-thermal
energy generated by the interplay between convection and magnetic field
near the photosphere. However, it remains unclear how and where coronal
heating occurs and how the corona is filled with hot plasma. Here,
we show that energy deposition at coronal heights cannot be the only
source of coronal heating, by revealing a significant coronal mass
supply mechanism that is driven from below, in the chromosphere, the
interface between photosphere and corona. We quantify the asymmetry
of spectral lines observed with Hinode and SOHO and identify faint
but ubiquitous upflows with velocities that are similar (50-100
km/s) across a wide range of magnetic field configurations and for
temperatures from 100,000 to several million degrees. These upflows
are correlated with and have similar upward velocities as the very fine
and dynamic chromospheric jets, or spicules, discovered by Hinode. As
these phenomena are incompatible with models of coronal loops that
only include nanoflare heating at coronal heights, we conclude that
a significant fraction of the energy needed to heat coronal plasma is
deposited at chromospheric heights in association with spicular jets
driven from below.
Title: How the Solar Wind Ties to its Photospheric Origins
Authors: Leamon, Robert J.; McIntosh, Scott W.
Bibcode: 2009ApJ...697L..28L
Altcode: 2009arXiv0904.0614L
We present a new method of visualizing the solar photospheric
magnetic field based on the "Magnetic Range of Influence" (MRoI). The
MRoI is a simple realization of the magnetic environment in the
photosphere, reflecting the distance required to balance the integrated
magnetic field contained in any magnetogram pixel. It provides a new
perspective on where subterrestrial field lines in a Potential Field
Source Surface (PFSS) model connect to the photosphere, and thus
the source of Earth-directed solar wind (within the limitations of
PFSS models), something that is not usually obvious from a regular
synoptic magnetogram. In each of three sample solar rotations,
at different phases of the solar cycle, the PFSS footpoint either
jumps between isolated areas of high MRoI or moves slowly within one
such area. Footpoint motions are consistent with Fisk's interchange
reconnection model.
Title: Mining a Massive Brightpoint Database for Science
Authors: McIntosh, Scott W.; Sitongia, L.; Markel, R.; Judge, P. G.;
Davey, A. R.
Bibcode: 2009SPD....40.1525M
Altcode:
We update the analysis of McIntosh & Gurman [2005, Sol. Phys.,
228, 285] to incorporate changes to the automatic EUV Bright Point
(BP) detection algorithm of data from the Extreme-ultraviolet
Imaging Telescope (EIT) on the Solar and Heliospheric Observatory
(SOHO). We discuss the implementation of the BP catalog as a searchable
database for the community and some of the basic manipulations on
that database. We present the multi-wavelength differential rotation
rates for the previous solar cycle and make an initial foray into the
connection of this most ubiquitous coronal structure and the larger
scale magnetic dynamo.
Title: How the Solar Wind Ties to Its Photospheric Origins
Authors: Leamon, Robert; McIntosh, S. W.
Bibcode: 2009SPD....40.3101L
Altcode:
We present a new method of visualizing the solar photospheric magnetic
field based on the "Magnetic Range of Influence" (MRoI). The MRoI is
a simple realization of the magnetic environment in the photosphere,
reflecting the distance required to balance the integrated magnetic
field contained in any magnetogram pixel. It provides a new perspective
on where sub-terrestrial field lines in a Potential Field Source
Surface (PFSS) model connect to the photosphere, and thus the
source of Earth-directed solar wind (within the limitations of
PFSS models), something that is not usually obvious from a regular
synoptic magnetogram. In each of three sample solar rotations,
at different phases of the solar cycle, the PFSS footpoint either
jumps between isolated areas of high MRoI or moves slowly within one
such area. Footpoint motions are consistent with Fisk's interchange
reconnection model. We explore the relationships between the MRoI and
flux at the footpoint and the in situ composition of the resulting wind.
Title: Direct Imaging of Fine Structure in the Chromosphere of a
Sunspot Umbra
Authors: Socas-Navarro, H.; McIntosh, S. W.; Centeno, R.; de Wijn,
A. G.; Lites, B. W.
Bibcode: 2009ApJ...696.1683S
Altcode: 2008arXiv0810.0597S
High-resolution imaging observations from the Hinode spacecraft in the
Ca II H line are employed to study the dynamics of the chromosphere
above a sunspot. We find that umbral flashes and other brightenings
produced by the oscillation are extremely rich in fine structure,
even beyond the resolving limit of our observations (0farcs22). The
umbra is tremendously dynamic to the point that our time cadence of
20 s does not suffice to resolve the fast lateral (probably apparent)
motion of the emission source. Some bright elements in our data set
move with horizontal propagation speeds of 30 km s-1. We have
detected filamentary structures inside the umbra (some of which have a
horizontal extension of ~1500 km) which, to our best knowledge, had not
been reported before. The power spectra of the intensity fluctuations
reveal a few distinct areas with different properties within the umbra
that seem to correspond with the umbral cores that form it. Inside
each one of these areas the dominant frequencies of the oscillation
are coherent, but they vary considerably from one core to another.
Title: The Inconvenient Truth About Coronal Dimmings
Authors: McIntosh, Scott W.
Bibcode: 2009ApJ...693.1306M
Altcode: 2008arXiv0809.4024M
We investigate the occurrence of a coronal mass ejection (CME)-driven
coronal dimming using unique high-resolution spectral images of the
corona from the Hinode spacecraft. Over the course of the dimming
event, we observe the dynamic increase of nonthermal line broadening
in the 195.12 Å emission line of Fe XII as the corona opens. As the
corona begins to close, refill and brighten, we see a reduction of
the nonthermal broadening toward the pre-eruption level. We propose
that the dynamic evolution of the nonthermal broadening is the result
of the growth of Alfvén wave amplitudes in the magnetically open
rarefied dimming region, compared to the dense closed corona prior
to the CME. We suggest, based on this proposition, that, as open
magnetic regions, coronal dimmings must act just as coronal holes
and be sources of the fast solar wind, but only temporarily. Further,
we propose that such a rapid transition in the thermodynamics of the
corona to a solar wind state may have an impulsive effect on the CME
that initiates the observed dimming. This last point, if correct,
poses a significant physical challenge to the sophistication of CME
modeling and capturing the essence of the source region thermodynamics
necessary to correctly ascertain CME propagation speeds, etc.
Title: The Solar Chromosphere: Old Challenges, New Frontiers
Authors: Ayres, T.; Uitenbroek, H.; Cauzzi, G.; Reardon, K.; Berger,
T.; Schrijver, C.; de Pontieu, B.; Judge, P.; McIntosh, S.; White,
S.; Solanki, S.
Bibcode: 2009astro2010S...9A
Altcode:
No abstract at ADS
Title: Time Distance Coronal Seismology With the CoMP Instrument
Authors: Tomczyk, S.; McIntosh, S.
Bibcode: 2008AGUFMSH11A..01T
Altcode:
Recent velocity imaging observations obtained with the Coronal
Multi-channel Polarimeter (CoMP) instrument reveal the existence of
ubiquitous propagating Alfvén waves in the solar corona. These data
present an exciting opportunity for probing the structure and magnetic
topology of the coronal plasma through coronal seismology. We present
the results of a time-distance analysis of the wave observations
which allows the determination of the phase speed of the waves and the
relative quantity of outward and inward wave flux. This analysis also
provides a k-omega diagnostic diagram of coronal waves. We discuss
current and future prospects for coronal seismology with these data.
Title: The Spectroscopic Footprint of the Fast Solar Wind
Authors: McIntosh, S. W.; Leamon, R. J.; de Pontieu, B.
Bibcode: 2008AGUFMSH41A1612M
Altcode:
We explore a large, complex equatorial coronal hole (ECH) and its
immediate surroundings through the temperature dependence of the
non-thermal line widths of three transition region emission lines
observed by SOHO/SUMER, placing them in context with recent studies of
the other spectroscopic measures taken. Using a recent semi-empirical
model of the solar wind as a basis, we explore the structure of the
solar wind during the observing period and seek to gain a better
understanding of the interaction of this region with the nascent
solar wind.
Title: The Center-to-Limb Variation of TRACE Travel-Times
Authors: Leamon, R. J.; McIntosh, S. W.
Bibcode: 2008AGUFMSH41A1610L
Altcode:
We explore the limb-to-limb behavior of multi-frequency Transition
Region and Coronal Explorer (TRACE) travel-time measurements of
magneto-atmospheric waves in the solar chromosphere. We establish that
while the higher frequency acoustic travel-times (~ 7~mHz) show little
or no limb-to-limb variation, the previously documented variations of
travel-time measurements on the magnetic environment through which the
waves propagate are evident: increased travel-times in coronal holes;
decreased travel-times in strong closed magnetic concentrations. For
frequencies approaching the classical acoustic cut-off frequency
(5.2~mHz) and below there is an increasing dependence of the measured
travel-time with viewing angle and decreasing frequency. In this
paper we demonstrate, using supporting observations from the Solar
Optical Telescope on Hinode, that the center-to-limb variation of
the low-frequency travel-times is the signature of propagating waves
on magnetic network structures at granular spatial scales [i.e.,
structures close the spatial Nyquist frequency of TRACE] whose signal
is a result of sub-resolution UV emission line 'contamination' in the
1600Å passband. Further, these structures must have a line-of-sight
extension normal to the solar surface that increases across the disk
as we approach the limb. We deduce that the low- frequency travel-time
signal is directly caused by spicule motions which are increasingly
inclined to the TRACE line-of-sight. Similarly, using SOT support,
we propose that the apparent TRACE travel-time enhancement in coronal
holes from TRACE, at same granular network locations, is the result
of a change in vertical stratification in the coronal hole compared
to quiet Sun counterpart emission. This effort is of particular
relevance to full-disk travel-time investigations from the Solar
Dynamics Observatory.
Title: The Whole Heliosphere Interval: Campaign Summaries and
Early Results
Authors: Thompson, B.; Gibson, S. E.; McIntosh, S.; Fuller-Rowell,
T.; Galvin, A. B.; Kozyra, J. U.; Petrie, G.; Schroeder, P.; Strachan,
L.; Webb, D. F.; Woods, T.
Bibcode: 2008AGUFMSH21C..01T
Altcode:
The Whole Heliosphere Interval (WHI) is an internationally coordinated
observing and modeling effort to characterize the 3-dimensional
interconnected solar-heliospheric-planetary system - a.k.a. the
"heliophysical" system. The heart of the WHI campaign is the study
of the interconnected 3-D heliophysical domain, from the interior
of the Sun, to the Earth, outer planets, and into interstellar
space. WHI observing campaigns began with the 3-D solar structure from
solar Carrington Rotation 2068, which ran from March 20 - April 16,
2008. Observations and models of the outer heliosphere and planetary
impacts extend beyond those dates as necessary; for example, the
solar wind transit time to outer planets can take months. WHI occurred
during solar minimum, which optimizes our ability to characterize the
3-D heliosphere and trace the structure to the outer limits of the
heliosphere. Highlights include the 3-D reconstruction of the solar
wind and complex geospace response during this solar minimum, contrasts
with the past solar minimum, and the effect of transient activity on the
"quiet" heliosphere. Nearly 200 scientists are participated in WHI data
and modeling efforts, ensuring that the WHI integrated observations
and models will give us a "new view" of the heliophysical system. A
summary of some of the key results from the WHI first workshop in
August 2008 will be given.
Title: Dynamics of the upper chromosphere
Authors: de Pontieu, B.; Carlsson, M.; McIntosh, S.; Hansteen, V.;
Tarbell, T.
Bibcode: 2008AGUFMSH51C..05D
Altcode:
In the past few years, high-resolution observations with ground-based
telescopes and the Broadband Filter Imager (BFI) and Narrowband
Filter Imager (NFI) of the Solar Optical Telescope onboard Hinode
have revolutionized our view of the dynamics and energetics of
the chromosphere. We review some of these results, including the
discovery of two different types of spicules and the finding that the
chromosphere is riddled with strong Alfvenic waves. We describe how
these observations, when combined with advanced numerical simulations,
can help address important unresolved issues regarding the connection
between the photosphere and corona, such as the role of waves and
of reconnection in driving the dynamics and energetics of the upper
chromosphere, and how chromospheric dynamics impact the transition
region and corona.
Title: A Coherence-Based Approach for Tracking Waves in the Solar
Corona
Authors: McIntosh, Scott W.; De Pontieu, Bart; Tomczyk, Steven
Bibcode: 2008SoPh..252..321M
Altcode: 2008arXiv0808.2978M; 2008SoPh..tmp..162M
We consider the problem of automatically (and robustly) isolating
and extracting information about waves and oscillations observed
in EUV image sequences of the solar corona with a view to near
real-time application to data from the Atmospheric Imaging Array
(AIA) on the Solar Dynamics Observatory (SDO). We find that a simple
coherence/travel-time based approach detects and provides a wealth
of information on transverse and longitudinal wave phenomena in the
test sequences provided by the Transition Region and Coronal Explorer
(TRACE). The results of the search are pruned (based on diagnostic
errors) to minimize false-detections such that the remainder provides
robust measurements of waves in the solar corona, with the calculated
propagation speed allowing automated distinction between various
wave modes. In this paper we discuss the technique, present results
on the TRACE test sequences, and describe how our method can be
used to automatically process the enormous flow of data (≈1 Tb
day−1) that will be provided by SDO/AIA.
Title: High Frequency Acoustic Waves in the Sun's Atmosphere
Authors: Fleck, B.; Jefferies, S. M.; McIntosh, S. W.; Severino, G.;
Straus, T.; Tarbell, T. D.
Bibcode: 2008ESPM...12.2.39F
Altcode:
This year marks the 60th anniversary of two pioneering papers by
Schwarzschild (1948) and Biermann (1948), who independently proposed
that acoustic waves generated in the turbulent convection zone play
an important role in the heating of the chromosphere and corona. High
frequency acoustic waves have remained one of the leading contenders
for solving the heating problem of the non-magnetic chromospheres of
the Sun and late-type stars ever since. Earlier attempts to determine
the acoustic energy flux from ground were compromised by atmospheric
seeing, which has its biggest effect on the high frequency parts
of the observed signal. Recently, based on a comparison of TRACE
observations and 1-D simulations, Fossum & Carlsson (2005, 2006)
concluded that high-frequency acoustic waves are not sufficient
to heat the solar chromosphere. The same conclusion was reached by
Carlsson et al. (2007) from an analysis of Hinode SOT/BFI Ca II H and
blue continuum observations. Other authors (e.g. Cuntz et al. 2007;
Wedemeyer-Boehm et al. 2007, Kalkofen 2007), however, questioned
these results for a number of reasons. Because of its limited spatial
resolution and limited sensitivity there are inherent difficulties
when comparing TRACE observations with numerical simulations. Further,
intensity oscillations are difficult to interpret, as they result from
a phase-sensitive mix of temperature and pressure fluctuations, and
non-local radiation transfer effects may complicate the picture even
more. Here we revisit the role of high frequency acoustic waves in the
dynamics and energetics of the Sun's atmosphere using high cadence,
high resolution Doppler velocity measurements obtained with SOT/SP
and SOT/NFI on Hinode.
