Author name code: deluca
ADS astronomy entries on 2022-09-14
author:DeLuca, Edward E.
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Title: The Airborne Infrared Spectrometer: Development,
Characterization, and the 2017 August 21 Eclipse Observation
Authors: Samra, Jenna E.; Marquez, Vanessa; Cheimets, Peter; DeLuca,
Edward E.; Golub, Leon; Hannigan, James W.; Madsen, Chad A.; Vira,
Alisha; Adams, Arn
Bibcode: 2022AJ....164...39S
Altcode: 2021arXiv210509419S
On 2017 August 21, the Airborne Infrared Spectrometer (AIR-Spec)
observed the total solar eclipse at an altitude of 14 km from aboard the
NSF/NCAR Gulfstream V research aircraft. The instrument successfully
observed the five coronal emission lines that it was designed to
measure: Si X 1.431 μm, S XI 1.921 μm, Fe IX 2.853 μm, Mg VIII
3.028 μm, and Si IX 3.935 μm. Characterizing these magnetically
sensitive emission lines is an important first step in designing
future instruments to monitor the coronal magnetic field, which
drives space weather events, as well as coronal heating, structure,
and dynamics. The AIR-Spec instrument includes an image stabilization
system, feed telescope, grating spectrometer, and slit-jaw imager. This
paper details the instrument design, optical alignment method, image
processing, and data calibration approach. The eclipse observations
are described and the available data are summarized.
Title: New Observations of the IR Emission Corona from the 2019 July
2 Eclipse Flight of the Airborne Infrared Spectrometer
Authors: Samra, Jenna E.; Madsen, Chad A.; Cheimets, Peter; DeLuca,
Edward E.; Golub, Leon; Marquez, Vanessa; Reyes, Naylynn Tañón
Bibcode: 2022ApJ...933...82S
Altcode: 2021arXiv210608760S
The Airborne Infrared Spectrometer (AIR-Spec) was commissioned during
the 2017 total solar eclipse, when it observed five infrared coronal
emission lines from a Gulfstream V research jet owned by the National
Science Foundation and operated by the National Center for Atmospheric
Research. The second AIR-Spec research flight took place during the
2019 July 2 total solar eclipse across the south Pacific. The 2019
eclipse flight resulted in seven minutes of observations, during
which the instrument measured all four of its target emission lines:
S XI 1.393 μm, Si X 1.431 μm, S XI 1.921 μm, and Fe IX 2.853
μm. The 1.393 μm S XI line was detected for the first time, and
probable first detections were made of Si XI 1.934 μm and Fe X 1.947
μm. The 2017 AIR-Spec detection of Fe IX was confirmed and the first
observations were made of the Fe IX line intensity as a function of
solar radius. Telluric absorption features were used to calibrate the
wavelength mapping, instrumental broadening, and throughput of the
instrument. AIR-Spec underwent significant upgrades in preparation for
the 2019 eclipse observation. The thermal background was reduced by a
factor of 30, providing a 5.5× improvement in signal-to-noise ratio,
and the postprocessed pointing stability was improved by a factor of 5
to <10″ rms. In addition, two imaging artifacts were identified
and resolved, improving the spectral resolution and making the 2019
data easier to interpret.
Title: Probing the Physics of the Solar Atmosphere with the Multi-slit
Solar Explorer (MUSE). II. Flares and Eruptions
Authors: Cheung, Mark C. M.; Martínez-Sykora, Juan; Testa, Paola;
De Pontieu, Bart; Chintzoglou, Georgios; Rempel, Matthias; Polito,
Vanessa; Kerr, Graham S.; Reeves, Katharine K.; Fletcher, Lyndsay; Jin,
Meng; Nóbrega-Siverio, Daniel; Danilovic, Sanja; Antolin, Patrick;
Allred, Joel; Hansteen, Viggo; Ugarte-Urra, Ignacio; DeLuca, Edward;
Longcope, Dana; Takasao, Shinsuke; DeRosa, Marc L.; Boerner, Paul;
Jaeggli, Sarah; Nitta, Nariaki V.; Daw, Adrian; Carlsson, Mats; Golub,
Leon; The
Bibcode: 2022ApJ...926...53C
Altcode: 2021arXiv210615591C
Current state-of-the-art spectrographs cannot resolve the fundamental
spatial (subarcseconds) and temporal (less than a few tens of
seconds) scales of the coronal dynamics of solar flares and eruptive
phenomena. The highest-resolution coronal data to date are based on
imaging, which is blind to many of the processes that drive coronal
energetics and dynamics. As shown by the Interface Region Imaging
Spectrograph for the low solar atmosphere, we need high-resolution
spectroscopic measurements with simultaneous imaging to understand the
dominant processes. In this paper: (1) we introduce the Multi-slit Solar
Explorer (MUSE), a spaceborne observatory to fill this observational
gap by providing high-cadence (<20 s), subarcsecond-resolution
spectroscopic rasters over an active region size of the solar transition
region and corona; (2) using advanced numerical models, we demonstrate
the unique diagnostic capabilities of MUSE for exploring solar coronal
dynamics and for constraining and discriminating models of solar flares
and eruptions; (3) we discuss the key contributions MUSE would make
in addressing the science objectives of the Next Generation Solar
Physics Mission (NGSPM), and how MUSE, the high-throughput Extreme
Ultraviolet Solar Telescope, and the Daniel K Inouye Solar Telescope
(and other ground-based observatories) can operate as a distributed
implementation of the NGSPM. This is a companion paper to De Pontieu
et al., which focuses on investigating coronal heating with MUSE.
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: Probing the Physics of the Solar Atmosphere with the Multi-slit
Solar Explorer (MUSE): II. Flares and Eruptions
Authors: Cheung, Chun Ming Mark; Martinez-Sykora, Juan; Testa, Paola;
De Pontieu, Bart; Chintzoglou, Georgios; Rempel, Matthias; Polito,
Vanessa; Kerr, Graham; Reeves, Katharine; Fletcher, Lyndsay; Jin,
Meng; Nobrega, Daniel; Danilovic, Sanja; Antolin, Patrick; Allred,
Joel; Hansteen, Viggo; Ugarte-Urra, Ignacio; DeLuca, Edward; Longcope,
Dana; Takasao, Shinsuke; DeRosa, Marc; Boerner, Paul; Jaeggli, Sarah;
Nitta, Nariaki; Daw, Adrian; Carlsson, Mats; Golub, Leon
Bibcode: 2021AGUFMSH51A..08C
Altcode:
Current state-of-the-art spectrographs cannot resolve the fundamental
spatial (sub-arcseconds) and temporal scales (less than a few tens
of seconds) of the coronal dynamics of solar flares and eruptive
phenomena. The highest resolution coronal data to date are based on
imaging, which is blind to many of the processes that drive coronal
energetics and dynamics. As shown by IRIS for the low solar atmosphere,
we need high-resolution spectroscopic measurements with simultaneous
imaging to understand the dominant processes. In this paper: (1)
we introduce the Multi-slit Solar Explorer (MUSE), a spaceborne
observatory to fill this observational gap by providing high-cadence
(<20 s), sub-arcsecond resolution spectroscopic rasters over an
active region size of the solar transition region and corona; (2)
using advanced numerical models, we demonstrate the unique diagnostic
capabilities of MUSE for exploring solar coronal dynamics, and for
constraining and discriminating models of solar flares and eruptions;
(3) we discuss the key contributions MUSE would make in addressing the
science objectives of the Next Generation Solar Physics Mission (NGSPM),
and how MUSE, the high-throughput EUV Solar Telescope (EUVST) and the
Daniel K Inouye Solar Telescope (and other ground-based observatories)
can operate as a distributed implementation of the NGSPM. This is a
companion paper to De Pontieu et al. (2021, also submitted to SH-17),
which focuses on investigating coronal heating with MUSE.
Title: The Multiview Observatory for Solar Terrestrial Science (MOST)
Authors: Gopalswamy, Nat; Kucera, Therese; Leake, James; MacDowall,
Robert; Wilson, Lynn; Kanekal, Shrikanth; Shih, Albert; Christe,
Steven; Gong, Qian; Viall, Nicholeen; Tadikonda, Sivakumar; Fung,
Shing; Yashiro, Seiji; Makela, Pertti; Golub, Leon; DeLuca, Edward;
Reeves, Katharine; Seaton, Daniel; Savage, Sabrina; Winebarger, Amy;
DeForest, Craig; Desai, Mihir; Bastian, Tim; Lazio, Joseph; Jensen,
P. E., C. S. P., Elizabeth; Manchester, Ward; Wood, Brian; Kooi,
Jason; Wexler, David; Bale, Stuart; Krucker, Sam; Hurlburt, Neal;
DeRosa, Marc; Pevtsov, Alexei; Tripathy, Sushanta; Jain, Kiran;
Gosain, Sanjay; Petrie, Gordon; Kholikov, Shukirjon; Zhao, Junwei;
Scherrer, Philip; Woods, Thomas; Chamberlin, Philip; Kenny, Megan
Bibcode: 2021AGUFMSH12A..07G
Altcode:
The Multiview Observatory for Solar Terrestrial Science (MOST) is a
comprehensive mission concept targeting the magnetic coupling between
the solar interior and the heliosphere. The wide-ranging imagery and
time series data from MOST will help understand the solar drivers and
the heliospheric responses as a system, discerning and tracking 3D
magnetic field structures, both transient and quiescent in the inner
heliosphere. MOST will have seven remote-sensing and three in-situ
instruments: (1) Magnetic and Doppler Imager (MaDI) to investigate
surface and subsurface magnetism by exploiting the combination of
helioseismic and magnetic-field measurements in the photosphere; (2)
Inner Coronal Imager in EUV (ICIE) to study large-scale structures
such as active regions, coronal holes and eruptive structures by
capturing the magnetic connection between the photosphere and the
corona to about 3 solar radii; (3) Hard X-ray Imager (HXI) to image
the non-thermal flare structure; (4) White-light Coronagraph (WCOR) to
seamlessly study transient and quiescent large-scale coronal structures
extending from the ICIE field of view (FOV); (5) Faraday Effect
Tracker of Coronal and Heliospheric structures (FETCH), a novel radio
package to determine the magnetic field structure and plasma column
density, and their evolution within 0.5 au; (6) Heliospheric Imager
with Polarization (HIP) to track solar features beyond the WCOR FOV,
study their impact on Earth, and provide important context for FETCH;
(7) Radio and Plasma Wave instrument (M/WAVES) to study electron beams
and shocks propagating into the heliosphere via passive radio emission;
(8) Solar High-energy Ion Velocity Analyzer (SHIVA) to determine spectra
of electrons, and ions from H to Fe at multiple spatial locations
and use energetic particles as tracers of magnetic connectivity; (9)
Solar Wind Magnetometer (MAG) to characterize magnetic structures at
1 au; (10) Solar Wind Plasma Instrument (SWPI) to characterize plasma
structures at 1 au. MOST will have two large spacecraft with identical
payloads deployed at L4 and L5 and two smaller spacecraft ahead of L4
and behind L5 to carry additional FETCH elements. MOST will build upon
SOHO and STEREO achievements to expand the multiview observational
approach into the first half of the 21st Century.
Title: Preliminary Results from the Marshall Grazing Incidence X-ray
Spectrometer (MaGIXS)
Authors: Winebarger, Amy; Savage, Sabrina; Kobayashi, Ken; Champey,
Patrick; Golub, Leon; Walsh, Robert; Athiray, P. S.; Bradshaw, Stephen;
Cheimets, Peter; Cirtain, Jonathan; DeLuca, Edward; Del Zanna, Giulio;
Mason, Helen; McKenzie, David; Ramsey, Brian; Reeves, Katharine;
Testa, Paola; Vigil, Genevieve; Warren, Harry
Bibcode: 2021AGUFMSH51A..06W
Altcode:
Coronal heating mechanisms are notoriously difficult to constrain with
current observations. We present new observations from an instrument
designed to measure a critical diagnostic of the frequency heating
events in active regions. The Marshall Grazing Incidence X-ray
Spectrometer (MaGIXS) is a sounding rocket mission that aims to
observe the soft x-ray solar spectrum (0.6 2.5 nm) with both spatial
and spectral resolution. This wavelength range has several high
temperature and abundance diagnostics that can be used to infer the
coronal heating frequency. MaGIXS will observe the Sun through a 12
x 33 slot, producing ``overlappograms, where the spatial and spectral
information are overlapped and must be unfolded. In this presentation,
I will report on the MaGIXS launch and data collection and provide
preliminary analysis of MaGIXS observations.
Title: Exploring the middle corona: new instrumentation to address
science questions critical to understanding the thermal structure
and dynamic evolution of the middle corona
Authors: DeLuca, Edward; Winebarger, Amy; Reeves, Katharine; Golub,
Leon; Samra, Jenna; Madsen, Chad; Rivera, Yeimy; Karna, Nishu;
Savage, Sabrina; Seaton, Daniel; West, Matthew; Downs, Cooper; Del
Zanna, Giulio
Bibcode: 2021AGUFMSH25F2150D
Altcode:
The global structure of the largely unexplored middle corona determines
the physical properties of the inner heliosphere, affects the formation
and acceleration of the solar wind, and controls the dynamics of
eruptive events. Tracing the short and long term global evolution
of the extended corona, identifying changes in corona/heliosphere
connectivity and following the dynamic evolution of eruptive events
in this unexplored region will provide observational data that will
clarify how the corona transitions from closed to open, illuminate the
genesis of coronal mass ejections, and provide input for the design
of the next generation of physics based space weather forecasts. This
poster outlines several critical science questions and identifies the
measurements that are required to make substantial progress towards
addressing the questions. We review and discuss the instrumentation
necessary to capture the observations needed for meaningful progress
in this area as well as the role of simulations in the interpretation
of the observations.
Title: Probing the Lower Solar Chromosphere Via Dynamical Signatures
of UV Bursts in Cold Lines
Authors: Chaparro, Victoria; Madsen, Chad; DeLuca, Edward
Bibcode: 2021AGUFMSH45B2368C
Altcode:
UV Bursts are small scale brightenings identified by dramatic
intensification and broadening of emission lines often accompanied
by absorption features from cold metallic ions. They can be used
as probes of plasma conditions in the lower solar atmosphere since
their spectral features suggest they are magnetic reconnection
events in the cool lower chromosphere. We present a spatial and
temporal analysis of the intensification and broadening of the Si IV
1393.78 Å and Cl I 1351.66 Å lines observed by the Interface Region
Imaging Spectrograph (IRIS) to trace magnetic reconnection outflows
through the lower chromosphere. We employ a semi-automated UV burst
detection algorithm by applying single-Gaussian fits (SGF) to the Si
IV 1394 Å line in IRIS sit-and-stare data. We first isolate the likely
candidate population in the SGF parameter space, reducing the candidate
field from hundreds of thousands to only a few thousand spectra. We
then manually search these candidate spectra for Ni II 1393.33 Å
absorption. Following detection, we focus on the Cl I 1391.66 Å
line to observe the influence of UV bursts over lower chromospheric
dynamics. This is done by constructing a series of space-time plots of
the peak intensity, Doppler velocity, and line width SGF parameters
of Cl I 1391.66 Å to measure time lags between its intensification
and broadening, allowing us to estimate downflow velocities in the
lower chromosphere under UV burst conditions. This is possible because
the peak intensity of Cl I 1391.66 Å is dependent on fluorescence
from C II 1335.71 Å, a line strongly emitted by the UV burst source,
while its width only broadens when the emitting material is impacted
by a material flow. This study establishes the power of UV bursts as
probes of dynamical phenomena in the lower chromosphere, a region that
is notoriously difficult to observe directly. Furthermore, it lays the
groundwork for future exploration of the often overlooked cool emission
lines in the IRIS spectral passbands and their potential as physical
diagnostics. This work is part of the NSF-REU Solar Physics program at
SAO, grant number AGS-1850750. Keywords: Solar Magnetic Reconnection,
Active Solar Chromosphere, Solar Ultraviolet Emission.
Title: An Airborne Coronal Emission Surveyor (ACES) for Total Solar
Eclipse Observations
Authors: Samra, Jenna; Cheimets, Peter; DeLuca, Edward; Madsen, Chad;
Marquez, Vanessa
Bibcode: 2021AGUFMED13B..01S
Altcode:
The Airborne Coronal Emission Surveyor (ACES) is a new imaging Fourier
transform spectrometer (FTS) that will explore the large-scale
coronal infrared (IR) emission spectrum during the April 8, 2024
total solar eclipse. ACES will fly along the path of totality on the
NSF/NCAR Gulfstream V High-performance Instrumented Airborne Platform
for Environmental Research (GV HIAPER), with a stabilized solar feed
provided by the Airborne Stabilized Platform for InfraRed Experiments
(ASPIRE). During the 6-minute total eclipse, ACES will map emission
line intensity in the 14 micron wavelength region at over a 0.73 0.5
field of view (FOV). A GV altitude of at least 13 km will enable it to
survey the near and mid-IR with minimal atmospheric interference. ACES
is the latest in a line of NSF-funded airborne instruments developed by
Smithsonian Astrophysical Observatory to explore the IR emission corona
from GV HIAPER. Previous instruments include the Airborne InfraRed
Spectrometer (AIR-Spec), a cryogenic grating spectrometer that observed
the 2017 and 2019 eclipses, and ASPIRE, which improves on the AIR-Spec
image stabilization system to provide a 20 cm solar feed stabilized to
5 arcsec RMS over 1 second. Unlike AIR-Spec, which observed a narrow
range of wavelengths and imaged along only one dimension, ACES will
survey the entire 14 micron (2,50010,000 cm-1) spectral range at high
(0.2 cm-1) spectral resolution and in two spatial dimensions. ACES is
expected to observe neutral helium as well as 18 forbidden lines of
ionized magnesium, silicon, sulfur, argon, calcium, and iron, and it
may measure weaker lines of those and other ions. The mission addresses
science questions related to the strength of different emission lines in
different regions of the corona, the relative radiative to collisional
excitation in each line, the best temperature and density diagnostics
in the passband, and the variation of elemental abundances across the
corona. The instrument consists of a condenser telescope, cryogenic
Michaelson interferometer, achromatic lens, and IR camera. The 2024
eclipse flight will serve as the ACES commissioning flight.
Title: Magnetofrictional Modeling of an Erupting Pseudostreamer
Authors: Karna, Nishu; Savcheva, Antonia; Gibson, Sarah; Tassev,
Svetlin; Reeves, Katharine K.; DeLuca, Edward E.; Dalmasse, Kévin
Bibcode: 2021ApJ...913...47K
Altcode:
In this study, we present the magnetic configuration of an erupting
pseudostreamer observed on 2015 April 19, on the southwest limb of the
Sun, with a prominence cavity embedded inside. The eruption resulted in
a partial halo coronal mass ejection. The prominence eruption begins
with a slow rise and then evolves to a fast-rise phase. We analyze
this erupting pseudostreamer using the flux-rope insertion method
and magnetofrictional relaxation to establish a sequence of plausible
out-of-equilibrium magnetic configurations. This approach allows the
direct incorporation of observations of structures seen in the corona
(filament and cavity) to appropriately model the pseudostreamer
based on SDO/HMI line-of-sight photospheric magnetograms. We also
perform a topological analysis in order to determine the location
of quasiseparatrix layers (QSLs) in the models, producing Q-maps to
examine how the QSL locations progress in the higher iterations. We
found that the axial flux in our best-fit unstable model was a factor
of 20 times higher than we found in our marginally stable case. We
computed the average magnetic field strength of the prominence and
found that the unstable model exhibits twice the average field strength
of the stable model. The eruption height from our modeling matches
very well with the prominence eruption height measured from the AIA
observation. The Q-maps derived from the model reproduce structures
observed in LASCO/C2. Thus, the modeling and topological analysis
results are fully consistent with the observed morphological features,
implying that we have captured the large magnetic structure of the
erupting filament in our magnetofrictional simulation.
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 Soft X-ray Irradiance Variability, I: Segmentation
of Hinode/XRT Full-Disk Images and Comparison with GOES (1 - 8 Å)
X-Ray Flux
Authors: Adithya, H. N.; Kariyappa, Rangaiah; Shinsuke, Imada; Kanya,
Kusano; Zender, Joe; Damé, Luc; Gabriel, Giono; DeLuca, Edward;
Weber, Mark
Bibcode: 2021SoPh..296...71A
Altcode:
It is of great interest and importance to study the variabilities of
solar EUV, UV and X-ray irradiance in heliophysics, in Earth's climate,
and space weather applications. A careful study is required to identify,
track, monitor and segment the different coronal features such as active
regions (ARs), coronal holes (CHs), the background regions (BGs) and
the X-ray bright points (XBPs) from spatially resolved full-disk images
of the Sun. Variability of solar soft X-ray irradiance is studied for a
period of 13 years (February 2007-March 2020, covers Solar Cycle 24),
using the X-Ray Telescope on board the Hinode (Hinode/XRT) and GOES
(1 - 8 Å). The full-disk X-ray images observed in Al_mesh filter
from XRT are used, for the first time, to understand the solar X-ray
irradiance variability measured, Sun as a star, by GOES instrument. An
algorithm in Python has been developed and applied to identify and
segment coronal X-ray features (ARs, CHs, BGs, and XBPs) from the
full-disk soft X-ray observations of Hinode/XRT. The segmentation
process has been carried out automatically based on the intensity
level, morphology and sizes of the X-ray features. The total intensity,
area, and contribution of ARs/CHs/BGs/XBPs features were estimated and
compared with the full-disk integrated intensity (FDI) and GOES (1 -
8 Å) X-ray irradiance measurements. The XBPs have been identified and
counted automatically over the full disk to investigate their relation
to solar magnetic cycle. The total intensity of ARs/CHs/BGs/XBPs/FD
regions are compared with the GOES (1 - 8 Å) X-ray irradiance
variations. We present the results obtained from Hinode/XRT full-disk
images (in Al_mesh filter) and compare the resulting integrated
full-disk intensity (FDI) with GOES X-ray irradiance. The X-ray
intensity measured over ARs/CHs/BGs/XBPs/FD is well correlated with
GOES X-ray flux. The contributions of the segmented X-ray features
to FDI and X-ray irradiance variations are determined. It is found
that the background and active regions have a greater impact on the
X-ray irradiance fluctuations. The mean contribution estimated for the
whole observed period of the background regions (BGs) will be around 65
±10.97 % , whereas the ARs, XBPs and CHs are 30 ±11.82 % , 4 ±1.18 %
and 1 ±0.52 % , respectively, to total solar X-ray flux. We observed
that the area and contribution of ARs and CHs varies with the phase of
the solar cycle, whereas the BGs and XBPs show an anti-correlation. We
find that the area of the coronal features is highly variable suggesting
that their area has to be taken into account in irradiance models,
in addition to their intensity variations. The time series results of
XBPs suggest for an existence of anti-correlation between the number
of XBPs and the sunspot numbers. It is also important to consider both
the number variation and the contribution of XBPs in the reconstruction
of total solar X-ray irradiance variability.
Title: A Study of Equatorial Coronal Holes and Active regions during
the Maximum Phase of four Solar Cycles
Authors: Karna, Nishu; DeLuca, Edward; Pesnell, William; Saar, Steven;
Karna, Mahendra
Bibcode: 2021cosp...43E.920K
Altcode:
The 11-year Solar Cycle (SC) is characterized by periodic changes
in solar activity indicators such as number of sunspots, coronal
holes, active regions (ARs), as well as the occurrence rate of solar
energetic events such as filament eruptions, flares and coronal mass
ejections (CMEs). In this work we performed a statistical study of the
equatorial coronal holes (ECHs) and ARs during the maximum phase of the
last four solar cycles: SC 21 (1979--1982), SC 22 (1989--1992), SC 23
(1999--2002) and SC 24 (2012--2015). We compared the number of ECHs and
ARs, separations between their centroids, solar wind speed, pressure
and the number of intense geomagnetic storms (IGS) data over these four
cycles. We note a strong anticorrelation between the number of ARs and
ECHs. We found that the number of close ARs and ECHs, solar wind speed,
and the number of IGS increases with average sunspot maximum number
for even cycles and decreases with average sunspot maximum for odd
cycles. These odd-even trends largely (though not entirely) disappear
in the relation between the wind properties and the numbers of close
AR and ECH. This suggests a possible link between ECH-AR interactions
and the solar wind phenomena, though residual odd-even trends point to
the importance of other effects (e.g., Sun-earth magnetic alignment)
as well.
Title: Magnetofrictional Modeling of an erupting Pseudostreamer
Authors: Karna, Nishu; Gibson, Sarah; DeLuca, Edward; Dalmasse,
Kévin; Savcheva, Antonia; Tassev, Svetlin
Bibcode: 2021cosp...43E1768K
Altcode:
In this study, we present a magnetic configuration of an erupting
pseudostreamer observed on April 19, 2015 on the Southwest limb,
embedding a prominence cavity. The eruption resulted in a relatively
wide CME with a round front and prominence core intersected by a sharp
plume as seen in SOHO/LASCO C2, a partial halo was observed. The
prominence eruption begins with a slow rise and then evolves to a
fast rise phase. We first construct a non-linear force free field
(NLFFF) model of this erupting pseudostreamer using the flux rope
insertion method. The NLFFF model produces the 3D coronal magnetic field
constrained by observed coronal structures and the SDO/HMI photospheric
magnetogram taken 3 days earlier. We then increase axial and poloidal
flux in the model to make it unstable. The field configurations
representing the eruption are not in force-free equilibrium. We
magnetofrictionally evolve the model until the flux rope expands to
three solar radii and compare the modeled CME propagation with the
SOHO/LASCO C2 observations. We perform a topological analysis of the
models in order to determine the location of quasi-separatrix layers
(QSLs) and how the QSL locations are transferred as the simulation
progresses. The model reproduced the LASCO C2 observation structure in
the QSL map. The modeling and topological analysis results are fully
consistent with the observed morphological features implying that we
have captured the large magnetic structure of the erupting filament.
Title: Characterization of UV Bursts Using Line-Ratio Density
Diagnostics
Authors: Conneely, F.; Madsen, C. A.; DeLuca, E.
Bibcode: 2020AGUFMSH0010005C
Altcode:
We compare abundance-sensitive and abundance-insensitive electron
density diagnostics for a large sample of UV burst spectra. These bursts
are compact (~1 arcsec), short-lived (~minutes to hours) active-region
phenomena, forming in the cool lower solar atmosphere and capable of
reaching nearly 100,000K. They exhibit significant intensification and
broadening/splitting of the Si IV 1393.76/1402.77 Å lines, which we
believe are signatures of magnetic reconnection. Bursts also display
absorption from cool metallic ions Ni II and Fe II, suggesting that they
form deep in the chromosphere. These unusual phenomena are critical to
understanding energy and mass transfer within the solar atmosphere,
possibly contributing to upper-chromospheric and coronal heating and
affecting the energetics and dynamics of the lower atmosphere. We
employ a semi-automated detection algorithm to assemble a sample of
over 9,800 UV burst spectra for Interface Region Imaging Spectrograph
(IRIS) observations of two active regions spanning several days. We perform line-ratio density diagnostics using O IV and S IV pairs as
well as a Si IV / O IV ratio. Since bursts are characterized by strong
Si IV 1402.77 Å emission and O IV 1401.16 Å also appears strongly in a
majority of burst spectra, the Si IV / O IV diagnostic has the potential
to be a robust density indicator. There is a significant uncertainty
around the use of different-species diagnostics due to their strong
dependence on relative atomic abundances, which are poorly constrained
in the chromosphere. We compare the Si IV / O IV diagnostic with the
abundance-insensitive ratios of O IV 1399.78 Å / O IV 1401.16 Å, O IV
1401.16 Å / O IV 1404.81 Å, and S IV 1404.85 Å / S IV 1406.06 Å and
comment on the viability of the Si IV /O IV method in burst regions. We
also find the rates of detection for these lines in our spectra. Our
density analysis provides useful constraints on UV burst formation
altitudes and aids in the comparison of observations to models. This work is supported by the NSF-REU Solar Physics program at SAO,
grant number AGS-1850750 and NASA H-SR grant number 80NSSC18K1124.
Title: Space Weather, Extreme Ultraviolet Instruments and the
Multithermal Corona
Authors: Golub, L.; DeLuca, E.; Reeves, K.
Bibcode: 2020AGUFMSH0300004G
Altcode:
Observation of the solar corona from Earth orbit or from other
locations such as L1 or L5 using suitably-chosen Extreme UltraViolet
(EUV) wavelengths offers the possibility of addressing two major goals
that will improve our ability to forecast and predict geoeffective space
weather events: 1.) improve our understanding of the coronal conditions
that control the opening and closing of the corona to the heliosphere
and consequent solar wind streams, and 2.) improve our understanding
of the physical processes that control the early evolution of CMEs
and the formation of shocks from the solar surface out to beyond the
nominal source surface. The time-varying solar corona is structured
not only in space and in time but also in temperature. A method
for efficiently observing multiple wavelengths, thereby recording
emission lines formed at different temperatures, simultaneously is
therefore desirable. These observations are especially necessary for CME
detection, as the departing magnetized plasma shows markedly different
structures at different temperatures and even the detectability of the
event varies dramatically at different EUV wavelengths. EUV measurements
can help to: i.) determine coronal structuring from its roots out
to beyond 2.5 R_s; ii.) measure the changes in coronal connectivity;
iii.) distinguish between and test solar wind models; iv.) establish
the impact of pre-existing coronal structures on CME evolution;
v.) confront theories of SEP acceleration and preconditioning; and
vi.) establish the extent of energy release behind CMEs.
Title: A Study of Equatorial Coronal Holes during the Maximum Phase
of Four Solar Cycles
Authors: Karna, Mahendra Lal; Karna, Nishu; Saar, Steven H.; Pesnell,
W. Dean; DeLuca, Edward E.
Bibcode: 2020ApJ...901..124K
Altcode:
The 11 yr solar cycle (SC) is characterized by periodic changes in
solar activity indicators such as the number of sunspots, coronal
holes, and active regions (ARs), as well as the occurrence rate of
solar energetic events such as filament eruptions, flares, and coronal
mass ejections. In this work we performed a statistical study of the
equatorial coronal holes (ECHs) and ARs during the maximum phase
of the last four SCs: SC 21 (1979-1982), SC 22 (1989-1992), SC 23
(1999-2002), and SC 24 (2012-2015). We compared the number of ECHs and
ARs, separations between their centroids, solar wind speed, pressure,
and the number of intense geomagnetic storm (IGS) data over these four
cycles. We note a strong anticorrelation between the number of ARs and
ECHs. We found that the number of close ARs and ECHs, solar wind speed,
and the number of IGS increases with average sunspot maximum number
for even cycles and decreases with average sunspot maximum for odd
cycles. Also, we find strong odd-even trends in the relation between
the wind properties and the numbers of close AR and ECH. These results
obtained from the annual average data suggest a possible link between
ECH and AR proximity and the solar wind phenomena, though odd-even
trends point to the importance of other effects (e.g., Sun-Earth
magnetic alignment) as well.
Title: Major Scientific Challenges and Opportunities in Understanding
Magnetic Reconnection and Related Explosive Phenomena in Solar and
Heliospheric Plasmas
Authors: Ji, H.; Karpen, J.; Alt, A.; Antiochos, S.; Baalrud, S.;
Bale, S.; Bellan, P. M.; Begelman, M.; Beresnyak, A.; Bhattacharjee,
A.; Blackman, E. G.; Brennan, D.; Brown, M.; Buechner, J.; Burch, J.;
Cassak, P.; Chen, B.; Chen, L. -J.; Chen, Y.; Chien, A.; Comisso,
L.; Craig, D.; Dahlin, J.; Daughton, W.; DeLuca, E.; Dong, C. F.;
Dorfman, S.; Drake, J.; Ebrahimi, F.; Egedal, J.; Ergun, R.; Eyink,
G.; Fan, Y.; Fiksel, G.; Forest, C.; Fox, W.; Froula, D.; Fujimoto,
K.; Gao, L.; Genestreti, K.; Gibson, S.; Goldstein, M.; Guo, F.; Hare,
J.; Hesse, M.; Hoshino, M.; Hu, Q.; Huang, Y. -M.; Jara-Almonte, J.;
Karimabadi, H.; Klimchuk, J.; Kunz, M.; Kusano, K.; Lazarian, A.; Le,
A.; Lebedev, S.; Li, H.; Li, X.; Lin, Y.; Linton, M.; Liu, Y. -H.;
Liu, W.; Longcope, D.; Loureiro, N.; Lu, Q. -M.; Ma, Z-W.; Matthaeus,
W. H.; Meyerhofer, D.; Mozer, F.; Munsat, T.; Murphy, N. A.; Nilson,
P.; Ono, Y.; Opher, M.; Park, H.; Parker, S.; Petropoulou, M.; Phan,
T.; Prager, S.; Rempel, M.; Ren, C.; Ren, Y.; Rosner, R.; Roytershteyn,
V.; Sarff, J.; Savcheva, A.; Schaffner, D.; Schoeffier, K.; Scime, E.;
Shay, M.; Sironi, L.; Sitnov, M.; Stanier, A.; Swisdak, M.; TenBarge,
J.; Tharp, T.; Uzdensky, D.; Vaivads, A.; Velli, M.; Vishniac, E.;
Wang, H.; Werner, G.; Xiao, C.; Yamada, M.; Yokoyama, T.; Yoo, J.;
Zenitani, S.; Zweibel, E.
Bibcode: 2020arXiv200908779J
Altcode:
Magnetic reconnection underlies many explosive phenomena in the
heliosphere and in laboratory plasmas. The new research capabilities in
theory/simulations, observations, and laboratory experiments provide the
opportunity to solve the grand scientific challenges summarized in this
whitepaper. Success will require enhanced and sustained investments
from relevant funding agencies, increased interagency/international
partnerships, and close collaborations of the solar, heliospheric,
and laboratory plasma communities. These investments will deliver
transformative progress in understanding magnetic reconnection and
related explosive phenomena including space weather events.
Title: A Study of Equatorial Coronal Holes during the Maximum Phase
of four Solar Cycles
Authors: Karna, N.; Karna, M.; Saar, S.; Pesnell, W.; DeLuca, E.
Bibcode: 2020SPD....5120903K
Altcode:
The 11-year Solar Cycle (SC) is characterized by periodic changes
in solar activity indicators such as a number of sunspots, coronal
holes, active regions (ARs), as well as the occurrence rate of solar
energetic events such as filament eruptions, flares and coronal mass
ejections (CMEs). In this work we performed a statistical study of
the equatorial coronal holes (ECHs) and ARs during the maximum phase
of the last four solar cycles: SC 21 (1979-1982), SC 22 (1989-1992),
SC 23 (1999-2002) and SC 24 (2012-2015). We compared the number of
ECHs and ARs, separations between their centroids, solar wind speed,
pressure and the number of intense geomagnetic storms (IGS) data
over these four cycles. We note a strong anticorrelation between the
number of ARs and ECHs. We found that the number of close ARs and ECHs
(which are potentially interacting), solar wind speed, and the number
of IGS increases with average sunspot maximum number for even cycles
and decreases with average sunspot maximum for odd cycles. Also,
we find strong odd-even trends in the relation between the wind
properties and the numbers of close AR and ECH. These results suggest a
possible link between ECH-AR interactions and the solar wind phenomena,
though odd-even trends point to the importance of other effects (e.g.,
Sun-earth magnetic alignment) as well.
Title: EUV imaging and spectroscopy for improved space weather
forecasting
Authors: Golub, Leon; Cheimets, Peter; DeLuca, Edward E.; Madsen, Chad
A.; Reeves, Katharine K.; Samra, Jenna; Savage, Sabrina; Winebarger,
Amy; Bruccoleri, Alexander R.
Bibcode: 2020JSWSC..10...37G
Altcode:
Accurate predictions of harmful space weather effects are mandatory
for the protection of astronauts and other assets in space, whether in
Earth or lunar orbit, in transit between solar system objects, or on the
surface of other planetary bodies. Because the corona is multithermal
(i.e., structured not only in space but also in temperature),
wavelength-separated data provide crucial information that is not
available to imaging methods that integrate over temperature. The
extreme ultraviolet (EUV) wavelengths enable us to focus directly on
high temperature coronal plasma associated with solar flares, coronal
mass ejections (CMEs), and shocked material without being overwhelmed by
intensity from the solar disk. Both wide-field imaging and spectroscopic
observations of the solar corona taken from a variety of orbits (e.g.,
Earth, L1, or L5) using suitably-chosen EUV instrumentation offer
the possibility of addressing two major goals to enhance our space
weather prediction capability, namely: (1) Improve our understanding
of the coronal conditions that control the opening and closing of the
corona to the heliosphere and consequent solar wind streams, and (2)
Improve our understanding of the physical processes that control the
early evolution of CMEs and the formation of shocks, from the solar
surface out into the extended corona.
Title: A New Facility for Airborne Solar Astronomy: NASA's WB-57 at
the 2017 Total Solar Eclipse
Authors: Caspi, Amir; Seaton, Daniel B.; Tsang, Constantine C. C.;
DeForest, Craig E.; Bryans, Paul; DeLuca, Edward E.; Tomczyk,
Steven; Burkepile, Joan T.; Casey, Thomas "Tony"; Collier, John;
Darrow, Donald "DD"; Del Rosso, Dominic; Durda, Daniel D.; Gallagher,
Peter T.; Golub, Leon; Jacyna, Matthew; Johnson, David "DJ"; Judge,
Philip G.; Klemm, Cary "Diddle"; Laurent, Glenn T.; Lewis, Johanna;
Mallini, Charles J.; Parent, Thomas "Duster"; Propp, Timothy; Steffl,
Andrew J.; Warner, Jeff; West, Matthew J.; Wiseman, John; Yates,
Mallory; Zhukov, Andrei N.; NASA WB-57 2017 Eclipse Observing Team
Bibcode: 2020ApJ...895..131C
Altcode: 2020arXiv200409658C
NASA's WB-57 High Altitude Research Program provides a deployable,
mobile, and stratospheric platform for scientific research. Airborne
platforms are of particular value for making coronal observations
during total solar eclipses because of their ability both to follow the
Moon's shadow and to get above most of the atmospheric air mass that
can interfere with astronomical observations. We used the 2017 August
21 eclipse as a pathfinding mission for high-altitude airborne solar
astronomy, using the existing high-speed visible-light and near/midwave
infrared imaging suite mounted in the WB-57 nose cone. In this paper,
we describe the aircraft, the instrument, and the 2017 mission;
operations and data acquisition; and preliminary analysis of data
quality from the existing instrument suite. We describe benefits and
technical limitations of this platform for solar and other astronomical
observations. We present a preliminary analysis of the visible-light
data quality and discuss the limiting factors that must be overcome
with future instrumentation. We conclude with a discussion of lessons
learned from this pathfinding mission and prospects for future research
at upcoming eclipses, as well as an evaluation of the capabilities of
the WB-57 platform for future solar astronomy and general astronomical
observation.
Title: Major Scientific Challenges and Opportunities in Understanding
Magnetic Reconnection and Related Explosive Phenomena throughout
the Universe
Authors: Ji, H.; Alt, A.; Antiochos, S.; Baalrud, S.; Bale, S.;
Bellan, P. M.; Begelman, M.; Beresnyak, A.; Blackman, E. G.; Brennan,
D.; Brown, M.; Buechner, J.; Burch, J.; Cassak, P.; Chen, L. -J.;
Chen, Y.; Chien, A.; Craig, D.; Dahlin, J.; Daughton, W.; DeLuca, E.;
Dong, C. F.; Dorfman, S.; Drake, J.; Ebrahimi, F.; Egedal, J.; Ergun,
R.; Eyink, G.; Fan, Y.; Fiksel, G.; Forest, C.; Fox, W.; Froula, D.;
Fujimoto, K.; Gao, L.; Genestreti, K.; Gibson, S.; Goldstein, M.; Guo,
F.; Hesse, M.; Hoshino, M.; Hu, Q.; Huang, Y. -M.; Jara-Almonte, J.;
Karimabadi, H.; Klimchuk, J.; Kunz, M.; Kusano, K.; Lazarian, A.;
Le, A.; Li, H.; Li, X.; Lin, Y.; Linton, M.; Liu, Y. -H.; Liu, W.;
Longcope, D.; Loureiro, N.; Lu, Q. -M.; Ma, Z-W.; Matthaeus, W. H.;
Meyerhofer, D.; Mozer, F.; Munsat, T.; Murphy, N. A.; Nilson, P.;
Ono, Y.; Opher, M.; Park, H.; Parker, S.; Petropoulou, M.; Phan, T.;
Prager, S.; Rempel, M.; Ren, C.; Ren, Y.; Rosner, R.; Roytershteyn,
V.; Sarff, J.; Savcheva, A.; Schaffner, D.; Schoeffier, K.; Scime, E.;
Shay, M.; Sitnov, M.; Stanier, A.; TenBarge, J.; Tharp, T.; Uzdensky,
D.; Vaivads, A.; Velli, M.; Vishniac, E.; Wang, H.; Werner, G.; Xiao,
C.; Yamada, M.; Yokoyama, T.; Yoo, J.; Zenitani, S.; Zweibel, E.
Bibcode: 2020arXiv200400079J
Altcode:
This white paper summarizes major scientific challenges and
opportunities in understanding magnetic reconnection and related
explosive phenomena as a fundamental plasma process.
Title: Eclipse Results from the Airborne Infrared Spectrometer
(AIR-Spec) and the Extreme-ultraviolet Imaging Spectrometer (EIS)
Authors: Tañón Reyes, N.; Samra, J.; Madsen, C.; DeLuca, E.
Bibcode: 2020AAS...23521009T
Altcode:
The Sun's dynamic outermost atmospheric layer, the corona, exhibits
extremely high temperatures meaning it's in a state of hydrostatic
and thermodynamic disequilibrium which leads to solar activity,
such as flares and coronal mass ejections. This activity can
dramatically affect humanity's infrastructure and technology in
space and on Earth. Understanding the coronal magnetic field would
allow for predictions of these magnetic reconnection-driven violent
events. Measuring the magnetic field is possible via the study of
magnetically sensitive emission lines in the infrared (IR) via the
Zeeman effect. The corona emits some IR emission lines, however, the
solar surface's intensity overwhelms them. To study these lines, we can
observe total solar eclipses wherein the moon blocks out the surface's
continuous emission. The Airborne Infrared Spectrometer (AIR-Spec) is
a pathfinder for future infrared spectrometers and spectro-polarimeters
that will measure the coronal magnetic field. On July 2, 2019 AIR-Spec
observed the total solar eclipse over the South Pacific from onboard
an aircraft. It flew at 13km to avoid low-altitude water vapor, the
primary absorber of IR radiation on Earth. AIR-Spec characterized four
emission lines to determine their viability for future instruments to
measure the coronal magnetic field. Comparing the intensity gradients
for the observed IR lines with extreme-ultraviolet (EUV) lines from
the EUV Imaging Spectrometer (EIS) gives us information regarding
the excitation processes in the corona, providing improvements to the
atomic models. We also determine the value of the IR lines as plasma
temperature and density diagnostics, using EIS data to supplement
our analysis. The analysis of the temperature and density will help
explain the behavior of the plasma, which will allow the mapping of the
coronal magnetic field. Lastly, we discuss how AIR-Spec will continue
its mission during both the 2020 and 2024 total solar eclipses as
well as its influence on future spectro-polarimetric missions. This
work is supported by the NSF-REU solar physics program at SAO [grant#
AGS-1560313] and the NSF Airborne InfraRed Spectrograph (AIR-Spec)
2019 Eclipse Flight [award# 1822314].
Title: The 2019 AIR-Spec Mission: Results from Coordinated Infrared
and EUV Spectroscopic Observations of the Corona During the South
Pacific Total Solar Eclipse
Authors: Madsen, C. A.; Samra, J.; Tañón Reyes, N.; DeLuca, E.
Bibcode: 2019AGUFMSH33A..04M
Altcode:
After a successful maiden voyage in 2017, The Airborne Infrared
Spectrometer (AIR-Spec) embarked on another observing mission, this
time targeting the July 2, 2019 total solar eclipse over the South
Pacific Ocean. AIR-Spec, designed specifically for operation onboard
aircraft, observes coronal infrared emission lines between 1.4 μm and
3.0 μm during total solar eclipses. It proved its viability during
the August 21, 2017 total solar eclipse and underwent significant
design improvements in preparation for the 2019 mission, resulting
in a vastly reduced thermal background and more precise pointing
control. These improvements allowed for an unprecedented view of the
underexplored near-infrared corona, a wavelength regime critical to the
advancement of solar physics due to the potential for direct coronal
magnetic field measurements via spectrally resolved observations of the
Zeeman effect. In pursuit of this goal, and with coordinated support
from the Extreme-ultraviolet Imaging Spectrometer (EIS), we present
the results from a number of studies involving four infrared lines
detected by AIR-Spec: S XI 1.39 μm, Si X 1.43 μm, S XI 1.92 μm, and
Fe IX 2.85 μm. First, we explore the effects of photoexcitation upon
the Si X 1.43 μm line by comparing its spatial radiance profile to
Si X lines in the EUV, further constraining atomic models of coronal
emission such as CHIANTI. Next, we probe the diagnostic potential
of the electron density-sensitive S XI 1.39/1.92 μm line pair while
characterizing the uncertainties arising from atmospheric absorption in
and around the S XI 1.39 μm line. Also, as an extension to previously
published research, we take advantage of the improved sensitivity and
stability of AIR-Spec to perform more precise temperature diagnostics
using the emission measure (EM) loci method. Finally, we demonstrate
how these results will influence future AIR-Spec missions and upcoming
spectro-polarimetric instruments, including those planned for the Daniel
K. Inouye Solar Telescope (DKIST) as well as a proposed balloon-based
coronagraph for coronal magnetic field measurements.
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 Study of Equatorial Coronal Holes during the Maximum Phase
of Four Solar Cycles
Authors: Karna, N.; Karna, M. L.; Saar, S. H.; Pesnell, W. D.;
DeLuca, E.
Bibcode: 2019AGUFMSH44A..03K
Altcode:
The 11-year Solar Cycle (SC) is characterized by periodic changes
in the solar activity such as sunspot numbers, coronal holes, active
regions, eruptions such as prominence eruptions, flares and coronal
mass ejections. In this work we performed a statistical study of the
equatorial coronal holes and the active regions during the maximum
phases of four solar cycles (SC 21 (1979, 1980, 1981 and 1982), SC 22
(1989, 1990, 1991 and 1992), SC 23 (1999, 2000, 2001 and 2002) and SC 24
(2012, 2013, 2014 and 2015)). We compared equatorial coronal hole and
active region numbers, separations between equatorial coronal holes and
active regions centroids, solar wind speed and the number of intense
geomagnetic storms data over these four cycles. We found that the
distance between equatorial coronal holes and active regions, the solar
wind speed, and the the number of intense geomagnetic storms increases
with average sunspot maximum number for even cycles and decreases
with average sunspot maximum for odd cycles. We also noticed that the
solar wind speeds, pressures, and the number of intense geomagnetic
storms increase with the numbers of close equatorial coronal holes and
active regions, suggesting a possible link between equatorial coronal
holes--active regions interactions and the wind phenomena.
Title: A Vis/IR Spectropolarmetric Filtergraph for the COSMO Large
Coronagraph
Authors: DeLuca, E.
Bibcode: 2019AGUFMSH31C3326D
Altcode:
The COronal Solar Magnetism Observatory (COSMO) is proposed to NSF
as a Mid-Scale R-2 facility. The central instrument in the COSMO
suite is a 1.5m-aperture Large Coronagraph (LC) and filtergraph that
will obtain daily measurements the coronal magnetic field strength
and orientation, velocity, temperature, density and emission line
intensity. Other COSMO instruments will measure the chromospheric
and prominence vector magnetic and velocity field and intensity,
and the coronal electron density. The COSMO LC & filtergraph
will be a versatile instrument with broad temperature coverage across
the corona. The basic requirements are: (1) internally occulted Lyot
coronagraph with 1.5m diameter lens; (2) field of view of 1°; (3) 2
arc sec spatial resolution; (4) spectral resolution λ/Δλ>8000;
(5) wavelength range from 500 to 1100 nm; (6) coronal magnetic field
sensitivity of 1 G in 15 min; (7) cadence of 1 s for intensity and
Doppler measurements. We will give an overview of the science
requirements that drive the LC and filtergraph design and report on
the expected performance from the current design.
Title: High-Altitude Instrumentation for Infrared Observations of
the Solar Corona
Authors: Samra, J.; Cheimets, P.; DeLuca, E.; Golub, L.; Hannigan,
J. W.; Judge, P. G.; Madsen, C. A.; Marquez, V.; Tañón Reyes, N.;
Tomczyk, S.
Bibcode: 2019AGUFMSH43B..07S
Altcode:
High-altitude infrared remote sensing is a promising new method for
measuring coronal plasma and magnetic fields. We present new results
from a recent airborne eclipse mission and outline concepts for future
airborne and balloon-based instruments for coronal spectroscopy
and spectro-polarimetry. The airborne infrared spectrometer
(AIR-Spec) was commissioned during the 2017 total solar eclipse,
when it observed five infrared coronal emission lines from the NSF
Gulfstream V research jet. These magnetically sensitive emission lines
of highly ionized magnesium, silicon, sulfur, and iron are promising
candidates for future observations of the coronal magnetic field, and
their characterization is an important first step toward developing
the next generation of instrumentation for coronal magnetometry. The
second AIR-Spec research flight took place during the July 2, 2019
total solar eclipse across the south Pacific. Higher sensitivity and
reduced jitter enabled more precise measurements of emission line
properties and plasma density, temperature, and line-of-sight velocity
up to one solar radius from the solar limb. Atmospheric absorption
was significant, even at altitude, and atmospheric modeling was
required to extract accurate line intensities. AIR-Spec is a slit
spectrometer that measures light over a 1.55 solar radius field of view
in three spectral passbands between 1.4 and 3 microns. The successful
eclipse missions overcame a number of engineering challenges, centered
around maintaining adequate resolution and signal-to-noise ratio in
a compact and inexpensive package on a moving platform. AIR-Spec is a
pathfinder for future infrared spectrometers and spectro-polarimeters,
including a balloon-based coronagraph that will measure the global
coronal magnetic field and an airborne spectrometer that will survey
the infrared emission corona during a future eclipse.
Title: Novel observations of the middle corona during the 2017 total
solar eclipse
Authors: Caspi, A.; Seaton, D. B.; Tsang, C.; DeForest, C.; Bryans,
P.; Samra, J.; DeLuca, E.; Tomczyk, S.; Burkepile, J.; Gallagher,
P.; Golub, L.; Judge, P. G.; Laurent, G. T.; West, M.; Zhukov, A.
Bibcode: 2019AGUFMSH13A..10C
Altcode:
Total solar eclipses offer rare opportunities to study the middle
corona. This intriguing region contains complex interfaces and
transitions between physical regimes, but has historically been
under-observed due to the challenges of observing its dim emission so
close to the bright inner corona and blinding solar disk. The unique
circumstances of a total solar eclipse coupled with a high-altitude
observing platform provide nearly space-quality observing conditions,
including for wavelengths inaccessible by ground-based observatories,
but with availability of ground-quality resources, including high-speed,
high-resolution, wide-field coronography typically inaccessible
from space. We used the 2017 August 21 "Great American" total solar
eclipse to observe the solar corona from ~1.02 to ~3 RSun
in both visible (533.9 ± 4.75 nm) and medium-wave infrared (3-5
μm) light using stabilized telescopes on two of NASA's WB-57F
high-altitude research aircraft. This pathfinding mission utilized
existing instrumentation to evaluate the platform performance, guide
instrumentation development, and explore new discovery space for
future studies of the middle corona. We present the high-speed
(30 Hz), high-resolution (3 arcsec/pixel) visible and IR observations
obtained during the eclipse, and analysis of these observations
in the context of coronal structure and dynamics. We discuss the
limitations of the prototype data and pathways forward for future
instrumentation and missions optimized for the range of observable
parameters in the middle corona. We also discuss the benefits of
such eclipse studies to an understanding of the corona as a single,
unified system, from its origins at the solar surface to its extension
into the heliosphere, particularly within the context of a developing
multi- and inter-disciplinary research collaboration, COHERENT (the
"Corona as a Holistic Environment" Research Network).
Title: Solar Eclipse Observations from the Ground and Air from 0.31
to 5.5 Microns
Authors: Judge, Philip; Berkey, Ben; Boll, Alyssa; Bryans, Paul;
Burkepile, Joan; Cheimets, Peter; DeLuca, Edward; de Toma, Giuliana;
Gibson, Keon; Golub, Leon; Hannigan, James; Madsen, Chad; Marquez,
Vanessa; Richards, Austin; Samra, Jenna; Sewell, Scott; Tomczyk,
Steven; Vera, Alysha
Bibcode: 2019SoPh..294..166J
Altcode:
We present spectra and broad-band polarized light data from a novel
suite of instruments deployed during the 21st August 2017 total solar
eclipse. Our goals were to survey solar spectra at thermal infrared
wavelengths during eclipse, and to test new technology for measuring
polarized coronal light. An infrared coronal imaging spectrometer,
flown at 14.3 km altitude above Kentucky, was supported on the ground
by observations from Madras, Oregon (elevation 683 m) and Camp Wyoba
on Casper Mountain, Wyoming (2402 m). In Wyoming we deployed a new
infrared Fourier Transform Spectrometer (FTS), three low-dispersion
spectrometers loaned to us by Avantes, a novel visible-light camera
PolarCam, sensitive to linear polarization, and one of two infrared
cameras from FLIR Systems, the other operated at Madras. Circumstances
of eclipse demanded that the observations spanned 17:19 to 18:26
UT. We analyze spectra of the limb photosphere, the chromosphere,
prominences, and coronal lines from 310 nm to 5.5 μm. We calibrated
data photometrically using the solar disk as a source. Between different
spectrometers, the calibrations were consistent to better than 13%. But
the sensitivities achieved were insufficient to detect coronal lines
from the ground. The PolarCam data are in remarkable agreement with
polarization data from the K-Cor synoptic instrument on Mauna Loa, and
with FLIR intensity data acquired in Madras. We discuss new results,
including a detection of the He I 1083 nm multiplet in emission during
the whole of totality. The combination of the FTS and AIR-Spec spectra
reveals for the first time the effects of the telluric extinction
on the infrared coronal emission lines, to be observed with upcoming
Daniel K. Inouye Solar Telescope.
Title: Forward Modeling of a Pseudostreamer
Authors: Karna, Nishu; Savcheva, Antonia; Dalmasse, Kévin; Gibson,
Sarah; Tassev, Svetlin; de Toma, Giuliana; DeLuca, Edward E.
Bibcode: 2019ApJ...883...74K
Altcode:
In this paper, we present an analysis of a pseudostreamer embedding
a filament cavity, observed on 2015 April 18 on the solar southwest
limb. We use the flux-rope insertion method to construct nonlinear
force-free field (NLFFF) models constrained by observed Solar Dynamics
Observatory (SDO)/AIA coronal structures and the SDO/Helioseismic
Magnetic Imager photospheric magnetogram. The resulting magnetic field
models are forward-modeled to produce synthetic data directly comparable
to Mauna Loa Solar Observatory/Coronal Multichannel Polarimeter (CoMP)
observations of the intensity and linear polarization of the Fe XIII
1074.7 nm infrared coronal emission line using FORWARD. In addition,
we determine the location of quasi-separatrix layers in the magnetic
models, producing a Q-map from which the signatures of magnetic null
points and separatrices can be identified. An apparent magnetic null
observed in linear polarization by CoMP is reproduced by the model
and appears in the region of the 2D-projected magnetic null in the
Q-map. Further, we find that the height of the CoMP null is better
reproduced by our NLFFF model than by the synthetic data we produce
with potential-field source-surface models, implying the presence of
a flux rope in the northern lobe of the pseudostreamer.
Title: Unfolding Overlapped Slitless Imaging Spectrometer Data for
Extended Sources
Authors: Winebarger, Amy R.; Weber, Mark; Bethge, Christian; Downs,
Cooper; Golub, Leon; DeLuca, Edward; Savage, Sabrina; del Zanna,
Giulio; Samra, Jenna; Madsen, Chad; Ashraf, Afra; Carter, Courtney
Bibcode: 2019ApJ...882...12W
Altcode: 2018arXiv181108329W
Slitless spectrometers can provide simultaneous imaging and spectral
data over an extended field of view, thereby allowing rapid data
acquisition for extended sources. In some instances, when the object
is greatly extended or the spectral dispersion is too small, there
may be locations in the focal plane where emission lines at different
wavelengths contribute. It is then desirable to unfold the overlapped
regions in order to isolate the contributions from the individual
wavelengths. In this paper, we describe a method for such an unfolding,
using an inversion technique developed for an extreme ultraviolet
imaging spectrometer and coronagraph named the COronal Spectroscopic
Imager in the EUV (COSIE). The COSIE spectrometer wavelength range
(18.6-20.5 nm) contains a number of strong coronal emission lines and
several density sensitive lines. We focus on optimizing the unfolding
process to retrieve emission measure maps at constant temperature,
maps of spectrally pure intensity in the Fe XII and Fe XIII lines,
and density maps based on both Fe XII and Fe XIII diagnostics.
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: Frequency Agile Solar Radiotelescope
Authors: Bastian, Tim; Bain, H.; Bradley, R.; Chen, B.; Dahlin, J.;
DeLuca, E.; Drake, J.; Fleishman, G.; Gary, D.; Glesener, L.; Guo,
Fan; Hallinan, G.; Hurford, G.; Kasper, J.; Ji, Hantao; Klimchuk,
J.; Kobelski, A.; Krucker, S.; Kuroda, N.; Loncope, D.; Lonsdale,
C.; McTiernan, J.; Nita, G.; Qiu, J.; Reeves, K.; Saint-Hilaire, P.;
Schonfeld, S.; Shen, Chengcai; Tun, S.; Wertheimer, D.; White, S.
Bibcode: 2019astro2020U..56B
Altcode:
We describe the science objectives and technical requirements for a
re-scoped Frequency Agile Solar Radiotelescope (FASR). FASR fulfills
a long term community need for a ground-based, solar-dedicated, radio
telescope - a next-generation radioheliograph - designed to perform
ultra-broadband imaging spectropolarimetry.
Title: Coronal Plasma Characterization via Coordinated Infrared and
Extreme Ultraviolet Observations of a Total Solar Eclipse
Authors: Madsen, Chad A.; Samra, Jenna E.; Del Zanna, Giulio; DeLuca,
Edward E.
Bibcode: 2019ApJ...880..102M
Altcode: 2019arXiv190110425M
We present coordinated coronal observations of the 2017 August 21 total
solar eclipse with the Extreme-ultraviolet Imaging Spectrometer (EIS)
and the Airborne Infrared Spectrometer (AIR-Spec). These instruments
provide an unprecedented view of the solar corona in two disparate
wavelength regimes, the extreme ultraviolet (EUV) and the near- to
mid-infrared (IR), opening new pathways for characterizing the complex
coronal plasma environment. During totality, AIR-Spec sampled coronal
IR spectra near the equatorial west limb, detecting strong sources
of Mg VIII, S XI, Si IX, and Si X in two passbands encompassing 1.4-4
μm. We apply an intensity-ratio diagnostic to a strong resonant Fe XII
line pair arising from the coordinated EIS observations. This results
in a high-resolution map of electron density throughout the shared
EIS/AIR-Spec field of view. Electron density measurements allow us to
produce a similar map of plasma temperature using emission measure
(EM) loci analysis as applied to 27 EIS emission lines, providing
temperatures of 106.12 ± 103.5 K along the
limb and 106.19 ± 103.5 K at about 100″
outward. Applying EM loci analysis to AIR-Spec IR spectra coadded
over two 31″ wide ranges centered at two locations, 30″ and
100″ from the limb, produces temperatures consistent with the EIS
data, albeit suffering from moderate uncertainties. Regardless, we
demonstrate that EUV spectral data are valuable constraints to coronal
IR emission models, and will be powerful supplements for future IR
solar observatories, particularly DKIST.
