Author name code: kankelborg
ADS astronomy entries on 2022-09-14
author:"Kankelborg, Charles"
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Title: An Updated Model for the Effect of Atmospheric Absorption on
Sounding Rockets
Authors: Donders, Nicolas; Zank, Gary; Winebarger, Amy; Paxton, Larry;
Kankelborg, Charles; Vigil, Genevieve
Bibcode: 2022cosp...44.2593D
Altcode:
A very high-resolution R > 20,000 Far Ultraviolet full-disk,
solar spectrograph will be launched in the Spring of 2023. This paper
describes the in-flight wavelength calibration techniques and the
fortuitous retrieval of Earth's thermospheric information during
the flight. Building and calibration of the Full-sun Ultraviolet
Rocket Spectrograph (FURST) is currently underway. The purpose of
this instrument is to obtain the highest resolution and most complete
Far Ultra-Violet (FUV) spectra of the full disk Sun. This so-called
"Sun-as-a-star" spectra will allow direct comparisons between our Sun
and other stars measured by the Hubble Space Telescope (HST) and the
upcoming James Webb Space Telescope (JWST). The Solar Physics groups at
NASA Marshall Space Flight Center (MSFC) and Montana State University
(MSU) have been developing the tools and procedures necessary to achieve
the high spectral resolution goal. These include, among other things,
improved tracking of error propagation, in-situ monitoring of the
camera gain with a radioactive Fe-55 source, and the development of
a simulated spectral calibration map under a noisy diagnostic-lamp
signal. This mapping introduces a clocked CCD in order to obtain
sub-pixel spectral resolution and overcome the Nyquist limit by
about a factor of 2. Aside from the main purpose of FURST, we have
been investigating the effect of absorption in the upper atmosphere
at sounding-rocket altitudes (about 100-300 km). We present here
an improved model of the optical depth caused by the thermospheric
Oxygen cross-section and H and O self-absorption. This data-based
model uses concentric spherical shells to account for the curvature
of the Earth's atmosphere and refraction. Using these calculations,
we present the anticipated effect on the signal received by FURST,
how that signal changes over the course of the flight-path These
absorption peaks would provide wavelength fiducials at line-center
that might add to in-flight calibration of the instrument. Many
studies have found ways to correct for these so-called "Telluric"
lines. However, it may be that these lines can in fact be a useful tool
to further improve our calibration, rather than simply a nuisance to
be corrected for! Finally, we discuss the inversion problem: how we
could take actual flight data and back-out the atmospheric data (such
as density and temperature) from any such sounding rocket flight that
shows evidence of atmospheric absorption. ***This material is based
upon work supported by the NSF EPSCoR RII-Track-1.2a (Non-invasive
plasma diagnostics for LTP) Cooperative Agreement OIA-1655280. Any
opinions, findings, and conclusions or recommendations expressed in
this material are those of the authors and do not necessarily reflect
the views of the National Science Foundation.***
Title: Determining the Spectral Content of MOSES Images
Authors: Parker, Jacob D.; Kankelborg, Charles C.
Bibcode: 2022ApJ...932..130P
Altcode:
The Multi-Order Solar Extreme Ultraviolet Spectrograph (MOSES)
sounding rocket was launched from White Sands Missile Range on 2006
February 8th, to capture images of the Sun in the He II 303.8 Å
emission line. MOSES is a slitless spectrograph that forms images in
multiple spectral orders simultaneously using a concave diffraction
grating in an effort to measure line profiles over a wide field of
view from a single exposure. Early work on MOSES data showed evidence
of solar features composed of neither He II 303.8 Å nor the nearby
Si XI 303.3 Å spectral lines. We have built a forward model that uses
cotemporal EIT images and the Chianti atomic database to fit synthetic
images with known spectra to the MOSES data in order to quantify this
additional spectral content. Our fit reveals a host of dim lines that
alone are insignificant but combined contribute a comparable intensity
to MOSES images as Si XI 303.3 Å. In total, lines other than He II
303.8 Å and Si XI 303.3 Å contribute approximately 10% of the total
intensity in the MOSES zero order image. This additional content, if
not properly accounted for, could significantly impact the analysis
of MOSES and similar slitless spectrograph data, especially those
using a zero-order (undispersed) image. More broadly, this serves as
a reminder that multilayer EUV imagers are sensitive to a host of weak
contaminant lines.
Title: A CubeSat to Observe FUV Spectrum of the Sun as a Star
Authors: Panda, S. P.; Kankelborg, C. C. K.
Bibcode: 2022heli.conf.4042P
Altcode:
We develop the science case for an orbital FUV sun-as-a-star
spectrometer and assess the technical challenges of a CubeSat
implementation. We envision this as a sequel to FURST, which will
obtain high-resolution spectra daily over a period of years.
Title: The Full-Sun Ultraviolet Rocket Spectrometer: Filling in the
VUV Spectrum of the Sun as a Star
Authors: Bunn, C. E.; Kankelborg, C. C.
Bibcode: 2022heli.conf.4012B
Altcode:
The Full-Sun Ultraviolet Rocket Spectrometer (FURST) is a NASA
sub-orbital sounding rocket mission that will obtain the first
high-resolution, radiometrically-calibrated VUV spectrum of the Sun
as a star.
Title: Explosive Events in Full disk SUMER data in C IV and Ne VIII
Authors: Panda, Suman; Kankelborg, Charles; Winebarger, Amy
Bibcode: 2021AGUFMSH45D2400P
Altcode:
We have analyzed full disk scans of Vacuum Ultra Violet (VUV) emission
lines(C IV and Ne VIII) from SUMER onboard SOHO. With this data,
we have identified explosive events and looked at their contribution
to the disk averaged spectrum of the Sun. Explosive events are small
scale bursts of plasma which can be observed in the transition region
lines. They are characterized by enhanced emission in the wings of the
spectral lines. We have compared the number of explosive events in
C IV (1548.20 Angstrom) and Ne VIII (770.41 Angstrom). We have also
looked at the relationship between spectral line width with their
integrated intensity. This analysis is especially helpful in light of
the planned launch of Full-sun Ultraviolet Rocket SpecTrometer (FURST),
in August 2022. FURST is a sounding rocket spectrometer that aims to
obtain high resolution full disk spectra of the Sun in VUV wavelength
range. Analyzing data from SUMER, gives us an idea of what FURST is
going to see.
Title: Investigating Geocoronal Absorption for Wavelength Calibration
of Sounding Rockets
Authors: Donders, Nicolas; Winebarger, Amy; Kankelborg, Charles;
Vigil, Genevieve; Paxton, Larry; Zank, Gary
Bibcode: 2021AGUFMSH52A..07D
Altcode:
Due to the high spectral resolution goals (R > 2x104) for the
upcoming Full-sun Ultraviolet Rocket Spectrograph (FURST), instrument
calibration will be particularly important. The Solar Physics groups
at NASA MSFC and Montana State University (MSU) have been developing
the tools necessary to achieve this goal. These include improved
tracking of error propagation, in-situ monitoring of the camera
gain with a radioactive Fe-55 source, and even better wavelength
calibration. This presentation will focus on the latter. We will
highlight the development of a calibration method which uses a
two-dimensional second-order polynomial to map pixels to wavelength
under a simulated noisy diagnostic lamp signal. Additionally, we have
introduced a tilted CCD in order to overcome the Nyquist limit. With
this as the background, we have been investigating an effect known
well among ground-based imaging: geocoronal absorption. We have been
looking into how much this effect will be present in the atmosphere
at sounding-rocket altitudes (~100-200 km). Many studies have found
ways to correct for these so-called "Telluric" lines. However, it may
be that these lines can in fact be a useful tool to further improve
our calibration, rather than simply a nuisance to be corrected for!
Title: Design for a portable calibration system for the Full-sun UV
Rocket SpecTrometer instrument
Authors: Vigil, Genevieve D.; Winebarger, Amy; Rachmeler, Laurel;
Donders, Nicolas; Athiray, P. S.; Kobayashi, Ken; Kankelborg, Charles
Bibcode: 2021JATIS...7c5009V
Altcode:
The Full-sun Ultraviolet Rocket SpecTrograph (FURST) is a sounding
rocket designed to acquire the first full-disk integrated high
resolution vacuum ultraviolet (VUV) spectra of the Sun. The data
enable analysis of the Sun comparable to stellar spectra measured
by astronomical instruments such as those on board the Hubble Space
Telescope. The mission is jointly operated by teams at Montana State
University (MSU), developing the instrument, and Marshall Space Flight
Center (MSFC), developing the camera and calibration systems, and is
scheduled to launch from White Sands Missile Range, New Mexico, in
2022. This mission requires the development of a pre- and post-launch
calibration plan for absolute radiometric and wavelength calibration
to reliably generate Hubble analogue spectra. Absolute radiometric
calibration, though initially planned to be performed at the National
Institute for Standards and Technology (NIST) calibration facilities,
is now planned to be completed with a portable VUV calibration
system provided by MSFC, due to instrument incompatibilities with
NIST infrastructure. The portable calibration system is developed
to provide absolute wavelength calibration and track changes in
calibration over the duration of the mission. The portable calibration
system is composed mainly of a VUV collimator equipped with an extreme
ultraviolet line source and calibrated photodiodes. The calibration
system is developed to accommodate both repeatable wavelength and
radiometric testing of the FURST instrument at various test sites
before and after launch. Presented here are the requirements, design,
and implementation of this portable calibration system with a focus
on those features most significant to radiometric measurements.
Title: A "Solar Space Elevator": Imaging and Spectroscopic Analysis
of Small Eruptions Observed by IRIS and SDO/AIA
Authors: Brannon, S.; Kankelborg, C.
Bibcode: 2021AAS...23832202B
Altcode:
Magnetic reconnection is typically understood to be an important
driver of energy release in the solar corona and chromosphere. Plasma
that is heated and accelerated upward along magnetic field structures
carries indirect information on conditions in the reconnection region
and current sheet located near the structure base. On 2016-Oct-14,
the Interface Region Imaging Spectrograph (IRIS) and Solar Dynamics
Observatory / Atmospheric Imaging Assembly (SDO/AIA) observed a
series of small (i.e. no GOES class) eruptions in NOAA AR 12599. These
eruptions originated in a unique structure projecting upward from the
AR, which displays a length-to-width ratio that exceeds 50 and remains
remarkably straight throughout its evolution. Several bright blobs of
plasma can be observed to ascend and subsequently descend along the
structure, giving the appearance of elevator cars. These eruptions are
cotemporal with footpoint and arcade brightenings, which we believe
indicate repeated episodes of reconnection at the structure base. We
present our analysis of imaging and spectroscopic data of the eruption
and footpoint plasma. We determine properties of the "elevator car"
plasma, including the line-of-sight inclination, the temperature and
density structure, and lift-off velocities and accelerations of jet
eruptions. We use these properties to constrain the geometry of the
"elevator" structure and conditions in the reconnection region.
Title: A New View of the Solar Interface Region from the Interface
Region Imaging Spectrograph (IRIS)
Authors: De Pontieu, Bart; Polito, Vanessa; Hansteen, Viggo; Testa,
Paola; Reeves, Katharine K.; Antolin, Patrick; Nóbrega-Siverio,
Daniel Elias; Kowalski, Adam F.; Martinez-Sykora, Juan; Carlsson,
Mats; McIntosh, Scott W.; Liu, Wei; Daw, Adrian; Kankelborg, Charles C.
Bibcode: 2021SoPh..296...84D
Altcode: 2021arXiv210316109D
The Interface Region Imaging Spectrograph (IRIS) has been obtaining
near- and far-ultraviolet images and spectra of the solar atmosphere
since July 2013. IRIS is the highest resolution observatory to provide
seamless coverage of spectra and images from the photosphere into the
low corona. The unique combination of near- and far-ultraviolet spectra
and images at sub-arcsecond resolution and high cadence allows the
tracing of mass and energy through the critical interface between the
surface and the corona or solar wind. IRIS has enabled research into the
fundamental physical processes thought to play a role in the low solar
atmosphere such as ion-neutral interactions, magnetic reconnection, the
generation, propagation, and dissipation of waves, the acceleration of
non-thermal particles, and various small-scale instabilities. IRIS has
provided insights into a wide range of phenomena including the discovery
of non-thermal particles in coronal nano-flares, the formation and
impact of spicules and other jets, resonant absorption and dissipation
of Alfvénic waves, energy release and jet-like dynamics associated
with braiding of magnetic-field lines, the role of turbulence and the
tearing-mode instability in reconnection, the contribution of waves,
turbulence, and non-thermal particles in the energy deposition during
flares and smaller-scale events such as UV bursts, and the role of flux
ropes and various other mechanisms in triggering and driving CMEs. IRIS
observations have also been used to elucidate the physical mechanisms
driving the solar irradiance that impacts Earth's upper atmosphere,
and the connections between solar and stellar physics. Advances in
numerical modeling, inversion codes, and machine-learning techniques
have played a key role. With the advent of exciting new instrumentation
both on the ground, e.g. the Daniel K. Inouye Solar Telescope (DKIST)
and the Atacama Large Millimeter/submillimeter Array (ALMA), and
space-based, e.g. the Parker Solar Probe and the Solar Orbiter, we aim
to review new insights based on IRIS observations or related modeling,
and highlight some of the outstanding challenges.
Title: Convolutional Neural Networks for Tomographic Imaging
Spectroscopy of the Solar Atmosphere
Authors: Smart, R.; Kankelborg, C. C.; Parker, J. D.
Bibcode: 2020AGUFMSH0480003S
Altcode:
The EUV Snapshot Imaging Spectrograph (ESIS) is an tomographic
imaging spectrograph designed to measure spectral line profiles over
a 2D field-of-view with much faster cadence than a rastering slit
spectrograph. ESIS uses four independent slitless spectrographs, each
with a different dispersion direction but all fed from the same primary
mirror. To recover spectral line profiles from this arrangement, the
images from each slitless spectrograph are interpreted using computed
tomography algorithms. With only four independent spectrographs, this is
a classic limited-angle tomography problem. We trained a convolutional
neural network to solve this tomography problem using observations from
the Coronal Diagnostic Spectrometer (CDS) as a training dataset. We will
present the performance of this network along with its application to
the observations gathered during the 2019 ESIS sounding rocket flight.
Title: Doppler Measurements of Transition Region Transient Events
at 630 Angstroms from the ESIS Sounding Rocket
Authors: Parker, J. D.; Smart, R.; Goldsworth, N. C.; Kankelborg,
C. C.; Winebarger, A. R.; Kobayashi, K.; Rachmeler, L.
Bibcode: 2020AGUFMSH0480004P
Altcode:
The EUV Snapshot Imaging Spectrograph (ESIS) was launched on board
a sounding rocket on September 30th, 2019 from White Sands Missile
Range. ESIS is a slitless spectrograph that captures spectral line
profiles over an extended field of view in a single "snapshot". Since
each of the four ESIS channels contains a unique combination of spatial
and spectral information it must be inverted to recover a line profile
at each spatial pixel. We present a preliminary inversion of the O
V 630 angstrom images captured by ESIS and an interpretation of line
profiles associated with several solar transient events within.
Title: Using an Fe-55 Source for Gain Fluctuation Characterization
in Sounding Rockets
Authors: Donders, N.; Winebarger, A. R.; Kankelborg, C. C.; Vigil,
G. D.; Kobayashi, K.; Rachmeler, L.; Zank, G. P.
Bibcode: 2020AGUFMSH0480006D
Altcode:
CCD cameras used in sounding rocket instruments and satellites
have a commonly known response to changes in temperature, pressure,
and other factors. Characterizing the signal noise for our Full-sun
Ultraviolet Rocket SpecTrograph (FURST) instrument has shown that
of these responses, the fluctuation in gain is the main driver
for variance in the readout signal when compared with calibration
consistency (see Vigil et al. 2020 in SPIE). For this instrument,
we must obtain spectral knowledge of Doppler-shifts smaller than 3
km/s (R > 10,000). Acquiring such a high level of precision in the
calibration of the optics and cameras requires small error margins in
the fluctuation of the gain. Previous work with the ESIS instrument
has provided numerous camera calibration test data, the same camera
which will be used in the FURST instrument. Using these data, we were
unable to show that external factors such as temperature changes can
accurately predict gain fluctuations for our instrument setup. However,
we have found that the use of an Fe-55 radioactive source as a control
spectrum can directly quantify the gain variation contributing to the
readout of the solar spectrum. Using flux rates of our current Fe-55
source, we perform a statistical analysis of the integration time
required for an acceptable characterization of gain fluctuation. This
analysis allows us to calculate the necessary size and position of the
radioactive source within the instrument payload, making it possible
to characterize gain during testing and flight of the sounding rocket.
Title: Explosive Event Contribution to the IRIS Si IV Transition
Region Lines of the Sun-as-a-Star
Authors: Bunn, C. E.; Kankelborg, C. C.
Bibcode: 2020AGUFMSH0480005B
Altcode:
This study aims to uncover the signature of FUV explosive events
(EEs) in Si IV full-disk mosaics (FDMs) taken by the Interface Region
Imaging Spectrograph (IRIS). The IRIS FDMs allow for the opportunity
to detect individual EEs across the disk and accurately measure the
disk-integrated spectrum both with and without the EE contribution. To
this end, we have taken careful account of sources of error in the
IRIS data such as bias estimation and backgrounds. The expected
signature in summed spectra of the full disk is a small enhancement
of the tails of the emission line, which is challenging to measure
accurately. If the disk-integrated EE contribution to the wings of TR
lines can be separated from the continuum and instrumental backgrounds,
then EE detection in the Sun-as-a-star and in Sun-like stars may be
possible. This research is motivated by the NASA suborbital sounding
rocket mission known as the Full-sun Ultraviolet Rocket SpecTrograph
(FURST), which is set to launch in late 2022, and also by the prospect
of comparing FURST data with Hubble Space Telescope (HST) spectra of
Sun-like stars.
Title: A Neural Network-based Data Analysis Technique for the EUV
Snapshot Imaging Spectrograph
Authors: Smart, R.; Kankelborg, C. C.; Parker, J. D.; Courrier, H.;
Winebarger, A. R.; Kobayashi, K.; Rachmeler, L.
Bibcode: 2019AGUFMSH31C3321S
Altcode:
The EUV Snapshot Imaging Spectrograph (ESIS) is a sounding rocket-borne
computed tomography (CT) imaging spectrograph designed to observe
the solar atmosphere in the O V (630 Å) spectral line. We are
developing a neural network-based data CT algorithm for analyzing ESIS
observations. This algorithm uses observations from the Interface Region
Imaging Spectrograph (IRIS) and the Hinode EUV Imaging Spectrograph
(EIS) as a synthetic sun to train a neural network to invert a forward
model of ESIS. We present progress on this algorithm, with performance
tests and initial results from the ESIS dataset.
Title: Wavelength Calibration of the Full-Sun Ultraviolet Rocket
SpecTrometer (FURST)
Authors: Donders, N.; Winebarger, A. R.; Kankelborg, C. C.; Vigil,
G. D.; Kobayashi, K.; Rachmeler, L.; Zank, G. P.
Bibcode: 2019AGUFMSH31C3325D
Altcode:
The Full-sun Ultraviolet Rocket SpecTrometer (FURST) is a sounding
rocket payload being developed by Montana State University (MSU)
alongside the Marshall Space Flight Center (MSFC) Solar Physics
Group. Scheduled to launch at the end of 2021, this sounding rocket is
unique in that it will produce the highest resolution full-disk FUV
spectra to-date of the Sun; this will allow for direct comparison
of stars by way of comparable resolution data gathered by Hubble
(HST). The main purpose of this research is to develop a simulation
of an incident signal with approximations for photon noise, CCD
electronic readout noise, and statistical error, to be used during
the calibration of FURST. This crucial step will allow us to develop
the necessary error budget to meet the 3 km/s Doppler-shift required
to resolve the relative motion of the low-temperature plasma in the
chromosphere and lower corona. The simulation results and their impact
on the calibration process shall be discussed. Future work includes
absolute radiometric and wavelength calibration in collaboration with
NIST. This material is based upon work supported by the NSF EPSCoR
RII-Track-1.2a (Non-invasive plasma diagnostics for LTP) Cooperative
Agreement OIA-1655280. Any opinions, findings, and conclusions or
recommendations expressed in this material are those of the authors and
do not necessarily reflect the views of the National Science Foundation.
Title: The Signature of Explosive Events in the FUV Spectrum of the
Sun as a Star
Authors: Bunn, C. E.; Kankelborg, C. C.
Bibcode: 2019AGUFMSH31C3324B
Altcode:
A NASA suborbital sounding rocket mission known as the Full-sun
Ultraviolet Rocket SpecTrometer (FURST) is being developed for launch
in late 2021 and will obtain the first high-resolution, high-quality
VUV spectrum of the Sun as a star. FURST will open new insights into
solar activity, placing the Sun in context with other stars. FURST
spectra will also have broad applications in solar system and
climate science. One of the science goals of FURST is the detection of
explosive events (EEs) in the solar transition region (TR). EEs appear
as suprathermal broadenings in TR emission line observations. If the
disk-integrated signature of EEs in the wings of TR emission lines
can be clearly separated from continuum and instrumental backgrounds,
then it will open a window to comparing solar and stellar atmospheres
in quiescent (non-flaring) conditions. In an effort to learn whether
this may be accomplished with existing solar data (albeit in a narrow
spectral window), we have identified EEs in monthly Interface Region
Imaging Spectrograph (IRIS) full-disk mosaics (FDMs), and quantified
their contribution to the full-disk integrated spectrum in strong TR
lines. The integrated IRIS FDM spectra can be compared directly to
Hubble Space Telescope (HST) spectra of Sun-like stars.