Title: On the Role of Acoustic-gravity Waves in the Energetics of
the Solar Atmosphere
Authors: Straus, T.; Fleck, B.; Jefferies, S. M.; Cauzzi, G.; McIntosh,
S. W.; Reardon, K.; Severino, G.; Steffen, M.; Suter, M.; Tarbell,
T. D.
Bibcode: 2008ESPM...12.2.11S
Altcode:
We revisit the dynamics and energetics of the solar atmosphere, using a
combination of high-quality observations and 3D numerical simulations
of the overshoot region of compressible convection into the stable
photosphere. We discuss the contribution of acoustic-gravity waves
to the energy balance of the photosphere and low chromosphere. We
demonstrate the presence of propagating internal gravity waves at
low frequencies (< 5mHz). Surprisingly, these waves are found
to be the dominant phenomenon in the quiet middle/upper photosphere
and to transport a significant amount of mechanical energy into the
atmosphere outweighing the contribution of high-frequency (> 5mHz)
acoustic waves by more than an order of magnitude. We compare the
properties of high-frequency waves in the simulations with results
of recent high cadence, high resolution Doppler velocity measurements
obtained with SOT/SP and SOT/NFI on Hinode. Our results seem to be in
conflict with the simple picture of upward propagating sound waves. We
discuss the implications of our findings on the energy flux estimate
at high-frequencies.
Title: What do Spicules Tell us About the Chromosphere?
Authors: de Pontieu, B.; Carlsson, M.; McIntosh, S.; Hansteen, V.;
Tarbell, T.
Bibcode: 2008ESPM...12.2.15D
Altcode:
In the past few years, high-resolution observations with ground-based
telescopes and the Broadband Filter Imager (BFI) and Narrowband
Filter Imager (NFI) of the Solar Optical Telescope onboard
Hinode have revolutionized our view of spicules and their role in
the chromosphere. We review some of these results, including the
discovery of two different types of spicules with different dynamics
and formation mechanisms, as well as the finding that the chromosphere
is riddled with strong Alfvenic waves. In an effort to determine
the formation mechanism of spicules and their impact on the outer
atmosphere, we further focus on the thermal evolution and velocities
developed by spicules. We use Dopplergrams made in the Na D 589.6 nm,
H-alpha 656.3 nm and Mg B 517.3 nm passbands, as well as filtergrams in
the Ca H 396.8 nm passband to study the spatio-temporal relationship
between the various spicular features. We compare those findings with
synthesized images based on line profiles computed from high-resolution
3D MHD numerical simulations from the University of Oslo. We also use
the Dopplergram data to investigate the velocities that develop in
the two types of spicules that were reported previously. We perform
statistical analysis of apparent velocities in the plane of the sky
and line-of-sight velocities derived from Dopplergrams to disentangle
the superposition of Alfvenic wave amplitudes and field-aligned
flows. We study these properties for a variety of magnetic field
configurations (coronal holes, quiet Sun, active region). Finally,
we focus on the formation mechanism of spicules by analyzing spicular
features in Dopplergrams on the disk that were taken simultaneously
with SP magnetograms.
Title: Impact of Active Regions on Coronal Hole Outflows
Authors: Habbal, Shadia Rifai; Scholl, Isabelle F.; McIntosh, Scott W.
Bibcode: 2008ApJ...683L..75H
Altcode:
Establishing the sources of the fast and slow solar wind is important
for understanding their drivers and their subsequent interaction
in interplanetary space. Although coronal holes continue to be
viewed as the main source of the fast solar wind, there is recent
evidence that the quiet Sun provides other spatially concentrated
sources. To identify the underlying physical characteristics of the
outflow from coronal holes, solar disk observations from the Solar
and Heliospheric Observatory (SOHO) are considered. These observations
encompass photospheric line-of-sight magnetic field measurements from
the Michelson Doppler Imager (MDI), Fe X 171 Å passband imaging from
the Extreme-ultraviolet Imaging Telescope (EIT), and Ne VIII 770 Å
spectral observations with outflows inferred from their corresponding
Doppler blueshifts, at solar minimum and maximum and at different
latitudes, from the Solar Ultraviolet Measurement of Emitted Radiation
(SUMER) instrument. The sharp variations of outflows within the SUMER
field of view, referred to as velocity gradients, are introduced
as a new diagnostic. It is shown that, in general, coronal holes
are indistinguishable from the quiet Sun, whether in their outflows
or their gradients. Surprisingly, however, when enhanced unbalanced
magnetic flux from active regions extends into neighboring coronal
holes, both outflows and their gradients become significantly enhanced
within the coronal holes and along their boundaries. The same effect is
observed in the quiet Sun, albeit to a lesser extent. These findings
point to the possibility that active regions can lead to enhanced
plasma outflows in neighboring coronal holes.
Title: The Energy Flux of Internal Gravity Waves in the Lower Solar
Atmosphere
Authors: Straus, Thomas; Fleck, Bernhard; Jefferies, Stuart M.;
Cauzzi, Gianna; McIntosh, Scott W.; Reardon, Kevin; Severino, Giuseppe;
Steffen, Matthias
Bibcode: 2008ApJ...681L.125S
Altcode:
Stably stratified fluids, such as stellar and planetary atmospheres,
can support and propagate gravity waves. On Earth these waves,
which can transport energy and momentum over large distances and can
trigger convection, contribute to the formation of our weather and
global climate. Gravity waves also play a pivotal role in planetary
sciences and modern stellar physics. They have also been proposed
as an agent for the heating of stellar atmospheres and coronae, the
exact mechanism behind which is one of the outstanding puzzles in solar
and stellar physics. Using a combination of high-quality observations
and 3D numerical simulations we have the first unambiguous detection
of propagating gravity waves in the Sun's (and hence a stellar)
atmosphere. Moreover, we are able to determine the height dependence of
their energy flux and find that at the base of the Sun's chromosphere it
is around 5 kW m-2. This amount of energy is comparable to
the radiative losses of the entire chromosphere and points to internal
gravity waves as a key mediator of energy into the solar atmosphere.
Title: Could We Have Forecast "The Day the Solar Wind Died"?
Authors: Leamon, Robert J.; McIntosh, Scott W.
Bibcode: 2008ApJ...679L.147L
Altcode:
In 1999 May an interval of unusually slow (<300 km s-1)
and rarefied (<1 cm-3) solar wind was observed upstream
of Earth by the ACE spacecraft. The event has been dubbed "The Day
the Solar Wind Died." We apply our solar wind forecast model to the
interval in question, to ask whether we could have predicted the
phenomenon. The model fails, but by the manner in which it fails, we
support the conclusion that the rarefaction was caused by a suppression
of coronal outflow from a region that earlier provided fast wind flow,
possibly caused by a rapid restructuring of solar magnetic fields.
Title: Velocities and thermal evolution of chromospheric spicules
Authors: de Pontieu, B.; McIntosh, S. W.; Tarbell, T.; Carlsson,
M. P.; Hansteen, V. H.
Bibcode: 2008AGUSMSP53A..06D
Altcode:
We use the Broadband Filter Imager (BFI) and Narrowband Filter
Imager (NFI) of the Solar Optical Telescope on Hinode to study the
thermal evolution and velocities developed by chromospheric plasma in
spicules. We use Dopplergrams made in the Na D 589.6 nm, Hα 656.3 nm
and Mg B 517.3 nm passbands, as well as filtergrams in the Ca H 396.8 nm
passband to study the spatio-temporal relationship between the various
spicular features. We compare those findings with synthesized images
based on line profiles computed from high-resolution 3D MHD numerical
simulations from the University of Oslo. We also use the Dopplergram
data to investigate the velocities that develop in the two types of
spicules that were reported previously. We perform statistical analysis
of apparent velocities in the plane of the sky and line-of-sight
velocities derived from Dopplergrams to disentangle the superposition
of Alfvenic wave amplitudes and field-aligned flows. We study these
properties for a variety of magnetic field configurations (coronal
holes, quiet Sun, active region). Finally, we focus on the formation
mechanism of spicules by analyzing spicular features in Dopplergrams
on the disk that were taken simultaneously with SP magnetograms. This
work was supported by NASA contract NNM07AA01C. The Hinode mission is
operated by ISAS/JAXA, NAOJ, NASA, STFC, ESA and NSC.
Title: WHI Targeted Campaigns on Coronal Holes and Quiet Sun: High
Resolution Observations of the Lower Atmosphere With IBIS
Authors: Cauzzi, G.; Reardon, K. P.; Rimmele, T.; Tritschler, A.;
Uitebroek, H.; Woeger, F.; Deforest, C.; McIntosh, S.
Bibcode: 2008AGUSMSH51A..02C
Altcode:
The Interferometric BIdimensional Spectrometer (IBIS) is a dual
Fabry-Perot instrument installed at the Dunn Solar Telescope that allows
two-dimensional spectroscopic observations in a variety of spectral
lines. The IBIS/DST will participate in the WHI targeted campaigns
on coronal holes (April 3-9) and quiet Sun dynamics (April 10-16)
performing simultaneous high-resolution observations of the dynamics of
the photosphere and chromosphere in the coordinated targets. The aim is
to obtain insights on the role of the lower atmosphere's dynamics and
energetics into the structuring of the coronal plasma and, possibly,
into the origin of the solar wind. In this paper we will present the
observations obtained as well as first results, and attempt to relate
them with recent work performed on quiet Sun chromospheric dynamics.
Title: Identifying the Distinctive Plasma Properties of Coronal Holes
Authors: Habbal, S. R.; Scholl, I.; McIntosh, S.
Bibcode: 2008AGUSMSP31D..08H
Altcode:
Interest in defining the distinguishing properties of coronal holes has
been ongoing for several decades, due in large part to the prevailing
view that they are the main source of the fast solar wind. So far, their
main distinct signature on the solar disk is reduced absorption in the
chromospheric He I 1083 nm line, and significantly reduced emission
in EUV emission lines formed at, or above, a temperature of a million
degrees. In this study, MDI line of sight photospheric magnetic field
measurements are combined with EIT solar disk intensities of the EUV
lines of Fe X 171 and Fe XII 195 A to define the boundaries of coronal
holes, following the technique recently described by Scholl and Habbal
(2007). By complementing this identification with coordinated SUMER Ne
VIII intensity and Doppler measurements, it is shown that coronal holes,
for the most part, are not the sole regions of outflow on the solar
surface. While these results provide a new step in identifying coronal
holes, they show that no single criterion can be used to distinguish a
number of their plasma properties from those of the surrounding quiet
Sun. Their underlying origin remains for the most part a puzzle.
Title: Chromospheric Flows in the Vicinity of Magnetic Features in
the Quiet Sun Observed with Hinode SOT
Authors: Tarbell, T.; de Pontieu, B.; Carlsson, M.; Hansteen, V.;
McIntosh, S.; Ichimoto, K.
Bibcode: 2008AGUSMSP41B..02T
Altcode:
The Narrowband Filter Imager of the Solar Optical Telescope on Hinode
can measure Doppler shifts and line-of- sight magnetic fields in two
lines with contributions from the low chromosphere: Na D 589.6 nm and
Mg b 517.3 nm. The SOT Spectro-Polarimeter also measures very accurate
vector magnetic fields and Doppler velocities in the photosphere. These
observations have diffraction-limited spatial resolution and superb
stability. We present examples of these measurements in quiet sun
at various disk positions. In addition to the expected granulation
and f- and p-modes, conspicuous longer-lived downflows are seen near
strong network flux elements. Transient upflows are also detected,
presumably the base of flows seen in spicules at the limb and H-alpha
mottles on the disk. Velocity features associated with emerging and
cancelling magnetic features are also described. The observations are
compared with synthesized images made from line profiles computed from
the University of Oslo 3-D MHD simulations. This work was supported by
NASA contract NNM07AA01C. The Hinode mission is operated by ISAS/JAXA,
NAOJ, NASA, STFC, ESA and NSC.
Title: Characterizing the Quiet Sun: Where is it?
Authors: McIntosh, S.; Quiet Sun Science Team
Bibcode: 2008AGUSMSH53A..02M
Altcode:
We will present and discuss results of the WHI Quiet Sun
Characterization Campaign of April 10-16, 2008. Using high spatial and
temporal resolution multi-wavelength observations from a broad suite
of observatories we made a detailed study of the response of the quiet
solar chromosphere, transition region and corona to the constantly
evolving photospheric magnetic field. These joint observations show
that there is no place in the solar atmosphere that is magnetically
or dynamically "quiet".
Title: High Frequency Acoustic Waves in the Sun's Atmosphere
Authors: Fleck, B.; Jefferies, S. M.; McIntosh, S. W.; Straus, T.;
Tarbell, T. D.
Bibcode: 2008AGUSMSP41B..04F
Altcode:
This year marks the 60th anniversary of two pioneering papers by
Schwarzschild (1948) and Biermann (1948), who independently proposed
that acoustic waves generated in the turbulent convection zone play
an important role in the heating of the chromosphere and corona. High
frequency acoustic waves have remained one of the leading contenders
for solving the heating problem of the non-magnetic chromospheres of
the Sun and late-type stars ever since. Earlier attempts to determine
the acoustic energy flux from ground were compromised by atmospheric
seeing, which has its biggest effect on the high frequency parts
of the observed signal. Recently, based on a comparison of TRACE
observations and 1-D simulations, Fossum & Carlsson (2005, 2006)
concluded that high-frequency acoustic waves are not sufficient to heat
the solar chromosphere. The same conclusion was reached by Carlsson et
al. (2007) from an analysis of Hinode SOT/BFI Ca II H and blue continuum
observations. Other authors (e.g. Cuntz et al. 2007; Wedemeyer-Boehm
et al. 2007, Kalkofen 2007), however, questioned these results for
a number of reasons. Because of its limited spatial resolution and
limited sensitivity there are inherent difficulties when comparing TRACE
observations with numerical simulations. Further, intensity oscillations
are difficult to interpret, as they result from a phase-sensitive mix of
density, temperature, and pressure fluctuations, and radiation transfer
effects may complicate the picture even more. Here we revisit the role
of high frequency acoustic waves in the Sun's atmosphere using high
cadence, high resolution Doppler velocity measurements obtained with
SOT/SP and SOT/NFI on Hinode.
Title: Reappraising Transition Region Line Widths in Light of Recent
Alfvén Wave Discoveries
Authors: McIntosh, Scott W.; De Pontieu, Bart; Tarbell, Theodore D.
Bibcode: 2008ApJ...673L.219M
Altcode: 2008arXiv0801.0671M
We provide a new interpretation of ultraviolet transition region
emission line widths observed by the SUMER instrument on the Solar
and Heliospheric Observatory (SOHO). This investigation is prompted
by observations of the chromosphere at unprecedented spatial and
temporal resolution from the Solar Optical Telescope (SOT) on Hinode
revealing that all chromospheric structures above the limb display
significant transverse (Alfvénic) perturbations. We demonstrate
that the magnitude, network sensitivity, and apparent center-to-limb
isotropy of the measured line widths (formed below 250,000 K) can be
explained by an observationally constrained forward model in which the
line width is caused by the line-of-sight superposition of longitudinal
and Alfvénic motions on the small-scale (spicular) structures that
dominate the chromosphere and low transition region.