Title: Nonlinear Force-free Field Modeling of Solar Coronal Jets in
Theoretical Configurations
Authors: Meyer, K. A.; Savcheva, A. S.; Mackay, D. H.; DeLuca, E. E.
Bibcode: 2019ApJ...880...62M
Altcode:
Coronal jets occur frequently on the Sun, and may contribute
significantly to the solar wind. With the suite of instruments
available now, we can observe these phenomena in greater detail
than ever before. Modeling and simulations can assist further with
understanding the dynamic processes involved, but previous studies
tended to consider only one mechanism (e.g., emergence or rotation)
for the origin of the jet. In this study we model a series of idealized
archetypal jet configurations and follow the evolution of the coronal
magnetic field. This is a step toward understanding these idealized
situations before considering their observational counterparts. Several
simple situations are set up for the evolution of the photospheric
magnetic field: a single parasitic polarity rotating or moving in a
circular path; as well as opposite polarity pairs involved in flyby
(shearing), cancellation or emergence; all in the presence of a uniform,
open background magnetic field. The coronal magnetic field is evolved in
time using a magnetofrictional relaxation method. While magnetofriction
cannot accurately reproduce the dynamics of an eruptive phase, the
structure of the coronal magnetic field, as well as the buildup of
electric currents and free magnetic energy are instructive. Certain
configurations and motions produce a flux rope and allow the significant
buildup of free energy, reminiscent of the progenitors of so-called
blowout jets, whereas other, simpler configurations are more comparable
to the standard jet model. The next stage is a comparison with observed
coronal jet structures and their corresponding photospheric evolution.
Title: Data-optimized Coronal Field Model. I. Proof of Concept
Authors: Dalmasse, K.; Savcheva, A.; Gibson, S. E.; Fan, Y.; Nychka,
D. W.; Flyer, N.; Mathews, N.; DeLuca, E. E.
Bibcode: 2019ApJ...877..111D
Altcode: 2019arXiv190406308D
Deriving the strength and direction of the three-dimensional
(3D) magnetic field in the solar atmosphere is fundamental for
understanding its dynamics. Volume information on the magnetic field
mostly relies on coupling 3D reconstruction methods with photospheric
and/or chromospheric surface vector magnetic fields. Infrared
coronal polarimetry could provide additional information to better
constrain magnetic field reconstructions. However, combining such
data with reconstruction methods is challenging, e.g., because of the
optical thinness of the solar corona and the lack and limitations of
stereoscopic polarimetry. To address these issues, we introduce the
data-optimized coronal field model (DOCFM) framework, a model-data
fitting approach that combines a parameterized 3D generative model,
e.g., a magnetic field extrapolation or a magnetohydrodynamic model,
with forward modeling of coronal data. We test it with a parameterized
flux-rope insertion method and infrared coronal polarimetry where
synthetic observations are created from a known “ground-truth”
physical state. We show that this framework allows us to accurately
retrieve the ground-truth 3D magnetic field of a set of force-free
field solutions from the flux-rope insertion method. In observational
studies, the DOCFM will provide a means to force the solutions
derived with different reconstruction methods to satisfy additional
common coronal constraints. The DOCFM framework therefore opens new
perspectives for the exploitation of coronal polarimetry in magnetic
field reconstructions and for developing new techniques to more
reliably infer the 3D magnetic fields that trigger solar flares and
coronal mass ejections.
Title: Major Scientific Challenges and Opportunities in Understanding
Magnetic Reconnection and Related Explosive Phenomena throughout
the Universe
Authors: Ji, Hantao; Alt, A.; Antiochos, S.; Baalrud, S.; Bale, S.;
Bellan, P. M.; Begelman, M.; Beresnyak, A.; Blackman, E. G.; Brennan,
D.; Brown, M.; Buechner, J.; Burch, J.; Cassak, P.; Chen, L. -J.;
Chen, Y.; Chien, A.; Craig, D.; Dahlin, J.; Daughton, W.; DeLuca, E.;
Dong, C. F.; Dorfman, S.; Drake, J.; Ebrahimi, F.; Egedal, J.; Ergun,
R.; Eyink, G.; Fan, Y.; Fiksel, G.; Forest, C.; Fox, W.; Froula, D.;
Fujimoto, K.; Gao, L.; Genestreti, K.; Gibson, S.; Goldstein, M.;
Guo, F.; Hesse, M.; Hoshino, M.; Hu, Q.; Huang, Y. -M.; Jara-Almonte,
J.; Karimabadi, H.; Klimchuk, J.; Kunz, M.; Kusano, K.; Lazarian,
A.; Le, A.; Li, H.; Li, X.; Lin, Y.; Linton, M.; Liu, Y. -H.; Liu,
W.; Longcope, D.; Louriero, N.; Lu, Q. -M.; Ma, Z. -W.; Matthaeus,
W. H.; Meyerhofer, D.; Mozer, F.; Munsat, T.; Murphy, N. A.; Nilson,
P.; Ono, Y.; Opher, M.; Park, H.; Parker, S.; Petropoulou, M.; Phan,
T.; Prager, S.; Rempel, M.; Ren, C.; Ren, Y.; Rosner, R.; Roytershteyn,
V.; Sarff, J.; Savcheva, A.; Schaffner, D.; Schoeffier, K.; Scime, E.;
Shay, M.; Sitnov, M.; Stanier, A.; TenBarge, J.; Tharp, T.; Uzdensky,
D.; Vaivads, A.; Velli, M.; Vishniac, E.; Wang, H.; Werner, G.; Xiao,
C.; Yamada, M.; Yokoyama, T.; Yoo, J.; Zenitani, S.; Zweibel, E.
Bibcode: 2019BAAS...51c...5J
Altcode: 2019astro2020T...5J
This is a group white paper of 100 authors (each with explicit
permission via email) from 51 institutions on the topic of magnetic
reconnection which is relevant to 6 thematic areas. Grand challenges
and research opportunities are described in observations, numerical
modeling and laboratory experiments in the upcoming decade.
Title: Erratum: “Discovery of New Coronal Lines at 2.843 and 2.853
μm” (2018,
ApJL, 856, L29)
Authors: Samra, Jenna E.; Judge, Philip G.; DeLuca, Edward E.;
Hannigan, James W.
Bibcode: 2019ApJ...873L..25S
Altcode:
No abstract at ADS
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: Heliophysics Science enabled by Lunar Orbiting Platforms
Authors: Spann, James; DeLuca, . Edward; Spence, Harlan; Savage,
Sabrina; Giles, Barbara; Paxton, Larry; Kasper, Justin; Horanyi,
Mihaly; Clark, Pamela; Collado-Vega, Yaireska
Bibcode: 2018cosp...42E3213S
Altcode:
The current emphasis on returning to the Moon with a lunar orbiting
platform provides an impetus and opportunity to explore newly enabled
investigations that are relevant to heliophysics and to understand
the coupling of the sun and its atmosphere to the magnetized space
environment surrounding the Earth. To that end, a workshop focused
on the science that the NASA Deep Space Gateway (DSG) platform
enables was held with focused topics including heliophysics, space
weather/radiation, Earth science, astrophysics, lunar and planetary,
crosscutting technologies, telerobotics, human exploration support,
and sample collection/return. Following this, a session at the Triennial
Earth-Sun Summit (TESS) focused on the heliophysics science enabled by
the DSG was convened. This talk will summarize the major heliophysics
themes of those two meetings and provide context for science strategies
that take advantage of lunar orbiting platforms, and for technologies
required to realize the full benefit of the synergy of human and
robotic exploration in the vicinity of the Moon.
Title: New Coronal Science from NASA WB-57F High-Altitude Aircraft
Observations of the 2017 Total Solar Eclipse
Authors: Caspi, Amir; DeLuca, . Edward; Tomczyk, Steven; DeForest,
Craig; Bryans, Paul; Seaton, Daniel; Tsang, Constantine
Bibcode: 2018cosp...42E.526C
Altcode:
Total solar eclipses present rare opportunities to study the
complex solar corona, down to altitudes of just a few percent of
a solar radius above the surface, using ground-based and airborne
observatories that would otherwise be dominated by the intense solar
disk and high sky brightness. Studying the corona is critical to
gaining a better understanding of physical processes that occur on
other stars and astrophysical objects, as well as understanding the
dominant driver of space weather that affects human assets at Earth and
elsewhere. For example, it is still poorly understood how the corona
is heated to temperatures of 1-2 MK globally and up to 5-10 MK above
active regions, while the underlying chromosphere is 100 times cooler;
numerous theories abound, but are difficult to constrain due to the
limited sensitivities and cadences of prior measurements. The stability
of large-scale coronal structures and the extent of their reach to the
middle and outer corona are also not well known, limited in large part
by sensitivities and fields of view of existing observations.Airborne
observations during a total eclipse provide unique advantages. By
flying in the stratosphere at altitudes of 50 kft or higher, they
avoid all weather, the seeing quality is enormously improved, and
additional wavelengths such as near-IR also become available due to
significantly reduced water absorption. An airborne observatory can
also follow the Moon's shadow, increasing the total observing time by
50% or more.We present current results of solar coronal measurements
from airborne observations of the 2017 Great American Total Solar
Eclipse using two of NASA's WB-57 high-altitude research aircraft,
each equipped with two 8.7" telescopes feeding high-sensitivity visible
(green line and nearby continuum) and medium-wave IR (3-5 {μ}m) cameras
operating at high cadence (30 Hz) with ∼3 arcsec/pixel platescale and
±3 R_{sun} fields of view. The aircraft flew along the eclipse path,
separated by ∼110 km, to observe a summed ∼7.5 minutes of totality
in both visible and MWIR. These observations enable groundbreaking
studies of high-speed coherent motion - including possible Alfvén
waves and nanojets - in the lower and middle corona that could shed
light on coronal heating processes and the formation and stability of
coronal structures. Our MWIR observations of a cool prominence and
hot coronal active region plasma will be combined with spectra from
the AIR-Spec instrument, flown concurrently on NCAR's HIAPER GV. We
review the WB-57 eclipse mission and the current results of analysis
on the visible and IR coronal measurements, along with an outlook for
future analysis and missions.
Title: Heliophysics Science enabled by Lunar Orbiting Platforms
Authors: Spann, James F.; Giles, Barbara L.; Spence, Harlan E.; Savage,
Sabrina L.; Paxton, Larry J.; Kasper, Justin Christophe; Horanyi,
Mihaly; DeLuca, Edward; Collado-Vega, Yaireska M.; Clark, Pamela
Bibcode: 2018tess.conf22001S
Altcode:
The current emphasis on returning to the Moon with a lunar orbiting
platform provides an impetus and opportunity to explore newly enabled
investigations that are relevant to heliophysics and to understand
the coupling of the sun and its atmosphere to the magnetized space
environment surrounding the Earth. To that end, a workshop focused on
the science that the NASA Deep Space Gateway platform enables was held
with focused topics including heliophysics, space weather/radiation,
Earth science, astrophysics, lunar and planetary, crosscutting
technologies, telerobotics, human exploration support, and sample
collection/return. This talk will summarize the major heliophysics
themes of that workshop and provide context for science strategies
that take advantage of lunar orbiting platforms, and for technologies
required to realize the full benefit of the synergy of human and
robotic exploration in the vicinity of the Moon.
Title: Eclipse Science from 50,000 Feet: New Coronal Results from
NASA WB-57F High-Altitude Aircraft Observations of the 2017 Total
Solar Eclipse
Authors: Caspi, Amir; Tsang, Constantine; Seaton, Daniel B.; DeForest,
Craig; Bryans, Paul; DeLuca, Edward; Tomczyk, Steven; Burkepile,
Joan; Casey, Thomas Anthony; Collier, John; Darrow, Donald DD; Del
Rosso, Dominic; Durda, Daniel D.; Gallagher, Peter; Gascar, Jasmine;
Golub, Leon; Jacyna, Matthew; Johnson, David DJ; Judge, Philip G.;
Klemm, Cary; Laurent, Glenn Thomas; Lewis, Johanna; Mallini, Charles;
Parent, Thomas Duster; Propp, Timothy; Steffl, Andrew; Warner, Jeff;
West, Matthew John; Wiseman, John; Yates, Mallory; Zhukov, Andrei
Bibcode: 2018tess.conf31302C
Altcode:
Total solar eclipses present rare opportunities to study the complex
solar corona, down to altitudes of just a few percent of a solar
radius above the surface. Studying the corona is critical to gaining
a better understanding of the dominant driver of space weather that
affects human assets on Earth and elsewhere. For example, it is still
poorly understood how the corona is heated to temperatures of 1-2 MK
globally and up to 5-10 MK above active regions, while the underlying
chromosphere is 100 times cooler. The stability of large-scale coronal
structures and the extent of their reach to the middle and outer corona
are also not well known, limited in large part by sensitivities and
fields of view of existing observations. Airborne observations
during a total eclipse provide unique advantages. By flying in the
stratosphere at altitudes of 50 kft or higher, they avoid all weather,
the seeing quality is enormously improved, and additional wavelengths
such as near-IR also become available due to significantly reduced
water absorption. An airborne observatory can also follow the Moon's
shadow, increasing the total observing time by 50% or more. We
present current results of solar coronal measurements from airborne
observations of the 2017 Great American Total Solar Eclipse using two
of NASA's WB-57 high-altitude research aircraft, each equipped with
two 8.7-inch telescopes feeding high-sensitivity visible (green line
and nearby continuum) and medium-wave IR (3-5 μm) cameras operating
at high cadence (30 Hz) with ∼3 arcsec/pixel platescale and ±3
Rsun fields of view. The two aircraft flew along the eclipse
path, separated by ∼110 km, to observe a total of ∼7.5 minutes
of totality in both visible and MWIR. These observations enable
groundbreaking studies of high-speed coherent motion - including
possible Alfvén waves and nanojets - in the lower and middle corona
that could shed light on coronal heating processes and the formation
and stability of coronal structures. Our MWIR observations of a cool
prominence and hot coronal active region plasma will be combined with
spectra from the AIR-Spec instrument, flown concurrently on NCAR's
HIAPER GV. We review the WB-57 eclipse mission and the current results
of analysis on the visible and IR coronal measurements, along with an
outlook for future analysis and missions.
Title: Using DSG to build the capability of space weather forecasting
in deep space.
Authors: DeLuca, Edward; Golub, Leon; Korreck, Kelly; Savage, Sabrina
L.; McKenzie, David E.; Rachmeler, Laurel; Winebarger, Amy R.; Martens,
Petrus C.
Bibcode: 2018tess.conf22002D
Altcode:
The prospect of astronaut missions to deep space and off the
sun-earth line raises new challenges for space weather awareness
and forecasting. Combined efforts of the science and human flight
communities are needed to identify the requirements and identify
pathways that will allow us to address the requirements for protecting
human life and equipment, on a timescale consistent with the deep space
exploration program. <p class="p1" The Deep Space Gateway provides
a platform where we can develop, test and validate a combined space
weather instrumentation, analysis and forecasting system that can be
used when out of routine contact with near earth based assets. This
presentation will attempt to outline the bounds of the problem and start
the discussion about how to build an independent space weather program.
Title: Discovery of New Coronal Lines at 2.843 and 2.853 μm
Authors: Samra, Jenna E.; Judge, Philip G.; DeLuca, Edward E.;
Hannigan, James W.
Bibcode: 2018ApJ...856L..29S
Altcode:
Two new emission features were observed during the 2017 August 21
total solar eclipse by a novel spectrometer, the Airborne Infrared
Spectrometer (AIR-Spec), flown at 14.3 km altitude aboard the NCAR
Gulfstream-V aircraft. We derive wavelengths in air of 2.8427 ±
0.00009 μm and 2.8529 ± 0.00008 μm. One of these lines belongs to the
3{{{p}}}53{{d}}{}3{{{F}}}3^\circ
\to
3{{{p}}}53{{d}}{}3{{{F}}}4^\circ
transition in Ar-like Fe IX. This appears to be the first
detection of this transition from any source. Minimization of
residual wavelength differences using both measured wavelengths,
together with National Institute of Standards and Technology (NIST)
extreme ultraviolet wavelengths, does not clearly favor assignment to
Fe IX. However, the shorter wavelength line appears more consistent
with other observed features formed at similar temperatures to Fe
IX. The transition occurs between two levels within the excited
3{{{p}}}53{{d}} configuration, 429,000 cm-1
above the ground level. The line is therefore absent in photo-ionized
coronal-line astrophysical sources such as the Circinus Galaxy. Data
from a Fourier transform interferometer (FTIR) deployed from Wyoming
show that both lines are significantly attenuated by telluric
H2O, even at dry sites. We have been unable to identify
the longer wavelength transition.
Title: CisLunar Interchangeable Observatory for Heliophysics (CLIOH):
A Deep Space Gateway Solar Viewing Platform for Technology Development
and Research Payloads
Authors: Savage, S.; DeLuca, E.; Cheimets, P.; Golub, L.; Kobayashi,
K.; McKenzie, D.; Rachmeler, L.; Winebarger, A.
Bibcode: 2018LPICo2063.3061S
Altcode:
The Deep Space Gateway offers an unparalleled opportunity to test
and operate solar instrumentation in a radiation hard environment,
which can be achieved via an external pointing platform designed to
accommodate multiple interchangeable payloads.
Title: Using DSG to Build the Capability of Space Weather Forecasting
in Deep Space
Authors: DeLuca, E. E.; Golub, L.; Korreck, K.; Savage, S.; McKenzie,
D. D.; Rachmeler, L.; Winebarger, A.; Martens, P.
Bibcode: 2018LPICo2063.3050D
Altcode:
The prospect of astronaut missions to deep space and off the
Sun-Earth line raises new challenges for space weather awareness and
forecasting. We need to identify the requirements and pathways that
will allow us to protect human life and equipment.
Title: Solar Coronal Lines in the Visible and Infrared: A Rough Guide
Authors: Del Zanna, Giulio; DeLuca, Edward E.
Bibcode: 2018ApJ...852...52D
Altcode: 2017arXiv170803626D
We review the coronal visible and infrared lines, collecting previous
observations and comparing, whenever available, observed radiances to
those predicted by various models: the quiet Sun (QS), a moderately
active Sun, and an active region as observed near the limb, around
1.1 R ⊙. We also model the off-limb radiances for the QS
case. We used the most up-to-date atomic data in CHIANTI version 8. The
comparison is satisfactory, in that all of the strong visible lines now
have a firm identification. We revise several previous identifications
and suggest some new ones. We also list the large number of observed
lines for which we do not currently have atomic data, and therefore
still await firm identifications. We also show that a significant number
of coronal lines should be observable in the near-infrared region of
the spectrum by the upcoming Daniel K. Inouye Solar Telescope (DKIST)
and the AIR-Spec instrument, which observed the corona during the 2017
August 21 solar eclipse. We also briefly discuss the many potential
spectroscopic diagnostics available to the visible and infrared, with
particular emphasis on measurements of electron densities and chemical
abundances. We briefly point out some of the potential diagnostics
that could be available with the future infrared instrumentation that
is being built for DKIST and planned for the Coronal Solar Magnetism
Observatory. Finally, we highlight the need for further improvements
in the atomic data.
Title: Chasing the Great American 2017 Total Solar Eclipse: Coronal
Results from NASA's WB-57F High-Altitude Research Aircraft
Authors: Caspi, A.; Tsang, C.; DeForest, C. E.; Seaton, D. B.; Bryans,
P.; Burkepile, J.; Casey, T. A.; Collier, J.; Darrow, D.; DeLuca,
E.; Durda, D. D.; Gallagher, P.; Golub, L.; Judge, P. G.; Laurent,
G. T.; Lewis, J.; Mallini, C.; Parent, T.; Propp, T.; Steffl, A.;
Tomczyk, S.; Warner, J.; West, M. J.; Wiseman, J.; Zhukov, A.
Bibcode: 2017AGUFMSH24A..05C
Altcode:
Total solar eclipses present rare opportunities to study the complex
solar corona, down to altitudes of just a few percent of a solar
radius above the surface, using ground-based and airborne observatories
that would otherwise be dominated by the intense solar disk and high
sky brightness. Studying the corona is critical to gaining a better
understanding of physical processes that occur on other stars and
astrophysical objects, as well as understanding the dominant driver of
space weather that affects human assets at Earth and elsewhere. For
example, it is still poorly understood how the corona is heated to
temperatures of 1-2 MK globally and up to 5-10 MK above active regions,
while the underlying chromosphere is 100 times cooler; numerous theories
abound, but are difficult to constrain due to the limited sensitivities
and cadences of prior measurements. The origins and stability of coronal
fans, and the extent of their reach to the middle and outer corona,
are also not well known, limited in large part by sensitivities and
fields of view of existing observations. Airborne observations during
the eclipse provide unique advantages; by flying in the stratosphere
at altitudes of 50 kft or higher, they avoid all weather, the seeing
quality is enormously improved, and additional wavelengths such as
near- IR also become available due to significantly reduced water
absorption. For an eclipse, an airborne observatory can also follow the
shadow, increasing the total observing time by 50% or more. We present
results of solar coronal measurements from airborne observations of
the 2017 Great American Total Solar Eclipse using two of NASA's WB-57
high-altitude research aircraft, each equipped with two 8.7" telescopes
feeding high-sensitivity visible (green-line) and medium-wave IR (3-5
μm) cameras operating at high cadence (30 Hz) with 3 arcsec/pixel
platescale and ±3 R_sun fields of view. The aircraft flew along the
eclipse path, separated by 110 km, to observe a summed 7.5 minutes of
totality in both visible and NIR, enabling groundbreaking studies of
high-speed wave motions and nanojets in the lower corona, the structure
and extent of coronal fans, and constraints on a potential primordial
dust ring around the Sun. We review the mission, and the results of
analysis on the visible and IR coronal measurements.
Title: Results of the IRIS UV Burst Survey, Part I: Active Regions
Tracked Limb to Limb
Authors: Madsen, C. A.; DeLuca, E.
Bibcode: 2017AGUFMSH43A2802M
Altcode:
We present results from the first phase of an effort to thoroughly
characterize UV bursts within the Interface Region Imaging Spectrograph
(IRIS) data catalogue. The observational signatures of these phenomena
include dramatically intensified and broadened NUV/FUV emission line
profiles with absorption features from cool metallic ions. These
properties suggest that UV bursts originate from plasma at transition
region temperatures (≥ 80,000 K) which is deeply embedded in the
cool lower chromosphere ( 5,000 K). Rigorously characterizing the
energetic and dynamical properties of UV bursts is crucial since they
have considerable potential to heat active region chromospheres and
could provide critical constraints for models of magnetic reconnection
in these regions. The survey first focuses on IRIS observations of
active regions tracked from limb to limb. All observations consist
of large field-of-view raster scans of 320 or 400 steps each, which
allow for widespread detection of many burst profiles at the expense
of having limited short-term time evolution information. We detect
bursts efficiently by applying a semi-automated single-Gaussian
fitting technique to Si IV 1393.8 Å emission profiles that isolates
the distinct burst population in a 4-D parameter space. The robust
sample of NUV/FUV burst spectra allows for precise constraints of
properties critical for modeling reconnection in the chromosphere,
including outflow kinetic energy, density estimates from intensity
ratios of Si IV 1402.8 Å and O IV 1401.2 Å emission lines, and
coincident measures of emission in other wavelengths. We also track
burst properties throughout the lifetimes of their host active regions,
noting changes in detection rate and preferential location as the
active regions evolve. Finally, the tracked active region observations
provide a unique opportunity to investigate line-of-sight effects on
observed UV burst spectral properties, particularly the strength of Ni
II 1393.3 Å absorption, a feature that may be important in identifying
the upward conduction of burst thermal energy through the chromosphere.
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: Exploring the Time Evolution of Cool Metallic Absorption
Features in UV Burst Spectra
Authors: Belmes, K.; Madsen, C. A.; DeLuca, E.
Bibcode: 2017AGUFMSH51C2499B
Altcode:
UV bursts are compact brightenings in active regions that appear in
UV images. They are identified through three spectroscopic features:
(1) broadening and intensification of NUV/FUV emission lines, (2)
the presence of optically thin Si IV emission, and (3) the presence
of absorption features from cool metallic ions. Properties (2) and (3)
imply that bursts exist at transition region temperatures (≥ 80,000
K) but are located in the cooler lower chromosphere ( 5,000 K). Their
energetic and dynamical properties remain poorly constrained. Improving
our understanding of this phenomena could help us further constrain the
energetic and dynamical properties of the chromosphere, as well as give
us insight into whether or not UV bursts contribute to chromospheric
and/or coronal heating. We analyzed the time evolution of UV bursts
using spectral data from the Interface Region Imaging Spectrograph
(IRIS). We inspected Si IV 1393.8 Å line profiles for Ni II 1393.3
Å absorption features to look for signs of heating. Weakening of
absorption features over time could indicate heating of the cool ions
above the burst, implying that thermal energy from the burst could
rapidly conduct upward through the chromosphere. To detect the spectral
profiles corresponding to bursts, we applied a four-parameter Gaussian
fit to every profile in each observation and took cuts in parameter
space to isolate the bursts. We then manually reviewed the remaining
profiles by looking for a statistically significant appearance of
Ni II 1393.3 Å absorption. We quantified these absorption features
by normalizing the Si IV 1393.8 Å emission profiles and measuring
the maximum fractional extinction in each. Our preliminary results
indicate that Ni II 1393.3 Å absorption may undergo a cycle of
strengthening and weakening throughout a burst's lifetime. However,
further investigation is needed for confirmation. This work is supported
by the NSF-REU solar physics program at SAO, grant number AGS-1560313.
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: Eclipse Science Results from the Airborne Infrared Spectrometer
(AIR-Spec)
Authors: Samra, J.; Cheimets, P.; DeLuca, E.; Golub, L.; Judge, P. G.;
Lussier, L.; Madsen, C. A.; Marquez, V.; Tomczyk, S.; Vira, A.
Bibcode: 2017AGUFMSH24A..06S
Altcode:
We present the first science results from the commissioning flight
of the Airborne Infrared Spectrometer (AIR-Spec), an innovative
solar spectrometer that will observe the 2017 solar eclipse from
the NSF/NCAR High-Performance Instrumented Airborne Platform for
Environmental Research (HIAPER). During the eclipse, AIR-Spec will
image five magnetically sensitive coronal emission lines between 1.4
and 4 microns to determine whether they may be useful probes of coronal
magnetism. The instrument will measure emission line intensity, FWHM,
and Doppler shift from an altitude of over 14 km, above local weather
and most of the absorbing water vapor. Instrumentation includes an image
stabilization system, feed telescope, grating spectrometer, infrared
camera, and visible slit-jaw imager. Results from the 2017 eclipse
are presented in the context of the mission's science goals. AIR-Spec
will identify line strengths as a function of position in the solar
corona and search for the high frequency waves that are candidates
for heating and acceleration of the solar wind. The instrument will
also identify large scale flows in the corona, particularly in polar
coronal holes. Three of the five lines are expected to be strong in
coronal hole plasmas because they are excited in part by scattered
photospheric light. Line profile analysis will probe the origins
of the fast and slow solar wind. Finally, the AIR-Spec measurements
will complement ground based eclipse observations to provide detailed
plasma diagnostics throughout the corona. AIR-Spec will measure infrared
emission of ions observed in the visible from the ground, giving insight
into plasma heating and acceleration at radial distances inaccessible
to existing or planned spectrometers.
Title: First results from the NASA WB-57 airborne observations of
the Great American 2017 Total Solar Eclipse
Authors: Caspi, Amir; Tsang, Constantine; DeForest, Craig; Seaton,
Daniel B.; Bryans, Paul; Tomczyk, Steven; Burkepile, Joan; Judge,
Phil; DeLuca, Edward E.; Golub, Leon; Gallagher, Peter T.; Zhukov,
Andrei; West, Matthew; Durda, Daniel D.; Steffl, Andrew J.
Bibcode: 2017SPD....4810701C
Altcode:
Total solar eclipses present rare opportunities to study the complex
solar corona, down to altitudes of just a few percent of a solar
radius above the surface, using ground-based and airborne observatories
that would otherwise be dominated by the intense solar disk and high
sky brightness. Studying the corona is critical to gaining a better
understanding of physical processes that occur on other stars and
astrophysical objects, as well as understanding the dominant driver of
space weather that affects human assets at Earth and elsewhere. For
example, it is still poorly understood how the corona is heated to
temperatures of 1-2 MK globally and up to 5-10 MK above active regions,
while the underlying chromosphere is 100 times cooler; numerous theories
abound, but are difficult to constrain due to the limited sensitivities
and cadences of prior measurements. The origins and stability of coronal
fans, and the extent of their reach to the middle and outer corona,
are also not well known, limited in large part by sensitivities and
fields of view of existing observations.Airborne observations during
the eclipse provide unique advantages; by flying in the stratosphere
at altitudes of 50 kft or higher, they avoid all weather, the seeing
quality is enormously improved, and additional wavelengths such
as near-IR also become available due to significantly reduced water
absorption. For an eclipse, an airborne observatory can also follow the
shadow, increasing the total observing time by 50% or more.We present
the first results from airborne observations of the 2017 Great American
Total Solar Eclipse using two of NASA's WB-57 research aircraft, each
equipped with two 8.7" telescopes feeding high-sensitivity visible
(green-line) and near-IR (3-5 µm) cameras operating at high cadence
(30 Hz) with ~3 arcsec/pixel platescale and ±3 R_sun fields of
view. The aircraft will fly along the eclipse path, separated by ~90
km, to observe a summed ~8 minutes of totality in both visible and
NIR, enabling groundbreaking studies of high-speed wave motions and
nanojets in the lower corona, the structure and extent of coronal fans,
and constraints on a potential primordial dust ring around the Sun.
Title: Solving the Coronal Heating Problem using X-ray
Microcalorimeters
Authors: Christe, Steven; Bandler, Simon; DeLuca, Edward; Caspi,
Amir; Golub, Leon; Smith, Randall; Allred, Joel; Brosius, Jeffrey W.;
Dennis, Brian; Klimchuk, James
Bibcode: 2017arXiv170100795C
Altcode:
Even in the absence of resolved flares, the corona is heated to several
million degrees. However, despite its importance for the structure,
dynamics, and evolution of the solar atmosphere, the origin of this
heating remains poorly understood. Several observational and theoretical
considerations suggest that the heating is driven by small, impulsive
energy bursts which could be Parker-style "nanoflares" (Parker 1988)
that arise via reconnection within the tangled and twisted coronal
magnetic field. The classical "smoking gun" (Klimchuk 2009; Cargill et
al. 2013) for impulsive heating is the direct detection of widespread
hot plasma (T > 6 MK) with a low emission measure. In recent years
there has been great progress in the development of Transition Edge
Sensor (TES) X-ray microcalorimeters that make them more ideal for
studying the Sun. When combined with grazing-incidence focusing optics,
they provide direct spectroscopic imaging over a broad energy band
(0.5 to 10 keV) combined with extremely impressive energy resolution
in small pixels, as low as 0.7 eV (FWHM) at 1.5 keV (Lee 2015),
and 1.56 eV (FWHM) at 6 keV (Smith 2012), two orders of magnitude
better than the current best traditional solid state photon-counting
spectrometers. Decisive observations of the hot plasma associated
with nanoflare models of coronal heating can be provided by new solar
microcalorimeters. These measurements will cover the most important part
of the coronal spectrum for searching for the nanoflare-related hot
plasma and will characterize how much nanoflares can heat the corona
both in active regions and the quiet Sun. Finally, microcalorimeters
will enable to study all of this as a function of time and space in
each pixel simultaneously a capability never before available.
Title: Initial Results of a Large-scale Statistical Survey of
Small-scale UV Bursts with IRIS and SDO
Authors: Madsen, C. A.; DeLuca, E.
Bibcode: 2016AGUFMSH31B2570M
Altcode:
UV bursts are small-scale ( 1 arcsec or less) brightenings observed
in the NUV/FUV passbands of the Interface Region Imaging Spectrograph
(IRIS). These peculiar phenomena are found exclusively in active regions
and exhibit dramatic and defining spectroscopic characteristics. In
particular, they present intense broadening and splitting, often
in excess of 70 km s-1, in all bright emission lines observable by
IRIS. Furthermore, these broadened lines also display strong absorption
from cool metallic ions such as Fe II and Ni II which typically
populate the chromosphere. These features suggest that bursts are
bidirectional plasma flows at transition region temperatures embedded
much farther down in the cool chromosphere. To better characterize
these phenomena, we have launched a statistical survey encompassing
the entire IRIS data catalogue to date and its accompanying data from
the Atmospheric Imaging Assembly (AIA) and Helioseismic and Magnetic
Imager (HMI). We sample a wide variety of IRIS observations of Si IV
lines, ranging from large 400-step rasters for large detection rates
to short-cadence sit-and-stare observations to provide in-depth time
evolution data of individual bursts. Detection is streamlined by a
semi-automated method that isolates characteristic burst spectra based
on single-Gaussian fit parameters, greatly reducing search times in the
vast IRIS catalogue. Our initial results demonstrate that UV bursts
tend to appear when active regions are young and actively emerging,
preferring to populate poorly developed inversion lines composed
of numerous small mixed-polarity regions. Burst occurrence rates
peak at 30-70 per hour in young active regions, decreasing as those
regions age. We also find dramatic variations in spectral morphology
in spatial scans of bursts with many split into distinct, opposing,
resolved regions of blueshifts and redshifts. Finally, we find little
evidence for coronal counterparts in AIA 171 Å, but we do find that
a significant ratio of bursts coincide with localized bright features
in AIA 1700 Å, lending support to the link between bursts and Ellerman
bombs. With further involvement in the survey, we hope to constrain the
burst/Ellerman bomb coincidence, the time evolution of burst spectral
morphologies, and the distribution of their peak kinetic energies.
Title: Development of the User Interface for AIR-Spec
Authors: Cervantes Alcala, E.; Guth, G.; Fedeler, S.; Samra, J.;
Cheimets, P.; DeLuca, E.; Golub, L.
Bibcode: 2016AGUFMSM51A2458C
Altcode:
The airborne infrared spectrometer (AIR-Spec) is an imaging
spectrometer that will observe the solar corona during the 2017 total
solar eclipse. This eclipse will provide a unique opportunity to
observe infrared emission lines in the corona. Five spectral lines
are of particular interest because they may eventually be used to
measure the coronal magnetic field. To avoid infrared absorption from
atmospheric water vapor, AIR-Spec will be placed on an NSF Gulfstream
aircraft flying above 14.9 km. AIR-Spec must be capable of taking
stable images while the plane moves. The instrument includes an image
stabilization system, which uses fiber-optic gyroscopes to determine
platform rotation, GPS to calculate the ephemeris of the sun, and
a voltage-driven mirror to correct the line of sight. An operator
monitors a white light image of the eclipse and manually corrects
for residual drift. The image stabilization calculation is performed
by a programmable automatic controller (PAC), which interfaces with
the gyroscopes and mirror controller. The operator interfaces with
a separate computer, which acquires images and computes the solar
ephemeris. To ensure image stabilization is successful, a human machine
interface (HMI) was developed to allow connection between the client
and PAC. In order to make control of the instruments user friendly
during the short eclipse observation, a graphical user interface
(GUI) was also created. The GUI's functionality includes turning
image stabilization on and off, allowing the user to input information
about the geometric setup, calculating the solar ephemeris, refining
estimates of the initial aircraft attitude, and storing data from
the PAC on the operator's computer. It also displays time, location,
attitude, ephemeris, gyro rates and mirror angles.
Title: An Airborne Infrared Spectrometer for Solar Eclipse
Observations
Authors: DeLuca, E.; Samra, J.; Golub, L.; Cheimets, P.
Bibcode: 2016AGUFMSM51A2457D
Altcode:
The airborne infrared spectrometer (AIR-Spec) is an innovative
solar spectrometer that will observe the 2017 solar eclipse from
the NSF/NCAR High-Performance Instrumented Airborne Platform for
Environmental Research (HIAPER). AIR-Spec will image five infrared
coronal emission lines to determine whether they may be useful probes
of coronal magnetism. AIR-Spec consists of an optical system (feed
telescope and a cooled grating spectrometer and infrared detector) and
an image stabilization system, which uses a fast steering mirror to
correct the line-of-sight for platform perturbations. To ensure that
the instrument meets its research goals, both systems are undergoing
extensive performance modeling and testing. We will present preliminary
results of November flight tests of the image stabilization systems,
a critical component of the program.
Title: Tracking Sunspot Waves Across the Solar Disk using IRIS
Authors: Sager, H. A.; Madsen, C. A.; DeLuca, E.
Bibcode: 2016AGUFMSH21E2568S
Altcode:
Waves can be observed in the transition region and upper chromosphere of
sunspots. Two particular phenomena, running waves and umbral flashes,
can be seen in the 1400 Å and 2796 Å bandpasses, respectively,
on slit-jaw images from the Interface Region Imaging Spectrograph
(IRIS). How running waves propagate through the solar atmosphere is
still a topic of debate revolving around two theories. The trans-sunspot
theory explains that these waves propagate radially across the sunspot
from its center just as they appear visually. The upward propagating
theory illustrates that these waves are tied to the magnetic field
lines and are therefore slow magnetoacoustic waves, indicating that the
observed apparent motion of the waves is not real. Previous studies
focused on individual observations at a fixed viewing angle, leaving
the results susceptible to line-of-sight bias. To test for this bias, we
observed the leading sunspots of AR 11836 and AR 12546 as they traveled
from the disk center to the western limb. To assess the two theories,
we applied global wavelet analysis to our high-pass filtered slit-jaw
images and were able to find the spatial distribution of dominate wave
periods for both phenomena. We then compared the period distribution
to magnetic field line inclinations from the Helioseismic and Magnetic
Imager (HMI). From this, we find a clear correlation between magnetic
field line inclination and wave period as both increase outward from the
sunspot center. The period increases from 180 s from the sunspot center
to 240 s near the edge of the penumbra for all of our viewing angles,
nullifying the existence of a line-of-sight bias and lending credence
to the upward propagating theory. The importance of discovering how
these waves are moving through the solar atmosphere could provide a
mechanism for transporting local seismic energy from the photosphere
to the corona.
Title: An airborne infrared spectrometer for solar eclipse
observations
Authors: Samra, Jenna; Cheimets, Peter; DeLuca, Edward; Galeros,
John; Gauron, Thomas; Golub, Leon; Guth, Giora; Hertz, Edward; Judge,
Philip; Koutchmy, Serge; Marquez, Vanessa
Bibcode: 2016SPIE.9908E..5US
Altcode:
This paper presents the design of an innovative solar spectrometer
that will y on the NSF/NCAR Gulfstream V High-Performance Instrumented
Airborne Platform for Environmental Research (GV HIAPER) during the
2017 solar eclipse. The airborne infrared spectrometer (AIR-Spec) is
groundbreaking in two aspects: it will image infrared coronal emission
lines that have never been measured, and it will bring high resolution
imaging to GV HIAPER. The instrument development faces the challenges
of achieving adequate resolution and signal-to-noise ratio in a compact
package mounted to a noisy moving platform. To ensure that AIR-Spec
meets its research goals, the instrument is undergoing pre-flight
modeling and testing. The results are presented with reference to the
instrument requirements.
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: An Airborne Infrared Spectrometer for Solar Eclipse
Observations
Authors: Samra, Jenna; DeLuca, Edward; Golub, Leon; Cheimets, Peter;
Judge, Philip
Bibcode: 2016shin.confE.155S
Altcode:
The airborne infrared spectrometer (AIR-Spec) is an innovative
solar spectrometer that will observe the 2017 solar eclipse from
the NSF/NCAR High-Performance Instrumented Airborne Platform for
Environmental Research (HIAPER). AIR-Spec will image five infrared
coronal emission lines to determine whether they may be useful probes
of coronal magnetism. The solar magnetic field provides the free
energy that controls coronal heating, structure, and dynamics. Energy
stored in coronal magnetic fields is released in flares and coronal mass
ejections and ultimately drives space weather. Therefore, direct coronal
field measurements have significant potential to enhance understanding
of coronal dynamics and improve solar forecasting models. Of particular
interest are observations of field lines in the transitional region
between closed and open flux systems, providing important information
on the origin of the slow solar wind. While current instruments
routinely observe only the photospheric and chromospheric magnetic
fields, AIR-Spec will take a step toward the direct observation of
coronal fields by measuring plasma emission in the infrared at high
spatial and spectral resolution. During the total solar eclipse of
2017, AIR-Spec will search for five magnetically sensitive coronal
emission lines between 1.4 and 4 μm from the HIAPER Gulfstream V at
an altitude above 14.9 km. The instrument will measure emission line
intensity, width, and Doppler shift, map the spatial distribution of
infrared emitting plasma, and search for waves in the emission line
velocities. AIR-Spec consists of an optical system (feed telescope,
grating spectrometer, and infrared detector) and an image stabilization
system, which uses a fast steering mirror to correct the line-of-sight
for platform perturbations. To ensure that the instrument meets its
research goals, both systems are undergoing extensive performance
modeling and testing. These results are shown with reference to the
science requirements.
Title: Laboratory identification of MHD eruption criteria in the
solar corona
Authors: Myers, Clayton E.; Yamada, M.; Ji, H.; Yoo, J.; Jara-Almonte,
J.; Fox, W.; Savcheva, A.; DeLuca, E. E.
Bibcode: 2016shin.confE.161M
Altcode:
Ideal magnetohydrodynamic (MHD) instabilities such as the kink [1]
and torus [2] instabilities are believed to play an important role
in driving "storage-and-release" eruptions in the solar corona. These
instabilities act on long-lived, arched magnetic flux ropes that are
"line-tied" to the solar surface. In spite of numerous observational and
computational studies, the conditions under which these instabilities
produce an eruption remain a subject of intense debate. In this paper,
we use a line-tied, arched flux rope experiment to systematically study
storage-and-release eruption mechanisms in the laboratory [3]. Thin
in situ magnetic probes facilitate the study of both the equilibrium
and the stability of these laboratory flux ropes. In particular,
they permit the direct measurement of magnetic (J-B) forces, both
in equilibrium and during dynamic events. Regarding stability and
eruptions, two major results are reported here: First, a new stability
regime is identified where torus-unstable flux ropes fail to erupt. In
this "failed torus" regime, the flux rope is torus-unstable but
kink-stable. Under these conditions, a dynamic "toroidal field tension
force" surges in magnitude and prevents the flux rope from erupting
[4]. This dynamic tension force, which is missing from existing eruption
models, is generated by magnetic self-organization events within the
line-tied flux rope. Second, a clear torus instability threshold is
observed in the kink-unstable regime. This latter result, which is
consistent with existing theoretical [5] and numerical [6] results,
verifies the key role of the torus instability in driving flux rope
eruptions in the solar corona. [1] A. W. Hood & E. R. Priest,
Geophys. Astrophys. Fluid Dynamics 17, 297 (1981) [2] B. Kliem
& T. Torok, Phys. Rev. Lett. 96, 255002 (2006) [3] C. E. Myers,
Ph.D. Thesis, Princeton University (2015) [4] C. E. Myers et al.,
Nature 528, 526 (2015) [5] O. Olmedo & J. Zhang, Astrophys. J. 718,
433 (2010) [6] T. Torok & B. Kliem, Astrophys. J. 630, L97 (2005)
This research is supported by DoE Contract No. DE-AC02-09CH11466
and by the NSF/DoE Center for Magnetic Self-Organization (CMSO).
Title: Simulations of the Kelvin-Helmholtz instability driven by CMEs
Authors: Gomez, Daniel; DeLuca, Edward; Mininni, Pablo
Bibcode: 2016cosp...41E.698G
Altcode:
Recent AIA/SDO images remarkably show evidence of the development of
the Kelvin-Helmholtz (K-H) instability, as coronal mass ejections
(CMEs) expand in the corona. On the other hand, the non-thermal
broadening of spectral lines observed in the ambient corona strongly
suggest that this plasma is in a turbulent regime. Therefore, the
development of the K-H instability can significantly differ from the
one corresponding to a laminar medium. To study the evolution of the
K-H instability in a turbulent background, we perform three-dimensional
simulations of the magnetohydrodynamic equations. The instability is
driven by a velocity profile tangential to the CME-corona interface,
which we simulate through a hyperbolic tangent profile. The turbulent
background is obtained as a result of the application of a stationary
stirring force. As expected, we observe that the role of turbulence is
to attenuate the growth of the instability. We compute the instability
growth-rate for different values of the correlation length of the
turbulence. The fact that the K-H instability is observed, sets an upper
limit on the correlation length of the coronal background turbulence.
Title: Simulating Idealized Flux Ropes with the Flux Rope Insertion
Method: A Parameter Space Exploration of Currents and Topology
Authors: Savcheva, Antonia; Tassev, Svetlin; DeLuca, Edward E.;
Gibson, Sarah; Fan, Yuhong
Bibcode: 2016SPD....47.0330S
Altcode:
Knowledge of the 3D magnetic filed structure at the time of major
solar eruptions is vital to the understanding of the space weather
effects of these eruptions. Multiple data-constrained techniques that
reconstruct the 3D coronal field based on photospheric magnetograms have
been used to achieve this goal. In particular, we have used the flux
rope insertion method to obtain the coronal magnetic field of multiple
regions containing flux ropes or sheared arcades based on line-of-sight
magnetograms and X-ray and EUV observations of coronal loops. For the
purpose of developing statistical measures of the goodness of fit of
these models to the observations, here we present our modeling of flux
ropes based on synthetic magnetograms obtained from aFan & Gibson
emerging flux rope simulation. The goal is to study the effect of of
different input flux rope parameters on the geometry of currents,
field line connectivity, and topology, in a controled setting. For
this purpose we create a large grid of models with the flux rope
insertion method with different combinations of axial and poloidal
flux, which give us different morphology of the flux rope. We create
synthetic images of these flux ropes in AIA passbands with the FORWARD
forward-fitting code. The present parametric study will later be used
to get a better handle on the initial condition for magnetofrictional
and MHD simulations of observed regions containing flux ropes, such
as sigmoids and polar-crown filaments.
Title: An Airborne Infrared Spectrometer for Solar Eclipse
Observations
Authors: Samra, Jenna; DeLuca, Edward E.; Golub, Leon; Cheimets,
Peter; Philip, Judge
Bibcode: 2016SPD....4730106S
Altcode:
The airborne infrared spectrometer (AIR-Spec) is an innovative
solar spectrometer that will observe the 2017 solar eclipse from
the NSF/NCAR High-Performance Instrumented Airborne Platform for
Environmental Research (HIAPER). AIR-Spec will image five infrared
coronal emission lines to determine whether they may be useful probes
of coronal magnetism.The solar magnetic field provides the free energy
that controls coronal heating, structure, and dynamics. Energy stored in
coronal magnetic fields is released in flares and coronal mass ejections
and ultimately drives space weather. Therefore, direct coronal field
measurements have significant potential to enhance understanding of
coronal dynamics and improve solar forecasting models. Of particular
interest are observations of field lines in the transitional region
between closed and open flux systems, providing important information on
the origin of the slow solar wind.While current instruments routinely
observe only the photospheric and chromospheric magnetic fields,
AIR-Spec will take a step toward the direct observation of coronal
fields by measuring plasma emission in the infrared at high spatial and
spectral resolution. During the total solar eclipse of 2017, AIR-Spec
will observe five magnetically sensitive coronal emission lines between
1.4 and 4 µm from the HIAPER Gulfstream V at an altitude above 14.9
km. The instrument will measure emission line intensity, width, and
Doppler shift, map the spatial distribution of infrared emitting plasma,
and search for waves in the emission line velocities.AIR-Spec consists
of an optical system (feed telescope, grating spectrometer, and infrared
detector) and an image stabilization system, which uses a fast steering
mirror to correct the line-of-sight for platform perturbations. To
ensure that the instrument meets its research goals, both systems are
undergoing extensive performance modeling and testing. These results
are shown with reference to the science requirements.
Title: Is it Possible to Use the Green Coronal Line Instead of X rays
to Cancel an Effect of the Coronal Emissivity Deficit in Estimation of
the Prominence Total Mass from Decrease of the EUV-corona Intensities?
Authors: Schwartz, P.; Heinzel, P.; Jejčič, S.; Rybák, J.; Kotrč,
P.; Fárník, F.; Kupryakov, Yu. A.; Deluca, E. E.; Golub, L.; Jibben,
P. R.; Anzer, U.; Tlatov, A. G. .; Guseva, S. A.
Bibcode: 2016ASPC..504...89S
Altcode:
Total masses of six quiescent prominences observed from April through
June 2011 were estimated using multi-spectral observations (in EUV,
X-rays, Hα, and Ca <small>II</small> H). The method for
the total mass estimation is based on the fact that the intensity
of the EUV solar corona at wavelengths below 912 Å is reduced at a
prominence by the absorption in resonance continua (photoionisation)
of hydrogen and possibly by helium and subsequently an amount of
absorbed radiation is proportional to the column density of hydrogen
and helium plasma. Moreover, the deficit of the coronal emissivity in
volume occupied by the cool prominence plasma also contributes to the
intensity decrease. The observations in X-rays which are not absorbed
by the prominence plasma, allow us to separate these two mechanisms
from each other. The X-ray observations of XRT onboard the Hinode
satellite made with the Al-mesh focal filter were used because the
X-ray coronal radiation formed in plasma of temperatures of the order
of 106 K was registered and EUV spectral lines occurring in
the 193, 211 and 335 Å channels of the Atmospheric Imaging Assembly
of the Solar Dynamics Observatory satellite are also formed at such
temperatures. Unfortunately, the Al-mesh filter has a secondary peak
of the transmittance at around 171 Å which causes a contribution
from the EUV corona to the measured data of up to 11 % in the quiet
corona. Thus, absorption in prominence plasma influences XRT X-ray
data when using the Al-mesh filter. On the other hand, other X-ray XRT
filters are more sensitive to plasma of much higher temperatures (log
T of the order of 7), thus observations using these filters cannot
be used together with the AIA observations in the method for mass
estimations. This problem could be solved using observations in the
green coronal line instead of X-rays. Absorption of the green coronal
line by a prominence plasma is negligible and this line is formed at
temperatures of the order of 106 K. We compare values of
the total mass of the prominence observed on 20 October 2012 on the
SE limb estimated when using XRT X-ray observations and observations
in the green coronal line obtained at Kislovodsk Mountain Astronomical
Station of the Pulkovo observatory (Russia).
Title: Simulations of the Kelvin-Helmholtz Instability Driven by
Coronal Mass Ejections in the Turbulent Corona
Authors: Gómez, Daniel O.; DeLuca, Edward E.; Mininni, Pablo D.
Bibcode: 2016ApJ...818..126G
Altcode:
Recent high-resolution Atmospheric Imaging Assembly/Solar
Dynamics Observatory images show evidence of the development of the
Kelvin-Helmholtz (KH) instability, as coronal mass ejections (CMEs)
expand in the ambient corona. A large-scale magnetic field mostly
tangential to the interface is inferred, both on the CME and on the
background sides. However, the magnetic field component along the shear
flow is not strong enough to quench the instability. There is also
observational evidence that the ambient corona is in a turbulent regime,
and therefore the criteria for the development of the instability
are a priori expected to differ from the laminar case. To study the
evolution of the KH instability with a turbulent background, we perform
three-dimensional simulations of the incompressible magnetohydrodynamic
equations. The instability is driven by a velocity profile tangential to
the CME-corona interface, which we simulate through a hyperbolic tangent
profile. The turbulent background is generated by the application of a
stationary stirring force. We compute the instability growth rate for
different values of the turbulence intensity, and find that the role of
turbulence is to attenuate the growth. The fact that KH instability is
observed sets an upper limit on the correlation length of the coronal
background turbulence.
Title: The Relation between Solar Eruption Topologies and Observed
Flare Features. II. Dynamical Evolution
Authors: Savcheva, A.; Pariat, E.; McKillop, S.; McCauley, P.; Hanson,
E.; Su, Y.; DeLuca, E. E.
Bibcode: 2016ApJ...817...43S
Altcode:
A long-established goal of solar physics is to build understanding
of solar eruptions and develop flare and coronal mass ejection (CME)
forecasting models. In this paper, we continue our investigation of
nonlinear forces free field (NLFFF) models by comparing topological
properties of the solutions to the evolution of the flare ribbons. In
particular, we show that data-constrained NLFFF models of three erupting
sigmoid regions (SOL2010-04-08, SOL2010-08-07, and SOL2012-05-12) built
to reproduce the active region magnetic field in the pre-flare state can
be rendered unstable and the subsequent sequence of unstable solutions
produces quasi-separatrix layers that match the flare ribbon evolution
as observed by SDO/AIA. We begin with a best-fit equilibrium model for
the pre-flare active region. We then add axial flux to the flux rope
in the model to move it across the stability boundary. At this point,
the magnetofrictional code no longer converges to an equilibrium
solution. The flux rope rises as the solutions are iterated. We
interpret the sequence of magnetofrictional steps as an evolution of
the active region as the flare/CME begins. The magnetic field solutions
at different steps are compared with the flare ribbons. The results are
fully consistent with the three-dimensional extension of the standard
flare/CME model. Our ability to capture essential topological features
of flaring active regions with a non-dynamic magnetofrictional code
strongly suggests that the pre-flare, large-scale topological structures
are preserved as the flux rope becomes unstable and lifts off.
Title: The Coronal Solar Magnetism Observatory
Authors: Tomczyk, S.; Landi, E.; Zhang, J.; Lin, H.; DeLuca, E. E.
Bibcode: 2015AGUFMSH43B2460T
Altcode:
Measurements of coronal and chromospheric magnetic fields are
arguably the most important observables required for advances in
our understanding of the processes responsible for coronal heating,
coronal dynamics and the generation of space weather that affects
communications, GPS systems, space flight, and power transmission. The
Coronal Solar Magnetism Observatory (COSMO) is a proposed ground-based
suite of instruments designed for routine study of coronal and
chromospheric magnetic fields and their environment, and to understand
the formation of coronal mass ejections (CME) and their relation to
other forms of solar activity. This new facility will be operated by
the High Altitude Observatory of the National Center for Atmospheric
Research (HAO/NCAR) with partners at the University of Michigan, the
University of Hawaii and George Mason University in support of the
solar and heliospheric community. It will replace the current NCAR
Mauna Loa Solar Observatory (http://mlso.hao.ucar.edu). COSMO will
enhance the value of existing and new observatories on the ground and
in space by providing unique and crucial observations of the global
coronal and chromospheric magnetic field and its evolution. The design
and current status of the COSMO will be reviewed.
Title: Observations of Small-scale IRIS Bombs (Reconnection Events)
in an Evolving Active Region
Authors: Madsen, C. A.; Tian, H.; DeLuca, E. E.
Bibcode: 2015AGUFMSH31B2414M
Altcode:
We present the first Interface Region Imaging Spectrograph (IRIS)
observations of small-scale bombs evolving with their host active
region. Bombs appear most clearly in the IRIS 1330 Å and 1400 Å
slit-jaw images as small (~1 arcsec), compact, intense brightenings at
transition region temperatures. Their NUV/FUV emission spectra exhibit
dramatic line splitting and strong absorption features indicative of
bidirectional flows from magnetic reconnection embedded deep within the
cool lower solar atmosphere. The bombs may contribute significantly
to the heating of the solar atmosphere in active regions; however,
it's unclear how prevalent the bombs are throughout the lifetime of an
active region. Using a semi-automated detection method, we locate bombs
within AR 11850 over the course of four observations from 06:00 UT on
September 25, 2013 until 11:30 UT the next day. The active region is
first observed in an emerging phase and rapidly grows into a mature
active region with well-developed sunspots. The bomb occurrence rate
drops dramatically as the active region fully emerges. We also find
that the bombs fall into two distinct populations: one appears largely
during active region emergence and contains a majority of the bombs,
while the other population is present regardless of active region
age. The first population of bombs is typically found embedded in the
low-lying loops prominent in the young active region. Furthermore,
we use Solar Dynamics Observatory/Helioseismic and Magnetic Imager
(SDO/HMI) line-of-sight magnetograms to show that the bombs associated
with the first population occur at the boundaries between the upward
and downward flux of small, isolated bipolar regions. These regions
dissipate as the active region emerges and reconfigures its magnetic
field into two large network patches of upward and downward flux with a
clear inversion line. The second, smaller population of bombs usually
occurs far from the active region loop structures in the plage and
sunspot penumbrae. They are associated with the boundaries between
strong upward or downward flux and regions where the magnetic field
is perpendicular to the line of sight.
Title: Airborne Infrared Spectrograph for Eclipse Observations
Authors: Golub, L.; Cheimets, P.; DeLuca, E. E.; Samra, J.; Judge,
P. G.
Bibcode: 2015AGUFMSH51C2454G
Altcode:
Direct measurements of the coronal magnetic field have significant
potential to enhance our understanding of coronal dynamics, and improve
forecasting models. Of particular interest are observations of coronal
field lines in the Transition Corona, the transitional region between
closed and open flux systems, providing important information on
eruptive instabilities and on the origin of the slow solar wind. While
current instruments routinely observe the photospheric and chromospheric
magnetic fields, the proposed airborne spectrometer will take a step
toward the direct observation of coronal fields by measuring plasma
emission in the infrared at high spatial and spectral resolution. The
targeted lines are five forbidden magnetic dipole transitions between
1.4 and 4 um. The airborne system will consist of a telescope,
grating spectrometer and pointing/stabilization system to be flown
on the NSF/NCAR High-performance Instrumented Airborne Platform for
Environmental Research (HIAPER) during the 21 August 2017 total solar
eclipse. We will discuss the scientific objectives of the 2017 flight,
describe details of the instrument design, and present the observing
program for the eclipse.
Title: A dynamic magnetic tension force as the cause of failed
solar eruptions
Authors: Myers, Clayton E.; Yamada, Masaaki; Ji, Hantao; Yoo, Jongsoo;
Fox, William; Jara-Almonte, Jonathan; Savcheva, Antonia; Deluca,
Edward E.
Bibcode: 2015Natur.528..526M
Altcode:
Coronal mass ejections are solar eruptions driven by a sudden release
of magnetic energy stored in the Sun’s corona. In many cases,
this magnetic energy is stored in long-lived, arched structures
called magnetic flux ropes. When a flux rope destabilizes, it can
either erupt and produce a coronal mass ejection or fail and collapse
back towards the Sun. The prevailing belief is that the outcome of a
given event is determined by a magnetohydrodynamic force imbalance
called the torus instability. This belief is challenged, however,
by observations indicating that torus-unstable flux ropes sometimes
fail to erupt. This contradiction has not yet been resolved because
of a lack of coronal magnetic field measurements and the limitations
of idealized numerical modelling. Here we report the results of
a laboratory experiment that reveal a previously unknown eruption
criterion below which torus-unstable flux ropes fail to erupt. We find
that such ‘failed torus’ events occur when the guide magnetic field
(that is, the ambient field that runs toroidally along the flux rope)
is strong enough to prevent the flux rope from kinking. Under these
conditions, the guide field interacts with electric currents in the
flux rope to produce a dynamic toroidal field tension force that halts
the eruption. This magnetic tension force is missing from existing
eruption models, which is why such models cannot explain or predict
failed torus events.
Title: 3D Model of Slip-Running Reconnection on Solar Sigmoidal
Regions
Authors: Douglas, B.; Savcheva, A. S.; DeLuca, E. E.
Bibcode: 2015AGUFMSH43A2422D
Altcode:
The structure of energy storing magnetic field lines on the Sun is
very twisted and contorted. Some of the twist arises from photospheric
foot point motion and some is due to currents carried into the corona
as fields emerge. The stability of a region depends on both the energy
stored (so-called "free" energy) and on the structure of the surrounding
nearly potential fields. Free energy is usually contained in these
S-shaped regions called sigmoids on the solar corona. The only way to
reach lower energy state is to release this free energy, by changing
its connectivity. This change in connectivity leads to flares and
coronal mass ejections (CMEs) that can affect environments of nearby
planets. For this project, we focus on a special kind of connectivity
change called slip-running reconnection to create 3D numerical models
of flare-producing magnetic fields. By comparing these numerical models
to observational data from Atmospheric Imaging Assembly (AIA), we will
be able to better explain the evolution of sigmoidal flares from active
regions. We are studying a flare from Dudik et al 2014 paper (2012 July
12), and a flare from 2015 June 14. Using the Coronal Modeling System
(CMS) software, we read the photospheric magnetogram for the specified
date and time, compute the potential field, setup the 3D flux rope
path, and then relax this flux rope over 60,000 iterations to create
a nonlinear force-free field (NLFFF). Using these relaxed models we
find the best-fit loops surrounding the flux rope. We then compare
these models to the observations in AIA. We compare the magnetic field
structure in our models with the observed slipping. For regions near
our inserted flux rope, our models successfully correlate with this
observation. Further modeling is required, but these initial results
suggest that NLFFF modeling may be able to capture realistic 3-D
magnetic structures associated with slipping reconnection.