Title: A Preliminary Study of the Data From the ESIS/MOSES III
Sounding Rocket Flight and Coordinating Observatories
Authors: Parker, J. D.; Kankelborg, C. C.; Smart, R.; Courrier, H.;
Winebarger, A. R.; Kobayashi, K.; Rachmeler, L.
Bibcode: 2019AGUFMSH31C3320P
Altcode:
The EUV Snapshot Imaging Spectrograph (ESIS) and Multi-Order Solar
EUV Spectrograph (MOSES) instruments were launched on board a single
sounding rocket in the summer of 2019. MOSES and ESIS are slitless
spectrographs that can capture line profiles over an extended field
of view in a single "snapshot". By measuring spectral data over a
large field of view in a single exposure, MOSES and ESIS can better
describe the evolution of solar events that evolve more quickly than
traditional slit spectrographs can raster. We present a preliminary
study of small transient brightenings in the lower solar atmosphere
captured by MOSES, ESIS, and coordinating instruments Hinode, the Solar
Dynamics Observatory (SDO), and the Interface Region Imaging Spectrograh
(IRIS).
Title: Automated Analysis of Transition Region Plasma Characteristics
Under Hot Coronal Footpoints
Authors: Atwood, S.; McCarthy, M.; Kankelborg, C. C.
Bibcode: 2019AGUFMSH53B3367A
Altcode:
In previous work, we examined Si IV 1393.78 Angstrom line profiles
from the IRIS satellite mission under hot loop footpoints. We expand
our analysis using composite SDO images, which are co-spatial and
co-temporal with many-step IRIS raster scans, to quantify varying plasma
characteristics under footpoints and the rest of active region at large.
Title: First Flight of the EUV Snapshot Imaging Spectrograph
Authors: Kankelborg, C. C.; Parker, J. D.; Smart, R.; Winebarger,
A. R.; Kobayashi, K.; Rachmeler, L.; Courrier, H.
Bibcode: 2019AGUFMSH33A..05K
Altcode:
The solar atmosphere is highly dynamic and morphologically
complex. Solar transient phenomena such as flares, eruptions,
and explosive events evolve on time scales too fast to be covered
effectively by slit spectrograph rasters. The EUV Snapshot Imaging
Spectrograph (ESIS) is a new suborbital rocket-borne slitless
spectrograph that collects four simultaneous images (expandable to six),
each formed by a grating with its dispersion oriented at a different
angle. The purpose of this arrangement is to collect enough data in
a single exposure to infer spectral line profiles across a large, 2D
field of view. We report on the first flight of ESIS, observing O V
(63.0 nm) and Mg X (61.0, 62.5 nm) for about five minutes during solar
minimum. Also included in the rocket experiment for its third flight
is the Multi-Order Solar EUV Spectrograph (MOSES), the predecessor
of ESIS. In its current configuration, MOSES images Ne VII (46.5 nm)
in three spectral orders from a single objective grating. We present
the combined observations from MOSES and ESIS, covering the solar
atmosphere from transition region to corona.
Title: A Modified Kirkpatrick-Baez Design for a Practical Astronomical
X-ray Telescope
Authors: Longcope, Dana; Acton, Loren W.; Kankelborg, Charles
Bibcode: 2019AAS...23430101L
Altcode:
Kirkpatrick-Baez (K-B) optics offer a means of imaging soft x-rays
with modest resolution and a multi-arc-minute field of view at a cost
far below the conventional Wolter design. Such a low-cost system could
be useful for dedicated, long time-line observation of astronomical
x-ray sources from orbit. A K-B telescope consists of crossed arrays
of parabolic mirrors at grazing incidence. The classic K-B design is
subject to significant aberration, arising from interplay between
the focusing of the fore and aft mirror arrays. We demonstrate
here a modified K-B design with aberrations reduced by an order of
magnitude. We show, furthermore, that it is possible to construct
such a system by constraining flat "slats" of commercially-available
glass in precision machined grooves. The slats deform into shapes which
adequately approximate the optimal figures, thereby yielding focusing
better than the best version of the classic K-B design. The result is a
new approach that greatly simplifies the task of achieving both useful
resolution and high effective area for x-ray astronomy applications.
Title: Analyzing deviations from optically thin emission in flare
ribbon plasma using IRIS observations of Si IV resonance lines
Authors: Brannon, Sean; Kankelborg, Charles
Bibcode: 2019AAS...23420406B
Altcode:
It is well-established that the Si IV resonance line pair at 1394 and
1403 Å observed by the Interface Region Imaging Spectrograph (IRIS)
exhibits a 2:1 intensity ratio in optically thin plasma. Deviations
from this ratio may arise from optical thickness (Mathioudakis et
al. 1999) and/or geometric effects (Kerr et al. 2005) in the emitting
plasma. These effects are expected to be particularly prevalent in
the dense chromospheric plasma that forms the ribbons during a flare,
and the Si IV resonance line ratio therefore provides a diagnostic
of the plasma conditions at the flare loop footpoints. Recently,
Kerr et al. (2019) used RADYN simulations to demonstrate that a
significant fraction of the Si IV flare ribbon emission may form at
cooler temperatures, even for relatively small flares. Their results
showed changes to both line shape and intensity in flare plasma, and
they recommended caution when interpreting Si IV emission in flare
ribbons. Additionally, they noted that only a handful of studies
using IRIS observations have reported the line ratio in flares. In
this work, we report on our work to create a catalog of the line
ratio for additional flare ribbon events in the IRIS observation
database. We select IRIS observations of flares that record both
Si IV resonance lines with an 8-step or fewer raster, and identify
28 candidate observations for which the flare ribbon is covered by
the spectrograph slit. We establish criteria for identifying spectra
that capture flare ribbon emission and for eliminating spectra that
contain defects (e.g. saturated pixels). We calculate line intensities
(less background contribution) and construct the line ratio for all
selected spectra in each observation, and report the mean, median,
and deviation of the line ratio for each flare ribbon. Based on our
results, we briefly discuss physical implications for interpreting Si
IV emission in flare ribbons.
Title: Cross calibration for coalignment, Hinode/SOT, IRIS, and SDO
Authors: Yoshimura, Keiji; Kankelborg, Charles
Bibcode: 2019AAS...23410701Y
Altcode:
Yoshimura and McKenzie (Solar Physics, vol.290, p.2355, 2015) reported
the results of the successful cross calibration for the coalignments
between the X-Ray Telescope (XRT) onboard Hinode and two instruments
onboard Solar Dynamic Observatory (SDO), i.e., the Helioseismic and
Magnetic Imager (HMI) and the Atmospheric Imaging Assembly (AIA). We are extending the same calibration methods to other instruments,
which include: (1) the Interface Region Imaging Spectrograph (IRIS), (2)
the Solar Optical Telescope (SOT) onboard Hinode, and (3) AIA/HMI. We summarize the modification and optimization of the methodology
and present the results of the calibrations. Time variation of the roll
angles and the plate scales will be discussed. The results can be used
for better coalignment. We have also done the calibration between
different wavelengths of SOT filtergram data. After the corrections
using the calibration results, we can still see some offsets between
the different wavelength images which vary with the position of the
observing region on the solar disk. We attribute this to the differing
heights of formation associated with each wavelength band.
Title: Quiet-Sun Explosive Events Observed in He II λ304 with
MOSES-06
Authors: Rust, Thomas; Kankelborg, Charles C.
Bibcode: 2019ApJ...877...59R
Altcode:
In this paper the unique data from the Multi-Order Solar
Extreme-Ultraviolet Spectrograph (MOSES) are used to investigate
transition region explosive events in the He II λ304 spectral
line. Particular attention is paid to two example events: one
blueshifted jet and one bidirectional jet. Observations suggest
that these events consist exclusively of high-velocity (∼100 km
s-1) plasma. These two and other examples presented here
exhibit a striking lack of emission in the line core. No acceleration
phase is observed at the onset of either event. In total, 41 examples
of explosive events are identified, including 5 blueshifted jets, 2
redshifted jets, and 10 bidirectional jets. The remaining 24 events
resist simple classification, but observations indicate compact,
highly Doppler-shifted emission. Event spatial scales and lifetimes
are consistent with published explosive event characteristics. Data
from the Michelson Doppler Imager provide magnetic context to the
MOSES observations. Bidirectional jets lacking line core emission
are interesting because they are predicted in models of Petschek
reconnection in the transition region.
Title: Instrument Calibration of the Interface Region Imaging
Spectrograph (IRIS) Mission
Authors: Wülser, J. -P.; Jaeggli, S.; De Pontieu, B.; Tarbell,
T.; Boerner, P.; Freeland, S.; Liu, W.; Timmons, R.; Brannon, S.;
Kankelborg, C.; Madsen, C.; McKillop, S.; Prchlik, J.; Saar, S.;
Schanche, N.; Testa, P.; Bryans, P.; Wiesmann, M.
Bibcode: 2018SoPh..293..149W
Altcode:
The Interface Region Imaging Spectrograph (IRIS) is a NASA small
explorer mission that provides high-resolution spectra and images of
the Sun in the 133 - 141 nm and 278 - 283 nm wavelength bands. The
IRIS data are archived in calibrated form and made available to the
public within seven days of observing. The calibrations applied to
the data include dark correction, scattered light and background
correction, flat fielding, geometric distortion correction, and
wavelength calibration. In addition, the IRIS team has calibrated the
IRIS absolute throughput as a function of wavelength and has been
tracking throughput changes over the course of the mission. As a
resource for the IRIS data user, this article describes the details
of these calibrations as they have evolved over the first few years
of the mission. References to online documentation provide access to
additional information and future updates.
Title: An on Orbit Determination of Point Spread Functions for the
Interface Region Imaging Spectrograph
Authors: Courrier, Hans; Kankelborg, Charles; De Pontieu, Bart;
Wülser, Jean-Pierre
Bibcode: 2018SoPh..293..125C
Altcode:
Using the 2016 Mercury transit of the Sun, we characterize on orbit
spatial point spread functions (PSFs) for the Near- (NUV) and Far- (FUV)
Ultra-Violet spectrograph channels of NASA's Interface Region Imaging
Spectrograph (IRIS). A semi-blind Richardson-Lucy deconvolution method
is used to estimate PSFs for each channel. Corresponding estimates
of Modulation Transfer Functions (MTFs) indicate resolution of 2.47
cycles/arcsec in the NUV channel near 2796 Å and 2.55 cycles/arcsec
near 2814 Å. In the short (≈1336 Å ) and long (≈1394 Å )
wavelength FUV channels, our MTFs show pixel-limited resolution (3.0
cycles/arcsec). The PSF estimates perform well under deconvolution,
removing or significantly reducing instrument artifacts in the Mercury
transit spectra. The usefulness of the PSFs is demonstrated in a case
study of an isolated explosive event. PSF estimates and deconvolution
routines are provided through a SolarSoft module.
Title: Measuring Optical Thickness and Geometric Effects in Flare
Ribbon Plasma with Si IV Spectral Lines as Observed by IRIS
Authors: Brannon, Sean Robert; Kankelborg, Charles C.
Bibcode: 2018tess.conf30492B
Altcode:
It is well-established that the Si \textsc{iv} spectral line pair
at 1394 and 1403 \AA\ exist in a 2:1 intensity ratio in optically
thin plasma, and that deviations from this ratio arise as an effect of
optical thickness and/or geometric effects in the emitting plasma. These
effects are expected to be particularly prevalent in the bright,
dense chromospheric plasma that forms the ribbons during a flare, and
the Si \textsc{iv} line pair therefore provides a diagnostic of the
plasma conditions at the flare loop footpoints. The Interface Region
Imaging Spectrograph (IRIS) contains spectral windows that observe both
the Si \textsc{iv} 1394 and 1403 \AA\ spectral lines with a spatial
resolution of up to <svg xmlns:xlink="http://www.w3.org/1999/xlink"
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</g> </svg>, spectral resolution up to 26 m\AA, and temporal
resolution up to 1 s, which is ideal for detailed observations of
flare ribbon plasma. For our analysis, we select IRIS observations of
flares that record both Si \textsc{iv} lines with an 8-step or fewer
raster, and identify 26 potential observations for which the flare
ribbon is covered by the spectrograph slit. We establish criteria
for identifying spectra that capture flare ribbon emission, and for
eliminating spectra that contain defects (e.g. saturated pixels). We
calculate absolute intensities, Doppler shifts, line widths, and the
intensity ratio for the Si IV line pair for all selected spectra in
each event, and conduct a statistical analysis of these quantities
across our selected flares. The statistical results for the line ratio
are then correlated to the results for the individual spectral lines,
as well as to properties of the flare and active region, such as GOES
class, ribbon geometry, LOS angle, and magnetic field complexity.
Title: Blind technique for point spread function equalization with
application to the Multi-Order Solar Extreme Ultraviolet Spectrograph
Authors: Atwood, Shane; Kankelborg, Charles
Bibcode: 2018JATIS...4b8002A
Altcode:
When combining remote sensing data from multiple instruments or
multiple imaging channels, differences in point spread function
(PSF) can lead to systematic error. If the PSFs are not well known,
then it is difficult to determine which differences in the image data
are meaningful for the object being observed and which are artifacts
of PSF. Direct PSF measurements can be problematic. For example, in a
sounding rocket payload, launch vibrations and acceleration, subsequent
operations in micro gravity, and the impact on return to Earth may all
affect PSFs. We have developed a blind method to equalize the PSFs of
three distinct instrument channels, as found in the Multi-Order Solar
Extreme Ultraviolet Spectrograph (MOSES). To validate our technique,
we generate three synthetic images with three different PSFs, with some
spectrally interesting features. Thence, we demonstrate the successful
removal of PSF-induced artifacts is possible, with the genuine spectral
features left intact. We also perform blind PSF equalizations on
three copies of the same solar image, but with differing PSFs, after
applying independent noise to each. The results accurately reproduce
corrections performed in the absence of noise, with full knowledge of
the PSFs. Finally, we apply PSF equalization to solar images obtained
in the 2006 MOSES flight and demonstrate the removal of artifacts.
Title: Using local correlation tracking to recover solar spectral
information from a slitless spectrograph
Authors: Courrier, Hans T.; Kankelborg, Charles C.
Bibcode: 2018JATIS...4a8001C
Altcode:
The Multi-Order Solar EUV Spectrograph (MOSES) is a sounding rocket
instrument that utilizes a concave spherical diffraction grating
to form simultaneous images in the diffraction orders m=0, +1,
and -1. MOSES is designed to capture high-resolution cotemporal
spectral and spatial information of solar features over a large
two-dimensional field of view. Our goal is to estimate the Doppler
shift as a function of position for every MOSES exposure. Since
the instrument is designed to operate without an entrance slit, this
requires disentangling overlapping spectral and spatial information in
the m=±1 images. Dispersion in these images leads to a field-dependent
displacement that is proportional to Doppler shift. We identify these
Doppler shift-induced displacements for the single bright emission
line in the instrument passband by comparing images from each spectral
order. We demonstrate the use of local correlation tracking as a
means to quantify these differences between a pair of cotemporal
image orders. The resulting vector displacement field is interpreted
as a measurement of the Doppler shift. Since three image orders are
available, we generate three Doppler maps from each exposure. These
may be compared to produce an error estimate.
Title: Feel the Burn, Part II: Quantifying and mapping spectral,
spatial, and temporal structures of the transition region under hot
and cold coronal regions
Authors: Atwood, Shane; Kankelborg, Charles C.
Bibcode: 2017SPD....4810602A
Altcode:
The coronal volume is filled with magnetic field, yet only part of
that volume has sufficient volume to exhibit hot X-ray loops. Using
XRT and AIA images, we identify footpoints of hot coronal loops. We
then use IRIS rasters to compare the spatial, temporal, and spectral
structure of these relatively "heated" and "unheated" regions. We seek
a signature of upward-propagating energy that could be associated with
hot active region loops.
Title: Point-Spread Functions for the Near Ultraviolet Channel of
the Interface Region Imaging Spectrograph (IRIS)
Authors: Courrier, Hans; Kankelborg, Charles C.; De Pontieu, Bart;
Wülser, Jean-Pierre
Bibcode: 2017SPD....4811701C
Altcode:
We present point-spread functions (PSFs) for the near ultraviolet (NUV)
spectrograph channel of the Interface Region Imaging Spectrograph
(IRIS). The hard edge terminus of the 2016 Mercury transit of the
Sun is used to measure the PSFs near instrument center field of view
using an iterative semi-blind deconvolution method. The resulting PSFs
exhibit an asymmetrical core with broader wings when compared to the
theoretical diffraction limited PSFs. Deconvolution of our PSFs from
the original Level 2 images produces images with improved stray light
characteristics and increased contrast.
Title: Constraining reconnection region conditions using imaging
and spectroscopic analysis of a coronal jet
Authors: Brannon, Sean; Kankelborg, Charles
Bibcode: 2017SPD....4830404B
Altcode:
Coronal jets typically appear as thin, collimated structures in EUV
and X-ray wavelengths, and are understood to be initiated by magnetic
reconnection in the lower corona or upper chromosphere. Plasma that
is heated and accelerated upward into coronal jets may therefore
carry indirect information on conditions in the reconnection region
and current sheet located at the jet base. On 2017 October 14,
the Interface Region Imaging Spectrograph (IRIS) and Solar Dynamics
Observatory Atmospheric Imaging Assembly (SDO/AIA) observed a series of
jet eruptions originating from NOAA AR 12599. The jet structure has a
length-to-width ratio that exceeds 50, and remains remarkably straight
throughout its evolution. Several times during the observation bright
blobs of plasma are seen to erupt upward, ascending and subsequently
descending along the structure. These blobs are cotemporal with
footpoint and arcade brightenings, which we believe indicates multiple
episodes of reconnection at the structure base. Through imaging and
spectroscopic analysis of jet and footpoint plasma we determine
a number of properties, including the line-of-sight inclination,
the temperature and density structure, and lift-off velocities and
accelerations of jet eruptions. We use these properties to constrain
the geometry of the jet structure and conditions in reconnection region.
Title: Measuring Plasma Flows in Transition Region Loops Using the
MOSES Instrument
Authors: Smart, Roy; Kankelborg, Charles C.; Bonham, Nick; Courrier,
Hans
Bibcode: 2017SPD....4810610S
Altcode:
While traditional slit spectrographs have been extremely valuable for
observing coronal loops, the narrow slit of these instruments does
not allow the properties and dynamic evolution of coronal loops to be
measured simultaneously across their entire structure. The Multi-Order
Solar EUV Spectrograph (MOSES) is a rocket-borne slitless spectrograph
capable of measuring doppler shifts simultaneously over a wide field
of view. On August 27, 2015, we observed AR 12403 in Ne VII (46.5 nm)
at T ~ 500,000 K. We present time dependent measurements of downflow
velocities for loop footpoints, with physical interpretation based on
1D modeling.
Title: VUV Spectroscopy of the Sun as a Star
Authors: Kankelborg, Charles; Philip, Judge; Winebarger, Amy R.;
Kobayashi, Ken; Smart, Roy
Bibcode: 2017SPD....4811001K
Altcode:
We describe a new sounding rocket mission to obtain the first
high resolution, high quality VUV (100-200 nm) spectrum of the
Sun-as-a-star. Our immediate science goal is to understand better the
processes of chromospheric and coronal heating. HST data exist for a
dozen or so Sun-like stars of a quality already beyond our ability to
construct a comparable sun-as-a-star UV spectrum. The solar spectrum
we obtain will enable us to understand the nature of magnetic energy
dissipation as a Sun-like star evolves, and the dependence of magnetic
activity on stellar mass and metallicity. This poster presents the
instrument design, scientific prospects, and broader impacts of the
proposed mission.
Title: A 2D Discrete Surface Flux Transport (DSFT) model applied to
polar and quiet sun regions.
Authors: Eckberg, J.; Kankelborg, C. C.; Martens, P.
Bibcode: 2016AGUFMSH31B2551E
Altcode:
We have developed a Surface Flux Transport simulation utilizing
a Semi-Lagrangian scheme to advect discrete magnetic flux
elements. Advection occurs due to the flow fields from supergranulation,
meridional flow, and differential rotation. Granular advection is
modeled using a time integrated effect which lowers the computational
cost of the simulation. We have incorporated observational, energetic
and geometric considerations in constructing the magnetic flux dynamics
of emergence, interaction, and fragmentation. Our model reproduces
observed distributions of magnetic flux in quiet sun and at the
poles. The variation of mean squared velocities with flux is also
reproduced. Our simulation clarifies which processes are essential in
reproducing the dynamics of solar magnetic flux balance.
Title: An On Orbit Determination of Point Spread Functions for the
Interface Region Imaging Spectrograph (IRIS)
Authors: Courrier, H.; Kankelborg, C. C.; De Pontieu, B.; Wuelser,
J. P.
Bibcode: 2016AGUFMSH31B2576C
Altcode:
IRIS is a small explorer spacecraft that observes the solar photosphere,
chromosphere, transition region, and corona using a combination of
slit based spectrograph and slit-jaw imagers. The hard edge terminus
of the May 09, 2016 Mercury transit observed by IRIS is used to measure
on-orbit point spread functions (PSFs) for the near ultra-violet (NUV)
and far ultra-violet (FUV) spectrograph channels. The contribution of
the measured PSFs on spectrograph resolution is investigated.
Title: Feel the Burn: What accounts for spatial variations in
coronal heating?