Title: On the Mass and Energy Loading of Extreme-UV Bright Points
Authors: McIntosh, Scott W.
Bibcode: 2007ApJ...670.1401M
Altcode: 2007arXiv0708.0550M
We discuss the appearance of extreme-ultraviolet (EUV) bright points
(BPs) in the analysis of long-duration observations in the He II 304 Å
passband of the Solar and Heliospheric Observatory Extreme-ultraviolet
Imaging Telescope (SOHO EIT). The signature of the observed 304 Å
passband intensity fluctuations around the BPs suggests that the primary
source of the mass and energy supplied to the magnetic structure is
facilitated by relentless magnetoconvection-driven reconnection, forced
by the magnetic evolution of the surrounding supergranules. Furthermore,
we observe that if the magnetic conditions in the supergranules
surrounding the footpoints of the cool 304 Å BPs are sufficient (large
net imbalance with a magnetic field that closes beyond the boundaries
of the cell in which it originates), the magnetic topology comprising
the BP will begin to reconnect with the overlying corona, increasing
its visibility to hotter EUV passbands and possibly soft X-rays.
Title: Chromospheric Alfvénic Waves Strong Enough to Power the
Solar Wind
Authors: De Pontieu, B.; McIntosh, S. W.; Carlsson, M.; Hansteen,
V. H.; Tarbell, T. D.; Schrijver, C. J.; Title, A. M.; Shine, R. A.;
Tsuneta, S.; Katsukawa, Y.; Ichimoto, K.; Suematsu, Y.; Shimizu, T.;
Nagata, S.
Bibcode: 2007Sci...318.1574D
Altcode:
Alfvén waves have been invoked as a possible mechanism for the heating
of the Sun's outer atmosphere, or corona, to millions of degrees and
for the acceleration of the solar wind to hundreds of kilometers per
second. However, Alfvén waves of sufficient strength have not been
unambiguously observed in the solar atmosphere. We used images of
high temporal and spatial resolution obtained with the Solar Optical
Telescope onboard the Japanese Hinode satellite to reveal that the
chromosphere, the region sandwiched between the solar surface and
the corona, is permeated by Alfvén waves with strong amplitudes on
the order of 10 to 25 kilometers per second and periods of 100 to
500 seconds. Estimates of the energy flux carried by these waves and
comparisons with advanced radiative magnetohydrodynamic simulations
indicate that such Alfvén waves are energetic enough to accelerate
the solar wind and possibly to heat the quiet corona.
Title: Hinode and the Corona's Lower Boundary: Spicules and Alfven
Waves
Authors: de Pontieu, B.; McIntosh, S. W.; Hansteen, V.; Carlsson, M. P.
Bibcode: 2007AGUFMSH52C..08D
Altcode:
The lower boundary of the corona, or chromosphere, requires of order
100 times more energy than the corona itself, and provides the mass
to fill coronal loops. Yet the chromosphere and its coupling to the
corona is often overlooked. Recently, observations with the Solar
Optical Telescope (SOT) onboard Hinode and ground-based telescopes
combined with advanced numerical simulations have provided us with
unprecedented views and a better understanding of the (spicular)
dynamics of the chromosphere and how the lower boundary couples to
the corona and solar wind. We analyze high-resolution, high-cadence
Ca II and Hα observations of the solar chromosphere and find that the
dynamics of the magnetized chromosphere are dominated by at least two
different types of spicules. We show that the first type involves up-
and downward motion that is driven by shock waves that form when global
oscillations and convective flows leak into the chromosphere along
magnetic field lines on on 3-7 minute timescales. The second type of
spicules is much more dynamic: they form rapidly (in ~10s), are very
thin (<200km wide), have lifetimes of 10-150s (at any one height) and
seem to be rapidly heated to (at least) transition region temperatures,
sending material through the chromosphere at speeds of order 50-150
km/s. The properties of Type II spicules suggest a formation process
that is a consequence of magnetic reconnection. We discuss the impact of
both spicules types on the coronal mass and energy balance. Our analysis
of Hinode data also indicates that the chromosphere is permeated by
strong Alfvén waves. Both types of spicules are observed to carry
these Alfvén waves, which have significant amplitudes of order 20 km/s,
transverse displacements of order 500-1,000 km and periods of 150-400
s. Estimates of the energy flux carried by these Alfvén waves and
comparisons to advanced radiative MHD simulations indicate that these
waves most likely play a significant role in the acceleration of the
solar wind, and possibly the heating of the quiet Sun corona. We will
discuss the implications of these waves on the energy balance of the
lower atmosphere.
Title: Alfven Waves in the Solar Corona
Authors: Tomczyk, S.; McIntosh, S. W.; Keil, S. L.; Judge, P. G.;
Schad, T.; Seeley, D. H.; Edmondson, J.
Bibcode: 2007AGUFMSH21A0289T
Altcode:
We present observations of the coronal intensity, line-of-sight
velocity, and linear polarization obtained in the FeXIII 1074.7 nm
coronal emission line with the Coronal Multi-channel Polarimeter
(CoMP) instrument. Analysis of these observations reveal ubiquitous
upward propagating waves with phase speeds of 1-4 Mm/s and trajectories
consistent with the direction of the magnetic field inferred from the
linear polarization measurements. We can definitively identify these
as Alfvén waves. An estimate of the energy carried by the waves that
we spatially resolve indicates that they are unable to heat the solar
corona, however, unresolved waves may carry sufficient energy.
Title: Evidence of Coupled Large-scale Propagating MHD Waves in the
EUV Corona
Authors: Wills-Davey, M. J.; Sechler, M.; McIntosh, S. W.
Bibcode: 2007AGUFMSH31A0222W
Altcode:
We identify TRACE and SOHO-EIT EUV observations that contain EIT waves
or evidence of EIT waves in the form of loop oscillations. In each
case, we find instances of a "precursor" to the EIT wave--a much weaker
wave pulse that appears instigated by the same source as the EIT wave,
and travels in front of the pulse along the same trajectory. In each
case, the wave "precursor" leads to some form of coronal dynamics; we
observe either loop brightenings or, in one case, the initiation of an
EIT wave and a sympathetic coronal mass ejection. These "precursors"
are particularly notable in that they travel significantly faster--at
least 3 × - 5 × faster--than their corresponding EIT waves, achieving
minimum velocities of 1300-1600 km/s. We postulate that these wave
"percursors" are, in fact, MHD modes coupled to the EIT waves, and
may be a fast- mode-like component correlated with the EIT waves'
corresponding slow-mode-like component.
Title: Observing the Influence of Alfven Waves on the Energetics of
the Quiet Solar Corona and Solar Wind
Authors: McIntosh, S. W.; de Pontieu, B.; Tomczyk, S.
Bibcode: 2007AGUFMSH21A0288M
Altcode:
We will present and discuss recent observations of Alfvén waves in the
solar chromosphere, from the Solar Optical Telescope (SOT) on Hinode,
and in the corona, from HAO's ground-based Coronal Multi-channel
Polarimeter (CoMP). These observations unambiguously demonstrate, for
the first time, that the magnetic chromosphere and corona are riddled
with 3- and 5-minute (3-5mHz) Alfvénic oscillations predominantly
propagating outward into the heliosphere. The combined analysis of these
observations, augmented by spectroscopic data from SOHO/SUMER, provide
a compelling look at the influence and importance of ubiquitously
driven Alfvén waves in heating the quiet solar corona and driving
the solar wind. Indeed, we believe that these direct observations of
a low-frequency wave input must provoke a re-evaluation of solar wind
acceleration by high frequency (kHz) ion-cyclotron modes.
Title: On Connecting the Dynamics of the Chromosphere and Transition
Region with Hinode SOT and EIS
Authors: Hansteen, Viggo H.; de Pontieu, Bart; Carlsson, Mats;
McIntosh, Scott; Watanabe, Tetsuya; Warren, Harry P.; Harra, Louise K.;
Hara, Hirohisa; Tarbell, Theodore D.; Shine, Dick; Title, Alan M.;
Schrijver, Carolus J.; Tsuneta, Saku; Katsukawa, Yukio; Ichimoto,
Kiyoshi; Suematsu, Yoshinori; Shimizu, Toshifumi
Bibcode: 2007PASJ...59S.699H
Altcode: 2007arXiv0711.0487H
We use coordinated Hinode SOT/EIS observations that include
high-resolution magnetograms, chromospheric, and transition region
(TR) imaging, and TR/coronal spectra in a first test to study how
the dynamics of the TR are driven by the highly dynamic photospheric
magnetic fields and the ubiquitous chromospheric waves. Initial
analysis shows that these connections are quite subtle and require a
combination of techniques including magnetic field extrapolations,
frequency-filtered time-series, and comparisons with synthetic
chromospheric and TR images from advanced 3D numerical simulations. As a
first result, we find signatures of magnetic flux emergence as well as
3 and 5mHz wave power above regions of enhanced photospheric magnetic
field in both chromospheric, transition region, and coronal emission.
Title: Can High Frequency Acoustic Waves Heat the Quiet Sun
Chromosphere?
Authors: Carlsson, Mats; Hansteen, Viggo H.; de Pontieu, Bart;
McIntosh, Scott; Tarbell, Theodore D.; Shine, Dick; Tsuneta, Saku;
Katsukawa, Yukio; Ichimoto, Kiyoshi; Suematsu, Yoshinori; Shimizu,
Toshifumi; Nagata, Shin'ichi
Bibcode: 2007PASJ...59S.663C
Altcode: 2007arXiv0709.3462C
We use Hinode/SOT Ca II H-line and blue continuum broadband observations
to study the presence and power of high frequency acoustic waves at
high spatial resolution. We find that there is no dominant power at
small spatial scales; the integrated power using the full resolution of
Hinode (0.05'' pixels, 0.16'' resolution) is larger than the power in
the data degraded to 0.5'' pixels (TRACE pixel size) by only a factor
of 1.2. At 20 mHz the ratio is 1.6. Combining this result with the
estimates of the acoustic flux based on TRACE data of Fossum &
Carlsson (2006), we conclude that the total energy flux in acoustic
waves of frequency 5-40 mHz entering the internetwork chromosphere of
the quiet Sun is less than 800 W m$^{-2}$, inadequate to balance the
radiative losses in a static chromosphere by a factor of five.
Title: A Tale of Two Spicules: The Impact of Spicules on the Magnetic
Chromosphere
Authors: de Pontieu, Bart; McIntosh, Scott; Hansteen, Viggo H.;
Carlsson, Mats; Schrijver, Carolus J.; Tarbell, Theodore D.; Title,
Alan M.; Shine, Richard A.; Suematsu, Yoshinori; Tsuneta, Saku;
Katsukawa, Yukio; Ichimoto, Kiyoshi; Shimizu, Toshifumi; Nagata,
Shin'ichi
Bibcode: 2007PASJ...59S.655D
Altcode: 2007arXiv0710.2934D
We use high-resolution observations of the Sun in CaIIH (3968Å)
from the Solar Optical Telescope on Hinode to show that there are
at least two types of spicules that dominate the structure of the
magnetic solar chromosphere. Both types are tied to the relentless
magnetoconvective driving in the photosphere, but have very different
dynamic properties. ``Type-I'' spicules are driven by shock waves
that form when global oscillations and convective flows leak into
the upper atmosphere along magnetic field lines on 3--7minute
timescales. ``Type-II'' spicules are much more dynamic: they form
rapidly (in ∼ 10s), are very thin (≤ 200 km wide), have lifetimes
of 10-150s (at any one height), and seem to be rapidly heated to
(at least) transition region temperatures, sending material through
the chromosphere at speeds of order 50--150kms-1. The
properties of Type II spicules suggest a formation process that is
a consequence of magnetic reconnection, typically in the vicinity
of magnetic flux concentrations in plage and network. Both types of
spicules are observed to carry Alfvén waves with significant amplitudes
of order 20kms-1.
Title: Observational signatures of the interaction between acoustic
waves and the solar magnetic canopy
Authors: Moretti, P. F.; Jefferies, S. M.; Armstrong, J. D.; McIntosh,
S. W.
Bibcode: 2007A&A...471..961M
Altcode:
Aims:We show that the spatial distribution (and its variation
with frequency) of the power spectra of the velocity and intensity
signals, in and around solar active regions, is a manifestation of the
interaction of acoustic waves at the magnetic canopy.
Methods:
We analysed 6 h of simultaneous, full-disk, velocity and intensity
images obtained using the MOTH instrument tuned in the Na D2 line at
589 nm and K D1 line at 770 nm, and full-disk velocity images from
the SOHO/MDI experiment using the Ni line at 677 nm.
Results:
We propose that more than one type of magneto-acoustic-gravity wave
is required to explain the well-known phenomena of p-mode absorption
and power halos.
Title: Alfvén Waves in the Solar Corona
Authors: Tomczyk, S.; McIntosh, S. W.; Keil, S. L.; Judge, P. G.;
Schad, T.; Seeley, D. H.; Edmondson, J.
Bibcode: 2007Sci...317.1192T
Altcode:
Alfvén waves, transverse incompressible magnetic oscillations, have
been proposed as a possible mechanism to heat the Sun’s corona
to millions of degrees by transporting convective energy from the
photosphere into the diffuse corona. We report the detection of
Alfvén waves in intensity, line-of-sight velocity, and linear
polarization images of the solar corona taken using the FeXIII
1074.7-nanometer coronal emission line with the Coronal Multi-Channel
Polarimeter (CoMP) instrument at the National Solar Observatory, New
Mexico. Ubiquitous upward propagating waves were seen, with phase speeds
of 1 to 4 megameters per second and trajectories consistent with the
direction of the magnetic field inferred from the linear polarization
measurements. An estimate of the energy carried by the waves that we
spatially resolved indicates that they are too weak to heat the solar
corona; however, unresolved Alfvén waves may carry sufficient energy.
Title: The SoHO/EIT Brightpoint Database: Mining The Database
For Science
Authors: Davey, Alisdair R.; McIntosh, S.
Bibcode: 2007AAS...210.9509D
Altcode: 2007BAAS...39R.327D
We update the analysis of McIntosh & Gurman [2005, Sol. Phys.,
228, 285] to incorporate changes to the automatic EUV Bright Point
(BP) detection algorithm of data from the Extreme-ultraviolet
Imaging Telescope (EIT) on the Solar and Heliospheric Observatory
(SOHO). We discuss the implementation of the BP catalog as a searchable
database for the community and some of the basic manipulations on that
database. We demonstrate a subset of the scientific results that can
be obtained from large scale BP studies by concentrating on the highest
cadence 195 data from July 2001.
Title: Internal Gravity Waves and their Role in the Energetics of
the Solar Atmosphere
Authors: Fleck, Bernard; Straus, T.; Jefferies, S.; McIntosh, S. W.;
Severino, G.; Steffen, M.
Bibcode: 2007AAS...210.2410F
Altcode: 2007BAAS...39..130F
Internal gravity waves are believed to be excited by convective
overshoot in the solar atmosphere. We compare the results from numerical
simulations of the overshoot region of compressible convection into a
stable photosphere, with observations of the velocity field at several
heights in the solar atmosphere. We find a consistent picture for the
quiet middle/upper photosphere in which internal gravity waves are the
dominant phenomenon at low frequencies (< 2.5 mHz). We estimate the
contribution of these waves to the energy balance in the photosphere
and low chromosphere.