Title: Laboratory Identification of MHD Eruption Criteria in the
Solar Corona
Authors: Yamada, M.; Myers, C. E.; Ji, H.; Yoo, J.; Fox, W. R., II;
Jara-Almonte, J.; Savcheva, A. S.; DeLuca, E. E.
Bibcode: 2015AGUFMSH13A2434Y
Altcode:
Ideal magnetohydrodynamic (MHD) instabilities such as the kink [1]
and torus [2] instabilities are believed to play an important role
in driving "storage-and-release" eruptions in the solar corona. These
instabilities act on long-lived, arched magnetic flux ropes that are
"line-tied" to the solar surface. In spite of numerous observational and
computational studies, the conditions under which these instabilities
produce an eruption remain a subject of intense debate. In this
paper, we use a line-tied, arched flux rope experiment to study
storage-and-release eruptions in the laboratory [3]. An in situ array
of miniature magnetic probes is used to assess the equilibrium and
stability of the laboratory flux ropes. Two major results are reported
here: First, a new stability regime is identified where torus-unstable
flux ropes fail to erupt. In this "failed torus" regime, the flux rope
is torus-unstable but kink-stable. Under these conditions, a dynamic
"toroidal field tension force" surges in magnitude and causes the flux
rope to contract. This tension force, which is missing from existing
eruption models, is the J×B force between self-generated poloidal
currents in the flux rope and the toroidal (guide) component of the
vacuum field. Secondly, a clear torus instability threshold is observed
in the kink-unstable regime. This latter result, which is consistent
with existing theoretical [4] and numerical [5] findings, verifies the
key role of the torus instability in driving some solar eruptions. This
research is supported by DoE Contract No. DE-AC02-09CH11466 and by
the NSF/DoE Center for Magnetic Self-Organization (CMSO). [1] Hood
& Priest, Geophys. Astrophys. Fluid Dynamics 17, 297 (1981)
[2] Kliem & Török, Phys. Rev. Lett. 96, 255002 (2006) [3]
Myers, Ph.D. Thesis, Princeton University (2015) [4] Olmedo &
Zhang, Astrophys. J. 718, 433 (2010) [5] Török & Kliem,
Astrophys. J. 630, L97 (2005)
Title: Towards a Data-Optimized Coronal Magnetic Field Model (DOC-FM):
Simulating Flux Ropes with the Flux Rope Insertion Method
Authors: Dalmasse, K.; DeLuca, E. E.; Savcheva, A. S.; Gibson, S. E.;
Fan, Y.
Bibcode: 2015AGUFMSH51B2444D
Altcode:
Knowledge of the 3D magnetic filed structure at the time of major solar
eruptions is vital or understanding of the space weather effects of
these eruptions. Multiple data-constrained techniques that reconstruct
the 3D coronal field based on photospheric magnetograms have been
used to achieve this goal. In particular, we have used the flux rope
insertion method to obtain the coronal magnetic field of multiple
regions containing flux ropes or sheared arcades based on line-of-sight
magnetograms and X-ray and EUV observations of coronal loops. For the
purpose of developing statistical measures of the goodness of fit of
these models to the observations, here we present our modeling of flux
ropes based on synthetic magnetograms obtained from Fan & Gibson
emerging flux rope simulation. The goal is to reproduce the flux rope
structure from a given time step of the MHD simulations based only
on the photospheric magnetogram and synthetic forward modeled coronal
emission obtained from the same step of the MHD simulation. For this
purpose we create a large grid of models with the flux rope insertion
method with different combinations of axial and poloidal flux, which
give us different morphology of the flux rope. Then we compare the
synthetic coronal emission with the shape of the current distribution
and field lines from the models to come up with a best fit. This fit
is then tested using the statistical methods developed by our team.
Title: The Relation between Solar Eruption Topologies and Observed
Flare Features. I. Flare Ribbons
Authors: Savcheva, A.; Pariat, E.; McKillop, S.; McCauley, P.; Hanson,
E.; Su, Y.; Werner, E.; DeLuca, E. E.
Bibcode: 2015ApJ...810...96S
Altcode: 2015arXiv150603452S
In this paper we present a topological magnetic field investigation
of seven two-ribbon flares in sigmoidal active regions observed with
Hinode, STEREO, and Solar Dynamics Observatory. We first derive the
3D coronal magnetic field structure of all regions using marginally
unstable 3D coronal magnetic field models created with the flux rope
insertion method. The unstable models have been shown to be a good
model of the flaring magnetic field configurations. Regions are selected
based on their pre-flare configurations along with the appearance and
observational coverage of flare ribbons, and the model is constrained
using pre-flare features observed in extreme ultraviolet and X-ray
passbands. We perform a topology analysis of the models by computing the
squashing factor, Q, in order to determine the locations of prominent
quasi-separatrix layers (QSLs). QSLs from these maps are compared to
flare ribbons at their full extents. We show that in all cases the
straight segments of the two J-shaped ribbons are matched very well by
the flux-rope-related QSLs, and the matches to the hooked segments are
less consistent but still good for most cases. In addition, we show that
these QSLs overlay ridges in the electric current density maps. This
study is the largest sample of regions with QSLs derived from 3D coronal
magnetic field models, and it shows that the magnetofrictional modeling
technique that we employ gives a very good representation of flaring
regions, with the power to predict flare ribbon locations in the event
of a flare following the time of the model.
Title: Self-organized braiding in solar coronal loops
Authors: Berger, M. A.; Asgari-Targhi, M.; Deluca, E. E.
Bibcode: 2015JPlPh..81d3904B
Altcode:
In this paper, we investigate the evolution of braided solar
coronal loops. We assume that coronal loops consist of several
internal strands which twist and braid about each other. Reconnection
between the strands leads to small flares and heating of the loop to
x-ray temperatures. Using a method of generating and releasing braid
structure similar to a forest fire model, we show that the reconnected
field lines evolve to a self-organised critical state. In this state,
the frequency distributions of coherent braid sequences as well as
flare energies follow power law distributions. We demonstrate how the
presence of net helicity in the loop alters the distribution laws.
Title: Investigation of Solar Eruptive Prominences
Authors: Su, Yingna; McCauley, Patrick; van Ballegooijen, Adriaan;
Ji, Haisheng; Reeves, Katharine; DeLuca, Edward
Bibcode: 2015IAUGA..2256101S
Altcode:
At first, we will present an investigation of the polar crown
prominence that erupted on 2012 March 12. This prominence is observed
at the southeast limb by SDO/AIA (end-on view) and displays a quasi
vertical-thread structure. Bright U-shape (horn-like) structure is
observed surrounding the upper portion of the prominence (171 Angstrom)
before the eruption and becomes more prominent during the eruption. When
viewed on the disk, STEREO-B shows that this long prominence is composed
of a series of vertical threads and displays a half loop-like structure
during the eruption. We focus on the magnetic support of the prominence
by studying the structure and dynamics of the prominence before
and during the eruption using observations from SDO and STEREO. We
construct a series of magnetic field models (including sheared arcade
model, twisted flux rope model, and model with HFT), then compare
with observations. Various observational characteristics appear to
support the twisted flux rope model. Our study suggests that the flux
rope supporting the prominence enters the regime of torus instability
at the onset of the fast rise phase, and signature of reconnection
appears about one hour later. In the second part, we will present
a statistical study on the kinematics of limb eruptive prominences
observed by SDO/AIA. A brief introduction on an online catalog of
prominence eruptions observed by SDO/AIA will also be presented.
Title: What is the best indicator of active region stability? Topology
not free energy or relative helicity!
Authors: DeLuca, Edward E.; Savcheva, Antonia
Bibcode: 2015shin.confE..28D
Altcode:
The determination of magnetic free energy and relative helicity
in active region magnetic field models is strongly model- and
method-dependent. Even if more accurate and complete magnetic field
measurements are made and the quantities can be determined with higher
confidence and precision, the limiting value that would
Title: The Relation between CME Topologies and Observed Flare Features
Authors: Savcheva, Antonia Stefanova; Pariat, E.; MaKillop, S.;
McCauley, P.; Hanson, E.; Werner, E.; Su, Y.; DeLuca, E.
Bibcode: 2015shin.confE...6S
Altcode:
A long established goal of solar physics is to build physics-based
flare and CME forecasting models. This study, building on the recent
successes in non-linear forces free field (NLFFF) modeling and detailed
numerical simulations, brings us closer to that goal. We show that
data-constrained NLFFF models built to reproduce the active region
magnetic field in the pre-flare state can be rendered unstable and
the sequence of unstable solutions produce quasi-separatrix layers
(QSLs) that reproduce the observed flare ribbons. The results are fully
consistant with the 3D extension of the standard flare/CME model. Our
ability to capture essential topological features of flaring active
regions with non-dynamic magneto-frictional code strongly suggests
that the pre-flare, large scale topological structures are preserved
as the flux rope becomes unstable and lifts off.
Title: Magnetic Structure and Dynamics of the Erupting Solar Polar
Crown Prominence on 2012 March 12
Authors: Su, Yingna; van Ballegooijen, Adriaan; McCauley, Patrick;
Ji, Haisheng; Reeves, Katharine K.; DeLuca, Edward E.
Bibcode: 2015ApJ...807..144S
Altcode: 2015arXiv150506826S
We present an investigation of the polar crown prominence that erupted
on 2012 March 12. This prominence is observed at the southeast limb
by the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly
(AIA; end-on view) and displays a quasi-vertical thread structure. A
bright U-shaped or horn-like structure is observed surrounding the upper
portion of the prominence at 171 Å before the eruption and becomes more
prominent during the eruption. The disk view of {STEREO}\_B shows that
this long prominence is composed of a series of vertical threads and
displays a half-loop-like structure during the eruption. We focus on
the magnetic support of the prominence vertical threads by studying the
structure and dynamics of the prominence before and during the eruption
using observations from SDO and STEREO_B. We also construct a series of
magnetic field models (sheared arcade model, twisted flux rope model,
and unstable model with hyperbolic flux tube). Various observational
characteristics appear to be in favor of the twisted flux rope model. We
find that the flux rope supporting the prominence enters the regime of
torus instability at the onset of the fast-rise phase, and signatures of
reconnection (posteruption arcade, new U-shaped structure, rising blobs)
appear about one hour later. During the eruption, AIA observes dark
ribbons seen in absorption at 171 Å corresponding to the bright ribbons
shown at 304 Å, which might be caused by the erupting filament material
falling back along the newly reconfigured magnetic fields. Brightenings
at the inner edge of the erupting prominence arcade are also observed
in all AIA EUV channels, which might be caused by the heating due to
energy released from reconnection below the rising prominence.
Title: The Minimum of Solar Cycle 23: As Deep as It Could Be?
Authors: Muñoz-Jaramillo, Andrés; Senkpeil, Ryan R.; Longcope,
Dana W.; Tlatov, Andrey G.; Pevtsov, Alexei A.; Balmaceda, Laura A.;
DeLuca, Edward E.; Martens, Petrus C. H.
Bibcode: 2015ApJ...804...68M
Altcode: 2015arXiv150801222M
In this work we introduce a new way of binning sunspot group data
with the purpose of better understanding the impact of the solar
cycle on sunspot properties and how this defined the characteristics
of the extended minimum of cycle 23. Our approach assumes that
the statistical properties of sunspots are completely determined
by the strength of the underlying large-scale field and have no
additional time dependencies. We use the amplitude of the cycle
at any given moment (something we refer to as activity level) as a
proxy for the strength of this deep-seated magnetic field. We find
that the sunspot size distribution is composed of two populations:
one population of groups and active regions and a second population
of pores and ephemeral regions. When fits are performed at periods
of different activity level, only the statistical properties of the
former population, the active regions, are found to vary. Finally,
we study the relative contribution of each component (small-scale
versus large-scale) to solar magnetism. We find that when hemispheres
are treated separately, almost every one of the past 12 solar minima
reaches a point where the main contribution to magnetism comes from
the small-scale component. However, due to asymmetries in cycle phase,
this state is very rarely reached by both hemispheres at the same
time. From this we infer that even though each hemisphere did reach
the magnetic baseline, from a heliospheric point of view the minimum
of cycle 23 was not as deep as it could have been.
Title: The Minimum of Solar Cycle 23: As Deep as It Could Be?
Authors: Munoz-Jaramillo, Andres; Senkpeil, Ryan; Longcope, Dana;
Tlatov, Andrey; Pevtsov, Alexei A.; Balmaceda, Laura; DeLuca, Edward
E.; Martens, Petrus C.
Bibcode: 2015TESS....130803M
Altcode:
After a lull lasting more than 60 years of seemly uniform solar minima,
the solar minimum of solar cycle 23 came as a great surprise due to its
depth, duration, and record lows in a wide variety of solar activity
indices and solar wind properties. One of the consequence of such an
event is the revival of the interest in extreme minima, grand minima,
and the identification of a solar basal state of minimum magnetic
activity.In this presentation we will discuss a new way of binning
sunspot group data, with the purpose of better understanding the impact
of the solar cycle on sunspot properties, and how this defined the
characteristics of the extended minimum of cycle 23. Our main result
is centered around the fact that the sunspot size distribution is
composed of two populations, a population of groups and active regions,
and second of pores and ephemeral regions. We find that only the
properties of the former population, the active regions, is found to
vary with the solar cycle, while the propeties of pores and ephemeral
regions does not.Taking advantage of our statistical characterization
we probe the question of the solar baseline magnetism. We find that,
when hemispheres are treated separately, almost every one of the past
12 solar minima reaches such a point. However, due to asymmetries in
cycle phase, the basal state is very rarely reached by both hemispheres
at the same time. From this we infer that, even though each hemisphere
did reach the magnetic baseline, from a heliospheric point of view
the minimum of cycle 23 was not as deep as it could have been.
Title: Investigation on Eruptive Prominences Observed by SDO
Authors: Su, Yingna; McCauley, Patrick; van Ballegooijen, Adriaan;
Ji, Haisheng; Reeves, Katharine; DeLuca, Edward
Bibcode: 2015TESS....121203S
Altcode:
We will present an investigation of the polar crown prominence that
erupted on 2012 March 12. This prominence is observed at the southeast
limb by SDO/AIA (end-on view) and displays a quasi vertical-thread
structure. Bright U-shape (horn-like) structure is observed surrounding
the upper portion of the prominence (171 Angstrom) before the eruption
and becomes more prominent during the eruption. When viewed on the
disk, STEREO-B shows that this long prominence is composed of a series
of vertical threads and displays a half loop-like structure during
the eruption. We focus on the magnetic support of the prominence
by studying the structure and dynamics of the prominence before and
during the eruption using observations from SDO and STEREO. During
the eruption, AIA observes dark ribbons seen in absorption at 171
Angstrom in corresponding to the bright ribbons at 304 Angstrom. We
construct a series of magnetic field models (including sheared arcade
model, twisted flux rope model, and model with HFT), then compare
with observations. Various observational characteristics appear to
support the twisted flux rope model. Our study suggests that the flux
rope supporting the prominence enters the regime of torus instability
at the onset of the fast rise phase, and evidence of reconnection
(post-eruption arcade, new U-shape Structure, rising blobs) appears
about one hour later. We will also present a statistical study on the
kinematics of limb eruptive prominences observed by SDO/AIA. A brief
introduction on an online catalog of prominence eruptions observed by
SDO/AIA will also be presented.
Title: Small-scale and Global Dynamos and the Area and Flux
Distributions of Active Regions, Sunspot Groups, and Sunspots:
A Multi-database Study
Authors: Muñoz-Jaramillo, Andrés; Senkpeil, Ryan R.; Windmueller,
John C.; Amouzou, Ernest C.; Longcope, Dana W.; Tlatov, Andrey G.;
Nagovitsyn, Yury A.; Pevtsov, Alexei A.; Chapman, Gary A.; Cookson,
Angela M.; Yeates, Anthony R.; Watson, Fraser T.; Balmaceda, Laura A.;
DeLuca, Edward E.; Martens, Petrus C. H.
Bibcode: 2015ApJ...800...48M
Altcode: 2014arXiv1410.6281M
In this work, we take advantage of 11 different sunspot group,
sunspot, and active region databases to characterize the area
and flux distributions of photospheric magnetic structures. We
find that, when taken separately, different databases are better
fitted by different distributions (as has been reported previously
in the literature). However, we find that all our databases can be
reconciled by the simple application of a proportionality constant,
and that, in reality, different databases are sampling different
parts of a composite distribution. This composite distribution
is made up by linear combination of Weibull and log-normal
distributions—where a pure Weibull (log-normal) characterizes the
distribution of structures with fluxes below (above) 1021Mx
(1022Mx). Additionally, we demonstrate that the Weibull
distribution shows the expected linear behavior of a power-law
distribution (when extended to smaller fluxes), making our results
compatible with the results of Parnell et al. We propose that this is
evidence of two separate mechanisms giving rise to visible structures
on the photosphere: one directly connected to the global component of
the dynamo (and the generation of bipolar active regions), and the other
with the small-scale component of the dynamo (and the fragmentation of
magnetic structures due to their interaction with turbulent convection).
Title: Observations of Umbral Flashes and Running Sunspot Waves with
the Interface Region Imaging Spectrograph
Authors: Madsen, Chad A.; Tian, Hui; DeLuca, Edward E.
Bibcode: 2015ApJ...800..129M
Altcode:
We present simultaneous, high-resolution, multi-temperature observations
of running waves and umbral flashes in a sunspot with the Interface
Region Imaging Spectrograph. We analyze intensity variations in
slit-jaw images to investigate the relationship between running
waves in the 1400 Å (Si IV/transition region) passband and umbral
flashes in the 2796 Å (Mg II/chromosphere) passband. Using global
wavelet analysis, we find that the dominant wave periods increase
from approximately 150 s near the sunspot center to about 300 s in
the penumbra in both passbands. This coincides extremely well with
the radially increasing inclination of magnetic field lines observed
with Solar Dynamics Observatory/Helioseismic and Magnetic Imager,
suggesting that the waves are propagating vertically along the inclined
field lines. Furthermore, apparent horizontal velocities for running
waves decrease from about 12 km s-1 in the umbra to about
4 km s-1 in the penumbra which is predicted by the same
inclined field geometry. Finally, we find that umbral flashes lead
running waves in both the spatial and temporal domains. The former
result is attributable to the inclined field geometry; however, the
geometry does not predict the radially increasing time lag which is
likely due to the opacity difference between the emission lines that
dominate the two passbands. These results suggest that running waves
and umbral flashes both originate from photospheric p-mode oscillations
and are manifestations of upward-propagating slow magnetoacoustic modes
at different altitudes and temperatures. The apparent trans-sunspot
propagation of running waves is not real but rather an image of these
upward-propagating modes traveling along field lines of radially
increasing inclination.
Title: Total mass of six quiescent prominences estimated from their
multi-spectral observations
Authors: Schwartz, P.; Heinzel, P.; Kotrč, P.; Fárník, F.;
Kupryakov, Yu. A.; DeLuca, E. E.; Golub, L.
Bibcode: 2015A&A...574A..62S
Altcode:
Context. Total masses of six solar prominences were estimated using
prominence multi-spectral observations (in EUV, X-rays, Hα, and Ca
ii H). The observations were made during the observing campaign from
April through June 2011.
Aims: The aim of the work was to apply
a complex method for the prominence mass estimations that can be used
later for other prominences observed during the observing campaign.
Methods: Our method is based on the fact that intensity of the EUV
solar corona at wavelengths below 912 Å is reduced by the absorption
in resonance continua of hydrogen and helium (photoionisation) and at
the same time also by a deficit of the coronal emissivity in volume
occupied by the cool prominence plasma. Both mechanisms contribute to
intensity decrease simultaneously. The observations in X-rays allow us
to separate these mechanisms from each other. Coronal emission behind a
prominence is not estimated by any temporal or spatial interpolation,
but by using a new method based on comparing the ratio of the optical
thickness at 193 Å and 211 Å determined from the observations
with the theoretical ratio.
Results: Values of the total mass
estimated for six prominences are between 2.9 × 1011 and
1.7 × 1012 kg. The column density of hydrogen is of the
order of 1018-1019 cm-2. Our results
agree with results of other authors.
Conclusions: The method
is now ready to be used for all 30 prominences observed during the
campaign. Then in the near future it will be possible to obtain a
statistics of the total mass of quiescent solar prominences.
Title: Toward the Direct Measurement of Coronal Magnetic Fields:
An Airborne Infrared Spectrometer for Eclipse Observations
Authors: Samra, J.; DeLuca, E. E.; Golub, L.; Cheimets, P.
Bibcode: 2014AGUFMSH53B4214S
Altcode:
The solar magnetic field enables the heating of the corona and
provides its underlying structure. Energy stored in coronal magnetic
fields is released in flares and coronal mass ejections (CME) and
provides the ultimate source of energy for space weather. Therefore,
direct measurements of the coronal magnetic field have significant
potential to enhance understanding of coronal dynamics and improve
solar forecasting models. Of particular interest are observations
of coronal field lines in the transitional region between closed and
open flux systems, providing important information on the origin of
the slow solar wind. While current instruments routinely observe only
the photospheric and chromospheric magnetic fields, a proposed airborne
spectrometer will take a step toward the direct observation of coronal
fields by measuring plasma emission in the infrared at high spatial
and spectral resolution. The targeted lines are four forbidden magnetic
dipole transitions between 2 and 4 μm. The airborne system will consist
of a telescope, grating spectrometer, and pointing/stabilization
system to be flown on the NSF/NCAR High-performance Instrumented
Airborne Platform for Environmental Research (HIAPER) during the
August 2017 total solar eclipse. The project incorporates several
optical engineering challenges, centered around maintaining adequate
spectral and spatial resolution in a compact and inexpensive package
and on a moving platform. Design studies are currently underway to
examine the tradeoffs between various optical geometries and control
strategies for the pointing/stabilization system. The results will
be presented and interpreted in terms of the consequences for the
scientific questions. In addition, results from a laboratory prototype
and simulations of the final system will be presented.
Title: Prevalence of Micro-Jets from the Network Structures of the
Solar Transition Region and Chromosphere
Authors: DeLuca, E. E.; Tian, H.; Cranmer, S. R.; Reeves, K.; Miralles,
M. P.; McCauley, P.; McKillop, S.
Bibcode: 2014AGUFMSH51C4180D
Altcode:
IRIS observations in the 1330Å, 1400Å and 2796Å passbands have
revealed numerous small-scale jet-like features with speeds of ~80-250
km/s from the chromospheric network. These network jets occur in
both the quiet Sun and coronal holes. Their widths are often ~300
km or less. Many of these jets show up as elongated features with
enhanced line width in maps obtained with transition region (TR)
lines, suggesting that these jets reach at least TR temperatures and
they constitute an important element of TR structures. The ubiquitous
presence of these high-reaching (often >10 Mm) jets also suggests
that they may play a crucial role in the mass and energy budgets
of the corona and solar wind. The generation of these jets in the
network and the accompanying Alfven waves is also consistent with
the "magnetic furnace model" of solar wind proposed by Axford &
McKenzie (1992). The large speeds (greater than sound speed) suggest
that the Lorentz force (perhaps related to reconnection) must play
an important role in the generation and propagation of the network
jets. We believe that many network jets are the on-disk counterparts
and TR manifestation of type-II spicules.
Title: A Personal View of Coronal Heating: Progress and Rabbit Holes
Authors: DeLuca, E. E.
Bibcode: 2014AGUFMSH12A..01D
Altcode:
Over the past few years we have seen great progress in our understanding
of the processes that provide mass and energy into the corona. Research
in atomic physics and new computational approaches, combined with an
impressive set of observations, allow us to test detailed physical
models against spatially, spectrally and temporally constrained
observations. Our understanding of physics of low beta plasmas are
increasing dramatically. In addition, we have explored some elaborate
rabbit holes in great details. A personal view of how we have gotten
here and where we should be going will be presented.
Title: Magnetic Field Modeling of Complex, Flare Productive Active
Regions
Authors: Millholland, S. C.; Savcheva, A. S.; DeLuca, E. E.
Bibcode: 2014AGUFMSH13A4079M
Altcode:
We present models and analysis of the magnetic field structure of three
sigmoidal active regions (ARs). Sigmoids, forward or backward S-shaped
EUV and X-ray emissions in the corona, are relevant as predictors of
eruptive events such as flares and Coronal Mass Ejections. The regions
were modeled using the Flux Rope Insertion Method, in which flux ropes,
held in equilibrium by an overlying potential arcade, represent the
sigmoids. The flux rope paths were inserted into a potential field
following the filaments observed in 304Å. The models were then relaxed
into a nonlinear force free (NLFFF) state using a magnetofrictional
relaxation process. The first region studied is NOAA AR 12017, which
produced an X1.0 flare at 2014/03/29 17:35. The second is NOAA AR 11283,
which erupted with an X2.1 flare at 2011/09/06 22:12. For these regions,
we show detailed comparisons of Quasi-Separatrix Layer (QSL) maps and
observed flare ribbons. The slow evolution of an unstable solution at
the time of the eruption produces a set of QSL solutions. Comparison
of the photospheric mapping of the QSL with the flare ribbons will be a
good measure of how well we have captured the magnetic structure of the
particle acceleration region with our simple NLFFF models. The third
is NOAA AR 11093. This region was a double decker filament composed
of two branches over the same polarity inversion line. At 2010/08/07
17:55, the upper filament erupted with an M1.0 flare. This is the first
time a double decker flux rope region has been modeled using these
techniques. We show the interaction of the two inserted flux ropes and
the evolution of the region through a series of NLFFF solutions to the
evolving photospheric magnetic field. This work has been funded by the
NSF-REU solar physics program at Smithsonian Astrophysical Observatory,
grant number AGS-1263241.
Title: Investigating Alfven Wave Turbulence in Chromosphere and
Corona Using Extreme Ultraviolet Imaging Spectrometer (EIS)
Authors: Asgari-Targhi, M.; Imada, S.; DeLuca, E. E.
Bibcode: 2014AGUFMSH53D..07A
Altcode:
The solar corona is known to be very dynamic. Mass motions due to
Alfven wave turbulence are one of the main causes of plasma flows
within the coronal loops. Using observations from EIS we analyze the
structure of active region loops observed on 2012 September 7. We
study the spectral line profiles of Fe XII, Fe XIII, Fe XV and Fe
XVI and compare the non-thermal line broadening from this region to
line-of-sight velocity from our Alfven wave turbulence modeling of the
loops. In our computations, the relationship between the width of the
coronal emission lines and the orientation of the coronal loops with
respect to the line-of-sight direction is taken in to account. We
predict that in coronal loops, the transverse component of plasma
flows with respect to the loop axis move at the speed of 15-40 km/s. In
conclusion, Alfven waves are a strong candidate in explaining the flows
within the coronal loops and play an important role in the heating of
the chromosphere and corona.
Title: Evidence of nonthermal particles in coronal loops heated
impulsively by nanoflares
Authors: Testa, P.; De Pontieu, B.; Allred, J.; Carlsson, M.; Reale,
F.; Daw, A.; Hansteen, V.; Martinez-Sykora, J.; Liu, W.; DeLuca, E. E.;
Golub, L.; McKillop, S.; Reeves, K.; Saar, S.; Tian, H.; Lemen, J.;
Title, A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser, J. P.;
Kleint, L.; Kankelborg, C.; Jaeggli, S.
Bibcode: 2014Sci...346B.315T
Altcode: 2014arXiv1410.6130T
The physical processes causing energy exchange between the Sun’s
hot corona and its cool lower atmosphere remain poorly understood. The
chromosphere and transition region (TR) form an interface region between
the surface and the corona that is highly sensitive to the coronal
heating mechanism. High-resolution observations with the Interface
Region Imaging Spectrograph (IRIS) reveal rapid variability (~20 to
60 seconds) of intensity and velocity on small spatial scales (≲500
kilometers) at the footpoints of hot and dynamic coronal loops. The
observations are consistent with numerical simulations of heating by
beams of nonthermal electrons, which are generated in small impulsive
(≲30 seconds) heating events called “coronal nanoflares.” The
accelerated electrons deposit a sizable fraction of their energy
(≲1025 erg) in the chromosphere and TR. Our analysis
provides tight constraints on the properties of such electron beams
and new diagnostics for their presence in the nonflaring corona.
Title: Nonlinear Force-free Field Modeling of the Solar Magnetic
Carpet and Comparison with SDO/HMI and Sunrise/IMaX Observations
Authors: Chitta, L. P.; Kariyappa, R.; van Ballegooijen, A. A.;
DeLuca, E. E.; Solanki, S. K.
Bibcode: 2014ApJ...793..112C
Altcode: 2014arXiv1408.0497C
In the quiet solar photosphere, the mixed polarity fields form a
magnetic carpet that continuously evolves due to dynamical interaction
between the convective motions and magnetic field. This interplay is a
viable source to heat the solar atmosphere. In this work, we used the
line-of-sight (LOS) magnetograms obtained from the Helioseismic and
Magnetic Imager on the Solar Dynamics Observatory, and the Imaging
Magnetograph eXperiment instrument on the Sunrise balloon-borne
observatory, as time-dependent lower boundary conditions, to study the
evolution of the coronal magnetic field. We use a magneto-frictional
relaxation method, including hyperdiffusion, to produce a time series
of three-dimensional nonlinear force-free fields from a sequence
of photospheric LOS magnetograms. Vertical flows are added up to a
height of 0.7 Mm in the modeling to simulate the non-force-freeness
at the photosphere-chromosphere layers. Among the derived quantities,
we study the spatial and temporal variations of the energy dissipation
rate and energy flux. Our results show that the energy deposited in
the solar atmosphere is concentrated within 2 Mm of the photosphere and
there is not sufficient energy flux at the base of the corona to cover
radiative and conductive losses. Possible reasons and implications are
discussed. Better observational constraints of the magnetic field in
the chromosphere are crucial to understand the role of the magnetic
carpet in coronal heating.
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: A New Sigmoid Catalog from Hinode and the Solar Dynamics
Observatory: Statistical Properties and Evolutionary Histories
Authors: Savcheva, A. S.; McKillop, S. C.; McCauley, P. I.; Hanson,
E. M.; DeLuca, E. E.
Bibcode: 2014SoPh..289.3297S
Altcode: 2014SoPh..tmp...17S
We present a new sigmoid catalog covering the duration of the Hinode
mission and the Solar Dynamics Observatory (SDO) until the end of
2012. The catalog consists of 72 mostly long-lasting sigmoids. We
collect and make available all X-ray and EUV data from Hinode, SDO, and
the Solar TErrestrial RElations Observatory (STEREO), and we determine
the sigmoid lifetimes, sizes, and aspect ratios. We also collect the
line-of-sight magnetograms from the Helioseismic and Magnetic Imager
(HMI) for SDO or the Michelson Doppler Imager (MDI) on the Solar
and Heliospheric Observatory (SOHO) to measure flux versus time for
the lifetime of each region. We determine that the development of
a sigmoidal shape and eruptive activity is more strongly correlated
with flux cancelation than with emergence. We find that the eruptive
properties of the regions correlate well with the maximum flux,
largest change, and net change in flux in the regions. These results
have implications for constraining future flux-rope models of ARs and
gaining insight into their evolutionary properties.
Title: Observations of Subarcsecond Bright Dots in the Transition
Region above Sunspots with the Interface Region Imaging Spectrograph
Authors: Tian, H.; Kleint, L.; Peter, H.; Weber, M.; Testa, P.;
DeLuca, E.; Golub, L.; Schanche, N.
Bibcode: 2014ApJ...790L..29T
Altcode: 2014arXiv1407.1060T
Observations with the Interface Region Imaging Spectrograph (IRIS)
have revealed numerous sub-arcsecond bright dots in the transition
region above sunspots. These bright dots are seen in the 1400 Å and
1330 Å slit-jaw images. They are clearly present in all sunspots we
investigated, mostly in the penumbrae, but also occasionally in some
umbrae and light bridges. The bright dots in the penumbrae typically
appear slightly elongated, with the two dimensions being 300-600 km and
250-450 km, respectively. The long sides of these dots are often nearly
parallel to the bright filamentary structures in the penumbrae but
sometimes clearly deviate from the radial direction. Their lifetimes
are mostly less than one minute, although some dots last for a few
minutes or even longer. Their intensities are often a few times stronger
than the intensities of the surrounding environment in the slit-jaw
images. About half of the bright dots show apparent movement with
speeds of ~10-40 km s-1 in the radial direction. Spectra of
a few bright dots were obtained and the Si IV 1402.77 Å line profiles
in these dots are significantly broadened. The line intensity can be
enhanced by one to two orders of magnitude. Some relatively bright
and long-lasting dots are also observed in several passbands of the
Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory,
and they appear to be located at the bases of loop-like structures. Many
of these bright dots are likely associated with small-scale energy
release events at the transition region footpoints of magnetic loops.
Title: Simulations of the Kelvin-Helmholtz instability driven by
coronal mass ejections in the turbulent corona
Authors: Gomez, Daniel O.; DeLuca, Edward E.; Mininni, Pablo D.
Bibcode: 2014arXiv1408.2598G
Altcode:
Recent high resolution AIA/SDO images show evidence of the development
of the Kelvin-Helmholtz instability, as coronal mass ejections (CMEs)
expand in the ambient corona. A large-scale magnetic field mostly
tangential to the interface is inferred, both on the CME and on the
background sides. However, the magnetic field component along the
shear flow is not strong enough to quench the instability. There
is also observational evidence that the ambient corona is in a
turbulent regime, and therefore the criteria for the development
of the instability are a-priori expected to differ from the laminar
case. To study the evolution of the Kelvin-Helmholtz instability with
a turbulent background, we perform three-dimensional simulations of
the incompressible magnetohydrodynamic equations. The instability is
driven by a velocity profile tangential to the CME-corona interface,
which we simulate through a hyperbolic tangent profile. The turbulent
background is generated by the application of a stationary stirring
force. We compute the instability growth-rate for different values of
the turbulence intensity, and find that the role of turbulence is to
attenuate the growth. The fact that the Kelvin-Helmholtz instability
is observed, sets an upper limit to the correlation length of the
coronal background turbulence.
Title: The soft x-ray photon-counting telescope for solar observations
Authors: Sakao, Taro; Narukage, Noriyuki; Suematsu, Yoshinori;
Watanabe, Kyoko; Shimojo, Masumi; Imada, Shinsuke; Ishikawa,
Shin-nosuke; DeLuca, Edward E.
Bibcode: 2014SPIE.9144E..3DS
Altcode:
We present overview and development activities of a soft X-ray
photon-counting spectroscopic imager for the solar corona that
we conceive as a possible scientific payload for future space
solar missions including Japanese Solar-C. The soft X-ray imager
will employ a Wolter I grazing-incidence sector mirror with which
images of the corona (1 MK to beyond 10 MK) will be taken with
the highest-ever angular resolution (0.5"/pixel for a focal length
of 4 m) as a solar Xray telescope. In addition to high-resolution
imagery, we attempt to implement photon-counting capability for the
imager by employing a backside-illuminated CMOS image sensor as the
focal-plane device. Imaging-spectroscopy of the X-ray corona will be
performed for the first time in the energy range from ~0.5 keV up to
10 keV. The imaging-spectroscopic observations with the soft X-ray
imager will provide a noble probe for investigating mechanism(s) of
magnetic reconnection and generation of supra-thermal (non-thermal)
electrons associated with flares. Ongoing development activities in
Japan towards the photon-counting imager is described with emphasis
on that for sub-arcsecond-resolution grazing-incidence mirrors.
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: A Topological View at Observed Flare Features: An Extension
of the Standard Flare Model to 3D
Authors: Savcheva, Antonia; Pariat, Etienne; McKillop, Sean; Hanson,
Elizabeth; Su, Yingna; DeLuca, Edward E.
Bibcode: 2014AAS...22430301S
Altcode:
We conduct topology analysis of erupting non-linear force-free field
(NLFFF) configurations of eight sigmoidal active regions observed
with Hinode/XRT and SDO/AIA. The NLFFF models are computed using
the flux rope insertion method and unstable models are utilized to
represent the erupting configurations. Topology analysis shows that the
quasi-separatrix layers (QSLs) in the chromosphere match well the flare
ribbons observed in these regions. In addition, we show that low-lying
QSLs associated with the rising flux rope change shape and extent to
match the separating flare ribbons as observed by AIA. Post-flare loops
are fit well by field lines lying under the generalized X-line at the
bottom of the flux rope. We show a correspondence in the evolution
of the post-flare loops from a strong-to-weak sheared state and the
behavior of the field lines as the flux rope expands in the corona. We
show that transient corona holes are associated with the footprints
of the flux rope in the low atmosphere. In addition, we compute the
reconnected flux in one of the regions and using information from
the models constrain how much energy has been released during the
event. We use this kind of topology analysis to extend the standard
CME/flare model to full 3D and find implications to reconnection in 3D.
Title: Observational Signatures of Alfven Wave Turbulence in Solar
Coronal Loops
Authors: Asgari-Targhi, Mahboubeh; Imada, Shinsuke; DeLuca, Edward E.
Bibcode: 2014AAS...22432325A
Altcode:
The non-thermal width in coronal emission lines could be due to
the Alfven wave turbulence. In order to find observational evidence
of the Alfven waves that result in coronal heating, we examine and
analyze the dynamics of an active region observed on 2012 September
7. We use spectral line profiles of Fe XII, Fe XIII, Fe XV and Fe
XVI obtained by Extreme-ultraviolet Imaging Spectrometer (EIS) on
Hinode spacecraft. Line profile observations from EIS were generated
and compared with our computations of line of sight Alfven wave
amplitude. We show non-thermal velocities, Doppler outflows, and
intensities for loops in this active region and derive comparisons
between our numerical results and observations from EIS. In our modeling
we take into account the relationship between the width of the coronal
emission lines and the orientation of the coronal loops with respect
to the line-of-sight direction. We conclude that the Alfven wave
turbulence model is a strong candidate for explaining how the observed
loops are heated.
Title: Column Densities of an Eruptive Prominence over Time
Authors: McCauley, Patrick; DeLuca, Edward E.; Su, Yingna
Bibcode: 2014AAS...22421822M
Altcode:
We present a series of column density measurements for an eruptive
prominence. The eruption occurred on March 12th, 2012, and observations
were recorded by the Atmospheric Imaging Assembly (AIA) aboard the Solar
Dynamics Observatory. We estimate the background emission to obtain
an optical depth, which can be used to estimate the column density
at all positions along the prominence. This is done every 30 minutes
for 2 days leading up to the eruption. The series of column density
maps can then be used to estimate the total mass of the prominence as
it evolves with time. Whether or not there is significant mass loss
or loading is an important constraint on the eruption mechanism. Our
early work has found no significant change in the prominence mass over
the two days leading up to the eruption, but we are currently working
to reconcile a discrepancy between independent estimations made using
AIA's 193, 211, and 335 Angstrom passbands. The results from this work
will be presented.
Title: Structure and Dynamics of One Polar Crown Prominence Eruption
Authors: Su, Yingna; Van Ballegooijen, Adriaan A.; McCauley, Patrick I;
Reeves, Kathy; DeLuca, Edward E.; Ji, Haisheng
Bibcode: 2014AAS...22421820S
Altcode:
We will present the recent progress on the investigation of the polar
crown prominence that erupted on 2012 March 12. This prominence is
viewed at the east limb by SDO/AIA and displays a quasi vertical-thread
structure. Bright U-shape (horn-like) structure is observed surrounding
the upper portion of the prominence before the eruption and becomes
more prominent during the eruption. When viewed on the disk, STEREO-B
shows that this prominence is composed of a series of vertical threads
and displays a loop-like structure during the eruption. We focus on
the magnetic support of the prominence by studying the structure
and dynamics of the prominence before and during the eruption
using observations from SDO, Hinode, and STEREO. We found that the
transition from slow rise to fast rise phase is associated with magnetic
reconnection below rising prominence threads. We also constructed a
series of magnetic field models (including sheared arcade model and
twisted flux rope model) of the prominence using the “flux rope
insertion method”, we will compare them with observations in order
to find the best-fit model. Our recent progress on the thermodynamics
of the erupting prominence will also be presented.
Title: Dynamics of the Transition Corona
Authors: Masson, Sophie; McCauley, Patrick; Golub, Leon; Reeves,
Katharine K.; DeLuca, Edward E.
Bibcode: 2014ApJ...787..145M
Altcode: 2013arXiv1301.0740M
Magnetic reconnection between the open and closed magnetic fields in
the corona is believed to play a crucial role in the corona/heliosphere
coupling. At large scale, the exchange of open/closed connectivity is
expected to occur in pseudo-streamer (PS) structures. However, there
is neither clear observational evidence of how such coupling occurs
in PSs, nor evidence for how the magnetic reconnection evolves. Using
a newly developed technique, we enhance the off-limb magnetic fine
structures observed with the Atmospheric Imaging Assembly and identify
a PS-like feature located close to the northern coronal hole. We first
identify that the magnetic topology associated with the observation is
a PS, null-point (NP) related topology bounded by the open field. By
comparing the magnetic field configuration with the EUV emission
regions, we determined that most of the magnetic flux associated with
plasma emission are small loops below the PS basic NP and open field
bounding the PS topology. In order to interpret the evolution of the
PS, we referred to a three-dimensional MHD interchange reconnection
modeling the exchange of connectivity between small closed loops and the
open field. The observed PS fine structures follow the dynamics of the
magnetic field before and after reconnecting at the NP obtained by the
interchange model. Moreover, the pattern of the EUV plasma emission is
the same as the shape of the expected plasma emission location derived
from the simulation. These morphological and dynamical similarities
between the PS observations and the results from the simulation
strongly suggest that the evolution of the PS, and in particular
the opening/closing of the field, occurs via interchange/slipping
reconnection at the basic NP of the PS. Besides identifying the
mechanism at work in the large-scale coupling between the open and
closed fields, our results highlight that interchange reconnection
in PSs is a gradual physical process that differs from the impulsive
reconnection of the solar-jet model.
Title: Statistical Constraints on Joy's Law
Authors: Amouzou, Ernest C.; Munoz-Jaramillo, Andres; Martens, Petrus
C.; DeLuca, Edward E.
Bibcode: 2014AAS...22421829A
Altcode:
Using sunspot data from the observatories at Mt. Wilson and Kodaikanal,
active region tilt angles are analyzed for different active region
sizes and latitude bins. A number of similarly-shaped statistical
distributions were fitted to the data using maximum likelihood
estimation. In all cases, we find that the statistical distribution
best describing the number of active regions at a given tilt angle is a
Laplace distribution with the form (2β)-1*exp(-|x-μ|/β),
with 2° ≤ μ ≤ 11°, and 10° ≤ β ≤ 40°.
Title: An Airborne Infrared Telescope and Spectrograph for Solar
Eclipse Observations
Authors: DeLuca, Edward E.; Cheimets, Peter; Golub, Leon
Bibcode: 2014AAS...22412356D
Altcode:
The solar infrared spectrum offers great possibilities for direct
spatially resolved measurements of the solar coronal magnetic fields,
via imaging of the plasma that is constrained to follow the magnetic
field direction and via spectro-polarimetry that permits measurement
of the field strength in the corona. Energy stored in coronal magnetic
fields is released in flares and coronal mass ejections (CME) and
provides the ultimate source of energy for space weather. The large
scale structure of the coronal field, and the opening up of the field
in a transition zone between the closed and open corona determines
the speed and structure of the solar wind, providing the background
environment through which CMEs propagate. At present our only direct
measurements of the solar magnetic fields are in the photosphere
and chromosphere. The ability to determine where and why the corona
transitions from closed to open, combined with measurements of the
field strength via infrared coronal spectro-polarimetry will give us
a powerful new tool in our quest to develop the next generation of
forecasting models.We describe a first step in achieving this goal:
a proposal for a new IR telescope, image stabilization system, and
spectrometer, for the NCAR HIPER GV aircraft. The telescope/spectrograph
will operate in the 2-6micron wavelength region, during solar eclipses,
starting with the trans-north American eclipse in August 2017. The
HIAPER aircraft flying at ~35,000 ft will provide an excellent platform
for IR observations. Our imaging and spectroscopy experiment will
show the distribution and intensity of IR forbidden lines in the
solar corona.
Title: Data-constrained Magnetofrcitional Simulation of a Flux Rope
Build-up in a Sigmoidal Active Region
Authors: Savcheva, Antonia Stefanova; Mackay, D.; Meyer, K.; Gibb,
G.; DeLuca, E.
Bibcode: 2014shin.confE...3S
Altcode:
We present a data-constrained magnetofrictional (MF) simulation of
the evolution over two days of the sigmoidal active region from 6-7
Dec 2007. The lower boundary condition is supplied by a series of
line-of-sight (LoS) namgnetograms from MDI, but for the first time the
initial condition is taken from a data-constrained non-linear force-free
(NLFFF) model of the active region early on Dec 6. The NLFFF model is
produced with the flux rope insertion method and is constrained by a LoS
magnetogram, filament path from STEREO, and coronal loops from XRT. The
initial condition is that of a sheared arcade and as time progresses
the photospheric evolution builds a flux rope, which becomes unstable
a few hours before the actual observed eruption. We show field lines
and current density distributions over time and compare them to XRT
images. We present the evolution of the free and potential energy and
relative helicity in the region. We compare our results to a previous
a simulation starting from a potential field as initial condition.
Title: From the Tachocline Into the Heliosphere: Coupling a 3D
kinematic dynamo to the CCMC
Authors: Munoz-Jaramillo, Andres; Yeates, Anthony R; Martens, Petrus
C.; DeLuca, Edward E.
Bibcode: 2014AAS...22421103M
Altcode:
During the last decade, axisymmetric kinematic dynamo models have
contributed greatly to our understanding of the solar cycle. However,
with the advent of more powerful computers the limitation to axisymmetry
has been lifted. Here we present a 3D kinematic dynamo model where
active regions are driven by velocity perturbations calibrated to
reproduce observed active region properties (including the size and
flux of active regions, and the distribution of tilt angle with
latitude), resulting in a more consistent treatment of flux-tube
emergence in kinematic dynamo models than artificial flux deposition. We
demonstrate how this technique can be used to assimilate active region
observations obtained from the US National Solar Observatory/Kitt Peak
(NSO/KP) synoptic magnetograms and how our model couples naturally
with heliospheric models, paving the way for the simultaneous study
of the evolution of the magnetic field in the solar interior as well
as its impact on the heliosphere.
Title: Kelvin-Helmholtz instability driven by CMEs expanding in a
turbulent medium
Authors: Gomez, Daniel O.; DeLuca, Edward E.; Mininni, Pablo D
Bibcode: 2014AAS...22430302G
Altcode:
Recent high resolution AIA/SDO images show clear evidence of the
development of the Rayleigh-Taylor instability, as coronal mass
ejections (CMEs) expand in the ambient corona. A large-scale magnetic
field mostly tangential to the interface is observed, both on the
CME and on the background sides. However, this magnetic field is
not intense enough to quench the instability. The ambient corona is
expected to be in a turbulent regime, and therefore the development
of the Raleigh-Taylor instability can significantly differ from the
one corresponding to a laminar medium.To study the evolution of the
Rayleigh-Taylor instability in a turbulent background, we perform
three-dimensional simulations of the magnetohydrodynamic equations. The
instability is driven by a velocity profile tangential to the CME-corona
interface, which we simulate through a hyperbolic tangent profile. The
turbulent background is obtained by the application of a stationary
stirring force. One of the outcomes of these simulations is the
computation of the instability growth-rate for different values of
the correlation length of the turbulence.
Title: Discovery of Finely Structured Dynamic Solar Corona Observed
in the Hi-C Telescope
Authors: Winebarger, Amy R.; Cirtain, Jonathan; Golub, Leon; DeLuca,
Edward; Savage, Sabrina; Alexander, Caroline; Schuler, Timothy
Bibcode: 2014ApJ...787L..10W
Altcode:
In the Summer of 2012, the High-resolution Coronal Imager (Hi-C)
flew on board a NASA sounding rocket and collected the highest
spatial resolution images ever obtained of the solar corona. One of
the goals of the Hi-C flight was to characterize the substructure of
the solar corona. We therefore examine how the intensity scales from
AIA resolution to Hi-C resolution. For each low-resolution pixel, we
calculate the standard deviation in the contributing high-resolution
pixel intensities and compare that to the expected standard deviation
calculated from the noise. If these numbers are approximately equal,
the corona can be assumed to be smoothly varying, i.e., have no evidence
of substructure in the Hi-C image to within Hi-C's ability to measure
it given its throughput and readout noise. A standard deviation much
larger than the noise value indicates the presence of substructure. We
calculate these values for each low-resolution pixel for each frame
of the Hi-C data. On average, 70% of the pixels in each Hi-C image
show no evidence of substructure. The locations where substructure is
prevalent is in the moss regions and in regions of sheared magnetic
field. We also find that the level of substructure varies significantly
over the roughly 160 s of the Hi-C data analyzed here. This result
indicates that the finely structured corona is concentrated in regions
of heating and is highly time dependent.
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: Structure and Dynamics of an Eruptive Prominence on the
Quiet Sun
Authors: Su, Yingna; Reeves, Katharine K.; McCauley, Patrick; van
Ballegooijen, Adriaan A.; DeLuca, Edward E.
Bibcode: 2014IAUS..300..460S
Altcode:
We present preliminary results on the investigation of one polar crown
prominence that erupted on 2012 March 11. This prominence is viewed
at the east limb by SDO/AIA and displays a simple vertical-thread
structure. A bright U-shape (double horn-like) structure is observed
surrounding the upper portion of the prominence before the eruption and
becomes more prominent during the eruption. When viewed on the disk,
STEREO_B shows that this prominence is composed of series of vertical
threads and displays a loop-like structure during the eruption. We focus
on the magnetic support of the prominence by studying the structure
and dynamics before and during the eruption using observations from
SDO and STEREO. We will also present preliminary DEM analysis of the
cavity surrounding the prominence.
Title: Column Density Measurements of a Prominence Observed by AIA
Authors: McCauley, Patrick I.; Su, Yingna; DeLuca, Edward; van
Ballegooijen, Adriaan
Bibcode: 2014IAUS..300..449M
Altcode:
We present column density measurements of a polar crown prominence
observed on March 9th, 2012 by the Atmospheric Imaging Assembly (AIA)
aboard the Solar Dynamics Observatory. The structure was viewed on
the east limb by AIA and erupted about 30 hours after the observations
shown here. We estimate column density by approximating the obscured
background emission to obtain an optical depth. This can then be
combined with the absorption cross sections of neutral hydrogen and
helium, along with the He:H abundance ratio, to calculate column
density. We perform this calculation for the 171, 193, 211, and 335
Å AIA passbands.
Title: Total mass loading of prominences estimated from their
multi-spectral observations
Authors: Schwartz, Pavol; Heinzel, Peter; Kotrč, Pavel; Fárník,
František; Kupryakov, Yurij A.; DeLuca, Edward E.; Golub, Leon
Bibcode: 2014IAUS..300..458S
Altcode:
The total mass of several quiescent prominences observed in EUV by
the AIA instrument on board SDO, in soft X-rays by XRT on Hinode and
in Hα and CaII H by the SLS and HSFA spectrographs of the Ondřejov
observatory, was estimated. Values of asymmetry of coronal emissivity
obtained during the mass computations are compared with those estimated
from 193 Å intensities measured at the disk edge and just above
the limb.
Title: Future Needs for Remote Sensing in Heliophysics: Photonic
Observations (Invited)
Authors: DeLuca, E. E.; Paxton, L.
Bibcode: 2013AGUFMSM52A..03D
Altcode:
In this talk we will review the needs for new optical measurements
relevant to the Heliophysics program. To do that we will discuss
the challenges inherent in applying remote sensing to observing
state variables (density, temperature, velocity, etc) that span the
many orders of magnitude range required to understand our research
domain. The current state of remote sensing from IR to x-rays and
the science requirements that are driving the need for these solar
and space physics observations will be discussed. We will discuss
how the next generation of imaging and spectroscopy along with the
complimentary advances in space platforms, sensors, data handling
and data downlinks, enables us to make cost-effective advances in our
understanding. Thoughts on how to spend precious instrument development
funds will be given.
Title: Magnetohydrodynamic Modeling of the Solar Eruption on 2010
April 8
Authors: Kliem, B.; Su, Y. N.; van Ballegooijen, A. A.; DeLuca, E. E.
Bibcode: 2013ApJ...779..129K
Altcode: 2013arXiv1304.6981K
The structure of the coronal magnetic field prior to eruptive
processes and the conditions for the onset of eruption are important
issues that can be addressed through studying the magnetohydrodynamic
(MHD) stability and evolution of nonlinear force-free field (NLFFF)
models. This paper uses data-constrained NLFFF models of a solar active
region (AR) that erupted on 2010 April 8 as initial conditions in MHD
simulations. These models, constructed with the techniques of flux rope
insertion and magnetofrictional relaxation (MFR), include a stable,
an approximately marginally stable, and an unstable configuration. The
simulations confirm previous related results of MFR runs, particularly
that stable flux rope equilibria represent key features of the
observed pre-eruption coronal structure very well, and that there is
a limiting value of the axial flux in the rope for the existence of
stable NLFFF equilibria. The specific limiting value is located within a
tighter range, due to the sharper discrimination between stability and
instability by the MHD description. The MHD treatment of the eruptive
configuration yields a very good agreement with a number of observed
features, like the strongly inclined initial rise path and the close
temporal association between the coronal mass ejection and the onset of
flare reconnection. Minor differences occur in the velocity of flare
ribbon expansion and in the further evolution of the inclination;
these can be eliminated through refined simulations. We suggest that
the slingshot effect of horizontally bent flux in the source region
of eruptions can contribute significantly to the inclination of the
rise direction. Finally, we demonstrate that the onset criterion,
formulated in terms of a threshold value for the axial flux in the
rope, corresponds very well to the threshold of the torus instability
in the considered AR.
Title: The Spatial and Temporal Dependence of Coronal Heating by
Alfvén Wave Turbulence
Authors: Asgari-Targhi, M.; van Ballegooijen, A. A.; Cranmer, S. R.;
DeLuca, E. E.
Bibcode: 2013ApJ...773..111A
Altcode: 2013arXiv1306.6038A
The solar atmosphere may be heated by Alfvén waves that propagate up
from the convection zone and dissipate their energy in the chromosphere
and corona. To further test this theory, we consider wave heating in
an active region observed on 2012 March 7. A potential field model of
the region is constructed, and 22 field lines representing observed
coronal loops are traced through the model. Using a three-dimensional
(3D) reduced magnetohydrodynamics code, we simulate the dynamics
of Alfvén waves in and near the observed loops. The results for
different loops are combined into a single formula describing the
average heating rate Q as a function of position within the observed
active region. We suggest this expression may be approximately valid
also for other active regions, and therefore may be used to construct
3D, time-dependent models of the coronal plasma. Such models are needed
to understand the role of thermal non-equilibrium in the structuring
and dynamics of the Sun's corona.
Title: Numerical simulations of the CME on 2010 April 8
Authors: Su, Yingna; Kliem, Bernhard; van Ballegooijen, Adriaan;
Deluca, Edward
Bibcode: 2013IAUS..294..575S
Altcode:
We present 3D zero-beta ideal MHD simulations of the solar flare/CME
event that occurred in Active Region 11060 on 2010 April 8. The initial
magnetic configurations of the two simulations are stable nonlinear
force-free field and unstable magnetic field models constructed by Su
et al. (2011) using the flux rope insertion method. The MHD simulations
confirm that the stable model relaxes to a stable equilibrium, while
the unstable model erupts as a CME. Comparisons between observations
and MHD simulations of the CME are also presented.
Title: A New Sigmoid Catalog: Statistical Properties of Sigmoids
and Their Evolution
Authors: McKillop, Sean; Savcheva, A.; Hanson, E.; McCauley, P.;
DeLuca, E. E.
Bibcode: 2013SPD....44...31M
Altcode:
Sigmoids are sinuous structures located in active regions that have
characteristic “s-shaped” or inverted “s-shaped” loops. Active
regions containing sigmoids are observed to have higher rates of
flaring and CMEs. Previous work detailing the properties of sigmoids
has generally focused on specific case studies of a handful of
regions. Although such studies are representative of the structure
and evolution of these regions, significant insight can be gained by
an observational overview approach with systematic and statistical
analysis of a large sample of sigmoids. We present a new sample
of 72 sigmoidal regions observed in a wide wavelength range and in
different parts of the solar atmosphere by various instruments such
as the Hinode/XRT, SDO/AIA, STEREO, and LASCO. From this data we
compiled a comprehensive list of many different parameters including:
size and aspect ratio, presence of Ha or EUV filaments, flare and CME
association, number of sunspots, active region and sigmoid lifetimes,
etc. Our preliminary results show that sigmoids have a higher eruption
rate than other active regions. We also find that the ratio of the long
axis to short axis of the sigmoids has a strong peak at 2.5 and the
lifetime peaks at 2 days. We also follow the evolution of the magnetic
flux in the photosphere and derive whether the sigmoids appear during
the emergence or cancellation stages of active region evolution. These
results can provide constraints for models of flux rope evolution in
global simulations.
Title: Using the Dipolar and Quadrupolar Moments to Improve
Solar-Cycle Predictions Based on the Polar Magnetic Fields
Authors: Muñoz-Jaramillo, Andrés; Balmaceda, Laura A.; DeLuca,
Edward E.
Bibcode: 2013PhRvL.111d1106M
Altcode: 2013arXiv1308.2038M
The solar cycle and its associated magnetic activity are the main
drivers behind changes in the interplanetary environment and Earth’s
upper atmosphere (commonly referred to as space weather and climate). In
recent years there has been an effort to develop accurate solar cycle
predictions, leading to nearly a hundred widely spread predictions for
the amplitude of solar cycle 24. Here we show that cycle predictions
can be made more accurate if performed separately for each hemisphere,
taking advantage of information about both the dipolar and quadrupolar
moments of the solar magnetic field during minimum.
Title: Solar Cycle Propagation, Memory, and Prediction: Insights
from a Century of Magnetic Proxies
Authors: Munoz-Jaramillo, Andres; Dasi-Espuig, M.; Balmaceda, L. A.;
DeLuca, E. E.
Bibcode: 2013SPD....4440302M
Altcode:
In the simplest of forms, modern dynamo theory describes the solar cycle
as a process that takes the solar magnetic field (back and forth) from
a configuration that is predominantly poloidal (contained inside the
meridional plane), to one predominantly toroidal (wrapped around the
axis of rotation). However, there is still uncertainty and controversy
in the detailed understanding of this process. A major contributor to
this uncertainty is the lack of direct long-term databases covering
different components of the solar magnetic field (an issue mainly
affecting the poloidal component of the solar magnetic field). In
this talk we will review the different observations that can be used
as proxies for the solar magnetic field (in absence of direct magnetic
observations). I will present a recently standardized database that can
be used as a proxy for the evolution of the polar magnetic field. And
to conclude, I will show the insights that can be gained (by taking
advantage of this database) in the context of the transition between
the toroidal and poloidal phases of the cycle, solar cycle memory
as determined by the different mechanisms of flux transport, and the
practical goal of solar cycle prediction.
Title: Structure and Dynamics of the Polar Crown Prominence that
Erupted on 2012 March 12
Authors: Su, Yingna; Van Ballegooijen, A. A.; McCauley, P.; Reeves,
K.; DeLuca, E. E.