Authors: Atwood, Shane; Kankelborg, Charles C.
Bibcode: 2016SPD....47.0312A
Altcode:
The coronal volume is filled with magnetic field, yet only part of
that volume has sufficient heating to exhibit hot x-ray loops. How
does the Sun decide where the heat goes? Using XRT and AIA images and
HMI magnetograms, we identify footpoints of hot coronal loops, and
magnetically similar regions underlying relatively unheated corona. We
then use IRIS rasters and sit-and-stare observations to compare
the spatial, temporal, and spectral structure of these relatively
``heated’’ and ``unheated’’ regions. We seek a signature of
upward propagating energy that could be associated with hot active
region loops.
Title: Preliminary Results of the MOSES II 2015 Flight
Authors: Smart, Roy; Courrier, Hans; Kankelborg, Charles
Bibcode: 2016SPD....4730901S
Altcode:
The Multi-Order Extreme Ultraviolet Spectrograph (MOSES) is a slitless
spectrograph which aims to produce simultaneous spatial-spectral
imaging of the solar transition region. This is accomplished through
a multilayer concave diffraction grating which produces three images
for the spectral orders m = 0, ± 1. The multilayer coating provides
a narrow passband, dominated by Ne VII (46.5 nm), which allows the
three images to be compared in order to determine line broadenings
and identify explosive events in the Solar Transition Region. Here,
we examine the preliminary results of MOSES II, the instrument’s
second flight which was launched on a sounding rocket from White Sands
Missile Range, NM in August 2015. We present the first images of the
Sun in Ne VII since Skylab and the preliminary results of observed
doppler shifts within an active region.
Title: Heating Profiles of Coronal Loops
Authors: Plowman, Joseph; Kankelborg, Charles C.; Martens, Petrus C.
Bibcode: 2016SPD....47.0328P
Altcode:
We analyze the temperature and density profiles of coronal
loops, as a function of their length, using data from SDO/AIA and
Hinode/EIS. The analysis considers the location of the heating along
the loop's length, and we conduct a more throrough investigation of our
previous preliminary result that heating is concentrated near the loop
footpoints. The work now features a larger selection of coronal loops,
compared to our previous presentations, and examines their scale-height
temperatures to ascertain the extent to which they are hydrostatic.
Title: Transition Region Explosive Events in He II 304Å: Observation
and Analysis
Authors: Rust, Thomas; Kankelborg, Charles C.
Bibcode: 2016SPD....4710101R
Altcode:
We present examples of transition region explosive events observed
in the He II 304Å spectral line with the Multi Order Solar EUV
Spectrograph (MOSES). With small (<5000 km) spatial scale and
large non-thermal (100-150 km/s) velocities these events satisfy
the observational signatures of transition region explosive
events. Derived line profiles show distinct blue and red velocity
components with very little broadening of either component. We observe
little to no emission from low velocity plasma, making the plasmoid
instability reconnection model unlikely as the plasma acceleration
mechanism for these events. Rather, the single speed, bi-directional
jet characteristics suggested by these data are consistent with
acceleration via Petschek reconnection.Observations were made during
the first sounding rocket flight of MOSES in 2006. MOSES forms images
in 3 orders of a concave diffraction grating. Multilayer coatings
largely restrict the passband to the He II 303.8Å and Si XI 303.3Å
spectral lines. The angular field of view is about 8.5'x17', or about
20% of the solar disk. These images constitute projections of the
volume I(x,y,λ), the intensity as a function of sky plane position
and wavelength. Spectral line profiles are recovered via tomographic
inversion of these projections. Inversion is carried out using a
multiplicative algebraic reconstruction technique.
Title: Determining the Spectral Content of MOSES Images
Authors: Parker, Jacob; Kankelborg, Charles
Bibcode: 2016SPD....47.0204P
Altcode:
The MOSES (Multi-Order Solar EUV Spectrograph) sounding rocket was
launched February 8th, 2006. The MOSES concave grating forms solar
images in multiple spectral orders, in an effort to measure line
profiles from a single exposure over a wide field of view. We present
a preliminary identification of spectral content in MOSES images. The
cross correlation of subtracted images provide evidence of spectral
content besides the normal 304 Anstrom He II line. We place confidence
on the peaks in correlation by cross correlating random data that is
statistically representative of MOSES data. These significant peaks
indicate a contribution to intensity from several coronal lines. These
lines are individually weak, but if not taken into account, they would
significantly increase the residuals when inverting MOSES images to
obtain spectra.
Title: Internetwork Chromospheric Bright Grains Observed With IRIS
and SST
Authors: Martínez-Sykora, Juan; Rouppe van der Voort, Luc; Carlsson,
Mats; De Pontieu, Bart; Pereira, Tiago M. D.; Boerner, Paul; Hurlburt,
Neal; Kleint, Lucia; Lemen, James; Tarbell, Ted D.; Title, Alan;
Wuelser, Jean-Pierre; Hansteen, Viggo H.; Golub, Leon; McKillop, Sean;
Reeves, Kathy K.; Saar, Steven; Testa, Paola; Tian, Hui; Jaeggli,
Sarah; Kankelborg, Charles
Bibcode: 2015ApJ...803...44M
Altcode: 2015arXiv150203490M
The Interface Region Imaging Spectrograph (IRIS) reveals small-scale
rapid brightenings in the form of bright grains all over coronal holes
and the quiet Sun. These bright grains are seen with the IRIS 1330,
1400, and 2796 Å slit-jaw filters. We combine coordinated observations
with IRIS and from the ground with the Swedish 1 m Solar Telescope
(SST) which allows us to have chromospheric (Ca ii 8542 Å, Ca ii H
3968 Å, Hα, and Mg ii k 2796 Å) and transition region (C ii 1334 Å,
Si iv 1403 Å) spectral imaging, and single-wavelength Stokes maps
in Fe i 6302 Å at high spatial (0\buildrel{\prime\prime}\over{.}
33), temporal, and spectral resolution. We conclude that the IRIS
slit-jaw grains are the counterpart of so-called acoustic grains,
i.e., resulting from chromospheric acoustic waves in a non-magnetic
environment. We compare slit-jaw images (SJIs) with spectra from the
IRIS spectrograph. We conclude that the grain intensity in the 2796
Å slit-jaw filter comes from both the Mg ii k core and wings. The
signal in the C ii and Si iv lines is too weak to explain the presence
of grains in the 1300 and 1400 Å SJIs and we conclude that the grain
signal in these passbands comes mostly from the continuum. Although
weak, the characteristic shock signatures of acoustic grains can often
be detected in IRIS C ii spectra. For some grains, a spectral signature
can be found in IRIS Si iv. This suggests that upward propagating
acoustic waves sometimes reach all the way up to the transition region.
Title: Imaging Spectroscopy of Transition Region Explosive Events
from MOSES Sounding Rocket Data
Authors: Rust, Thomas; Kankelborg, Charles
Bibcode: 2015TESS....120304R
Altcode:
The Multi-Order Solar EUV Spectrograph (MOSES) forms 304 Å EUV images
at three spectral orders from an objective multilayer grating. The
images encode spatial and spectral data over a 20 x 10 arc minute field
of view. Numerous examples of compact transient brightenings are present
in data obtained during a 2006 flight. We employ an inversion algorithm
which incorporates the instrument point spread functions and noise model
and present spectra derived thereby which show strong doppler shifts
associated with these brightenings. Spatial structure (0.5" pixels) and
temporal evolution (~10 s cadence) of these events will be presented.
Title: PSF-Corrected Inversion of MOSES Images: Validation With
IRIS Data
Authors: Atwood, Shane; Kankelborg, Charles
Bibcode: 2015TESS....140306A
Altcode:
The Multi-Order Solar EUV Spectrograph (MOSES) forms three Helium
304 images taken at the m=-1,0,+1 spectral orders. Subtle differences
between images encode line profile information. However, differences
in instrument point spread function (PSF) in the three orders lead
to non-negligible systematic errors in the retrieved profiles. The
PSF-corrected SMART 2 algorithm is designed to equalize the PSFs and
extract the spectral and doppler information. We apply the algorithm
to IRIS raster images to demonstrate the technique's effectiveness.
Title: Using Correlation Tracking to Disentangle Spatial and Spectral
Data in a Slitless Spectrograph
Authors: Courrier, Hans; Kankelborg, Charles
Bibcode: 2015TESS....140315C
Altcode:
In a typical slit style spectrograph, the limited field of view
afforded by the entrance slit is overcome by rastering the slit
across a feature of interest to build a composite image. While it is
trivial to separate spatial and spectral data in such an instrument,
the cadence of the raster results in a loss of temporal data when
attempting to image a feature that is much larger than the entrance
slit. The Multi-Order Solar EUV Spectrograph (MOSES) is a slitless
spectrograph that collects co-temporal spatial and spectral images in
He II 304 Å over a 10’ x 20’ field of view through the use of a
spherical diffraction grating. Local correlation tracking routines are
used to disentangle the spatial and spectral data from images formed by
the zero and both first orders of the MOSES instrument. The opposing
dispersion direction of the outboard orders allows a diagnostic of
the viability of the method when analyzing images obtained from the
February 2006 MOSES sounding rocket flight.
Title: Homologous Helical Jets: Observations By IRIS, SDO, and Hinode
and Magnetic Modeling With Data-Driven Simulations
Authors: Cheung, Mark C. M.; De Pontieu, B.; Tarbell, T. D.; Fu, Y.;
Tian, H.; Testa, P.; Reeves, K. K.; Martínez-Sykora, J.; Boerner,
P.; Wülser, J. P.; Lemen, J.; Title, A. M.; Hurlburt, N.; Kleint,
L.; Kankelborg, C.; Jaeggli, S.; Golub, L.; McKillop, S.; Saar, S.;
Carlsson, M.; Hansteen, V.
Bibcode: 2015ApJ...801...83C
Altcode: 2015arXiv150101593C
We report on observations of recurrent jets by instruments on board
the Interface Region Imaging Spectrograph, Solar Dynamics Observatory
(SDO), and Hinode spacecraft. Over a 4 hr period on 2013 July 21,
recurrent coronal jets were observed to emanate from NOAA Active Region
11793. Far-ultraviolet spectra probing plasma at transition region
temperatures show evidence of oppositely directed flows with components
reaching Doppler velocities of ±100 km s-1. Raster Doppler
maps using a Si iv transition region line show all four jets to have
helical motion of the same sense. Simultaneous observations of the
region by SDO and Hinode show that the jets emanate from a source
region comprising a pore embedded in the interior of a supergranule. The
parasitic pore has opposite polarity flux compared to the surrounding
network field. This leads to a spine-fan magnetic topology in the
coronal field that is amenable to jet formation. Time-dependent
data-driven simulations are used to investigate the underlying drivers
for the jets. These numerical experiments show that the emergence of
current-carrying magnetic field in the vicinity of the pore supplies
the magnetic twist needed for recurrent helical jet formation.
Title: Hot explosions in the cool atmosphere of the Sun
Authors: Peter, H.; Tian, H.; Curdt, W.; Schmit, D.; Innes, D.;
De Pontieu, B.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt, N.;
Tarbell, T. D.; Wuelser, J. P.; Martínez-Sykora, Juan; Kleint,
L.; Golub, L.; McKillop, S.; Reeves, K. K.; Saar, S.; Testa, P.;
Kankelborg, C.; Jaeggli, S.; Carlsson, M.; Hansteen, V.
Bibcode: 2014Sci...346C.315P
Altcode: 2014arXiv1410.5842P
The solar atmosphere was traditionally represented with a simple
one-dimensional model. Over the past few decades, this paradigm shifted
for the chromosphere and corona that constitute the outer atmosphere,
which is now considered a dynamic structured envelope. Recent
observations by the Interface Region Imaging Spectrograph (IRIS) reveal
that it is difficult to determine what is up and down, even in the cool
6000-kelvin photosphere just above the solar surface: This region hosts
pockets of hot plasma transiently heated to almost 100,000 kelvin. The
energy to heat and accelerate the plasma requires a considerable
fraction of the energy from flares, the largest solar disruptions. These
IRIS observations not only confirm that the photosphere is more complex
than conventionally thought, but also provide insight into the energy
conversion in the process of magnetic reconnection.
Title: The unresolved fine structure resolved: IRIS observations of
the solar transition region
Authors: Hansteen, V.; De Pontieu, B.; Carlsson, M.; Lemen, J.; Title,
A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser, J. P.; Pereira,
T. M. D.; De Luca, E. E.; Golub, L.; McKillop, S.; Reeves, K.; Saar,
S.; Testa, P.; Tian, H.; Kankelborg, C.; Jaeggli, S.; Kleint, L.;
Martínez-Sykora, J.
Bibcode: 2014Sci...346E.315H
Altcode: 2014arXiv1412.3611H
The heating of the outer solar atmospheric layers, i.e., the transition
region and corona, to high temperatures is a long-standing problem
in solar (and stellar) physics. Solutions have been hampered by an
incomplete understanding of the magnetically controlled structure of
these regions. The high spatial and temporal resolution observations
with the Interface Region Imaging Spectrograph (IRIS) at the solar
limb reveal a plethora of short, low-lying loops or loop segments
at transition-region temperatures that vary rapidly, on the time
scales of minutes. We argue that the existence of these loops solves
a long-standing observational mystery. At the same time, based on
comparison with numerical models, this detection sheds light on a
critical piece of the coronal heating puzzle.
Title: Evidence of nonthermal particles in coronal loops heated
impulsively by nanoflares
Authors: Testa, P.; De Pontieu, B.; Allred, J.; Carlsson, M.; Reale,
F.; Daw, A.; Hansteen, V.; Martinez-Sykora, J.; Liu, W.; DeLuca, E. E.;
Golub, L.; McKillop, S.; Reeves, K.; Saar, S.; Tian, H.; Lemen, J.;
Title, A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser, J. P.;
Kleint, L.; Kankelborg, C.; Jaeggli, S.
Bibcode: 2014Sci...346B.315T
Altcode: 2014arXiv1410.6130T
The physical processes causing energy exchange between the Sun’s
hot corona and its cool lower atmosphere remain poorly understood. The
chromosphere and transition region (TR) form an interface region between
the surface and the corona that is highly sensitive to the coronal
heating mechanism. High-resolution observations with the Interface
Region Imaging Spectrograph (IRIS) reveal rapid variability (~20 to
60 seconds) of intensity and velocity on small spatial scales (≲500
kilometers) at the footpoints of hot and dynamic coronal loops. The
observations are consistent with numerical simulations of heating by
beams of nonthermal electrons, which are generated in small impulsive
(≲30 seconds) heating events called “coronal nanoflares.” The
accelerated electrons deposit a sizable fraction of their energy
(≲1025 erg) in the chromosphere and TR. Our analysis
provides tight constraints on the properties of such electron beams
and new diagnostics for their presence in the nonflaring corona.
Title: Prevalence of small-scale jets from the networks of the solar
transition region and chromosphere
Authors: Tian, H.; DeLuca, E. E.; Cranmer, S. R.; De Pontieu, B.;
Peter, H.; Martínez-Sykora, J.; Golub, L.; McKillop, S.; Reeves,
K. K.; Miralles, M. P.; McCauley, P.; Saar, S.; Testa, P.; Weber,
M.; Murphy, N.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt, N.;
Tarbell, T. D.; Wuelser, J. P.; Kleint, L.; Kankelborg, C.; Jaeggli,
S.; Carlsson, M.; Hansteen, V.; McIntosh, S. W.
Bibcode: 2014Sci...346A.315T
Altcode: 2014arXiv1410.6143T
As the interface between the Sun’s photosphere and corona, the
chromosphere and transition region play a key role in the formation and
acceleration of the solar wind. Observations from the Interface Region
Imaging Spectrograph reveal the prevalence of intermittent small-scale
jets with speeds of 80 to 250 kilometers per second from the narrow
bright network lanes of this interface region. These jets have lifetimes
of 20 to 80 seconds and widths of ≤300 kilometers. They originate from
small-scale bright regions, often preceded by footpoint brightenings
and accompanied by transverse waves with amplitudes of ~20 kilometers
per second. Many jets reach temperatures of at least ~105
kelvin and constitute an important element of the transition region
structures. They are likely an intermittent but persistent source of
mass and energy for the solar wind.
Title: On the prevalence of small-scale twist in the solar
chromosphere and transition region
Authors: De Pontieu, B.; Rouppe van der Voort, L.; McIntosh, S. W.;
Pereira, T. M. D.; Carlsson, M.; Hansteen, V.; Skogsrud, H.; Lemen,
J.; Title, A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser,
J. P.; De Luca, E. E.; Golub, L.; McKillop, S.; Reeves, K.; Saar,
S.; Testa, P.; Tian, H.; Kankelborg, C.; Jaeggli, S.; Kleint, L.;
Martinez-Sykora, J.
Bibcode: 2014Sci...346D.315D
Altcode: 2014arXiv1410.6862D
The solar chromosphere and transition region (TR) form an interface
between the Sun’s surface and its hot outer atmosphere. There,
most of the nonthermal energy that powers the solar atmosphere
is transformed into heat, although the detailed mechanism remains
elusive. High-resolution (0.33-arc second) observations with NASA’s
Interface Region Imaging Spectrograph (IRIS) reveal a chromosphere
and TR that are replete with twist or torsional motions on sub-arc
second scales, occurring in active regions, quiet Sun regions, and
coronal holes alike. We coordinated observations with the Swedish
1-meter Solar Telescope (SST) to quantify these twisting motions and
their association with rapid heating to at least TR temperatures. This
view of the interface region provides insight into what heats the low
solar atmosphere.
Title: An Interface Region Imaging Spectrograph First View on Solar
Spicules
Authors: Pereira, T. M. D.; De Pontieu, B.; Carlsson, M.; Hansteen,
V.; Tarbell, T. D.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt,
N.; Wülser, J. P.; Martínez-Sykora, J.; Kleint, L.; Golub, L.;
McKillop, S.; Reeves, K. K.; Saar, S.; Testa, P.; Tian, H.; Jaeggli,
S.; Kankelborg, C.
Bibcode: 2014ApJ...792L..15P
Altcode: 2014arXiv1407.6360P
Solar spicules have eluded modelers and observers for decades. Since
the discovery of the more energetic type II, spicules have become
a heated topic but their contribution to the energy balance of the
low solar atmosphere remains unknown. Here we give a first glimpse of
what quiet-Sun spicules look like when observed with NASA's recently
launched Interface Region Imaging Spectrograph (IRIS). Using IRIS
spectra and filtergrams that sample the chromosphere and transition
region, we compare the properties and evolution of spicules as
observed in a coordinated campaign with Hinode and the Atmospheric
Imaging Assembly. Our IRIS observations allow us to follow the thermal
evolution of type II spicules and finally confirm that the fading
of Ca II H spicules appears to be caused by rapid heating to higher
temperatures. The IRIS spicules do not fade but continue evolving,
reaching higher and falling back down after 500-800 s. Ca II H type
II spicules are thus the initial stages of violent and hotter events
that mostly remain invisible in Ca II H filtergrams. These events
have very different properties from type I spicules, which show lower
velocities and no fading from chromospheric passbands. The IRIS spectra
of spicules show the same signature as their proposed disk counterparts,
reinforcing earlier work. Spectroheliograms from spectral rasters also
confirm that quiet-Sun spicules originate in bushes from the magnetic
network. Our results suggest that type II spicules are indeed the
site of vigorous heating (to at least transition region temperatures)
along extensive parts of the upward moving spicular plasma.
Title: The Interface Region Imaging Spectrograph (IRIS)
Authors: De Pontieu, B.; Title, A. M.; Lemen, J. R.; Kushner, G. D.;
Akin, D. J.; Allard, B.; Berger, T.; Boerner, P.; Cheung, M.; Chou,
C.; Drake, J. F.; Duncan, D. W.; Freeland, S.; Heyman, G. F.; Hoffman,
C.; Hurlburt, N. E.; Lindgren, R. W.; Mathur, D.; Rehse, R.; Sabolish,
D.; Seguin, R.; Schrijver, C. J.; Tarbell, T. D.; Wülser, J. -P.;
Wolfson, C. J.; Yanari, C.; Mudge, J.; Nguyen-Phuc, N.; Timmons,
R.; van Bezooijen, R.; Weingrod, I.; Brookner, R.; Butcher, G.;
Dougherty, B.; Eder, J.; Knagenhjelm, V.; Larsen, S.; Mansir, D.;
Phan, L.; Boyle, P.; Cheimets, P. N.; DeLuca, E. E.; Golub, L.;
Gates, R.; Hertz, E.; McKillop, S.; Park, S.; Perry, T.; Podgorski,
W. A.; Reeves, K.; Saar, S.; Testa, P.; Tian, H.; Weber, M.; Dunn, C.;
Eccles, S.; Jaeggli, S. A.; Kankelborg, C. C.; Mashburn, K.; Pust, N.;
Springer, L.; Carvalho, R.; Kleint, L.; Marmie, J.; Mazmanian, E.;
Pereira, T. M. D.; Sawyer, S.; Strong, J.; Worden, S. P.; Carlsson,
M.; Hansteen, V. H.; Leenaarts, J.; Wiesmann, M.; Aloise, J.; Chu,
K. -C.; Bush, R. I.; Scherrer, P. H.; Brekke, P.; Martinez-Sykora,
J.; Lites, B. W.; McIntosh, S. W.; Uitenbroek, H.; Okamoto, T. J.;
Gummin, M. A.; Auker, G.; Jerram, P.; Pool, P.; Waltham, N.