Title: Observational Evidence For The Ubiquity Of Strong Alfven
Waves In The Magnetized Chromosphere
Authors: De Pontieu, Bart; McIntosh, S. W.; Carlsson, M.; Hansteen,
V. H.; Schrijver, C. J.; Tarbell, T. D.; Title, A.; SOT Team
Bibcode: 2007AAS...210.9415D
Altcode: 2007BAAS...39R.219D
Hinode/SOT Ca II broadband observations show that Alfven waves with
significant amplitudes of order 10-20 km/s and periods of 150-300 s are
extremely ubiquitous in the magnetized middle to upper chromosphere. Our
observations focus on spicules at the limb, and straw-like features
associated with network and plage on the disk. We find that the
weak straw-like features and most spicules all undergo significant
transverse motions that are driven by Alfven waves. These waves are
seen to propagate both up- and downward, and may carry an energy flux
that is significant compared to both the local, coronal and solar wind
energy balance. We will provide estimates of the energy flux carried
by these waves, and will compare our observations with Alfven waves
that are observed in 3D numerical simulations that include advanced
radiative transfer treatment for the chromosphere. This work was
supported by NASA contract NNM07AA01C.
Title: Connecting The Dynamics Of The Chromosphere And Transition
Region With Hinode/sot And Eis
Authors: Hansteen, Viggo H.; McIntosh, S.; De Pontieu, B.; Carlsson,
M.; SOT Team
Bibcode: 2007AAS...210.9430H
Altcode: 2007BAAS...39..222H
We will use coordinated Hinode SOT/EIS observations that include
high-resolution magnetograms, chromospheric and TR imaging and
TR/coronal spectra to study how the dynamics of the TR are driven by
the higly dynamic photospheric magnetic fields and the ubiquitous
chromospheric waves. Using travel time analysis, magnetic field
extrapolations, frequency filtered timeseries and comparisons with
synthetic chromospheric and TR images from advanced 3D numerical
simulations, we will study and establish how the dynamics of the
photosphere, chromosphere and TR are connected.
Title: Magneto-acoustic Waves And Their Role In The Energetics And
Dynamics Of The Solar Chromosphere
Authors: Jefferies, Stuart; De Pontieu, B.; McIntosh, S.; Hansteen,
V. H.
Bibcode: 2007AAS...21012004J
Altcode: 2007BAAS...39..245J
We analyze a diverse set of observations obtained with SOHO and
TRACE, as well as with MOTH and the Swedish 1 m Solar Telescope to
show that sound waves play an important role in shaping the structure
and energetics of the magnetized chromosphere. Travel time analysis
of TRACE, MOTH and SST observations and comparisons with numerical
simulations show that normally evanescent 5 minute p-mode oscillations
leak into the chromosphere along flux tubes that are inclined with
the vertical. Comparisons of SST data of fibril-like jets above
active region plage and quiet Sun mottles with advanced radiative
MHD simulations show how these oscillations develop into slow mode
magnetoacoustic shocks that drive spicule-like chromospheric jets up
to coronal heights. The leaking waves not only drive much of the
dynamics of the magnetized chromosphere: Doppler measurements from the
MOTH instrument at several heights in the atmosphere show that the total
energy flux carried by these leaking waves may play a significant role
in the energy balance of the magnetized chromosphere. We describe
first approaches to determine more precisely how and where the wave
energy is deposited in the low atmosphere.
Title: The Posteruptive Evolution of a Coronal Dimming
Authors: McIntosh, Scott W.; Leamon, Robert J.; Davey, Alisdair R.;
Wills-Davey, Meredith J.
Bibcode: 2007ApJ...660.1653M
Altcode: 2007astro.ph..1347M
We discuss the posteruptive evolution of a ``coronal dimming'' based
on observations of the EUV corona from the Solar and Heliospheric
Observatory and the Transition Region and Coronal Explorer (TRACE). This
discussion highlights the roles played by magnetoconvection-driven
magnetic reconnection and the global magnetic environment of the
plasma in the ``filling'' and apparent motion of the region following
the eruption of a coronal mass ejection (CME). A crucial element in
our understanding of the dimming region's evolution is developed by
monitoring the disappearance and reappearance of bright TRACE ``moss''
around the active region that gives rise to the CME. We interpret the
change in the TRACE moss as a proxy of the changing coronal magnetic
field topology behind the CME front. We infer that the change in the
global magnetic topology also results in a shift of the energy balance
in the process responsible for the production of the moss emission while
the coronal magnetic topology evolves from closed to open and back to
closed again because, following the eruption, the moss reforms around
the active region in almost exactly its pre-event configuration. As a
result of the moss's evolution, combining our discussion with recent
spectroscopic results of an equatorial coronal hole, we suggest that
the interchangeable use of the term ``transient coronal hole'' to
describe a coronal dimming is more than just a simple coincidence.
Title: A Tale of Two Spicules
Authors: McIntosh, Scott W.; De Pontieu, B.; Carlsson, M.; Hansteen,
V. H.; Schrijver, C. J.; Tarbell, T. D.; Title, A. M.; SOT Team
Bibcode: 2007AAS...210.9414M
Altcode: 2007BAAS...39..219M
Hinode/SOT Ca II broadband images and movies show that there are
several different types of spicules at the limb. These different
types are distinguished by dynamics on different timescales. The
first type involves up- and downward motion on timescales of 3-5
minutes. The dynamics of these spicules are very similar to those of
fibrils and mottles as observed on the disk. Recent work suggests that
these are driven by slow-mode magnetoacoustic shocks that form when
convective flows and global oscillations leak into the chromosphere
along magnetic flux tubes. The second type is much more dynamic with
typical lifetimes of 10-60 s. These spicules are characterized by
sudden appearance and disappearance that may be indicative of rapid
heating to TR temperatures. We will describe the properties of these
spicules in various magnetic environments (coronal hole, quiet Sun,
active region) and study the possible role of reconnection in driving
the second type of spicules. In addition, we will perform detailed
comparisons of these different types of jets with synthetic Ca images
derived from advanced 3D numerical simulations that encompass the
convection zone up through the corona.
Title: Can High Frequency Acoustic Waves Heat the Quiet Sun
Chromosphere?
Authors: Carlsson, Mats P. O.; De Pontieu, B.; Tarbell, T.; Hansteen,
V. H.; McIntosh, S.; SOT Team
Bibcode: 2007AAS...210.6306C
Altcode: 2007BAAS...39..172C
We use Hinode/SOT Ca II, G-band and blue continuum broadband
observations to study the presence and power of high frequency acoustic
waves at high spatial resolution. Previous observations with TRACE,
which were limited by the 1 arcsec resolution, and 1D numerical
simulations (Fossum & Carlsson, 2005) have been used to constrain
the possible role of high frequency waves in the heating of the quiet
Sun chromosphere. We will use the higher spatial resolution Hinode
data and comparisons with both 1D and 3D numerical models to study
the amount of high frequency power at smaller scales, and whether that
power is sufficient to heat the quiet Sun chromosphere.
Title: Empirical Solar Wind Forecasting from the Chromosphere
Authors: Leamon, R. J.; McIntosh, S. W.
Bibcode: 2007ApJ...659..738L
Altcode: 2007astro.ph..1348L
Recently, we correlated the inferred structure of the solar
chromospheric plasma topography with solar wind velocity and composition
data measured at 1 AU. We now offer a physical justification of these
relationships and present initial results of an empirical prediction
model based on them. While still limited by the fundamentally complex
physics behind the origins of the solar wind and how its structure
develops in the magnetic photosphere and expands into the heliosphere,
our model provides a near-continuous range of solar wind speeds and
composition quantities that are simply estimated from the inferred
structure of the chromosphere. We suggest that the derived quantities
may provide input to other, more sophisticated, prediction tools or
models such as those that study coronal mass ejection (CME) propagation
and solar energetic particle (SEP) generation.
Title: Does High Plasma-β Dynamics ``Load'' Active Regions?
Authors: McIntosh, Scott W.
Bibcode: 2007ApJ...657L.125M
Altcode: 2007astro.ph..2093M
Using long-duration observations in the He II 304 Å passband of SOHO
EIT, we investigate the spatial and temporal appearance of impulsive
intensity fluctuations in the pixel light curves. These passband
intensity fluctuations come from plasma emitting in the chromosphere,
in the transition region, and in the lowest portions of the corona. We
see that they are spatially tied to the supergranular scale and
that their rate of occurrence is tied to the unsigned imbalance of
the magnetic field in which they are observed. The signature of the
fluctuations (in space and time) is consistent with their creation
by magnetoconvection-forced reconnection, which is driven by the flow
field in the high-β plasma. The signature of the intensity fluctuations
around an active region suggests that the bulk of the mass and energy
going into the active region complex observed in the hotter coronal
plasma is supplied by this process, dynamically forcing the looped
structure from beneath.
Title: Observations Supporting the Role of Magnetoconvection in
Energy Supply to the Quiescent Solar Atmosphere
Authors: McIntosh, Scott W.; Davey, Alisdair R.; Hassler, Donald M.;
Armstrong, James D.; Curdt, Werner; Wilhelm, Klaus; Lin, Gang
Bibcode: 2007ApJ...654..650M
Altcode: 2006astro.ph..9503M
Identifying the two physical mechanisms behind the production and
sustenance of the quiescent solar corona and solar wind poses two of
the outstanding problems in solar physics today. We present analysis of
spectroscopic observations from the Solar and Heliospheric Observatory
that are consistent with a single physical mechanism being responsible
for a significant portion of the heat supplied to the lower solar corona
and the initial acceleration of the solar wind; the ubiquitous action
of magnetoconvection-driven reprocessing and exchange reconnection of
the Sun's magnetic field on the supergranular scale. We deduce that
while the net magnetic flux on the scale of a supergranule controls the
injection rate of mass and energy into the transition region plasma,
it is the global magnetic topology of the plasma that dictates whether
the released ejecta provides thermal input to the quiet solar corona
or becomes a tributary that feeds the solar wind.
Title: An Empirical Solar Wind Forecast Model From The Chromosphere
Authors: Leamon, R. J.; McIntosh, S. W.
Bibcode: 2006AGUFMSH44A..08L
Altcode:
Recently, we [McIntosh and Leamon, ApJL, 624, 117, 2005] correlated
the inferred topography of the solar chromospheric plasma with in situ
solar wind velocity and composition data measured at 1~AU. Specifically,
the measured separation in height of the TRACE 1600Å\ and 1700Å\
UV band pass filters correlate very strongly with solar wind
velocity and inversely with the ratio of ionic oxygen (O^{7+/O^{6+}})
densities. Here, we build on our previous results by presenting initial
results of a model developed to so predict interplanetary solar wind
conditions, using SOHO/MDI magnetograms with 96 minute cadence as
proxies of chromospheric topography as input. Specifically, we use the
observed correlation between the measured chromospheric travel-time
and the magnetic field strength to allow us to convert the into a
(reasonable) full-disk travel-time diagnostic (in place of limited
field of view TRACE observations). Maps of full-disk travel-time are
scaled to wind diagnostic maps which are then "forward" mapped into
the heliosphere using a PFSS model. The resulting wind forecast matches
the observed state of the solar wind remarkably well for a simple model.
Title: The Role of Magnetoconvection in the Evolution of Active
Regions Before, During and After the Eruption of Coronal Mass
Ejections
Authors: McIntosh, S. W.; Leamon, R. J.
Bibcode: 2006AGUFMSH43B1529M
Altcode:
We discuss the pre-eruptive evolution of an active region filament
and the evolution of the ensuing post-eruptive "coronal dimming"
based on observations of the EUV corona from the Solar and Heliospheric
Observatory and the Transition Region and Coronal Explorer. We speculate
that the erosion of coronal loop footpoints anchored in the weakest
magnetic portions of an active region by magneto-convective flux
emergence driven reconnection acts as a stochastic "tether cutting"
mechanism. We discuss how this erosion of tethering magnetic flux is
capable of creating a topological instability and eventual coronal
mass ejection (CME) eruption. The magnetoconvection-driven magnetic
reconnection and the global magnetic enviroment of the plasma are
equally important in the "filling" and apparent motion of the region
following the eruption of the CME. Further, we speculate that coronal
dimmings could pose a potential secondary source of driving momentum
to the CMEs that cause their initial appearance.
Title: Low-frequency magneto-acoustic waves in the solar chromosphere
Authors: Jefferies, S. M.; McIntosh, S. W.; Armstrong, J. D.; Bogdan,
T. J.; Cacciani, A.; Fleck, B.
Bibcode: 2006ESASP.624E..16J
Altcode: 2006soho...18E..16J
No abstract at ADS
Title: Magnetoacoustic Portals and the Basal Heating of the Solar
Chromosphere
Authors: Jefferies, Stuart M.; McIntosh, Scott W.; Armstrong, James
D.; Bogdan, Thomas J.; Cacciani, Alessandro; Fleck, Bernhard
Bibcode: 2006ApJ...648L.151J
Altcode:
We show that inclined magnetic field lines at the boundaries of
large-scale convective cells (supergranules) provide ``portals''
through which low-frequency (<5 mHz) magnetoacoustic waves can
propagate into the solar chromosphere. The energy flux carried by
these waves at a height of 400 km above the solar surface is found
to be a factor of 4 greater than that carried by the high-frequency
(>5 mHz) acoustic waves, which are believed to provide the dominant
source of wave heating of the chromosphere. This result opens up
the possibility that low-frequency magnetoacoustic waves provide a
significant source of energy for balancing the radiative losses of
the ambient solar chromosphere.
Title: Observing the Modification of the Acoustic Cutoff Frequency
by Field Inclination Angle
Authors: McIntosh, Scott W.; Jefferies, Stuart M.
Bibcode: 2006ApJ...647L..77M
Altcode:
We use observations of a sunspot from the Transition Region and
Coronal Explorer (TRACE) spacecraft to demonstrate observationally
the modification of the acoustic cutoff frequency in the lower solar
chromosphere by the changing the inclination of the magnetic field as
first predicted theoretically by Bel & Leroy.
Title: Low-frequency magneto-acoustic waves in the solar chromosphere
Authors: Jefferies, S. M.; McIntosh, S. W.; Armstrong, J. D.; Cacciani,
A.; Bogdan, T. J.; Fleck, B.
Bibcode: 2006IAUJD...3E..62J
Altcode:
We demonstrate that low-frequency (< 5 mHz) propagating
magneto-acoustic waves provide a larger source of energy for balancing
the radiative losses of the solar chromosphere than their high-frequency
(> 5 mHz) counterparts. The low-frequency waves, which are normally
evanescent in the solar atmosphere, are able to propagate through
"acoustic portals" that exist in areas of strong, significantly
inclined (> 30° with respect to the vertical), magnetic field. Such
conditions are found both in active regions and at the boundaries of
supergranules. The latter implies that acoustic portals are omnipresent
over the solar surface and throughout the magnetic activity cycle,
an essential prerequisite for any baseline heating mechanism.
Title: Empirical Solar Wind Forecasting from the Chromosphere
Authors: Leamon, R.; McIntosh, S. W.