Bibcode: 2013SPD....4420302S
Altcode:
We will present preliminary results on the investigation of one polar
crown prominence that erupted on 2012 March 12. This prominence is
viewed at the east limb by SDO/AIA and displays a simple vertical-thread
structure. Bright U-shape (horn-like) structure is observed surrounding
the upper portion of the prominence before the eruption and becomes
more prominent during the eruption. When viewed on the disk, STEREO-B
shows that this prominence is composed of series of vertical threads
and displays a loop-like structure during the eruption. We focus on
the magnetic support of the prominence by studying the structure and
dynamics before and during the eruption using observations from SDO,
Hinode, and STEREO. We will explore magnetic field modeling of this
prominence using the flux rope insertion method. We will also present
preliminary analysis on the thermodynamics of the prominence, namely
DEM analysis of the cavity surrounding the prominence, as well as
column density measurements. This work is supported by NASA Grant
(#NNX12AB25G) and NASA Contract (#SP02H1701R) from LMSAL to SAO.
Title: An MHD Model of a Solar Eruption Starting from NLFFF Initial
Conditions
Authors: DeLuca, Edward E.; Su, Y.; Kliem, B.; Van Ballegooijen, A. A.
Bibcode: 2013SPD....4410301D
Altcode:
The structure of the coronal magnetic field prior to eruptive processes
and the conditions for the onset of eruption are important issues that
can be addressed through studying the magnetohydrodynamic stability
and evolution of nonlinear force-free field (NLFFF) models. This
talk uses data-constrained NLFFF models of a solar active region that
erupted on 2010 Apri 8 as initial conditions in MHD simulations. These
models, constructed with the techniques of flux rope insertion and
magnetofrictional relaxation, include a stable, an approximately
marginally stable, and an unstable configuration. The simulations
confirm previous related results of magnetofrictional relaxation runs,
in particular that stable flux rope equilibria represent key features
of the observed pre-eruption coronal structure very well and that there
is a limiting value of the axial flux in the rope for the existence
of stable NLFFF equilibria. The specific limiting value is located
within a tighter range, due to the sharper discrimination between
stability and instability by the MHD description. The MHD treatment of
the eruptive configuration yields very good agreement with a number of
observed features like the strongly inclined initial rise path and the
close temporal association between the coronal mass ejection and the
onset of flare reconnection. Minor differences occur in the velocity of
flare ribbon expansion and in the further evolution of the inclination;
these can be eliminated through refined simulations. We suggest that
the slingshot effect of horizontally bent flux in the source region
of eruptions can contribute significantly to the inclination of the
rise direction. Finally, we demonstrate that the onset criterion
formulated in terms of a threshold value for the axial flux in the
rope corresponds very well to the threshold of the torus instability
in the considered active region.
Title: Fixing the Leak: Empirical Corrections for the Small Light
Leak in Hinode XRT
Authors: Saar, Steven H.; DeLuca, E. E.; McCauley, P.; Kobelski, A.
Bibcode: 2013SPD....44...93S
Altcode:
On May 9, 2012, the the straylight level of XRT on Hinode suddenly
increased, consistent with the appearance of a pinhole in the entrance
filter (possibly a micrometeorite breach). The effect of this event
is most noticeable in the optical G band data, which shows an average
light excess of ~30%. However, data in several of the X-ray filters is
also affected, due to low sensitivity "tails" of their filter responses
into the visible. Observations taken with the G band filter but with
the visible light shutter (VLS) closed show a weak, slightly shifted,
out-of-focus image, revealing the leaked light. The intensity of
the leak depends on telescope pointing, dropping strongly for images
taken off-disk. By monitoring light levels in the corners of full-Sun
Ti-poly filter images, we determine the approximate time of the event:
~13:30 UT. We use pairs of images taken just-before and after the filter
breach to directly measure the leakage in two affected X-ray filters. We
then develop a model using a scaled, shifted, and smoothed versions
of the VLS closed images to remove the contamination. We estimate
the uncertainties involved in our proposed correction procedure. This
research was supported under NASA contract NNM07AB07C for Hinode XRT.
Title: Using the dipolar and quadrupolar moments to improve solar
cycle predictions based on the polar magnetic fields
Authors: Munoz-Jaramillo, Andres; Balmaceda, L. A.; DeLuca, E. E.
Bibcode: 2013SPD....44..129M
Altcode:
The solar cycle and its associated magnetic activity are the main
drivers behind changes in the interplanetary environment and the Earth's
upper atmosphere. These changes have a direct impact on the lifetime of
space-based assets and can create hazards to astronauts in space. In
recent years there has been an effort to develop accurate solar cycle
predictions (with aims at predicting the long-term evolution of space
weather), leading to nearly a hundred widely spread predictions for
the amplitude of solar cycle 24. In this presentation we show how cycle
predictions can be made more accurate if performed separately for each
hemisphere, taking advantage of information about both the dipolar
and quadrupolar moments of the solar magnetic field. Additionally,
by extending the relationship between polar flux at solar minimum
and the amplitude of the next cycle to encompass a full century, we
demonstrate the power of predictions based on the solar polar field --
paving the way for a new generation of better and more accurate solar
cycle predictions.
Title: The Spatial and Temporal Dependence of Coronal Heating by
Alfven Wave Turbulence
Authors: Asgari-Targhi, Mahboubeh; Van Ballegooijen, A. A.; Cranmer,
S. R.; DeLuca, E. E.
Bibcode: 2013SPD....4430501A
Altcode:
The solar atmosphere may be heated by Alfven waves that propagate up
from the convection zone and dissipate their energy in the chromosphere
and corona. To further test this theory, we consider wave heating in an
active region observed on 2012 March 7. A potential field model of the
region is constructed, and 22 field lines representing observed coronal
loops are traced through the model. Using a three-dimensional (3D)
reduced magneto-hydrodynamics (MHD) code, we simulate the dynamics of
Alfven waves in and near the observed loops. The results for different
loops are combined into a single formula describing the average
heating rate $Q$ as function of position within the observed active
region. We suggest this expression may be approximately valid also
for other active regions, and therefore may be used to construct 3D,
time-dependent models of the coronal plasma. Such models are needed
to understand the role of thermal non-equilibrium in the structuring
and dynamics of the Sun's corona.
Title: Dynamics of the Transition Corona
Authors: Masson, Sophie; McCauley, P.; Golub, L.; Reeves, K.; DeLuca,
E. E.
Bibcode: 2013SPD....44...27M
Altcode:
Magnetic reconnection between open and closed magnetic field in the
corona is believed to play a crucial role in the corona / heliosphere
coupling. At large scale, the exchange of open /closed connectivity
is expected to occur in pseudo-streamer structures. However,
there is neither clear observational evidence of how such coupling
occurs in pseudo-streamers, nor evidence for how the magnetic
reconnection evolves. Using a newly-developed technique, we enhance
the off-limb magnetic fine structures observed with AIA and identify
a pseudo-streamer-like feature located close to the northern coronal
hole. We first identify that the magnetic topology associated with the
observation is a pseudo-streamer, null-point-related topology bounded
by open field. We then compare the evolution of the observed pseudo-
streamer fine structure in the location of strong currents, i.e. in
the region of energy dissipation, with the dynamics of the magnetic
field resulting from the interchange reconnection obtained in a fully
3D MHD simulation. The morphological and dynamical similarities between
the pseudo-streamer observations and the results from the simulation
strongly suggest that the evolution of the pseudo-streamer is caused
by interchange reconnection in a null-point topology that is embedded
in Quasi-Separatrix layers. Besides identifying the mechanism at work
in the large-scale coupling between open and closed field, our results
highlight that interchange reconnection in pseudo-streamers is a gradual
physical process that differs from the impulsive reconnection of the
solar-jet model.
Title: IRIS EPO Program Provides Experiences in Authentic NASA Science
Authors: Scherrer, Deborah K.; Des Jardins, A.; Ward, B.; DeLuca,
E. E.; Conrad, L.; Larimer, R.; Green, R.; Martin, Lockheed
Bibcode: 2013SPD....44..157S
Altcode:
The Education and Public Outreach program for NASA's IRIS mission
focuses on providing experiences in authentic solar science research to
elementary and secondary students, STEM undergraduates, families and the
public through science events, and public outreach through a variety
of online resources. Our poster will highlight the achievements of
these programs, details of their preparation, and use of collaborative
partnerships to implement them.
Title: Observations and Modeling of the Emerging Extreme-ultraviolet
Loops in the Quiet Sun as Seen with the Solar Dynamics Observatory
Authors: Chitta, L. P.; Kariyappa, R.; van Ballegooijen, A. A.;
DeLuca, E. E.; Hasan, S. S.; Hanslmeier, A.
Bibcode: 2013ApJ...768...32C
Altcode: 2013arXiv1303.3426C
We used data from the Helioseismic and Magnetic Imager (HMI) and the
Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory
(SDO) to study coronal loops at small scales, emerging in the quiet
Sun. With HMI line-of-sight magnetograms, we derive the integrated
and unsigned photospheric magnetic flux at the loop footpoints in the
photosphere. These loops are bright in the EUV channels of AIA. Using
the six AIA EUV filters, we construct the differential emission measure
(DEM) in the temperature range 5.7-6.5 in log T (K) for several hours
of observations. The observed DEMs have a peak distribution around
log T ≈ 6.3, falling rapidly at higher temperatures. For log T <
6.3, DEMs are comparable to their peak values within an order of
magnitude. The emission-weighted temperature is calculated, and its
time variations are compared with those of magnetic flux. We present
two possibilities for explaining the observed DEMs and temperatures
variations. (1) Assuming that the observed loops are composed of
a hundred thin strands with certain radius and length, we tested
three time-dependent heating models and compared the resulting DEMs
and temperatures with the observed quantities. This modeling used
enthalpy-based thermal evolution of loops (EBTEL), a zero-dimensional
(0D) hydrodynamic code. The comparisons suggest that a medium-frequency
heating model with a population of different heating amplitudes can
roughly reproduce the observations. (2) We also consider a loop model
with steady heating and non-uniform cross-section of the loop along
its length, and find that this model can also reproduce the observed
DEMs, provided the loop expansion factor γ ~ 5-10. More observational
constraints are required to better understand the nature of coronal
heating in the short emerging loops on the quiet Sun.
Title: Solar Cycle Propagation, Memory, and Prediction: Insights
from a Century of Magnetic Proxies
Authors: Muñoz-Jaramillo, Andrés; Dasi-Espuig, María; Balmaceda,
Laura A.; DeLuca, Edward E.
Bibcode: 2013ApJ...767L..25M
Altcode: 2013arXiv1304.3151M
The solar cycle and its associated magnetic activity are the main
drivers behind changes in the interplanetary environment and Earth's
upper atmosphere (commonly referred to as space weather). These
changes have a direct impact on the lifetime of space-based assets
and can create hazards to astronauts in space. In recent years there
has been an effort to develop accurate solar cycle predictions (with
aims at predicting the long-term evolution of space weather), leading
to nearly a hundred widely spread predictions for the amplitude of
solar cycle 24. A major contributor to the disagreement is the lack
of direct long-term databases covering different components of the
solar magnetic field (toroidal versus poloidal). Here, we use sunspot
area and polar faculae measurements spanning a full century (as our
toroidal and poloidal field proxies) to study solar cycle propagation,
memory, and prediction. Our results substantiate predictions based
on the polar magnetic fields, whereas we find sunspot area to be
uncorrelated with cycle amplitude unless multiplied by area-weighted
average tilt. This suggests that the joint assimilation of tilt and
sunspot area is a better choice (with aims to cycle prediction) than
sunspot area alone, and adds to the evidence in favor of active region
emergence and decay as the main mechanism of poloidal field generation
(i.e., the Babcock-Leighton mechanism). Finally, by looking at the
correlation between our poloidal and toroidal proxies across multiple
cycles, we find solar cycle memory to be limited to only one cycle.
Title: Sigmoidal Active Regions on the Sun: Statistical and Detailed
Studies
Authors: Hanson, E.; DeLuca, E.; Savcheva, A. S.
Bibcode: 2012AGUFMSH51A2202H
Altcode:
We have compiled a catalog of sigmoidal active regions occurring
in Aug 2010 - May 2012. The catalog data will enable us to identify
variations and unifying characteristics of the sigmoids. In the long
run, analyzing the typical behavior of these regions will improve
space weather forecasting capabilities because sigmoidal regions
have been shown to be a good predictor of eruptions. Additionally,
we modeled the magnetic field of one of the cataloged sigmoids (NOAA
active region 11474 at 2012.05.08/05:38:00) four hours prior to an
eruption. The models consisted of a flux rope in a potential arcade,
with the path of the rope following the H-α filament. The best fit
model yields a current distribution which, viewed in cross section,
exhibits a characteristic teardrop-shaped topology. Field lines passing
through specific zones in the cross section define unique shapes in
the sigmoid: the single S, the two Js, the overlying potential arcade,
and the underlying small loops. The static model is slightly unstable;
therefore, further relaxation of the model mimics the time evolution
of the active region leading up to its eruption at 09:26. Future
work will examine the relationship between Quasi-Separatrix Layer
(QSL) maps and flare ribbons seen in 304Å images from the eruption.;
Current and magnetic field lines from a model of a marginally stable
flux rope. ; Cross section of the current. Note the x-line at the base
of the flux rope.
Title: MHD Modeling of the Solar Eruption on 2010 April 8
Authors: Kliem, B.; Su, Y.; Van Ballegooijen, A. A.; DeLuca, E.
Bibcode: 2012AGUFMSH51A2194K
Altcode:
We present a numerical MHD study of the solar eruption on 2010 April
8, extending the previous modeling of the source region in Su et
al. (2011) which had employed the flux rope insertion method and
magnetofrictional relaxation. The threshold of the rope's axial flux
for the loss of equilibrium obtained in Su et al. is confirmed. We find
that the inserted flux rope partly splits for slightly subcritical axial
flux. Starting with slightly supercritical axial flux in the rope, the
MHD simulation yields a fast and strongly inclined eruption as observed
by the STEREO and SDO instruments. The causes of the inclination will
be explored. We also model photospheric changes that may have driven
the flux rope from a stable to the unstable configuration.
Title: Non-Linear Force Free Field Modeling and Flare Ribbon
Comparison of Several Flaring Active Regions
Authors: McKillop, S.; Savcheva, A. S.; DeLuca, E.
Bibcode: 2012AGUFMSH51A2201M
Altcode:
Three dimensional magnetic field models are critically important for
understanding the storage and release of energy in flaring active
regions. In this project we present models of several flaring active
regions (ARs) observed with the Atmospheric Imaging Assembly (AIA)
aboard the Solar Dynamics Observatory (SDO). For each AR we built
a Non-Linear Force Free Field (NLFFF) model using Helioseismic and
Magnetic Imager (HMI) magnetograms as the boundary condition and
AIA coronal observations as the constraint on the models. The models
based on observations just prior to the flare have unstable solutions
from which Quasi-Separatrix Layers (QSL) maps are calculated at low
heights in the corona. Detailed comparison of the QSL and the flare
ribbons provide insight into the magnetic configuration at the particle
acceleration site.
Title: Understanding the Role of the Polar Fields on the Propagation
of the Solar Cycle
Authors: Munoz-Jaramillo, A.; DeLuca, E. E.
Bibcode: 2012AGUFMSH13C2263M
Altcode:
In addition to the well known 11-year periodicity, the solar cycle also
presents long-term modulations of its amplitude and period which play
a determinant role in the evolution of space weather and climate. To
this date, the efforts at understanding long-term solar variability
have focused on the active parts of the cycle using sunspot properties
as their main source of data. However, the recent extend minimum
of sunspot cycle 23 has shown us that the quiet parts of the cycle
are equally important and thus long-term databases complementary to
sunspot properties are necessary. Here we use a homogeneous database
of polar magnetic flux measurements going back to the beginning of
the 20th century to study the role of the polar flux in the long-term
evolution of the heliospheric magnetic field, as well as the relevance
of the polar magnetic field for the evolution of the solar cycle. We
demonstrate that the polar fields are crucial for the evolution of
both types of magnetic field and how the results presented here lay
the foundations for a new generation of sunspot cycle predictions.
Title: The Spatial Dependence of Coronal Heating by Alfven Wave
Turbulence
Authors: Asgari-targhi, M.; Van Ballegooijen, A. A.; Cranmer, S. R.;
DeLuca, E. E.
Bibcode: 2012AGUFMSH31B..05A
Altcode:
We consider the wave heating in an active region observed on 7th of
March 2012 (Image). Using a potential field model we choose 22 field
lines and construct 3D MHD models of the Alfven waves along those
field lines. Based on those results we develop a heating formula
for the coronal loops observed. In our calculations, we establish
explicit relationships between the energy deposited and the loop
parameters, such as the length, and the magnetic field strength along
the loop. We also look at the variation of the heating within the loops
and predict the velocity fluctuations seen with future high-resolution
spectrographs.A potential field modeling of an active region observed
on 7th of March 2012.
Title: Photospheric Flux Cancellation and the Build-up of Sigmoidal
Flux Ropes on the Sun
Authors: Savcheva, A. S.; Green, L. M.; van Ballegooijen, A. A.;
DeLuca, E. E.
Bibcode: 2012ApJ...759..105S
Altcode:
In this study we explore the scenario of photospheric flux cancellation
being the primary formation mechanism of sigmoidal flux ropes in
decaying active regions. We analyze magnetogram and X-ray observations
together with data-driven non-linear force-free field (NLFFF) models of
observed sigmoidal regions to test this idea. We measure the total and
canceled fluxes in the regions from MDI magnetograms, as well as the
axial and poloidal flux content of the modeled NLFFF flux ropes for
three sigmoids—2007 February, 2007 December, and 2010 February. We
infer that the sum of the poloidal and axial flux in the flux ropes for
most models amounts to about 60%-70% of the canceled flux and 30%-50%
of the total flux in the regions. The flux measurements and the analysis
of the magnetic field structure show that the sigmoids first develop
a strong axial field manifested as a sheared arcade and then, as flux
cancellation proceeds, form long S-shaped field lines that contribute to
the poloidal flux. In addition, the dips in the S-shaped field lines are
located at the sites of flux cancellation that have been identified from
the MDI magnetograms. We find that the line-of-sight-integrated free
energy is also concentrated at these locations for all three regions,
which can be liberated in the process of eruption. Flare-associated
brightenings and flare loops coincide with the location of the X-line
topology that develops at the site of most vigorous flux cancellation.
Title: The x-ray/EUV telescope for the Solar-C mission: science and
development activities
Authors: Sakao, Taro; Narukage, Noriyuki; Imada, Shinsuke; Suematsu,
Yoshinori; Shimojo, Masumi; Tsuneta, Saku; DeLuca, Edward E.; Watanabe,
Kyoko; Ishikawa, Shin-nosuke
Bibcode: 2012SPIE.8443E..0AS
Altcode:
We report science and development activities of the X-ray/EUV telescope
for the Japanese Solar-C mission whose projected launch around 2019. The
telescope consists of a package of (a) a normal-incidence (NI) EUV
telescope and (b) a grazing-incidence (GI) soft X-ray telescope. The NI
telescope chiefly provides images of low corona (whose temperature 1
MK or even lower) with ultra-high angular resolution (0.2-0.3"/pixel)
in 3 wavelength bands (304, 171, and 94 angstroms). On the other
hand, the GI telescope provides images of the corona with a wide
temperature coverage (1 MK to beyond 10 MK) with the highest-ever
angular resolution (~0.5"/pixel) as a soft X-ray coronal imager. The
set of NI and GI telescopes should provide crucial information for
establishing magnetic and gas-dynamic connection between the corona and
the lower atmosphere of the Sun which is essential for understanding
heating of, and plasma activities in, the corona. Moreover, we attempt
to implement photon-counting capability for the GI telescope with
which imaging-spectroscopy of the X-ray corona will be performed for
the first time, in the energy range from ~0.5 keV up to 10 keV. The
imaging-spectroscopic observations will provide totally-new information
on mechanism(s) for the generation of hot coronal plasmas (heated
beyond a few MK), those for magnetic reconnection, and even generation
of supra-thermal electrons associated with flares. An overview of
instrument outline and science for the X-ray photoncounting telescope
are presented, together with ongoing development activities in Japan
towards soft X-ray photoncounting observations, focusing on high-speed
X-ray CMOS detector and sub-arcsecond-resolution GI mirror.
Title: Cooler and Hotter X-ray Bright Points from Hinode/XRT
Observations
Authors: Kariyappa, R.; DeLuca, E. E.; Saar, S. H.; Golub, L.; Damé,
L.; Varghese, B. A.
Bibcode: 2012ASPC..454..149K
Altcode:
We use a 7-hour (17:00 UT - 24:00 UT) time sequence of soft X-ray images
observed almost simultaneously in two filters (Ti_poly and Al_mesh) on
April 14, 2007 with X-Ray Telescope (XRT) on-board the Hinode mission
to determine the temperature of X-ray bright points (XBPs). A sample
of 14 XBPs and 2 background coronal regions have been identified and
selected on both the images for detailed analysis. The temperature of
XBPs is determined by filter ratio method. We find that the XBPs show
temperature fluctuations and that the average temperature ranges from
1.1 MK to 3.4 MK which may correspond to different X-ray fluxes. These
results suggest the existence of cooler and hotter XBPs and that the
heating rate of XBPs is highly variable on short time scales.
Title: Comparison of a Magnetohydrodynamical Simulation and a
Non-Linear Force-Free Field Model of a Sigmoidal Active Region.
Authors: Pariat, Etienne; DeLuca, Edward; Van Ballegooijen, Adriaan;
Aulanier, Guillaume; Savcheva, Antonia
Bibcode: 2012cosp...39.1448P
Altcode: 2012cosp.meet.1448P
Sigmoids are solar magnetic structures where highly non-potential
fields (strong shear/twist) are believed to be present. Thanks to
the high level of free magnetic energy, active regions with sigmoids
possess a higher eruptivity. In the present study, we will present
a comparive topological analysis between a Non-Linear Force Free
Field (NLFFF) model of sigmoid region, and a three-dimensional (3D)
magnetohydrodynamics numerical simulation of the formation and eruption
of such a structure. The MHD simulation is based on an idealized
magnetic field distribution and the sigmoidal flux rope is built by
means of shearing motions and magnetic polarity diffusion. The NLFFF
model is based on the flux rope insertion method which utilizes line of
sight magnetograms and X-ray observations of the region to constrain the
models. We compare the geometrical and topological properties of the 3D
magnetic fields given by both methods in their pre-eruptive phases. We
arrive at a consistent picture for the evolution and eruption of the
sigmoid by using the idealized MHD simulation as a context for the more
specific observationally-constrained NLFFF models and data. Although,
the two models are very different in their setups, we identify strong
similarities between the two models and understandable differences. By
computing the squashing factor in different horizontal maps at various
heights above the photosphere and in vertical cuts in the domains,
we demonstrate the existence of key Quasi-Separatrix Layers (QSL)
eventually involved in the dynamic of the structure. We also show that
there are electric current concentrations coinciding with the main
QSLs. Finally, we perform torus instability analysis and show that
a combination between reconnection at the main QSL and the resulting
expansion of the flux rope into the torus instability domain is the
cause of the CME in both models. This study finally highlights the
interest of the use of in-depth topological tools to study highly
non-potential magnetic fields.
Title: Calibrating 100 Years of Polar Faculae Measurements:
Implications for the Evolution of the Heliospheric Magnetic Field
Authors: Muñoz-Jaramillo, Andrés; Sheeley, Neil R.; Zhang, Jie;
DeLuca, Edward E.
Bibcode: 2012ApJ...753..146M
Altcode: 2013arXiv1303.0345M
Although the Sun's polar magnetic fields are thought to provide
important clues for understanding the 11 year sunspot cycle, including
the observed variations of its amplitude and period, the current
database of high-quality polar field measurements spans relatively
few sunspot cycles. In this paper, we address this deficiency by
consolidating Mount Wilson Observatory polar faculae data from four
data reduction campaigns, validating it through a comparison with
facular data counted automatically from Michelson Doppler Imager (MDI)
intensitygrams, and calibrating it against polar field measurements
taken by the Wilcox Solar Observatory and average polar field and
total polar flux calculated using MDI line-of-sight magnetograms. Our
results show that the consolidated polar facular measurements are in
excellent agreement with both polar field and polar flux estimates,
making them an ideal proxy to study the evolution of the polar
magnetic field. Additionally, we combine this database with sunspot
area measurements to study the role of the polar magnetic flux in the
evolution of the heliospheric magnetic field (HMF). We find that there
is a strong correlation between HMF and polar flux at solar minimum
and that, taken together, polar flux and sunspot area are better
at explaining the evolution of the HMF during the last century than
sunspot area alone.
Title: Photospheric flux cancellation and the build-up of sigmoidal
flux ropes
Authors: Savcheva, Antonia Stefanova; Green, L.; van Ballegooijen,
A.; DeLuca, E.
Bibcode: 2012shin.confE.122S
Altcode:
The magnetic structure of sigmoidal active regions is generally
associated with the presence of a twisted flux rope held down by a
potential arcade. There are competing theories of how the flux rope
develops - by flux emergence, cancellation, or footpoint motions. We
look at how flux cancellation in several sigmoidal regions, observed
with XRT, affects the buildup of the underlying flux ropes. We use
MDI magnetograms to quantify the flux cancellation, and the flux rope
insertion method to construct non-linear force free field models of the
regions. These models allow us to produce 3-D magnetic field models
and see how the fields evolve in time. The models show how the flux
ropes energy and magnetic flux changes during the different stages in
the flux cancellation. Flux cancellation events are associated with
build up of twist in the region in accordance with the accepted flux
cancellation picture. The location of flares and build-up of free
energy is well correlated with flux cancellation events.
Title: Dynamics of the Solar Magnetic Bright Points Derived from
Their Horizontal Motions
Authors: Chitta, L. P.; van Ballegooijen, A. A.; Rouppe van der Voort,
L.; DeLuca, E. E.; Kariyappa, R.
Bibcode: 2012ApJ...752...48C
Altcode: 2012arXiv1204.4362C
The subarcsecond bright points (BPs) associated with the small-scale
magnetic fields in the lower solar atmosphere are advected by
the evolution of the photospheric granules. We measure various
quantities related to the horizontal motions of the BPs observed in
two wavelengths, including the velocity autocorrelation function. A
1 hr time sequence of wideband Hα observations conducted at the
Swedish 1 m Solar Telescope (SST) and a 4 hr Hinode G-band time
sequence observed with the Solar Optical Telescope are used in this
work. We follow 97 SST and 212 Hinode BPs with 3800 and 1950 individual
velocity measurements, respectively. For its high cadence of 5 s as
compared to 30 s for Hinode data, we emphasize more the results from
SST data. The BP positional uncertainty achieved by SST is as low as 3
km. The position errors contribute 0.75 km2 s-2
to the variance of the observed velocities. The raw and corrected
velocity measurements in both directions, i.e., (vx ,
vy ), have Gaussian distributions with standard deviations
of (1.32, 1.22) and (1.00, 0.86) km s-1, respectively. The
BP motions have correlation times of about 22-30 s. We construct the
power spectrum of the horizontal motions as a function of frequency,
a quantity that is useful and relevant to the studies of generation
of Alfvén waves. Photospheric turbulent diffusion at timescales less
than 200 s is found to satisfy a power law with an index of 1.59.
Title: Sigmoidal Active Region on the Sun: Comparison of a
Magnetohydrodynamical Simulation and a Nonlinear Force-free Field
Model
Authors: Savcheva, A.; Pariat, E.; van Ballegooijen, A.; Aulanier,
G.; DeLuca, E.
Bibcode: 2012ApJ...750...15S
Altcode:
In this paper we show that when accurate nonlinear force-free
field (NLFFF) models are analyzed together with high-resolution
magnetohydrodynamic (MHD) simulations, we can determine the physical
causes for the coronal mass ejection (CME) eruption on 2007 February
12. We compare the geometrical and topological properties of the
three-dimensional magnetic fields given by both methods in their
pre-eruptive phases. We arrive at a consistent picture for the
evolution and eruption of the sigmoid. Both the MHD simulation and
the observed magnetic field evolution show that flux cancellation
plays an important role in building the flux rope. We compute the
squashing factor, Q, in different horizontal maps in the domains. The
main shape of the quasi-separatrix layers (QSLs) is very similar
between the NLFFF and MHD models. The main QSLs lie on the edge of
the flux rope. While the QSLs in the NLFFF model are more complex due
to the intrinsic large complexity in the field, the QSLs in the MHD
model are smooth and possess lower maximum value of Q. In addition,
we demonstrate the existence of hyperbolic flux tubes (HFTs) in both
models in vertical cross sections of Q. The main HFT, located under the
twisted flux rope in both models, is identified as the most probable
site for reconnection. We also show that there are electric current
concentrations coinciding with the main QSLs. Finally, we perform torus
instability analysis and show that a combination between reconnection
at the HFT and the resulting expansion of the flux rope into the torus
instability domain is the cause of the CME in both models.
Title: Mass Loading of Quiescent Prominences
Authors: Schwartz, P.; Heinzel, 2. P.; Kotrč, P.; Anzer, U.;
Kupryakov, Y.; DeLuca, E.
Bibcode: 2012ASPC..456...73S
Altcode:
From April through June 2011 a multi-spectral observing campaign of
quiescent prominences was made. Observations were carried out in EUV
by SDO/AIA, in soft X-rays by XRT on Hinode and in Hα by horizontal
spectrographs of the Ondrřejov observatory. In this work the masses of
selected prominences, observed on May 18 and April 19, were determined
in order to test the method and our semi-automatic computer code.
Title: Applications of Quasi-Separatrix Layer Maps in Understanding
an XRT Sigmoid
Authors: Savcheva, A.; van Ballegooijen, A.; DeLuca, E. E.
Bibcode: 2012ASPC..455..261S
Altcode:
We present our recent work on utilizing Quasi-Separatrix Layer (QSL)
maps for understanding the structure, evolution, and pre-eruption
behavior of the quiescent sigmoid observed with Hinode/XRT in February
2007. QSL maps are created at various heights in the corona and for
10 different observations during the evolution of the long-lasting
sigmoid. This is the first QSL analysis based on a non-linear force
free field of a sigmoid. We point out some major properties of the
QSL topology in the sigmoid and we explore how they change spatially
and temporally with the evolution of the sigmoid. We explore how QSL
topology and strength relate to current distributions and torsion
factors in the moments leading to the B-class flare. While the current
distribution in the region is smooth and extended, the QSLs show much
finer structure which may prove to be of help in pinpointing possible
reconnection or heating sites.
Title: Topological Tools For The Analysis Of Active Region Filament
Stability
Authors: DeLuca, Edward E.; Savcheva, A.; van Ballegooijen, A.;
Pariat, E.; Aulanier, G.; Su, Y.
Bibcode: 2012AAS...22020207D
Altcode:
The combination of accurate NLFFF models and high resolution MHD
simulations allows us to study the changes in stability of an active
region filament before a CME. Our analysis strongly supports the
following sequence of events leading up to the CME: first there is a
build up of magnetic flux in the filament through flux cancellation
beneath a developing flux rope; as the flux rope develops a hyperbolic
flux tube (HFT) forms beneath the flux rope; reconnection across
the HFT raises the flux rope while adding addition flux to it; the
eruption is triggered when the flux rope becomes torus-unstable. The
work applies topological analysis tools that have been developed over
the past decade and points the way for future work on the critical
problem of CME initiation in solar active regions. We will present
the uses of this approach, current limitations and future prospects.
Title: Coronal Rotation from XBPs Observed with Hinode/XRT
Authors: Kariyappa, R.; DeLuca, E.
Bibcode: 2012ASPC..456..207K
Altcode:
We have selected a large number of X-ray bright points (XBPs) over
synoptic soft X-ray full-disk images observed using Al-Mesh with X-Ray
Telescope (XRT) onboard the Hinode spacecraft during July-December,
2008. We have analyzed the full-disk images using SSW in IDL. We used
the tracer method to identify and trace the passage of XBPs over the
solar disc with the help of overlaying grids. We also obtained the
position (Latitude and Longitude), size & brightness information
for XBPs using tracer method as a function of time and thus calculated
sidereal angular rotation rate of corona at different latitudes. We
have compared the rotation rate with latitude, size and brightness of
XBPs. We found that the corona rotates differentially and it appears
that the larger XBPs show a lower sidereal angular rotation rate,
the smaller XBPs exhibit higher rotation rate, similar to sunspots.
Title: X-Ray Searches for Solar Axions
Authors: Hudson, H. S.; Acton, L. W.; DeLuca, E. E.; Hannah, I. G.;
Reardon, K.; Van Bibber, K.
Bibcode: 2012ASPC..455...25H
Altcode: 2012arXiv1201.4607H
Axions generated thermally in the solar core can convert nearly directly
to X-rays as they pass through the solar atmosphere via interaction with
the magnetic field. The result of this conversion process would be a
diffuse centrally-concentrated source of few-keV X-rays at disk center;
it would have a known dimension, of order 10% of the solar diameter, and
a spectral distribution resembling the blackbody spectrum of the solar
core. Its spatial structure in detail would depend on the distribution
of mass and field in the solar atmosphere. The brightness of the source
depends upon these factors as well as the unknown coupling constant
and the unknown mass of the axion; this particle is hypothetical and
no firm evidence for its existence has been found yet. We describe the
solar magnetic environment as an axion/photon converter and discuss
the upper limits obtained by existing and dedicated observations from
three solar X-ray observatories: Yohkoh, RHESSI, and Hinode.
Title: Calibration Of a Century of Polar Field Measurements and
what this Tells us About the Long-term Variability of the Solar and
Heliospheric Magnetic Field
Authors: Munoz-Jaramillo, Andres; Sheeley, N. R.; Zhang, J.; DeLuca,
E. E.
Bibcode: 2012AAS...22012304M
Altcode:
In addition to the well known 11-year periodicity, the solar cycle also
presents long-term modulations of its amplitude and period which play
a determinant role in the evolution of space weather and climate. To
this date, the efforts at understanding long-term solar variability
have focused on the active parts of the cycle using sunspot properties
as their main source of data. However, the recent extend minimum of
sunspot cycle 23 has shown us that the quiet parts of the cycle are
equally important and thus long-term databases complementary to sunspot
properties are necessary. Here we show how to consolidate Mount
Wilson Observatory polar faculae data from four observational campaigns
(1906-1964, Sheeley 1966; 1960-1975, Sheeley 1976; 1975-1990, Sheeley
1991; 1985-2007, Sheeley 2008), validate it through a comparison
with facular data counted automatically from MDI intensitygrams,
and calibrate it against polar field measurements taken by the Wilcox
Solar Observatory (1977-2011) and average polar field and total polar
flux calculated using MDI line-of-sight magnetograms (1996-2011). We also show that the consolidated polar facular measurements are
in excellent agreement with both polar field and polar flux estimates,
making them an ideal proxy to study the evolution of the polar magnetic
field since 1906 and use this proxy to study the role of polar flux in
the evolution of the solar cycle and the Heliospheric Magnetic Field
(HMF).
Title: Hot Plasma Detected in Active Regions by HINODE/XRT and SDO/AIA
Authors: Reale, F.; Testa, P.; Guarrasi, M.; DeLuca, E.; Peres, G.;
Golub, L.
Bibcode: 2012ASPC..456..129R
Altcode:
Multiple ratios of Hinode/XRT filters showed evidence of a minor
very hot emission measure component in active regions. Recently also
SDO/AIA detected hot plasma in the core of an active region. Here
we provide estimates showing that the amount of emission measure of
the hot component detected with SDO is consistent with that detected
with Hinode/XRT.
Title: Dynamics of the Photospheric Bright Points Observed With SST
and Hinode
Authors: Chitta, Lakshmi Pradeep; van Ballegooijen, A.; Rouppe van
der Voort, L.; DeLuca, E.; Kariyappa, R.
Bibcode: 2012AAS...22020614C
Altcode: 2012AAS...22020614P
The horizontal motions of the solar magnetic bright points (BPs)
observed in two wavelengths (SST Halpha and Hinode/SOT G-band)
is studied in detail. With emphasis on SST results: the velocity
distribution of horizontal motions is found to be a Gaussian. The
auto-correlations of observed velocities is also obtained. An
empirical fit to the observed auto-correlation gives us a positional
uncertainty of 3 km and the error in the velocity measurements to be
0.87 km s$^{-1}$. Due to the non-Lorentzian, cusp-like nature of the
auto-correlation, the power spectrum of the BP motions shows enhanced
power at frequencies exceeding 0.02 Hz. The diffusion of magnetic field
due to granular evolution at short timescales is found to satisfy a
power law with a slope of 1.59.
Title: The Effect of Flux Cancellation on Building Sigmoidal Flux
Ropes
Authors: Savcheva, Antonia; Green, L.; van Ballegooijen, A.; DeLuca, E.
Bibcode: 2012AAS...22041105S
Altcode:
The magnetic structure of sigmoidal active regions is generally
associated with the presence of a twisted flux rope held down by a
potential arcade. There are competing theories of how the flux rope
develops - by flux emergence, cancellation, or footpoint motions. We
look at how flux cancellation in several sigmoidal regions, observed
with XRT, affects the buildup of the underlying flux ropes. We use
MDI magnetograms to quantify the flux cancellation, and the flux rope
insertion method to construct non-linear force free field models of the
regions. These models allow us to produce 3-D magnetic field models
and see how the fields evolve in time. The models show how the flux
ropes energy and magnetic flux changes during the different stages in
the flux cancellation. Flux cancellation events are associated with
build up of twist in the region in accordance with the accepted flux
cancelation picture. The location of flares and build-up of free energy
is well correlated with flux cancellation events.
Title: Measuring Uncertainties in the Hinode X-Ray Telescope
Authors: Kobelski, A.; Saar, S.; McKenzie, D. E.; Weber, M.; Reeves,
K.; DeLuca, E.
Bibcode: 2012ASPC..456..241K
Altcode:
We have developed estimates of the systematic photometric uncertainties
the X-Ray Telescope (Kano et al. (2008)) on Hinode (Kosugi et
al.(2007)). These estimates are included as optional returns from the
standard XRT data reduction software, xrt_prep.pro. Included in the
software estimates are uncertainties from instrument vignetting, dark
current subtraction, split bias leveling, fourier filtering and JPEG
compression. We show that these uncertainties are generally smaller
than the photon counting uncertainty. However, due to the reliance
on assumptions of plasma radiation models and elemental abundances,
photon counting is not included in the software.
Title: Topological tools for the analysis of active region filament
stability
Authors: DeLuca, Edward E.; Savcheva, A.; van Ballegooijen, A.;
Pariat, E.; Aulanier, G.; Su, Y.
Bibcode: 2012decs.confE..64D
Altcode:
The combination of accurate NLFFF models and high resolution MHD
simulations allows us to study the changes in stability of an active
region filament before a CME. Our analysis strongly supports the
following sequence of events leading up to the CME: first there is a
build up of magnetic flux in the filament through flux cancellation
beneath a developing flux rope; as the flux rope develops a hyperbolic
flux tube (HFT) forms beneath the flux rope; reconnection across
the HFT raises the flux rope while adding addition flux to it; the
eruption is triggered when the flux rope becomes torus-unstable. The
work applies topological analysis tools that have been developed over
the past decade and points the way for future work on the critical
problem of CME initiation in solar active regions. We will discuss
the uses of this approach, current limitations and future prospects.
Title: Field Topology Analysis of a Long-lasting Coronal Sigmoid
Authors: Savcheva, A. S.; van Ballegooijen, A. A.; DeLuca, E. E.
Bibcode: 2012ApJ...744...78S
Altcode:
We present the first field topology analysis based on nonlinear
force-free field (NLFFF) models of a long-lasting coronal sigmoid
observed in 2007 February with the X-Ray Telescope on Hinode. The
NLFFF models are built with the flux rope insertion method and
give the three-dimensional coronal magnetic field as constrained by
observed coronal loop structures and photospheric magnetograms. Based
on these models, we have computed horizontal maps of the current and
the squashing factor Q for 25 different heights in the corona for all
six days of the evolution of the region. We use the squashing factor
to quantify the degree of change of the field line linkage and to
identify prominent quasi-separatrix layers (QSLs). We discuss the major
properties of these QSL maps and devise a way to pick out important QSLs
since our calculation cannot reach high values of Q. The complexity
in the QSL maps reflects the high degree of fragmentation of the
photospheric field. We find main QSLs and current concentrations that
outline the flux rope cavity and that become characteristically S-shaped
during the evolution of the sigmoid. We note that, although intermittent
bald patches exist along the length of the sigmoid during its whole
evolution, the flux rope remains stable for several days. However,
shortly after the topology of the field exhibits hyperbolic flux tubes
(HFT) on February 7 and February 12 the sigmoid loses equilibrium
and produces two B-class flares and associated coronal mass ejections
(CMEs). The location of the most elevated part of the HFT in our model
coincides with the inferred locations of the two flares. Therefore, we
suggest that the presence of an HFT in a coronal magnetic configuration
may be an indication that the system is ready to erupt. We offer a
scenario in which magnetic reconnection at the HFT drives the system
toward the marginally stable state. Once this state is reached, loss
of equilibrium occurs via the torus instability, producing a CME.
Title: The Atmospheric Imaging Assembly (AIA) on the Solar Dynamics
Observatory (SDO)
Authors: Lemen, James R.; Title, Alan M.; Akin, David J.; Boerner,
Paul F.; Chou, Catherine; Drake, Jerry F.; Duncan, Dexter W.; Edwards,
Christopher G.; Friedlaender, Frank M.; Heyman, Gary F.; Hurlburt, Neal
E.; Katz, Noah L.; Kushner, Gary D.; Levay, Michael; Lindgren, Russell
W.; Mathur, Dnyanesh P.; McFeaters, Edward L.; Mitchell, Sarah; Rehse,
Roger A.; Schrijver, Carolus J.; Springer, Larry A.; Stern, Robert A.;
Tarbell, Theodore D.; Wuelser, Jean-Pierre; Wolfson, C. Jacob; Yanari,
Carl; Bookbinder, Jay A.; Cheimets, Peter N.; Caldwell, David; Deluca,
Edward E.; Gates, Richard; Golub, Leon; Park, Sang; Podgorski, William
A.; Bush, Rock I.; Scherrer, Philip H.; Gummin, Mark A.; Smith, Peter;
Auker, Gary; Jerram, Paul; Pool, Peter; Soufli, Regina; Windt, David
L.; Beardsley, Sarah; Clapp, Matthew; Lang, James; Waltham, Nicholas
Bibcode: 2012SoPh..275...17L
Altcode: 2011SoPh..tmp..106L; 2011SoPh..tmp..172L; 2011SoPh..tmp..241L;
2011SoPh..tmp..115L
The Atmospheric Imaging Assembly (AIA) provides multiple simultaneous
high-resolution full-disk images of the corona and transition region
up to 0.5 R⊙ above the solar limb with 1.5-arcsec spatial
resolution and 12-second temporal resolution. The AIA consists of four
telescopes that employ normal-incidence, multilayer-coated optics to
provide narrow-band imaging of seven extreme ultraviolet (EUV) band
passes centered on specific lines: Fe XVIII (94 Å), Fe XVII, XXI
(131 Å), Fe IX (171 Å), Fe XII, XXIV (193 Å), Fe XIV (211 Å),
He II (304 Å), and Fe XVI (335 Å). One telescope observes C IV
(near 1600 Å) and the nearby continuum (1700 Å) and has a filter
that observes in the visible to enable coalignment with images from
other telescopes. The temperature diagnostics of the EUV emissions
cover the range from 6×104 K to 2×107 K. The
AIA was launched as a part of NASA's Solar Dynamics Observatory (SDO)
mission on 11 February 2010. AIA will advance our understanding of the
mechanisms of solar variability and of how the Sun's energy is stored
and released into the heliosphere and geospace.
Title: Nonlinear Force-Free Modeling of Aug 4 & 10, 2010 Sigmoids
via Flux Rope Insertion Method
Authors: Behm, Tyler; DeLuca, E.; Savcheva, A.
Bibcode: 2012AAS...21914404B
Altcode:
The high spatial resolution of space-based solar telescopes like
AIA and Hinode/XRT has allowed us to see fine S-shaped structures
in active regions. The collection of such S-shaped loops is known
as a sigmoid and are of great interest to solar physics since 68%
of coronal mass ejections appear in such regions. In our research,
we detail methods of studying sigmoids by using magnetograms to make
non-linear force free field models and by comparing these models to the
observed loops in X-ray and EUV images. We use the flux rope insertion
method to set the initial parameters for these models. Furthermore,
we examine the ability of contour maps of field divergence to study
the field topology of sigmoids. From our models, we estimate the free
energy stored in the sigmoids. From our field divergence maps, we find
features of high divergence also known as quasi-separatrix layers,
which can point to probable location for reconnection.
Title: The Wave Properties of Coronal Bright Fronts Observed Using
SDO/AIA
Authors: Long, David M.; DeLuca, Edward E.; Gallagher, Peter T.
Bibcode: 2011ApJ...741L..21L
Altcode: 2011arXiv1109.5897L
Coronal bright fronts (CBFs) are large-scale wavefronts that propagate
through the solar corona at hundreds of kilometers per second. While
their kinematics have been studied in detail, many questions
remain regarding the temporal evolution of their amplitude and pulse
width. Here, contemporaneous high cadence, multi-thermal observations
of the solar corona from the Solar Dynamic Observatory (SDO) and
Solar TErrestrial RElations Observatory (STEREO) spacecraft are used
to determine the kinematics and expansion rate of a CBF wavefront
observed on 2010 August 14. The CBF was found to have a lower initial
velocity with weaker deceleration in STEREO observations compared
to SDO observations (~340 km s-1 and -72 m s-2
as opposed to ~410 km s-1 and -279 m s-2). The
CBF kinematics from SDO were found to be highly passband-dependent,
with an initial velocity ranging from 379 ± 12 km s-1
to 460 ± 28 km s-1 and acceleration ranging from -128 ±
28 m s-2 to -431 ± 86 m s-2 in the 335 Å and
304 Å passbands, respectively. These kinematics were used to estimate
a quiet coronal magnetic field strength range of ~1-2 G. Significant
pulse broadening was also observed, with expansion rates of ~130 km
s-1 (STEREO) and ~220 km s-1 (SDO). By treating
the CBF as a linear superposition of sinusoidal waves within a Gaussian
envelope, the resulting dispersion rate of the pulse was found to be
~8-13 Mm2 s-1. These results are indicative
of a fast-mode magnetoacoustic wave pulse propagating through an
inhomogeneous medium.
Title: Photon-counting soft x-ray telescope for the Solar-C mission
Authors: Sakao, Taro; Narukage, Noriyuki; Shimojo, Masumi; Tsuneta,
Saku; Suematsu, Yoshinori; Miyazaki, Satoshi; Imada, Shinsuke;
Nishizuka, Naoto; Watanabe, Kyoko; Dotani, Tadayasu; DeLuca, Edward
E.; Ishikawa, Shin-nosuke
Bibcode: 2011SPIE.8148E..0CS
Altcode: 2011SPIE.8148E..11S
We report instrument outline as well as science of the photon-counting
soft X-ray telescope that we have been studying as a possible scientific
payload for the Japanese Solar-C mission whose projected launch around
2019. Soft X-rays (~1- 10 keV) from the solar corona include rich
information on (1) possible mechanism(s) for heating the bright core of
active regions seen in soft X-rays (namely, the hottest portion in the
non-flaring corona), (2) dynamics and magnetohydrodynamic structures
associated with magnetic reconnection processes ongoing in flares,
and even (3) generation of supra-thermal distributions of coronal
plasmas associated with flares. Nevertheless, imaging-spectroscopic
investigation of the soft X-ray corona has so far remained unexplored
due to difficulty in the instrumentation for achieving this aim. With
the advent of recent remarkable progress in CMOS-APS detector
technology, the photon-counting X-ray telescope will be capable
of, in addition to conventional photon-integration type exposures,
performing imaging-spectroscopic investigation on active regions and
flares, thus providing, for example, detailed temperature information
(beyond the sofar- utilized filter-ratio temperature) at each spatial
point of the observing target. The photon-counting X-ray telescope will
emply a Wolter type I optics with a piece of a segmented mirror whose
focal length 4 meters, combined with a focal-plane CMOS-APS detector
(0.4-0.5"/pixel) whose frame read-out rate required to be as high as
1000 fps.
Title: Propagation of Polar Coronal Jets in the Fast Solar Wind
Authors: Miralles, M. P.; Cranmer, S. R.; Raymond, J. C.; Savcheva,
A. S.; Stenborg, G.; Deluca, E. E.
Bibcode: 2011exas.conf..119M
Altcode:
We present results of an ongoing observational study of the physical
properties and kinematics of polar coronal jets. While magnetic
reconnection is considered the prime driving mechanism of the ejected
plasma, the processes at work during reconnection are not yet completely
understood. We use a combination of X-ray, UV, and visible-light imaging
to probe the jet plasma, and we trace polar jets from their reconnection
sites into the fast solar wind. Multi-instrument measurements of
polar jets will put firm constraints on the mechanisms driving the
jets and on the relative contribution of jets to the overall fast
solar wind. This work is supported by NASA grant NNX09AH22G to the
Smithsonian Astrophysical Observatory.
Title: Heating of the Solar Chromosphere and Corona by Alfvén
Wave Turbulence
Authors: van Ballegooijen, A. A.; Asgari-Targhi, M.; Cranmer, S. R.;
DeLuca, E. E.
Bibcode: 2011ApJ...736....3V
Altcode: 2011arXiv1105.0402V
A three-dimensional magnetohydrodynamic (MHD) model for the propagation
and dissipation of Alfvén waves in a coronal loop is developed. The
model includes the lower atmospheres at the two ends of the loop. The
waves originate on small spatial scales (less than 100 km) inside
the kilogauss flux elements in the photosphere. The model describes
the nonlinear interactions between Alfvén waves using the reduced
MHD approximation. The increase of Alfvén speed with height in
the chromosphere and transition region (TR) causes strong wave
reflection, which leads to counter-propagating waves and turbulence
in the photospheric and chromospheric parts of the flux tube. Part of
the wave energy is transmitted through the TR and produces turbulence
in the corona. We find that the hot coronal loops typically found in
active regions can be explained in terms of Alfvén wave turbulence,
provided that the small-scale footpoint motions have velocities of 1-2
km s-1 and timescales of 60-200 s. The heating rate per
unit volume in the chromosphere is two to three orders of magnitude
larger than that in the corona. We construct a series of models with
different values of the model parameters, and find that the coronal
heating rate increases with coronal field strength and decreases
with loop length. We conclude that coronal loops and the underlying
chromosphere may both be heated by Alfvénic turbulence.
Title: Solar Dynamics Observatory Discovers Thin High Temperature
Strands in Coronal Active Regions
Authors: Reale, Fabio; Guarrasi, Massimiliano; Testa, Paola; DeLuca,
Edward E.; Peres, Giovanni; Golub, Leon
Bibcode: 2011ApJ...736L..16R
Altcode: 2011arXiv1106.1591R
One scenario proposed to explain the million degree solar corona
is a finely stranded corona where each strand is heated by a rapid
pulse. However, such fine structure has neither been resolved through
direct imaging observations nor conclusively shown through indirect
observations of extended superhot plasma. Recently, it has been shown
that the observed difference in the appearance of cool and warm coronal
loops (~1 MK and ~2-3 MK, respectively)—warm loops appearing "fuzzier"
than cool loops—can be explained by models of loops composed of
subarcsecond strands, which are impulsively heated up to ~10 MK. That
work predicts that images of hot coronal loops (gsim 6 MK) should
again show fine structure. Here we show that the predicted effect is
indeed widely observed in an active region with the Solar Dynamics
Observatory, thus supporting a scenario where impulsive heating of
fine loop strands plays an important role in powering the active corona.
Title: Observations and Magnetic Field Modeling of the Flare/coronal
Mass Ejection Event on 2010 April 8
Authors: Su, Yingna; Surges, Vincent; van Ballegooijen, Adriaan;
DeLuca, Edward; Golub, Leon
Bibcode: 2011ApJ...734...53S
Altcode:
We present a study of the flare/coronal mass ejection event that
occurred in Active Region 11060 on 2010 April 8. This event also
involves a filament eruption, EIT wave, and coronal dimming. Prior to
the flare onset and filament eruption, both SDO/AIA and STEREO/EUVI
observe a nearly horizontal filament ejection along the internal
polarity inversion line, where flux cancellations frequently occur as
observed by SDO/HMI. Using the flux-rope insertion method developed
by van Ballegooijen, we construct a grid of magnetic field models
using two magneto-frictional relaxation methods. We find that the
poloidal flux is significantly reduced during the relaxation process,
though one relaxation method preserves the poloidal flux better
than the other. The best-fit pre-flare NLFFF model is constrained by
matching the coronal loops observed by SDO/AIA and Hinode/XRT. We find
that the axial flux in this model is very close to the threshold of
instability. For the model that becomes unstable due to an increase of
the axial flux, the reconnected field lines below the X-point closely
match the observed highly sheared flare loops at the event onset. The
footpoints of the erupting flux rope are located around the coronal
dimming regions. Both observational and modeling results support
the premise that this event may be initiated by catastrophic loss of
equilibrium caused by an increase of the axial flux in the flux rope,
which is driven by flux cancellations.
Title: Photospheric Flux Cancellation and the Build-up of Sigmoidal
Flux Ropes
Authors: Savcheva, Antonia; Green, L.; DeLuca, E.; van Ballegooijen, A.
Bibcode: 2011SPD....42.1806S
Altcode: 2011BAAS..43S.1806S
The magnetic structure of sigmoidal active regions is generally
associated with the presence of a twisted flux rope held down by a
potential arcade. There are competing theories of how the flux rope
develops - by flux emergence, cancellation, or footpoint motions. We
look at how flux cancellation in several sigmoidal regions, observed
with XRT and AIA, affects the buildup of the underlying flux ropes. We
use MDI and HMI magnetograms to quantify the flux cancellation, and the
flux rope insertion method to construct non-linear force free field
models of the regions. We present magnetic maps and the 3D flux rope
structure. We correlate the locations of flares and build-up of free
energy and helicity with flux cancellation events. We show how the
flux ropes energy and flux budget changes with the different stages
in the flux cancellation.
Title: Wavefront Expansion and Dispersion of Coronal Bright Fronts
Authors: Long, David; DeLuca, E.; Gallagher, P.
Bibcode: 2011SPD....42.0505L
Altcode: 2011BAAS..43S.0505L
The true nature of Coronal Bright Fronts (CBFs; commonly called "EIT
Waves") remains enigmatic despite more than ten years of research. High
cadence contemporaneous observations from the Solar Dynamic
Observatory (SDO) and Solar TErrestrial RElations Observatory (STEREO)
spacecraft are used here to determine the kinematics and dispersion
of a CBF pulse observed on 2010 August 14. The CBF exhibited clear
deceleration with propagation, with lower initial velocity and weaker
deceleration in STEREO observations compared to SDO. The kinematics
of the CBF were found to be highly passband dependent, with the pulse
exhibiting higher initial velocity and stronger deceleration in cooler
passbands. Significant pulse broadening was also measured using both
STEREO ( 55 km/s) andSDO ( 65 km/s) observations. The dispersion rate
of the pulse was derived by modeling the CBF as a linear superposition
of sinusoidal waves within a Gaussian envelope. These results imply
that the observed CBF is a fast-mode magnetoacoustic wave, and allowed
the quiet coronal magnetic field strength to be estimated at 1-2 G.
Title: Coronal-Temperature-Diagnostic Capability of the Hinode/
X-Ray Telescope Based on Self-Consistent Calibration
Authors: Narukage, N.; Sakao, T.; Kano, R.; Hara, H.; Shimojo, M.;
Bando, T.; Urayama, F.; DeLuca, E.; Golub, L.; Weber, M.; Grigis,
P.; Cirtain, J.; Tsuneta, S.
Bibcode: 2011SoPh..269..169N
Altcode: 2010arXiv1011.2867N; 2011SoPh..tmp....1N
The X-Ray Telescope (XRT) onboard the Hinode satellite is an X-ray
imager that observes the solar corona with unprecedentedly high angular
resolution (consistent with its 1″ pixel size). XRT has nine X-ray
analysis filters with different temperature responses. One of the most
significant scientific features of this telescope is its capability
of diagnosing coronal temperatures from less than 1 MK to more than
10 MK, which has never been accomplished before. To make full use
of this capability, accurate calibration of the coronal temperature
response of XRT is indispensable and is presented in this article. The
effect of on-orbit contamination is also taken into account in the
calibration. On the basis of our calibration results, we review the
coronal-temperature-diagnostic capability of XRT.
Title: Temperature variability in X-ray bright points observed
with Hinode/XRT
Authors: Kariyappa, R.; Deluca, E. E.; Saar, S. H.; Golub, L.; Damé,
L.; Pevtsov, A. A.; Varghese, B. A.
Bibcode: 2011A&A...526A..78K
Altcode:
Aims: We investigate the variability in temperature as
a function of time among a sample of coronal X-ray bright points
(XBPs).
Methods: We analysed a 7-h (17:00-24:00 UT) long time
sequence of soft X-ray images observed almost simultaneously in two
filters (Ti_poly and Al_mesh) on April 14, 2007 with X-ray telescope
(XRT) onboard the Hinode mission. We identified and selected 14 XBPs
for a detailed analysis. The light curves of XBPs were derived using
the SolarSoft library in IDL. The temperature of XBPs was determined
using the calibrated temperature response curves of the two filters
by means of the intensity ratio method.
Results: We find that
the XBPs show a high variability in their temperature and that the
average temperature ranges from 1.1 MK to 3.4 MK. The variations
in temperature are often correlated with changes in average X-ray
emission. It is evident from the results of time series that the XBP
heating rate can be highly variable on short timescales, suggesting
that it has a reconnection origin.
Title: Temperature Distribution of a Non-flaring Active Region from
Simultaneous Hinode XRT and EIS Observations
Authors: Testa, Paola; Reale, Fabio; Landi, Enrico; DeLuca, Edward E.;
Kashyap, Vinay
Bibcode: 2011ApJ...728...30T
Altcode: 2010arXiv1012.0346T
We analyze coordinated Hinode X-ray Telescope (XRT) and Extreme
Ultraviolet Imaging Spectrometer (EIS) observations of a non-flaring
active region to investigate the thermal properties of coronal plasma
taking advantage of the complementary diagnostics provided by the
two instruments. In particular, we want to explore the presence of
hot plasma in non-flaring regions. Independent temperature analyses
from the XRT multi-filter data set, and the EIS spectra, including
the instrument entire wavelength range, provide a cross-check of the
different temperature diagnostics techniques applicable to broadband and
spectral data, respectively, and insights into cross-calibration of the
two instruments. The emission measure distributions, (EM(T)), we derive
from the two data sets have similar width and peak temperature, but
show a systematic shift of the absolute values, the EIS (EM(T)) being
smaller than the XRT (EM(T)) by approximately a factor two. We explore
possible causes of this discrepancy, and we discuss the influence of the
assumptions for the plasma element abundances. Specifically, we find
that the disagreement between the results from the two instruments
is significantly mitigated by assuming chemical composition closer
to the solar photospheric composition rather than the often adopted
"coronal" composition. We find that the data do not provide conclusive
evidence on the high temperature (log T(K) >~ 6.5) tail of the
plasma temperature distribution, however, suggesting its presence to
a level in agreement with recent findings for other non-flaring regions.
Title: Comparison of simulated and observed loop-top emission in
flares using the AIA telescopes on SDO
Authors: Engell, A.; Reeves, K. K.; Ji, L.; Deluca, E. E.; Smith,
R.; Golub, L.
Bibcode: 2010AGUFMSH11A1596E
Altcode:
We investigate the spatial and temporal behavior of emission in
flaring loops observed by AIA's 193 (Fe XXIV/XII), 131(Fe XX), 094
(Fe XVIII), 335 (Fe XVI), 211 (Fe XIV), and 171 (Fe IX) channels for
two C class flares and one M class flare. Plotting light curves from
loop-top areas in the six channels reveals the temporal distributions
as a function of the ionization stages, with the same characteristic
behavior identifiable in all three flares. The order of appearance
is from the highest ionization state (FeXXIV) to the lowest (Fe XVI),
and the observations are compared with the Reeves, Warren & Forbes
(2007) model of flare loop energization, calculated for the various
AIA channels. We also model the effects of non-equilibrium ionization
on the simulated light curves.