Bibcode: 2014SoPh..289.2733D
Altcode: 2014arXiv1401.2491D; 2014SoPh..tmp...25D
The Interface Region Imaging Spectrograph (IRIS) small explorer
spacecraft provides simultaneous spectra and images of the photosphere,
chromosphere, transition region, and corona with 0.33 - 0.4 arcsec
spatial resolution, two-second temporal resolution, and 1 km
s−1 velocity resolution over a field-of-view of up to
175 arcsec × 175 arcsec. IRIS was launched into a Sun-synchronous
orbit on 27 June 2013 using a Pegasus-XL rocket and consists of a
19-cm UV telescope that feeds a slit-based dual-bandpass imaging
spectrograph. IRIS obtains spectra in passbands from 1332 - 1358 Å,
1389 - 1407 Å, and 2783 - 2834 Å, including bright spectral lines
formed in the chromosphere (Mg II h 2803 Å and Mg II k 2796 Å) and
transition region (C II 1334/1335 Å and Si IV 1394/1403 Å). Slit-jaw
images in four different passbands (C II 1330, Si IV 1400, Mg II k
2796, and Mg II wing 2830 Å) can be taken simultaneously with spectral
rasters that sample regions up to 130 arcsec × 175 arcsec at a variety
of spatial samplings (from 0.33 arcsec and up). IRIS is sensitive to
emission from plasma at temperatures between 5000 K and 10 MK and will
advance our understanding of the flow of mass and energy through an
interface region, formed by the chromosphere and transition region,
between the photosphere and corona. This highly structured and dynamic
region not only acts as the conduit of all mass and energy feeding
into the corona and solar wind, it also requires an order of magnitude
more energy to heat than the corona and solar wind combined. The
IRIS investigation includes a strong numerical modeling component
based on advanced radiative-MHD codes to facilitate interpretation of
observations of this complex region. Approximately eight Gbytes of data
(after compression) are acquired by IRIS each day and made available
for unrestricted use within a few days of the observation.
Title: Detection of Supersonic Downflows and Associated Heating
Events in the Transition Region above Sunspots
Authors: Kleint, L.; Antolin, P.; Tian, H.; Judge, P.; Testa, P.;
De Pontieu, B.; Martínez-Sykora, J.; Reeves, K. K.; Wuelser, J. P.;
McKillop, S.; Saar, S.; Carlsson, M.; Boerner, P.; Hurlburt, N.; Lemen,
J.; Tarbell, T. D.; Title, A.; Golub, L.; Hansteen, V.; Jaeggli, S.;
Kankelborg, C.
Bibcode: 2014ApJ...789L..42K
Altcode: 2014arXiv1406.6816K
Interface Region Imaging Spectrograph data allow us to study the solar
transition region (TR) with an unprecedented spatial resolution of
0.''33. On 2013 August 30, we observed bursts of high Doppler shifts
suggesting strong supersonic downflows of up to 200 km s-1
and weaker, slightly slower upflows in the spectral lines Mg II h
and k, C II 1336, Si IV 1394 Å, and 1403 Å, that are correlated
with brightenings in the slitjaw images (SJIs). The bursty behavior
lasts throughout the 2 hr observation, with average burst durations
of about 20 s. The locations of these short-lived events appear to
be the umbral and penumbral footpoints of EUV loops. Fast apparent
downflows are observed along these loops in the SJIs and in the
Atmospheric Imaging Assembly, suggesting that the loops are thermally
unstable. We interpret the observations as cool material falling
from coronal heights, and especially coronal rain produced along the
thermally unstable loops, which leads to an increase of intensity
at the loop footpoints, probably indicating an increase of density
and temperature in the TR. The rain speeds are on the higher end of
previously reported speeds for this phenomenon, and possibly higher
than the free-fall velocity along the loops. On other observing days,
similar bright dots are sometimes aligned into ribbons, resembling
small flare ribbons. These observations provide a first insight into
small-scale heating events in sunspots in the TR.
Title: Using FLCT to Obtain Spectral Information From MOSES Data
Authors: Courrier, Hans; Kankelborg, Charles
Bibcode: 2014AAS...22421849C
Altcode:
The Multi-Order Solar EUV Spectrograph (MOSES) is a high cadence
slitless spectrograph that images in He II 304Å. The large field of
view (20’x10’) combined with the ability to quickly obtain images
containing both spectral and spatial information makes MOSES an ideal
platform for probing small scale, short duration flows resulting
from magnetic reconnection in the solar transition region. The ease
of obtaining co-temporal spectral and spatial data with a slitless
spectrograph is counterbalanced by increased difficulty required to
disentangling the information captured in the images. The Fourier
Local Correlation Tracking (FLCT) routine developed by Fischer and
Welch (2007) is developed as a technique for obtaining Doppler shifts
and line widths from small scale flows imaged by MOSES. Results are
reported utilizing this technique on simulated images and MOSES data.
Title: An Improved Periodogram Technique for 2-D PSF Equalization
Authors: Atwood, Shane; Kankelborg, Charles
Bibcode: 2014AAS...22412355A
Altcode:
The Multi-Order Extreme Ultraviolet Spectrograph (MOSES) forms
images of the transition region at HE II 30.4 in three spectral
orders. Subtle differences between these images encode line profile
information. However, differences in instrument point-spread function
(PSF) in the three orders lead to non-negligible systematic errors in
the retrieval of the line profiles. We describe an improved periodogram
technique for equalizing the PSFs, and provide numerical verification
of the technique's validity.
Title: MOSES Inversions using Multiresolution SMART
Authors: Rust, Thomas; Fox, Lewis; Kankelborg, Charles; Courrier,
Hans; Plovanic, Jacob
Bibcode: 2014AAS...22441406R
Altcode:
We present improvements to the SMART inversion algorithm for the MOSES
imaging spectrograph. MOSES, the Multi-Order Solar EUV Spectrograph,
is a slitless extreme ultraviolet spectrograph designed to measure
cotemporal narrowband spectra over a wide field of view via tomographic
inversion of images taken at three orders of a concave diffraction
grating. SMART, the Smooth Multiplicative Algebraic Reconstruction
Technique, relies on a global chi squared goodness of fit criterion,
which enables overfit and underfit regions to "balance out" when
judging fit quality. "Good" reconstructions show poor fits at some
positions and length scales. Here we take a multiresolution approach
to SMART, applying corrections to the reconstruction at positions and
scales where correction is warranted based on the noise. The result
is improved fit residuals that more closely resemble the expected
noise in the images. Within the multiresolution framework it is also
easy to include a regularized deconvolution of the instrument point
spread functions, which we do. Different point spread functions
among MOSES spectral orders results in spurious doppler shifts in
the reconstructions, most notable near bright compact emission. We
estimate the point spread funtions from the data. Deconvolution is done
using the Richardson-Lucy method, which is algorithmically similar to
SMART. Regularization results from only correcting the reconstruction
at positions and scales where correction is warranted based on the
noise. We expect the point spread function deconvolution to increase
signal to noise and reduce systematic error in MOSES reconstructions.
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: Testing Milne-Eddington Inversion Codes Against One-Dimensional
Model Atmospheres
Authors: Lastufka, Erica; Jaeggli, S. A.; Kankelborg, C.; Uitenbroek,
H.
Bibcode: 2013SPD....44..116L
Altcode:
Properties of solar vector magnetic fields can be determined by the
inversion of polarization spectra. It is therefore important to have
accurate inversion methods. Milne-Eddington inversions, used almost
exclusively in the photosphere, assume a thin, flat atmosphere and are
one of the most widely used inversion techniques. To investigate the
potential weaknesses of parameterizing a stratified atmosphere using
a single set of properties, we examine the consequences of using a
Milne-Eddington inversion to invert spectra of complex atmospheres. Han
Uitenbroek's Rybicki-Hummer radiative transfer and chemical equilibrium
code was used to generate a series of one-dimensional model atmospheres
with predetermined magnetic field configurations. Atmospheres at the
quiet Sun temperature contained magnetic fields with strengths up
3000 G and inclination and azimuthal angles from 0 to 180 degrees. We
examined the Stokes profiles of the Fe 15648.5 line, which with a
Landé g-factor of 3.0 is very sensitive to the magnetic field. Using a
simple Milne-Eddington inversion code, we examined the ranges in which
the code accurately parameterized the magnetic field. To investigate
the confidence intervals associated with the inverted parameters, we
used the BayesME code developed by Andres Asensio Ramos. We discuss
the key assumptions and limitations of a Milne-Eddington inversion.
Title: Fast Differential Emission Measure Inversion of Solar
Coronal Data
Authors: Plowman, Joseph; Kankelborg, Charles; Martens, Petrus
Bibcode: 2013ApJ...771....2P
Altcode: 2012arXiv1204.6306P
We present a fast method for reconstructing differential emission
measures (DEMs) using solar coronal data. The method consists of a
fast, simple regularized inversion in conjunction with an iteration
scheme for removal of residual negative emission measure. On average,
it computes over 1000 DEMs s-1 for a sample active region
observed by the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics
Observatory, and achieves reduced chi-squared of order unity with no
negative emission in all but a few test cases. The high performance of
this method is especially relevant in the context of AIA, which images
of order one million solar pixels per second. This paper describes the
method, analyzes its fidelity, compares its performance and results with
other DEM methods, and applies it to an active region and loop observed
by AIA and by the Extreme-ultraviolet Imaging Spectrometer on Hinode.
Title: MOSES Observations of Doppler Shifts in HeII λ304
Authors: Rust, Thomas; Kankelborg, C.
Bibcode: 2013SPD....44...38R
Altcode:
We report on Doppler shifts observed in HeII λ304 with the Multi-Order
Solar EUV Spectrograph (MOSES) sounding rocket. We use wavelet analysis
for automated identification and analysis of Doppler shifted emission
at different spatial scales, and track the temporal evolution over
time of flight.
Title: What Can FLCT and MOSES Tell Us About the Transition Region?
Authors: Courrier, Hans; Kankelborg, C.
Bibcode: 2013SPD....44...94C
Altcode:
Local correlation tracking methods are often used to measure
displacement, deformation, strain, and flow in varying fields of
study. The Fourier Local Correlation Tracking (FLCT) technique described
by Fisher & Welch (2007) is used to track flows on varying scales
observed by the Multi-Order Solar EUV Spectrograph (MOSES), a slitless
spectrograph imaging in narrowband He II 304 Å. The high spatial
resolution (0.6”) and wide field of view (10’ x 20’) combined
with the cotemporal spectral data obtained by the MOSES instrument
provides a unique range of transition region features and spectral
information that may be analyzed using FLCT techniques. Results are
reported using FLCT to evaluate small scale flows. The feasibility of
extending the technique to include larger scale motions and analysis
of spectral information is also considered.
Title: Numerical Verification of a 2-D PSF Equalization Technique
Authors: Atwood, Shane; Kankelborg, C.
Bibcode: 2013SPD....44...96A
Altcode:
The Multi-Order Extreme Ultraviolet Spectrograph (MOSES) forms
images of the transition region at HE II 30.4 in three spectral
orders. Subtle differences between these images encode line profile
information. However, differences in instrument point-spread function
(PSF) in the three orders lead to non-negligible systematic errors
in the retrieval of the line profiles. We describe a technique
for equalizing the PSFs, and provide numerical verification of the
technique's validity.
Title: Temperature, Density, and Heating Profiles of Coronal Loops
Authors: Plowman, Joseph; Martens, P. C.; Kankelborg, C.; Ritchie,
M.; Scott, J.; Sharma, R.
Bibcode: 2013SPD....4420106P
Altcode:
We show detailed results of a combined DEM and density-sensitive line
ratio analysis of coronal loops observed simultaneously by EIS and
AIA. The temperature and density profiles of the loop are compared
to and isolated from those of the surrounding material, and these
properties are fit to an analytic strand heating model developed by
Martens (2010). This research builds on our previously reported work
by analyzing a number of coronal loops (including one observed by the
Hi-C rocket), improved background subtraction and loop fitting. These
improvements allow us to place significant constraints on the heating
distribution of coronal loops.
Title: The Interface Region Imaging Spectrograph (IRIS)
Authors: De Pontieu, Bart; Title, A. M.; Lemen, J.; Wuelser, J.;
Tarbell, T. D.; Schrijver, C. J.; Golub, L.; Kankelborg, C.; Carlsson,
M.; Hansteen, V. H.; Worden, S.; IRIS Team
Bibcode: 2013SPD....44...03D
Altcode:
The solar chromosphere and transition region (TR) form a highly
structured and dynamic interface region between the photosphere and
the corona. This region not only acts as the conduit of all mass and
energy feeding into the corona and solar wind, it also requires an
order of magnitude more energy to heat than the corona. Nevertheless,
the chromosphere remains poorly understood, because of the complexity
of the required observational and analytical tools: the interface
region is highly complex with transitions from optically thick to
optically thin radiation, from pressure to magnetic field domination,
and large density and temperature contrasts on small spatial scales. The
Interface Region Imaging Spectrograph (IRIS) was selected for a NASA
SMEX mission in 2009 and is scheduled to launch on 26-June-2013 (with
first light scheduled for mid July). IRIS addresses critical questions:
(1) Which types of non-thermal energy dominate in the chromosphere and
beyond? (2) How does the chromosphere regulate mass and energy supply
to the corona and heliosphere? (3) How do magnetic flux and matter
rise through the lower atmosphere, and what role does flux emergence
play in flares and mass ejections? These questions are addressed with
a high-resolution near and far UV imaging spectrometer sensitive to
emission from plasma at temperatures between 5,000 K and 10 MK. IRIS
has a field-of-view of 120 arcsec, a spatial resolution of 0.4 arcsec,
and velocity resolution of 0.5 km/s. The IRIS investigation includes
a strong numerical modeling component based on advanced radiative MHD
codes to facilitate interpretation of observations. We describe the
IRIS instrumentation and numerical modeling, and present the plans for
observations, calibration and data distribution. We will highlight some
of the issues that IRIS observations can help resolve. More information
can be found at http://iris.lmsal.com
Title: National Student Solar Spectrograph Competition Overview
and Results
Authors: Des Jardins, Angela C.; Larimer, R.; Shaw, J. A.; Kankelborg,
C.; Palmer, C.; Key, J. S.; Nakagawa, W.; Springer, L.; Knighton,
W.; Repasky, K. S.; Pust, N. J.; Babbitt, W.; Jaeggli, S. A.; Hobish,
M. K.; Wilson, E. W.; Anderson, M.; Boger, J.; McCrady, N.; Naylor,
J.; Turcotte, S.; Lines, T.; Strobel, N.; Cooper, W.; Darke, R.; Head,
R.; Kimball, D.; Kissel, G.; Buck, K.; Lawrence, L.; Wragg, J.; Runyon,
C. J.; Spacher, P.; Dumitriu, I.; Nollenberg, J. G.; Estaban, R.
Bibcode: 2013SPD....44..160D
Altcode:
The yearly National Student Solar Spectrograph Competition (NSSSC)
is Montana Space Grant Consortium's Education and Public Outreach
(EP/O) Program for NASA's Interface Region Imaging Spectrograph (IRIS)
mission. The NSSSC is designed to give institutions with less aerospace
activity such as Minority Serving Institutions and Community Colleges
an opportunity for hands on real world research experience. The NSSSC
provides students from across the country the opportunity to work as
part of an undergraduate interdisciplinary team to design, build and
test a ground based solar spectrograph. Over the course of nine months,
teams come up with their own science goals and then build an instrument
to collect data in support of their goals. Teams then travel to Bozeman,
MT to demonstrate their instruments and present their results in a
competitive science fair environment. This poster will present the
2012-2013 competition results.Abstract (2,250 Maximum Characters):
The yearly National Student Solar Spectrograph Competition (NSSSC)
is Montana Space Grant Consortium's Education and Public Outreach
(EP/O) Program for NASA's Interface Region Imaging Spectrograph (IRIS)
mission. The NSSSC is designed to give institutions with less aerospace
activity such as Minority Serving Institutions and Community Colleges
an opportunity for hands on real world research experience. The NSSSC
provides students from across the country the opportunity to work as
part of an undergraduate interdisciplinary team to design, build and
test a ground based solar spectrograph. Over the course of nine months,
teams come up with their own science goals and then build an instrument
to collect data in support of their goals. Teams then travel to Bozeman,
MT to demonstrate their instruments and present their results in a
competitive science fair environment. This poster will present the
2012-2013 competition results.
Title: The Importance of Priors in Bayesian Reconstruction of Emission
Measure Distributions
Authors: Plowman, Joseph; Kankelborg, Charles
Bibcode: 2013enss.confE..96P
Altcode:
Bayesian methods such as MCMC are popular tools for reconstruction
of differential emission measures (DEMs) from coronal observations,
but the careful choice of prior probability distributions for these
reconstructions has received relatively little consideration. The choice
of prior is especially important for DEM reconstructions due to their
ill-posed nature; aspects of the reconstruction which are ill-posed
(i.e., not constrained by the data) will be determined exclusively by
the prior. We illustrate the effect of various choice of prior on the
reconstruction of example DEMs and outline some considerations for
choosing more physical priors. We also show results from application
of the MultiNest Bayesian inference tool to DEM reconstruction, and
compare with the results of the popular PINTofALE MCMC package.
Title: The Interface Region Imaging Spectrograph (IRIS)
Authors: De Pontieu, B.; Title, A. M.; Lemen, J. R.; Wuelser, J.;
Tarbell, T. D.; Schrijver, C.; Golub, L.; Kankelborg, C. C.; Hansteen,
V. H.; Carlsson, M.
Bibcode: 2012AGUFMSH33D2256D
Altcode:
The solar chromosphere and transition region (TR) form a highly
structured and dynamic interface region between the photosphere and
the corona. This region not only acts as the conduit of all mass and
energy feeding into the corona and solar wind, it also requires an
order of magnitude more energy to heat than the corona. Nevertheless,
the chromosphere remains poorly understood, because of the complexity
of the required observational and analytical tools: the interface
region is highly complex with transitions from optically thick to
optically thin radiation, from pressure to magnetic field domination,
and large density and temperature contrasts on small spatial scales. The
Interface Region Imaging Spectrograph (IRIS) was selected for a NASA
SMEX mission in 2009 and is scheduled to launch in early 2013. IRIS
addresses critical questions: (1) Which types of non-thermal energy
dominate in the chromosphere and beyond? (2) How does the chromosphere
regulate mass and energy supply to the corona and heliosphere? (3)
How do magnetic flux and matter rise through the lower atmosphere, and
what role does flux emergence play in flares and mass ejections? These
questions are addressed with a high-resolution near and far UV imaging
spectrometer sensitive to emission from plasma at temperatures between
5,000 K and 10 MK. IRIS has a field-of-view of 120 arcsec, a spatial
resolution of 0.4 arcsec, and velocity resolution of 0.5 km/s. The
IRIS investigation includes a strong numerical modeling component
based on advanced radiative MHD codes to facilitate interpretation of
observations. We will describe the IRIS instrumentation and numerical
modeling, and present the status of the IRIS observatory development. We
will highlight some of the issues that IRIS observations can help
resolve.
Title: The interface region imaging spectrograph for the IRIS Small
Explorer mission
Authors: Wülser, Jean-Pierre; Title, Alan M.; Lemen, James R.; De
Pontieu, Bart; Kankelborg, Charles C.; Tarbell, Theodore D.; Berger,
Thomas E.; Golub, Leon; Kushner, Gary D.; Chou, Catherine Y.; Weingrod,
Isaac; Holmes, Buck; Mudge, Jason; Podgorski, William A.
Bibcode: 2012SPIE.8443E..08W
Altcode:
The Interface Region Imaging Spectrograph (IRIS) is a NASA SMall
EXplorer mission scheduled for launch in January 2013. The primary goal
of IRIS is to understand how the solar atmosphere is energized. The
IRIS investigation combines advanced numerical modeling with a high
resolution UV imaging spectrograph. IRIS will obtain UV spectra
and images with high resolution in space (0.4 arcsec) and time (1s)
focused on the chromosphere and transition region of the Sun, a complex
interface region between the photosphere and corona. The IRIS instrument
uses a Cassegrain telescope to feed a dual spectrograph and slit-jaw
imager that operate in the 133-141 nm and 278-283 nm ranges. This paper
describes the instrument with emphasis on the imaging spectrograph,
and presents an initial performance assessment from ground test results.
Title: Experimental Flat-Field for Correction of XRT Contamination
Spots
Authors: McKenzie, D. E.; Fox, J. L.; Kankelborg, C.
Bibcode: 2012ASPC..454..453M
Altcode:
Beginning in mid-2007, the XRT images are marred by dark spots due
to beads of congealed contaminant. While programs are available for
improving the cosmetic appearance of the images, no method has yet
been demonstrated for a quantitative correction. We have employed a
flatfielding method developed for MSU's MOSES sounding rocket payload,
in an attempt to restore capabilities for quantitative photometry in the
affected pixels. Initial results are encouraging; characterization of
the uncertainties in the photometric correction are ongoing. We report
on the degree to which this flatfielding attempt has been successful.
Title: DEMs for EIS and AIA
Authors: Plowman, J.; Kankelborg, C.; Martens, P.; Ritchie, M.; Scott,
J.; Sharma, R.