Bibcode: 2006ESASP.617E..13L
Altcode: 2006soho...17E..13L
No abstract at ADS
Title: Investigating SUMER Coronal Hole Observations: A Robust Method
of Raster Reduction
Authors: Davey, Alisdair R.; McIntosh, Scott W.; Hassler, Donald M.
Bibcode: 2006ApJS..165..386D
Altcode:
We present a physically constrained, comprehensive, and robust means
of reducing long-duration spectroscopic raster observations made in
the important 1530-1555 Å wavelength range by the Solar Ultraviolet
Measurements of Emitted Radiation (SUMER) instrument on the Solar and
Heliospheric Observatory (SOHO). Our method performs corrections in
spatial, spectral, and temporal domains following application of the
standard SUMER data reduction package to minimize the net Doppler
shift of neutral and singly ionized silicon emission lines in the
chromosphere. We have applied this method to seven raster observations
of the same equatorial coronal hole acquired over a 5 day period, 1999
November 3-8, and to the well-studied observations of 1996 September
21-22. This technique allows us to make physically consistent analyses
of multiple SUMER rasters and will aid in future investigations
of the solar ``rest'' wavelength of the important Ne VIII 770 Å
emission line and, as a result, of the properties of transition region
blueshifts-specifically, their correlation to multithermal radiance
structure, supergranular network patterns, and the coronal magnetic
environment at the perceived lower boundary of solar wind outflow.
Title: Simple Magnetic Flux Balance as an Indicator of Ne VIII
Doppler Velocity Partitioning in an Equatorial Coronal Hole
Authors: McIntosh, Scott W.; Davey, Alisdair R.; Hassler, Donald M.
Bibcode: 2006ApJ...644L..87M
Altcode: 2006astro.ph..5565M
We present a novel investigation into the relationship between simple
estimates of magnetic flux balance and the Ne VIII Doppler velocity
partitioning of a large equatorial coronal hole observed by the Solar
Ultraviolet Measurements of Emitted Radiation spectrometer (SUMER) on
the Solar and Heliospheric Observatory in 1999 November. We demonstrate
that a considerable fraction of the large-scale Doppler velocity
pattern in the coronal hole can be qualitatively described by simple
measures of the local magnetic field conditions, that is, the relative
imbalance of magnetic polarities and the radial distance required to
balance local flux concentrations with those of opposite polarity.
Title: Low-frequency Magneto-acoustic Waves In The Solar Chromosphere
Authors: Fleck, Bernard; Jefferies, S. M.; McIntosh, S. W.; Armstrong,
J. D.; Cacciani, A.; Bogdan, T. J.
Bibcode: 2006SPD....37.0206F
Altcode: 2006BAAS...38..662F
We demonstrate that low-frequency (< 5 mHz) propagating
magneto-acoustic waves provide a larger source of energy for balancing
the radiative losses of the solar chromosphere than their high-frequency
(> 5 mHz) counterparts. The low-frequency waves, which are normally
evanescent in the solar atmosphere, are able to propagate through
"acoustic portals” that exist in areas of strong, significantly
inclined (> 30° with respect to the vertical), magnetic field. Such
conditions are found both in active regions and at the boundaries of
supergranules. The latter implies that acoustic portals are omnipresent
over the solar surface and throughout the magnetic activity cycle,
an essential prerequisite for any baseline heating mechanism.
Title: Exploring High Time Resolution Coronal Dynamics with the
Rapid Acquisition Imaging Spectrograph (RAISE) Sounding Rocket Program
Authors: Hassler, Donald W.; DeForest, C. E.; McIntosh, S.; Slater,
D.; Ayres, T.; Thomas, R.; Scheuhle, U.; Michaelis, H.; Mason, H.
Bibcode: 2006SPD....37.3706H
Altcode:
The Rapid Acquisition Imaging Spectrograph (RAISE) is a next-generation
high resolution imaging spectrograph to study the dynamics of the
solar chromosphere and corona on time scales as short as 100 ms. High
speed imaging from TRACE has shown that rapid motions and reconnection
are central to the physics of the transition region and corona, but
cannot resolve the differences between propagating phenomena and bulk
motion. SoHO/CDS and SoHO/SUMER have yielded intriguing measurements
of motion and heating in the solar atmosphere, and Solar-B/EIS will
capture EUV spectra of flares in progress; but no currently planned
instrument can capture spectral information in the chromosphere,
transition region, or cool corona on the 1-10 Hz time scale required for
few-second cadence spectral imaging or rapid wave motion studies. RAISE
is uniquely suited to exploring this hard-to-reach domain.The first
flight of RAISE is scheduled for October 24, 2006 (Flight 36.219 US)
and will focus on the study of high frequency, small-scale dynamics
of active region structures and the high frequency wave structure
associated with these active regions.
Title: Genesis of AR NOAA10314
Authors: Morita, S.; McIntosh, S. W.
Bibcode: 2005ASPC..346..317M
Altcode:
In March 2003, over the space of six days, 37 (including 2 X-class)
flares occurred in the newly emerged AR NOAA10314 as it evolved
from a dual-dipolar configuration to an incredibly complex magnetic
entity only 150 hours later. We study the evolution of the coronal
structures of this young and prolific active region using SOHO/EIT
195Å and SOHO/MDI magnetogram observations. Since this active region
appeared in a coronal hole, its evolution gives us various clues to
understand the relation of magnetic field topology and flare activity
in a relatively clean coronal environment. We find that at least 31
of the 37 events (including the 2 X-class flares) occurred along the
same magnetic inversion line between the two dipoles. In this short
paper assess how the numerous flares drove the topological changes in
the coronal structures above active region.
Title: Chromospheric Origins of the Solar Wind: Composition and
Correlations
Authors: Leamon, R. J.; McIntosh, S. W.
Bibcode: 2005AGUSMSH11C..04L
Altcode:
Diagnostics of atmospheric "depth" in the chromosphere are made
for several observing periods in active, coronal hole and quiet Sun
regions. We track the coronal outflows from these regions to 1 AU using
a ballistic travel time approximation and correlate the chromospheric
quantities with counterpart in situ quantities from the same packets
of plasma Recently, we1 have shown that derived diagnostic quantities
correlate very strongly with solar wind velocity and inversely with the
ratio of ionic oxygen composition (O7+/O6+). We extend this work to show
that strong correlations exist between the state of the chromosphere
and other in situ observables, including proton temperatures, alpha
particle temperatures and alpha/proton ratios. (1) McIntosh and Leamon,
ApJL, submitted 2005
Title: The TRACE Inter-Network Oscillations (INO) Program II:
Observations of Limb and Coronal Hole Regions
Authors: McIntosh, S. W.; Crotser, D.; Leamon, R. J.; Fleck, B.;
Tarbell, T. D.
Bibcode: 2005AGUSMSH13C..06M
Altcode:
We will present results of the TRACE Inter-Network Oscillations (INO)
observing program from 2003 to the present. The INO program uses
near-simultaneous observations in the 1600Å and 1700Å UV continuum
pass bands as an acoustic probe of chromospheric structure. In
this poster we will discuss the INO observations of limb, polar and
coronal hole regions and show the key results found, thus far. These
observations offer us a remote means to study the structure and behavior
of the chromopsheric plasma topography at a potential driving base
for the heliospheric plasma system.
Title: Nine Years Of Euv Bright Points
Authors: McIntosh, Scott W.; Gurman, Joseph B.
Bibcode: 2005SoPh..228..285M
Altcode:
We discuss early results derived from an algorithm that automates the
detection, cataloging, and analysis of extreme-ultraviolet (EUV) "bright
points" (BP) from 9 years of data acquired by the Extreme-ultraviolet
Imaging Telescope (EIT) on the Solar and Heliospheric Observatory
(SOHO). The algorithm relies upon the computation of a map of
"intensity significance"; this then contains the location of the EUV
BPs. By mapping the location of BPs in each image and linking them
through long sequences of EIT images we can describe the temporal
and spatial variations of the 1.3× 108 EUV BPs observed
by SOHO to date. We suggest that there is a considerable amount of
physical information about the solar coronal plasma that can be readily
gleamed from the BP detection database. In this paper we discuss only
a small portion of the possible correlations, but we point to the
possibility of BP lifetime distributions that are well described by
modified power-laws; the components of which vary with the different
temperature filters and with time over the present solar cycle.
Title: Acoustic Mapping of the Magnetic Canopy in the Solar
Chromosphere
Authors: Jefferies, S. M.; Armstrong, J. D.; Cacciani, A.; Finsterle,
W.; McIntosh, S. W.
Bibcode: 2005AGUSMSH13C..11J
Altcode:
We show that high-frequency acoustic waves can be used to map the
location where the gas and magnetic pressures of the plasma in the
solar chromosphere are comparable. This transition region, which can be
considered as a "magnetic canopy" where MHD waves can transform from one
type into another, is believe to play a key role in the flow of mass
and energy through the chromosphere. Results will be presented from
the analysis of 18 (uninterrupted) hours of simultaneous, full-disk,
velocity observations using the Ni (676 nm), K (770 nm) and Na (589 nm)
Fraunhofer lines (with the SOHO/MDI and MOTH/South Pole instruments),
and 106 (uninterrupted) hours of K and Na data (from the MOTH/South
Pole instrument). The MOTH data were acquired every 10 seconds and the
MDI data every 60 seconds. This work was funded by awards OPP-0087541
and OPP-0338251 from the National Science Foundation.
Title: The Complexity of Equatorial Coronal Holes
Authors: McIntosh, S. W.; Davey, A. R.; Hassler, D. M.
Bibcode: 2005AGUSMSP51B..05M
Altcode:
We will investigate the multi-thermal intensities, flow structures
and extrapolated magnetic structures in an massive equatorial coronal
holes that crossed the solar disk in early November of 1999. We will
use a large suite of observations from the MDI and SUMER instruments on
SOHO. We will use the insight developed from our understanding of the
multi-thermal coronal hole topography to propose a consistent picture
of solar wind structure at the base of the Sun-Earth Connection.
Title: Is There a Chromospheric Footprint of the Solar Wind?
Authors: McIntosh, S. W.; Leamon, R. J.
Bibcode: 2005ApJ...624L.117M
Altcode:
We correlate the inferred structure of the solar chromospheric
plasma topography with in situ solar wind velocity and composition
data measured at 1 AU. Diagnostics of atmospheric ``depth'' in the
chromosphere are made for several observing periods in active,
coronal hole, and quiet-Sun regions. We demonstrate that the
inferred chromospheric diagnostics correlate very strongly with
solar wind velocity and inversely with the ratio of ionic oxygen
(O+7/O+6) densities. These correlations suggest
that the structure of the solar wind is rooted deeper in the outer
solar atmosphere than has been previously considered.
Title: Travel Time and Phase Analysis of Waves in the Lower Solar
Chromosphere
Authors: Fleck, B.; Armstrong, J.; Cacciani, A.; de Pontieu, B.;
Finsterle, W.; Jefferies, S. M.; McIntosh, S. W.; Tarbell, T. D.
Bibcode: 2005AGUSMSH13C..04F
Altcode:
In an effort to better understand how the chromospheric plasma and
magnetic fields are guiding, converting and dissipating acoustic waves,
we analyze high-cadence time series taken in Na I D2 589.0 nm and K I
769.9 nm that were obtained with the Magneto Optical Filters at Two
Heights (MOTH) experiment at the South Pole in January 2003. These
data are complemented by a very high spatial resolution time series
taken in Na D with the Swedish Vacuum Solar Telescope in June 1992. The
travel time maps, power maps, and phase diagrams show some unexpected
behaviour, in particular in and around active regions.
Title: The TRACE Inter-Network Oscillations (INO) Program I: Probing
Chromospheric Topography
Authors: McIntosh, S. W.; Bernhard, F.; Tarbell, T. D.
Bibcode: 2005AGUSMSH13C..05M
Altcode:
We will present results of the TRACE Inter-Network Oscillations (INO)
observing program from 2003 to the present. The INO program uses
near-simultaneous observations in the 1600Å and 1700Å UV continuum
pass bands as an acoustic probe of chromospheric structure. In the
two years of INO observations we have studied a large number of quiet
chromosphere and active regions as well as regions of the chromosphere
under coronal holes. In this poster we will discuss the diagnostic
methods applied to analyze the INO observations and the key results
found, thus far. These diagnostic methods offer us a remote means to
study the complex plasma topography of the solar chromosphere.
Title: Magnetic Topology and Wave Propagation in the Solar Atmosphere
Authors: Lawrence, J. K.; Cadavid, A. C.; McIntosh, S. W.; Berger,
T. E.
Bibcode: 2005AGUSMSH13C..01L
Altcode:
We analyze a 9 hr sequence of simultaneous, high resolution, 21 s
cadence SVST G-band and K-line solar filtergrams plus magnetograms
of lower cadence and resolution. The data include both network and
internetwork areas (Berger and Title 2001, Cadavid, et al. 2003,
Lawrence, et al. 2003). Time series of the G-band and K-line data are
compared after filtering by a Morlet wavelet transform of period 2.5
min. On the average, the K-line signal is delayed by several seconds
after the G-band signal Δ T = 8.6 ± 0.1 s for weak (|BZ| < 50 G)
magnetic field in internetwork but Δ T = 7.2 ± 0.1 s for weak field
in an area including network. The internetwork has no strong fields,
but in network (|BZ| > 80 G) the mean delay time drops to Δ T =
3.4 ± 0.3 s. This is consistent with results by McIntosh, Fleck and
Tarbell (2004) using TRACE 1600Å and 1700Å UV image series. Our
principal result is that the time delay is greater in the internetwork
than in the network by 1.4 ± 0.1 s, even for the same local magnetic
field strength. This suggests that the difference must be an effect
of the field topology. Spatial maps of time delays, in comparison
to maps of such topological quantities as the height in the solar
atmosphere at which the plasma β = 1, offer additional details of the
relationship between wave propagation and the magnetic fields in the
solar atmosphere. This work was supported in part by grants NSF-ATM
9987305 and NASA-NAG5-10880. The SVST is operated by the Swedish
Royal Academy of Sciences at the Spanish Observatorio del Roque de
los Muchachos of the Instituto de Astrofisica de Canarias. Berger,
T.E. and Title, A.M. 2001, ApJ, 553, 449. Cadavid, A.C., et al. 2003,
ApJ, 586, 1409. Lawrence, J.K., et al. 2003, ApJ, 597, 1178. McIntosh,
S.W., Fleck, B. and Tarbell, T.D. 2004, ApJ, 609, L95.
Title: Nine Years of EIT Bright Points
Authors: McIntosh, S. W.; Gurman, J. B.
Bibcode: 2005AGUSMSP22A..03M
Altcode:
We discuss early results derived from an algorithm that automates the
detection, cataloging, and analysis of Extreme-ultraviolet (EUV) "Bright
Points" (BP) from nine years of data acquired by the Extreme-ultraviolet
Imaging Telescope (EIT) on the Solar and Heliospheric Observatory
(SOHO). In particular, we describe the temporal and spatial variations
of the 1.3x108 EUV BPs observed by SOHO to date.