Title: Observations of Coronal Bright Fronts using SDO/AIA
Authors: Long, D.; Deluca, E. E.; Gallagher, P. T.
Bibcode: 2010AGUFMSH23A1825L
Altcode:
Coronal bright fronts (CBFs; commonly called ``EIT waves'') have
been studied in detail for over ten years but remain a source of much
debate. We present the first observations of a CBF using the Atmospheric
Imaging Assembly (AIA) onboard the Solar Dynamic Observatory (SDO). An
intensity profiling technique is used to automatically identify
the position of the CBF. The resulting kinematics of the pulse
are studied in detail, with the CBF exhibiting clear deceleration
with propagation. The multi-wavelength capabilities of SDO/AIA are
also used to examine the CBF across multiple passbands. The CBF is
evident in both the 193 and 211~Å passbands, with the 171~Å passband
showing no clear CBF signal in contrast to previous observations from
other space-based instruments. Comparing these results with similar
observations from STEREO/EUVI, we suggest that CBFs may best be
approximated as freely-propagating magneto-acoustic waves.
Title: A Unified Model for Chromospheric and Coronal Heating Driven
by Small-Scale Random Footpoint Motions
Authors: van Ballegooijen, A. A.; Cranmer, S. R.; Asgari-Targhi, M.;
Deluca, E. E.
Bibcode: 2010AGUFMSH31C1802V
Altcode:
The solar corona is thought to be heated by dissipation of magnetic
disturbances that propagate up from the Sun's convection zone. We
propose that a major contribution to the heating comes from disturbances
that originate on small spatial scales inside the kilogauss magnetic
flux elements in the photosphere. Interactions of convective flows with
such flux elements produce Alfven waves that travel upward along the
magnetic field lines. When they reach the chromosphere and transition
region, the waves reflect, producing counter-propagating waves in the
chromosphere. Such counter-propagating waves are subject to well-known
nonlinear wave-wave interactions that can lead to the development
of turbulence. We simulate the dynamics of Alfven waves using a 3D
MHD model of a coronal loop (including the lower atmospheres at the
two ends of the loop) and we find that strong turbulence does indeed
develop in the lower parts of the flux tube. Some of the wave energy is
transmitted into the corona and produces turbulence there. We find that
the hot coronal loops typically found in active regions can be explained
in terms of Alfven wave turbulence, provided the photospheric footpoint
motions have a velocity of 1 - 2 km/s and a correlation time of about
60 seconds. The heating rate in the chromosphere is 2 to 3 orders of
magnitude larger than that in the corona, consistent with empirical
models of facular regions. We conclude that coronal loops and the
underlying chromosphere may both be heated by Alfven wave turbulence.
Title: Multi-stranded and Multi-thermal Solar Coronal Loops: Evidence
from Hinode X-ray Telescope and EUV Imaging Spectrometer Data
Authors: Schmelz, J. T.; Saar, S. H.; Nasraoui, K.; Kashyap, V. L.;
Weber, M. A.; DeLuca, E. E.; Golub, L.
Bibcode: 2010ApJ...723.1180S
Altcode:
Data from the X-Ray Telescope (XRT) and the EUV Imaging Spectrometer
(EIS) on the Japanese/USA/UK Hinode spacecraft were used to investigate
the spatial and thermal properties of an isolated quiescent coronal
loop. We constructed differential emission measure (DEM) curves
using Monte Carlo based, iterative forward fitting algorithms. We
studied the loop as a whole, in segments, in transverse cuts, and
point-by-point, always with some form of background subtraction, and
find that the loop DEM is neither isothermal nor extremely broad, with
approximately 96% of the EM between 6.2 <=log T<= 6.7, and an
EM-weighted temperature of log T = 6.48 ± 0.16. We find evidence for
a gradual change in temperature along the loop, with log T increasing
only by ≈0.1 from the footpoints to the peak. The combine XRT-EIS
data set does a good job of constraining the temperature distribution
for coronal loop plasma. Our studies show that the strong constraints
at high and low temperatures provided by the combined data set are
crucial for obtaining reasonable solutions. These results confirm
that the observations of at least some loops are not consistent with
isothermal plasma, and therefore cannot be modeled with a single flux
tube and must be multi-stranded.
Title: Science Objectives for an X-Ray Microcalorimeter Observing
the Sun
Authors: Laming, J. Martin; Adams, J.; Alexander, D.; Aschwanden, M;
Bailey, C.; Bandler, S.; Bookbinder, J.; Bradshaw, S.; Brickhouse,
N.; Chervenak, J.; Christe, S.; Cirtain, J.; Cranmer, S.; Deiker, S.;
DeLuca, E.; Del Zanna, G.; Dennis, B.; Doschek, G.; Eckart, M.; Fludra,
A.; Finkbeiner, F.; Grigis, P.; Harrison, R.; Ji, L.; Kankelborg,
C.; Kashyap, V.; Kelly, D.; Kelley, R.; Kilbourne, C.; Klimchuk, J.;
Ko, Y. -K.; Landi, E.; Linton, M.; Longcope, D.; Lukin, V.; Mariska,
J.; Martinez-Galarce, D.; Mason, H.; McKenzie, D.; Osten, R.; Peres,
G.; Pevtsov, A.; Porter, K. Phillips F. S.; Rabin, D.; Rakowski, C.;
Raymond, J.; Reale, F.; Reeves, K.; Sadleir, J.; Savin, D.; Schmelz,
J.; Smith, R. K.; Smith, S.; Stern, R.; Sylwester, J.; Tripathi, D.;
Ugarte-Urra, I.; Young, P.; Warren, H.; Wood, B.
Bibcode: 2010arXiv1011.4052L
Altcode:
We present the science case for a broadband X-ray imager with
high-resolution spectroscopy, including simulations of X-ray spectral
diagnostics of both active regions and solar flares. This is part of
a trilogy of white papers discussing science, instrument (Bandler et
al. 2010), and missions (Bookbinder et al. 2010) to exploit major
advances recently made in transition-edge sensor (TES) detector
technology that enable resolution better than 2 eV in an array that
can handle high count rates. Combined with a modest X-ray mirror, this
instrument would combine arcsecondscale imaging with high-resolution
spectra over a field of view sufficiently large for the study of
active regions and flares, enabling a wide range of studies such as
the detection of microheating in active regions, ion-resolved velocity
flows, and the presence of non-thermal electrons in hot plasmas. It
would also enable more direct comparisons between solar and stellar
soft X-ray spectra, a waveband in which (unusually) we currently have
much better stellar data than we do of the Sun.
Title: The Role of Magnetic Topology in the Heating of Active Region
Coronal Loops
Authors: Lee, J. -Y.; Barnes, Graham; Leka, K. D.; Reeves, Katharine
K.; Korreck, K. E.; Golub, L.; DeLuca, E. E.
Bibcode: 2010ApJ...723.1493L
Altcode: 2010arXiv1009.2070L
We investigate the evolution of coronal loop emission in the context
of the coronal magnetic field topology. New modeling techniques allow
us to investigate the magnetic field structure and energy release
in active regions (ARs). Using these models and high-resolution
multi-wavelength coronal observations from the Transition Region and
Coronal Explorer and the X-ray Telescope on Hinode, we are able to
establish a relationship between the light curves of coronal loops
and their associated magnetic topologies for NOAA AR 10963. We examine
loops that show both transient and steady emission, and we find that
loops that show many transient brightenings are located in domains
associated with a high number of separators. This topology provides
an environment for continual impulsive heating events through magnetic
reconnection at the separators. A loop with relatively constant X-ray
and EUV emission, on the other hand, is located in domains that are
not associated with separators. This result implies that larger-scale
magnetic field reconnections are not involved in heating plasma in
these regions, and the heating in these loops must come from another
mechanism, such as small-scale reconnections (i.e., nanoflares) or
wave heating. Additionally, we find that loops that undergo repeated
transient brightenings are associated with separators that have enhanced
free energy. In contrast, we find one case of an isolated transient
brightening that seems to be associated with separators with a smaller
free energy.
Title: High-spectral resolution high-cadence imaging x-ray
microcalorimeters for solar physics
Authors: Bandler, Simon R.; Bailey, Catherine N.; Bookbinder, Jay A.;
Deluca, Edward E.; Chervenak, Jay A.; Eckart, Megan E.; Finkbeiner,
Fred M.; Kelley, Daniel P.; Kelley, Richard L.; Kilbourne, Caroline
A.; Porter, Frederick S.; Sadleir, John E.; Smith, Stephen J.; Smith,
Randall K.
Bibcode: 2010SPIE.7732E..38B
Altcode: 2010SPIE.7732E.101B
High spectral resolution, high cadence, imaging x-ray spectroscopy
has the potential to revolutionize the study of the solar corona. To
that end we have been developing transition-edge-sensor (TES) based
x-ray microcalorimeter arrays for future solar physics missions
where imaging and high energy resolution spectroscopy will enable
previously impossible studies of the dynamics and energetics of the
solar corona. The characteristics of these xray microcalorimeters are
significantly different from conventional microcalorimeters developed
for astrophysics because they need to accommodate much higher count
rates (300-1000 cps) while maintaining high energy resolution of less
than 4 eV FWHM in the X-ray energy band of 0.2-10 keV. The other main
difference is a smaller pixel size (less than 75 x 75 square microns)
than is typical for x-ray microcalorimeters in order to provide
angular resolution less than 1 arcsecond. We have achieved at energy
resolution of 2.15 eV at 6 keV in a pixel with a 12 x 12 square micron
TES sensor and 34 x 34 x 9.1 micron gold absorber, and a resolution
of 2.30 eV at 6 keV in a pixel with a 35 x 35 micron TES and a 57 x
57 x 9.1 micron gold absorber. This performance has been achieved in
pixels that are fabricated directly onto solid substrates, ie. they
are not supported by silicon nitride membranes. We present the results
from these detectors, the expected performance at high count-rates,
and prospects for the use of this technology for future Solar missions.
Title: High Spectral Resolution, Imaging X-ray Microcalorimeters
for Solar Physics
Authors: Bandler, Simon; Bailey, C. N.; Bookbinder, J.; Chervenak,
J. A.; Deluca, E.; Eckart, M. E.; Finkbeiner, F. M.; Porter, F. S.;
Kilbourne, C. A.; Kelley, R. L.; Sadleir, J. E.; Smith, R. K.; Smith,
S. J.
Bibcode: 2010AAS...21640518B
Altcode: 2010BAAS...41..891B
High spectral resolution, high cadence, imaging x-ray spectroscopy
has the potential to revolutionize the study of the solar corona. To
that end we have been developing transition-edge-sensor (TES) based
x-ray microcalorimeter arrays for future solar physics missions
where imaging and high energy resolution spectroscopy will enable
previously impossible studies of the dynamics and energetics of the
solar corona. The characteristics of these x-ray microcalorimeters are
significantly different from conventional microcalorimeters developed
for astrophysics because they need to accommodate much higher count
rates ( 300-1000 cps) while maintaining high energy resolution of
less than 4 eV FWHM in the X-ray energy band of 0.2-10 keV. The other
main difference is a smaller pixel size (less than 75 microns) than
is typical for x-ray microcalorimeters in order to provide angular
resolution of less than 1 arcsecond. We have achieved at energy
resolution of 2.13 eV FWHM at 6 keV in a pixel with a 34 micron gold
absorber, and a resolution of 2.28 eV FWHM at 6 keV in a pixel with
a 57 micron gold absorber. This performance has been achieved in
pixels that are fabricated directly onto solid substrates. We will
describe these results, the characteristics of these detectors, and
the expected performance of these at high count rates. We have also
demonstrated an array heat-sinking technique that is necessary for
high-count rate operation, and shown that this heat-sinking reduces
the thermal cross-talk between pixels to an insignificant level that
is less than one part in ten thousand. This work was funded under
under NASA's ROSES program for Solar and Heliospheric Physics Research.
Title: Application of Quasi-Separatrix Layer Maps to Understanding
the Structure and Evolution of Sigmoids
Authors: Savcheva, Antonia; DeLuca, E.; Van Ballegooijen, A.
Bibcode: 2010AAS...21640522S
Altcode:
We present some preliminary work in attempt to utilize Quasi-Separatrix
Layer (QSL) maps for understanding the structure and evolution of
sigmoids. We show sample QSL maps calculated at different heights
above the photosphere and different times over the evolution of the
quiescent sigmoid from February, 2007, observed with Hinode/XRT. The
QSL maps use already existing static MHD models of the sigmoid, based
on the flux rope insertion method. We give a short overview of the
method used to set-up these maps. By comparing current distributions
and the squashing factors at different height and cross sections over
the sigmoid location we suggest the use of QSLs as tracers of surface
and/or volumetric currents. We look at the distribution, structure,
and concentration of QSLs in combination with the size and location
of bald patches at different stages of the sigmoid development. We
attempt to use this analysis to help us discriminate between the
main scenarios for the formation and X-ray appearance of the S-like
structure - flux emergence (or cancellation) and twisting foot point
motions. This method may possibly shed some light on the pre-eruption
configuration and eruption mechanism in sigmoids as well.
Title: Hot Coronal Plasma Seen by SDO/AIA and Hinode/XRT
Authors: DeLuca, Edward E.
Bibcode: 2010AAS...21640227D
Altcode: 2010BAAS...41Q.877D
The normal incidence telescopes on SDO/AIA cover coronal emission from
Fe VIII, IX, XII, XIV, XVI, XVIII, XX, XXIII, and XXIV. The grazing
incidence soft x-ray telescope on Hinode/XRT covers emission from 4-60A,
including the critical Fe XVII L-Shell emission. We will compare the
morphology and dynamics of active regions transient brightenings
seen with AIA and XRT to understand the complementarity of these
two telescopes.
Title: TRACE Observations of Changes in Coronal Hole Boundaries
Authors: Kahler, S.; Jibben, P.; DeLuca, E. E.
Bibcode: 2010SoPh..262..135K
Altcode: 2010SoPh..tmp...28K
Solar coronal holes (CHs) are large regions of the corona
magnetically open to interplanetary space. The nearly rigid north
- south CH boundaries (CHBs) of equatorward extensions of polar
CHs are maintained while the underlying photospheric fields rotate
differentially, so interchange magnetic reconnection is presumed to
be occurring continually at the CHBs. The time and size scales of the
required reconnection events at CHBs have not been established from
previous observations with soft X-ray images. We use TRACE 195 Å
observations on 9 December 2000 of a long-lived equatorial extension
of the negative-polarity north polar CH to look for changes of ≳ 5
arcsec to > 20 arcsec at the western CHB. Brightenings and dimmings
are observed on both short (≈ 5 minutes) and long (≈ 7 hours)
time scales, but the CHB maintains its quasi-rigid location. The
transient CHB changes do not appear associated with either magnetic
field enhancements or the changes in those field enhancements observed
in magnetograms from the Michelson Doppler Imager (MDI) on SOHO. In
seven hours of TRACE observations we find no examples of the energetic
jets similar to those observed to occur in magnetic reconnection in
polar plumes. The lack of dramatic changes in the diffuse CHB implies
that gradual magnetic reconnection occurs high in the corona with large
(≳ 10°) loops and/or weak coronal fields. We compare our results
with recent observations of active regions at CHBs. We also discuss
how the magnetic polarity symmetry surrounding quasi-rigid CHs implies
an asymmetry in the interchange reconnection process and a possible
asymmetry in the solar wind composition from the eastern and western
CHB source regions.
Title: Formation of Torus-Unstable Flux Ropes and Electric Currents
in Erupting Sigmoids
Authors: Aulanier, G.; Török, T.; Démoulin, P.; DeLuca, E. E.
Bibcode: 2010ApJ...708..314A
Altcode:
We analyze the physical mechanisms that form a three-dimensional
coronal flux rope and later cause its eruption. This is achieved by a
zero-β magnetohydrodynamic (MHD) simulation of an initially potential,
asymmetric bipolar field, which evolves by means of simultaneous slow
magnetic field diffusion and sub-Alfvénic, line-tied shearing motions
in the photosphere. As in similar models, flux-cancellation-driven
photospheric reconnection in a bald-patch (BP) separatrix transforms the
sheared arcades into a slowly rising and stable flux rope. A bifurcation
from a BP to a quasi-separatrix layer (QSL) topology occurs later on in
the evolution, while the flux rope keeps growing and slowly rising,
now due to shear-driven coronal slip-running reconnection, which
is of tether-cutting type and takes place in the QSL. As the flux
rope reaches the altitude at which the decay index -∂ln B/∂ln z
of the potential field exceeds ~3/2, it rapidly accelerates upward,
while the overlying arcade eventually develops an inverse tear-drop
shape, as observed in coronal mass ejections (CMEs). This transition
to eruption is in accordance with the onset criterion of the torus
instability. Thus, we find that photospheric flux-cancellation and
tether-cutting coronal reconnection do not trigger CMEs in bipolar
magnetic fields, but are key pre-eruptive mechanisms for flux ropes to
build up and to rise to the critical height above the photosphere at
which the torus instability causes the eruption. In order to interpret
recent Hinode X-Ray Telescope observations of an erupting sigmoid, we
produce simplified synthetic soft X-ray images from the distribution
of the electric currents in the simulation. We find that a bright
sigmoidal envelope is formed by pairs of J-shaped field lines in the
pre-eruptive stage. These field lines form through the BP reconnection
and merge later on into S-shaped loops through the tether-cutting
reconnection. During the eruption, the central part of the sigmoid
brightens due to the formation of a vertical current layer in the wake
of the erupting flux rope. Slip-running reconnection in this layer
yields the formation of flare loops. A rapid decrease of currents due
to field line expansion, together with the increase of narrow currents
in the reconnecting QSL, yields the sigmoid hooks to thin in the early
stages of the eruption. Finally, a slightly rotating erupting loop-like
feature (ELLF) detaches from the center of the sigmoid. Most of this
ELLF is not associated with the erupting flux rope, but with a current
shell that develops within expanding field lines above the rope. Only
the short, curved end of the ELLF corresponds to a part of the flux
rope. We argue that the features found in the simulation are generic
for the formation and eruption of soft X-ray sigmoids.
Title: Magnetic Flux Rope Eruption: Non Equilibrium versus Torus
Instability
Authors: Demoulin, Pascal; Aulanier, Guillaume; Toeroek, Tibor;
Deluca, Edward
Bibcode: 2010cosp...38.1855D
Altcode: 2010cosp.meet.1855D
The coronal magnetic configuration of an active region typically
evolves quietly during few days before becoming suddenly eruptive
and launching a CME. The precise origin of the eruption is still
debated. Among other mechanisms, it has been long proposed that a
loss of equilibrium, or an ideal MHD instability such as the torus
instability, could be responsible for the sudden eruptivity. We first
revisit both approaches with simple analytical models as well as with
a 3D MHD simulation of an initially potential bipolar field, which
evolves by means of simultaneous slow magnetic field diffusion and
shearing motions in the photosphere. Reconnection of sheared arcade
leads to the formation of a twisted flux rope, which corresponds to an
electric current channel. We find that the electric current distribution
and the field-line organization present in the MHD simulation provide
an explanation for the recent X-rays Hinode observations of erupting
sigmoidal regions. Next, we show analytically that the loss of
equilibrium and the torus instability are two different views of the
same physical mechanism. We compare the instability thresholds in the
limit of straight and circular current channels, finding that they are
closely comparable for thick current channels (as present in the MHD
simulation and as expected in the corona) while these thresholds are
well distinct at the limit of very thin current channels (as typically
found in previous studies). Finally, including photospheric line tying
of the current channel in the analytical models permits to have a
closer comparison between instability thresholds found analytically
and by the MHD simulation.
Title: Dynamical Evolution of X-Ray Bright Points with Hinode/XRT
Authors: Kariyappa, R.; Varghese, B. A.; DeLuca, E. E.; van
Ballegooijen, A. A.
Bibcode: 2010ASSP...19..440K
Altcode: 2010mcia.conf..440K
We analyzed a 7-h long time sequence of soft X-ray images obtained
on 14 April 2007 from a quiet region using the X-Ray Telescope (XRT)
onboard Hinode. The aim was to observe intensity oscillations in
coronal XBPs of different brightness and to study differences, if
any, in the periodicity of the intensity variations and the heating
mechanism during their dynamical evolution. We have compared the XRT
images with GONG magnetograms using Coronal Modeling Software (CMS),
and found that some of the XBPs are located at magnetic bipoles. The
coronal XBPs are highly dynamic and oscillatory in nature, showing a
wide variety of time scales in their intensity variations.
Title: Examining the Effect of Local Magnetic Field on Coronal Bright
Point Heating and Evolution
Authors: Farid, S.; Saar, S.; Govindan, R.; Deluca, E.
Bibcode: 2009ASPC..415...15F
Altcode: 2010arXiv1001.3241F
We investigate the effect of the local magnetic field on the
evolution and heating of coronal bright points (BPs) by examining a
BP in a coronal hole and a BP in the nearby quiet sun. We attempt to
discriminate the heating source of BPs by correlating fluctuations in
emission in TRACE 171 Å images, to changes in the unsigned magnetic
flux of the associated bipolar region using GONG magnetograms, and
potential field extrapolations. We confirm that changes in emission of
the larger, quiet-sun bright point can be correlated to fluctuations in
the total unsigned magnetic flux as predicted by previous studies. The
quiet sun BP also appears to have a potential magnetic configuration
over the observation period. However changes in emission in the smaller,
coronal hole bright point appears to be less correlated to changes
in the bipolar region. We also could not reproduce a potential-like
extrapolation at any time during the observation period, possibly
indicating the CH bright point may be non-potential.
Title: Coronal Loop Temperatures Obtained with Hinode XRT: A
Toothpaste-Tube Analogy
Authors: Schmelz, J. T.; Saar, S. H.; Weber, M. A.; Deluca, E. E.;
Golub, L.
Bibcode: 2009ASPC..415..299S
Altcode:
Multi-filter data observed by the Hinode X-Ray Telescope on 10 and
2007 July 13 were used to investigate the thermal properties of
coronal loops. At several positions along the loops, differential
emission measure analysis revealed a strong peak at log T = 6.1 (which
would predict the presence of a TRACE loop) and a much weaker hot
component (which we speculated might be a nanoflare signature). TRACE
observations, however, did not reveal the predicted loop, so we were
forced to re-examine our assumptions. Good differential emission measure
results require high- and low-temperature constraints, but our data sets
did not contain images from the thinnest and thickest filters, which
would be most likely to provide these constraints. Since differential
emission measure programs aim to match observed intensities and get
low values of χ2, they may place emission measure in high-
and low-temperature bins where it does not belong. We draw an analogy to
squeezing the toothpaste tube in the middle. Our analysis was repeated
for a loop observed on 2007 May 13 when the instrument acquired data
in 11 filters and filter combinations, including both the thinnest and
thickest filters. These results show that the loop is multi-thermal,
with significant emission measure in the range 6.0 < log T < 6.5.
Title: Does a Polar Coronal Hole's Flux Emergence Follow a Hale-Like
Law?
Authors: Savcheva, A.; Cirtain, J. W.; DeLuca, E. E.; Golub, L.
Bibcode: 2009ApJ...702L..32S
Altcode:
Recent increases in spatial and temporal resolution for solar telescopes
sensitive to EUV and X-ray radiation have revealed the prevalence of
transient jet events in polar coronal holes. Using data collected by the
X-Ray Telescope on Hinode, Savcheva et al. confirmed the observation,
made first by the Soft X-ray Telescope on Yohkoh, that some jets exhibit
a motion transverse to the jet outflow direction. The velocity of this
transverse motion is, on average, 10 km s-1. The direction
of the transverse motion, in combination with the standard reconnection
model for jet production (e.g., Shibata et al.), reflects the magnetic
polarity orientation of the ephemeral active region at the base of
the jet. From this signature, we find that during the present minimum
phase of the solar cycle the jet-base ephemeral active regions in the
polar coronal holes had a preferred east-west direction, and that this
direction reversed during the cycle's progression through minimum. In
late 2006 and early 2007, the preferred direction was that of the active
regions of the coming sunspot cycle (cycle 24), but in late 2008 and
early 2009 the preferred direction has been that of the active regions
of sunspot cycle 25. These findings are consistent with the observations
of Wilson et al. suggesting that each cycle of solar activity begins
at polar latitudes soon after the onset of the previous cycle.
Title: Detection of a Preferred Direction of Polar-Latitude Magnetic
Bipoles via the Reconnection Bright Point in X-Ray Jets
Authors: Stern, Julie; Cirtain, J.; Falconer, D.; Moore, R.; DeLuca, E.
Bibcode: 2009SPD....40.1304S
Altcode:
Martin and Harvey (1979, Sol. Phys. 64, 93) found that during the
solar minimum between Cycles 20 and 21 ephemeral active regions
at high latitudes (55-65 degrees) showed a definite preference for
the east-west magnetic direction expected from Hale's Law for the
active regions of the coming solar cycle. In the present study, we use
Hinode X-Ray Telescope movies of X-ray jets observed in and around the
polar coronal holes to examine whether the magnetic bipoles at polar
latitudes (> 60 degrees) during the present Cycle 23-24 minimum
display any preference in their east-west direction. The particular
feature of an X-ray jet that we use to detect the magnetic direction
of the magnetic bipole spanning the base of the jet is the smaller
bright-point bipole produced at one end of the jet-base bipole by the
jet-producing reconnection with the surrounding high-reaching background
field in and around the coronal hole (a la Shibata et al 1992, PASJ,
44, L173). For any jet-producing bipole that has an obvious east-west
component to its direction, the east-west magnetic direction of the
bipole is deduced from the polarity of the polar-cap background field
and whether the reconnection bright point is on the east or west end
of the jet-base bipole. For an initial collection of about 100 polar
jets, observed in late 2006 and early 2007 and produced by bipoles
having obvious east-west inclination, we find that a majority ( 60%)
of the bipoles had the east-west direction expected from Hale's Law
for the coming solar cycle (Cycle 24). We can use this method to see
if this direction preference at polar latitudes changes as Cycle 24
progresses. This work was supported by the NASA/MSFC Undergraduate
Student Research Program and by NASA's Heliophysics Division through
the Hinode Mission and the Heliophysics Guest Investigators Program.
Title: The Off-Axis Properties of the Hinode X-Ray Telescope (XRT):
I. Vignetting Effect
Authors: Shin, Junho; Martens, P. C. H.; Golub, L.; Deluca, E. E.
Bibcode: 2009SPD....40.1804S
Altcode:
The X-Ray Telescope (XRT) aboard Hinode has observed a variety
of coronal structures in the range of 34x34 arc min field-of-view
(FOV) covering the full solar disk. In general, most astronomical
telescopes are designed such that the best-focused image of an object
can be achieved at or close to the on-axis position, and the optical
performance varies systematically across the FOV. The Sun is, however,
a large object whose size is about 30 arc min and coronal structures
are observed not only at the disc center but also near the limb. For
this reason, the optical structure of solar telescopes should be
designed with care for improving the uniformity of the angular
resolution over the full FOV. Since there is no unique solution for
successfully implementing this kind of off-axis variation, the optical
properties of the XRT have been examined using the data from the ground
experiments as well as from in-flight observations for the calibration
of systematic variations in the FOV. The vignetting effect is an
important optical characteristic for describing the performance of
the telescope, which reflects the ability to collect incoming light
at different locations and different photon energies. Especially,
the determination of this vignetting effect is one of the essential
calibration steps that should be performed before the observed images
are used for any scientific purposes. Because a component of the
XRT vignetting effect shows a wavelength dependence, special care
should be taken when, for example, performing temperature analyses
with thin and thick filters of flares occurring near the solar
limb. In this presentation, we introduce the results of analysis of
pre-launch calibration data obtained from MSFC/XRCF experiments. The
two-dimensional off-axis variation of the XRT point spread function
(PSF) and its energy dependence will be discussed in detail.
Title: Hinode X-Ray Telescope Detection of Hot Emission from Quiescent
Active Regions: A Nanoflare Signature?
Authors: Schmelz, J. T.; Saar, S. H.; DeLuca, E. E.; Golub, L.;
Kashyap, V. L.; Weber, M. A.; Klimchuk, J. A.
Bibcode: 2009ApJ...693L.131S
Altcode: 2009arXiv0901.3122S
The X-Ray Telescope (XRT) on the Japanese/USA/UK Hinode (Solar-B)
spacecraft has detected emission from a quiescent active region
core that is consistent with nanoflare heating. The fluxes from 10
broadband X-ray filters and filter combinations were used to construct
differential emission measure (DEM) curves. In addition to the expected
active region peak at log T = 6.3-6.5, we find a high-temperature
component with significant emission measure at log T > 7.0. This
emission measure is weak compared to the main peak—the DEM is down
by almost three orders of magnitude—which accounts of the fact
that it has not been observed with earlier instruments. It is also
consistent with spectra of quiescent active regions: no Fe XIX lines
are observed in a CHIANTI synthetic spectrum generated using the XRT
DEM distribution. The DEM result is successfully reproduced with a
simple two-component nanoflare model.
Title: Thermal And Statistical Properties of X-ray Bright Points
Authors: Saar, S.; Farid, S.; Deluca, E.
Bibcode: 2009AIPC.1094..756S
Altcode: 2009csss...15..756S
HINODE's X-ray Telescope (XRT) offers a unique combination of
high spatial (~2'') and thermal resolution, full-Sun observations
of the solar corona over a wide range of temperatures (5.8~<log
T~<7.6). We use multi-filter Hinode/XRT data to explore the thermal,
statistical and spatial properties of X-ray bright points (XBPs). We
have developed an automated XBP finder to study BPs over two periods
during November 2007 and May 2008. We detect somewhat fewer XBPs than
SOHO EIT in 195 Å but find comparable values to the 284 Å band. This
is likely due in some part to the somewhat stricter requirements on XBP
shape and enhancement above local background that we have adopted. We
find that most XBPs appear to be relatively cool on average (log T~6.1),
only slightly hotter than the average quiet Sun. There is a trend for
larger XBPs to be hotter, with a sub-class of XBPs which are hotter
still at all sizes. We further investigate the spatial distribution
of XBPs, in particular exploring whether the ``overhot'' XBPs have
any tendency to appear in or near coronal holes. We find that there
appears to be a notable trend of overhot bright points within the two
data sets and a tendency of those to lie within 40'' of coronal holes.
Title: On the Structure and Evolution of Complexity in Sigmoids:
A Flux Emergence Model
Authors: Archontis, V.; Hood, A. W.; Savcheva, A.; Golub, L.;
Deluca, E.
Bibcode: 2009ApJ...691.1276A
Altcode:
Sigmoids are structures with a forward or inverse S-shape, generally
observed in the solar corona in soft X-ray emission. It is believed that
the appearance of a sigmoid in an active region is an important factor
in eruptive activity. The association of sigmoids with dynamic phenomena
such as flares and coronal mass ejections (CMEs) make the study of
sigmoids important. Recent observations of a coronal sigmoid, obtained
with the X-Ray Telescope (XRT) on board Hinode, showed the formation
and eruption phase with high spatial resolution. These observations
revealed that the topological structure of the sigmoid is complex:
it consists of many differently oriented loops that all together
form two opposite J-like bundles or an overall S-shaped structure. A
series of theoretical and numerical models have been proposed, over
the past years, to explain the nature of sigmoids but there is no
explanation on how the aforementioned complexity in sigmoids is built
up. In this paper, we present a flux emergence model that leads to the
formation of a sigmoid, whose structure and evolution of complexity
are in good qualitative agreement with the recent observations. For
the initial state of the experiment a twisted flux tube is placed
below the photosphere. A density deficit along the axis of the tube
makes the system buoyant in the middle and it adopts an Ω-shape as it
rises toward the outer atmosphere. During the evolution of the system,
expanding field lines that touch the photosphere at bald-patches (BPs)
form two seperatrix surfaces where dissipation is enhanced and current
sheets are formed. Originally, each of the BP seperatrix surfaces
has a J-like shape. Each one of the J's consist of reconnected field
lines with different shapes and different relative orientation. The
further dynamical evolution of the emerging flux tube results in the
occurrence of many sites that resemble rotational discontinuities. Thus,
additional current layers are formed inside the rising magnetized volume
increasing the complexity of the system. The reconnected field lines
along these layers form an overall S-shaped structure. The reconnection
process continues to occur leading to the formation of another current
concentration in the middle of the sigmoid where a flaring episode
occurs. This central brightening is accompanied by the eruption of a
flux rope from the central area of the sigmoid and the appearance of
"post-flare" loops underneath the current structure.
Title: Are Coronal Loops Isothermal or Multithermal?
Authors: Schmelz, J. T.; Nasraoui, K.; Rightmire, L. A.; Kimble,
J. A.; del Zanna, G.; Cirtain, J. W.; DeLuca, E. E.; Mason, H. E.
Bibcode: 2009ApJ...691..503S
Altcode: 2009arXiv0901.3281S
Surprisingly few solar coronal loops have been observed simultaneously
with TRACE and SOHO/Coronal Diagnostics Spectrometer (CDS), and even
fewer analyses of these loops have been conducted and published. The
SOHO Joint Observing Program 146 was designed in part to provide the
simultaneous observations required for in-depth temperature analysis of
active region loops and determine whether these loops are isothermal
or multithermal. The data analyzed in this paper were taken on 2003
January 17 of AR 10250. We used TRACE filter ratios, emission measure
loci, and two methods of differential emission measure analysis to
examine the temperature structure of three different loops. TRACE and
CDS observations agree that Loop 1 is isothermal with log T = 5.85,
both along the line of sight as well as along the length of the loop
leg that is visible in the CDS field of view. Loop 2 is hotter than
Loop 1. It is multithermal along the line of sight, with significant
emission between 6.2 < log T< 6.4, but the loop apex region
is out of the CDS field of view so it is not possible to determine
the temperature distribution as a function of the loop height. Loop
3 also appears to be multithermal, but a blended loop that is just
barely resolved with CDS may be adding cool emission to the Loop
3 intensities and complicating our results. So, are coronal loops
isothermal or multithermal? The answer appears to be yes.
Title: Observations and Nonlinear Force-Free Field Modeling of Active
Region 10953
Authors: Su, Yingna; van Ballegooijen, Adriaan; Lites, Bruce W.;
Deluca, Edward E.; Golub, Leon; Grigis, Paolo C.; Huang, Guangli;
Ji, Haisheng
Bibcode: 2009ApJ...691..105S
Altcode:
We present multiwavelength observations of a simple bipolar active
region (NOAA 10953), which produced several small flares (mostly B class
and one C8.5 class) and filament activations from April 30 to May 3 in
2007. We also explore nonlinear force-free field (NLFFF) modeling of
this region prior to the C8.5 flare on May 2, using magnetograph data
from SOHO/MDI and Hinode/SOT. A series of NLFFF models are constructed
using the flux-rope insertion method. By comparing the modeled field
lines with multiple X-ray loops observed by Hinode/XRT, we find that
the axial flux of the flux rope in the best-fit models is (7± 2)×
1020 Mx, while the poloidal flux has a wider range of
(0.1-10)× 1010 Mx cm-1. The axial flux in the
best-fit model is well below the upper limit (~15× 1020
Mx) for stable force-free configurations, which is consistent with the
fact that no successful full filament eruption occurred in this active
region. From multiwavelength observations of the C8.5 flare, we find
that the X-ray brightenings (in both RHESSI and XRT) appeared about 20
minutes earlier than the EUV brightenings seen in TRACE 171 Å images
and filament activations seen in MLSO Hα images. This is interpreted as
an indication that the X-ray emission may be caused by direct coronal
heating due to reconnection, and the energy transported down to the
chromosphere may be too low to produce EUV brightenings. This flare
started from nearly unsheared flare loop, unlike most two-ribbon flares
that begin with highly sheared footpoint brightenings. By comparing
with our NLFFF model, we find that the early flare loop is located
above the flux rope that has a sharp boundary. We suggest that this
flare started near the outer edge of the flux rope, not at the inner
side or at the bottom as in the standard two-ribbon flare model.
Title: Plasma Outflows in the Corona as Observed With Hinode XRT
Authors: Sakao, T.; Kano, R.; Narukage, N.; Deluca, E. E.; Grigis, P.
Bibcode: 2008AGUFMSH41B1624S
Altcode:
We present imaging observations of plasma outflows in the solar corona
made with X-Ray Telescope (XRT) aboard Hinode satellite. The XRT employs
a back-illuminated CCD as the focal-plane imaging device which enables
us, together with an optimized set of analysis filters, to investigate,
for the first time, dynamic behavior of relatively cool (1-2 MK, say)
plasmas in the corona. The XRT revealed a clear pattern of continuous
outflow of plasmas from the edge of an active region NOAA AR 10942 right
adjacent to a coronal hole. Plasmas of temperature ~1 MK flowed out
with a sub-sonic velocity of typically ~140 km/s along magnetic field
lines that are most likely open towards the interplanetary space. These
outflowing plasmas may constitute a fraction of the (slow) solar
wind. In addition to this discovery, the XRT has so far identified
rich patterns of continuous outflows including those from coronal
hole boundaries and along fan-like field lines rooted inside coronal
holes. XRT observations of such plasma outflows in the corona are
presented and their possible implications to the solar wind discussed.
Title: Observations and analysis of the April 9, 2008 CME using
STEREO, Hinode TRACE and SoHO data
Authors: Reeves, K. K.; Patsourakos, S.; Stenborg, G.; Miralles, M.;
Deluca, E.; Forbes, T.; Golub, L.; Kasper, J.; Landi, E.; McKenzie,
D.; Narukage, N.; Raymond, J.; Savage, S.; Su, Y.; van Ballegooijen,
A.; Vourlidas, A.; Webb, D.
Bibcode: 2008AGUFMSH12A..04R
Altcode:
On April 9, 2008 a CME originating from an active region behind the limb
was well-observed by STEREO, Hinode, TRACE and SoHO. Several interesting
features connected to this eruption were observed. (1) The interaction
of the CME with open field lines from a nearby coronal hole appeared
to cause an abrupt change in the direction of the CME ejecta. (2) The
prominence material was heated, as evidenced by a change from absorption
to emission in the EUV wavelengths. (3) Because the active region was
behind the limb, the X-Ray Telescope on Hinode was able to take long
enough exposure times to observe a faint current- sheet like structure,
and it was able to monitor the dynamics of the plasma surrounding this
structure. This event is also being studied in the context of activity
that occurred during the Whole Heliosphere Interval (WHI).
Title: Hinode, TRACE, SOHO, and Ground-based Observations of a
Quiescent Prominence
Authors: Heinzel, P.; Schmieder, B.; Fárník, F.; Schwartz, P.;
Labrosse, N.; Kotrč, P.; Anzer, U.; Molodij, G.; Berlicki, A.;
DeLuca, E. E.; Golub, L.; Watanabe, T.; Berger, T.
Bibcode: 2008ApJ...686.1383H
Altcode:
A quiescent prominence was observed by several instruments on
2007 April 25. The temporal evolution was recorded in Hα by the
Hinode SOT, in X-rays by the Hinode XRT, and in the 195 Å channel by
TRACE. Moreover, ground-based observatories (GBOs) provided calibrated
Hα intensities. Simultaneous extreme-UV (EUV) data were also taken by
the Hinode EIS and SOHO SUMER and CDS instruments. Here we have selected
the SOT Hα image taken at 13:19 UT, which nicely shows the prominence
fine structure. We compare this image with cotemporaneous ones taken
by the XRT and TRACE and show the intensity variations along several
cuts parallel to the solar limb. EIS spectra were obtained about half
an hour later. Dark prominence structure clearly seen in the TRACE and
EIS 195 Å images is due to the prominence absorption in H I, He I,
and He II resonance continua plus the coronal emissivity blocking due
to the prominence void (cavity). The void clearly visible in the XRT
images is entirely due to X-ray emissivity blocking. We use TRACE, EIS,
and XRT data to estimate the amount of absorption and blocking. The
Hα integrated intensities independently provide us with an estimate of
the Hα opacity, which is related to the opacity of resonance continua
as follows from the non-LTE radiative-transfer modeling. However,
spatial averaging of the Hα and EUV data have quite different natures,
which must be taken into account when evaluating the true opacities. We
demonstrate this important effect here for the first time. Finally,
based on this multiwavelength analysis, we discuss the determination
of the column densities and the ionization degree of hydrogen in
the prominence.
Title: DEM Temperature Analysis of Eruptive Events Using the XRT
on Hinode
Authors: Reeves, K. K.; Weber, M. A.; Kashyap, V.; Deluca, E. E.
Bibcode: 2008ASPC..397..187R
Altcode:
The X-Ray Telescope (XRT) on Hinode has unprecedented temperature
coverage with 9 X-Ray filters in the focal plane. This temperature
coverage is especially useful in determining the temperatures of
flaring plasma. In this work, we use DEM techniques to analyze the
temperature structures in some small eruptive events.
Title: Physical Conditions in Coronal Structures About to Flare
Authors: Hudson, H. S.; Hannah, I. G.; Deluca, E. E.; Weber, M.
Bibcode: 2008ASPC..397..130H
Altcode:
We use Hinode observations to study coronal structures about to flare,
based on their apparent footpoints as a guide to identification. The
high resolution and excellent stability of the Hinode observations
makes the identifications much more precise than those done with the
soft X-ray telescope (SXT) on board Yohkoh. The physical conditions in
the coronal structure about to flare are important in understanding
the nature of the plasma processes leading to the eruption. We find
examples of soft X-ray microflares that agree with the SXT conclusions:
the structure is essentially invisible prior to the flare in most
cases. We present an estimation of preflare temperature and density
and find that in these cases, the flare appears to happen in flux tubes
with undetectably low electron density, less than ∼10^{8} cm^{-3}. A
similar program with the full instrument set of Hinode would be
extremely powerful, owing to the broad temperature coverage available.
Title: Vertical Temperature Structures of the Solar Corona Derived
with the Hinode X-Ray Telescope
Authors: Kano, Ryouhei; Sakao, Taro; Narukage, Noriyuki; Tsuneta,
Saku; Kotoku, Jun'ichi; Bando, Takamasa; Deluca, Edward; Lundquist,
Loraine; Golub, Leon; Hara, Hirohisa; Matsuzaki, Keiichi; Shimojo,
Masumi; Shibasaki, Kiyoto; Shimizu, Toshifumi; Nakatani, Ichiro
Bibcode: 2008PASJ...60..827K
Altcode:
We obtained temperature structures in faint coronal features
above and near the solar limb with the X-Ray Telescope aboard the
Hinode satellite by accurately correcting the scattered X-rays
from surrounding bright regions with occulted images during
the solar eclipses. Our analysis yields a polar coronal hole
temperature of about 1.0MK and an emission measure in the range of
1025.5-1026.0cm-5. In addition,
our methods allow us to measure the temperature and emission
measure of two distinct quiet-Sun structures: radial (plume-like)
structures near the boundary of the coronal-hole and diffuse quiet
Sun regions at mid-latitudes. The radial structures appear to have
increasing temperature with height during the first 100Mm, and
constant temperatures above 100Mm. For the diffuse quiet-Sun region
the temperatures are the highest just above the limb, and appear
to decrease with height. These differences may be due to different
magnetic configurations.
Title: The Hinode X-Ray Telescope (XRT): Camera Design, Performance
and Operations
Authors: Kano, R.; Sakao, T.; Hara, H.; Tsuneta, S.; Matsuzaki, K.;
Kumagai, K.; Shimojo, M.; Minesugi, K.; Shibasaki, K.; DeLuca, E. E.;
Golub, L.; Bookbinder, J.; Caldwell, D.; Cheimets, P.; Cirtain, J.;
Dennis, E.; Kent, T.; Weber, M.
Bibcode: 2008SoPh..249..263K
Altcode:
The X-ray Telescope (XRT) aboard the Hinode satellite is a grazing
incidence X-ray imager equipped with a 2048×2048 CCD. The XRT has
1 arcsec pixels with a wide field of view of 34×34 arcmin. It is
sensitive to plasmas with a wide temperature range from < 1 to 30
MK, allowing us to obtain TRACE-like low-temperature images as well as
Yohkoh/SXT-like high-temperature images. The spacecraft Mission Data
Processor (MDP) controls the XRT through sequence tables with versatile
autonomous functions such as exposure control, region-of-interest
tracking, flare detection, and flare location identification. Data are
compressed either with DPCM or JPEG, depending on the purpose. This
results in higher cadence and/or wider field of view for a given
telemetry bandwidth. With a focus adjust mechanism, a higher resolution
of Gaussian focus may be available on-axis. This paper follows the
first instrument paper for the XRT (Golub et al., Solar Phys.243, 63,
2007) and discusses the design and measured performance of the X-ray
CCD camera for the XRT and its control system with the MDP.
Title: A search for oscillating loops in Solar-B XRT observations
Authors: Savcheva, Antonia; DeLuca, Edward
Bibcode: 2008IAUS..247..147S
Altcode: 2007IAUS..247..147S
Between November 2006 and March 2007, on several occasions, XRT has
been taking high-cadence one or two filter observations of prominent
active regions on the disk. We took these datasets and conducted a quick
search for acoustic brightness oscillation in loops. We concentrated
our search on flaring active regions. Here we present the preliminary
results of this search. We found one active region - NOAA 10953 from 27
April - 02 May 2007 that had indications of acoustic oscillations with
periods around 5 min, as well as multiples of this period, and one 40
min period that we associate with periodic heating of the loops. An
interesting result is that all the loops in the active region seemed
to oscillate with the same set of periods, only the power in the FFT
was different and maybe dependent on the magnetic field strength.
Title: The Analysis of Hinode/XRT Observations
Authors: Deluca, E. E.; Weber, M.; Savcheva, A.; Saar, S.; Testa,
P.; Cirtain, J. W.; Sakao, T.; Noriyuki, N.; Kano, R.; Shimizu, T.
Bibcode: 2008AGUSMSP51B..02D
Altcode:
This poster will present the current state of Hinode/XRT analysis
software. We will give an overview of the XRT Analysis Guide. We will
include a detailed discussion of the following topics: Co-alignment
with SOT and EIS Spot removal for dynamics studies Filter calibration
for thermal studies Dark calibrations Sample data sets will be
discussed and links to the data products will be provided.
Title: Observations and NLFFF Modeling of Active Region 10953
Authors: Su, Y.; van Ballegooijen, A.; Golub, L.; Deluca, E.
Bibcode: 2008AGUSMSP43C..07S
Altcode:
We explored the non-linear force free field (NLFFF) modeling of a
simple bipolar active region (NOAA 10953), which produced several small
flares (mostly B class and one C8.5 class) and filament activations
from April 30 to May 3 in 2007. These events appear to be associated
with the frequent flux cancellations (SOHO/MDI) that occurred in the
region close to the polarity inversion line. Some preliminary results
of multi-wavelength observations of a C8.5 flare that occurred on May
2 will be presented. We constructed a series of NLFFF models for this
active region at three times, using the flux-rope insertion method. The
models are constructed based on MDI magnetograms, and constrained by
Hα filaments and highly sheared loops observed by XRT aboard Hinode. We
find good NLFFF models that fit the observations before the C8.5 flare,
but not for the case after the flare. The flux rope contains highly
sheared but weakly twisted magnetic fields. Before the C8.5 flare,
this active region is close to an eruptiveon state: the axial flux in
the flux rope is close to the upper limit for instability.
Title: Searching the X-ray Sun For Solar Axions
Authors: Hudson, Hugh S.; Acton, L. W.; DeLuca, E. E.; Hannah, I. G.;
Hurford, G. J.; Lin, R. P.; Reardon, K. P.; van Bibber, K.
Bibcode: 2008AAS...212.0402H
Altcode: 2008BAAS...40..193H
The axion is a hypothetical weakly-interacting elementary particle. The
solar core may produce a copious axion flux via the Primakoff
effect. This same process can also convert a tiny fraction of the
axions back into photons via interaction with the magnetic field
threading the solar atmosphere. The spectral signature of the emitted
X-rays is determined mainly by the temperature of the solar core, and
the spatial distribution also depends strongly on the solar magnetic
field in the back-conversion process. The X-ray intensity thus varies as
Gaγγ(∫BperpdL)2,
where Bperp is the perpendicular component of the
chromospheric and coronal magnetic field in the appropriate zone
for interaction and photon escape, and Gaγγ
is the (unknown) coupling constant, dependent on the (unknown) mass
of the axion. We describe observational tests suitable for solar
X-ray imagers and discuss projects now under way with Yohkoh/SXT,
RHESSI, and Hinode/XRT. The successful detection of axions would have
implications for basic physics and for cosmological dark matter. It
would also help us to characterize the ill-understood extension of the
solar magnetic field into the chromosphere and corona. We specifically
focus on applying the existing understanding of solar (and stellar)
magnetism to this problem.
Title: Modeling Nonpotential Magnetic Fields in Solar Active Regions
Authors: Bobra, M. G.; van Ballegooijen, A. A.; DeLuca, E. E.
Bibcode: 2008ApJ...672.1209B
Altcode:
Electric currents are present in the coronae above solar active regions,
producing nonpotential magnetic fields that can be approximated as
nonlinear force-free fields (NLFFFs). In this paper NLFFF models for
two active regions observed in 2002 June are presented. The models are
based on magnetograms from SOHO MDI and are constrained by nonpotential
structures seen in BBSO Hα images and TRACE EUV images. The models are
constructed using the flux rope insertion method. We find that the axial
fluxes of the flux ropes are well constrained by the observations. The
flux ropes are only weakly twisted, and electric currents flow mainly at
the interface between the flux rope and its surroundings. In one case,
the flux rope is anchored with both ends in the active region; in the
other case, the flux rope extends to the neighboring quiet Sun. We
find that the magnetic fields in these active regions are close to
an eruptive state: the axial flux in the flux ropes is close to the
upper limit for eruption. We also derive estimates for magnetic free
energy and helicity in these regions.
Title: Coronal soft X-ray activity in the quiet Sun
Authors: Grigis, Paolo; Golub, Leon; Deluca, Edward
Bibcode: 2008cosp...37.1077G
Altcode: 2008cosp.meet.1077G
Small scale coronal activity in the quiet Sun is continuous, ubiquitous
and driven by magnetic fields. Typical manifestations of this activity
are seen in the form of brightenings in X-ray bright points, network
flares, nanoflares. We present high-cadence Hinode/XRT soft X-ray
observations of the quiet Sun corona and a statistical analysis of
its variability on short timescales (minutes to hours). We explore
the connection between this coronal activity (as mapped from the soft
X-ray image sequences) and the underlying magnetic field structures.
Title: Observations and NLFFF modeling of active region 10953
Authors: Su, Yingna; van Ballegooijen, Adriaan; Golub, Leon; Deluca,
Edward
Bibcode: 2008cosp...37.3075S
Altcode: 2008cosp.meet.3075S
We explore the non-linear force free field (NLFFF) modeling of a simple
bipolar active region (NOAA 10953), which produced several small
flares (mostly B class and one C8.5 class) and filament activations
from April 30 to May 3 in 2007. These events appear to be associated
with the frequent flux cancellations (SOHO/MDI) that occurred in the
region close to the polarity inversion line. Some preliminary results
of multi-wavelength observations of a C8.5 flare that occurred on May
2 will be presented. We constructed a series of NLFFF models for this
active region at three times, using the flux-rope insertion method. The
models are constructed based on MDI magnetograms, and constrained by
Hα filaments and highly sheared loops observed by XRT aboard Hinode. We
find good NLFFF models that fit the observations before the C8.5 flare,
but not for the case after the flare. The flux rope contains highly
sheared but weakly twisted magnetic fields. Before the C8.5 flare,
this active region is close to an eruptive state: the axial flux in
the flux rope is close to the upper limit for instability.
Title: Magnetic Evolution of X-Ray Bright Points
Authors: Deluca, Edward; van Ballegooijen, Adriaan; Harvey, Jack
Bibcode: 2008cosp...37..690D
Altcode: 2008cosp.meet..690D
The evolution of magnetic structures that form X-Ray Bright Points will
be studied using local high resolution potential field extrapolations
of GONG magnetograph observations. The relationship between the X-ray
structures seen in Hinode/XRT and the magnetic structures will be
discussed.
Title: Cross calibration of soft X-ray telescopes between Hinode/XRT
and GOES13/SXI
Authors: Narukage, N.; Sakao, T.; Kano, R.; Shimojo, M.; Cirtain,
J.; Deluca, E.; Nitta, N.; Lemen, J.
Bibcode: 2007AGUFMSH53A1050N
Altcode:
The X-Ray Telescope (XRT) aboard Hinode satellite is a grazing
incidence telescope to observe all the coronal features with a wide
temperature range from less than 1MK to more than 10MK. And the XRT
has 9 X-ray analysis filters which are optimized to observed the
almost whole coronal plasma and to derived the coronal temperature
distribution. Meanwhile, the GOES13 satellite carries a Solar X-ray
Imager (SXI) to monitor the solar X-rays. The SXI is also a grazing
incidence telescope and has 7 X-ray filters. The XRT and SXI are
similar telescopes to observe the dynamic solar corona. On 24 Nov 2006,
the XRT and SXI-team performed the simultaneous observation for the
cross calibration between XRT and SXI. In this study, we analyzed
this data set and checked the actual characteristics of each X-ray
analysis filter.
Title: X-ray Microflares with Hinode and RHESSI.
Authors: Hannah, I. G.; Christe, S.; Krucker, S.; Hudson, H.; Lin,
R. P.; Deluca, E.
Bibcode: 2007AGUFMSH52C..07H
Altcode:
We present analysis of microflares (small active region associated
flares below GOES C class) using RHESSI and Hinode/XRT. RHESSI has
observed well over 1,000 microflares since Hinode launched late in 2006
and of these over 150 have good Hinode/XRT coverage. We use RHESSI to
obtain the temperature, emission measure and non-thermal power-law
parameters from spectral fitting. We compare RHESSI and Hinode/XRT
images to locate the thermal and non-thermal emissions. Taking advantage
of the sensitive high-resolution capability of XRT for the softer
X-rays, we investigate the resulting heating and evaporation from the
accelerated electrons observed via the non-thermal emission by RHESSI.
Title: The Differential Emission Measure and Analysis of X-Ray Bright
Points using Hinode's X-Ray Telescope (XRT)
Authors: Farid, S. I.; Saar, S.; Deluca, E.; Golub, L.; Weber, M.
Bibcode: 2007AGUFMSH22A0841F
Altcode:
The X-Ray telescope aboard Hinode utilizes up to thirteen filter
combinations with one arc second resolution to provide unprecedented
temperature coverage. In this study, we have used eleven X-Ray filters
to examine the statistical properties of X-ray bright points including
temperature, emission, and size distributions. We have analyzed what
appears to be a population of XRBs that are hotter than the main group
in order to identify any distinguishing properties.We discuss the
results of our analysis and their implications on XBP classification.
Title: Mangetic field properties at the footpoints of solar
microflares (active-region transient brightenings)
Authors: Shimizu, T.; Kano, R.; Katsukawa, Y.; Kubo, M.; Deluca, E.;
Ichimoto, K.; Lites, B.; Nagata, S.; Sakao, T.; Shine, R.; Suematsu,
Y.; Tarbell, T.; Title, A.; Tsuneta, S.
Bibcode: 2007AGUFMSH52C..06S
Altcode:
Solar active regions produce numerous numbers of small-scale explosive
energy releases, i.e., microflares, which are captured by imaging
observations in soft X-rays as transient brightenings of small-scale
coronal loops. Thanks to advanced performance of X-Ray Telescope (XRT)
onboard the Hinode satellite, we can investigate finer structure
of the brightening X-ray sources in more details than we did with
Yohkoh data. One of important questions on microflares is what causes
microflares. The simultaneous visible-light observations by the Solar
Optical Telescope (SOT) allow us to explore magnetic activities
and magnetic field configuration at the photospheric footpoints
of brightening loops, giving key observations to investigate the
question. For our investigations of corona-photosphere magnetic
coupling, we have established co-alignment between SOT and XRT
with accuracy better than 1 arcsec (Shimizu et al. 2007, PASJ in
press). It turns out that Ca II H observations are very useful
to identify the exact positions of footpoints of X-ray transient
brightening loops. Small "Kernels" are sometimes observed in Ca II H
and they may be signature of highly accelerated non-thermal particles
impinging on chromosphere. As already shown in Shimizu et al.(2002),
frequent transient brightenings are observed at the locations where
emerging activities are on going. However, another type of brightening
triggering mechanism should exist to explain some observed multiple-loop
brightenings. In the multiple-loop brightenings, multiple loops are
magnetically in parallel with each other and no apparent magnetic
activities, such as emerging and canceling, are observed at and near
the footpoints. This paper will present SOT observations of some
microflares observed with XRT.
Title: Slipping Magnetic Reconnection in Coronal Loops
Authors: Aulanier, Guillaume; Golub, Leon; DeLuca, Edward E.; Cirtain,
Jonathan W.; Kano, Ryouhei; Lundquist, Loraine L.; Narukage, Noriyuki;
Sakao, Taro; Weber, Mark A.
Bibcode: 2007Sci...318.1588A
Altcode:
Magnetic reconnection of solar coronal loops is the main process that
causes solar flares and possibly coronal heating. In the standard
model, magnetic field lines break and reconnect instantaneously at
places where the field mapping is discontinuous. However, another mode
may operate where the magnetic field mapping is continuous but shows
steep gradients: The field lines may slip across each other. Soft
x-ray observations of fast bidirectional motions of coronal loops,
observed by the Hinode spacecraft, support the existence of this
slipping magnetic reconnection regime in the Sun’s corona. This
basic process should be considered when interpreting reconnection,
both on the Sun and in laboratory-based plasma experiments.
Title: Evidence for Alfvén Waves in Solar X-ray Jets
Authors: Cirtain, J. W.; Golub, L.; Lundquist, L.; van Ballegooijen,
A.; Savcheva, A.; Shimojo, M.; DeLuca, E.; Tsuneta, S.; Sakao, T.;
Reeves, K.; Weber, M.; Kano, R.; Narukage, N.; Shibasaki, K.
Bibcode: 2007Sci...318.1580C
Altcode:
Coronal magnetic fields are dynamic, and field lines may misalign,
reassemble, and release energy by means of magnetic reconnection. Giant
releases may generate solar flares and coronal mass ejections and,
on a smaller scale, produce x-ray jets. Hinode observations of polar
coronal holes reveal that x-ray jets have two distinct velocities:
one near the Alfvén speed (~800 kilometers per second) and another
near the sound speed (200 kilometers per second). Many more jets were
seen than have been reported previously; we detected an average of
10 events per hour up to these speeds, whereas previous observations
documented only a handful per day with lower average speeds of 200
kilometers per second. The x-ray jets are about 2 × 103 to
2 × 104 kilometers wide and 1 × 105 kilometers
long and last from 100 to 2500 seconds. The large number of events,
coupled with the high velocities of the apparent outflows, indicates
that the jets may contribute to the high-speed solar wind.
Title: Continuous Plasma Outflows from the Edge of a Solar Active
Region as a Possible Source of Solar Wind
Authors: Sakao, Taro; Kano, Ryouhei; Narukage, Noriyuki; Kotoku,
Jun'ichi; Bando, Takamasa; DeLuca, Edward E.; Lundquist, Loraine L.;
Tsuneta, Saku; Harra, Louise K.; Katsukawa, Yukio; Kubo, Masahito;
Hara, Hirohisa; Matsuzaki, Keiichi; Shimojo, Masumi; Bookbinder, Jay
A.; Golub, Leon; Korreck, Kelly E.; Su, Yingna; Shibasaki, Kiyoto;
Shimizu, Toshifumi; Nakatani, Ichiro
Bibcode: 2007Sci...318.1585S
Altcode:
The Sun continuously expels a huge amount of ionized material into
interplanetary space as the solar wind. Despite its influence on the
heliospheric environment, the origin of the solar wind has yet to
be well identified. In this paper, we report Hinode X-ray Telescope
observations of a solar active region. At the edge of the active region,
located adjacent to a coronal hole, a pattern of continuous outflow of
soft-x-ray emitting plasmas was identified emanating along apparently
open magnetic field lines and into the upper corona. Estimates of
temperature and density for the outflowing plasmas suggest a mass
loss rate that amounts to ~1/4 of the total mass loss rate of the
solar wind. These outflows may be indicative of one of the solar wind
sources at the Sun.