Bibcode: 2012ASPC..456..131P
Altcode:
We present a method for constructing Differential Emission Measures
(DEMs) using data from solar imagers such as EIS and AIA. The method is
simple, and very fast (∼ 1 minute per full disk AIA image). We analyze
the fidelity of the method, and apply it to a coronal loop observed on
April 19, 2011. The method appears to give reasonable results, although
reconstructed DEMs can contain regions of moderately negative emission
measure (EM). Both EIS and AIA DEM reconstructions suggest that the loop
has a narrow temperature distribution centered at 1.2 MK, situated in a
diffuse background of broader temperature distribution centered at 3 MK.
Title: Simultaneous Imaging and Spectroscopy by Inversion of MOSES
Sounding Rocket Data
Authors: Kankelborg, Charles; Atwood, S.; Courrier, H.; Plovanic,
J.; Rust, T.
Bibcode: 2012AAS...22012401K
Altcode:
The Multi-Order Solar EUV Spectrograph (MOSES) forms 304 Å EUV images
at three spectral orders from an objective multilayer grating. The
images encode spatial and spectral data over a 20 x 10 arc minute field
of view. We describe an inversion algorithm and present spectra derived
thereby from data obtained during the 2006 flight. We gratefully
acknowledge the support of the NASA Heliophysics LCAS program.
Title: Temperature And Density Analysis Of A Coronal Loop Observed
By Eis And Aia
Authors: Plowman, Joseph; Martens, P.; Kankelborg, C.; Ritchie, M.;
Scott, J.; Sharma, R.
Bibcode: 2012AAS...22030905P
Altcode:
We present a combined DEM and density-sensitive line ratio analysis of
a loop observed simultaneously by EIS and AIA. The DEMs are calculated
using a fast new method which we also describe. The temperature and
density profiles of the loop are compared to and isolated from those of
the surrounding material, and these properties are fit to an analytic
strand heating model developed by Martens (2010). Supported by an AIA
subcontract to Montana State University.
Title: Radiative Transfer and Absorbing Structures in the Transition
Region
Authors: Plovanic, Jacob; Kankelborg, C. C.
Bibcode: 2012AAS...22020308P
Altcode:
A fully satisfactory explanation for the anomalous He II 304 Å
intensity in the solar transition region has yet to be offered. As an
extension of previous work, we use a full radiative transfer code to
build a more consistent model of the transition region that allows
the He II line to form with low filling factor and low opacity. Our
results are constrained by the quiet sun center-to-limb profile of He
II 304 Å obtained from the MOSES sounding rocket mission and by AIA
full-disk data.
Title: Theoretical Performance of a Multi-Order Spectral Imager for
the Solar Transition Region
Authors: Courrier, Hans; Kankelborg, C.
Bibcode: 2012AAS...22020313C
Altcode:
The 2006 sounding rocket launch of the Multi-Order Solar EUV
Spectrograph (MOSES) provided simultaneous imaging and spectroscopy
of the solar atmosphere through the use of 3 projections provided by
a concave reflection grating. A new, more flexible instrument design
has been proposed that allows the use of 4-8+ projections to obtain
higher moments of the spectral line profile in a configuration that
also provides increased sensitivity and improved manufacturability. The
optical performance of this instrument is investigated and optimized
with respect to grating design parameters, and its scientific utility
is discussed.
Title: Fast DEMs for EIS and AIA
Authors: Plowman, Joseph; Kankelborg, Charles; Martens, Petrus;
Ritchie, Miriam; Scott, Jason; Sharma, Rahul
Bibcode: 2012decs.confE..77P
Altcode:
We present a method for constructing Differential Emission Measures
(DEMs) using data from solar imagers such as EIS and AIA. In its
basic form, the method is very fast (approximately one minute per
full disk AIA image), although the DEMs obtained can contain regions
of moderately negative emission measure (EM). We demonstrate an
extension of the method which removes regions of negative EM while
closely matching the data. The fidelity of the method is analyzed,
its results are compared to those of the PINTofALE MCMC DEM algorithm,
and it is applied to a coronal loop observed on April 19, 2011.
Title: Obtaining Line Intensities and Profiles From MOSES Sounding
Rocket Data
Authors: Kankelborg, Charles C.; Atwood, Shane M.; Courrier, Hans T.;
Plovanic, Jacob T.; Rust, Thomas L.
Bibcode: 2012decs.confE..78K
Altcode:
The Multi-Order Solar EUV Spectrograph (MOSES) obtains images dispersed
at three spectral orders from an objective grating, with the goal of
reconstructing EUV spectra of He II (30.38 nm) and Si XI (30.33 nm)
simultaneously over a large 2D field of view. We present preliminary
results from a new data inversion code, estimating the spectrum in
every pixel. This capability opens a new window on the solar atmosphere.
Title: Non-Stationary Deconvolution for the IRIS NUV Slit-Jaw Imager
Authors: Jaeggli, Sarah A.; Kankelborg, Charles C.; IRIS Team
Bibcode: 2012decs.confE..49J
Altcode:
High spatial resolution context imaging is essential to linking spatial
structures with spectral signatures in the chromosphere, a critical
part of the science requirements for IRIS (Interface Region Imaging
Spectrograph). Measurements of the optical figure of the Solc filter
indicate that the NUV slit-jaw imager on IRIS will have a somewhat
broader PSF than the other instrument channels. We have developed an
advanced deconvolution technique which combines measured PSFs sampled
over the image plane to achieve the best correction for each pixel. We
have conducted an analysis of this technique on synthetic data, and
we assess the quality of the resulting images containing a variety of
simulated effects, including cosmic ray hits, photon counting noise,
discrete energetic solar events (flares), and saturation and overflow
artifacts.
Title: The Interface Region Imaging Spectrograph (IRIS) NASA SMEX
Authors: Lemen, James; Title, A.; De Pontieu, B.; Schrijver, C.;
Tarbell, T.; Wuelser, J.; Golub, L.; Kankelborg, C.
Bibcode: 2011SPD....42.1512L
Altcode: 2011BAAS..43S.1512L
The solar chromosphere and transition region (TR) is highly structured,
dynamic, and intimately connected to the corona. It requires more
than ten times the energy required to heat the corona, and yet it
has received far less interest because of the complexity of the
required observational and analytical tools. In the TR the density
drops by six orders of magnitude and the temperature increases by
three orders of magnitude. Hinode observations reveal the importance
the magnetic field has on this region of the solar atmosphere that
acts as the interface between the photosphere and the corona. The
Interface Region Imaging Spectrograph (IRIS) was selected for a NASA
SMEX mission in 2009 and is scheduled to launch in December 2012. IRIS
addresses critical questions in order to understand the flow of energy
and mass through the chromosphere and TR, namely: (1) Which types of
non-thermal energy dominate in the chromosphere and beyond? (2) How
does the chromosphere regulate mass and energy supply to the corona
and heliosphere? (3) How do magnetic flux and matter rise through the
lower atmosphere, and what roles dos flux emergence play in flares and
mass ejections? These questions are addressed with a high-resolution
imaging spectrometer that observes Near- and Far-VU emissions that
are formed at temperatures between 5,000K and 1.5 x 106
K. IRIS has a field-of-view of 120 arcsec, a spatial resolution
of 0.4 arcsec, and velocity resolution of 0.5 km/s. Members of the
IRIS investigation team are developing advanced radiative MHD codes
to facilitate comparison with and interpretation of observations. We
present the status of the IRIS observatory development, which completed
its Critical Design Review in December 2010.
Title: Explosive Event Rates in He II from MOSES Data
Authors: Fox, Lewis; Kankelborg, C.
Bibcode: 2011SPD....42.0307F
Altcode: 2011BAAS..43S.0307F
Explosive events have been observed for years in many transition
region lines across temperatures from 20,000 - 250,000 K. They are
particularly well-known in lines of C IV (the 1550A doublet) and Si
IV (1393A) at temperatures of 100,000 K. They are characterized by
large non-thermal doppler broadening of the order of 100 km/s, are
usually small 2000 km, and short-lived, 60 - 90 sec. Event rates have
been measured on the order of 600 events per second over the visible
surface of the Sun. In Fox, Kankelborg, and Thomas (2010) we showed
the discovery of the first explosive event reported in the literature
in the He II 304A line, at a temperature of 80,000 K (Andretta et. al.,
2000), using data from the Multi-Order Solar EUV Spectrograph sounding
rocket instrument. Explosive events in He II lines are seldom reported
in the literature, and no event rates are given. We present here the
first estimate of He II explosive event rates and compare to event
rates for explosive events in other ions. This work supported by the
NASA LCAS program, grant NAG5-10997 and NNX-07AG6G.
Title: Blue Shifted Jets in the Transition Region
Authors: Rust, Thomas; Kankelborg, C. C.
Bibcode: 2011SPD....42.1740R
Altcode: 2011BAAS..43S.1740R
We report on blue shifted jets observed at 10 s cadence with the MOSES
sounding rocket (first flight February 2006). MOSES (Multi-Order
Solar EUV Spectrograph) employs multicoated diffractive optics to
obtain simultaneous images and spectra of He II emission in the solar
transition region.
Title: An Advanced EUV Multi-Order Spectral Imager For The Solar
Atmosphere
Authors: Kankelborg, Charles; Chen, C.; Lokken, P.
Bibcode: 2011SPD....42.1514K
Altcode: 2011BAAS..43S.1514K
We describe an EUV imager capable of measuring spectral line profiles
at high spatial resolution over a wide field of view in a single
snapshot. The instrument follows in the footsteps of the Multi-Order
Solar EUV Specrtrograph (MOSES) sounding rocket instrument, and could
fly simultaneously within the same experiment section. The design
provides higher moments of the spectral line profile and higher
sensitivity that MOSES, but with a more compact optical configuration.
Title: Fine Structure and Optical Depth in the Solar Transition Region
Authors: Plovanic, Jacob; Kankelborg, C. C.; Williamson, K.
Bibcode: 2011SPD....42.1739P
Altcode: 2011BAAS..43S.1739P
Unresolved fine structure in the solar transition region (TR) has
long been inferred from measurements of density-sensitive line pairs
showing low filling factor (< 0.01). Low filling factor models for
the structure of the He II source region, however, have not been well
studied. We propose a highly structured model of the lower atmosphere in
which He II is formed at low filling factors, leading to high emission
measure and an optically thin He II line. This transparent TR material
is juxtaposed with absorbing chromospheric structures, leading to the
nearly uniform center to limb behavior of the He II line as observed.
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: A Transition Region Explosive Event Observed in He II with
the MOSES Sounding Rocket
Authors: Fox, J. Lewis; Kankelborg, Charles C.; Thomas, Roger J.
Bibcode: 2010ApJ...719.1132F
Altcode:
Transition region explosive events (EEs) have been observed with slit
spectrographs since at least 1975, most commonly in lines of C IV
(1548 Å, 1550 Å) and Si IV (1393 Å, 1402 Å). We report what we
believe to be the first observation of a transition region EE in
He II 304 Å. With the Multi-Order Solar EUV Spectrograph (MOSES)
sounding rocket, a novel slitless imaging spectrograph, we are able
to see the spatial structure of the event. We observe a bright core
expelling two jets that are distinctly non-collinear, in directions
that are not anti-parallel. The jets have sky-plane velocities of
order 75 km s-1 and line-of-sight velocities of +75 km
s-1 (blue) and -30 km s-1 (red). The core is a
region of high non-thermal Doppler broadening, characteristic of EEs,
with maximal broadening 380 km s-1 FWHM. It is possible
to resolve the core broadening into red and blue line-of-sight
components of maximum Doppler velocities +160 km s-1 and
-220 km s-1. The event lasts more than 150 s. Its properties
correspond to the larger, long-lived, and more energetic EEs observed
in other wavelengths.
Title: Coronal Tomography With STEREO and TRACE
Authors: Plumberg, Christopher; Kankelborg, C. C.
Bibcode: 2010AAS...21640722P
Altcode:
We demonstrate a simple, yet powerful, algorithm for computed
tomography using both synthetic and solar data. A minimum of three
perspectives are required. We obtain these from STEREO/EUVI plus
TRACE. Our treatment includes subtraction of nonuniform backgrounds
that depend on the viewing angle. A preliminary three-dimensional
tomographic reconstruction of the low corona with STEREO and TRACE
images is performed with an active region observed on October 15, 2008.
Title: SMART Analysis Of A He II Explosive Event Observed With MOSES
Authors: Fox, Lewis; Kankelborg, C. C.; Thomas, R. J.
Bibcode: 2010AAS...21630501F
Altcode:
Analysis of data from the MOSES (Multi-Order Solar EUV Spectrograph)
sounding rocket has shown a Transition Region Explosive Event (TREE)
in He II 304 Å with an unusual structure that defies conventional
models of explosive events; the outflow jets are not collinear or
anti-parallel. Results from our preliminary analysis of this event,
performed using a tomographic parallax technique but without full
inversions, are reported in a paper submitted to the Astrophysical
Journal, presently under revision. Early results of inversions using
the Smoothed Multiplicative Algebraic Reconstruction Technique
(SMART), reported at SPD 2009, showed qualitative agreement with
parallax analysis results but disagreement in magnitude of doppler
velocities. We address this discrepancy with further refinement of the
inversion technique and show how the discrepancy in velocity magnitude
can be understood.
Title: The Interface Region Imaging Spectrograph (IRIS) Small Explorer
Authors: de Pontieu, B.; Title, A. M.; Schryver, C. J.; Lemen, J. R.;
Golub, L.; Kankelborg, C. C.; Carlsson, M.
Bibcode: 2009AGUFMSH33B1499D
Altcode:
The Interface Region Imaging Spectrograph (IRIS) was recently selected
as a small explorer mission by NASA. The primary goal of IRIS is to
understand how the solar atmosphere is energized. The IRIS investigation
combines advanced numerical modeling with a high resolution 20 cm UV
imaging spectrograph that will obtain spectra covering temperatures
from 4,500 to 10 MK in three wavelength ranges (1332-1358 Angstrom,
1390-1406 Angstrom and 2785-2835 Angstrom) and simultaneous images
covering temperatures from 4,500 K to 65,000 K. IRIS will obtain UV
spectra and images with high resolution in space (1/3 arcsec) and time
(1s) focused on the chromosphere and transition region of the Sun, a
complex dynamic interface region between the photosphere and corona. In
this region, all but a few percent of the non-radiative energy leaving
the Sun is converted into heat and radiation. IRIS fills a crucial gap
in our ability to advance Sun-Earth connection studies by tracing the
flow of energy and plasma through this foundation of the corona and
heliosphere. The IRIS investigation is led by PI Alan Title (LMSAL)
with major participation by the Harvard Smithsonian Astrophysical
Observatory, Montana State University, NASA Ames Research Center,
Stanford University and the University of Oslo (Norway). IRIS is
scheduled for launch in late 2012, and will have a nominal two year
mission lifetime.
Title: Coronal Loop Expansion Properties Explained Using Separators
Authors: Plowman, Joseph E.; Kankelborg, Charles C.; Longcope, Dana W.
Bibcode: 2009ApJ...706..108P
Altcode: 2009arXiv0903.3430P
One puzzling observed property of coronal loops is that they are of
roughly constant thickness along their length. Various studies have
found no consistent pattern of width variation along the length of
loops observed by TRACE and SOHO. This is at odds with expectations
of magnetic flux tube expansion properties, which suggests that
loops are widest at their tops, and significantly narrower at their
footpoints. Coronal loops correspond to areas of the solar corona
which have been preferentially heated by some process, so this
observed property might be connected to the mechanisms that heat
the corona. One means of energy deposition is magnetic reconnection,
which occurs along field lines called separators. These field lines
begin and end on magnetic null points, and loops forming near them can
therefore be relatively wide at their bases. Thus, coronal energization
by magnetic reconnection may replicate the puzzling expansion properties
observed in coronal loops. We present results of a Monte Carlo survey
of separator field line expansion properties, comparing them to the
observed properties of coronal loops.
Title: First Inversions of MOSES Slit-less Spectroscopy Data
Authors: Fox, Lewis; Kankelborg, C. C.
Bibcode: 2009SPD....40.3304F
Altcode:
The Multi-Order Solar EUV Spectrograph sounding rocket payload
launched Feb. 8, 2006, obtaining data in three spectral orders at a
wavelength of 304Å. Direct analyses of the data have been performed
and reported previously, showing the existence of outflow jets and
explosive events in our images. To realize the full potential of
slit-less imaging spectroscopy, however, requires inversion of the
three-order imaging data to produce a hyper-spectral cube, containing
a spectrum at every pixel. We have previously performed and reported
on inversion techniques applied to synthetic data. We now show, for
the first time, trial inversions of real MOSES data using the Smoothed
Multiplicative Algebraic Reconstruction Technique (SMART). We use the
resulting hyper-spectral cubes to produce the first MOSES dopplergrams.
Title: MOSES Radiometric Calibration
Authors: Rust, Thomas; Fox, J. L.; Kankelborg, C. C.; Thomas, R. J.
Bibcode: 2009SPD....40.1808R
Altcode:
We present analysis of radiometric calibration data for MOSES, the
Multi-Order Solar EUV Spectrograph. MOSES is an EUV imaging spectrograph
which uses a spherical grating to feed three rear illuminated CCDs, one
for each of the m = 0 and m = ±1 spectral orders of the grating. MOSES
was calibrated end-to-end at the EUV radiometric calibration facility
at Rutherford Appleton Laboratory, using a well characterized hollow
cathode source traceable to the BESSY synchrotron. We analyze these data
and present the end-to-end instrument response (DN per incident photon)
for each of MOSES three CCD channels. This work was supported in part
by a grant from the NASA Solar and Heliospheric Physics LCAS program.
Title: Reconnectionless CME Eruption: Putting the Aly-Sturrock
Conjecture to Rest
Authors: Rachmeler, L. A.; DeForest, C. E.; Kankelborg, C. C.
Bibcode: 2009ApJ...693.1431R
Altcode: 2008arXiv0812.3199R
We demonstrate that magnetic reconnection is not necessary to initiate
fast Coronal mass ejections (CMEs). The Aly-Sturrock conjecture
states that the magnetic energy of a given force-free boundary field
is maximized when the field is open. This is problematic for CME
initiation because it leaves little or no magnetic energy to drive the
eruption, unless reconnection is present to allow some of the flux to
escape without opening. Thus, it has been thought that reconnection
must be present to initiate CMEs. This theory has not been subject to
rigorous numerical testing because conventional magnetohydrodynamics
(MHD) numerical models contain numerical diffusion, which introduces
uncontrolled numerical reconnection. We use a quasi-Lagrangian
simulation technique to run the first controlled experiments of CME
initiation in the complete lack of reconnection. We find that a flux
rope confined by an arcade, when twisted beyond a critical amount,
can escape to an open state, allowing some of the surrounding arcade
to shrink, and releasing magnetic energy from the global field. This
mechanism includes a true ideal MHD instability. We conclude that
reconnection is not a necessary trigger for fast CME eruptions.
Title: Coronal Tomography
Authors: Kankelborg, Charles C.
Bibcode: 2008arXiv0806.4803K
Altcode:
A simple, yet powerful, algorithm for computed tomography of the
solar corona is presented and demonstrated using synthetic EUV data. A
minimum of three perspectives are required. These may be obtained from
STEREO/EUVI plus an instrument near Earth, e.g. TRACE or SOHO/EIT.
Title: Coronal Tomography
Authors: Kankelborg, C. C.
Bibcode: 2008AGUSMSP31D..02K
Altcode:
A simple, yet powerful, algorithm for computed tomography of the solar
corona is demonstrated using synthetic EUV data. A minimum of three
perspectives are required. These may be obtained from STEREO/EUVI plus
an instrument near Earth, e.g. TRACE or SOHO/EIT.
Title: The effect of reconnection on a confined flux rope
Authors: Rachmeler, L. A.; Deforest, C. E.; Kankelborg, C. C.
Bibcode: 2007AGUFMSH31A0233R
Altcode:
Coronal mass ejections are among the most energetic events in our
solar system, but their initiation mechanisms are still not well
known. One possibility is loss of stability of a twisted flux rope
confined by an overlying arcade. We present here a continuation of
our research studying the role of reconnection on this system. We
examine the relationship between critical-current reconnection and
stability of a simple confined flux rope in simulations free from
numerical reconnection. The current work focuses on imposing various
reconnection rates on the system to determine how reconnection effects
the stability of the confined rope.
Title: Three Dimensional Structure and Time Evolution of a Transition
Region Explosive Event Observed in He II
Authors: Fox, J. L.; Kankelborg, C. C.; Thomas, R. J.; Longcope, D.
Bibcode: 2007AGUFMSH22A0840F
Altcode:
Transition Region Explosive Events (TREEs) have been observed with
slit spectrographs since at least 1975, most commonly in lines of C IV
(1548A,1550A) and Si IV (1393A, 1402A). We report what we believe to be
the first observation of a TREE in He II 304A. With the MOSES sounding
rocket, a novel type of imaging spectrograph, we are able to see the
spatial and spectral structure of the event. It consists of a bright
core expelling two jets, oppositely directed but not collinear, which
curve away from the axis of the core. The jets have both line-of-sight
and sky-plane motion. The core is a region of high non-thermal doppler
broadening, characteristic of TREEs. It is possible to resolve the
core broadening into red and blue line-of-sight components. MOSES
captured approximately 150 sec of time evolution before the rocket
flight ended. We see the beginning (core activation) and middle (jet
ejection), but not the end. It is clear from our data-set that TREEs
in He II 304A are much less common than observed in other wavelengths.
Title: Fluxon Modeling of Eruptive Events With and Without
Reconnection
Authors: DeForest, Craig; Rachmeler, L.; Davey, A.; Kankelborg, C.