Title: Doppler Shift Velocity Calculations of Multi-Wavelength Coronal
Diagnostic Spectrometer Data Using Various Background Corrections
Authors: Duffin, R. T.; Poland, A. I.; McIntosh, S. W.
Bibcode: 2004ESASP.575..545D
Altcode: 2004soho...15..545D
No abstract at ADS
Title: EIT &EUV Brightpoints Over the SOHO Mission so Far
Authors: McIntosh, S. W.; Gurman, J. B.
Bibcode: 2004ESASP.575..235M
Altcode: 2004soho...15..235M
No abstract at ADS
Title: Helioseismic Mapping of the Magnetic Canopy in the Solar
Chromosphere
Authors: Finsterle, W.; Jefferies, S. M.; Cacciani, A.; Rapex, P.;
McIntosh, S. W.
Bibcode: 2004ApJ...613L.185F
Altcode:
We determine the three-dimensional topography of the magnetic canopy
in and around active regions by mapping the propagation behavior of
high-frequency acoustic waves in the solar chromosphere.
Title: Chromospheric Oscillations in an Equatorial Coronal Hole
Authors: McIntosh, Scott W.; Fleck, Bernhard; Tarbell, Theodore D.
Bibcode: 2004ApJ...609L..95M
Altcode:
We report phase-difference and travel-time analyses of propagating
chromospheric oscillations in and around an equatorial coronal hole
as observed by TRACE. Our results suggest a significant change in
atmospheric conditions at the base of the chromosphere inside the
coronal hole relative to its boundary and quiet-Sun regions.
Title: Probing Chromospheric Structure with the TRACE Inter-Network
Oscillation Program
Authors: Fleck, B.; McIntosh, S. W.
Bibcode: 2004AAS...204.3717F
Altcode: 2004BAAS...36..711F
We discuss the structure and dynamics of the solar chromosphere through
the application of several diagnostics to the Transition Region and
Coronal Explorer (TRACE) Inter-Network Oscillation (INO) ''synoptic''
observing sequence. Using several newly developed diagnostics we
investigate the generation and interplay of the observed chromospheric
oscillations and the ubiquitous magnetic field that permeates the
TRACE field of view.
Title: High Time Cadence Observations with the Rapid Acquisition
Imaging Spectrograph (RAISE) Rocket Program
Authors: Ayres, T. R.; Hassler, D. M.; Slater, D.; DeForest, C. E.;
Mason, H.; McIntosh, S.; Thomas, R. J.
Bibcode: 2004AAS...204.9704A
Altcode: 2004BAAS...36..828A
The Rapid Acquisition Imaging Spectrograph (RAISE) is a next-generation
high resolution imaging spectrograph scheduled to fly on a NASA sounding
rocket in 2006 to study the dynamics of the solar chromosphere and
corona on time scales as short as 100 ms. High speed imaging from
TRACE has shown that rapid motions and reconnection are central to the
physics of the transition region and corona, but cannot resolve the
differences between propagating phenomena and bulk motion. SoHO/CDS and
SoHO/SUMER have yielded intriguing measurements of motion and heating
in the solar atmosphere, and Solar-B/EIS will capture EUV spectra of
flares in progress; but no currently planned instrument can capture
spectral information in the chromosphere, transition region, or cool
corona on the ∼ 1-10 Hz time scale required for few-second cadence
spectral imaging or rapid wave motion studies. RAISE is uniquely suited
to exploring this hard-to-reach domain. This work is supported
by NASA Grant NNG04WC01G to the Southwest Research Institute.
Title: Erratum: Continuum analysis of an avalanche model for solar
flares [ Phys. Rev. E 66, 056111 (2002)]
Authors: Liu, Han-Li; Charbonneau, Paul; Pouquet, Annick; Bogdan,
Thomas; McIntosh, Scott
Bibcode: 2004PhRvE..69e9904L
Altcode:
No abstract at ADS
Title: EUV Brightpoints over the cycle to date as observed by SOHO/EIT
Authors: McIntosh, S. W.; Young, C. A.; Gurman, J. B.
Bibcode: 2004AAS...204.9507M
Altcode: 2004BAAS...36..827M
We investigate the multi-wavelength, multiple timescale appearance of
Extreme Ultraviolet (EUV) brightpoints over the current solar cycle
through the eyes of SOHO's Extreme Ultraviolet Imaging Telescope
(EIT). Over the past 8 years EIT has built up an unprecidented dataset
to facilitate the study of these ubiquitous coronal phenomena. Using an
automated detection algorithm we explore their physical and statistical
characteristics over the cycle to-date and ponder the mechanism behind
their generation in several specific instances of note.
Title: Characteristic Scales of Chromospheric Oscillation Wave Packets
Authors: McIntosh, Scott W.; Smillie, Darren G.
Bibcode: 2004ApJ...604..924M
Altcode:
We use wavelet transforms to study the characteristic time scales
of chromospheric oscillation ``wave packets'' that are observed in
Transition Region and Coronal Explorer (TRACE) ultraviolet continuum
image time series. Using several data sets, we investigate the
statistical, spatial, and temporal intermittence of the number,
duration, mean frequency, and delay (``wait time'') between wave
packets in the time series data. Further, we demonstrate that these
characteristic values are consistent with newly developed pictures of
the wave-mode suppression and conversion by the chromospheric magnetic
``canopy.'' We propose that wavelet analysis may be fruitfully used
in diagnosing the structure of the chromosphere and in identifying
chromospheric oscillation wave packets temporally and spatially with
their photospheric sources.
Title: Detailed SUMER Observations of Coronal Loop Footpoint Dynamics
Authors: McIntosh, Scott W.; Poland, Arthur I.
Bibcode: 2004ApJ...604..449M
Altcode:
For the most part, the characteristics of heating in the open corona
and in closed coronal loops are determined by observing the emitted
plasma intensity as a function of position and comparing this with
model calculations. There are also some efforts that include observed
velocity and still others that use theoretical physical processes
such as electrodynamic or turbulent heating, for example. With a
view toward future modeling endeavors, we investigate the temporal
behavior of the intensity and velocity of a magnetic loop footpoint
as observed by SUMER on the Solar and Heliospheric Observatory (SOHO)
spacecraft as part of SOHO/TRACE Joint Observing Program 72. We study
these quantities in emission lines that were specifically chosen to
span the temperature domain of the upper chromospheric and transition
region plasmas (105-106 K). We discuss the
implications of these observations, suggest improvements, and present
some new avenues of exploration. The most significant result is the
demonstration of the importance of including the measurement of velocity
as a function of time in the loop footpoint region.
Title: Mapping the Chromospheric Plasma Topography Through
Chromospheric Oscillations
Authors: McIntosh, S. W.; Fleck, B.
Bibcode: 2004ESASP.547..149M
Altcode: 2004soho...13..149M
Recent research has shown that understanding the physical nature of
chromospheric oscillations hinges critically upon the understanding of
the plasma structure in which they are formed and observed. To this
end we discuss the mapping of the chromospheric plasma topography
through the analysis of simultaneous SOHO/MDI and TRACE time-series
observations through a combination of Fourier and Wavelet based analysis
techniques. We are able to construct a picture of the chromospheric
plasma and its interaction with the wave modes present. Such a picture
will focus studies on topographic regions that will form a simulation
test-bed for theories of modeconversion, dissipation and wave heating
in the solar chromosphere.
Title: Spatial Correlations of Phase Relationships in TRACE
Ultraviolet Bandpasses
Authors: McIntosh, S. W.; Fleck, B.
Bibcode: 2004IAUS..219..696M
Altcode:
No abstract at ADS
Title: Future Observations with the Rapid Acquisition Imaging
Spectrograph (RAISE)
Authors: Hassler, D. M.; Deforest, C. E.; Slater, D.; Ayres, T.;
Mason, H.; McIntosh, S.; Thomas, R.
Bibcode: 2004cosp...35.2280H
Altcode: 2004cosp.meet.2280H
The Rapid Acquisition Imaging Spectrograph (RAISE) is a next-generation
high resolution imaging spectrograph scheduled to fly on a NASA sounding
rocket in 2006 to study the dynamics of the solar chromosphere and
corona on time scales as short as 100 ms. High speed imaging from TRACE
has shown that rapid motions and reconnection are central to the physics
of the transition region and corona, but cannot resolve the differences
between propagating phenomena and bulk motion. SoHO/CDS and SoHO/SUMER
have yielded intriguing measurements of motion and heating in the
solar atmosphere, and Solar-B/EIS will capture EUV spectra of flares
in progress; but no currently planned instrument can capture spectral
information in the chromosphere, transition region, or cool corona
on the ~1-10 Hz time scale required for few-second cadence spectral
imaging or rapid wave motion studies. RAISE is uniquely suited to
exploring this hard-to-reach domain.
Title: Waves in the Magnetized Solar Atmosphere. II. Waves from
Localized Sources in Magnetic Flux Concentrations
Authors: Bogdan, T. J.; Carlsson, M.; Hansteen, V. H.; McMurry, A.;
Rosenthal, C. S.; Johnson, M.; Petty-Powell, S.; Zita, E. J.; Stein,
R. F.; McIntosh, S. W.; Nordlund, Å.
Bibcode: 2003ApJ...599..626B
Altcode:
Numerical simulations of wave propagation in a two-dimensional
stratified magneto-atmosphere are presented for conditions that
are representative of the solar photosphere and chromosphere. Both
the emergent magnetic flux and the extent of the wave source are
spatially localized at the lower photospheric boundary of the
simulation. The calculations show that the coupling between the
fast and slow magneto-acoustic-gravity (MAG) waves is confined to
thin quasi-one-dimensional atmospheric layers where the sound speed
and the Alfvén velocity are comparable in magnitude. Away from this
wave conversion zone, which we call the magnetic canopy, the two MAG
waves are effectively decoupled because either the magnetic pressure
(B2/8π) or the plasma pressure (p=NkBT)
dominates over the other. The character of the fluctuations observed
in the magneto-atmosphere depend sensitively on the relative location
and orientation of the magnetic canopy with respect to the wave source
and the observation point. Several distinct wave trains may converge
on and simultaneously pass through a given location. Their coherent
superposition presents a bewildering variety of Doppler and intensity
time series because (1) some waves come directly from the source while
others emerge from the magnetic canopy following mode conversion, (2)
the propagation directions of the individual wave trains are neither
co-aligned with each other nor with the observer's line of sight, and
(3) the wave trains may be either fast or slow MAG waves that exhibit
different characteristics depending on whether they are observed in
high-β or low-β plasmas (β≡8πp/B2). Through the
analysis of four numerical experiments a coherent and physically
intuitive picture emerges of how fast and slow MAG waves interact
within two-dimensional magneto-atmospheres.
Title: MHD Waves in Magnetic Flux Concentrations
Authors: Bogdan, T. J.; Carlsson, M.; Hansteen, V.; Zita, E. J.;
Stein, R. F.; McIntosh, S. W.
Bibcode: 2003AGUFMSH42B0535B
Altcode:
Results from 2D MHD simulations of waves in a stratified isothermal
atmosphere will be presented and analyzed. The waves are generated
by a localized piston source situated on the lower, photospheric,
boundary of the computational domain. A combination of fast and slow
magneto-atmospheric waves propagates with little mutual interaction
until they encounter the surface where the sound speed and the Alfven
speed are comparable in magnitude. The waves couple strongly in this
region and emerge with different amplitudes and phases. Owing to
this mode mixing and the large variation in the Alfven speed in the
magneto-atmosphere, the fluctuations observed at a given location are
often a superposition of both fast and slow waves which have traversed
different paths and have undergone different transformations during
their journies.
Title: Investigating the role of plasma topography on chromospheric
oscillations observed by TRACE
Authors: McIntosh, S. W.; Fleck, B.; Judge, P. G.
Bibcode: 2003A&A...405..769M
Altcode:
We present the results of an investigation into the interaction of
the topographic structure of the solar chromospheric plasma with the
wave modes manifesting themselves in the UV continua formed there. We
show that there is a distinct correlation between the inferred
plasma topography, the phase-differences between and suppression of
oscillations in different levels of the solar atmosphere. We interpret
these factors as evidence of interaction between the oscillations and
the extended magnetic ``canopy''. This work is based on the analysis of
joint observations made by the Solar and Heliospheric Observatory (SOHO)
spacecraft and the Transition Region and Coronal Explorer (TRACE).
Title: Some theoretical and algorithmic ideas in spectral line
fitting problems
Authors: Ireland, J.; McIntosh, S. W.
Bibcode: 2003SPD....34.0302I
Altcode: 2003BAAS...35..808I
We take another look at the issue of fitting spectral lines from two
different viewpoints. Firstly, we present a theoretical framework
that enables the exploration of spectrometer precisions. The theory
enables the discussion of theoretical precision limits to model
spectrometers. Some applications of the theory are presented and
discussed with reference to the Coronal Diagnostic Spectrometer
(CDS) and Solar Ultraviolet Measurements of Emitted Radiation
(SUMER) instruments on board the Solar and Heliospheric Observatory
(SOHO). Secondly, we discuss the application of genetic and simulated
annealing algorithms to line fitting problems in the context of the
theoretical framework described above. Such algorithms are of utility
in providing unbiased fits in a wide variety of spectra where more
traditional fitting routines have difficulty converging. This work is
funded via a NASA NRA 01-OSS-01 award.
Title: Chromospheric Oscillations observed by SUMER and TRACE:
Their Interplay with the Solar Plasma Topography
Authors: McIntosh, S. W.; Fleck, B.
Bibcode: 2003SPD....34.0701M
Altcode: 2003BAAS...35R.819M
We present the results of an investigation into the interaction of
wave modes with the solar chromospheric plasma's topography through
the analysis of joint SOHO/SUMER and TRACE observations. We show
that there is a distinct correlation between the inferred solar plasma
topography (specifically the height of the transition from a high to low
plasma-beta regime) and the phase differences between, and suppression
of, atmospheric/chromospheric oscillations in different levels of the
solar atmosphere. Indeed, we demonstrate that the spectroscopic signal
observed changes dramatically in the passage from the high to low beta
regimes. We propose that the dependences presented can be used as an
interpretative tool for simulations seeking to model chromospheric
oscillations and as a diagnostics of the plasma conditions in the
important region in the mid-chromosphere where the plasma-beta is of
order unity, through the signatures of the wave-modes present.
Title: Technologies for Monolithic Suspensions
Authors: Rowan, S.; Fejer, M. M.; Gustafson, E. K.; Route, R.; Cagnoli,
G.; Hough, J.; McIntosh, S.; Sneddon, P.
Bibcode: 2002nmgm.meet.1849R
Altcode:
Despite recent work 1 showing that thermo-elastic damping in
bulk sapphire is expected to produce a higher level of thermal noise
at low frequencies than previously predicted using loss measurements
made at several 10's of kHz 2,3, for typical designs of
advanced interferometers thermal noise from sapphire test masses can
still be lower than that expected from fused silica over portions
of the frequency range relevant for gravitational wave detection
4. For this to be the case, excess mechanical losses
associated with suspending the test masses or coating them as mirrors
must be suitably low.