Title: The Magnetic Structure of X-Ray Bright Points
Authors: Deluca, E. E.; van Ballegooijen, A. A.; Harvey, J. W.;
Henney, C. J.
Bibcode: 2007AGUFMSH53A1058D
Altcode:
The magnetic structure of X-Ray Bright Points (XBPs) observed by Hinode,
SOLIS and GONG are well represented by potential field extrapolation
models. SOLIS observations are used to compare the magnetic field
model with X-ray observations. GONG observation allow us to follow
the evolution of the magnetic structures that form the XBPs. Detailed
examination of the nulls in the corona around the bright points will
presented and discussed.
Title: Magnetic Feature and Morphological Study of X-Ray Bright
Points with Hinode
Authors: Kotoku, Jun'ichi; Kano, Ryouhei; Tsuneta, Saku; Katsukawa,
Yukio; Shimizu, Toshifumi; Sakao, Taro; Shibazaki, Kiyoto; Deluca,
Edward E.; Korreck, Kelly E.; Golub, Leon; Bobra, Monica
Bibcode: 2007PASJ...59S.735K
Altcode:
We observed X-ray bright points (XBPs) in a quiet region of the Sun
with the X-Ray Telescope (XRT) aboard the Hinode satellite on 2006
December 19. XRT's high-resolution X-ray images revealed many XBPs with
complicated structure and evolving dramatically with time. Almost all
of the dynamic eruptions in the quiet region were composed of XBPs,
and they had either loop or multiloop shapes, as is observed in larger
flares. Brightening XBPs had strong magnetic fields with opposite
polarities near their footpoints. While we have found a possible
example of associated magnetic cancellation, other XBPs brighten and
fade without any associated movement of the photospheric magnetic field.
Title: A Study of Polar Jet Parameters Based on Hinode XRT
Observations
Authors: Savcheva, Antonia; Cirtain, Jonathan; Deluca, Edward E.;
Lundquist, Loraine L.; Golub, Leon; Weber, Mark; Shimojo, Masumi;
Shibasaki, Kiyoto; Sakao, Taro; Narukage, Noriyuki; Tsuneta, Saku;
Kano, Ryouhei
Bibcode: 2007PASJ...59S.771S
Altcode:
Hinode/SOHO campaign 7197 is the most extensive study of polar jet
formation and evolution from within both the north and south polar
coronal holes so far. For the first time, this study showed that the
appearance of X-ray jets in the solar coronal holes occurs at very high
frequency - about 60 jets d-1 on average. Using observations
collected by the X-Ray Telescope on Hinode, a number of physical
parameters from a large sample of jets were statistically studied. We
measured the apparent outward velocity, the height, the width and
the lifetime of the jets. In our sample, all of these parameters show
peaked distributions with maxima at 160kms-1 for the outward
velocity, 5 × 104 km for the height, 8 × 103
km for the width, and about 10min for the lifetime of the jets. We
also present the first statistical study of jet transverse motions,
which obtained transverse velocities of 0-35kms-1. These
values were obtained on the basis of a larger (in terms of frequency)
and better sampled set of events than what was previously statistically
studied (Shimojo et al. 1996, PASJ, 48, 123). The results were made
possible by the unique characteristics of XRT. We describe the methods
used to determine the characteristics and set some future goals. We
also show that despite some possible selection effects, jets preferably
occur inside the polar coronal holes.
Title: Hinode Calibration for Precise Image Co-Alignment between
SOT and XRT (2006 November-2007 April)
Authors: Shimizu, Toshifumi; Katsukawa, Yukio; Matsuzaki, Keiichi;
Ichimoto, Kiyoshi; Kano, Ryohei; Deluca, Edward E.; Lundquist,
Loraine L.; Weber, Mark; Tarbell, Theodore D.; Shine, Richard A.;
Sôma, Mitsuru; Tsuneta, Saku; Sakao, Taro; Minesugi, Kenji
Bibcode: 2007PASJ...59S.845S
Altcode: 2007arXiv0709.4098S
To understand the physical mechanisms for activity and heating in
the solar atmosphere, the magnetic coupling from the photosphere
to the corona is an important piece of information from the Hinode
observations, and therefore precise positional alignment is required
among the data acquired by different telescopes. The Hinode spacecraft
and its onboard telescopes were developed to allow us to investigate
magnetic coupling with co-alignment accuracy better than 1". Using
the Mercury transit observed on 2006 November 8 and co-alignment
measurements regularly performed on a weekly basis, we have determined
the information necessary for precise image co-alignment, and have
confirmed that co-alignment better than 1" can be realized between
Solar Optical Telescope (SOT) and X-Ray Telescope (XRT) with our
baseline co-alignment method. This paper presents results from the
calibration for precise co-alignment of CCD images from SOT and XRT.
Title: Evolution of the Sheared Magnetic Fields of Two X-Class Flares
Observed by Hinode/XRT
Authors: Su, Yingna; Golub, Leon; van Ballegooijen, Adriaan; Deluca,
Edward E.; Reeves, Kathy K.; Sakao, Taro; Kano, Ryouhei; Narukage,
Noriyuki; Shibasaki Kiyoto
Bibcode: 2007PASJ...59S.785S
Altcode:
We present multi-wavelength observations of the evolution of the sheared
magnetic fields in NOAA Active Region 10930, where two X-class flares
occurred on 2006 December 13 and December 14, respectively. Observations
made with the X-ray Telescope (XRT) and the Solar Optical Telescope
(SOT) aboard Hinode suggest that the gradual formation of the sheared
magnetic fields in this active region is caused by the rotation and
west-to-east motion of an emerging sunspot. In the pre-flare phase
of the two flares, XRT shows several highly sheared X-ray loops in
the core field region, corresponding to a filament seen in the TRACE
EUV observations. XRT observations also show that part of the sheared
core field erupted, and another part of the sheared core field stayed
behind during the flares, which may explain why a large part of the
filament is still seen by TRACE after the flare. About 2-3 hours after
the peak of each flare, the core field becomes visible in XRT again,
and shows a highly sheared inner and less-sheared outer structure. We
also find that the post-flare core field is clearly less sheared than
the pre-flare core field, which is consistent with the idea that the
energy released during the flares is stored in the highly sheared
fields prior to the flare.
Title: An On-Orbit Determination of the On-Axis Point Spread Function
of the Hinode X-Ray Telescope
Authors: Weber, Mark; Deluca, Edward E.; Golub, Leon; Cirtain,
Jonathan; Kano, Ryouhei; Sakao, Taro; Shibasaki, Kiyoto; Narukage,
Noriyuki
Bibcode: 2007PASJ...59S.853W
Altcode:
The Hinode X-ray Telescope provides unprecedented observations of
the solar corona in X-rays, due in part to its fine resolution. The
X-ray point spread function (PSF) was measured before launch at the
NASA X-ray Calibration Facility to have a FWHM of 0.8''. This paper
describes the work to verify the PSF measurements using on-orbit
observations of planetary transits and solar eclipses. Analysis of a
Mercury transit gives a PSF FWHM = 1.0" ± 0.12".
Title: The X-Ray Telescope for Solar-B: Calibration and Predicted
Performance
Authors: Deluca, E. E.
Bibcode: 2007ASPC..369...19D
Altcode:
The X-Ray Telescope (XRT) for Solar-B will provide coronal imaging
with unprecedented spatial and temporal coverage. XRT was subjected to
several calibration tests during the course of its construction. The
x-ray mirror and CCD were calibrated separately and the entire telescope
was calibrated ``end-to-end". The mirror and end-to-end tests were held
at the NASA's Marshal Space Flight Center X-Ray Calibration Facility
(XRCF). The CCD calibrations were performed at NAOJ. The calibration
results show that XRT meets all of its design requirements, it will
provide high resolution, multi-thermal, wide FOV, low scattering
observations of the solar corona for Solar-B. XRT will be the highest
spatial resolution solar X-Ray Telescope every flown, FWHM of the PSF
is 10.4 μm (0.8 arcsec). We will present the summary findings of the
calibration efforts and discuss the performance of the XRT.
Title: What Determines the Intensity of Solar Flare/CME Events?
Authors: Su, Yingna; Van Ballegooijen, Adriaan; McCaughey, James;
Deluca, Edward; Reeves, Katharine K.; Golub, Leon
Bibcode: 2007ApJ...665.1448S
Altcode:
We present a comprehensive statistical study addressing the question of
what determines the intensity of a solar flare and associated coronal
mass ejection (CME). For a sample of 18 two-ribbon flares associated
with CMEs, we have examined the correlations between the GOES soft X-ray
peak flare flux (PFF), the CME speed (VCME) obtained from
SOHO LASCO observations, and six magnetic parameters of the flaring
active region. These six parameters measured from both TRACE and SOHO
MDI observations are: the average background magnetic field strength
(B), the area of the region where B is counted (S), the magnetic
flux of this region (Φ), the initial shear angle (θ1,
measured at the flare onset), the final shear angle (θ2,
measured at the time when the shear change stops), and the change of
shear angle (θ12=θ1-θ2) of the
footpoints. We have found no correlation between θ1
and the intensity of flare/CME events, while the other five
parameters are either positively or negatively correlated with
both log10(PFF) and VCME. Among these five parameters,
Φ and θ12 show the most significant correlations with
log10(PFF) and VCME. The fact that both log10(PFF) and
VCME are highly correlated with θ12 rather
than with θ1 indicates that the intensity of flare/CME
events may depend on the released magnetic free energy rather than
the total free energy stored prior to the flare. We have also found
that a linear combination of a subset of these six parameters shows
a much better correlation with the intensity of flare/CME events than
each parameter itself, and the combination of log10Φ, θ1,
and θ12 is the top-ranked combination.
Title: Data Archive of the Hinode Mission
Authors: Matsuzaki, K.; Shimojo, M.; Tarbell, T. D.; Harra, L. K.;
Deluca, E. E.
Bibcode: 2007SoPh..243...87M
Altcode:
All of the Hinode telemetry data are to be reformatted and archived
in the DARTS system at ISAS and mirrored to data centers around
the word. The archived data are distributed to users through the
Internet. This paper gives an overview of the files in the archive,
including the file formats. All formats are portable and have
heritage from the previous missions. From the reformatted files, index
information is created for faster data search. Users can perform queries
based on information contained in the index. This allows for searches
to return observations that conform to particular observing conditions.
Title: The X-Ray Telescope (XRT) for the Hinode Mission
Authors: Golub, L.; DeLuca, E.; Austin, G.; Bookbinder, J.; Caldwell,
D.; Cheimets, P.; Cirtain, J.; Cosmo, M.; Reid, P.; Sette, A.; Weber,
M.; Sakao, T.; Kano, R.; Shibasaki, K.; Hara, H.; Tsuneta, S.; Kumagai,
K.; Tamura, T.; Shimojo, M.; McCracken, J.; Carpenter, J.; Haight,
H.; Siler, R.; Wright, E.; Tucker, J.; Rutledge, H.; Barbera, M.;
Peres, G.; Varisco, S.
Bibcode: 2007SoPh..243...63G
Altcode:
The X-ray Telescope (XRT) of the Hinode mission provides an
unprecedented combination of spatial and temporal resolution in solar
coronal studies. The high sensitivity and broad dynamic range of XRT,
coupled with the spacecraft's onboard memory capacity and the planned
downlink capability will permit a broad range of coronal studies over
an extended period of time, for targets ranging from quiet Sun to
X-flares. This paper discusses in detail the design, calibration, and
measured performance of the XRT instrument up to the focal plane. The
CCD camera and data handling are discussed separately in a companion
paper.
Title: The Dynamics Of Fine Structures In Solar X-ray Jets
Authors: Shimojo, Masumi; Narukage, N.; Kano, R.; Sakao, T.; Tsuneta,
T.; Cirtain, J. W.; Lundquist, L. L.; Deluca, E. E.; Golub, L.
Bibcode: 2007AAS...210.9422S
Altcode: 2007BAAS...39Q.221S
The X-ray telescope(XRT) aboard HINODE satellite has the great
spatial/time resolution in X-ray range. And, the observations using
XRT have revealed the fine structures of solar corona. From the
observations, we found the fine thread structures in the X-ray jets
and the structures move dynamically like wave. We also found that some
X-ray jets start just after small loop expansion in the footpoint
brightening. The observation results suggest that the reconnection
process X-ray jets is very similar to that in large flares.
Title: Hinode Data Calibration For Precise Image Co-alignment:
XRT vs. SOT
Authors: Shimizu, Toshifumi; DeLuca, E. E.; Lundquist, L.; Sakao,
T.; Kubo, M.; Narukage, N.; Kano, R.; Katsukawa, Y.; Ichimoto, K.;
Suematsu, Y.; Tsuneta, S.; Tarbell, T.; Shine, D.; Hinode Team
Bibcode: 2007AAS...210.9417S
Altcode: 2007BAAS...39Q.220S
From late October in 2006, Hinode solar optical telescope (SOT) has
started to produce series of 0.2-0.3 arcsec visible-light images,
revealing dynamical behaviors of solar magnetic fields on the
solar surface. Simultaneously, Hinode X-ray telescope (XRT) has been
providing 1 arcsec resolution X-ray images of the solar corona, giving
the location of heating and dynamics occuring in the corona. Precise
image co-alignment of SOT data on XRT data with sub-arcsec accuracy is
required to provide new information regarding connecting the corona to
the photosphere. This presentation will give an introduction of Hinode
between-telescopes' image co-alignment to SPD participants. For active
region observations with sunspots, sunspots can be used as fiducial to
co-align the data from the two telescopes each other. Satellite jitter
in order of 1 arcsec or less is included in the series of XRT data,
whereas image stabilization system (correlation tracker) removes the
satellite jitter from the series of SOT images. Telescope pointings show
orbital variation in order of a few arcsec, which can be well predicted
from Hinode orbit information. Modeling co-alignment is under study
and it is the only precise method for quiet Sun and limb observations.
Title: Coronal Loops: Isothermal or Multithermal?
Authors: Kimble, Jason; Schmelz, J. T.; Nasraoui, K.; Cirtain, J. W.;
Del Zanna, G.; DeLuca, E. E.; Mason, H. E.
Bibcode: 2007AAS...210.9120K
Altcode: 2007BAAS...39..207K
The coronal loop data used for this analysis were taken on 2003 January
17 at 14:24:45 UT by the Coronal Diagnostic Spectrometer (CDS) aboard
the Solar and Heliospheric Observatory. We use the Chianti atomic
physics data base and the hybrid coronal abundances to determine
temperatures and densities for positions along several loops. The
traditional method used to create our differential emission measure
(DEM) curves has been forward folding, but we are now using both
emission measure loci plots and DEM automatic inversion to support
and confirm the original conclusions. In this poster, we will look
specifically at the emission measure loci analysis of three loops
visible in the CDS data set. We find different results for each of
these loops. One of the loops seems to be composed of isothermal
plasma with Log T = 5.8 MK. The temperature does not appear to change
with position, from the footpoint to the loop leg. Unfortunately,
the loop top is outside the CDS field of view. Each pixel examined in
the second loop seems to require a multithermal DEM distribution. For
the third loop, the temperature increases and the density appears
to decrease with loop height, reminiscent of traditional hydrostatic
loop models. Solar physics research at the University of Memphis is
supported by NSF ATM-0402729 and NASA NNG05GE68G.
Title: SOHO-CDS: Thermal and Density Analysis of Coronal Loops
Authors: Rightmire, Lisa; Schmelz, J. T.; Cirtain, J. W.; Del Zanna,
G.; DeLuca, E. E.; Mason, H. E.
Bibcode: 2007AAS...210.9121R
Altcode: 2007BAAS...39..207R
Data was obtained using the Coronal Diagnostic Spectrometer (CDS)
instrument on the Solar and Heliospheric Observatory (SOHO). The goal
of this project is to analyze the data obtained by the CDS instrument
in order to determine the behavior of temperature and density of the
coronal loop progressing from the foot point and moving up the loop. The
loop being analyzed was observed by CDS on 2003 January 17 and the foot
point was located at solar coordinates (585,-472) arcsecs. A background
pixel and several pixels on the loop were selected. The background pixel
intensity was then subtracted from each loop pixel intensity in order to
isolate the emission from each loop pixel. The spectral line intensities
of each loop pixel were analyzed to determine which spectral lines
had any significant contribution to the loop intensity. The predicted
and observed intensities of these significant lines were then used to
create a differential emission measure (DEM) curve to best fit each
loop pixel emission. Comparison of the DEM curves for each loop pixel
indicates that the temperature increases and the density decreases,
while progressing up the loop. Solar physics research at the University
of Memphis is supported by NSF ATM-0402729 and NASA NNG05GE68G.
Title: A Study of Polar Jet Parameters Based on Solar-B XRT
Observations
Authors: Savcheva, Antonia; Cirtain, J.; Lundquist, L. L.; DeLuca,
E. E.; Shimojo, M.; Tsuneta, S.
Bibcode: 2007AAS...210.9116S
Altcode: 2007BAAS...39T.206S
SoHO/Hinode campaign 7197 studied polar jet formation from within
both the north and south polar coronal holes. Using the observations
collected by the X-Ray Telescope on Hinode, a number of physical
parameters of the jets have been characterized. We will show the
results for velocity, emission measure, length, width, lifetime, and
spatial distribution. These observational results will be compared to
models such as the Shibata-type reconnection model and correlations
to estimates of the theoretical model will be compared to the observations.
Title: Coronal Temperature Diagnostics With Hinode X-ray Telescope
Authors: Narukage, Noriyuki; Sakao, T.; Kano, R.; Shimojo, M.; Tsuneta,
S.; Kosugi, T.; Deluca, E. E.; Golub, L.; Weber, M.; Cirtain, J.;
Japan-US X-Ray Telescope Team
Bibcode: 2007AAS...210.6304N
Altcode: 2007BAAS...39..172N
An X-ray telescope (XRT) on board HINODE satellite observes the Sun
in X-rays with high special resolution (1arcsec 730km on solar the
disk). This telescope has 9 X-ray filters with different temperature
responses. Using these filters, the XRT can detect the coronal
plasma with a wide temperature range from less than 1MK to more
than 10MK. Moreover, based on observations with more than 2 filters,
we can estimate the coronal temperature. In this paper, we use the
filter ratio method for coronal temperature diagnostics. Using this
method, we can easily estimate the averaged temperature of the coronal
plasma along the line-of-sight. This method has been used frequently
in the past, but the high quality XRT data give us temperature maps
with unprecedented accuracy and resolution. The XRT usually takes
the full Sun images with 2 kinds of filters 4 times a day. Using this
data and filter ratio method, we can obtain full Sun temperature maps
with high special resolution. In our analysis, we can derive reliable
temperatures not only in active regions but also in quiet regions and
coronal holes. This map can be created with the data set of one synoptic
observation. This means that we can obtain 4 maps a day. The result is
a full Sun temperature movie that gives us an unprecedented view of the
time evolution of solar temperature. In this meeting, we will show the
full Sun temperature movie and our coronal temperature analysis results.
Title: Magnetic Shear in Two-ribbon Solar Flares
Authors: Su, Yingna; Golub, L.; Van Ballegooijen, A.; McCaughey, J.;
Deluca, E. E.; Reeves, K.; Gros, M.
Bibcode: 2007AAS...210.3702S
Altcode: 2007BAAS...39Q.151S
To study shear motion of the footpoints in solar flares, we selected
50 X- and M- class two-ribbon flares observed by TRACE (in 1998-2005)
as our data sample. We found that: 1) 86% (43 out of 50) of these
flares show both strong-to-weak shear change of footpoints and ribbon
separation. Shear motion of footpoints is thus a common feature
in two-ribbon flares; 2) the initial and final shear angles of the
footpoints in this type of flare are mainly in the range from 50° to
80° and 15° to 55°, respectively; 3) in 10 out of the 14 events with
both measured shear angle and corresponding hard X-ray observations,
the cessation of shear change is 0-2 minutes earlier than the end of
the impulsive phase. This may suggest that the change from impulsive to
gradual phase is related to magnetic shear change. We then selected 20
flares with measured shear angles and corresponding CMEs from our data
sample. For these flares, we found that the magnetic flux and change
of shear angle show comparably strong correlations with the peak flare
flux and CME speed, while the intial shear angle does not. This result
indicates that the intensity of flare/CME events may depend mainly on
the released magnetic free energy rather than the total magnetic free
energy stored prior to the eruption. After a successful launch last
September, Hinode (Solar-B) caught two X-class solar flares, which
occurred in AR 10930 on Dec 13 and 14, 2006. Using these new datasets
(Hinode/XRT, Hinode/SOT, TRACE, and SOHO/MDI), we carried out a study of
the evolution of the sheared magnetic fields involved in these flares,
and some preliminary results will also be presented. The TRACE analysis
was supported at Smithsonian Astrophysical Observatory by a contract
from Lockheed Martin.
Title: Intercalibration of the X-ray Telescope and the EUV Imaging
Spectrometer on Hinode
Authors: Golub, Leon; Cirtain, J.; DeLuca, E. E.; Hara, H.; Warren,
H.; Weber, M.
Bibcode: 2007AAS...210.9418G
Altcode: 2007BAAS...39..220G
The X-Ray Telescope and the Extreme-Ultra Violet Imaging Spectrometer
on Hinode are designed to measure the emission of excited ions formed
at temperatures ranging from 104-108 K. The
temperature overlap of these two telescope is from 0.7 to 20 MK, and
an on-orbit calibration of the sensitivity of the two instruments
to solar features will provide a basis for future observational
comparisons. Using calibrated samples of data from each instrument,
and relying to a great extent on the CHIANTI spectral code, we have
derived an estimate of the inter-calibration of the two telescope
for a variety of different solar features and conditions. This is a
major step in enhancing our ability to use the instruments together
for providing quantitative diagnostics of the solar plasma.
Title: Continuous Upflow of Plasmas at the Edge of an Active Region
as Revealed by the X-ray Telescope (XRT) aboard Hinode
Authors: Sakao, Taro; Kano, R.; Narukage, N.; Kotoku, J.; Bando, T.;
DeLuca, E. E.; Lundquist, L. L.; Golub, L.; Kubo, M.; Katsukawa, Y.;
Tsuneta, S.; Hara, H.; Matsuzaki, K.; Shimojo, M.; Shibasaki, K.;
Shimizu, T.; Nakatani, I.
Bibcode: 2007AAS...210.7205S
Altcode: 2007BAAS...39Q.179S
We present X-ray imaging observations with Hinode X-Ray Telescope (XRT)
of an active region NOAA AR 10942 made in the period of 20-22 February
2007. A prominent feature that drew our particular attention is that
there revealed continuous upflow of soft-X-ray-emitting plasmas along
apparently-open field lines towards the outer corona emanating from the
edge of the active region. The field lines are originated from
an ensamble of small spots of following polarity, and are located at
a border between the active region and an adjacent equatorial coronal
hole(s) located to the east. The upflow was observed to be continuous
throughout the three days of observation intervals with projected
velocity of 140 km/s, accompanied with undulating motion of the field
lines. We assert that these upflowing plasmas would be a possible
source of slow solar wind material, which supports a foresighted
notion which grew out of interplanetary scintillation observations
that slow solar wind most likely has its origin in the vicinity of
active regions with large flux expansion (Kojima et al. 1999). A
preliminaty analysis indicates that the temperature of the upflowing
material near the base of the field lines is 1.3 MK with number density
of 2 × 109 /cm3. Assuming that all the material
is to escape to the interplanetary space, this leads to a mass loss
rate of 2 × 1011 g/s which amounts to a good fraction of
the total mass loss rate for solar wind. It is noteworthy that, even
apart from this unique upflow, we see continuous (up)flows of plasmas
anywhere around (surrounding) the active region. Details of the
upflow will be presented and their possible implication to slow solar
wind discussed.
Title: Modeling Non-Potential Magnetic Fields in Solar Active Regions
Authors: Bobra, Monica; van Ballegooijen, A. A.; DeLuca, E. E.
Bibcode: 2007AAS...210.9103B
Altcode: 2007BAAS...39..204B
Many models aim to reproduce the non-linear force free fields in
the solar corona; in this particular study, the magnetofrictional
relaxation method is tested. This method produces non-linear force
free fields based on line-of-sight magnetograms and ground-based Hα
images to define the location of a filament, which is represented by
a flux rope. The models are tested by comparing the results to TRACE
and Hinode X-Ray Telescope (XRT) observations of highly sheared,
non-potential loop structures in active regions. For each event, we
(1) determine the amount of flux contained in the flux ropes needed
to reproduce the observed loops, (2) estimate the current, torsion
parameter α, and quasi-separatrix layer distributions, and (3)
estimate the relative magnetic helicity and magnetic free energy in
the computational domain. This work was supported by NASA LWS grant
NNG05GK32G.
Title: Structure and Coronal Activity around Filament Channels
Observed with Hinode XRT And TRACE
Authors: Lundquist, Loraine L.; van Ballegooijen, A. A.; Reeves,
K. K.; Sakao, T.; DeLuca, E. E.; Narukage, N.; Kano, R.
Bibcode: 2007AAS...210.9427L
Altcode: 2007BAAS...39..221L
The combination of multi-wavelength, high resolution, high cadence
data from the Hinode X-Ray Telescope (XRT) and the Transition Region
And Coronal Explorer (TRACE) give an unprecedented view of solar
active region dynamics and coronal topology. We focus on examples of
filament structures observed by TRACE and XRT in December 2006 and
February 2007. Co-alignment of observations in these two instruments
yields a striking picture of the coronal structures, with loops lying
both along and above the filament. Overlying loops exhibit remarkable
dynamics while the filament lies dormant, and numerous x-point and
triple-leg structures undergo repeated brightenings. We also employ
magnetic field data from SOT and from SOLIS to compare a non-linear
force-free model of the coronal magnetic field with the observed loops.
Title: On-orbit Measurement Of The Hinode/XRT Point Spread Function
Authors: Weber, Mark A.; Cirtain, J.; Golub, L.; DeLuca, E. E.;
Martens, P.; XRT Team
Bibcode: 2007AAS...210.9416W
Altcode: 2007BAAS...39..220W
The Hinode X-Ray Telescope provides unprecedented observations of
the solar corona in x-rays, due in part to its fine resolution. The
optical point spread function (PSF) was measured before launch at the
NASA X-Ray Calibration Facility to have a FWHM of 0.92 arc-seconds. In
this poster we describe our work to verify the PSF measurements using
on-orbit data. The US XRT team is supported by a contract from NASA to
SAO. Hinode is an international project supported by JAXA, NASA, PPARC,
and ESA. We are grateful to the Hinode team for all their efforts in
the design, development, and operation of the mission.
Title: Temperature Structures Above Coronal Hole and Quiet Sun
Authors: Kano, Ryouhei; Sakao, T.; Narukage, N.; Kotoku, J.; Bando,
T.; DeLuca, E. E.; Lundquist, L.; Golub, L.; Tsuneta, S.; Hara, H.;
Shibasaki, K.; Shimojo, M.
Bibcode: 2007AAS...210.9436K
Altcode: 2007BAAS...39..223K
The X-ray Telescope (XRT) on board Hinode satelite has the capability
to derive the temperature structure in the solar corona. We present
the hieght dependence of the temperature above the limb. Because X-ray
intensity above the limb is so faint, it is important to estimate the
scattered light from disk corona. The eclipses happened on February 17
and March 19 in 2007 at Hinode orbit. On February 17, we took X-ray
images above the south polar coronal hole, while Moon passed it. On
March 19, we took the data for quiet Sun in the same way. We
can estimated the scattered light from the eclipse data, and derived
the scatter-free X-ray images above the solar limb. In this meeting,
we will present the temperatures above coronal hole and quiet Sun,
based on the eclipse data.
Title: Are Coronal Loops Isothermal Or Multithermal? Yes!
Authors: Schmelz, Joan T.; Nasraoui, K.; Rightmire, L.; Garst, J.;
Kimble, J.; Cirtain, J.; DeLuca, E. E.; Del Zanna, G.; Mason, H.
Bibcode: 2007AAS...210.9431S
Altcode: 2007BAAS...39..222S
Analysis of loops observed with the Coronal Diagnostics Spectrometer
(CDS) and the Transition Region and Coronal Explorer (TRACE) reveal
examples of both isothermal and multithermal plasma. These data
were taken on 2003 January 17, and since the loops are on the disk,
a lot of work was done on the details of background subtraction. The
background-subtracted CDS intensities were analyzed using three
methods: (1) Emission Measure Loci, (2) Forward-Folding DEM, and (3)
Automatic-Inversion DEM. The first loop appears to be isothermal,
with Log T = 5.8 MK. The forward-folding DEM shows a spike at this
temperature and the EM Loci curves all intersect at this point. The
automatic-inversion DEM results are broadened, however, as a result
of the smoothing required for this method. This loop has a uniform
temperature along the segment visible in the CDS field of view,
and this result is confirmed using the TRACE data. The pixels along
the second loop do not appear to be isothermal. The EM Loci curves
do not intersect at a single point and both DEM methods show a broad
curve. Other loops in this data set as well as loop evolution will be
investigated if time permits. Solar physics research at the University
of Memphis is supported by NSF ATM-0402729 and NASA NNG05GE68G.
Title: The X-ray Telescope On Hinode
Authors: DeLuca, Edward E.; US-Japan X-Ray Telescope Team
Bibcode: 2007AAS...210.6302D
Altcode: 2007BAAS...39..171D
The X-ray Telescope (XRT) on the Hinode mission provides an
unprecedented combination of spatial and temporal resolution in solar
coronal studies. The high sensitivity and broad dynamic range of XRT,
coupled with the spacecraft's onboard memory capacity and downlink
capability permit a broad range of coronal studies over an extended
period of time, for targets ranging from quiet Sun to X-flares. We will give an overview of the first results from XRT and provide
information on how to access the Hinode data and information on how
to propose joint observations with Hinode. The US XRT team is
supported by a contract from NASA to SAO. Hinode is an international
project supported by JAXA, NASA, PPARC and ESA. We are grateful to
the Hinode team for all their efforts in the design, development and
operation of the mission.
Title: The Sun-as-a-star As Seen By Hinode XRT
Authors: Saar, Steven H.; DeLuca, E. E.
Bibcode: 2007AAS...210.9424S
Altcode: 2007BAAS...39R.221S
We study full disk images of the Sun taken in multiple filters with
the Hinode XRT during the current low state of the solar cycle (late
2006). Taking advantage of the wide temperature sensitivity of the
XRT, we construct spatially averaged emission measure (EM) curves for
each of several solar region types, including coronal holes, quiet Sun,
bright points, and active regions of various description. These are
used to determine the relative contribution of the various features to
the total solar EM, as a starting point for a program to investigate
their time variation. We also explore use of the average EM curves
for understanding spatially unresolved stellar spectra and their
correlation with underlying magnetic fields. The US XRT team is
supported by a contract from NASA to SAO. Hinode is an international
project supported by JAXA, NASA, PPARC and ESA. We are grateful
to the Hinode team for all their efforts in the design, development
and operation of the mission.
Title: Differential Emission Measurements on Sparse Raster Data
from SOHO-CDS
Authors: Garst, Jennifer W.; Schmelz, J. T.; Nasraoui, K.; Cirtain,
J. W.; DeLuca, E. E.; Del Zanna, G.; Mason, H. E.
Bibcode: 2007AAS...210.2517G
Altcode: 2007BAAS...39..133G
Two types of rasters were taken on 2003 January 17 with the Solar and
Heliospheric Observatory’s Coronal Diagnostic Spectrometer. The
first type contains a continuous image of coronal loops under
investigation while the second, the ‘sparse raster,’ was taken at
spatial intervals in order to simulate enhanced time resolution. With
this technique, intensities in 14 passbands were collected at fixed
positions on the solar disk every 7 minutes. The start time for the
CDS observations was 06:51:27 UT and the observing sequences ran for
7 hours. The continuous rasters were interspersed with the sparse
rasters. All the rasters were then co-aligned and a loop pixel and a
background pixel were selected for detailed analysis. Differential
emission measure was performed on the background-subtracted CDS
intensities to determine the temporal evolution of the loop pixel
plasma. Solar physics research at the University of Memphis is supported
by NSF ATM-0402729 and NASA NNG05GE68G.
Title: The Statistics of Polar Coronal Jets using XRT/Hinode
Authors: Cirtain, Jonathan W.; Lundquist, L. L.; DeLuca, E. E.;
Savcheva, A.; Shimojo, M.; Tsuneta, S.
Bibcode: 2007AAS...210.9432C
Altcode: 2007BAAS...39..222C
Recent observations of the polar coronal holes using the X-Ray Telescope
on Hinode revealed how frequent x-ray jets occur. Previous observations
were limited by cadence, spatial resolution and continuity. However,
with XRT operations successfully underway, multiple weeks of polar
observations can be used to provide improved statistics of some
fundamental physical parameters of the jets. In particular, we will
present results for the radial and transverse velocities, observed
length and width, duration, and spatial distribution of some of the
more than 200 jets XRT has observed to date. The observed changes in
the structure of the region where the jets are formed seems to be well
characterized by the Shibata-type reconnection model. Examples will
be provided.
Title: Coronal Diagnostics Spectrometer Observations of Coronal Loops
Authors: Nasraoui, Kaouther; Schmelz, J. T.; Cirtain, J. W.; Del Zanna,
G.; DeLuca, E. E.; Mason, H. E.
Bibcode: 2007AAS...210.9122N
Altcode: 2007BAAS...39..207N
Two side by side loops from the solar disk were analyzed. These two
loops were observed with the Coronal Diagnostics Spectrometer on
SOHO on 2003 January 17. The first loop was best seen in Mg IX at
a wavelength of 368 angstroms and a peak formation temperature of
Log T = 6.0. Seven pixels on the loop and one background pixel were
chosen. The intensity of the background pixel was subtracted from each
of the loop pixels. Only the lines that had a significant intensity
after background subtraction were considered. A differential emission
measure (DEM) curve was constructed for the background subtracted data
using the forward folding technique. The DEM for most of these pixels
had a spike shape at Log T equal to 5.85. This result shows that the
loop is isothermal at most of these pixels. The second loop was best
seen in Si XII at a wavelength of 520 angstroms and a peak formation
temperature of Log T = 6.3. The same procedure was followed for the
data analysis. After background subtraction only some hot lines had a
significant intensity and a DEM curve was constructed for each loop
pixel. This time the DEM is broader with a shape that shows that
the loop plasma is multithermal with a log temperature range of 6.1
to 6.5. Solar physics research at the University of Memphis is
supported by NSF ATM-0402729 and NASA NNG05GE68G.
Title: Coronal Diagnostic Spectrometer Observations of Isothermal
and Multithermal Coronal Loops
Authors: Schmelz, J. T.; Nasraoui, K.; Del Zanna, G.; Cirtain, J. W.;
DeLuca, E. E.; Mason, H. E.
Bibcode: 2007ApJ...658L.119S
Altcode:
A data set obtained on 2003 January 17 with the Coronal Diagnostic
Spectrometer (CDS) shows two loops sitting side by side on the solar
disk. These loops are oriented along the CDS slit, so all pixels in
each loop were observed simultaneously. So, although the instrument
has a relatively slow time cadence, changes as a function of time
that may occur during the CDS raster buildup will not affect the loop
temperature results. Differential emission measure (DEM) analysis
using a forward-folding technique shows different results for the
two loops. For the first loop, the intensities of the lines that
remain after background subtraction are well fit with a DEM curve that
collapses to a single spike. In other words, the loop plasma at this
location is isothermal. This analysis is confirmed with an emission
measure loci method and agrees with the results obtained recently
by other authors that show that the moderate spatial resolution
of CDS can detect isothermal structures. For the second loop, the
background-subtracted line intensities require a broad DEM, not
consistent with isothermal plasma. This conclusion is confirmed with
an automatic-inversion DEM method. In this Letter, we specifically
address some of the concerns raised about CDS temperature analysis:
the slow CDS temporal resolution, the moderate CDS spatial resolution,
the inherent smoothing associated with DEM inversion, and line-of-sight
effects on the DEM distribution.
Title: Modeling magnetic flux ropes in the solar atmosphere
Authors: van Ballegooijen, A. A.; Deluca, E. E.; Squires, K.; Mackay,
D. H.
Bibcode: 2007JASTP..69...24V
Altcode: 2007JATP...69...24V
Coronal flux ropes are highly sheared or twisted magnetic fields
overlying polarity inversion lines on the solar photosphere. The
formation of such flux ropes is briefly discussed. A coronal flux
rope can be stable for many days and then suddenly lose equilibrium
and erupt, producing a coronal mass ejection (CME). To understand
what causes such eruptions, we need to determine the 3D magnetic
structure of observed active regions prior to CMEs. This requires
constructing nonlinear force free field models of active regions based
on observed photospheric vector fields, Hα filaments, or coronal loop
structures. We describe a new method for constructing models containing
flux ropes.
Title: Active Region Loops: Temperature Measurements as a Function
of Time from Joint TRACE and SOHO CDS Observations
Authors: Cirtain, J. W.; Del Zanna, G.; DeLuca, E. E.; Mason, H. E.;
Martens, P. C. H.; Schmelz, J. T.
Bibcode: 2007ApJ...655..598C
Altcode:
In this paper, we aim to quantitatively investigate the structure
and time variation of quiescent active region loop structures. We
coordinated a joint program of observations (JOP 146) using TRACE, to
obtain high-cadence EUV images, and SOHO CDS, to obtain spectroscopic
data. Loop intensities are used to determine temperature as a function
of time for a single loop, taking full account of the background
emission. In many locations, the emission measure loci are consistent
with an isothermal structure. However, the results indicate significant
changes in the loop temperature (between 1 and 2 MK) over the 6 hr
observing period. It is possible that the loop structures are composed
of multiple, independently heated strands with sizes less than the
resolution of the imager and spectrometer.
Title: Coronal Loop Recognition: A Diagnostic Tool for Magnetic
Field Extrapolation Models
Authors: Sandell, Julia; Kashyap, V.; Weber, M.; van Ballegooijen,
A.; Deluca, E.; Bobra, M.
Bibcode: 2006AAS...209.1604S
Altcode: 2006BAAS...38..918S
Constraining the structure and extent of the coronal magnetic field is
important for theories of coronal heating. This can be accomplished
by matching the models of magnetic fields derived by extrapolating
measurements of surface magnetic flux, with highly detailed structure
present in EUV and X-ray images of the corona. Using high resolution
TRACE images we detect loops in an automated manner, and aim to
replace the currently used method of manually selecting pixels that
might comprisea loop. We apply this method to a set of TRACE images
and identify loops for further analysis. We fit force-free potential
field models of the magnetic field to these loops and derive useful
parameters that describe the geometric and physical parameters of
the loop. We find that the loops are generally of length > 1010
cm. If assumed to be in static equilibrium, the loop top temperatures
are 3-5 MK. the field lines are characterized by strength ranging
from 0.4-27 G. After carrying out numerous Monte Carlo simulations,
each time varying different parameters used in the program, we found
this new automated process to be stable and robust. We thank the
Harvard-Smithsonian Summer REU program for making this summer project
possible as well as a grant from NASA (NASA grant NNG05GM44G), and
the NSF for funding the REU program.
Title: Companion Event and Precursor of the X17 Flare on 28 October
2003
Authors: Mandrini, C. H.; Demoulin, P.; Schmieder, B.; Deluca, E. E.;
Pariat, E.; Uddin, W.
Bibcode: 2006SoPh..238..293M
Altcode: 2006SoPh..tmp...79M
A major two-ribbon X17 flare occurred on 28 October 2003, starting
at 11:01 UT in active region NOAA 10486. This flare was accompanied
by the eruption of a filament and by one of the fastest halo coronal
mass ejections registered during the October-November 2003 strong
activity period. We focus on the analysis of magnetic field (SOHO/MDI),
chromospheric (NainiTal observatory and TRACE), and coronal (TRACE) data
obtained before and during the 28 October event. By combining our data
analysis with a model of the coronal magnetic field, we concentrate
on the study of two events starting before the main flare. One
of these events, evident in TRACE images around one hour prior to
the main flare, involves a localized magnetic reconnection process
associated with the presence of a coronal magnetic null point. This
event extends as long as the major flare and we conclude that it is
independent from it. A second event, visible in Hα and TRACE images,
simultaneous with the previous one, involves a large-scale quadrupolar
reconnection process that contributes to decrease the magnetic field
tension in the overlaying field configuration; this allows the filament
to erupt in a way similar to that proposed by the breakout model,
but with magnetic reconnection occurring at Quasi-Separatrix Layers
(QSLs) rather than at a magnetic null point.
Title: SOHO Observations of Polar Coronal Jets over the Last Solar
Cycle
Authors: Dobrzycka, Danuta; Raymond, J.; DeLuca, E.; Guman, J.;
Fludra, A.; Biesecker, D.
Bibcode: 2006ESASP.617E..87D
Altcode: 2006soho...17E..87D
No abstract at ADS
Title: The Nature and Time-variability of TRACE Moss
Authors: Lin, Li Wei; Kashya, V.; Cirtain, J.; Deluca, E.; Drake,
J.; Weber, M.
Bibcode: 2006SPD....37.0102L
Altcode: 2006BAAS...38..215L
The nature of coronal "moss" seen in Transition Region and Coronal
Explorer (TRACE) images is investigated using a time series set of
SOHO Coronal Diagnostic Spectrometer (CDS) and TRACE measurements of
a moss region seen face-on. Spectral line fluxes obtained at different
times are used to construct differential emission measure distribution
snapshots in the moss line-of-sight, paying special attention to
subtraction of background from unassociated structures. The results
are used to investigate the variability of the moss itself and of the
purported overlying hot loops whose footpoints Berger et al (1999)
and Fletcher & De Pontieu (1999) have proposed as the origin of
the moss emission. We conclude by discussing whether or not the loop
footpoint nature of moss is compatible with our observations.
Title: The Non-Potential Structure of Solar Active Regions
Authors: DeLuca, Edward E.; van Ballegooijen, A.; Bobra, M.
Bibcode: 2006AAS...208.6508D
Altcode: 2006BAAS...38R.145D
Various methods for constructing 3D models of the coronal field are
discussed. The flux-rope insertion method is found to give a good fit to
TRACE observations of coronal loops near an H-alpha filament. Data from
the Advanced Stokes Polarimeter is used for extrapolating photospheric
vector fields into the corona. Tests indicate that models based on
chromospheric vector-field data are more reliable than those based on
photospheric data.
Title: The Atmospheric Imaging Assembly (AIA) for the Solar Dynamics
Observatory
Authors: Smith, Peter L.; Golub, L.; Bookbinder, J. A.; Reid, P. B.;
Deluca, E. E.; Cheimets, P. N.; Podgorski, W. A.; Title, A. M.; Lemen,
J. R.; Boerner, P. F.; SAO, Science, and LMSAL Engineering Teams
Bibcode: 2006SPD....37.0119S
Altcode: 2006BAAS...38Q.218S
The Atmospheric Imaging Assembly (AIA) is being developed for the
Solar Dynamics Observatory (SDO), which is designed to study the
Sun as part of NASA's Living With a Star program. AIA comprises
four normal-incidence telescopes with multilayer-coated optics;
entrance-aperture and focal-plane filters limit the bandpasses. Solar
radiation from the upper solar atmosphere at six wavelengths
corresponding to temperatures between 6.3×105 and
1.5×107 K [Fe IX (171 Å) Fe XII, XXIV (193 Å) Fe XIV
(211 Å) Fe XVI (335 Å) Fe XVIII (94 Å) and Fe XX, XXIII (131 Å)]
will be recorded with high spatial resolution (0.6 arcsec pixels). Other
channels enable observations of the chromosphere (He II 304 Å C IV
1550 Å) and the photosphere. Each telescope contains a 4096 x 4096
CCD camera system and has a 41 arcmin field of view. AIA will return 8
full-solar-disk images every 10 s. The 5-year SDO mission is scheduled
to launch in late 2008. The imaging performance of the telescopes,
which are being provided by the Smithsonian Astrophysical Observatory,
and performance of the multilayer coatings, which are responsible for
the large effective area of AIA, will be discussed in the context of
AIA science goals.
Title: The Hi-C Sounding Rocket Experiment
Authors: Golub, Leon; Cirtain, J.; DeLuca, E.; Nystrom, G.; Kankelborg,
C.; Klumpar, D.; Longcope, D.; Martens, P.
Bibcode: 2006SPD....37.0605G
Altcode: 2006BAAS...38R.226G
The High-resolution Coronal Imager, Hi-C, is a pathfinder
mission designed to place significant new limits on theories of
coronal heating and dynamics by measuring the structures at size
scales relevant to reconnection physics. The Hi-C instrument uses
normal-incidence EUV multilayer technology, as developed in the
NIXT and TRACE programs. A dual-channel long focal-length telescope
and large format back-illuminated CCD camera provide spectroscopic
imaging of the corona at 0.1 arcsec resolution.The main objective of
the Hi-C investigation is to determine the geometric configuration and
topology of the structures making up the inner corona. The secondary
objective is to examine the dynamics of those structures, within the
constraints of the 300-seconds of observing time available from a
sounding rocket. The mission is designed to study the mechanisms for
growth, diffusion and reconnection of magnetic fields, and to help
understand the coupling of small-scale dynamic and eruptive processes
to large-scale dynamics.Hi-C will benefit from a unique coordinated
observation opportunity with investigations such as AIA on SDO, XRT on
Solar-B, and STEREO. Hi-C will address basic plasma physics science
goals of the SSSC by observing the small-scale processes that are
ubiquitous in hot magnetized coronal plasma. The scientific objectives
of Hi-C are central to the SSSC goal of understanding the Sun's activity
and its effects on the terrestrial environment, by providing unique
and unprecedented views of the dynamic activity in the solar atmosphere.
Title: Modeling Non-Potential Fields in Solar Active Regions
Authors: Bobra, Monica; DeLuca, E. E.; Van Ballegooijen, A. A.
Bibcode: 2006SPD....37.0112B
Altcode: 2006BAAS...38..217B
Many models aim to reproduce the non-linear force-free fields in
the solar corona; in this particular study, the magnetofrictional
relaxation method is tested. This method produces non-linear force-free
fields from line-of-sight magnetograms and uses ground-based H-alpha
images to define the location of a filament. Testing the model involves
comparing the model's results to TRACE observations of highly sheared,
non-potential magnetic field structures in several non-flaring active
regions. Preliminary results from such tests are presented. This work
is supported by NASA LWS grant NNG05GK32G.
Title: Using High Cadence TRACE Observations for Coronal Hole
Boundary Analysis
Authors: Jibben, Patricia R.; Kahler, S. W.; DeLuca, E.
Bibcode: 2006SPD....37.1002J
Altcode: 2006BAAS...38..237J
When combined with MDI magnetograms and ground based 10830 images, TRACE
EUV observations can be used to study the boundaries of coronal holes
with high time resolution. Potential source surface field solutions
based on MDI observations (Schrijver et al., ApJ 2005, 628, 501)
are overlaid on TRACE images to show the relationships between the
photospheric flux, the extrapolated coronal fields and the observed
coronal structures. Examples from several TRACE pointing along a
long-lived CH on 9-Dec-2000 are used to demonstrate the method. A
summary of candidate TRACE observations is presented.
Title: The Coronal Loop Controversy: Resolved!
Authors: Schmelz, Joan T.; Nasraoui, K.; Cirtain, J.; DeLuca, E.;
Del Zanna, G.; Mason, H.
Bibcode: 2006SPD....37.1701S
Altcode: 2006BAAS...38..245S
Critics have pointed out the shortcomings of CDS coronal loop
temperature analysis - the large pixel size and the slow time
cadence. It is these limitations, some say, that have produced
multithermal results for the loop observed with CDS on 1998 April
20, both along the line of sight and along the loop length. Analysis
of the CDS observations of AR 10250 from 2003 January 17, however,
seem to contradict these critics. Two loops sit side-by-side right
along the slit in this raster, so all pixels in each loop were
observed at the same time. As a result changes as a function of time
will not affect the temperature results. The first loop is observed
primarily in Mg IX (Log T = 6.0) and the second in Si XII (Log T =
6.3). Differential Emission Measure (DEM) analysis of background
subtracted line intensities of pixels in each loop show distinctly
different results. For the first loop, the intensities of the lines
that remain after background subtraction are well fit with a DEM that
collapses to a single spike. In other words, the loop plasma at this
location is isothermal. This proves that it is neither the DEM method
nor the CDS pixel size that produced the multithermal distributions
for the 1998 April 20 loop plasma. In addition the DEM distribution for
the second loop is similar to those produced for the 1998 April 20 loop
and is clearly inconsistent with isothermal plasma. Both distributions
change as a function of position along the loop, with the temperatures
increasing with loop height. Solar physics research at the University
of Memphis is supported by grants from NSF and NASA.
Title: The X-Ray Telescope for Solar-B
Authors: DeLuca, Edward E.; XRT Team
Bibcode: 2006SPD....37.3603D
Altcode: 2006BAAS...38R.260D
Solar-B is the follow-up mission to the very successful Japan/UK/US
Yohkoh mission. Using a combination of optical, EUV and X-ray
instrumentation Solar-B will study the interaction between the
Sun's magnetic field and its corona to increase our understanding of
the causes of solar variability. It is due for launch in September
2006. The X-Ray Telescope on Solar-B (XRT) is the result of a SAO/JAXA
collaboration. We will discuss our plans for XRT early operations,
the capabilities of the telescope and how scientists can get involved
in XRT science program.
Title: Magnetic reconfiguration before the X 17 Solar flare of
October 28 2003
Authors: Schmieder, B.; Mandrini, C. H.; Démoulin, P.; Pariat, E.;
Berlicki, A.; Deluca, E.
Bibcode: 2006AdSpR..37.1313S
Altcode:
An active region (AR) NOAA 10486, which produced a large number of
X-ray flares during October November 2003, was observed during a
multi-wavelength campaign with ground based and space instruments. We
focus our analysis on the observations of October 28, 2003. The
magnetic field was observed with THEMIS (Na D1) and MDI (Ni I), the
chromosphere with THEMIS (Ca II 8542 Å) and with the Meudon heliograph
in Hα, the EUV images with SOHO/EIT and TRACE. Two pre-events started
just before the major X 17 flare. One was related to localized flux
emergence and lasted until the decay phase of the X flare; while the
second one involved a large scale quadrupolar reconnection, that we
infer by modeling the AR magnetic field. Extended dimming areas across
the equator (EIT), large arcades of post-flare loops (TRACE 195 Å)
and a halo CME (LASCO) were observed consequently after the flare. We
perform an extrapolation of the magnetic field above the photosphere
using a linear force-free-field approximation that allows us to find
the connectivity among the four polarities that would be involved
in the quadrupolar reconnection event. The X 17 flare is plausibly
due to the destabilisation of a twisted flux tube, the bottom part
of this magnetic structure can be visualized by the presence of a
filament. The destabilization is caused by converging and shearing
photospheric motions towards the main magnetic inversion line. The
large scale quadrupolar reconnection related to the second pre-event
would favour the opening of the field above the twisted flux tube and,
consequently, the coronal mass ejection.
Title: The Reconnection and Microscale (RAM) Mission in the LWS
Context
Authors: Golub, L.; Deluca, E.
Bibcode: 2005AGUFMSH54A..02G
Altcode:
Hot magnetized plasmas are ubiquitous throughout the universe. The
physics governing the dynamics of such plasmas takes place on remarkably
small spatial and temporal scales, while both the cause of and the
response to this activity occur on large spatial scales. Understanding
the dynamics, energetics, and coupling between magnetic fields and
plasmas are key focal points of research in astro-, space, and solar
physics. Studying the Sun provides unique opportunities to examine these
processes with unprecedented detail and scope unattainable for more
remote objects. Few problems have proved as resistant to solution as the
production of high-energy particles in hot magnetized plasmas. Theory
and observations indicate that both magnetic reconnection and shocks
can accelerate particles to high energies, involving small-scale
structures that ultimately affect a much larger volume. Reconnection
has been invoked to explain a wide range of explosive solar activity,
from surges to coronal mass ejections, requiring the creation and
dissipation of fine-scale currents. The Reconnection and Microscale
(RAM) Mission is focused on understanding these key processes on
the Sun, with particular emphasis on the production of high-energy
particles and radiation. RAM obtains imaging and spectroscopic
data with unprecedented resolution, and distinguishes among proposed
energy-release and particle-acceleration mechanisms by determining the
fine-scale structure of heated and cooling threads, and by observing
the detailed evolution of multithermal plasmas using high-cadence
spectroscopic imaging with broad temperature coverage. Lessons learned
will also be applicable to both laboratory and non-solar magnetoplasmas,
from the magnetosphere to active galaxies.
Title: Isothermal Bias of the ``Filter Ratio'' Method for Observations
of Multithermal Plasma
Authors: Weber, M. A.; Schmelz, J. T.; DeLuca, E. E.; Roames, J. K.
Bibcode: 2005ApJ...635L.101W
Altcode:
An early result from the Transition Region and Coronal Explorer
(TRACE) was that the EUV filter ratios for many narrow coronal loops
(widths of a few arcseconds) were found to cluster within the small
range 0.50-1.70, as functions of position along loop length. The
most common interpretation is that the temperature along the
loop is in fact nearly constant with a value between 1.1 and 1.3
MK. This interpretation has resulted in a class of TRACE loop models
with heating close to the footpoints. We analyze the filter ratio
method to show that the constant TRACE 195 Å/173 Å ratios can be
reproduced by multithermal differential emission measures (DEMs)
along the line of sight over a wide range of peak temperatures, so
long as the distribution is relatively flat and spans the temperature
response of both channels. Furthermore, in the limit of flat (i.e.,
very multithermal) DEMs, the filter ratio method is biased toward the
ratio of the integrals of the temperature response functions. This
result is general to any measurement of intensity ratios that are
formed over a nonzero temperature range (e.g., narrow passbands and
ion emission lines).
Title: Dynamics of Active Region Loops: Temperature Measurements as
a function of Time
Authors: Cirtain, J. J.; del Zanna, G.; Mason, H.; Deluca, E.;
Martens, P.
Bibcode: 2005AGUFMSH44A..03C
Altcode:
The combination of moderate resolution EUV spectroscopy and high
resolution narrow band filter images provides the most accurate
measure of temperature and density for coronal loops to date. We will
demonstrate our technique for combining the data sets from the Coronal
Diagnostic Spectrometer on SoHO and the Transition Region and Coronal
Explorer. Background subtracted spectral intensities are used to
determine the temperature of coronal loops and the TRACE images help
determine the loop cross-section, temporal variability, and filling
factor. The resulting temperature profiles for multiple positions along
a loop leg are determined using the EM LOCI method, and a technique for
determining whether a single temperature can characterize the plasma is
also presented. We compare the results of our study to current models.
Title: The Reconnection and Microscale (RAM) probe
Authors: Golub, Leon; Bookbinder, Jay A.; DeLuca, Edward E.; Karpen,
Judith T.
Bibcode: 2005SPIE.5901..281G
Altcode:
Hot magnetized plasmas - typified by the solar corona - are
ubiquitous throughout the universe. The physics governing the
dynamics of such plasmas takes place on remarkably small spatial
and temporal scales, while both the cause activity and the response
occur on large spatial scales. Thus both high resolution and large
fields of view are needed. Observations from SMM, Yohkoh, EIT and
TRACE show that typical solar active region structures range in
temperature from 0.5 to 10 MK, and up to 40MK in flares, implying
the need for broad temperature coverage. The RAM S-T Probe consists
of a set of imaging and spectroscopic instruments that will enable
definitive studies of fundamental physical processes that govern
not only the solar atmosphere but much of the plasma universe. Few
problems in astrophysics have proved as resistant to solution as the
microphysics that results in the production of high-energy particles
in hot magnetized plasmas. Theoretical models have focused in recent
years on the various ways in which energy may be transported to the
corona, and there dissipated, through the reconnection of magnetic
fields. Theory implies that the actual dissipation of energy in the
corona occurs in spatially highly localized regions, and there is
observational support for unresolved structures with filling factors
0.01 - 0.001 in dynamic coronal events.
Title: Calibration of the Solar-B x-ray optics
Authors: Cosmo, Mario L.; DeLuca, Edward E.; Golub, Leon; Austin,
Gerald K.; Chappell, Jon H.; Barbera, Marco; Bookbinder, Jay A.;
Cheimets, Peter N.; Cirtain, Jonathan; Podgorski, William A.; Davis,
William; Varisco, Salvatore; Weber, Mark A.
Bibcode: 2005SPIE.5900...99C
Altcode:
The Solar-B X-ray telescope (XRT) is a grazing-incidence modified Wolter
I X-ray telescope, of 35 cm inner diameter and 2.7 m focal length. XRT,
designed for full sun imaging over the wavelength 6-60 Angstroms, will
be the highest resolution solar X-Ray telescope ever flown. Images
will be recorded by a 2048 X 2048 back-illuminated CCD with 13.5 μm
pixels (1 arc-sec/pixel ) with full sun field of view. XRT will have
a wide temperature sensitivity in order to observe and discriminate
both the high (5-10 MK) and low temperature (1-5 MK) phenomena in
the coronal plasma. This paper presents preliminary results of the
XRT mirror calibration performed at the X-ray Calibration Facility,
NASA-MSFC, Huntsville, Alabama during January and February 2005. We
discuss the methods and the most significant results of the XRT mirror
performance, namely: characteristics of the point response function
(PSF), the encircled energy and the effective area. The mirror FWHM
is 0.8" when corrected for 1-g, finite source distance, and CCD
pixelization. With the above corrections the encircled energy at 27
μm and 1keV is 52%. The effective area is greater than 2cm2
at 0.5keV and greater than 1.7cm2 at 1.0keV.
Title: SAO/MCLC Solar Dynamics Observatory Partnership
Authors: Deluca, E. E.; Ward, R. B.; Griffin, R.; Liscombe, M.;
Goguen, N.; Mattson, B.; Moriaty, B.; Ruscitti, L.; Lyons, N.
Bibcode: 2005AGUSMSH13D..04D
Altcode:
The Smithsonian Astrophysical Observatory (SAO) and Christa McAuliffe
Challenger Learning Center (MCLC) at Framingham State College have
partnered to design and develop a Sun-Earth mission scenario for use
at Challenger Learning Center simulators nation wide. The simulation
experience, and the solar science embedded within, will be accessible
to students of all capabilities and from every setting, and to general
audiences. We will present the current status of this project, our
educational approach and our plans for the future.
Title: Spicules, mass transfer, oscillations, and the heating of
the corona
Authors: Pasachoff, J. M.; Kozarev, K. A.; Butts, D. L.; Gangestad,
J. W.; Seaton, D. B.; de Pontieu, B.; Golub, L.; Deluca, E.; Wilhelm,
K.; Dammasch, I.
Bibcode: 2005AGUSMSH13C..02P
Altcode:
The mass moving in chromospheric spicules is enough to replace the
corona in a brief time, so understanding the dynamics of spicules
is important for understanding the support and heating of the
solar corona. We have undertaken a program involving simultaneous
high-resolution observations in various chromospheric visible lines
(H-alpha, Ca II H, and G-band, as well as Dopplergrams) using the
Swedish Solar Telescope on La Palma, ultraviolet chromospheric,
transition-region, and coronal lines (Fe IX/X 171 A, Lyman-alpha
1216 A, and continuum/C I/C IV 1600 A) using NASA's TRACE, and
ultraviolet chromospheric and transition-region lines (Si II 1533,
C IV 1548, and Ne VIII 770) using SUMER on SOHO. Our first coordinated
observing run, in May 2004, yielded a variety of images that are under
study, especially for the morphological statistics and dynamics of
spicules. The energy transfer through the chromosphere is relevant to
the overlapping investigation of coronal heating through rapid (1Hz
range) oscillations of coronal loops as observed at total eclipses
by Williams College expeditions. This research is supported by NASA
grant number NNG04GK44G to Williams College. TRACE analysis at SAO
is supported by a contract from Lockheed Martin. SOHO is a project of
international cooperation between ESA and NASA.