Bibcode: 2007AAS...210.5305D
Altcode: 2007BAAS...39..165D
Fluxon MHD models represent the coronal magnetic field as a "skeleton"
of discretized field lines. This quasi-Lagrangian approach eliminates
numerical resistivity and allows 3-D time-dependent plasma simulation in
a desktop workstation.Using our fluxon code, FLUX, we have demonstrated
that ideal MHD instabilities can drive fast eruptive events even in the
complete absence of magnetic reconnection. The mechanism ("herniation")
is probably not the main driver of fast CMEs but may be applicable to
microjets, macrospicules, or other small scale events where vortical
flows are present in the solar atmosphere. In this presentation, we use
time-dependent simulations to demonstrate energy release in several
idealized plasma systems with and without magnetic reconnection.This
work was funded by NASA's LWS and SHP-SR&T programs.
Title: Three Dimensional Structure Of A Complex Bipolar Jet:
Transition Region Imaging-spectroscopy With MOSES
Authors: Fox, Lewis; Kankelborg, C. C.; Longcope, D.
Bibcode: 2007AAS...210.9501F
Altcode: 2007BAAS...39..223F
We report on an interesting transient brightening observed in He II 304
Å above a flux-canceling magnetic bipole during the MOSES (Multi-Order
Solar EUV Spectrograph) sounding rocket flight, Feb. 8, 2006. The event
resembles a bipolar jet and has characteristics of a transition region
explosive event, but it is not a simple, linear structure at some angle
to the line-of-sight. The jets curve away from the axis of a compact,
bright core, and are not collinear. We observe transverse sky-plane
motions and infer line-of-sight doppler shifts along the length of
the jets, as well as non-thermal line broadening in the bright core,
demonstrating the utility of simultaneous imaging-spectroscopy provided
by MOSES. This work is supported by NASA LCAS and the Montana Space
Grant Consortium.
Title: Low Cost X-ray Optics for Studying StellarDynamo Cycles
Authors: Rust, Thomas; Acton, L.; Kankelborg, C.; Martens, P.
Bibcode: 2007AAS...210.2302R
Altcode: 2007BAAS...39..128R
Comparison of measured coronal X-ray variability over stellar magnetic
dynamo cycles with theoretical models will yield new understanding
of the solar magnetic dynamo cycle. We present the results of a study
comparing surface roughnesses of three candidate materials for use as
glancing angle X-ray reflectors. This work is part of a continuing
effort by MSU's Solar Physics Group and Space Science Engineering
Laboratory (SSEL) to design and build large aperture, low cost X-ray
optics for space experiments. The MSU proposed SADE (Starspot and
Dynamo Explorer) instrument would use arrays of nested Kirkpatrick-Baez
reflectors, called STAX (Sade Telescope Array for X-rays), for long
term measurements of soft X-ray fluxes from about a hundred nearby
solar-type stars. The advantage of the STAX design is that it uses
"off the shelf" materials bent to shape, which is far cheaper and
easier to manufacture than the polished cylindrical optics typically
used in X-ray telescopes. In order to determine whether off the shelf
materials satisfy the stringent surface smoothness requirements for
glancing angle reflectors, we have undertaken an atomic force microscope
investigation of three candidate materials. In addition, we compare
the measured and theoretical diffraction pattern of our existing STAX
test article. This comparison will provide insight into the suitability
of the candidate material, as well as the feasibility of maintaining
proper shape over the surface of the reflector by constraining the
edges in precision machined grooves. This work is supported by a grant
from MSU/NASA EPSCOR.
Title: The Sensitivity of Hybrid Differential Stereoscopy for
Spectral Imaging
Authors: DeForest, Craig E.; Kankelborg, Charles C.
Bibcode: 2007arXiv0704.2058D
Altcode: 2007arXiv0704.2058K
Stereoscopic spectral imaging is an observing technique that affords
rapid acquisition of limited spectral information over an entire image
plane simultaneously. Light from a telescope is dispersed into multiple
spectral orders, which are imaged separately, and two or more of the
dispersed images are combined using an analogy between the (x,y,\lambda)
spectral data space and conventional (x,y,z) three-space. Because
no photons are deliberately destroyed during image acquisition, the
technique is much more photon-efficient in some observing regimes than
existing techniques such as scanned-filtergraph or scanned-slit spectral
imaging. Hybrid differential stereoscopy, which uses a combination of
conventional cross-correlation stereoscopy and linear approximation
theory to extract the central wavelength of a spectral line, has been
used to produce solar Stokes-V (line-of-sight) magnetograms in the
617.34 nm Fe I line, and more sophisticated inversion techniques are
currently being used to derive Doppler and line separation data from
EUV images of the solar corona collected in the neighboring lines
of He-II and Si-XI at 30.4 nm. In this paper we develop an analytic
a priori treatment of noise in the line shift signal derived from
hybrid differential stereoscopy. We use the analysis to estimate
the noise level and measurement precision in a high resolution solar
magnetograph based on stereoscopic spectral imaging, compare those
estimates to a test observation made in 2003, and discuss implications
for future instruments.
Title: Fluxon modeling of low-beta plasmas
Authors: Deforest, C. E.; Kankelborg, C. C.
Bibcode: 2007JASTP..69..116D
Altcode: 2007JATP...69..116D; 2006astro.ph..9508D
We have developed a new, quasi-Lagrangian approach for numerical
modeling of magnetohydrodynamics in low to moderate β plasmas such
as the solar corona. We introduce the concept of a “fluxon”, a
discretized field line. Fluxon models represent the magnetic field as
a skeleton of such discrete field lines, and interpolate field values
from the geometry of the skeleton where needed, reversing the usual
direction of the field line transform. The fluxon skeleton forms
the grid for a collection of 1-D Eulerian models of plasma along
individual flux tubes. Fluxon models have no numerical resistivity,
because they preserve topology explicitly. Our prototype code, FLUX,
is currently able to find 3-D nonlinear force-free field solutions with
a specified field topology, and work is ongoing to validate and extend
the code to full magnetohydrodynamics. FLUX has significant scaling
advantages over conventional models: for “magnetic carpet” models,
with photospheric line-tied boundary conditions, FLUX simulations
scale in complexity like a conventional 2-D grid although the full
3-D field is represented. The code is free software and is available
online. In this current paper we introduce fluxons and our prototype
code, and describe the course of future work with the code.
Title: Fluxon Modeling of Active Region Evolution
Authors: Deforest, C. E.; Kankelborg, C. C.; Davey, A. R.; Rachmeler,
L.
Bibcode: 2006AGUFMSH31B..07D
Altcode:
We present current results and status on fluxon modeling of free
energy buildup and release in active regions. Our publicly available
code, FLUX, has the unique ability to track magnetic energy buildup
with a truly constrained topology in evolving, nonlinear force-free
conditions. Recent work includes validation of the model against Low
&Lou force-free field solutions, initial evolution studies of
idealized active regions, and inclusion of locally parameterized
reconnection into the model. FLUX is uniquely able to simulate
complete active regions in 3-D on a single workstation; we estimate
that a parallelized fluxon model, together with computer vision code
to ingest solar data, could run faster than real time on a cluster
of \textasciitilde 30 CPUs and hence provide a true predictive space
weather model in the style of predictive simulations of terrestrial
weather.
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: First Results From the MOSES Rocket Flight
Authors: Kankelborg, Charles; Fox, J. L.; Thomas, R. J.
Bibcode: 2006SPD....37.3704K
Altcode:
The Multi-Order Solar EUV Spectrograph (MOSES) is a first-of-its-kind
simultaneous imaging spectrograph. We report the first results from
a successful flight on February 8, 2006.
Title: Constraining Spectrum Reconstruction for the MOSES Rocket
Intrument
Authors: Fox, Lewis; Kankelborg, C. C.
Bibcode: 2006SPD....37.0609F
Altcode: 2006BAAS...38Q.227F
The Multi-Order Solar EUV Spectrograph (MOSES) sounding rocket,
launched Feb. 8, 2006, is a first-of-its-kind simultaneous imaging
spectrograph. The reconstruction of EUV spectra from our data requires
a constraint on the FOV integrated spectrum. There are several ways to
impose that constraint, requiring varying amounts of information. The
aim of this work is to discover how best to estimate the integrated
spectrum and to apply this constraint in reconstructing spectral image
cubes.This work is supported by NASA LCAS Grant NAG5-10997 and NASA
GSRP Fellowship NGT5-50471.
Title: Quantifying The Relationship Between Reconnection Rate And
Energy Release In A Survey Of Coronal Bright Points
Authors: Malanushenko, Anna V.; Longcope, D.; Aver, E.; Kankelborg, C.
Bibcode: 2006SPD....37.1001M
Altcode: 2006BAAS...38Q.237M
This is an observational study of coronal bright points aimed at
quantifying the relationship between reconnection rate and dissipated
power. We assemble surveys of 733 bright from archival SOHO data. Bright
points are found in two channels of EIT (EUV Imaging Telescope)
data. We match these features to magnetic bipoles found in photospheric
magnetic field observations of MDI. From the MDI magnetograms we extract
measurements of each quantity relevant to simple three-dimensional
reconnection model including the relative velocities of the magnetic
poles. The study reveals temporal and spatial properties of X-ray bright
points and compares them to the simple models of spatial distribution
over the disk. The temporal evolution of the poles is used to test the
hypothesis that coronal heating is due to magnetic reconnection and
furthermore to quantify the relationship between reconnection rate and
heating power.This work was supported by NASA under grant NAG5-10489.
Title: Narrow-band EUV multilayer coating for the MOSES sounding
rocket
Authors: Owens, Scott M.; Gum, Jeffery S.; Tarrio, Charles; Grantham,
Steven; Dvorak, Joseph; Kjornrattanawanich, Benjawan; Keski-Kuha,
Ritva; Thomas, Roger J.; Kankelborg, Charles C.
Bibcode: 2005SPIE.5900....5O
Altcode:
The Multi-order Solar EUV Spectrograph (MOSES) is a slitless
spectrograph designed to study solar He II emission at 303.8 Å (1 Å =
0.1 nm), to be launched on a sounding rocket payload. One difference
between MOSES and other slitless spectrographs is that the images are
recorded simultaneously at three spectral orders, m = -1, 0, +1. Another
is the addition of a narrow-band multilayer coating on both the grating
and the fold flat, which will reject out-of-band lines that normally
contaminate the image of a slitless instrument. The primary metrics
for the coating were high peak reflectivity and suppression of Fe XV
and XVI emission lines at 284 Å and 335 Å, respectively. We chose
B4C/Mg2Si for our material combination since
it provides excellent peak reflectivity and rejection of out-of-band
wavelengths. Measurements of witness flats at NIST indicate the peak
reflectivity at 303.8 is 39.0% for a 15 bilayer stack, while suppression
ranges from 7.5x to 12.9x at 284 Å and from 3.4x to 15.1x at 335 Å
for the individual reflections in the optical path. We present the
results of coating the MOSES flight gratings and fold flat, including
the spectral response of the fold flat and grating as measured at
NIST's SURF III and Brookhaven's X24C beamline, respectively.
Title: An imager with added value for the Solar Orbiter mission
Authors: Harra, L. K.; Kankelborg, C. C.; Thomas, R. J.; Fox, J. L.;
Winter, B.
Bibcode: 2005AdSpR..36.1422H
Altcode:
Our current ways of observing the Sun with spectrometers and imagers
are limited. With a slit spectrometer, we require time to build up a
2-D image which results in temporal blurring. When we use a traditional
imager, we have no ability to measure and detect line-of-sight flows
or to discriminate contributions from gas at different temperatures
in the imager passband, causing spectral confusion of the images. For
Solar Orbiter, the combination of an exciting new viewpoint of the
Sun, and the best resolution of the corona ever seen, means that we
require the best time cadence and velocity information that we can
get. The spatial resolution expected from the imager on Solar Orbiter
will reach approximately 70 km. At such a resolution in the corona,
we expect to see the fundamental magnetic flux tubes, which are
predicted to have high velocities. This is also the scale at which we
will be able to search for evidence basic physical processes such as
magnetic reconnection. We will describe the design of an imager that
gives not only high quality images, but also provides simultaneous
information about plasma flows and temperature. A prototype instrument
is being flown on a NASA sounding rocket next year. The concept will
be described, along with some methods of extracting the spectroscopic
information.
Title: Fast Inversion of MOSES Data
Authors: Kankelborg, C. C.; Fox, J. L.
Bibcode: 2004AAS...204.6901K
Altcode: 2004BAAS...36..794K
The Multi-Order Solar EUV Spectrograph (MOSES) is a snapshot imaging
spectrometer payload planned for launch from White Sands Missile
Range in August, 2004. We describe the Smooth Multiplicative Algebraic
Reconstruction Technique (SMART), a new algorithm for near real time
reconstruction of line profile parameters from MOSES data. Though the
technique was developed for generating a quick look data product,
the results have high fidelity. In simulations, doppler shifts are
reconstructed with 0.25 pixel accuracy (RMS).
Title: An imager with added value for the Solar Orbiter mission
Authors: Harra, L.; Kankelborg, C.; Thomas, R.; Fox, J.; Winter, B.
Bibcode: 2004cosp...35.1120H
Altcode: 2004cosp.meet.1120H
Our current ways of observing the Sun with spectrometers and imagers
are limited. When we use a spectrometer, we require time to build
up an image. When we use a traditional imager we have no ability to
measure and detect Doppler flows. These limitations will become even
more restrictive on Solar Orbiter. The combination of an exciting new
viewpoint of the Sun, and the best resolution of the corona ever seen,
means that we require the best time cadence and velocity information
that we can get. The spatial resolution expected from the imager on
Solar Orbiter will reach approximately 30 km. At such a resolution in
the corona, we expect to see the fundamental flux tubes, which are
predicted to have high velocities. This is also the scale at which
we will be able to observe basic physical processes such as magnetic
reconnection occurring. We will describe a design of an imager that
allows not only high quality images, but also obtains information about
Doppler flows simultaneously. A prototype instrument is being flown
on a NASA sounding rocket this year. The concept will be described,
along with some methods of deconvolving the spectroscopic information.
Title: The Relationship Between X-Ray Radiance and Magnetic Flux
Authors: Pevtsov, Alexei A.; Fisher, George H.; Acton, Loren W.;
Longcope, Dana W.; Johns-Krull, Christopher M.; Kankelborg, Charles
C.; Metcalf, Thomas R.
Bibcode: 2003ApJ...598.1387P
Altcode:
We use soft X-ray and magnetic field observations of the Sun (quiet
Sun, X-ray bright points, active regions, and integrated solar disk)
and active stars (dwarf and pre-main-sequence) to study the relationship
between total unsigned magnetic flux, Φ, and X-ray spectral radiance,
LX. We find that Φ and LX exhibit a very nearly
linear relationship over 12 orders of magnitude, albeit with significant
levels of scatter. This suggests a universal relationship between
magnetic flux and the power dissipated through coronal heating. If the
relationship can be assumed linear, it is consistent with an average
volumetric heating rate Q~B/L, where B is the average field strength
along a closed field line and L is its length between footpoints. The
Φ-LX relationship also indicates that X-rays provide a
useful proxy for the magnetic flux on stars when magnetic measurements
are unavailable.
Title: A Fluxon Model for the Behavior of Solar Force-Free Magnetic
Fields
Authors: Blane McCracken, Stephen; Kankelborg, Charles
Bibcode: 2003APS..SES.JB006B
Altcode:
For years solar physics has sought to explain the incredible energy
emissions of the sun, like coronal mass ejections and flares. One of
the main reasons for this study is that areas of high solar activity
can cause disruptions of technological equipment like our satellite
network and power grids. It has been proven that magnetic fields are the
main cause for all solar activity, and have therefore become the main
focus of this branch of physics. I have been working with Dr. Charles
Kankelborg of Montana State University on a computational model of the
behavior of solar force-free magnetic fields and the ways in which
they interact and release energy through relaxation of the field
tension and repulsion. The model proposes that the field is composed
of discrete bundles of constant magnetic flux called "fluxons,"
which are represented as distinct lines. With this new ability,
it is possible to study various theoretical field configurations,
how these fields interact, and what the final configuration may be
after relaxation. (This work made possible by support from a National
Science Foundation REU.)
Title: Data inversion for the Multi-Order Solar Extreme-Ultraviolet
Spectrograph
Authors: Fox, J. Lewis; Kankelborg, Charles C.; Metcalf, Tomas R.
Bibcode: 2003SPIE.5157..124F
Altcode:
The Multi-Order Solar Extreme Ultraviolet Spectrograph (MOSES) is
a high resolution, slitless imaging spectrometer that will observe
the Sun in extreme ultraviolet near 304A. MOSES will fly on a NASA
sounding rocket launch in spring 2004. The instrument records spatial
and spectral information into images at three spectral orders. To
recover the source spectrum, an ill-posed inversion must be performed
on these data. We will explore two of the techniques by which this may
be accomplished: Fourier backprojection and Pixons, constrained by the
spatially integrated spectrum of the Sun. Both methods produce good
results, including doppler shifts measured to 1/3-pixel accuracy. The
Pixon code better reproduces the line widths.
Title: SADE: The starspot and dynamo explorer
Authors: Martens, P. C. H.; Acton, L. W. A.; Klumpar, D.; Kankelborg,
C.; Stern, R. A.; Peres, G.; Culhane, J. L.
Bibcode: 2003AdSpR..32.1123M
Altcode:
We propose a mission called SADE, the Starspot And Dynamo Explorer, to
study dynamo activity in nearby late-type stars. The onboard instruments
will be a Ca-K telescope for magnetically dominated chromospheric
emission, and an X-ray grazing incidence telescope to study coronal
emission. We design the mission for a life-time of 15 years or longer
to capture a full activity cycle for most solar-type stars. We aim to
firmly establish the spectrum of the relation between chromospheric
and corona' emission in late-type stars, and capture one or more stars
going into or coming out of a Maunder type minimum. Operation costs will
be kept to a minimum by automating mission operations to a maximum,
and have the science operations be carried out by students at Montana
State University.
Title: The Importance of Plasma Viscosity in Narrow Band Bright
Point Observations
Authors: McMullen, R. A.; Longcope, D. W.; Kankelborg, C. C.
Bibcode: 2002AAS...200.0201M
Altcode: 2002BAAS...34R.639M
We explore the importance of compressional viscosity in models and
observations of an X-ray bright point. Comparison of hydrodynamic
models with and without compressive viscosity allow us to separate its
physical effects during small scale heating events that differ only in
the presence or absence of viscous effects. Heating models are designed
to emulate TRACE and SOHO/MDI observations of a June 17, 1998 bright
point transient brightening through variations in the temporal heat
distribution. Analysis methods of data and model accuracy are explored.
Title: Sensitivity of MOSES to Chromospheric Spectral Line Profiles
Authors: Kankelborg, C. C.
Bibcode: 2002AAS...200.5506K
Altcode: 2002BAAS...34..733K
The Multi-Order Solar EUV Spectrograph (MOSES) is a new type of slitless
imaging spectrograph with detectors at three spectral orders (-1,
0, 1). The slitless configuration allows collection of spectroscopic
information simultaneously over a 2D image. This study assesses the
information content of an idealized MOSES data set by deriving and
analyzing the null space of the instrument response. The conclusion is
that MOSES is sensitive to line intensity, line width, and doppler shift
but is insensitive to higher moments of the line profile. Addition of
detectors at higher orders would impart sensitivity to line asymmetry
and higher moments. This work is funded by NASA Grant NAG5-10997.
Title: A Parametric Inversion Technique for MOSES Data
Authors: Fox, J. L.; Kankelborg, C. C.
Bibcode: 2002AAS...200.5508F
Altcode: 2002BAAS...34..733F
MOSES (the Multi-Order Slitless EUV Spectrograph) will be capable of
simultaneous 2-D imaging and spectroscopy of the solar transition
region at high spatial and temporal resolution. The MOSES data are
a convolution of spatial and spectral variables. To obtain an image
cube, in coordinates (x,y,λ ), one must solve an ill-posed inverse
problem. We describe and implement an approach which parameterizes the
image cube in terms of spectral line moments. We use the inversion code
to recover test data obtained from SERTS 95 which has been processed
through a forward model of the MOSES instrument response, and evaluate
the performance of this parametric inversion technique. This work is
funded by NASA Grant NAG5-10997.
Title: Forward Modeling of MOSES Response to the Solar Atmosphere
Authors: Cirtain, M. J. S.; Kankelborg, C. C.; Reiser, M.
Bibcode: 2002AAS...200.5507C
Altcode: 2002BAAS...34Q.733C
Using high resolution TRACE data, we have generated a suite of models
for EUV intensity and line profiles in He II and Si XI. The models are
used to simulate the response of the Multi-Order Solar EUV Spectrograph
(MOSES) rocket instrument to realistic solar features. This research
is supported by NASA Grant NAG5-10997.
Title: Modeling the coronal loop of an X-ray bright point
Authors: McMullen, R.; Longcope, D.; McKenzie, D.; Kankelborg, C.;
Klimchuk, J.
Bibcode: 2002ocnd.confE..28M
Altcode:
No abstract at ADS
Title: Nanoflare Modeling of an X-Ray Bright Point Coronal Loop
Authors: McMullen, R. A.; Longcope, D. W.; Kankelborg, C. C.
Bibcode: 2002mwoc.conf...95M
Altcode:
We study the spatial structure and temporal evolution of an X-ray
bright point loop in order to understand the role of magnetic energy
dissipation. We use a time-dependent gasdynamic model to simulate
the corona and transition region in the x-ray bright point's coronal
loop. For this work we model a bright point observed by TRACE and SOHO
on June 17, 1998, where the magnetic field geometry is derived from an
extrapolation of magnetograms. We study the effects of various spatial
and temporal distributions of heat deposition within the loop. The
quantity of energy deposited and the location of the energy release
is constrained by a model equilibrium magnetic field. We model the
observed transient brightening of the bright point as a series of
nanoflare events.