Title: Continuum analysis of an avalanche model for solar flares
Authors: Liu, Han-Li; Charbonneau, Paul; Pouquet, Annick; Bogdan,
Thomas; McIntosh, Scott
Bibcode: 2002PhRvE..66e6111L
Altcode:
We investigate the continuum limit of a class of self-organized
critical lattice models for solar flares. Such models differ from the
classical numerical sandpile model in their formulation of stability
criteria in terms of the curvature of the nodal field, and are known
to belong to a different universality class. A fourth-order nonlinear
hyperdiffusion equation is reverse engineered from the discrete model's
redistribution rule. A dynamical renormalization-group analysis of the
equation yields scaling exponents that compare favorably with those
measured in the discrete lattice model within the relevant spectral
range dictated by the sizes of the domain and the lattice grid. We
argue that the fourth-order nonlinear diffusion equation that models
the behavior of the discrete model in the continuum limit is, in fact,
compatible with magnetohydrodynamics (MHD) of the flaring phenomenon
in the regime of strong magnetic field and the effective magnetic
diffusivity characteristic of strong MHD turbulence.
Title: Waves in magnetic flux concentrations: The critical role of
mode mixing and interference
Authors: Bogdan, T. J.; Rosenthal, C. S.; Carlsson, M.; Hansteen, V.;
McMurry, A.; Zita, E. J.; Johnson, M.; Petty-Powell, S.; McIntosh,
S. W.; Nordlund, Å.; Stein, R. F.; Dorch, S. B. F.
Bibcode: 2002AN....323..196B
Altcode:
Time-dependent numerical simulations of nonlinear wave propagation
in a two-dimensional (slab) magnetic field geometry show wave mixing
and interference to be important aspects of oscillatory phenomena in
starspots and sunspots. Discrete sources located within the umbra
generate both fast and slow MHD waves. The latter are compressive
acoustic waves which are guided along the magnetic field lines and
steepen into N-waves with increasing height in the spot atmosphere. The
former are less compressive, and accelerate rapidly upward through the
overlying low-beta portion of the umbral photosphere and chromosphere
(beta equiv 8pi p/ B2). As the fast wave fronts impinge
upon the beta ~ 1 penumbral ``magnetic canopy" from above, they
interfere with the outward-propagating field-guided slow waves, and
they also mode convert to (non-magnetic) acoustic-gravity waves as
they penetrate into the weak magnetic field region which lies between
the penumbral canopy and the base of the surrounding photosphere. In
a three-dimensional situation, one expects additional generation,
mixing and interference with the remaining torsional Alfvén waves.
Title: Conduction in the transition region?: Interpretation of DEMs
using SOHO/SUMER observations
Authors: McIntosh, Scott W.
Bibcode: 2002ESASP.508..271M
Altcode: 2002soho...11..271M
The role of classical heat conduction in the energy balance of
the Te domain of the transition region (105 -
106K) is explored. We consider variations in space and time
of the Differntial Emission Measure (DEM) inferred from high cadence
(10s) SUMER observations taken on May 17, 1998 as part of JOP72. In
particular, we show that the gradient of the DEM in the observed
region, irrespective of the spatial/temporal binning applied, is
3/2. We discuss the implications of this result.
Title: Trawling around in the Noise
Authors: Fleck, B.; McIntosh, S. W.
Bibcode: 2002AAS...200.3905F
Altcode: 2002BAAS...34..701F
We investigate the possible presence of low amplitude, high-frequency
oscillations in short time exposure SUMER timeseries. Using a variety
of profile fitting methods and a combination of real and synthetic
data we examine the detection thresholds and limits. As a result we
can assess the likelyhood that certain long-duration, high cadence,
SUMER datasets contain meaningful information about the propagation
of high frequency waves in the Solar Chromosphere and Transition Region.
Title: Geometrical properties of avalanches in self-organized critical
models of solar flares
Authors: McIntosh, Scott W.; Charbonneau, Paul; Bogdan, Thomas J.;
Liu, Han-Li; Norman, James P.
Bibcode: 2002PhRvE..65d6125M
Altcode:
We investigate the geometrical properties of avalanches in
self-organized critical models of solar flares. Traditionally, such
models differ from the classical sandpile model in their formulation of
stability criteria in terms of the curvature of the nodal field, and
belong to a distinct universality class. With a view toward comparing
these properties to those inferred from spatially and temporally
resolved flare observations, we consider the properties of avalanche
peak snapshots, time-integrated avalanches in two and three dimensions,
and the two-dimensional projections of the latter. The nature of the
relationship between the avalanching volume and its projected area is
an issue of particular interest in the solar flare context. Using our
simulation results we investigate this relationship, and demonstrate
that proper accounting of the fractal nature of avalanches can bring
into agreement hitherto discrepant results of observational analyses
based on simple, nonfractal geometries for the flaring volume.
Title: Waves in the Magnetized Solar Atmosphere. I. Basic Processes
and Internetwork Oscillations
Authors: Rosenthal, C. S.; Bogdan, T. J.; Carlsson, M.; Dorch,
S. B. F.; Hansteen, V.; McIntosh, S. W.; McMurry, A.; Nordlund, Å.;
Stein, R. F.
Bibcode: 2002ApJ...564..508R
Altcode:
We have modeled numerically the propagation of waves through magnetic
structures in a stratified atmosphere. We first simulate the propagation
of waves through a number of simple, exemplary field geometries in
order to obtain a better insight into the effect of differing field
structures on the wave speeds, amplitudes, polarizations, direction
of propagation, etc., with a view to understanding the wide variety of
wavelike and oscillatory processes observed in the solar atmosphere. As
a particular example, we then apply the method to oscillations in the
chromospheric network and internetwork. We find that in regions where
the field is significantly inclined to the vertical, refraction by
the rapidly increasing phase speed of the fast modes results in total
internal reflection of the waves at a surface whose altitude is highly
variable. We conjecture a relationship between this phenomenon and the
observed spatiotemporal intermittancy of the oscillations. By contrast,
in regions where the field is close to vertical, the waves continue
to propagate upward, channeled along the field lines but otherwise
largely unaffected by the field.
Title: Geometric Effects in Avalanche Models of Solar Flares:
Implications for Coronal Heating
Authors: McIntosh, S. W.; Charbonneau, P.
Bibcode: 2001ApJ...563L.165M
Altcode:
Observational inferences of the power-law frequency distribution of
energy release by solar flares, and in particular its logarithmic
slope αE, depend critically on the geometric relationship
assumed to relate the observed emitting area A and the underlying
emitting volume V. Recent results on the fractal nature of avalanches
in self-organized critical models for solar flares indicate that
this relationship is a power law V~Aγ with index
γ=1.41(+/-0.04). We show that when proper account is made for
the fractal geometry of the flaring volume, hitherto discrepant
observational inferences of αE are brought in much closer
agreement. The resulting values of αE lie tantalizingly
close, but still below the critical value αE=2.0, beyond
which Parker's conjecture of coronal heating by nanoflares is tenable.
Title: Can the SOI/MDI Detect White Light Flares?
Authors: Gregory, S. E.; Myers, D.; Tarbell, T.; McIntosh, S.; Bush, R.
Bibcode: 2001AGUFMSH42A0765G
Altcode:
We examine flares observed jointly with high spatial resolution by
the SOHO instrument the Solar Oscillation Investigation/Michelson
Doppler Imager (SOI/MDI) and the Transition Region and Coronal Explorer
(TRACE). These include a GOES X1.1 class flare on 6 June 2000 and an
X5.7 flare on 14 July 2000. The June flare data provide a unique set
of line profiles across the flare site which help us better understand
potential instrumental effects in the SOI/MDI response to flares. We
locate the photospheric footpoints of the flares in both the SOI/MDI
and TRACE intensity images and examine their relationship with the
magnetograms. We also show that some flare kernels show emission in
both the line and the continuum in SOI/MDI data.
Title: On the Nature of Magnetic Shadows in the Solar Chromosphere
Authors: McIntosh, S. W.; Judge, P. G.
Bibcode: 2001ApJ...561..420M
Altcode:
Recent multi-instrument spacecraft studies of the solar photosphere
and chromosphere have uncovered a feature-a ``magnetic shadow''-not
previously discussed in the literature. A region of the midchromosphere
neighboring, but not within, a network magnetic element exhibits
a suppression of both the mean UV line/continuum intensity and the
characteristic 3 minute oscillation that is clearly observed elsewhere
in apparently similar internetwork regions. The clearest cases appear
to occur rarely, and their properties stand in obvious contrast to the
well-known ``aureoles'' of enhanced variability seen surrounding some
plage regions. It is imperative to understand more clearly the nature
of the shadow region, not least because the suppressed atmospheric
heating within it has implications for heating processes elsewhere
in the chromosphere that are dependent on, or at least related to,
the 3 minute oscillation. Based on the measured photospheric magnetic
field, its upward extrapolation, and the appearance of spectral features
formed above the midchromosphere, we suggest that a shadow occurs when
magnetic structures, in a relatively weak background field, ``close''
locally within the chromosphere, suppressing the upward propagation
of magnetoatmospheric waves into the chromosphere.
Title: Avalanche models for solar flares (Invited Review)
Authors: Charbonneau, Paul; McIntosh, Scott W.; Liu, Han-Li; Bogdan,
Thomas J.
Bibcode: 2001SoPh..203..321C
Altcode:
This paper is a pedagogical introduction to avalanche models of solar
flares, including a comprehensive review of recent modeling efforts and
directions. This class of flare model is built on a recent paradigm in
statistical physics, known as self-organized criticality. The basic
idea is that flares are the result of an `avalanche' of small-scale
magnetic reconnection events cascading through a highly stressed coronal
magnetic structure, driven to a critical state by random photospheric
motions of its magnetic footpoints. Such models thus provide a natural
and convenient computational framework to examine Parker's hypothesis
of coronal heating by nanoflares.
Title: Waiting-Time Distributions in Lattice Models of Solar Flares
Authors: Norman, James P.; Charbonneau, Paul; McIntosh, Scott W.;
Liu, Han-Li
Bibcode: 2001ApJ...557..891N
Altcode:
It has recently been argued that the distribution of waiting times
between successive solar flares is incompatible with the prediction
of lattice models, which interpret flares as avalanches of magnetic
reconnection events within a stressed magnetic structure driven to
a state of self-organized criticality by stochastic motions of the
photospheric magnetic footpoints. Inspired by a suggestion recently
made by Wheatland, we construct modified lattice models driven by
a nonstationary random process. The resulting models have frequency
distributions of waiting times that include a power-law tail at long
waiting times, in agreement with observations. One model, based on a
random walk modulation of an otherwise stationary driver, yields an
exponent for the power-law tail equal to 2.51+/-0.16, in reasonable
agreement with observational inferences. This power-law tail survives
in the presence of noise and a detection threshold. These findings
lend further support to the avalanche model for solar flares.
Title: Wave Propagation in a Magnetized Atmosphere
Authors: Bogdan, T. J.; Rosenthal, C. S.; Carlsson, M.; McIntosh,
S.; Dorch, S.; Hansteen, V.; McMurry, A.; Nordlund, Å; Stein, R. F.
Bibcode: 2001AGUSM..SH41A01B
Altcode:
Numerical simulations of MHD wave propagation in plane-parallel
atmospheres threaded by non-trivial potential magnetic fields will be
presented, and their implications for understanding distinctions between
intranetwork and internetwork oscillations will be discussed. Our
findings basically confirm the conjecture of McIntosh et al. (2001,
ApJ 548, L237), that the two-dimensional surface where the Alfvén
and sound speeds coincide (i.e., where the plasma-β , the ratio of
gas to magnetic pressure, is of order unity) plays a fundamental
role in mediating the conversion between the fast-, intermediate-
(Alfvén), and slow-Magneto-Atmospheric-Gravity (MAG) waves. For
example, upward-propagating acoustic waves generated at the base of
the internetwork photosphere suffer significant downward reflection
when they encounter this β ≈ 1 surface. Close to the network, this
surface descends from the upper chromosphere and low corona (which
pertains in the internetwork cell interiors) down into the photosphere,
and so chromospheric oscillation `shadows' are predicted to surround
the network. In the network, strong vertical magnetic fields further
depress the β ≈ 1 surface below the surface layers where the
(magnetic field-aligned) acoustic waves (i.e., slow MAG-waves) are
generated. For frequencies in excess of the cutoff frequency, these
acoustic waves suffer little reflection from the overlying atmosphere
and they steepen as they progress upward.
Title: Correlated Wavelet Transforms of SOHO Chromospheric and
Transition Region Timeseries Observations
Authors: McIntosh, S. W.; Fleck, B.
Bibcode: 2001AGUSM..SH41A03M
Altcode:
We consider the wavelet transform study of correlated SOHO (SUMER,
CDS and EIT) time-series observations with a view to understanding
inter-network plasma structure along the line-of-sight. By implementing
wavelet transforms in a novel way we able to study the behavior of
upward propagating wave-packets as a function of their height in the
atmosphere. Using this information we will infer properties of the
inter-network thermodynamic plasma structure of the chromosphere and
transition region.
Title: Geometrical Aspects of SOC Flare Models
Authors: McIntosh, S. W.; Charbonneau, P.
Bibcode: 2001AGUSM..SP52B04M
Altcode:
In this paper we address the geometrical properties of SOC Flare Models
and possible connections to high spatial resolution observations of the
solar coronal plasma. We discuss the study of geometrical projection
effects and the fractal nature of avalanches in large two and three
dimensional Cartesian lattice models and of (nano-)flares observed by
the TRACE spacecraft. We examine the differences, and similarities,
between the behavior of the lattice model and the observational data.
Title: Analysis of an avalanche model in the continuum limit
Authors: Liu, H.; Charbonneau, P.; Bogdan, T. J.; Pouquet, A.;
McIntosh, S. W.; Norman, J. P.
Bibcode: 2001AGUSM..SP51C03L
Altcode:
It is shown that in the continuum limit, the avalanche system postulated
by Lu and Hamilton (1991) (LH91) can be described by a hyper-diffusion
equation in regions where every lattice is in avalanche, and the
overall system can be approximated by a randomly forced system with
a anomalous hyper-diffusion term and a cubic nonlinear transport
term. The LH91 is equivalent to a finite difference approximation to
the the equation with 2nd order center differencing in space and simple
forward time integration, and is numerically unstable. The modified rule
by Lu et al. (1993) (LH93) actually overcame the numerical stability
problem by essentially reducing the diffusion coefficient. We apply a
dynamical renormalization group analysis to the continuum system. The
frequency power spectrum scaling behavior of the "dissipating energy"
and "falling-off energy" derived from this analysis is in reasonable
agreement with the results from the LH93 avalanche model.
Title: An Observational Manifestation of Magnetoatmospheric Waves
in Internetwork Regions of the Chromosphere and Transition Region
Authors: McIntosh, S. W.; Bogdan, T. J.; Cally, P. S.; Carlsson, M.;
Hansteen, V. H.; Judge, P. G.; Lites, B. W.; Peter, H.; Rosenthal,
C. S.; Tarbell, T. D.
Bibcode: 2001ApJ...548L.237M
Altcode:
We discuss an observational signature of magnetoatmospheric waves in
the chromosphere and transition region away from network magnetic
fields. We demonstrate that when the observed quantity, line or
continuum emission, is formed under high-β conditions, where β is
the ratio of the plasma and magnetic pressures, we see fluctuations in
intensity and line-of-sight (LOS) Doppler velocity consistent with the
passage of the magnetoatmospheric waves. Conversely, if the observations
form under low-β conditions, the intensity fluctuation is suppressed,
but we retain the LOS Doppler velocity fluctuations. We speculate that
mode conversion in the β~1 region is responsible for this change in
the observational manifestation of the magnetoatmospheric waves.