Title: Why Does TRACE See So Many Isothermal Loops?
Authors: Weber, M.; Deluca, E.; Schmelz, J.
Bibcode: 2005AGUSMSP13B..03W
Altcode:
The Transition Region and Coronal Explorer (TRACE) has advanced our
view of the dynamics of solar active regions. TRACE brings the highest
spatial resolution and reasonable temporal coverage to bear on the
evolution and structure of coronal plasma; temperature discrimination
is achieved with three narrowband EUV filters and the filter ratio
method. Many thin coronal loops have been observed to have near-constant
filter ratios along their length, which has commonly been interpreted
as evidence for isothermal structure. We discuss and quantify how the
TRACE filter response ratios are biased to estimate relatively constant
isothermal temperatures in the observed range when the plasma along
the line-of-sight is multithermal.
Title: The Calibration of the Solar-B X-ray Telescope (XRT)
Authors: Golub, L.; Barbera, M.; Bookbinder, J.; Cheimets, P.; Cirtain,
J.; Cosmo, M.; Deluca, E.; Podgorski, W.; Sette, A.; Varisco, S.;
Weber, M.
Bibcode: 2005AGUSMSP43A..01G
Altcode:
The Solar-B X-ray telescope (XRT) is designed to have a wide temperature
sensitivity in order to observe and analyze both the high (5-10 MK)
and low temperature (1-5 MK) phenomena in the coronal plasma. It will
be the telescope with the highest resolution ever flown for solar
coronal studies. The telescope is designed for full Sun imaging over
the wavelength range 6-60 Angstroms. The XRT is a grazing-incidence
modified Wolter I X-ray telescope, of 35 cm inner diameter and 2.7
m focal length. The 2048 X 2048 back illuminated CCD has 13.5 µm
pixels, corresponding to 1 arcsecond. The filter set used in the XRT,
mounted at the telescope entrance and near the focal plane, will perform
three functions: (1) to reduce the heat load inside the telescope,
(2) to reduce the incoming visible light and (3) to provide spectral
diagnostics to determine coronal plasma temperatures. This paper
will present the results of the XRT calibration performed at the X-ray
Calibration Facility, NASA-MSFC, Huntsville, Alabama in January 2005. We
will discuss the methods and the most significant results of the XRT
performance, namely: imaging properties, encircled energy, the point
response function and the effective area in the 0.2-2 keV energy range.
Title: EUV Observations of Active Region Dynamics
Authors: Deluca, E. E.; Cirtain, J. W.; del Zanna, G.; Mason, H. E.;
Martens, P. C.; Schmelz, J.; Golub, L.
Bibcode: 2005AGUSMSP33A..03D
Altcode:
Data collected during SoHO JOP 146, in collaboration with TRACE, is
used to investigate the physical characteristics of coronal active
region loops as a function of time and position along and across
loop structures. These data include TRACE images in all three EUV
passbands, and simultaneous CDS spectroscopic observations. Preliminary
measurements of the loop temperature both along the loop half-length
and loop cross-section are presented as a function of time. We will
show the temperature and density profiles of several structures as a
function of position, show changes in temperature and density with time
and characterize the coronal background emission. Questions raised
by these results will be greatly advanced with the high resolution
spectra available from the EIS on Solar-B.
Title: The nearest star: resolving the building blocks of the
coronal DEM
Authors: Lin, L.; Kashyap, V. L.; Drake, J. J.; Deluca, E. E.; Weber,
M.; Sette, A. L.
Bibcode: 2005ESASP.560..757L
Altcode: 2005csss...13..757L
No abstract at ADS
Title: Size of coronal structures in active stellar coronae from
the detection of X-ray resonant scattering
Authors: Testa, P.; Drake, J. J.; Peres, G.; Deluca, E. E.
Bibcode: 2005ESASP.560...43T
Altcode: 2005csss...13...43T
No abstract at ADS
Title: Science of the X-ray Sun: The X-ray telescope on Solar-B
Authors: DeLuca, E. E.; Weber, M. A.; Sette, A. L.; Golub, L.;
Shibasaki, K.; Sakao, T.; Kano, R.
Bibcode: 2005AdSpR..36.1489D
Altcode:
The X-Ray Telescope (XRT) on Solar-B is designed to provide high
resolution, high cadence observations of the X-ray corona through
a wide range of filters. The XRT science team has identified four
general problems in coronal physics as the primary science goals for our
instrument. Each of these goals will require collaborative observations
from the other Solar-B instruments: EUV Imaging Spectrograph (EIS)
and Solar Optical Telescope Focal Plane Package (SOT). We will discuss
the science goals and observations needed to address those goals.
Title: Transverse Oscillations in a Coronal Loop Arcade
Authors: Verwichte, E.; Nakariakov, V. M.; Ofman, L.; Deluca, E. E.
Bibcode: 2004ESASP.575..460V
Altcode: 2004soho...15..460V
No abstract at ADS
Title: Differential Emission Measure Reconstruction with the SolarB
X-Ray Telescope
Authors: Golub, L.; Deluca, E. E.; Sette, A.; Weber, M.
Bibcode: 2004ASPC..325..217G
Altcode:
Two of the main considerations in the design of the SolarB X-Ray
Telescope are temperature coverage and discrimination. We describe how
these factors enter into the design of XRT, as well as the methods
we have developed for producing estimates of emission measures. We
analyze model DEMs to evaluate our ability to reconstruct DEMs.
Title: SolarB X-Ray Telescope (XRT)
Authors: Kano, R.; Hara, H.; Shimojo, M.; Tsuneta, S.; Sakao, T.;
Matsuzaki, K.; Kosugi, T.; Golub, L.; Deluca, E. E.; Bookbinder,
J. A.; Cheimets, P.; Owens, J. K.; Hill, L. D.
Bibcode: 2004ASPC..325...15K
Altcode:
The Soft X-ray Telescope (XRT) aboard SolarB is a grazing incidence
X-ray telescope equipped with 2k × 2k CCD. XRT has 1 arcsec resolution
with wide field-of-view of 34 × 34 arcmin. It is sensitive to
<1 MK to 30 MK, allowing us to obtain TRACE-like low temperature
images as well. Co-alignment with SOT and EIS is realized through
the XRT visible light telescope and with temperature overlap with
EIS. Spacecraft mission data processor (MDP) controls XRT through
the sequence tables with versatile autonomous functions such as
exposure control, region-of-interest tracking, flare detection and
flare location identification. Data are compressed either with DPCM or
JPEG, depending on the purpose. This results in higher cadence and/or
wider field-of-view for given telemetry bandwidth. With focus adjust
mechanism, higher resolution of Gaussian focus may be available on-axis.
Title: Calibration of the XRT-SOLARB flight filters at the XACT
facility of INAF-OAPA
Authors: Barbera, Marco; Artale, Maria Antonella; Candia, Roberto;
Collura, Alfonso; Lullo, Giuseppe; Peres, Giovanni; Perinati, Emanuele;
Varisco, Salvatore; Bookbinder, J. A.; Cheimets, Peter N.; Cosmo,
Mario L.; DeLuca, Edward E.; Golub, Leon; Weber, Mark A.
Bibcode: 2004SPIE.5488..423B
Altcode:
The X-Ray Telescope (XRT) experiment on-board the Japanese satellite
SOLAR-B (launch in 2006) aimed at providing full Sun field of view at ~
1.5" angular resolution, will be equipped with two wheels of focal-plane
filters to select spectral features of X-ray emission from the Solar
corona, and a front-end filter to significantly reduce the visible
light contamination. We present the results of the X-ray calibrations
of the XRT flight filters performed at the X-ray Astronomy Calibration
and Testing (XACT) facility of INAF-OAPA. We describe the instrumental
set-up, the adopted measurement technique, and present the transmission
vs. energy and position measurements.
Title: Calibration of the XRT-SOLARB flat mirror samples at the XACT
Facility of INAF-OAPA
Authors: Artale, Maria Antonella; Barbera, Marco; Collura, Alfonso;
Di Cicca, Gaspare; Peres, Giovanni; Varisco, Salvatore; Bookbinder,
J. A.; Cheimets, Peter N.; Cosmo, Mario L.; DeLuca, Edward E.; Golub,
Leon; Weber, Mark A.
Bibcode: 2004SPIE.5488..440A
Altcode:
The X-Ray Telescope (XRT) experiment on-board the Japanese satellite
SOLAR-B (launch in 2006) is equipped with a modified Wolter I grazing
incidence X-ray telescope (focal length 2700 mm) to image the full Sun
at ~ 1.5" angular resolution onto a 2048 x 2048 back illuminated CCD
focal plane detector. The X-ray telescope consisting of one single
reflecting shell is coated with ion beam sputtered Iridium over a
binding layer of Chromium to provide nearly 5 square centimetres
effective area at 60 Å. We present preliminary results of X-ray
calibrations of the XRT flat mirror samples performed at the X-ray
Astronomy Calibration and Testing (XACT) facility of INAF-OAPA. We
describe the instrumental set-up, the adopted measurement technique,
and present the measured reflectivity vs. angle of incidence at few
energies.
Title: Characteristics of transverse oscillations in a coronal
loop arcade
Authors: Verwichte, E.; Nakariakov, V. M.; Ofman, L.; Deluca, E. E.
Bibcode: 2004SoPh..223...77V
Altcode:
TRACE observations from 15 April 2001 of transverse oscillations in
coronal loops of a post-flare loop arcade are investigated. They
are considered to be standing fast kink oscillations. Oscillation
signatures such as displacement amplitude, period, phase and damping
time are deduced from 9 loops as a function of distance along the loop
length. Multiple oscillation modes are found with different amplitude
profile along the loop length, suggesting the presence of a second
harmonic. The damping times are consistent with the hypothesis of
phase mixing and resonant absorption, although there is a clear bias
towards longer damping times compared with previous studies. The
coronal magnetic field strength and coronal shear viscosity in the
loop arcade are derived.
Title: Magnetic changes observed in the formation of two filaments
in a complex active region: TRACE and MSDP observations
Authors: Schmieder, Brigitte; Mein, Nicole; Deng, Yuanyong; Dumitrache,
Cristiana; Malherbe, Jean-Marie; Staiger, Joachim; Deluca, E. E.
Bibcode: 2004SoPh..223..119S
Altcode:
This paper is focused on the formation of two filaments in a complex
center of decaying active regions (AR 8329 and AR 8326), located in
the northern hemisphere. The observations were obtained in Hα by
the Multi-channel Subtractive Double Pass spectrograph (MSDP mounted
on the German telescope VTT in Tenerife) and EUV lines with TRACE
(Transition Region And Corona Explorer). High Doppler shifts are found
to be related to the ends of filament segments where canceling magnetic
fields are also located (as seen on magnetograms from Big Bear Solar
Observatory). At these locations, velocities along the line of sight,
derived by using a cloud model method reach −20 km s−1,
the segments of filaments merge and frequently a time-related sub-flare
is observed by TRACE. The chirality of the filament segments has been
determined by different methods: the segments of dextral chirality
join together and form a long dextral filament, and a single filament
of sinistral chirality forms end to end with the dextral filament
but does not merge with it. Assuming a model of twisted flux tube for
filament material, we suggest that the dextral filament has negative
helicity and a relationship between its formation and the close by
sunspot with the same sign of helicity.
Title: Detection of X-Ray Resonance Scattering in Active Stellar
Coronae
Authors: Testa, Paola; Drake, Jeremy J.; Peres, Giovanni; DeLuca,
Edward E.
Bibcode: 2004ApJ...609L..79T
Altcode: 2004astro.ph..5520T
An analysis of Lyman series lines arising from hydrogen-like oxygen
and neon ions in the coronae of the active RS CVn-type binaries II Peg
and IM Peg, observed using the Chandra High Resolution Transmission
Grating Spectrograph, shows significant decrements in the Lyα/Lyβ
ratios as compared with theoretical predictions and with the same ratios
observed in similar active binaries. We interpret these decrements in
terms of resonance scattering of line photons out of the line of sight;
these observations present the first strong evidence of this effect in
active stellar coronae. The net line photon loss implies a nonuniform
and asymmetric surface distribution of emitting structures on these
stars. Escape probability arguments, together with the observed line
ratios and estimates of the emitting plasma density, imply typical
line-of-sight sizes of the coronal structures that dominate the X-ray
emission of 1010 cm at temperatures of 3×106 K
and of 108 cm at 107 K. These sizes are an order
of magnitude larger than predicted by simple quasi-static coronal loops
models but are still very small compared to the several 1011
cm radii of the underlying stars.
Title: The Neareset Star: Emission Structure of the Sun's corona
Authors: Lin, L.; Kashyap, V. L.; Drake, J. J.; DeLuca, E. E.; Weber,
M. A.; Sette, A. L.
Bibcode: 2004AAS...204.9508L
Altcode: 2004BAAS...36Q.827L
We describe the application of a sophisticated differential emission
measure (DEM) reconstruction technique to solar observations by
Yohkoh, TRACE, SOHO, and GOES. Based on a Markov-Chain Monte Carlo
algorithm originally developed for use with high resolution stellar
EUV and X-ray spectra, the method is easily adapted to any combination
of observations with different instruments and filters. We derive
DEMs over the temperature range log{T}=5.5-7.5 using full disk solar
observations from the various telescopes to mimic the appearance of the
Sun as a distant star. We then compare the DEMs thus derived with those
obtained for stars based on EUV and X-ray spectroscopy. We also explore
the extent to which Solar-B will enhance our understanding of the
underlying temperature structure of the Solar corona, and describe new
methods to apply to the data cube of a typical Solar-B XRT observation.
Title: Pre-Conditioning Optmization Methods and Display for Mega-Pixel
DEM Reconstructions
Authors: Sette, A. L.; DeLuca, E. E.; Weber, M. A.; Golub, L.
Bibcode: 2004AAS...204.6904S
Altcode: 2004BAAS...36R.794S
The Atmospheric Imaging Assembly (AIA) for the Solar Dynamics
Observatory will provide an unprecedented rate of mega-pixel solar
corona data. This hastens the need for faster differential emission
measure (DEM) reconstruction methods, as well as scientifically
useful ways of displaying this information for mega-pixel datasets. We
investigate pre-conditioning methods, which optimize DEM reconstruction
by making an informed initial DEM guess that takes advantage of the
sharing of DEM information among the pixels in an image. In addition,
we evaluate the effectiveness of different DEM image display options,
including single temperature emission maps and time-progression DEM
movies. This work is supported under contract SP02D4301R to the
Lockheed Martin Corp.
Title: Evidence for Coexisting Hot and Cool Polar Coronal Jets -
Coordinated Observations of SOHO and TRACE
Authors: Dobrzycka, D.; Raymond, J. C.; Deluca, E. E.; Gurman, J.;
Biesecker, D.; Fludra, A.
Bibcode: 2004AGUSMSH52A..05D
Altcode:
The polar coronal jets were first observed by SOHO instruments
(EIT, LASCO, UVCS) during the last solar minimum. They were small,
fast ejections originating from flaring UV bright points within large
polar coronal holes. The polar holes disappeared at solar maximum and
the jets were not visible anymore. Currently, however, as the Sun's
activity declines, the polar holes again became permanent structures
and new polar coronal jets were observed by specially designed SOHO
Joint Observing Program (JOP 155). Their frequency of several events per
day appear comparable to the frequency from last solar minimum. Also,
the speed of ∼ 400~km~s-1 at 1.6~R⊙ is consistent
with typical velocities of polar jets in 1996-1998. The ejections are
believed to be triggered by the field line reconnection between the
emerging magnetic dipole and pre-existing unipolar field. Existing
models predict that the hot jet is ejected together with another jet
made of cool material. The coordinated SOHO and TRACE observations
within JOP 155 provide unique opportunity to test this prediction. We
will present observations and discuss evidence supporting the model.
Title: The Atmospheric Imaging Assembly and Temperature Diagnostics
Authors: Weber, M. A.; Caldwell, D.; Deluca, E. E.; Golub, L.; Sette,
A. L.
Bibcode: 2004AAS...204.6906W
Altcode: 2004BAAS...36..795W
The Atmospheric Imaging Assembly (AIA) will be one of the instruments
on the Solar Dynamics Observatory (SDO). It will image the solar
transition region and corona in multiple EUV and UV wavelengths
simultaneously, using four aligned telescopes. Hence, AIA will be
capable of high-cadence, spatially resolved temperature discrimination
of solar plasmas. We discuss the design of AIA, with focus on its
ability for temperature diagnostics. We consider different methods for
reconstruction of differential emission measures, since this will be
one of the more important data products. This work is supported
under contract SP02D4301R to the Lockheed Martin Corp.
Title: Science with the Solar-B X-Ray Telescope
Authors: Deluca, E. E.; Weber, M. A.; Golub, L.
Bibcode: 2004AAS...204.6905D
Altcode: 2004BAAS...36Q.795D
The Solar-B mission will launch in 2006 with three telescopes:
a high resolution visible light telescope feeding filtergraph and
spectropolarimeter focal plane instruments, a grazing incidence X-Ray
telescope and an EUV spectrograph. This combination of instruments
will provide detailed information on Active Region evolution, heating,
connectivity and dynamics. The X-Ray telescope on Solar-B will be
sensitive to emission from 1-50MK. Focal plane filters will allow us
to follow the evolution of the bulk of the coronal plasma. This poster
will describe the core science that will be done by XRT together with
EIS and SOT. Joint observing programs will also be discussed.
Title: EUV multilayers for solar physics
Authors: Windt, David L.; Donguy, S.; Seely, John F.;
Kjornrattanawanich, Benjawan; Gullikson, Eric M.; Walton, C. C.;
Golub, L.; DeLuca, E.
Bibcode: 2004SPIE.5168....1W
Altcode:
We present an overview of currently available EUV multilayer coatings
that can be used for the construction of solar physics instrumentation
utilizing normal-incidence optics. We describe the performance of
a variety of Si-based multilayers, including Si/B4C and
new Si/SiC films that provide improved performance in the wavelength
range from 25 n 35 nm, as well as traditional Si/Mo multilayers,
including broad-band coatings recently developed for the Solar-B/EIS
instrument. We also outline prospects for operation at both longer and
shorter EUV wavelengths, and also the potential of ultra-short-period
multilayers that work near normal incidence in the soft X-ray region.
Title: Multi-wavelength flare study and magnetic configuration
Authors: Schmieder, Brigitte; Berlicki, A.; Vilmer, N.; Aulanier,
G.; Démoulin, P.; Mein, P.; Mandrini, C.; Deluca, E.
Bibcode: 2004IAUS..223..397S
Altcode: 2005IAUS..223..397S
Recent results of two observation campaigns (October 2002 and October
2003) are presented with the objective of understanding the onset
of flares and CMEs. The magnetic field was observed with THEMIS and
MDI, the chromosphere with the MSDP operating on the German telescope
VTT and on THEMIS, the EUV images with SOHO/CDS and TRACE, the X-ray
with RHESSI. We show how important is the magnetic configuration of
the active region to produce CMEs using two examples: the October 28
2003 X 17 flare and the October 22 2002 M 1.1 flare. The X 17 flare
gave a halo CME while the M 1.1 flare has no corresponding CME. The
magnetic topology analysis of the active regions is processed with a
linear-force-free field configuration.
Title: Multi-Wavelength Observations of an M1.0 Flare on 22 October
2002
Authors: Berlicki, A.; Schmieder, B.; Vilmer, N.; Mein, P.; Mein,
N.; Heinzel, P.; Staiger, J.; Deluca, E. E.
Bibcode: 2004IAUS..219..669B
Altcode:
No abstract at ADS
Title: Temperature diagnostics with multichannel imaging telescopes
Authors: Weber, M. A.; Deluca, E. E.; Golub, L.; Sette, A. L.
Bibcode: 2004IAUS..223..321W
Altcode: 2005IAUS..223..321W
Modern solar telescope design in the EUV to x-ray range is now capable
of producing large images in multiple channels at rapid cadences, with
high spatial and temperature resolution. We discuss reconstruction
of differential emission measures for solar coronal plasma using two
state-of-the-art instruments: the X-Ray Telescope on Solar-B, and the
Atmospheric Imaging Assembly on the Solar Dynamics Observatory. We
discuss the relative merits of iteration and direct inversion methods
for determining DEM(T). We also consider strategies for automating and
visualizing DEM maps, given the high data rates that these instruments
will produce. We touch on the scientific potential of high-cadence,
spatially resolved DEM data products.
Title: Origins of the Solar Polar Jets - Coordinated SOHO and TRACE
Observations
Authors: Dobrzycka, D.; Raymond, J. C.; Deluca, E. E.; Gurman, J. B.;
Biesecker, D.; Fludra, A.
Bibcode: 2003AGUFMSH22A0187D
Altcode:
The polar jets are dynamic coronal eruptions originating in the low
solar atmosphere, in flaring UV bright points within polar coronal
holes. They were first observed by SOHO instruments (EIT, LASCO)
during last solar minimum in 1996 when the polar holes were dominating
coronal structures. UVCS/SOHO obtained ultraviolet spectroscopy of
the jet providing us with estimates of the jet plasma conditions,
evolution of the electron temperature and heating rate required to
reproduce the observed ionization state. As the Sun is currently at
the declining phase of its activity, the polar holes again became
permanent structures. The SOHO Joint Observing Program (JOP 155)
was designed to identify and study the jet phenomena that would be
counterparts of the solar minimum polar jets. The jets are believed
to be triggered by field line reconnection between emerging magnetic
dipole and pre-existing unipolar field. Existing models predict that the
hot jet is ejected together with another jet of a cool material. The
particular goal of the coordinated SOHO and TRACE observations was to
look for possible association of the hot and cool plasma ejections. We
present first results of the campaign and discuss their implications.
Title: Constraints on Active Region Coronal Heating
Authors: Antiochos, S. K.; Karpen, J. T.; DeLuca, E. E.; Golub, L.;
Hamilton, P.
Bibcode: 2003ApJ...590..547A
Altcode:
We derive constraints on the time variability of coronal heating from
observations of the so-called active region moss by the Transition
Region and Coronal Explorer (TRACE). The moss is believed to be due to
million-degree emission from the transition regions at the footpoints
of coronal loops whose maximum temperatures are several million
degrees. The two key results from the TRACE observations discussed in
this paper are that in the moss regions one generally sees only moss,
not million-degree loops, and that the moss emission exhibits only weak
intensity variations, ~10% over periods of hours. TRACE movies showing
these results are presented. We demonstrate, using both analytic and
numerical calculations, that the lack of observable million-degree
loops in the moss regions places severe constraints on the possible
time variability of coronal heating in the loops overlying the moss. In
particular, the heating in the hot moss loops cannot be truly flarelike
with a sharp cutoff, but instead must be quasi-steady to an excellent
approximation. Furthermore, the lack of significant variations in
the moss intensity implies that the heating magnitude is only weakly
varying. The implications of these conclusions for coronal heating
models will be discussed.
Title: Propagating EUV disturbances in the Solar corona:
Two-wavelength observations
Authors: King, D. B.; Nakariakov, V. M.; Deluca, E. E.; Golub, L.;
McClements, K. G.
Bibcode: 2003A&A...404L...1K
Altcode:
Quasi-periodic EUV disturbances simultaneously observed in 171 Å and
195 Å TRACE bandpasses propagating outwardly in a fan-like magnetic
structure of a coronal active region are analysed. Time series of
disturbances observed in the different bandpasses have a relatively
high correlation coefficient (up to about 0.7). The correlation has
a tendency to decrease with distance along the structure: this is
consistent with an interpretation of the disturbances in terms of
parallel-propagating slow magnetoacoustic waves. The wavelet analysis
does not show a significant difference between waves observed in
different bandpasses. Periodic patterns of two distinct periods: 2-3 min
and 5-8 min are detected in both bandpasses, existing simultaneously
and at the same distance along the loop, suggesting the nonlinear
generation of the second harmonics.
Title: Coronal Loop Differential Emission Measures from TRACE and
CDS Observations
Authors: Hamilton, P. S.; DeLuca, E. E.; Johnson, K.
Bibcode: 2003SPD....34.1707H
Altcode: 2003BAAS...35..838H
There has been much recent discussion about the nature of active
region coronal loops detected by the Transition Region and Coronal
Explorer (TRACE) observations. Using several sets of co-aligned CDS
and TRACE observations we perform a DEM analysis on both loop and
nearby background plasma. We find that these loops contain material
at 105.9 K to 106.2 K. Finally we examine how
this information can be used to constrain the input parameters to
time-dependent hydrodynamic models of these loops. TRACE is
supported by contract NAS5-38099 from NASA to LMATC.
Title: The High Resolution Imager on the Reconnection and Microscale
(RAM) Mission
Authors: Bookbinder, J. A.; DeLuca, E. E.; Golub, L.; Weber, M.;
Karpen, J. T.
Bibcode: 2003SPD....34.2404B
Altcode: 2003BAAS...35..853B
Hot, magnetized plasmas such as the solar corona have the property that
much of the physics governing its activity takes place on remarkably
small spatial and temporal scales, while the response to this activity
occurs on large scales. Future progress on the challenging solar
physics issues of eruptive flares, coronal heating and the initial of
the solar wind requires observations on spatial and temporal scales
relevant to the observable signatures of the underlying physical
processes. These spatial and temporal domains - in the relevant
temperature regimes - have been heretofore inaccessible to direct
observations from Earth, with the result that theoretical efforts have
relied heavily on extrapolations from more accessible regimes. The
RAM Solar-Terrestrial Probe consists of a set of carefully selected
imaging and spectroscopic instruments that enable definitive studies of
the dynamics and energetics of the solar corona. We present an overview
of the synergism inherent in the RAM instrument suite, with emphasis
on the rationale for, and the capability of, its high-resolution imager.
Title: Moss Loop Cooling in the TRACE 171A Passband
Authors: Weber, M. A.; Seaton, D. B.; DeLuca, E. E.; Lee, E.
Bibcode: 2003SPD....34.1704W
Altcode: 2003BAAS...35..838W
There is clear evidence that ``moss'' (hot, low-altitude plasma seen
in the 171Å passband of the Transition Region and Coronal Explorer)
is transition region emission at the footpoints of hot ( ∼ 3-5 MK)
coronal loops overlying plage regions. Since the radiative cooling
time for these loops (> 10 minutes) is greater than TRACE's typical
cadence in 171Å, one expects to observe these loops cool through the
passband as the moss boundary evolves. This poster reports on our study
of the co-evolution of moss/plage boundaries with cooling loops. TRACE is supported by contract NAS 5-38099 from NASA to LMATC.
Title: Coronal `Tadpoles' Observed by TRACE
Authors: Seaton, D. B.; Deluca, E. E.; Cooper, F. C.; Nakariakov, V. M.
Bibcode: 2003SPD....34.1618S
Altcode: 2003BAAS...35..836S
The X1.5 flare event observed by TRACE in 195 Å on 21 April 2002,
showed dark, downward-propagating features over the flare arcade which
we call `coronal tadpoles.' We analyzed these features and determined
their distinguishing characteristics. Estimating plasma densities
inside the features, we determined that they are of very low density
and possibly >10 million K. We propose that the coronal tadpoles
my be interpreted in terms of kink modes of the flaring current sheet
filled by hot, rarefied plasma.
Title: Exploration of Stability Regime for Coronal Loops with
Asymmetric Footpoint Heating
Authors: Boyd, J. F.; Weber, M. A.; DeLuca, E. E.; Van Ballegooijen,
A. A.
Bibcode: 2003SPD....34.0405B
Altcode: 2003BAAS...35..811B
We use an iterative code developed by Van Ballegooijen and Hussain
to compute steady state solutions of the hydrodynamic equations
for a one-dimensional coronal loop model with asymmetric footpoint
heating. We vary the loop length and heating scale height to construct
a two-dimensional parameter space similar to that of Aschwanden et
al. (2001). This parameter space contains a boundary that divides a
regime where steady state solutions exist from the regime where there
are no steady state solutions. In this poster we vary the heating scale
height and explore the onset of instability using a state-of-the-art
adaptive mesh code called FLASH to solve the time-dependent hydrodynamic
equations for the one-dimensional coronal loop model with asymmetric
footpoint heating. TRACE is supported by contract NAS5-38099
from NASA to LMATC. The software used in this work was in part
developed by the DOE-supported ASCI/Alliance Center for Astrophysical
Thermonuclear Flashes at the University of Chicago.
Title: DECoDE: The Dual-channel EUV Coronal Dynamics Explorer
Authors: DeLuca, E.
Bibcode: 2003SPD....34.2005D
Altcode: 2003BAAS...35..845D
DECoDE, the Dual-channel EUV Coronal Dynamics Explorer, is designed to
achieve a specific set of mission objectives which are crucial to an
improved understanding of fundamental processes in plasma astrophysics
and the drivers of space weather. \begin{bf} Establish the magnetic
connectivity, energy and mass transport between the solar chromosphere
and corona. Resolve the internal structure of coronal loops, the
basic elements of coronal EUV and soft X-ray emission. Explore
the relationship between small scale reconnection, changes in magnetic
topology, and the global scale instabilites that drive space weather. These science objectives follow logically from NASA's objectives laid
out in the `2003 Strategic Plan for NASA,' and in the 2002 SEC Roadmap.
Title: The Reconnection And Microscale (RAM) Solar-Terrestrial Probe
Authors: Bookbinder, Jay A.; DeLuca, Edward; Cheimets, Peter; Golub,
Leon; Hassler, Donald M.; Korendyke, Clarence M.; Glenn, Paul E.;
Silver, Eric H.
Bibcode: 2003SPIE.4853..436B
Altcode:
A hot, magnetized plasma such as the solar corona has the property that
much of the physics governing its activity takes place on remarkably
small spatial and temporal scales, while the response to this activity
occurs on large scales. Observations from SMM, TRACE, SOHO and Yohkoh
have shown that typical solar active regions have loops ranging in
temperature from 0.5 to 10 MK, and flares up to 40MK. The spatial
and temporal domains involved have been heretofore inaccessible to
direct observations from Earth, so that theory has relied heavily on
extrapolations from more accessible regimes, and on speculation. The
RAM Solar-Terrestrial Probe consists of a set of carefully selected
imaging and spectroscopic instruments that enable definitive studies
of the dynamics and energetics of the solar corona.
Title: Tracking the processing status of Chandra observations
Authors: Winkelman, Sherry L.; Rots, Arnold; DeLuca, Edward E.;
Paltani, Stephane; Hall, Diane
Bibcode: 2002SPIE.4844..485W
Altcode:
The Chandra Data Archive has been archiving and distributing data
for the Chandra X-ray Observatory and keeping observers informed of
the status of their observations since shortly after launch in July
1999. Due to the complicated processing history of Chandra data,
it became apparent that a database was needed to track this history
on an observation by observation basis. The result is the Processing
Status Database and the Chandra Observations Processing Status tool. In
this paper, a description of the database design is given, followed
by details of the tools which populate and display the database.
Title: Chandra Data Archive Operations
Authors: Rots, Arnold H.; Winkelman, Sherry L.; Paltani, Stéphane;
DeLuca, Edward E.
Bibcode: 2002SPIE.4844..172R
Altcode:
The Chandra Data Archive plays a central role in the Chandra
X-ray Center (CXC) that manages the operations of the Chandra X-ray
Observatory. We shall give an overview of two salient aspects of the
CDA's operations, as they are pertinent to the operation of any large
observatory. First, in the database design it was decided to have a
single observation catalog database that controls the entire life cycle
of Chandra observations (as opposed to separate databases for uplink
and downlink, as is common for many scientific space missions). We will
discuss the pros and cons of this design choice and present some lessons
learnt. Second, we shall review the complicated network that consists
of Automated (pipeline) Processing, archive ingest, Verification &
Validation, reprocessing, data distribution, and public release of
observations. The CXC is required to deliver high-level products to its
users. This is achieved through a sophisticated system of processing
pipelines. However, occasional failures as well as the need to reprocess
observations complicate this seemingly simple series of actions. In
addition, we need to keep track of allotted and used observing time
and of proprietary periods. Central to the solution is the Processing
Status Database which is described in more detail in a related poster
presentation.
Title: The Timing of Flares Associated with the Two Dynamical Types
of Solar Coronal Mass Ejections
Authors: Zhang, M.; Golub, L.; DeLuca, E.; Burkepile, J.
Bibcode: 2002ApJ...574L..97Z
Altcode:
In this Letter, we consider a sample of Transition Region and Coronal
Explorer flare-associated solar coronal mass ejections (CMEs) and study
the timing behavior of the flares associated with fast or slow CMEs. We
find that flares associated with fast CMEs tend to happen within half
an hour of the CME onsets, while the timing of flares associated with
slow CMEs is only loosely related to the CME onsets. This suggests that
the occurrence of flares may be integral to the early development of
fast CMEs but is not crucial for slow CMEs. This observational result
supports a recent qualitative theory of the initiation and expulsion
mechanism of the two dynamical types of CMEs.
Title: TRACE Active Region Loops: Observation and Modeling
Authors: Hamilton, P. S.; Warren, H. P.; DeLuca, E. E.; Boyd, J. F.
Bibcode: 2002AAS...200.0210H
Altcode: 2002BAAS...34..641H
Recent Transition Region and Coronal Explorer (TRACE) observations have
detected active region coronal loops that can not be easily modeled
using hydrostatic models. Analysis of these loops suggests that they
are overdense relative to the predictions of hydrodynamic models with
uniform heating. This modeling, however, assumes that the observed
emission is near 1 MK. Since the TRACE filter ratios are actually
multivalued and high-temperature, uniformly heated models are difficult
to exclude based on the TRACE data alone. Using co-aligned CDS rasters
of overdense TRACE loops we find that these loops contain material at
105.9 K to 106.2 K. From these rasters we perform
a DEM analysis to constrain the input parameters to time-dependent
hydrodynamic models of these loops. TRACE is supported by contract
NAS5-38099 from NASA to LMATC.
Title: Active Region Loop Heating
Authors: Antiochos, S. K.; Karpen, J. T.; DeLuca, E. E.; Golub, L.;
Hamilton, P.
Bibcode: 2002AAS...200.1606A
Altcode: 2002BAAS...34..668A
A long-standing unresolved question in solar physics is whether the
heating in coronal loops is steady or impulsive. X-ray observations
of high-temperature loops (T > 2 x 106 K) tend to
show quasi-steady structures, (evolution slow compared to cooling
time scales), whereas theoretical models strongly favor impulsive
heating. We present simulations of impulsively heated loops using
our adaptive-mesh-refinement code ARGOS, and compare the results with
TRACE observations of the transition regions of high-temperature active
region loops. From this comparison, we deduce that the heating in the
core of active regions is quasi-steady rather than impulsive. These
results pose a formidable challenge to developing theoretical models
for the heating. This work was supported in part by NASA and ONR.
Title: The Reconnection and Microscale (RAM) Mission
Authors: Bookbinder, J. A.; DeLuca, E. E.; Golub, L.
Bibcode: 2002AAS...200.5609B
Altcode: 2002BAAS...34Q.736B
Hot magnetized plasmas - typified by the solar corona - are ubiquitous
throughout the universe. The physics governing the dynamics of
such plasmas takes place on remarkably small spatial and temporal
scales, while both the cause activity and the response occur on large
spatial scales. Thus both high resolution and large fields of view are
needed. Observations show that typical solar active region structures
range in temperature from 0.5 to 10 MK, and up to 40 MK in flares,
implying the need for broad temperature coverage. The RAM mission is
designed to meet the observational requirements of the next generation
Solar observatory; we present an overview of the proposed ST-Probe
class mission concept, instrument complement, and technology status. We
emphasize the capabilities and status of the instrument suite that
is proposed: a set of imaging and spectroscopic instruments that will
enable definitive studies of fundamental physical processes that govern
not only the solar atmosphere but much of the plasma universe. The
imaging instruments on RAM combine extremely high spatial resolution
in the corona ( ~10 km) with intermediate scale ( ~70 km) large FOV
observations at several complementary passbands/temperatures. The
spectroscopic instruments offer high resolution ( ~70 km spatial,
~5 km/s velocity) imaging EUV spectroscopy and a photon counting
imaging X-ray micro-calorimeter array offers ( ~700 km, 2 eV energy,
~10 msec time) over a bandpass from 0.2 to >40 keV.
Title: A New Code for Simulating Dynamic Coronal Loops
Authors: Boyd, J. F.; DeLuca, E. E.; van Ballegooijen, A. A.; Arber,
T. D.
Bibcode: 2002AAS...200.0211B
Altcode: 2002BAAS...34..641B
Recent observations with TRACE suggest that apparently steady
coronal loops are inconsistent with hydrostatic loop models. We
present results from a new hydrodynamic code that will be used to
model recent observations from TRACE, SOHO and HESSI. In this poster
we describe the code and show detail comparisons between the results
from this code and a range of loop models. The validation of the code
is an ongoing process, but the simulations we have run to-date suggest
that it will be extremely useful for the testing of detailed heating
models by comparison of forward models with detailed multi-wavelength
observations. Other posters at this meeting will present applications
of this code to active region loops and flares. TRACE is supported by
contract NAS5-38099 from NASA to LMATC.
Title: Science Objectives of the Reconnection and Micrcoscale (RAM)
Solar-Terrestrial Probe
Authors: DeLuca, E. E.; Bookbinder, J.; Golub, L.
Bibcode: 2002AAS...200.8801D
Altcode: 2002BAAS...34..789D
The RAM mission is designed to address fundamental questions related
to the origin and dynamics of hot magnetized plasmas throughout
the universe. Observations of the solar corona demonstrate that
the important physical processes take place on small spatial
and temporal scales, while the energy driving these processes is
stored on large scales, and the response can affect the global
structure of the corona. In this talk we discuss the theoretical
and observational evidence for the existence of small-scale coronal
structures, and outline the observational requirements to answer the
following fundamental questions that apply to all coronal plasmas:
(1) What are the conditions that lead to magnetic reconnection? (2)
What micro-scale instabilities lead to global effects? (3) Where are
the regions of particle acceleration? (4) Where are the reconnection
regions and what is their topology? A companion poster will present the
baseline instrument complement that will achieve these observational
requirements.
Title: Hydrodynamic Modeling of Flare Loops
Authors: Reeves, K. K.; Warren, H. P.; DeLuca, E. E.; Boyd, J. F.;
Arber, T. D.
Bibcode: 2002AAS...200.6811R
Altcode: 2002BAAS...34..757R
The study of post-flare loops is instrumental to understanding the
energy deposition in flares. Previously we modeled the evolution of
a flare arcade using a set of scaling laws for the conductive and
radiative cooling of post-flare loops. We found that these simulated
loops decrease in intensity faster than the observed loops. The scaling
laws, however, did not allow for heating during the decay of the flare,
or provide information on variations in temperature and density along
the loop. In the current work, we use a full hydrodynamic simulation
to investigate energy deposition in flaring loops. We will compare our
simulated flare arcades to spatially and temporally resolved TRACE,
SXT and HESSI observations. This work has been supported in part by
the NASA Sun-Earth Connection Guest Investigator Program. TRACE is
supported by Contract NAS5-38099 from NASA to LMATC.
Title: Influence of Coronal Abundance Variations
Authors: DeLuca, E. E.
Bibcode: 2002STIN...0251207D
Altcode:
The Multispecies loop modeling project addresses the modeling of TRACE
and SOHO observations as a plasma rather than a single fluid. In the
single-fluid approximation the effects of heavy species are considered
in an averaged sense. Further, loop abundances are usually taken to
be uniform throughout the loop, in spite of observational evidence
for considerable variation in coroner abundances.
Title: A photometric imaging solar telescope, tunable in the extreme
ultraviolet, utilizing multilayer x-ray optics
Authors: Golub, L.; Deluca, E.; Hamilton, P.; Nystrom, G.; Windt,
D. L.; Schmidt, W. K. H.; Dannenberg, A.
Bibcode: 2002RScI...73.1908G
Altcode:
We present a new instrument for space-based observational solar physics,
recently flown successfully on a sounding rocket, designed to provide
high spatial resolution, time-resolved images of the solar corona at
specific wavelengths in the extreme ultraviolet (XUV). The primary
instrument employs multilayer x-ray mirrors in a novel geometry that
affords quasi-monochromatic imaging at wavelengths tunable continuously
over the spectral range from 17.1 to 21.1 nm. The secondary instrument
also uses multilayer x-ray mirrors to provide high-resolution imaging
at three fixed XUV wavelength bands. Both instruments use charge
coupled device detectors and thin A1 filters for rejection of unwanted
wavelengths. We describe the design, construction, and performance of
the instrument and discuss prospects for the future.
Title: Steady Flows Detected in Extreme-Ultraviolet Loops
Authors: Winebarger, Amy R.; Warren, Harry; van Ballegooijen, Adriaan;
DeLuca, Edward E.; Golub, Leon
Bibcode: 2002ApJ...567L..89W
Altcode:
Recent Transition Region and Coronal Explorer (TRACE) observations have
detected a class of active region loops whose physical properties are
inconsistent with previous hydrostatic loop models. In this Letter we
present the first co-aligned TRACE and the Solar Ultraviolet Measurement
of Emitted Radiation (SUMER) observations of these loops. Although these
loops appear static in the TRACE images, SUMER detects line-of-sight
flows along the loops of up to 40 km s-1. The presence
of flows could imply an asymmetric heating function; such a heating
function would be expected for heating that is proportional to
(often asymmetric) footpoint field strength. We compare a steady flow
solution resulting from an asymmetric heating function to a static
solution resulting from a uniform heating function in a hypothetical
coronal loop. We find that the characteristics associated with the
asymmetrically heated loop better compare with the characteristics of
the loops observed in the TRACE data.
Title: Magnetic structure and reconnection of x-ray bright points
in the solar corona
Authors: Brown, D. S.; Parnell, C. E.; DeLuca, E. E.; McMullen, R. A.;
Golub, L.; Priest, E. R.
Bibcode: 2002AdSpR..29.1093B
Altcode:
The three-dimensional magnetic topology of the solar corona is
incredibly complex and its effect on the nature of 3D reconnection is
profound. We study the supposedly simple topology of a small scale X-ray
bright point observed by TRACE and SOHO/MDI, and how it is driven by
reconnection when it forms and during the early stages of its lifetime.
Title: Investigation of Non-steady Flow Solutions in the Coronal
Heating Problem
Authors: Boyd, J. F.; DeLuca, E. E.; Reeves, K. K.; Winebarger, A. R.
Bibcode: 2001AGUFMSH11A0691B
Altcode:
Observations made by the TRACE satellite show intermittent intensity
fluctuations in coronal loops that suggest non-steady mass flows. These
flows are not explained by previous work on coronal loop models, which
focus on static and steady flow solutions. To investigate these flows
we have written a code that looks for thermally stable, non-steady
solutions to the hydrodynamic equations that govern coronal loops. These
solutions will be used to determine if an asymmetric heating function
reproduces the observed intensities.
Title: On the Time Variability of Coronal Heating
Authors: Antiochos, S. K.; Karpen, J. T.; DeLuca, E. E.; Golub, L.;
Hamilton, P.
Bibcode: 2001AGUFMSH11A0690A
Altcode:
We derive constraints on the time variability of coronal heating from
observations of the so-called active-region moss by the Transition
and Coronal Explorer (TRACE). The moss is believed to be due to
million-degree emission from the transition regions at the footpoints
of coronal loops whose maximum temperatures are several million
degrees. The key point of the TRACE observations is that in the
moss regions one generally sees only moss, and not million degree
loops. TRACE movies showing this result will be presented. We will
demonstrate using both analytic and numerical calculations, that the
lack of observable million-degree loops in the moss regions places
severe constraints on the possible time variability of coronal heating
in the loops overlying the moss. In particular, the heating in the hot
moss loops cannot be truly flare-like with a sharp cutoff, but instead,
must be quasi-steady to an excellent approximation. The implications
of this result for coronal heating models will be discussed. This work
was supported in part by NASA and ONR
Title: New Observations of Oscillating Coronal Loops
Authors: Reeves, K. K.; Shoer, J.; Deluca, E. E.; Winebarger, A. R.;
Ofman, L.; Davila, J. M.
Bibcode: 2001AGUFMSH11A0704R
Altcode:
One of the most promising discoveries of the TRACE mission is the first
observations of transverse oscillations in coronal loops (Aschwanden
et al 1999, Nakariakov et al 1999). Loops are set into motion from
nearby flares, oscillate with a well defined frequency and decay
on a time scale of 10 minutes. While the theoretical study of MHD
waves in the corona has a long history, observational support has
dramatically increased over the past 10 years as coronal instruments
have improved. The transverse oscillations have been identified as
standing kink modes for the 14-July-1998 observations cited above. In
this paper we present clear evidence for a decaying global kink modes
observed by TRACE on 15-Apr-2001. Six different loops have been observed
to oscillate with a frequency in the range: 15-20 mHz (compared with
4 mHz for 14-July-1998) and a decay time in the range: 8-23 minutes
(compared with 11 minutes for the earlier event). The implications
for these results for coronal diagnostics and solar coronal seismology
will be discussed.
Title: Impulsive Events and Coronal Loop Cooling Observed with TRACE
Authors: Seaton, D. B.; DeLuca, E. E.; Golub, L.; Reeves, K. K.;
Winebarger, A. R.; Gallagher, P. T.
Bibcode: 2001AGUFMSH11A0705S
Altcode:
Nearly every active region imaged by TRACE contains sporadic
brightenings in coronal loops. Many of these ubiquitous, short-lived
events appear nearly simultaneously in the Fe IX/X (log T
e≈ 6.0) and the C IV channel (log T≈ 5.0); hence, we interpret
them as the rapid cooling of a multifilament loops. A particularly good
example of such an event was observed on 21, June 2001, as part of an
hour long active region observation; a total of 52 of the TRACE 171
Å and 68 TRACE 1600 Å images have been analyzed from that sequence,
as well as 35 images provided by the MDI aboard SOHO. In this poster,
we will discuss the analysis of the events and the implications of
our cooling model.
Title: Active Region Transient Events Observed with TRACE
Authors: Seaton, Daniel B.; Winebarger, Amy R.; DeLuca, Edward E.;
Golub, Leon; Reeves, Katharine K.; Gallagher, Peter T.
Bibcode: 2001ApJ...563L.173S
Altcode:
Nearly all active region observations made by the Transition Region
and Coronal Explorer (TRACE) contain seemingly spontaneous, short-lived
brightenings in small-scale loops. In this paper, we present an analysis
of these brightenings using high-cadence TRACE observations of Active
Region 9506 on 2001 June 21 from 15:17:00 to 15:46:00 UT. During this
time frame, several brightenings were observed over a neutral line in
a region of emerging flux that had intensity signatures in both the
171 Å (logTe~6.0) and 1600 Å (logTe~4.0-5.0)
channels. The events had a cross-sectional diameter of approximately
2" and a length of 25". We interpret these as reconnection events
associated with flux emergence, possible EUV counterparts to active
region transient brightenings.
Title: The Magnetic Structure of a Coronal X-Ray Bright Point
Authors: Brown, D. S.; Parnell, C. E.; Deluca, E. E.; Golub, L.;
McMullen, R. A.
Bibcode: 2001SoPh..201..305B
Altcode:
X-ray bright points are small dynamic loop structures that are observed
all over the solar corona. The high spatial and temporal resolution of
the TRACE instrument allows bright points to be studied in much greater
detail than previously possible. This paper focuses on a specific
bright point which occurred for about 20 hours on 13-14 June 1998 and
examines its dynamic structure in detail. This example suggests that
the mechanisms that cause bright points to form and evolve are more
complex than previously thought. In this case, reconnection probably
plays a major part during the formation and brightening of the loop
structure. However, later on the foot points rotate injecting twist
into the bright point which may cause an instability to occur with
dynamic results.
Title: A Study of Hydrogen Density in Emerging Flux Loops from
a Coordinated Transition Region and Coronal Explorer and Canary
Islands Observation Campaign
Authors: Mein, N.; Schmieder, B.; DeLuca, E. E.; Heinzel, P.; Mein,
P.; Malherbe, J. M.; Staiger, J.
Bibcode: 2001ApJ...556..438M
Altcode:
During an international ground-based campaign in the Canary Islands
coordinated with space instruments (i.e., Transition Region and Coronal
Explorer [TRACE]), we observed an active region on 1998 September
10 with high spatial and temporal resolution. New emerging flux in
the central part of the active region was observed in magnetograms
of the Swedish Vacuum Solar Telescope, La Palma. Emerging loops
(arch-filament systems [AFSs]) are well developed in Hα and Ca II
according to the observations made at the Vacuum Tower Telescope (VTT)
and THEMIS telescope in Tenerife with the Multichannel Subtractive
Double Pass (MSDP) spectrographs. The TRACE images obtained at 171
and 195 Å show low-emission regions that are easily identified as
the individual AFS. They are due to absorption by hydrogen and helium
continua in the cool filament plasma. We compare two techniques of
measuring the hydrogen density in the cool dense fibrils of AFSs. The
first method based on TRACE observations derived the neutral hydrogen
column density of the plasma absorbing coronal lines. The second one
using Hα line profiles provided by the MSDP spectrographs is based on
the cloud model. The results are consistent. We derive also electron
density values using Hα lines that are in good agreement with those
derived from the 8542 Å Ca II line observed with THEMIS (Mein et
al.). The three types of observations (TRACE, VTT, THEMIS) are well
complementary: absorption of coronal lines giving a good approximation
for the maximum value of the neutral hydrogen column density, the Hα
line giving a good determination of ne, and the 8542 Å Ca
II line a good determination of the electronic temperature.
Title: Science Objectives of the Solar B X-Ray Telescope
Authors: DeLuca, E. E.; Golub, L.; Bookbinder, J.
Bibcode: 2001AGUSM..SH31D04D
Altcode:
The X-Ray Telescope (XRT) on the Solar B Mission will set a new
standard for high resolution full disk imaging of hot solar coronal
plasma. The optimized grazing incidence optic will have more than twice
the resolution of Yohkoh's SXT, a wider temperature response and much
less scatter. We will present the expected instrument performance,
describe the science objectives, and review sample observing plans
for the XRT.
Title: Apparent Flows above an Active Region Observed with the
Transition Region and Coronal Explorer
Authors: Winebarger, Amy R.; DeLuca, Edward E.; Golub, Leon
Bibcode: 2001ApJ...553L..81W
Altcode:
The Transition Region and Coronal Explorer (TRACE) observed Active
Region 8395 on 1998 December 1 from 1:30:00 to 3:00:00 UT at high
cadence in the Fe IX/Fe X channel (logTe~6.0). Throughout
the observing time, brightness variations along a dense bundle of
coronal field lines in the southwest corner of the active region
were observed. Movies made of this region give the impression of
continuous intermittent outflow in this bundle of coronal loops; such
apparent outflow is often seen in the TRACE data. In this Letter,
we present an analysis of four separate flow events occurring in
three different loops. These events are used as tracers of the flow
in order to characterize its physical properties, such as apparent
velocity. The projected velocities of the intensity fronts of these
flows (and hence lower limits of true velocities) are between 5 and
20 km s-1. Comparisons of the observed intensities with
those predicted by a quasi-static model suggest that the events can be
explained only by a mass flow from the chromosphere into the corona. The
persistence of the flows, and their ubiquity in the TRACE observations,
indicates that hydrostatic loops models are not applicable to this
class of coronal structures.
Title: Magnetic Diffusion in Stratified Atmospheres
Authors: DeLuca, E. E.; Hurlburt, N. E.
Bibcode: 2001ApJ...548.1093D
Altcode:
The predictions from mean field electrodynamics have been questioned
because of the strong feedback of small-scale magnetic structure
on the velocity fields. In two dimensions, this nonlinear feedback
results in a lengthening of the turbulent decay time. In three
dimensions α-quenching is predicted. Previous studies assumed a
homogeneous fluid. We will present recent results from two-dimensional
compressible MHD decay simulations in a highly stratified atmosphere
that more closely resembles the solar convection zone. Our results
show that the field geometry has a strong influence on the decay rate:
vertical fields remain fairly constant for a period of time and then
rapidly decay on the turbulent timescale; horizontal fields decay at
an intermediate rate with strong fields persisting near the top and
bottom boundaries. The implication of our results for understanding
solar active region decay is discussed.
Title: High-resolution grazing incidence telescope for the Solar-B
observatory
Authors: Golub, Leon; DeLuca, Edward E.; Bookbinder, Jay A.; Cheimets,
Peter; Shibasaki, Kiyoto; Sakao, Taro; Kano, Ryouhei
Bibcode: 2000SPIE.4139..313G
Altcode:
The X-ray observations from the Yohkoh SXT provided the greatest
step forward in our understanding of the solar corona in nearly two
decades. We believe that the scientific objectives of the Solar-B
mission can best be achieved with an X-ray telescope (XRT) similar to
the SXT, but with significant improvements in spatial resolution and
in temperature response that take into account the knowledge gained
from Yohkoh. We present the scientific justification for this view,
discuss the instrumental requirements that flow from the scientific
objectives, and describe the instrumentation that will meet these
requirements. XRT is a grazing-incidence (GI) modified Wolter I X-ray
telescope, of 35 cm inner diameter and 2.7 m focal length. The 2048 X
2048 back-illuminated CCD has 13.5 (mu) pixels, corresponding to 1.0
arcsec and giving full Sun field of view. This will be the highest
resolution GI X-ray telescope ever flown for Solar coronal studies,
and it has been designed specifically to observe both the high and
low temperature coronal plasma.
Title: Determination of Flare Heating and Cooling Using the Transition
Region and Coronal Explorer
Authors: Antiochos, S. K.; DeLuca, E. E.; Golub, L.; McMullen, R. A.
Bibcode: 2000ApJ...542L.151A
Altcode:
We describe how the Transition Region and Coronal Explorer 171 Å
observations can be used to determine the properties of flare-loop
heating. The key point is that the evolution of a loop transition region
(TR) is much easier to measure quantitatively than the bulk flare plasma
because the TR emission originates from an unobscured source with simple
geometry. We derive general analytic expressions for the evolution
of a flare-loop TR that, in principle, permit a determination of the
heating function from the observations. These results are compared with
observations of the 1998 September 20 flare. We find that the observed
evolution of the flare ribbons is in good agreement with our model for
the evaporative cooling of flare loops and that the heating in these
loops is incompatible with the assumption of spatial uniformity.
Title: The Topology and Evolution of the Bastille Day Flare
Authors: Aulanier, G.; DeLuca, E. E.; Antiochos, S. K.; McMullen,
R. A.; Golub, L.
Bibcode: 2000ApJ...540.1126A
Altcode:
On 1998 July 14, a class M3 flare occurred at 12:55 UT in AR 8270
near disk center. Kitt Peak line-of-sight magnetograms show that the
flare occurred in a δ spot. Mees vector magnetograms show a strong
shear localized near a portion of the closed neutral line around the
parasitic polarity of the δ spot. Observations of the flare in 171,
195, and 1600 Å have been obtained by TRACE, with ~=40 s temporal
and 0.5" spatial resolutions. They reveal that small-scale preflare
loops above the sheared region expanded and disappeared for more than
1 hr before flare maximum. During the flare, bright loops anchored in
bright ribbons form and grow. This occurs while large-scale dimmings,
associated with large expanding loops, develop on both sides of
the active region. This suggests that the flare was eruptive and
was accompanied by a coronal mass ejection (CME). Magnetic field
extrapolations reveal the presence of a null point in the corona, with
its associated ``spine'' field line, and its ``fan'' surface surrounding
the parasitic polarity. We show that while the whole event occurs,
the intersections of the ``fan'' and the ``spine'' with the photosphere
brighten and move continuously. The interpretation of the event shows
that the magnetic evolution of the eruptive flare is strongly coupled
with its surrounding complex topology. We discuss evidence supporting a
``magnetic breakout'' process for triggering this eruptive flare. We
finally conclude that multipolar fields cannot be neglected in the
study and modeling of the origin of CMEs in the corona.
Title: Emergence of sheared magnetic flux tubes in an active region
observed with the SVST and TRACE
Authors: Deng, Y. Y.; Schmieder, B.; Engvold, O.; DeLuca, E.; Golub, L.
Bibcode: 2000SoPh..195..347D
Altcode:
The active region NOAA AR 8331 was a target of an international
ground-based observational campaign in the Canaries and coordinated
with space instruments (TRACE and Yohkoh). We focus our study on
observations obtained with the SVST at LaPalma, and with TRACE. On 10
September 1998, arch-filament systems were observed with high spatial
and temporal resolution, from the lower to the upper atmosphere of
the Sun, during five hours. Flux tubes emerged with increasing shear,
which apparently led to energy release and heating in the overlying
corona. A model for filament formation by the emergence of U-shaped
loops from the subphotosphere, as proposed by Rust and Kumar (1994),
is supported by the present observations. The coronal response to these
events is visualized by rising, medium-scale loop brightenings. The
low-lying X-ray loops show short-lived, bright knots which are thought
to result from interaction between different loop systems.
Title: A Brightening Coronal Loop Observed by TRACE. I. Morphology
and Evolution
Authors: Reale, F.; Peres, G.; Serio, S.; DeLuca, E. E.; Golub, L.
Bibcode: 2000ApJ...535..412R
Altcode:
We analyze the transient brightening of a solar coronal loop observed,
at high time cadence (30 s) and spatial resolution (0.5" pixel size),
with the Transition Region and Coronal Explorer (TRACE) in the 171 Å
band on 1998 June 26. The loop, located in AR 8253, is ~1010
cm long and inclined with respect to the vertical to the solar
surface. Its geometry and shape do not change significantly during the
brightening, which lasts for ~2 hr and is preceded by highly dynamic
events in nearby and perhaps interacting loops. The loop footpoints
brighten first; after ~10 minutes, moving brightness fronts rise
initially from the northern footpoint, and after another ~7 minutes
from the southern one, at an apparent speed ~100 km s-1, the
whole loop becoming clearly visible afterward. During the rising phase
the loop evolves coherently as a single magnetic tube. The brightness
profile is asymmetric with respect to the loop apex at all times; the
brightness contrast between the footpoints and the apex decreases with
time from a ratio of ~10 to ~3. After the loop has become all visible,
the several parallel filaments which form it follow an independent
evolution. Assuming a plasma temperature of ~1 MK, we infer a plasma
density of ~6×108 cm -3 and a pressure of ~0.2
dyn cm-2 close to the loop apex at the luminosity maximum. A
companion paper is devoted to modeling the rising phase of this event.
Title: A Brightening Coronal Loop Observed by TRACE. II. Loop Modeling
and Constraints on Heating
Authors: Reale, F.; Peres, G.; Serio, S.; Betta, R. M.; DeLuca, E. E.;
Golub, L.
Bibcode: 2000ApJ...535..423R
Altcode:
This is the second of two papers dedicated to the brightening of a
coronal loop observed by the Transition Region and Coronal Explorer
(TRACE) on 1998 June 26; it aims at hydrodynamic modeling of the
brightening. Since the loop geometry is practically unchanged during
the brightening, the evolution of the plasma confined in the loop is
described with a one-dimensional hydrodynamic time-dependent numerical
model, and from the results the emission along the loop in the TRACE
171 Å band is synthesized. The information from Paper I is used
to derive the geometry and the initial configuration of the loop as
well as for comparison with the results of the model. The modeling is
focused to determine the amount, spatial distribution, and evolution
of the heating deposited in the loop to make the modeled evolution
close to that observed with TRACE. We find that, in order to match the
observed evolution and distribution of the brightness along the loop,
the heating has to be nonsymmetrical in the loop, in particular,
deposited between the apex and one footpoint (3×109 cm
from the southern footpoint). A reasonable match with observations
is obtained by assuming that the heating is switched on abruptly and
then kept constant for the whole rising phase. An even better match
is obtained with the heating high and constant for 100 s and then
decaying exponentially with an e-folding time of 300 s. We discuss
the resulting physical scenario; a bright irregular structure close
to the loop in the TRACE images may be a tracer of the heating release.
Title: The X-ray telescope on Solar B.
Authors: Deluca, E. E.; Golub, L.; Bookbinder, J.; Cheimets, P.;
Shibasaki, K.; Sakao, T.; Kano, R.