Title: Optical Design of the MOSES Sounding Rocket Experiment
Authors: Thomas, R. J.; Kankelborg, C. C.
Bibcode: 2001AAS...199.8807T
Altcode: 2001BAAS...33.1434T
The Multi-Order Solar EUV Spectrograph (MOSES) is a sounding
rocket payload now being developed by Montana State University in
collaboration with the Goddard Space Flight Center, Lockheed Martin
Advanced Technology Center, and Mullard Space Science Laboratory. The
instrument utilizes a unique optical design to provide solar EUV
measurements with true 2-pixel resolutions of 1.0 arcsec and 60 mÅ
over a full two-dimensional field of view of 1056 x 528 arcsec, all
at a time cadence of 10 s. This unprecedented capability is achieved
by means of an objective spherical grating 100 mm in diameter, ruled
at 833 gr/mm. The concave grating focuses spectrally dispersed solar
radiation onto three separate detectors, simultaneously recording
the zero-order as well as the plus and minus first-spectral-order
images. Data analysis procedures, similar to those used in X-ray
tomography reconstructions, can then disentangle the mixed spatial and
spectral information recorded by the multiple detectors. A flat folding
mirror permits an imaging focal length of 4.74 m to be packaged within
the payload's physical length of 2.82 m. Both the objective grating and
folding flat have specialized, closely matched, multilayer coatings that
strongly enhance their EUV reflectance while also suppressing off-band
radiation that would otherwise complicate data inversion. Although
the spectral bandpass is rather narrow, several candidate wavelength
intervals are available to carry out truly unique scientific studies
of the outer solar atmosphere. Initial flights of MOSES, scheduled
to begin in 2004, will observe a 10 Å band that covers very strong
emission lines characteristic of both the sun's corona (Si XI 303 Å)
and transition-region (He II 304 Å). The MOSES program is supported
by a grant from NASA's Office of Space Science.
Title: Simultaneous imaging and spectroscopy of the solar atmosphere:
advantages and challenges of a 3-order slitless spectrograph
Authors: Kankelborg, Charles C.; Thomas, Roger J.
Bibcode: 2001SPIE.4498...16K
Altcode:
The dynamic solar atmosphere poses a severe observational challenge
for imaging spectroscopy in EUV. The traditional method of building up
images by rastering a slit spectrograph has so far proven too slow to
keep up with the Sun's rapidly changing transition region and corona. We
describe a new approach, using a slitless imaging spectrograph
operating in a narrow band, with imaging detectors at three orders. This
arrangement offers cotemporal imaging and spectroscopy at high spatial,
spectral, and temporal resolution. The prospect of disentangling spatial
and spectral information is greatly improved by choosing a narrow band
containing only two spectral lines, and by imaging at several spectral
orders. This paper discusses several advantages and challenges of the
multi-order slitless approach. We derive a mathematical description
of the null space of spatial-spectral signatures to which an ideal
three-order slitless spectrograph has zero response. An exploration of
the null space helps to clarify the capabilities and limitations of this
instrument type. We infer that the three-order slitless spectrograph
is sensitive to line intensity, doppler shift and line width; but
insensitive to line asymmetry. Strategies are developed to minimize
the ambiguity in interpreting the multi-order data. A proof of concept
sounding rocket payload, the Multi-Order Solar EUV Spectrograph (MOSES),
is under development with an anticipated launch in Spring, 2004.
Title: Simulations of an X-Ray Bright Point's Evolution
Authors: McMullen, R. A.; Longcope, D. W.; McKenzie, D. E.; Kankelborg,
C. K.
Bibcode: 2001AGUFMSH11C0726M
Altcode:
We study the spatial structure and temporal evolution of an X-ray
bright point loop in order to understand the role of magnetic energy
dissipation. We use a time-dependent gasdynamic model to simulate
the corona and transition region in the x-ray bright point's coronal
loop. For this work we model a bright point observed by TRACE, Yohkoh
and SOHO on June 17, 1998, where the magnetic field geometry is derived
from an extrapolation of magnetograms. We study the effects of various
spatial and temporal distributions of heat deposition within the
loop. The quantity of energy deposited and the location of the energy
release is constrained by a model equilibrium magnetic field. We model
the observed transient brightening of the bright point as a series of
nanoflare events.
Title: Science objectives of the EUV spectral imager for Solar Orbiter
Authors: Martens, Petrus C.; Kankelborg, Charles C.
Bibcode: 2001ESASP.493..293M
Altcode: 2001sefs.work..293M
No abstract at ADS
Title: Simultaneous EUV imaging and spectroscopy
Authors: Kankelborg, Charles C.; Martens, Petrus C.; Thomas, Roger J.
Bibcode: 2001ESASP.493..257K
Altcode: 2001sefs.work..257K
No abstract at ADS
Title: Topology is destiny: Reconnection energetics in the corona
Authors: Longcope, D. W.; Kankelborg, C. C.
Bibcode: 2001EP&S...53..571L
Altcode:
Magnetic reconnection is clearly at work in the solar corona
reorganizing and simplifying the magnetic field. It has also been
hypothesized that this reorganization process somehow supplies
the energy heating the corona. We propose a quantitative model
relating the topological role (simplification) and the energetic role
(heating) of magnetic reconnection. This model is used to analyze
multi-wavelength observations of an X-ray bright point. In the model,
motion of photospheric sources drives reconnection of coronal flux. If
reconnection occurs only sporadically then energy is stored in the
coronal field, and released by topological reconnection. We simulate
the dynamical response of the plasma to such an energy release, and
translate this into predicted observational signatures. The resulting
predictions are difficult to reconcile with the observations. This
suggests that while reconnection is important in the corona, energy
dissipation is governed by other factors, not all of which relate to
the topology of the field.
Title: Fluxon Modeling of Force Free Magnetic Fields: Voronoi Method
Authors: DeForest, C. E.; Kankelborg, C. C.; Longcope, D. W.
Bibcode: 2001AGUSM..SH41A18D
Altcode:
We present a promising new form of quasi-Lagrangian magnetic model for
the corona, a ``fluxon model''. Fluxons are discrete representations of
field lines. Fluxon-based models are similar to traditional Lagrangian
field models in that they have no numerical resistivity because
field topology is explicitly preserved. They differ from traditional
Lagrangian models in two ways: there is no fixed set of proximity
relationships between the discrete elements of the model, preventing
numerial runaway in evolving systems; and div B is explicitly maintained
at 0. In a force-free field, the magnetic pressure and tension forces
are in equilibrium. The fluxon formulation reduces determination
of the field to a relaxation process. Calculation of the magnetic
pressure and tension forces at each step in the relaxation is reduced
to a variant of known, solved problems in computational geometry. In
this presentation, we demonstrate a computationally efficient method
of calculating these forces, using an approximation to the ``Voronoi
foam'' of spatial neighborhoods defined by a particular collection of
fluxons. Magnetic field modeling with fluxons offers several advantages:
(1) it facilitates detailed investigation of field topology; (2)
reconnection is completely controllable, because there is no numerical
resistivity; (4) the modeled structures may be critically sampled,
raising the prospect of unprecedented computational efficiency. These
advantages together will ultimately allow explicit modeling of stability
and reconnection in complex, slowly evolving coronal features such as
polar plumes, prominences, and active regions.
Title: A Reflight of the Explorer-1 Science Mission: The Montana
EaRth Orbiting Pico Explorer (MEROPE)
Authors: Klumpar, D. M.; Obland, M.; Hunyadi, G.; Jepsen, S.; Larsen,
B.; Kankelborg, C.; Hiscock, W.
Bibcode: 2001AGUSM..SM52A19K
Altcode:
Montana State University's interdisciplinary Space Science and
Engineering Laboratory (SSEL) under support from the Montana NASA Space
Grant Consortium is engaged in an earth orbiting satellite student
design and flight project. The Montana EaRth Orbiting Pico Explorer
(MEROPE) will carry a modern-day reproduction of the scientific
payload carried on Explorer-1. On February 1, 1958 the United States
launched its first earth orbiting satellite carrying a 14 kg scientific
experiment built by Professor James Van Allen's group at the State
University of Iowa (now The University of Iowa). The MEROPE student
satellite will carry a reproduction, using current-day technology, of
the scientific payload flown on Explorer-1. The CubeSat-class satellite
will use currently available, low cost technologies to produce a
payload-carrying satellite with a total orbital mass of 1 kg in a volume
of 1 cubic liter. The satellite is to be launched in late 2001 into a
600 km, 65° inclination orbit. MEROPE will utilize passive magnetic
orientation for 2-axis attitude control. A central microprocessor
provides timing, controls on-board operations and switching, and enables
data storage. Body mounted GaAs solar arrays are expected to provide
in excess of 1.5 W. to maintain battery charge and operate the bus and
payload. The Geiger counter will be operated at approximately 50% duty
cycle, primarily during transits of the earth's radiation belts. Data
will be stored on board and transmitted approximately twice per day to
a ground station located on the Bozeman campus of the Montana State
University. Owing to the 65° inclination, the instrument will also
detect the higher energy portion of the electron spectrum responsible
for the production of the Aurora Borealis. This paper describes both the
technical implementation and design of the satellite and its payload
as well as the not inconsiderable task of large team organization
and management. As of March 2001, the student team consists of
four graduate students and approximately 45 undergraduates in fields
including Physics, Engineering, Computer Sciences, Business, and Liberal
Arts. Satellites of this class have the potential to lead to low-cost
constellations of sciencecraft making coordinated measurements of the
highly dynamic and spatially structured space environment. While key
tradeoffs between resource needs and resource availability (e.g. power,
telemetry, mass, volume, and cost) constrain payload sophistication,
the tremendous advantages of having even simple dispersed multipoint
measurements of the Geospace environment far outweigh the loss of
payload sophistication in many instances.
Title: Evidence of Separator Reconnection in a Survey of X-Ray
Bright Points
Authors: Longcope, D. W.; Kankelborg, C. C.; Nelson, J. L.; Pevtsov,
A. A.
Bibcode: 2001ApJ...553..429L
Altcode:
X-ray bright points are among the simplest coronal structures
hypothesized to be powered by magnetic reconnection. Their
magnetic field appears to consist of a simple loop of field lines
connecting positive to negative photospheric sources. Quantitative
three-dimensional models of reconnection in this geometry are therefore
expected to apply directly to X-ray bright points. We assemble a survey
from archival Solar and Heliospheric Observatory data of 764 X-ray
bright points (EUV Imaging Telescope) along with their associated
photospheric magnetic fields (Solar Oscillation Imager/Michelson
Doppler Imager). Measurements are made of each quantity relevant to
the simple three-dimensional reconnection model. These data support
several predictions of a magnetic reconnection model providing further
evidence in favor of the hypothesis that magnetic reconnection supplies
heating power to the quiet solar corona.
Title: Modeling the Coronal Loop of an X-ray Bright Point
Authors: McMullen, R. A.; Kankelborg, C. C.; Longcope, D. W.
Bibcode: 2001AGUSM..SH41A16M
Altcode:
We use a time-dependent gasdynamic model to simulate the corona
and transition region in an x-ray bright point loop. For this
work we model a bright point observed by TRACE and SOHO on June 17,
1998. The magnetic field geometry is derived from an extrapolation of
magnetograms. We study the effects of various hypothesized spatial and
temporal distributions of heat deposition within the loop, including
Joule heating at the footpoints or decay of standing Alfvén waves.
Title: Lagrangian Modeling of Force Free Fields and Current Sheets:
Fluxon representation and the Kernel Method
Authors: Kankelborg, C. C.; Longcope, D. W.; DeForest, C. E.
Bibcode: 2001AGUSM..SH41A17K
Altcode:
In force free magnetic fields, the magnetic pressure and tension forces
are balanced. These forces may be represented in terms of arrangements
of field lines (``fluxons''). We demonstrate a novel Lagrangian
technique for modeling of force-free configurations in 2D and 3D with
and without current sheets. The fundamental computational element
in our model is the fluxon, a field-line-like entity that represents
the configuration of a finite quantity of magnetic flux. The magnetic
field in a volume is represented as a collection of fluxons, each with a
geometry defined by a connected series of points. The magnetic curvature
force is easily determined by finite differencing along a fluxon. A
smoothing kernel is used to evaluate magnetic field strength and its
gradient. By these means, the Lorentz force is determined. Relaxation
to a force free state is accomplished by displacing the fluxons in the
direction indicated by the Lorentz force. Further calculations with
the smoothing kernel allow the evaluation of stored magnetic energy
and mapping of current distributions in the volume. Magnetic field
modeling in the fluxon representation offers several advantages:
(1) it facilitates detailed investigation of field topology; (2)
reconnection is completely controllable --- it cannot occur unless
it is explicitly inserted into the model; (3) there is no numerical
resistivity; (4) current sheets are critically sampled, raising the
prospect of unprecedented computational efficiency.
Title: Solar Plumbing? Constraints on the 3D geometry of
constant-width coronal loops.
Authors: Martens, P. C. H.; Kankelborg, C. C.
Bibcode: 2000SPD....31.0144M
Altcode: 2000BAAS...32R1289M
Coronal loops are observed to have nearly constant apparent width
(Klimchuk, 1999; Watko & Klimchuk, 1999). We will show that only
one basic geometry is possible for constant-width coronal loops in
a force free magnetic field. In particular, the loop must describe a
helix. Furthermore, the torsion of the loop is determined solely by
the value of the force free parameter, alpha = (curl B) / B.
Title: On the Nature of the ``Moss'' Observed by TRACE
Authors: Martens, P. C. H.; Kankelborg, C. C.; Berger, T. E.
Bibcode: 2000ApJ...537..471M
Altcode:
``Moss'' is the name given to low-lying (~3000 km), hot (~1 MK) solar
coronal plasma that has been observed recently by the Transition
Region and Coronal Explorer (TRACE). This paper investigates two
hypotheses regarding the nature of the moss: (1) emission from small,
million degree loops; (2) emission from the legs of 3-10 million
degree loops. We update the coronal radiative loss curve, using the
most recent results for coronal abundances, and use an analytical loop
model to find that the first hypothesis requires a filling factor close
to unity to reproduce the observed emission measure, while the second
hypothesis results in a filling factor of about 0.1, in agreement
with other independent multiwavelength analyses of moss. We find that
the vertical extent and the height of the moss layer above the limb
are also very well reproduced with the second hypothesis. We further
show that the observed brightness of the moss scales linearly with
the loop pressure and filling factor, independent of the loop length,
and we derive a general expression for the conversion factor.
Title: Time Variability of the ``Quiet'' Sun Observed with
TRACE. II. Physical Parameters, Temperature Evolution, and Energetics
of Extreme-Ultraviolet Nanoflares
Authors: Aschwanden, Markus J.; Tarbell, Ted D.; Nightingale, Richard
W.; Schrijver, Carolus J.; Title, Alan; Kankelborg, Charles C.;
Martens, Piet; Warren, Harry P.
Bibcode: 2000ApJ...535.1047A
Altcode:
We present a detailed analysis of the geometric and physical
parameters of 281 EUV nanoflares, simultaneously detected with the
TRACE telescope in the 171 and 195 Å wavelengths. The detection and
discrimination of these flarelike events is detailed in the first paper
in this series. We determine the loop length l, loop width w, emission
measure EM, the evolution of the electron density ne(t) and
temperature Te(t), the flare decay time τdecay,
and calculate the radiative loss time τloss, the conductive
loss time τcond, and the thermal energy Eth. The
findings are as follows: (1) EUV nanoflares in the energy range of
1024-1026 ergs represent miniature versions
of larger flares observed in soft X-rays (SXR) and hard X-rays
(HXR), scaled to lower temperatures (Te<~2 MK),
lower densities (ne<~109 cm-3),
and somewhat smaller spatial scales (l~2-20 Mm). (2) The cooling
time τdecay is compatible with the radiative cooling
time τrad, but the conductive cooling timescale
τcond is about an order of magnitude shorter, suggesting
repetitive heating cycles in time intervals of a few minutes. (3)
The frequency distribution of thermal energies of EUV nanoflares,
N(E)~10-46(E/1024)-1.8 (s-1
cm-2 ergs-1) matches that of SXR microflares
in the energy range of 1026-1029, and exceeds
that of nonthermal energies of larger flares observed in HXR by a
factor of 3-10 (in the energy range of 1029-1032
ergs). Discrepancies of the power-law slope with other studies, which
report higher values in the range of a=2.0-2.6 (Krucker & Benz;
Parnell & Jupp), are attributed to methodical differences in the
detection and discrimination of EUV microflares, as well as to different
model assumptions in the calculation of the electron density. Besides
the insufficient power of nanoflares to heat the corona, we find also
other physical limits for nanoflares at energies <~1024
ergs, such as the area coverage limit, the heating temperature limit,
the lower coronal density limit, and the chromospheric loop height
limit. Based on these quantitative physical limitations, it appears
that coronal heating requires other energy carriers that are not
luminous in EUV, SXR, and HXR.
Title: Having Our Cake and Eating it, Too: Fast Imaging Spectroscopy
With a Multi-Order Slitless Spectrograph
Authors: Kankelborg, C. C.; Longcope, D. W.; Martens, P. C. H.
Bibcode: 2000SPD....3102101K
Altcode: 2000BAAS...32..829K
We describe a new type of EUV imaging spectrograph that combines high
spectral, spatial and temporal resolution. The instrument consists of
a slitless spectrograph with cameras placed at several diffraction
orders. The unique information derived from simultaneous imaging
at multiple orders allows the deconvolution of spectral and spatial
information, thus overcoming the limitations of a traditional slitless
spectrograph.
Title: X-ray bright points: A case study in solar reconnection
Authors: Longcope, D.; Kankelborg, C.
Bibcode: 2000SPD....31.1304L
Altcode: 2000BAAS...32..845L
Magnetic reconnection is believed to play an important role in the
energetics of the solar corona including flaring and quiescent heating
in active regions. It is also implicated as the energy source for
X-ray bright points which occur in coronal holes and in the quiet
Sun. X-ray bright points are the ideal feature in which to study
magnetic reconnection since they have relatively simple geometry:
two isolated sources of photospheric flux approaching one another. By
assuming that all power comes from the process of forging new field
lines to connect the approaching poles we are lead to a simple
quantitative model for an X-ray bright point. To test the model the
predicted energy release is used in a dynamical simulation of loop
plasma evolution. The results of this simulation are used to sythesize
images in the EUV for direct comparison to a TRACE observation. A
second test of the model is provided by a statistical study of X-ray
bright points and bipoles in archival SOHO data. The results of this
survey support several predictions of the model. Finally, the model
is applied to a theoretical distribution of flux elements to yield a
model for heating of the quiet Sun. This produces expressions for the
density of X-ray bright points and total heat flux.
Title: Solar Public Outreach on a Shoestring Budget: A Community
Approach
Authors: Larson, M. B.; Kankelborg, C. K.; Longcope, D. W.
Bibcode: 2000SPD....3102123L
Altcode: 2000BAAS...32R.833L
Multi-thousand (or even multi-million) dollar Education and Public
Outreach (E/PO) efforts have increased science knowledge and awareness
within the public school system and amongst the general public. In
addition to such large scale outreach programs, there is a niche to
be filled by low budget, widespread outreach efforts like the one
we suggest here. We propose a low budget (approx. \$1000/yr) Public
Outreach effort which utilizes the strong network of amateur astronomy
clubs that exist in most areas. Through cooperation with local contacts,
this public outreach effort works at the community level, and involves
the delivery of scientifically interesting and visually engaging public
lectures by solar research scientists to underserved regions in their
home state.
Title: High resolution imaging with multilayer telescopes: resolution
performance of the MSSTA II Telescopes
Authors: Martinez-Galarce, Dennis S.; Walker, Arthur B.; Gore, David
B.; Kankelborg, Charles C.; Hoover, Richard B.; Barbee, Troy W.;
Boerner, Paul F.
Bibcode: 2000OptEn..39.1063M
Altcode:
The Multi-Spectral Solar Telescope Array (MSSTA) is a sounding
rocket-borne observatory composed of a set of normal-incidence
multilayer-coated telescopes that obtained selected bandpass
spectroheliograms (44 to 1550 angstroms) of the solar atmosphere. These
spectroheliograms were recorded on specially fabricated XUV And
FUV 70-mm Kodak film. Rocket launches of this instrument payload
took place in 1991 (MSSTA I) and 1994 (MSSTA II) at the White
Sands Missile Test Range in New Mexico, sponsored by the National
Aeronautics and Space Administration (NASA) sounding rocket experiment
program. Immediately prior to the 1994 launch, visible light focusing
tests of each telescope were performed in situ using a 1951 standard
Air Force high- resolution test target, to measure optical resolution
performance. We determined that the MSSTA II telescopes performed
at diffraction-limited resolutions down to 0.70 arcsec at visible
wavelengths. Based on these measurements, we calculate an upper bound
to the focusing errors that incorporate the sum of all uncorrelated
system focus errors that affect resolution performance. Coupling these
upper bound estimates with the in-band diffraction limits, surface
scattering errors and payload pointing jitter, we demonstrate that 11
of 19 MSSTA II telescopes--having negligible figures of focus errors in
comparison to the corresponding visible diffraction limits--performed at
sub arcsecond resolution at their operational FUV/EUV/XUV wavelengths
during flight. We estimate the in-band performance down to 0.14 +/-
0.08 arcsec.