Title: Waves in the Magnetised Solar Atmosphere
Authors: Rosenthal, C. S.; Carlsson, M.; Hansteen, V.; McMurry,
A.; Bogdan, T. J.; McIntosh, S.; Nordlund, A.; Stein, R. F.; Dorch,
S. B. F.
Bibcode: 2001IAUS..203..170R
Altcode:
We have simulated the propagation of magneto-acoustic disturbances
through various magneto-hydrostatic structures constructed to mimic
the solar magnetic field. As waves propagate from regions of strong
to weak magnetic field and vice-versa different types of wave modes
(transverse and longitudinal) are coupled. In closed-field geometries
we see the trapping of wave energy within loop-like structures. In
open-field regions we see wave energy preferentially focussed away
from strong-field regions. We discuss these oscillations in terms
of various wave processes seen on the Sun - umbral oscillations,
penumbral running waves, internetwork oscillations etc.
Title: Very High Q Measurements on a Fused Silica Monolithic Pendulum
for Use in Enhanced Gravity Wave Detectors
Authors: Cagnoli, G.; Gammaitoni, L.; Hough, J.; Kovalik, J.; McIntosh,
S.; Punturo, M.; Rowan, S.
Bibcode: 2000PhRvL..85.2442C
Altcode:
We present for the first time the results of very high Q factor
measurements for a 2.8 kg fused silica mass suspended by two
fused quartz fibers attached by a novel technique for joining
fused silica or quartz. The Q for the pendulum mode at 0.93 Hz was
\(2.3+/-0.2\)×107, the highest value demonstrated to date
for a mass of this size. By employing such a new suspension system
the sensitivity of the gravitational wave detectors currently under
construction can be increased up to 1 order of magnitude.
Title: Suspension design for GEO 600-an update
Authors: Robertson, N. A.; Cagnoli, G.; Hough, J.; Husman, M. E.;
McIntosh, S.; Palmer, D.; Plissi, M. V.; Robertson, D. I.; Rowan,
S.; Sneddon, P.; Strain, K. A.; Torrie, C. I.; Ward, H.
Bibcode: 2000AIPC..523..313R
Altcode: 2000grwa.conf..313R
The GEO 600 gravitational wave detector (1) is currently under
construction at Ruthe, near Hannover in Germany. The design of the
suspension system for the main mirrors in the detector has been chosen
such that thermal noise due to the internal modes of the mirrors is
expected to set the sensitivity limit from 50 Hz to ~200 Hz. Thus the
design must be such that the effects of seismic noise and thermal
noise from the suspensions are lower than the ``internal'' thermal
noise at and above 50 Hz. To achieve this, a triple pendulum suspension
incorporating fused silica fibers in the lowest stage forms the major
part of the overall suspension and isolation system. In this paper,
recent work on developing several aspects of the triple pendulum design
is discussed. .
Title: Quiet Sun Oscillation Packets
Authors: Ireland, J.; McIntosh, S. W.; Fleck, B.
Bibcode: 2000SPD....31.0132I
Altcode: 2000BAAS...32..807I
This paper combines the novel techniques of wavelet analysis
and genetic algorithms to exploit SOHO-SUMER (Solar Ultraviolet
Measurements of Emitted Radiation) data in a new way. The data consists
of time series in O I 1306.03 Angstroms, Si II 1309.28 Angstroms,
C I 1311.36 Angstroms, C II 1334.53 Angstroms, He I 584 Angstroms,
O I 1152 Angstroms, and C III 1176 Angstroms tracking specific pieces
of quiet Sun westward across the disk. To analyse this data, genetic
algorithms (McIntosh et. al, A.& A. Suppl. Ser., 132, 145, 1998)
are used to fit quiet Sun emission spectra, allowing the unbiassed
determination of spectral properties such as total line intensity
and Doppler velocity. Time series of line intensity and Doppler
velocity are formed which are then analysed using wavelet techniques,
permitting the distinguishing of distinct oscillation wave packets in
the time series. Correlations of wave packets between different lines
and physical quantities are discussed, as are the distributions of
oscillation packets seen.
Title: On the Inference of Differential Emission Measures Using
Diagnostic Line Ratios
Authors: McIntosh, Scott W.
Bibcode: 2000ApJ...533.1043M
Altcode:
Spectroscopic diagnosis of hot optically thin plasmas can be used to
infer valuable information about the temperature structure of the
emitting plasma volume, through the emission measure differential
(DEM) in Te, DEM(Te). However, the uncertainties
in atomic parameters (required to model the plasma emission) make
such inferences intractable. We demonstrate that it is possible,
and relatively straightforward, to implement a formalism and infer
DEM(Te) in a way such that atomic uncertainties are treated
explicitly. Indeed, we show that a hybrid line-ratio/emission-measure
method is robust when ``standard'' inversion methods will fail to
produce consistent results.
Title: Preconditioning the Differential Emission Measure
(Te) Inverse Problem
Authors: McIntosh, S. W.; Charbonneau, P.; Brown, J. C.
Bibcode: 2000ApJ...529.1115M
Altcode:
In an inverse problem of any kind, poor conditioning of the inverse
operator decreases the numerical stability of any unregularized
solution in the presence of data noise. In this paper we show that
the numerical stability of the differential emission measure (DEM)
inverse problem can be considerably improved by judicious choice of
the integral operator. Specifically, we formulate a combinatorial
optimization problem where, in a preconditioning step, a subset of
spectral lines is selected in such a way as to minimize explicitly the
condition number of the discretized integral operator. We tackle this
large combinatorial optimization problem using a genetic algorithm. We
apply this preconditioning technique to a synthetic data set comprising
of solar UV/EUV emission lines in the SOHO SUMER/CDS wavelength
range. Following which we test the same hypothesis on lines observed by
the Harvard S-055 EUV spectroheliometer. On performing the inversion
we see that the temperature distribution in the emitting region of
the solar atmosphere is recovered with considerably better stability
and smaller error bars when our preconditioning technique is used,
in both synthetic and ``real'' cases, even though this involves
the analysis of fewer spectral lines than in the ``All-lines''
approach. The preconditioning step leads to regularized inversions
that compare favorably to inversions by singular value decomposition,
while providing greater flexibility in the incorporation of physically
and/or observationally based constraints in the line selection process.
Title: The GEO 600 Gravitational Wave Detector
Authors: Willke, B.; Aufmuth, P.; Balasubramanian, R.; Brozek, O. S.;
Cagnoli, G.; Casey, M.; Clubley, D.; Churches, D.; Danzmann, K.;
Fallnich, C.; Freise, A.; Goßler, S.; Grado, A.; Grote, H.; Hough,
J.; Husman, M.; Kawabe, K.; Lück, H.; McNamara, P.; McIntosh, S.;
Mossavi, K.; Newton, G. P.; Palmer, D.; Papa, M. A.; Plissi, M. V.;
Quetschke, V.; Robertson, D. I.; Robertson, N. A.; Rowan, S.; Rüdiger,
A.; Sathyaprakash, B. S.; Schilling, R.; Schutz, B. F.; Sintes-Olives,
A.; Skeldon, K. D.; Sneddon, P.; Strain, K. A.; Taylor, I.; Torrie,
C. I.; Vecchio, A.; Ward, H.; Welling, H.; Winkler, W.; Zawischa,
I.; Zhao, C.
Bibcode: 2000gwd..conf...25W
Altcode:
No abstract at ADS
Title: Aspects of the Suspension and Isolation Systems for the Test
Masses in GEO 600
Authors: Hough, J.; Cagnoli, G.; Husman, M.; McIntosh, S.; Plissi,
M.; Robertson, D.; Robertson, N.; Strain, K.; Torrie, C.; Ward, H.;
Rowan, S.
Bibcode: 2000gwd..conf..311H
Altcode:
No abstract at ADS
Title: Fused Silica Suspensions for Advanced Gravitational Wave
Detectors
Authors: Rowan, S.; Cagnoli, G.; McIntosh, S.; Sneddon, P.; Crookes,
D.; Hough, J.; Gustafson, E. K.; Route, R.; Fejer, M. M.
Bibcode: 2000gwd..conf..203R
Altcode:
No abstract at ADS
Title: Non-Uniqueness of Atmospheric Modeling
Authors: Judge, Philip G.; McIntosh, Scott W.
Bibcode: 1999SoPh..190..331J
Altcode:
We focus on the deceptively simple question: how can we use the emitted
photons to extract meaningful information on the transition region and
corona? Using examples, we conclude that the only safe way to proceed
is through forward models. In this way, inherent non-uniqueness is
handled by adding information through explicit physical assumptions
and restrictions made in the modeling procedure. The alternative,
`inverse' approaches, including (as a restricted subset) many standard
'`spectral diagnostic techniques', rely on more subjective choices
that have, as yet, no clear theoretical support. Emphasis is on the
solar transition region, but necessarily discussing the corona, and
with implications for more general problems concerning the use of
photons to diagnose plasma conditions.
Title: A non-uniqueness problem in solar hard x-ray spectroscopy
Authors: Piana, M.; Barrett, R.; Brown, J. C.; McIntosh, S. W.
Bibcode: 1999InvPr..15.1469P
Altcode:
We consider the hard x-ray emission process by interaction between
the electrons and the ions in the solar atmosphere. We provide the
integral equations describing this process as an inverse problem
in the case of uniform ionization of the plasma and of a simple but
rather realistic approximation of non-uniform conditions. The singular
system of the integral operators is computed analytically in the
continuous case for the uniform ionization model and numerically in
the case of discrete data for both uniform and non-uniform ionization
conditions. By analytical arguments and analysis of the singular
spectrum we point out that non-uniform ionization results in an
ambiguous interpretation of the solution of the integral equation,
this solution not being unique. Finally, we briefly recall that this
analysis facilitates methods for recovering unique and regularized
solutions from high-resolution hard x-ray spectral data soon to be
forthcoming from the HESSI space mission.
Title: Studying Solar MHD Wave Propagation in Two Dimensions
Authors: McIntosh, S. W.; Bogdan, T. J.
Bibcode: 1999AAS...194.7810M
Altcode: 1999BAAS...31..962M
We present preliminary results on simulations of Magnetohydrodynamic
(MHD) wave propagation in a two dimensional stratified model of the
upper solar atmosphere. The simulations presented are obtained using
the High-Order Godunov scheme of Zachary, Malagoli & Colella
(1994). These simulations allow us to analyze quantitatively the
coupling, resonances and absorption of MHD waves in a stratified
plasma such as that of the Sun. In particular, we are able to observe
the dynamic evolution of energy and momentum balances of the model
atmosphere in response the wave propagation. In addition, we are able to
study the phenomenology of MHD wave passage through particular regions
of interest. We will concentrate mostly upon the physical manifestation
of MHD waves propagating in ``network'' and ``internetwork'' regions and
study the effect on physical parameters and the basic field structure
imposed at outset. We believe that such simulations are important
in that they compliment the high quality/temporal resolution data
currently being acquired by the SOHO and TRACE spacecraft.
Title: Preconditioning the DEM(T) inverse problem
Authors: Charbonneau, P.; McIntosh, S.
Bibcode: 1999AAS...194.9313C
Altcode: 1999BAAS...31..990C
In an inverse problem of any kind, poor conditioning of the inverse
operator decreases the numerical stability of any unregularized solution
in the presence of data noise. In this poster we show that the numerical
stability of the differential emission measure (DEM) inverse problem
can be considreably improved by judicious choice of the integral
operator. Specifically, we formulate a combinatorial optimization
problem where, in a preconditioning step, a subset of spectral
lines is selected in order to minimize the condition number of the
discretized integral operator. This turns out to be a hard combinatorial
optimization problem, which we tackle using a genetic algorithm. We
apply the technique to the dataset comprising the solar UV/EUV emission
lines in the SOHO SUMER/CDS wavelength range, and to the Harvard S-055
EUV spectroheliometer data. The temperature distribution in the emitting
region of the solar atmosphere is recovered with considerably better
stability and smaller error bars when our preconditioning technique is
used, even though this involves the analysis of fewer spectral lines
than in the conventional ``all-lines'' approach.
Title: Spectral decomposition by genetic forward modelling
Authors: McIntosh, S. W.; Diver, D. A.; Judge, P. G.; Charbonneau,
P.; Ireland, J.; Brown, J. C.
Bibcode: 1998A&AS..132..145M
Altcode:
We discuss the analysis of real and simulated line spectra using
a genetic forward modelling technique. We show that this Genetic
Algorithm (GA) based technique experiences none of the user bias
or systematic problems that arise when faced with poorly sampled or
noisy data. An important feature of this technique is the ease with
which rigid a priori constraints can be applied to the data. These
constraints make the GA decomposition much more accurate and stable,
especially at the limit of instrumental resolution, than decomposition
algorithms commonly in use.
Title: Inversion of Thick Target Bremsstrahlung Spectra from
Nonuniformly Ionised Plasmas
Authors: Brown, John C.; McArthur, Guillian K.; Barrett, Richard K.;
McIntosh, Scott W.; Emslie, A. Gordon
Bibcode: 1998SoPh..179..379B
Altcode:
The effects of non-uniform plasma target ionisation on the spectrum of
thick-target HXR bremsstrahlung from a non-thermal electron beam are
analysed. In particular the effect of the target ionisation structure on
beam collisional energy losses, and hence on inversion of an observed
photon spectrum to yield the electron injection spectrum, is considered
and results compared with those obtained under the usual assumption
of a fully ionised target.
Title: The relation between line ratio and emission measure analyses
Authors: McIntosh, S. W.; Brown, J. C.; Judge, P. G.
Bibcode: 1998A&A...333..333M
Altcode:
Spectroscopic diagnosis of the temperature and density structure of
hot optically thin plasmas from emission line intensities is usually
described in two ways. The simplest approach, the `line ratio' method,
uses an observed ratio of emission line intensities to determine a
`spectroscopic mean' value of electron temperature < T_e >
or electron density < ne>. The mean value is chosen
to be the theoretical value of T_e or ne which matches the
observed value. The line ratio method is stable, leading to well defined
values of < T_e > or < n_e > for each line pair but, in the
realistic case of inhomogeneous plasmas, these are hard to interpret
since each line pair yields different mean parameter values. The more
general `differential emission measure' (DEM) method recognizes that
observed plasmas are better described by distributions of temperature
or density along the line of sight, and poses the problem in inverse
form. It is well known that the DEM function is the solution to the
inverse problem, which is a function of T_e, n_e, or both. Derivation of
DEM functions, while more generally applicable, is unstable to noise
and errors in spectral and atomic data. The mathematical relation
between these two approaches has never been precisely defined. In
this paper we demonstrate the formal equivalence of the approaches,
and discuss some potentially important applications of methods based
upon combining the line ratio and DEM approaches.