Bibcode: 2000BAAS...32..827D
Altcode:
No abstract at ADS
Title: The X-Ray Telescope on Solar B
Authors: DeLuca, E. E.; Golub, L.; Bookbinder, J.; Cheimets, P.;
Shibasaki, K.; Sakao, T.; Kano, R.
Bibcode: 2000SPD....31Q0293D
Altcode:
The X-ray observations from the Yohkoh SXT provided the greatest
step forward in our understanding of the solar corona in nearly two
decades. We believe that the scientific objectives of the Solar-B
mission can best be achieved with an X-ray telescope (XRT) similar to
the SXT, but with significant improvements in spatial resolution and in
temperature response that take into account the knowledge gained from
Yohkoh. We present the scientific justification for this view, discuss
the instrumental requirements that flow from the scientific objectives,
and describe the instrumentation to meet these requirements. XRT is
a grazing-incidence (GI) modified Wolter I X-ray telescope, of 35cm
inner diameter and 2.7m focal length. The 2048x2048 back-illuminated
CCD has 13.5&mu pixels, corresponding to 1.0 arcsec and giving
full Sun field of view. This will be the highest resolution GI X-ray
telescope ever flown for Solar coronal studies, and it has been designed
specifically to observe both the high and low temperature coronal
plasma. A small optical telescope provide visibles light images for
coalignment with the Solar-B optical and EUV instruments. The US XRT
team is support by a NASA Contract from MSFC.
Title: The Topology and Evolution of the Bastille Day Flare Observed
by TRACE
Authors: Aulanier, G.; Antiochos, S. K.; DeLuca, E. E.; McMullen,
R. A.; Golub, L.
Bibcode: 2000SPD....31.1402A
Altcode: 2000BAAS...32..846A
On July 14, 1998, a class M3 flare occurred at 12:55 UT in AR 8270
near disc center. Kitt Peak line-of-sight magnetograms show that the
flare occurred in a δ -spot. Mees vector magnetograms show a strong
shear localized near a portion of the closed neutral line around the
parasitic polarity of the δ -spot. Observations of the flare in 171
Angstroms, 195 Angstroms and 1600 Angstroms have been obtained by TRACE,
with ~= 40 s temporal and 0.5 arcsec spatial resolutions. They reveal
that small-scale pre-flare loops above the sheared region expanded and
disappeared for more than one hour before flare maximum. During the
flare, bright loops anchored in bright ribbons form and grow. This
occurs while large-scale dimmings, associated with large expanding
loops, develop on both sides of the AR. This suggests that the
flare was eruptive, and was accompanied by a coronal mass ejection
(CME). Magnetic field extrapolations reveal the presence of a null
point in the corona, with its associated ``spine'' field line, and
its ``fan'' surface surrounding the parasitic polarity. We show that
while the whole event occurs, the intersections of the ``fan'' and the
``spine'' with the photosphere brighten and move continuously. The
interpretation of the event shows that the magnetic evolution of
the eruptive flare is strongly coupled with its surrounding complex
topology. We discuss evidence supporting a ``magnetic breakout''
process for triggering this eruptive flare. We finally conclude that
multipolar fields cannot be neglected in the study and modeling of
the origin of CMEs in the corona. This work is supported, at SAO by
a NASA contract to Lockheed-Martin, and at NRL by NASA and ONR.
Title: Long-lived Coronal Loop Profiles from TRACE
Authors: Lenz, Dawn D.; DeLuca, Edward E.; Golub, Leon; Rosner, Robert;
Bookbinder, Jay A.; Litwin, Christof; Reale, Fabio; Peres, Giovanni
Bibcode: 1999SoPh..190..131L
Altcode:
An initial study of long-lived loops observed with TRACE (Lenz et al.,
1999) shows that they have no significant temperature stratification
and that they are denser than the classic loop model predicts. Models
that agree better with the observations include a loop consisting of a
bundle of filaments at different temperatures and a loop with momentum
input by MHD waves. Some implications for coronal heating models and
mechanisms are discussed.
Title: A Study of Hydrogen Density in Emerging Flux Loops from a
Coordinated TRACE and Canary Islands Observation Campaign
Authors: Schmieder, B.; Deluca, E.; Mein, N.; Mein, P.; Malherbe,
J. M.; Wilken, V.; Staiger, J.; Engvold, O.; Hanssen, I.
Bibcode: 1999ESASP.448..653S
Altcode: 1999mfsp.conf..653S; 1999ESPM....9..653S
No abstract at ADS
Title: Fine-Structures and Dynamics of a Filament in EUV lines:
SOHO/CDS and SUMER, TRACE
Authors: Schmieder, B.; Engvold, O.; Wiik, J. E.; Deluca, E.
Bibcode: 1999ESASP.446..599S
Altcode: 1999soho....8..599S
No abstract at ADS
Title: An Eruptive Flare Observed by TRACE as a Test for the Magnetic
Authors: Aulaneir, G.; Deluca, E. E.; Golub, L.; Artzner, Guy; Sabine
Coquillart; Hochedez, Jean-Francois; Delaboudinier, Jean-Pierre
Bibcode: 1999ESASP.446..131A
Altcode: 1999soho....8..131A
No abstract at ADS
Title: An Eruptive Flare Observed by TRACE as a Test for the Magnetic
Authors: Aulaneir, G.; Deluca, E. E.; Golub, L.; McMullen, R. A.;
Karpen, J. T.; Antiochos, S. K.
Bibcode: 1999ESASP.446..135A
Altcode: 1999soho....8..135A
No abstract at ADS
Title: Observed Magnetic Structure of X-Ray Bright Points from TRACE
and MDI
Authors: Brown, D. S.; Parnell, C.; Deluca, E.; McMullen, R.; Golub, L.
Bibcode: 1999ASPC..184...81B
Altcode:
From 13th-17th June 1998, TRACE and MDI simultaneously observed the
same quiet region of the Sun. From these observations the fascinating
and complex structure of x-ray bright points, intense small scale
brightenings that occur throughout the solar corona, can be seen in
great detail. For the first time, it has been possible to study bright
points for their entire lifetime with a cadence of 2 minutes and a
temporal resolution of 0.5 arcsecs. One particular bright point which
lasted two days exhibited dynamic structural behaviour which became
increasingly complex and lead to its sudden eruptive demise. With the
use of MDI magnetograms, it is possible to extrapolate the magnetic
structure using an analytical constant α force-free approximation. This
has been used to help us to explain the topology and behaviour of the
bright point. By comparing two of TRACE's Fe lines (FeIX and FeXII) the
spatial and temporal temperature and density structure of the bright
point has been investigated. This analysis indicates that this bright
point is made up of a complex system of dense loops. By understanding
the magnetic, temperature and density structure of the bright point,
it is hoped that the mechanism by which it is heated can be gained.
Title: TRACE observation of damped coronal loop oscillations:
Implications for coronal heating
Authors: Nakariakov, V. M.; Ofman, L.; Deluca, E. E.; Roberts, B.;
Davila, J. M.
Bibcode: 1999Sci...285..862N
Altcode:
The imaging telescope on board the Transition Region and Coronal
Explorer (TRACE) spacecraft observed the decaying transversal
oscillations of a long [(130 ± 6) × 106 meters], thin
[diameter (2.0 ± 0.36) × 106 meters], bright coronal
loop in the 171 angstrom FeIX emission line. The oscillations were
excited by a solar flare in the adjacent active region. The decay
time of the oscillations is 14.5 ± 2.7 minutes for an oscillation
with a frequency 3.90 ± 0.13 millihertz. The coronal dissipation
coefficient is estimated to be eight to nine orders of magnitude
larger than the theoretically predicted classical value. The larger
dissipation coefficient may solve existing difficulties with wave
heating and reconnection theories.
Title: A new view of the solar outer atmosphere by the Transition
Region and Coronal Explorer
Authors: Schrijver, C. J.; Title, A. M.; Berger, T. E.; Fletcher, L.;
Hurlburt, N. E.; Nightingale, R. W.; Shine, R. A.; Tarbell, T. D.;
Wolfson, J.; Golub, L.; Bookbinder, J. A.; DeLuca, E. E.; McMullen,
R. A.; Warren, H. P.; Kankelborg, C. C.; Handy, B. N.; De Pontieu, B.
Bibcode: 1999SoPh..187..261S
Altcode:
The Transition Region and Coronal Explorer (TRACE) - described in the
companion paper by Handy et al. (1999) - provides an unprecedented
view of the solar outer atmosphere. In this overview, we discuss the
initial impressions gained from, and interpretations of, the first
million images taken with TRACE. We address, among other topics,
the fine structure of the corona, the larger-scale thermal trends,
the evolution of the corona over quiet and active regions, the high
incidence of chromospheric material dynamically embedded in the coronal
environment, the dynamics and structure of the conductively dominated
transition region between chromosphere and corona, loop oscillations
and flows, and sunspot coronal loops. With TRACE we observe a corona
that is extremely dynamic and full of flows and wave phenomena, in
which loops evolve rapidly in temperature, with associated changes in
density. This dynamic nature points to a high degree of spatio-temporal
variability even under conditions that traditionally have been referred
to as quiescent. This variability requires that coronal heating can
turn on and off on a time scale of minutes or less along field-line
bundles with cross sections at or below the instrumental resolution
of 700 km. Loops seen at 171 Å (∼1 MK) appear to meander through
the coronal volume, but it is unclear whether this is caused by the
evolution of the field or by the weaving of the heating through the
coronal volume, shifting around for periods of up to a few tens of
minutes and lighting up subsequent field lines. We discuss evidence
that the heating occurs predominantly within the first 10 to 20 Mm
from the loop footpoints. This causes the inner parts of active-region
coronae to have a higher average temperature than the outer domains.
Title: The transition region and coronal explorer
Authors: Handy, B. N.; Acton, L. W.; Kankelborg, C. C.; Wolfson, C. J.;
Akin, D. J.; Bruner, M. E.; Caravalho, R.; Catura, R. C.; Chevalier,
R.; Duncan, D. W.; Edwards, C. G.; Feinstein, C. N.; Freeland, S. L.;
Friedlaender, F. M.; Hoffmann, C. H.; Hurlburt, N. E.; Jurcevich,
B. K.; Katz, N. L.; Kelly, G. A.; Lemen, J. R.; Levay, M.; Lindgren,
R. W.; Mathur, D. P.; Meyer, S. B.; Morrison, S. J.; Morrison, M. D.;
Nightingale, R. W.; Pope, T. P.; Rehse, R. A.; Schrijver, C. J.;
Shine, R. A.; Shing, L.; Strong, K. T.; Tarbell, T. D.; Title, A. M.;
Torgerson, D. D.; Golub, L.; Bookbinder, J. A.; Caldwell, D.; Cheimets,
P. N.; Davis, W. N.; Deluca, E. E.; McMullen, R. A.; Warren, H. P.;
Amato, D.; Fisher, R.; Maldonado, H.; Parkinson, C.
Bibcode: 1999SoPh..187..229H
Altcode:
The Transition Region and Coronal Explorer (TRACE) satellite, launched
2 April 1998, is a NASA Small Explorer (SMEX) that images the solar
photosphere, transition region and corona with unprecedented spatial
resolution and temporal continuity. To provide continuous coverage
of solar phenomena, TRACE is located in a sun-synchronous polar
orbit. The ∼700 Mbytes of data which are collected daily are made
available for unrestricted use within a few days of observation. The
instrument features a 30-cm Cassegrain telescope with a field of view
of 8.5×.5 arc min and a spatial resolution of 1 arc sec (0.5 arc sec
pixels). TRACE contains multilayer optics and a lumogen-coated CCD
detector to record three EUV wavelengths and several UV wavelengths. It
observes plasmas at selected temperatures from 6000 K to 10 MK with
a typical temporal resolution of less than 1 min.
Title: Temperature and Emission-Measure Profiles along Long-lived
Solar Coronal Loops Observed with the Transition Region and Coronal
Explorer
Authors: Lenz, Dawn D.; DeLuca, Edward E.; Golub, Leon; Rosner,
Robert; Bookbinder, Jay A.
Bibcode: 1999ApJ...517L.155L
Altcode: 1999astro.ph..3491L
We report an initial study of temperature and emission-measure
distributions along four steady loops observed with the Transition
Region and Coronal Explorer at the limb of the Sun. The temperature
diagnostic is the filter ratio of the extreme-ultraviolet 171 and 195
Å passbands. The emission-measure diagnostic is the count rate in the
171 Å passband. We find essentially no temperature variation along
the loops. We compare the observed loop structure with theoretical
isothermal and nonisothermal static loop structure.
Title: A new view of the solar corona from the transition region
and coronal explorer (TRACE)
Authors: Golub, L.; Bookbinder, J.; Deluca, E.; Karovska, M.; Warren,
H.; Schrijver, C. J.; Shine, R.; Tarbell, T.; Title, A.; Wolfson,
J.; Handy, B.; Kankelborg, C.
Bibcode: 1999PhPl....6.2205G
Altcode:
The TRACE Observatory is the first solar-observing satellite in the
National Aeronautics and Space Administration's (NASA) Small Explorer
series. Launched April 2, 1998, it is providing views of the solar
transition region and low corona with unprecedented spatial and
temporal resolution. The corona is now seen to be highly filamented,
and filled with flows and other dynamic processes. Structure is seen
down to the resolution limit of the instrument, while variability and
motions are observed at all spatial locations in the solar atmosphere,
and on very short time scales. Flares and shock waves are observed,
and the formation of long-lived coronal structures, with consequent
implications for coronal heating models, has been seen. This overview
describes the instrument and presents some preliminary results from
the first six months of operation.
Title: Determination of the Reynolds number from TRACE Observation
of Damped Coronal Loop Oscillations Induced by a Flare
Authors: Ofman, L.; Nakariakov, V. M.; Deluca, E.; Roberts, B.;
Davila, J. M.
Bibcode: 1999AAS...194.7909O
Altcode: 1999BAAS...31..964O
The Transition Region and Coronal Expolorer (TRACE) observes the solar
corona with unprecedented spatial and temporal resolution. We analyzed
active region loop observation in the 171 Angstroms Fe IX emission line,
and report the direct observations of damped transverse oscillations
of a long (130+/-6 Mm) thin (diameter 2+/-0.36 Mm) bright active region
loop. The oscillations were detected following a flare in the adjacent
active region. We determined the oscillation frequency and the decay
time by the least-square fit of an exponentially decaying sinusoidal
function. Using the dispersion relation for the transverse oscillations,
and the observed loop geometry we estimated the Alfven crossing time
in the loop. The Alfven time can be used to determine the magnetic
field strength in the loop if the density is known. All parts of the
loop were observed to oscillate transversly in-phase, implying that the
ocillation is a global mode of the loop. Using dissipative MHD model for
resonant absorption of global mode oscillations for the coronal loop
we determined the Reynolds number that produces the observed damping
rate of the observed global mode. The value of the Reynolds number is
in the 10(5-10^6) range, which is eight to nine orders of magnitude
smaller than the classical coronal value. We discuss the important
implication of the small Reynolds number on coronal heating theories.
Title: Nonlinear Compressible Dynamos
Authors: Deluca, E. E.; Hurlburt, N. E.
Bibcode: 1999AAS...194.5616D
Altcode: 1999BAAS...31..914D
The predictions of Mean Field Electrodynamics have been questioned
because of the strong feedback of small scale magnetic structure
on the velocity fields. In 2-D, this nonlinear feedback results in
a lengthening of the turbulent decay time. In 3-D alpha-quenching
is predicted. Previous studies assumed a homogeneous fluid. Here
we present result of numerical solutions of fully compressible,
nonlinear dynamos in two and three dimensions. In two dimensions,
we consider an adiabatically stratified layer which experiences a
constant shear. A mean-field alpha effect is introduced which is uniform
over the layer. This system admits dynamo solutions of both the alpha
-omega and alpha (2) varieties. This system also experiences a random
thermal forcing which generates an additional turbulent diffusion. We
seek to understand both the nonlinear actions of this system and the
impact of the turbulent motions upon it. The magnetic flux in the
convecting region above has a strong influence on the evolution of
the dynamo. In three dimensions we model the generation of magnetic
field in an adiabatic, stratified layer with random thermal forcing
and an imposed velocity shear across the layer. Rather than introduce
an artificial alpha effect, we seek a fully self consistent periodic
dynamo. We therefore introduce a uniform rotation to the system which,
in conjunction with the random forcing produces a mean helicity to
the flows. We present the results of these calculations and their
implications for the solar cycle. This work is supported by NASA grant:
NAGW-5154
Title: TRACE and SVST Observations of an Active-Region Filament
Authors: van Ballegooijen, A. A.; Deluca, E. E.
Bibcode: 1999AAS...194.7806V
Altcode: 1999BAAS...31..962V
In June 1998 the Transition Region and Coronal Explorer (TRACE) observed
filaments and prominences in coordination with various ground-based
solar observatories, including the Swedish Vacuum Solar Telescope (SVST)
on La Palma. Here we present results for an active-region filament
observed on June 21-22. This horse-shoe shaped filament had a "barb"
that reached down from the filament spine to the chomosphere below. We
use high-resolution images obtained at the SVST on June 21 from 18:03
to 19:04 UT to study the fine structure and dynamics of plasmas in the
barb and other parts of the filament. The data consist of narrowband
Hα images taken with the Lockheed Tunable Filtergraph operating at a
cadence of 20 s. We present Doppler maps derived from these images. The
filament erupted six hours after the SVST observations. The eruption
was observed with TRACE, which obtained images in Fe IX/X 171, Fe XII
195, Fe XV 284 and H I Lyalpha . At the start of the event, a thin
bright loop appears high above the filament at the location of the
barb. We interpret this feature as the outline of a magnetic "bubble"
which forms as a result of kink instability in the magnetic field that
supports the filament. The bright loop appears to be due to particle
acceleration and impulsive heating along certain field lines on the
periphery of this magnetic structure. A few minutes later, the dark
filament threads turn into emission and move outward, exhibiting a
helical structure. We discuss the magnetic structure of the barb and
its possible role in the filament eruption.
Title: The Transition Region and Coronal Explorer
Authors: Handy, B. N.; Deluca, E. E.; McMullen, R. A.; Schrijver,
C. J.; Tarbell, T. D.; Title, A. M.; Wolfson, C. J.
Bibcode: 1998AAS...193.1207H
Altcode: 1998BAAS...30R1269H
The Transition Region and Coronal Explorer (TRACE), launched 1 April
1998, will have at the time of this meeting been in orbit for just over
8 months. In that time, the instrument will have taken over 500,000
exposures of the sun in ultraviolet and extreme ultraviolet wavelengths,
will have completed three-forths of the nominal mission and will be
approaching the end of the first eclipse season. The TRACE telescope
is unique in its ability to observe in UV and EUV wavelengths at high
cadence with unprecedented resolution. We present a review of the TRACE
instrument and show current observations and results. We discuss the
performance of the instrument in terms of observational capabilities,
sensitivity, calibration, effects of aging on the instrument, CCD
effects, and contamination effects.
Title: HIREX: results of the mission concept study
Authors: Bookbinder, Jay A.; Cheimets, Peter; Davis, William R.;
Caldwell, David; Golub, Leon; Deluca, Edward
Bibcode: 1998SPIE.3442...22B
Altcode:
HIREX is a suite of three complementary solar-pointed instruments
that is being proposed to NASA under the NASA MIDEX announcement
of opportunity. The main instrument is a 0.6m clear aperture, 240m
effective focal length normal incidence XUV telescope operated at 171
angstrom, with a spatial resolution of 0.01 inch. This main telescope
is complemented by two other instruments: 1) a 0.3 m context telescope
that images in a wavelength range that covers the UV and XUV spectral
regime, based on the TRACE design. This context telescope places the
high magnification, limited field of view images created by the high
resolution telescope in both spatial and temperature context. 2)
A spectrometer covering the spectral range from 170-220 angstrom,
based on the SERTS design.
Title: Large-area thin aluminum filter design, handling, and testing
Authors: Cheimets, Peter; Bookbinder, Jay A.; Deluca, Edward; Caldwell,
David; Davis, William R.; Golub, Leon
Bibcode: 1998SPIE.3445...96C
Altcode:
The process of observing the Sun in the x-ray and extreme UV (XUV),
as we are now doing with the TRACE telescope, requires blocking
the tremendous amount of visible and RI light that dominates the
flux from the sun. If it is not blocked, the energy will swamp the
desired spectrum and cause thermal problems inside the telescope. The
most effective approach removing the energy is by filtering the
incoming light. One of the best materials for eliminating the
undesirable wavelengths is aluminum, which is semi- transparent
to x-ray and XUV, but blocks most light with wavelength redward of
850 angstrom. Unfortunately the aluminum must be extremely must be
extremely thin, < 1600 angstrom thick, to provide the necessary
XUV transparency. To overcome the structural problem of supporting
large areas of extremely thin aluminum, the aluminum film is bonded
on a nickel mesh.
Title: Magnetohydrodynamic Turbulence of Coronal Active Regions and
the Distribution of Nanoflares
Authors: Dmitruk, Pablo; Gómez, Daniel O.; DeLuca, Edward E.
Bibcode: 1998ApJ...505..974D
Altcode:
We present results from numerical simulations of an externally driven
two-dimensional magnetohydrodynamic system over extended periods
of time, used to model the dynamics of a transverse section of a
solar coronal loop. A stationary forcing was imposed to model the
photospheric motions at the loop footpoints. After several photospheric
turnover times, a turbulent stationary regime is reached that has an
energy dissipation rate consistent with the heating requirements of
coronal loops. The turbulent velocities obtained in our simulations
are consistent with those derived from the nonthermal broadening of
coronal spectral lines. We also show the development of small scales in
the spatial distribution of electric currents, which are responsible
for most of the energy dissipation. The energy dissipation rate as
a function of time displays an intermittent behavior, in the form
of impulsive events, that is a direct consequence of the strong
nonlinearity of the system. We associate these impulsive events of
magnetic energy dissipation with the so-called nanoflares. A statistical
analysis of these events yields a power-law distribution as a function
of their energies with a negative slope of 1.5, consistent with
those obtained for flare energy distributions reported from X-ray
observations. A simple model of dissipative structures, based on
Kraichnan's theory for MHD turbulence, is also presented.
Title: First Results from the TRACE Mission
Authors: Title, A.; Tarbell, T.; Schrijver, C.; Wolfson, J.; Shine,
R.; Hurlburt, N.; Golub, L.; Deluca, E.; Bookbinder, J.; Handy, B.;
Acton, L.; Harrison, R.; Delaboudinere, J. -P.
Bibcode: 1998AAS...192.1507T
Altcode: 1998BAAS...30..841T
The TRACE spacecraft was launched on 1 April and all systems are
functioning as designed. The initial outgassing period will conclude
on 20 April and the science program will then begin. TRACE is a UV-EUV
imager with one arc second spatial resolution and is capable of taking
images with a cadence as high as two seconds. We will present images
and image sequences. We hope to present initial comparisons of magnetic
evolution and transition region and coronal brightenings.
Title: Chinks in Solar Dynamo Theory: Turbulent Diffusion, Dynamo
Waves and Magnetic Helicity
Authors: Deluca, E. E.; Hurlburt, N.
Bibcode: 1998nasa.reptV....D
Altcode:
In this first year of our investigation we explored the role of
compressibility and stratification in the dissipation of magnetic
fields. The predictions of Mean Field Electrodynamics have been
questioned because of the strong feedback of small scale magnetic
structure on the velocity fields. In 2-D, this nonlinear feedback
results in a lengthening of the turbulent decay time. In 3-D
alpha-quenching is predicted. Previous studies assumed a homogeneous
fluid. This first year we present recent results from 2-D compressible
MHD decay simulations in a highly stratified atmosphere that more
closely resembles to solar convection zone. We have applied for NCCS
T3E time to assist in the performance of our 3-D calculations.
Title: Magnetic Diffusion in Stratified Atmospheres
Authors: Deluca, Edward E.; Hurlburt, Neal
Bibcode: 1997SPD....28.0251D
Altcode: 1997BAAS...29..902D
The predictions from of Mean Field Electrodynamics have been questioned
because of the strong feedback of small scale magnetic structures
on the velocity fields. In 2-D, this nonlinear feedback results in
a lengthening of the turbulent decay time. In 3-D alpha -quenching
is predicted. Previous studies assumed a homogeneous fluid. We will
present recent results from 2-D compressible MHD decay simulations in
a highly stratified atmosphere that more closely resembles to solar
convection zone.
Title: Detecting Siphon Flows in Coronal Loops
Authors: McMullen, Rebecca A.; Deluca, Edward E.; Golub, Leon
Bibcode: 1997SPD....28.0148M
Altcode: 1997BAAS...29..888M
While siphon flows are thought to be common in coronal loops,
detection in coronal emission has remained elusive. The Tuneable
X-Ray Imager (TXI) sounding rocket will produce images of the corona
in 4 Angstroms \ passbands around prominent emission lines between
170-200 Angstroms. This new instrument can also produce velocity
maps from difference images taken on either side of an emission
line. We present a study of the response of the TXI to siphon flows
in coronal loop models. The models show that loops with flows are
significantly fainter than the equivalent static loops. In addition,
contamination from nearby lines tends to mask the Doppler shift, even
with an instrument of excellent imaging capacity. We will outline more
detailed analysis methods that may reveal the siphon flows more clearly.
Title: The TRACE Mission
Authors: Wolfson, J.; Bruner, M.; Jurcevich, B.; Lemen, J.; Schrijver,
K.; Shine, R.; Strong, K.; Tarbell, T.; Title, A.; Golub, L.;
Bookbinder, J.; Deluca, E.; Acton, L.; Handy, B.; Kankelborg, C.;
Fisher, R.
Bibcode: 1997SPD....28.0143W
Altcode: 1997BAAS...29..887W
The TRACE (Transition Region and Coronal Explorer) mission will explore
the connections between fine-scale magnetic fields and plasma structures
in the coronal, transition zone and temperature minimum regions of the
sun. TRACE will collect images of solar plasmas at temperatures from
10(4) to 10(7) K, with one arc second spatial resolution and excellent
temporal resolution and continuity. With a scheduled launch date of 15
December 1997, the mission will emphasize collaborative observations
with SoHO, enabling simultaneous observations of high-resolution images,
spectra, and magnetograms. The 30 cm aperture TRACE telescope uses four
normal-incidence coatings for the EUV and UV on quadrants of the primary
and secondary mirrors. Interference filters further isolate 5 different
UV bands. The images are co-aligned and internally stabilized against
spacecraft jitter. A 1024 x 1024 lumigen-coated CCD detector collects
images over an 8.5 x 8.5 arc minute field-of-view. LMATC, SAO, and GSFC
built the TRACE instrument, which was integrated with the GSFC-produced
SMEX spacecraft on 28 February (just over two years from the start
of its development). It will be put into a Sun-synchronous orbit and
operated in coordination with the SoHO Experiment Operations Facility at
GSFC. We are committed to maintaining a publicly accessible data base
for TRACE data. Browsing and data set requesting capabilities will be
provided at Web site www.space.lockheed.com/TRACE/TRACElinks.html. This
site already contains a large volume of information on the mission
including preliminary scientific observing programs and directions
as to how to participate in the mission now and in the future. This
project is supported by NASA contract NAS5-38099.
Title: The Emergence of Magnetic Flux Loops in Sunlike Stars
Authors: DeLuca, Edward E.; Fan, Yuhong; Saar, Steven H.
Bibcode: 1997ApJ...481..369D
Altcode:
We explore the latitude of emergence of flux tubes at the surface
of G stars as a function of the rotation rate, magnetic flux,
and injection latitude at the bottom of the convective zone. Our
analysis is based on a thin flux tube evolution code that has been
developed to study the emergence of magnetic flux in the Sun and is
well calibrated by detailed comparisons with solar observations. We
study solar models with rotation rates between 1/3 and 10 times solar,
injection latitudes φI between 1° and 40°, and tubes
with a range of field strengths, B0, and fluxes. For
our range of input parameters, we find that the mean latitude of
emergence, <φE>, increases and its range decreases
with higher rotation rates, that φE <= 45° for stars
with rotational periods >=27 days, that φE increases
with B0 in rapid rotators, while the reverse is true for
slow rotators, that the dependence of φE on B0
decreases with increasing φI, that tubes with higher flux
emerge at larger φE, and that the footpoint separation
depends linearly on B0. We compare our results to other
calculations and with observations of magnetic features on stars and
suggest future observations and extensions of this research. Our results
suggest that for near-polar starspots to occur, either active stars
must have a larger range of φI than inferred for the Sun,
or differential rotation and meridional flows are more important for
magnetic flux redistribution in these stars. Our models also imply
that flux appearing near the equator of active stars may be generated
by a distributed, rather than a boundary layer, dynamo.
Title: Possible Detection of a Residual Non-Cyclic Distributed Dynamo
in ``Maunder Minimum'' Stars
Authors: Saar, S. H.; Deluca, E. E.; Baliunas, S. L.; Donahue, R. A.
Bibcode: 1996AAS...189.8104S
Altcode: 1996BAAS...28.1382S
We have analyzed HST and IUE ultraviolet spectra of five dwarfs which
have extremely low, non-variable levels of Ca II HK emission. These
stars appear to be in the stellar analog of the solar ``Maunder
minimum'' - a period when the normal cyclic magnetic dynamo went
into temporary quiescence. The stars all have very low levels of
chromospheric and transition region (TR) emission. The ratio of TR (Si
IV and C IV) to chromospheric emission (C II) is smaller than expected
from published estimates of the ``basal'' emission, and increases with
decreasing T_eff. This is in contrast to the lack of such a trend in
dwarfs with variable Ca II HK (``normal'' operating magnetic dynamos)
and the reverse of the trend expected if the emission was acoustic in
origin. The existence of significant TR emission in ``Maunder minimum''
stars suggests that they are still generating magnetic flux, but
it is apparently in some form which enhances chromospheric emission
relative to the TR. A possible explanation for the observations is
that a residual ``Maunder minimum'' magnetic flux is a generated
by a non-cyclic distributed-type dynamo (a less efficient mechanism
which operates throughout the convective zone, and thus grows with
increased convective zone depth). If this scenario is correct, our
data are the first observational evidence of such a dynamo operating
in a star which is not fully convective.
Title: Modeling magnetic flux emergence in HD 106225.
Authors: Wills, M. J.; Deluca, E. E.; Guenther, D. B.
Bibcode: 1996BAAS...28..943W
Altcode:
No abstract at ADS
Title: Modeling Magnetic Flux Emergence in HD 106225
Authors: Wills, M. J.; Deluca, E. E.; Guenther, D. B.
Bibcode: 1996AAS...188.7109W
Altcode: 1996BAAS...28R.943W
Using a ``thin flux tube'' approximation proposed by Spruit (1981),
and working with a numerical simulation previously used to model
solar magnetic flux dynamics, we attempt to create magnetic flux tube
emergence in HD 106225, a rapidly rotating subgiant star, which has been
observed to have both x-ray emission and starspots. Initial attempts,
placing the stellar dynamo at the base of the convection zone, as has
been done in solar modeling, were unsuccessful. Fisher, McClymont, &
Chou (1991) show that, if the pressure scale height at the base of the
convection zone is a significant fraction of the radius at that point
(Lambda /R > 0.3), the magnetic tension force increases faster than
the buoyancy as the tube is stretched, and no rise occurs from a tube
anchored at the base of the convection zone. However, Spruit &
van Ballegooijen (1982a, b) prove that, for stars with sufficiently
deep convection zones, it is possible to create a buoyantly stable flux
tube in the convection zone itself. The stability of a given mode again
depends on the value of Lambda /R at a given radius. If Lambda /R >
0.3, a flux tube is able to maintain null buoyancy in the convection
zone proper. Using Spruit & van Ballegooijen's solutions, we
are able to run numerical simulations that model stable flux tubes
in the convection zone. We have also been able to create the rise
of a magnetic flux perturbation by placing the base of the ring at
a stable convective radius with the perturbation extending to a more
buoyant radius. Initial attempts have been based on a simplified model,
placing a flux tube at zero latitude with no rotation. We also attempt
simulations which allow for flux rise at non-zero latitudes and include
Coriolis force. Using these results, we examine the implications that
such a magnetic field pattern has for the stellar dynamo.
Title: Observations of a Quiescent Prominence Straddling the Solar
Limb during the Total Eclipse of 11 July 1991
Authors: Gaizauskas, V.; Deluca, E.; Golub, L.; Jones, H. P.;
November, L.
Bibcode: 1996mpsa.conf..491G
Altcode: 1996IAUCo.153..491G
No abstract at ADS
Title: Observations and Interpretation of Soft X-Ray Limb Absorption
Seen by the Normal Incidence X-Ray Telescope
Authors: Daw, A.; Deluca, E. E.; Golub, L.
Bibcode: 1995ApJ...453..929D
Altcode:
The Normal Incidence X-Ray Telescope (NIXT) obtained a unique set of
high-resolution full-disk solar images which were exposed simultaneously
by X-rays in a passband at 63.5 Å and by visible light. The perfect
alignment of a photospheric visible-light image with a coronal
X-ray image enables us to present observations of X-ray intensity
as a function of an accurately determined height above the visible
limb. The height at which the observed X-ray intensity peaks varies
from 4000 km in active regions to 9000 km in quiet regions of the
Sun. The interpretation of the observations stems from the previously
established fact that, for the coronal loops, emission in the NIXT
bandpass peaks sharply just above the footpoints. Because there is
not a sharp peak in the observed X-ray intensity as a function of
off-limb height, we conclude that the loop footpoints, when viewed at
the limb, are obscured by absorption in chromospheric material along
the line of sight. We calculate the X-ray intensity as a function of
height predicted by a number of different idealizations of the solar
atmosphere, and we compare these calculations with the observed X-ray
intensity as a function of height. The calculations use existing coronal
and chromospheric models. In order for the calculations to reproduce
the observed off-limb X-ray intensities, we are forced to assume an
atmosphere in which the footpoints of coronal loops are interspersed
along the line of sight with cooler chromospheric material extending to
heights well above the loop footpoints. We argue that the absorption
coefficient for NIXT X-rays by chromospheric material is roughly
proportional to the neutral hydrogen density, and we estimate an
average neutral hydrogen density and scale height implied by the data.
Title: Nonlinear Energy Transfer in Solar Magnetic Loops
Authors: Gomez, Daniel O.; Deluca, Edward E.; McClymont, Alexander N.
Bibcode: 1995ApJ...448..954G
Altcode:
Active region coronal loops are widely believed to be heated by ohmic
dissipation of field-aligned electric currents. These currents are
driven by turbulent photospheric motions which twist and shear the
magnetic footpoints of loops. Fine-scale structure in the corona is
required in order to dissipate the currents rapidly enough to account
for coronal heating. A long-standing controversy surrounds the question:
is the fine-scale filamentation the result of magnetohydrodynamic
(MHD) instabilities, or of dynamical nonequilibrium, or is it merely
the direct product of the turbulent footpoint motions themselves? We
present a simple model for the evolution of the coronal magnetic field,
with no fine-scale structure in the imposed footpoint motions. The
model consists of a three-mode truncation of the "reduced" MHD
equations. One mode is driven by a stationary velocity field at the
footpoints; the other two modes, of different spatial frequencies, are
amplified through interaction with the driven mode. After approximately
one photospheric turnover time, the coronal field loses equilibrium,
and evolves rapidly to a new configuration, transferring energy to the
two non-driven modes. The timescale of rapid nonequilibrium evolution
is (tAtp)½, where tA
is the Alfvén transit time along the loop and tp is
the photospheric turnover time. Regarding this simple model as a
building block of a much more complex process, we see that dynamical
nonequilibrium should be able to produce a cascade of free energy
to fine spatial scales where it can be dissipated rapidly enough to
account for coronal heating, as envisioned by Parker.
Title: NIXT X-ray Bright Point Survey: Building a Better Bright Point
Authors: Wills, M. J.; Hartl, M. D.; Deluca, E. E.; Golub, L.
Bibcode: 1995SPD....26..707W
Altcode: 1995BAAS...27..966W
No abstract at ADS
Title: Recovering the fine structures in solar images
Authors: Karovska, M.; Habbal, S. R.; Golub, L.; DeLuca, E.; Hudson, H.
Bibcode: 1994ESASP.373..183K
Altcode: 1994soho....3..183K
No abstract at ADS
Title: Simultaneous High Resolution Coronal and Photospheric
Observations From NIXT and BBSO
Authors: Winebarger, A.; Deluca, E. E.; Golub, L.
Bibcode: 1994AAS...185.8605W
Altcode: 1994BAAS...26.1464W
High resolution coronal images from the 11 September 1989 flight of the
NIXT (Normal Incidence X-ray Telescope) and a series of simultaneous
high resolution Big Bear Magnetograms are discussed as part of an on
going investigation of X-ray bright points. The NIXT and BBSO images
are aligned and the evolution of the magnetic fields associated with
coronal features were monitored over the experimental time frame. An
analysis of the relationship between the X-ray bright points and
the time resolved BBSO magnetograms is presented. Bright points are
associated with both converging and diverging magnetic bi-poles.
Title: Models of Rising Active Region Flux Tubes
Authors: Fisher, George H.; Fan, Yuhong; Deluca, Edward E.; McClymont,
Alexander N.
Bibcode: 1994ASPC...68..109F
Altcode: 1994sare.conf..109F
No abstract at ADS
Title: The SWATH Satellite Program
Authors: Bookbinder, J.; Golub, L.; Deluca, E.; Smartt, R.
Bibcode: 1993AAS...183.0810B
Altcode: 1993BAAS...25R1302B
No abstract at ADS
Title: The Dynamics of Magnetic Flux Rings
Authors: Deluca, E. E.; Fisher, G. H.; Patten, B. M.
Bibcode: 1993ApJ...411..383D
Altcode:
The evolution of magnetic fields in the presence of turbulent convection
is examined using results of numerical simulations of closed magnetic
flux tubes embedded in a steady 'ABC' flow field, which approximate
some of the important characteristics of a turbulent convecting flow
field. Three different evolutionary scenarios were found: expansion to
a steady deformed ring; collapse to a compact fat flux ring, separated
from the expansion type of behavior by a critical length scale; and,
occasionally, evolution toward an advecting, oscillatory state. The
work suggests that small-scale flows will not have a strong effect on
large-scale, strong fields.
Title: The Origin of Morphological Asymmetries in Bipolar Active
Regions
Authors: Fan, Y.; Fisher, G. H.; Deluca, E. E.
Bibcode: 1993ApJ...405..390F
Altcode:
A series of 3D numerical simulations was carried out to examine the
dynamical evolution of emerging flux loops in the solar convective
envelope. The innermost portions of the loops are anchored beneath the
base of the convective zone by the subadiabatic temperature gradient
of the underlying overshoot region. It is found that, as the emerging
loops approach the photosphere, the magnetic field strength of the
leading side of each rising loop is about twice as large as that of the
following side at the same depth. The evacuation of plasma out of the
leading side of the rising loop results in an enhanced magnetic field
strength there compared with the following side. It is argued that this
result provides a natural explanation for the fact that the preceding
(leading) polarity tends to have a less organized and more fragmented
appearance, and that the preceding spots tend to be larger in area and
fewer in number, and have a longer lifetime than the following spots.
Title: The Evolution of Anchored Magnetic Flux Loops in the Convective
Envelope of the Sun
Authors: Fan, Y.; Fisher, G. H.; Deluca, E. E.
Bibcode: 1993ASPC...42...89F
Altcode: 1993gong.conf...89F
No abstract at ADS
Title: Fibril Dynamics and Fibril Dynamos
Authors: Deluca, E. E.; Fisher, G. H.
Bibcode: 1992AAS...180.0501D
Altcode: 1992BAAS...24..733D
The dynamics of fibril magnetic fields in a three dimensional
chaotic flow shows that two possible final states are realizable:
collapse to a singular ring, and expansion to an asymoptotic state
with magnetic tension balancing aerodynamic drag everywhere. Flux
rings with diameters smaller than the charateristic length scale of
the flow are much more likely to collapse than larger rings with the
same flux. Scaling arguments predict an asymoptotic field strength
given by: $ Bas ~ 3.7 rho ^ {2/3} l ^ {2/3} v_l ^ {4/3} Phi
(-1/3) , where\rho is the mass density, l is the charateristic velocity
scale, v_l is the velocity amplitude at length scale l, and \Phi$ is
the magnetic flux in the fibril. The implications of these results,
and other properties of fibril fields for a fibril dynamo model are
disscussed. In particular, we consider the combination of fibril
dynamics and fibril reconnection in a simplified fibril dynamo. The
prospects of full, 3-D multi-fibril simulations with reconnection
are examined.
Title: Magnetic Reconnection in Incompressible Fluids
Authors: Deluca, Edward E.; Craig, Ian J.
Bibcode: 1992ApJ...390..679D
Altcode:
The paper investigates the dynamical relaxation of a disturbed
X-type magnetic neutral point in a periodic geometry, with an
ignorable coordinate, for an incompressible fluid. It is found that
the properties of the current sheet cannot be understood in terms
of steady state reconnection theory or more recent linear dynamical
solutions. Accordingly, a new scaling law for magnetic reconnection
is presented, consistent with fast energy dissipation (i.e., the
dissipation rate at current maximum is approximately independent of
magnetic diffusivity (eta)). The flux annihilation rate, however,
scales at eta exp 1/4, faster than the Sweet-Parker rate of sq rt
eta but asymptotically much slower than the dissipation rate. These
results suggest a flux pile-up regime in which the bulk of the free
magnetic energy is released as heat rather than as kinetic energy of
mass motion. The implications of our results for reconnection in the
solar atmosphere and interior are discussed.
Title: On the Dynamics of Emerging Toroidal Magnetic Flux Tubes
Authors: Fan, Y.; Fisher, G. H.; Deluca, E. E.
Bibcode: 1992AAS...180.0502F
Altcode: 1992BAAS...24..733F
We study the dynamic evolution of emerging toroidal magnetic flux
rings in the solar convective envelope by carrying out 3D numerical
simulations based on the thin flux tube approximation of Spruit. We
find: 1)For an axisymmetric flux ring, the aerodynamic drag force
experienced by the ring when moving with respect to the ambient
fluid transfers no angular momentum to the ring. Therefore in
both cases, with or without the drag force, the ring moves nearly
parallel to the rotational axis of the sun and emerges at a latitude
significantly poleward of sunspot zones, as pointed out by Choudhuri
and Gilman. However, for a non-axisymmetric flux ring (i.e. with
wave-like undulations along its circumference), the aerodynamic drag
force can transfer angular momentum to the flux ring, and therefore
reduces the latitude of flux emergence to within the observed sunspot
latitudes. 2)As each apex of a flux loop rises due to the magnetic
buoyancy force, gas inside the flux tube tends to diverge from the
apex. In the meantime, however, the Coriolis force drives a flow
within the flux tube opposite to the direction of rotation. Thus the
point of maximum divergence in the flow within the tube is shifted
from the apex into the leading side (in the direction of rotation)
of the emerging loop. The evacuation of plasma from the leading side
of the loop results in a much lower internal gas pressure there as
compared to that in the following side at the same depth. Therefore,
the magnetic field strength is stronger on the leading side. The
numerical simulations show that the field strength in the leading side
of the loop can be twice as large as that of the following side at the
same depth. This result offers a simple explanation for the observed
fact that the leading polarity of an active region is more compact,
forms sunspots more easily, and has a longer life time than does the
following polarity.
Title: Amplification of Fibril Magnetic Fields by Chaotic Flows
Authors: Fisher, George H.; Deluca, Edward E.; Patten, Brian M.
Bibcode: 1992ASPC...27..173F
Altcode: 1992socy.work..173F
No abstract at ADS
Title: Magnetic Flux Tubes in a 3D Chaotic Flow Field
Authors: Fisher, G. H.; Deluca, E. E.; Patten, B. M.
Bibcode: 1992ASPC...26..240F
Altcode: 1992csss....7..240F
No abstract at ADS
Title: Development of hard-turbulent convection in two dimensions:
Numerical evidence
Authors: Werne, J.; Deluca, E. E.; Rosner, R.; Cattaneo, F.
Bibcode: 1991PhRvL..67.3519W
Altcode:
New numerical evidence for a transition to hard turbulence in 2D
Boussinesq convection is presented. These 2D simulations agree with
some, but not all, experimental results for the scaling properties of
3D hard turbulence. The transition to 2D hard turbulence, as measured
by a change in the Nusselt-Rayleigh scaling law, coincides with a
gradual change in the velocity probability distribution from Gaussian
to exponential form and with the development of a ``well-mixed''
central region.
Title: On the Dissipation of Magnetic Fields in the Solar Convection
Zone
Authors: Deluca, E. E.; Fisher, G. H.
Bibcode: 1991BAAS...23.1048D
Altcode:
No abstract at ADS
Title: A New Numerical Model of Thin Flux Tubes in Three Dimensions
Authors: Patten, B. M.; Fisher, G. H.; Deluca, E. E.
Bibcode: 1991BAAS...23R1051P
Altcode:
No abstract at ADS
Title: The solar dynamo.
Authors: Deluca, E. E.; Gilman, P. A.
Bibcode: 1991sia..book..275D
Altcode:
The authors discuss the present state of our understanding of the
origin of the Sun's magnetic field. They begin with an introduction
to the theory of magnetic field generation in rotating, conducting
fluids. Next they consider a dilemma that has persisted for some 15
yr, namely the inconsistency of the kinematic and dynamic convection
zone dynamo models. A resolution of this dilemma has been suggested
by the recent helioseismology observations on the rotation rate as a
function of latitude and depth. These observations, together with other
observational and theoretical constraints, suggest that the solar dynamo
operates not in the convection zone, but rather in a thin layer between
the convection zone and the radiative interior. A model of such a dynamo
is presented and discussed. The authors conclude by discussing the
problems posed by the placement of the dynamo below the convection zone.
Title: Numerical simulations of soft and hard turbulence: Preliminary
results for two-dimensional convection
Authors: Deluca, E. E.; Werne, J.; Rosner, R.; Cattaneo, F.
Bibcode: 1990PhRvL..64.2370D
Altcode:
We report results on the transition from soft to hard turbulence in
simulations of 2D Boussinesq convection. The computed probability
densities for temperature fluctuations are exponential in form in both
soft and hard turbulence, unlike what is observed in experiments; in
contrast, we obtain a change in the Nusselt number scaling on Rayleigh
number in good agreement with the 3D experiments.
Title: Solar Dynamo Theory: Current Problems and Future Prospects
Authors: Deluca, E. E.
Bibcode: 1990BAAS...22..890D
Altcode:
No abstract at ADS
Title: The Physics of an Interface Dynamo
Authors: Deluca, E. E.; Gilman, P. A.
Bibcode: 1989BAAS...21R.842D
Altcode:
No abstract at ADS
Title: On the Two-Dimensional Inversion of Helioseismology Data to
Obtain the Internal Rotation Curve of the Sun
Authors: Horner, S.; Rosner, R.; Deluca, E. E.; Jeffrey, W.
Bibcode: 1989BAAS...21..842H
Altcode:
No abstract at ADS
Title: Angular Momentum Transport and Dynamo Action in the Sun:
Implications of Recent Oscillation Measurements
Authors: Gilman, Peter A.; Morrow, Cherilynn A.; Deluca, Edward E.
Bibcode: 1989ApJ...338..528G
Altcode:
The implications of a newly proposed picture of the sun's internal
rotation (Brown et al., 1989; Morrow, 1988) for the distribution
and transport of angular momentum and for the solar dynamo are
considered. The new results, derived from an analysis of solar acoustic
oscillations, affect understanding of how momentum is cycled in the sun
and provide clues as to how and where the solar dynamo is driven. The
data imply that the only significant radial gradient of angular velocity
exists in a transitional region between the bottom of the convection
zone, which is rotating like the solar surface, and the top of the deep
interior, which is rotating rigidly at a rate intermediate between the
equatorial and polar rates at the surface. Thus the radial gradient
must change sign at the latitude where the angular velocity of the
surface matches that of the interior. These inferences suggest that
the cycle of angular momentum that produces the observed latitudinal
differential rotation in the convection zone may be coupled to layers
of the interior beneath the convection zone.
Title: On the effects of Cosmions upon the structure and evolution
of very low mass stars
Authors: Deluca, E. E.; Griest, K.; Rosner, R.; Wang, J.
Bibcode: 1989STIN...8920880D
Altcode:
A number of recent studies have suggested that cosmions, or WIMPS,
may play an important role in the energetics of the solar interior;
in particular, it has been argued that these hypothetical particles
may transport sufficient energy within the nuclear-burning solar core
so as to depress the solar core temperature to the point of resolving
the solar neutrino problem. Solutions to the solar neutrino problem
have proven themselves to be quite nonunique, so that it is of some
interest whether the cosmion solution can be tested in some independent
manner. It is argued that if cosmions solve the solar neutrino problem,
then they must also play an important role in the evolution of low mass
main sequence stars; and, second, that if they do so, then a simple
(long mean free path) model for the interaction of cosmions with
baryons leads to changes in the structure of the nuclear-burning core
which may be in principal observable. Such changes include suppression
of a fully-convective core in very low mass main sequence stars; and a
possible thermal runaway in the core of the nuclear burning region. Some
of these changes may be directly observable, and hence may provide
independent constraints on the properties of the cosmions required to
solve the solar neutrino problem, perhaps even ruling them out.
Title: On the Galactic Dynamo
Authors: Rosner, R.; Deluca, E.
Bibcode: 1989IAUS..136..319R
Altcode:
No abstract at ADS
Title: Angular momentum transport and dynamo action in the Sun:
a report on implications of a recent heliospheric estimate of solar
rotation.
Authors: Morrow, C. A.; Gilman, P. A.; Deluca, E. E.
Bibcode: 1988ESASP.286..109M
Altcode: 1988ssls.rept..109M
Gilman, Morrow and DeLuca have recently introduced some ideas about how
an emerging helioseismic picture of the Sun's internal rotation might
affect the understanding of angular momentum transport and turbulent
dynamic action in the solar interior. The present paper offers a
brief report and commentary on these issues. Analysis of the frequency
splittings of solar acoustic oscillations measured by Brown and Morrow
has suggested that the latitudinal differential rotation observed at the
surface persists throughout the convection zone, and that the rotation
is more uniform in the outer layers of the radiative interior. Taking
this picture at face value, the authors discuss qualitatively how
angular momentum must be transported in order to sustain the observed
rotation, the exchange of angular momentum between the convection zone
and radiative interior, and the action of a turbulent dynamo which might
be operating near the base of the convection zone. This new qualitative
scenario for the solar dynamo explains both the equatorward migration
of the zone where sunspots appear and the observed poleward migration
of non-sunspot magnetic field.
Title: Truncation Effects on a Nonlinear Solar Dynamo Model
Authors: Deluca, E.
Bibcode: 1988BAAS...20Q1009D
Altcode:
No abstract at ADS
Title: Implications of Recent Estimates of Solar Interior Rotation
for Angular Momentum Transport and Dynamo Action in the Sun
Authors: Gilman, P. A.; Morrow, C. A.; Deluca, E. E.
Bibcode: 1988BAAS...20..701G
Altcode:
No abstract at ADS
Title: Dynamo theory for the interface between the convection zone
and the radiative interior of a star part
Authors: Deluca, Edward E.; Gilman, Peter A.
Bibcode: 1988GApFD..43..119D
Altcode:
We discuss numerical solutions of nonlinear equations that model
magnetic field generation in a thin layer beneath the convection zone
of a late type star. The model equations were derived previously in
Paper I (DeLuca and Gilman, 1986b). Three main results are found: first,
the oscillating, dynamo wave solutions discussed in DeLuca and Gilman
(1986a) are shown to be a result of the severe truncation used in those
calculations; second, the induced velocity feld is shown to have an
important role in determining the spatial structure of the magnetic
field solutions; time dependent solutions have been found. These are
not wave-like solutions, rather the amplitude of different horizontal
wave modes vary in time. Further, we show that the exact solutions
found in Paper I are generally unstable, with the exception of those
that are independent of (latitude in our Cartesian geometry), which
are stable if the transient induced velocity field remains small. We
conclude that the induced velocity fields are an important ingredient
in any model of dynamo action below the solar convection zone.
Title: Magnetic Field Generation in the Overshoot Region Beneath
the Solar Convection Zone
Authors: Deluca, E. E.; Gilman, P. A.
Bibcode: 1987BAAS...19..945D
Altcode:
No abstract at ADS
Title: Dynamo Theory for a Thin Layer Between the Convection Zone
and the Radiative Zone of a Star. Formulation and Preliminary Results
Authors: Deluca, Edward E.; Gilman, Peter A.
Bibcode: 1986LNP...254..173D
Altcode: 1986csss....4..173D
No abstract at ADS
Title: Dynamo Theory for the Interface Between the Convection Zone
and the Radiative Interior of a Star.
Authors: Deluca, E. E.
Bibcode: 1986PhDT.........4D
Altcode: 1987DiAbI..47.4552D
In this thesis we examine the possibility that the solar dynamo
operates in a thin overshoot region between the convection zone and the
radiative interior. We are interested in understanding the interplay of
the magnetic fields and the induced velocity fields in this overshoot
layer. We derive model equations in Cartesian geometry which contain the
essential physics for the dynamo, presenting both analytic and numerical
solutions. In the model we solve the momentum, magnetic induction,
and continuity equations for axisymmetric large scale magnetic and
velocity fields in the presence of cyclonic turbulence. We have found a
family of exact, force free solutions to the nonlinear equations when
there is no imposed velocity shear. When the induced velocity fields
are large the exact solutions are unstable. The induced velocities
control the location of the peak in the magnetic energy spectrum
and the slope of the spectrum at high wavenumbers. The amplitude
of the induced velocity field varies greatly with variations in our
free parameters: the magnetic diffusivity, the viscous diffusivity,
and the total magnetic energy. In all cases solutions with no imposed
velocity shear show no oscillatory or "dynamo wave" character. When a
velocity shear is imposed across the layer oscillatory "dynamo wave"
solutions are generally found, even for rather weak shear. The induced
velocity fields now have a dual role, controlling the location of
the peak in the magnetic field and the slope of the spectrum at high
wavenumbers. In addition, the induced velocities oppose the propagation
of the magnetic fields and dramatically lengthen the periods of the
solutions. To our knowledge we have formulated the first detailed model
of a dynamo located in the overshoot layer beneath the convection zone
of a star. Our solutions show that the induced velocity field strongly
influences both the horizontal structure and periods of the magnetic
fields. These effects can not be included in kinematic models that
are commonly used to study the solar dynamo.
Title: Dynamo Theory for the Sun and Stars
Authors: Gilman, Peter A.; Deluca, Edward E.
Bibcode: 1986LNP...254..163G
Altcode: 1986csss....4..163G
No abstract at ADS
Title: Dynamo theory for the interface between the convection zone
and the radiative interior of a star
Authors: DeLuca, Edward Ernst
Bibcode: 1986PhDT........98D
Altcode:
No abstract at ADS
Title: Dynamo theory for the interface between the convection zone
and the radiative interior of a star
Authors: Deluca, Edward Ernst
Bibcode: 1986dtib.book.....D
Altcode:
No abstract at ADS
Title: Dynamo theory for the interface between the convection zone
and the radiative interior of a star: Part I model equations and
exact solutions
Authors: Deluca, Edward E.; Gilman, Peter A.
Bibcode: 1986GApFD..37...85D
Altcode:
In this paper we derive a set of equations which model magnetic
field generation and maintenance in a thin region, ( 104)km thick,
below the solar convection zone, and present some simple exact
solutions. Energy to drive the dynamo is assumed to come from helical
convection that overshoots into this region. Differential rotation
and meridional circulation result only from feedbacks by the induced
fields. The equations are derived for a homogeneous incompressible
fluid in Cartesian geometry. The momentum equation, magnetic induction
equation, and the continuity equation are included in the analysis. We
assume velocity and magnetic field patterns have an aspect ratio of
1/10 (radial to horizontal scale), that the large scale velocities
are smaller than the convection zone velocities, a few meters per
sec, and the large scale magnetic fields are of the order of 104
Gauss. Finally we assume that the time scale of interest is the
advective time scale. Using these assumptions, we derive governing
equations in which the Coriolis force balances the Lorentz force, the
pressure gradient force, and the viscosity, and in which the magnetic
fields are maintained by the effect but significantly modified by the
above velocity fields. The results of this model will be discussed in
following papers.
Title: The response of chromospheric emission lines to flares on YZ
Canis Minoris.
Authors: Worden, S. P.; Schneeberger, T. J.; Giampapa, M. S.; Deluca,
E. E.; Cram, L. E.
Bibcode: 1984ApJ...276..270W
Altcode:
Six flares of the dMe star YZ CMi have been observed with simultaneous
photometry and high-dispersion, time-resolved spectroscopy.The spectra
have temporal resolutions of 3 minutes with spectral resolutions
of 0.24 Å. The largest observed flare had a U band amplitude of
1.5 mag. Hα and Hβ line profiles did not broaden during any of the
observed flares, although the line center intensity increased by over a
factor of 2 during some flares. After the initial increase in intensity,
the emission line strength decreases but remains at enhanced levels
for hours following U band flares. The Hα flare luminosity and total
energy are compared to corresponding properties of solar flares.
Title: A search for red-dwarf members of the Coma star cluster.
Authors: Deluca, E. E.; Weis, E. W.
Bibcode: 1981PASP...93...32D
Altcode:
A photometric search for red dwarfs belonging to the Coma star cluster
is reported. Observations in B, V, R and I were obtained for 88 stars
in the region of the Coma cluster using a pulse-counting photometer
with a GaAs photomultiplier attached to a 0.9-m reflector. Cluster
membership of the stars was determined on the basis of the deviation of
stellar position in V, (B-V) and V, (R-I) diagrams from the nominal main
sequence. Of the 25 stars suggested as possible members by Artyukhina
(1955) and the 29 additional stars suggested by Malmquist (1927),
only three stars are found to be possible members on the basis of
this criterion. The possible membership of only one of the two stars
suggested by Argue and Kenworthy on the basis of proper motions and
photographic photometry is confirmed. It is concluded that the number
of red-dwarf members of the Coma cluster with V magnitudes between
10.5 and 15.5 is unlikely to be greater than ten.
Title: Photometry of possible members of the Hyades cluster. III.
Authors: Weis, E. W.; Deluca, E. E.; Upgren, A. R.
Bibcode: 1979PASP...91..766W
Altcode:
Photoelectric photometry in BVRI colors has been obtained for 61 stars
in the region surrounding the Hyades cluster. Almost all stars observed
here were found by Giclas or Luyten to possess proper motions resembling
those of confirmed Hyades members. They cover the ranges between 0.6
and 1.7 in (B-V) and 0.2 and 1.3 in (R-I) and are thus mostly late
G, K, and early M stars. Of these 61 stars, only 24 are found to be
probable members and five are found to be possible members from their
positions in either the V,(B-V) or V,(R-I) diagrams. Nonetheless,
these probable members enrich the cluster well beyond the list of Pels,
Oort, and Pels-Kluyver, especially in its southwestern quadrant.
Title: High Resolution Spectra of Stellar Flares
Authors: Worden, S. P.; Schneeberger, T. J.; Deluca, E.; Giampapa, M.
Bibcode: 1979BAAS...11..628W
Altcode:
No abstract at ADS
Title: Photometry of Praesepe in BVRI colors.
Authors: Upgren, A. R.; Weis, E. W.; Deluca, E. E.
Bibcode: 1979AJ.....84.1586U
Altcode:
Results are reported for BVRI photoelectric photometry of 55 stars
in the region of the Praesepe cluster. Distance moduli are derived
independently from V, B-V and V, R-I diagrams. These diagrams indicate
that five of the stars do not appear to be cluster members and that
13 others are possibly binary members of Praesepe. The remaining stars
are found to define a sequence similar in slope to that of the Hyades
and lying 3.0 mag below it. Best values of 6.20 + or - 0.05 mag for the
modulus and 174 + or - 4 pc for the distance of Praesepe are adopted.
Title: The Distance to Praesepe from R-I Photometry
Authors: Upgren, A. R.; Weis, E. W.; Deluca, E. E.
Bibcode: 1979BAAS...11..404U
Altcode:
No abstract at ADS