Title: Forward modeling of the coronal response to reconnection in
an X-ray bright point
Authors: Kankelborg, Charles; Longcope, Dana
Bibcode: 1999SoPh..190...59K
Altcode:
We use MDI magnetic field observations and the theory of reconnection
through a separator to constrain a numerical simulation of an X-ray
bright point observed in EUV by TRACE. A gasdynamic model is employed
to describe the corona and transition region in the bright point
loop. Nonlocal effects such as opacity and ambipolar diffusion are
important to the transition region; these effects are approximated
locally by modification of the radiative loss and thermal conduction. A
straightforward comparison of measured light curves versus those
generated by the simulation shows that the reconnection model is unable
to account for the observations.
Title: Coronal Heating by Collision and Cancellation of Magnetic
Elements
Authors: Longcope, D. W.; Kankelborg, C. C.
Bibcode: 1999ApJ...524..483L
Altcode:
A model is proposed for the coronal response to the interaction between
randomly moving photospheric magnetic flux elements. In this model the
collision between two elements of opposing signs results in reconnection
and the appearance of an X-ray bright point. A section of quiet Sun on
which elements are distributed and moving randomly will contain a number
of X-ray bright points. The model combines a distribution of element
sizes, random velocities of the elements, and a model for pair-wise
collisions. This results in quantitative predictions for surface
density of X-ray bright points, the distribution of their luminosities,
and their contribution to the total heat flux in the quiet Sun. The
predictions depend principally on the densities of flux elements of
each sign B¯+ and B¯-, the average element size
Φ¯, and the random velocity v0. The predicted heat flux,
FXBP=0.1B¯+B¯-v0, is in
rough agreement with published observational studies of X-ray bright
points but well below the flux required to supply heat to the quiet
Sun corona. Other predictions of the model are similarly consistent
with published studies.
Title: VLA Decimetric Observations of EUV Transient Events Detected
by SOHO and TRACE
Authors: Willson, Robert F.; Kankelborg, Charles
Bibcode: 1999ESASP.446..715W
Altcode: 1999soho....8..715W
Very Large Array (VLA) observations of active region at 2, 6, 20.7 and
91.6 cm are compared with simultaneous EUV images taken by SOHO and
TRACE at several wavelengths. The main objective of these observations
is to study the properties of evolving magnetic loop structures at
different heights in the transition region and corona where impulsive
and long-lasting energy release takes place. VLA observations at 2
and 6 cm wavelength have been used to measure the sizes, locations and
lifetimes of small-scale, variable magnetic structures detected by the
SOHO EIT and TRACE and to discriminate between thermal and nonthermal
emission mechanisms in these sources. Our VLA 91 cm observations have
been used to study the relationship between long-lasting Type I noise
storm emission and underlying compact magnetic loops seen by EIT and
TRACE as well as larger coronal structures seen at the solar limb by the
LASCO coronagraphs. Our results show that one one day, a Type I noise
storm enhancement began a few tens of minutes after a prominent EUV
ejection event detected by TRACE, suggesting that the nonthermal noise
storm emission may have been triggered by the diffusion of magnetic
fields and particles from the underlying site of energy release. On
other days, there appears to be a weaker correlation between changes in
the intensity of the noise storm emission and underlying EUV events,
suggesting an independent origin for the noise storm emission in
these regions.
Title: High-resolution imaging with multilayer telescopes: resolution
performance of the MSSTA II telescopes
Authors: Martinez-Galarce, Dennis S.; Walker, Arthur B.; Gore, David
B.; Kankelborg, Charles C.; Hoover, Richard B.; Barbee, Troy W.;
Boerner, Paul F.
Bibcode: 1999SPIE.3766..275M
Altcode:
The Multi-Spectral Solar Telescope Array (MSSTA) is a sounding
rocket-borne observatory composed of a set of normal-incidence
multilayer-coated telescopes that obtained selected bandpass
spectroheliograms of the Solar atmosphere. These spectroheliograms were
recorded on specially fabricated XUV and FUV 70mm Kodak film. Rocket
launches of this instrument payload took place in 1991 and 1994 at
the White Sands Missile Test Range in New Mexico, sponsored by the
NASA sounding rocket experiment program. Immediately prior to the 1994
launch, visible light focusing test of each telescope were performed
in-situ using a 1951 Standard Air Force High Resolution Test-target,
to measure optical resolution performance. We determined that the
MSSTA II telescopes performed at diffraction-limited resolutions down
to 0.70 arc-second at visible wavelengths. Based on these measurements,
we calculated an upper-bound to the focusing errors that incorporate the
sum of all uncorrelated system resolution errors that affect resolution
performance. Coupling these upper-bound estimates with the in-band
diffraction limits, surface scattering errors and payload pointing
jitter, we demonstrate that eleven of nineteen MSSTA II telescopes
- having negligible figures of focus errors in comparison to the
corresponding visible diffraction limits - performed at sub arc-second
resolution at their operation FUV/EUV/XUV wavelengths during flight. We
estimate the in-band performance down to 0.14 +/- 0.08 second of arc.
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: 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: A Survey of X-ray Bright Points: Implications for a
Reconnection Model
Authors: Kankelborg, C. C.; Nelson, J.; Longcope, D. W.; Pevtsov, A. A.
Bibcode: 1999AAS...194.1601K
Altcode: 1999BAAS...31..849K
We present a survey of over 350 bright points from archival SOHO
data. Extreme ultraviolet images were measured to determine orientation,
length, and brightness in the EIT 171 angstrom (Fe X, 1 MK) and 195
angstrom (Fe XII, 1.5 MK) passbands. MDI data were analyzed to obtain
the size, orientation, and magnetic flux of the corresponding magnetic
bipoles. The three-dimensional reconnection theory of Longcope (1998)
makes several predictions that may be tested with these data. For this,
the first phase of the study, we concentrate on the scaling of EUV
brightness with magnetic flux and the distribution of displacement
angles between EUV bright points and their magnetic counterparts. We
also verify the assumption of Longcope & Kankelborg (1999) that
the distribution of magnetic orientations is random and independent
of latitude.
Title: On the Nature of the "Moss" Observed by TRACE
Authors: Martens, P. C. H.; Kankelborg, C. C.
Bibcode: 1999AAS...194.7903M
Altcode: 1999BAAS...31..963M
Moss is the name given to low lying ( 2 Mm), hot ( 1 MK) plasma that
has recently been observed by the Transition Region and Coronal
Explorer (TRACE). The moss occurs over some but not all magnetic
plage. We investigate two hypotheses regarding the nature of the moss:
(1) emission from small, million degree loops; (2) emission from the
legs of 2-5 million degree loops. An analytical loop model is used to
demonstrate that only the second hypothesis is consistent with the
observations. It is shown that the observed brightness of the moss
should scale as the third power of the loop maximum temperature.
Title: Heating from X-ray Bright Points in the Quiet Sun Corona:
A Quantitative Model
Authors: Longcope, D. W.; Kankelborg, C. C.
Bibcode: 1999AAS...194.1602L
Altcode: 1999BAAS...31..849L
It has proven difficult to quantify, even approximately, the theoretical
heat flux due to magnetic reconnection in the solar corona. Perhaps
the simplest example of coronal reconnection is an X-ray bright
point, where two isolated concentrations of photospheric flux are
swept together. A theory has been recently proposed providing a
theoretical estimate of the heat released by reconnection between the
two flux concentrations. This energy release depends on the flux of
each element, and the strength of the overlying field. The quiet Sun
contains a dense intermixture of photospheric flux concentrations of
each sign, spanning a wide range of fluxes. We calculate the rate at
which these elements collide to produce X-ray bright points, and the
energy released by each collision. Combining these ingredients provides
quantitative estimates for several properties of the quiet Sun corona,
including the heat flux from magnetic reconnection, the surface density
of X-ray bright points and their distribution in luminosity. Each of
these predictions compares favorably with published observations.
Title: The TRACE Mission: Initial Scientific Results
Authors: Title, A. M.; Tarbell, T. D.; Wolfson, J.; Schrijver, K.;
Fisher, R. R.; Gang, Th.; Golub, L.; McMullen, R. A.; Kankelborg,
C.; TRACE Collaboration
Bibcode: 1998AAS...19310008T
Altcode: 1998BAAS...30R1398T
TRACE (Transition Region and Coronal Explorer) is a Small Explorer
Mission (SMEX) devoted to studying the evolution and propagation
of fine-scale magnetic fields and plasma structures throughout the
solar atmosphere. The instrument consists of a telescope with a 30 cm
primary mirror, normal incidence coatings for three EUV bands (171,
195 and 284 Angstroms), and interference filters for UV bands (1216
to 1700 Angstroms) as well as white light (allowing the selection of
temperature ranges from ~ 6 000 to ~ 2 500 000 degrees K). The 1024
x 1024 CCD camera has a field of view of 8.5 arcmin with a spatial
resolution of 1 arcsec and exposure times of 0.002 to 260 sec with
a cadence as short as two seconds. The spacecraft was launched on
April 1, 1998, and first light for the telescope occurred on April
20. Observations have been collected nearly 24 hours per day since
then, with no significant problems in any segment of the spacecraft,
instrument, or mission operations. TRACE transmits about 3--4 GB of
data per week which gets automatically reformatted and becomes available
for the scientific community within approx. 24 hours. It is accessible
without restrictions (only guidelines) together with other informations
(technical details, educational material, movies, images,...) at:
http://vestige.lmsal.com/TRACE. The images reveal activity in the
solar atmosphere in stunning detail and include the first detailed
observations of a magnetic energy release. This magnetic reconnection
was observed on May 8, 1998, in a region of the solar atmosphere where
two sets of perpendicular magnetic loops expanded into each other (see
NASA Press Release 98-92). The TRACE mission has been developed and
operated by NASA's Goddard Space Flight Center, Lockheed Martin Solar
& Astrophysics Laboratory, Smithsonian Astrophysical Observatory,
and Montana State University.
Title: Observation and Modeling of Soft X-Ray Bright
Points. II. Determination of Temperature and Energy Balance
Authors: Kankelborg, Charles C.; Walker, Arthur B. C., II; Hoover,
Richard B.
Bibcode: 1997ApJ...491..952K
Altcode:
The Multispectral Solar Telescope Array was launched on 1991 May
13, in order to obtain narrowband images of the solar corona and
transition region. Calibrated EUV and H Lyman-α images are used
to constrain a simple loop model of the energy balance in 23 X-ray
bright points (XBPs). The results are consistent with substantial back
heating of the lower transition region by thermal conduction from the
corona. Statistical analysis shows that length and temperature are
uncorrelated for XBP loops; implications of this finding for coronal
heating are discussed. Some evidence is found for a systematic imbalance
between radiative and conductive losses. Inferences of effective loop
cross section by modeling suggest that the coronal filling factor is
nearly unity.
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: Observation and Modeling of Soft X-ray Bright
Points. II. Determination of Temperature and Energy Balance
Authors: Kankelborg, Charles. C.; Walker, Arthur B. C., II; Hoover,
Richard B.
Bibcode: 1997SPD....28.0132K
Altcode: 1997BAAS...29..885K
The Multispectral Solar Telescope Array was launched on 1991 May
13, obtaining narrowband images of the solar corona and transition
region. Calibrated EUV and H Lyman alpha images are used to constrain
a simple loop model of the energy balance in 23 x-ray bright
points. The results are consistent with substantial backheating
of the lower transition region by thermal conduction from the
corona. Statistical analysis shows that length and temperature are
uncorrelated for XBP loops; implications of this finding for coronal
heating are discussed. Some evidence is found for a systematic imbalance
between radiative and conductive losses. Inferences of effective loop
cross-section by modeling suggest that the coronal filling factor is
nearly 1.
Title: Observation and Modeling of Soft X-Ray Bright
Points. I. Initial Results
Authors: Kankelborg, Charles C.; Walker, Arthur B. C., II; Hoover,
Richard B.; Barbee, Troy W., Jr.
Bibcode: 1996ApJ...466..529K
Altcode:
The Multi-Spectral Solar Telescope Array was launched from White
Sands Missile Range, New Mexico, on 1991 May 13 at 1905 UT. Full-disk,
high-resolution solar images were obtained in a variety of soft X-ray
and far-ultraviolet wavelengths. The 193 Å (Fe XII) and 44 Å (Si
XII) images show a large number of coronal bright points. The high
spatial resolution of the Fe XII image allows many of the bright
points to be resolved as tiny loops. Co-alignment of the soft X-ray
images with the 1216 Å Lyα image reveals that all the coronal bright
points have counterparts in the transition region, often resolved as
a pair of footpoints, which are brighter than neighboring elements
of the chromospheric network. Moreover, comparison with the KPNO
magnetogram shows dipole structures coincident with nearly all of the
bright points. We present a quantitative analysis based on preliminary
photometry of four of the bright points that were observed. By fitting
a simple, numerical loop model to the photometric data, we estimate
the magnitude of the coronal heating in these structures. The rate of
heating per unit footpoint area is found to be similar to previous
measurements for much larger coronal structures. Implications for
heating of the chromosphere and lower transition region are also
discussed.
Title: Multispectral Observations of Coronal X-Ray Bright Points
Authors: Kankelborg, C. C.
Bibcode: 1996PhDT........72K
Altcode:
The Multi-Spectral Solar Telescope Array (MSSTA) was launched from
White Sands Missile Range, NM on May 13, 1991, at 1905 UT. Full disk,
high resolution solar images were obtained in a variety of extreme
ultraviolet (EUV) and far ultraviolet (FUV) wavelengths. Images from
the 211 Å (Fe XIV), 193 Å (Fe XII), 173 Å (Fe IX/X) and 44 Å
(Si XII) telescopes show a large number of coronal bright points. The
high spatial resolution of the EUV images allows many of the bright
points to be resolved as tiny loops. Coalignment of the EUV images with
the 1216 Å H Lyman alpha image reveals that all the coronal bright
points have counterparts in the transition region, often resolved as
a pair of footpoints, which are brighter than neighboring elements
of the chromospheric network. Moreover, comparison with a Kitt Peak
magnetogram taken at 1438 UT shows dipole structures coincident with
nearly all of the bright points. Based on this morphological evidence,
a simple coronal loop model is fitted to the calibrated photometric
data from the MSSTA telescopes. The resulting picture of energy balance
in these smallest coronal structures carries implications for the
heating of the solar corona and transition region. Implications for
multispectral plasma diagnostic techniques are also discussed.
Title: Optical focusing and alignment of the Multi-Spectral Solar
Telescope Array II payload
Authors: Gore, David B.; Hadaway, James B.; Hoover, Richard B.;
Walker, Arthur B.; Kankelborg, Charles C.
Bibcode: 1995SPIE.2515..532G
Altcode:
The Multi-Spectral Solar Telescope Array (MSSTA) is a sounding rocket
borne observatory designed to image the sun at many spectral lines in
soft x-ray, EUV, and FUV wavelengths. Of the nineteen telescopes flown
on November 3, 1994 the two Cassegrain telescopes and three of the six
Ritchey-Cretien telescopes were focussed at NASA/Marshall Space Flight
Center (MSFC) with a Zygo double-pass interferometer to determine the
best positions of back focus. The remaining three Ritchey-Cretien and
eleven Herschellian telescopes were focussed in situ at White Sands
Missile Range by magnifying the telescopic image through a Gaertner
traveling microscope and recording the position of best focus. From the
data obtained at visible wavelengths, it is not unreasonable to expect
that many of our telescopes did attain the sub-arc second resolution
for which they were designed.
Title: Design and performance of thin foil XUV filters for the
Multi-Spectral Solar Telescope Array II
Authors: Plummer, James E.; DeForest, Craig E.; Martinez-Galarce,
Dennis S.; Kankelborg, Charles C.; Gore, David B.; O'Neal, Ray H.;
Walker, Arthur B.; Powell, Forbes R.; Hoover, Richard B.; Barbee,
Troy W.; Weed, J. W.
Bibcode: 1995SPIE.2515..565P
Altcode:
The redesigned payload of the Multi-Spectral Solar Telescope Array
(MSSTA), the MSSTA II, was successfully flown on November 3, 1994. The
multilayer mirrors used in the normal incidence optical systems of the
MSSTA II are efficient reflectors for soft x-ray/extreme ultraviolet
(EUV) radiation at wavelengths that satisfy the Bragg condition,
thus allowing a narrow band of the soft x-ray/EUV spectrum to be
isolated. When applied to solar observations the temperature response
of an optical system is quite sensitive to telescope bandpass because
of the high density of lines in the coronal spectrum. We have designed
a set of thin foil filters in conjunction with our multilayer optics to
eliminate contaminant lines and specular reflectivity, thus enhancing
the temperature diagnostic capabilities of our instruments. Extensive
measurements have recently been carried out on the thin foil filters
at the Stanford Synchrotron Radiation Laboratory. We describe here the
design and performance of thin foil filters developed for the MSSTA II.
Title: Multi-Spectral Solar Telescope Array VIII: the second flight
Authors: Walker, Arthur B.; Allen, Maxwell J.; DeForest, Craig E.;
Kankelborg, Charles C.; Martinez-Galarce, Dennis S.; Plummer, James
E.; Hoover, Richard B.; Barbee, Troy W.; Gore, David B.
Bibcode: 1995SPIE.2515..182W
Altcode:
The Multi Spectral Solar Telescope Array (MSSTA) is a rocket borne
observatory that utilizes an array of multi-layer and interference film
coated telescopes to observe the solar atmosphere from the chromosphere
to the corona, over a broad spectral range (VUV - soft x rays). The
MSSTA is continuously evolved to incorporate new instruments, and
to improve its ability to investigate specific topics related to
the structure and dynamics of the solar atmosphere. We describe
chromospheric and coronal observations recorded during the second
flight of the MSSTA on November 3, 1994 at 1915 UT.
Title: Calibration of multilayer mirrors for the Multi-Spectral
Solar Telescope Array II
Authors: Kankelborg, Charles C.; Plummer, James E.; Martinez-Galarce,
Dennis S.; O'Neal, Ray H.; DeForest, Craig E.; Walker, Arthur B.;
Barbee, Troy W.; Weed, J. W.; Hoover, Richard B.; Powell, Forbes R.
Bibcode: 1995SPIE.2515..436K
Altcode:
The Multi-Spectral Solar Telescope Array II (MSSTA II), a rocket-borne
solar observatory, was successfully flown on November 3, 1994 obtaining
solar images in multiple XUV and FUV bands with an array of compact
multilayer telescopes. Extensive measurements have recently been carried
out on some of the multilayer telescopes at the Stanford Synchrotron
Radiation Laboratory. These measurements are the first high spectral
resolution calibrations of newly introduced MSSTA II instruments and
instruments with lambda0 less than 130 angstrom. Previous
measurements and/or calculations of telescope throughputs have been
confirmed with greater accuracy. Results are presented on Mo/Si
multilayer bandpasses, and multilayer bandpass changes with time.
Title: Observation and Modeling of Soft X-Ray Bright Points in the
Solar Corona
Authors: Kankelborg, C. C.; Walker, A. B. C., Jr.; Hoover, R. B.;
Barbee, T. W., Jr.
Bibcode: 1995SPD....26..614K
Altcode: 1995BAAS...27..964K
No abstract at ADS
Title: Performance of the multilayer-coated mirrors for the
MultiSpectral Solar Telescope Array
Authors: Allen, Maxwell J.; Willis, Thomas D.; Kankelborg, Charles
C.; O'Neal, Ray H.; Martinez-Galarce, Dennis S.; Deforest, Craig
E.; Jackson, Lisa R.; Plummer, James D.; Walker, Arthur B.; Barbee,
Troy W.; Weed, J. W.; Hoover, Richard B.
Bibcode: 1994SPIE.2011..381A
Altcode:
The Multi-Spectral Solar Telescope Array, a rocket-borne solar
observatory, was successfully flown in May, 1991, obtaining solar images
in eight XUV and FUV bands with 12 compact multilayer telescopes. We
report on recent measurements of the performance of multilayer coated
mirrors for the Multi Spectral Solar Telescope Array, carried out at
the Stanford Synchrotron Radiation Laboratory.
Title: Observations and Modeling of Soft X-Ray Bright Points in the
Solar Corona
Authors: Kankelborg, C. C.; Walker, A. B. C., Jr.; Hoover, R. B.;
Barbee, T. W.
Bibcode: 1993BAAS...25.1211K
Altcode:
No abstract at ADS
Title: Calibration of the multispectral solar telescope array
multilayer mirrors and XUV filters
Authors: Allen, Maxwell J.; Willis, Thomas D.; Kankelborg, Charles
C.; O'Neal, Ray H.; Martinez-Galarce, Dennis S.; Deforest, Craig E.;
Jackson, Lisa R.; Lindblom, Joakim F.; Walker, Arthur B.; Barbee,
Troy W., Jr.; Weed, J. W.; Hoover, Richard B.; Powell, Forbes R.
Bibcode: 1993SPIE.1742..562A
Altcode:
The Multi-Spectral Solar Telescope Array (MSSTA), rocket-borne
solar observatory, was successfully flown in May, 1991, obtaining
solar images in eight XUV and FUV bands with 12 compact multilayer
telescopes. Extensive measurements have recently been carried out on the
multilayer telescopes and thin film filters at the Stanford Synchrotron
Radiation Laboratory. These measurements are the first high spectral
resolution calibrations of the MSSTA instruments. Previous measurements
and/or calculations of telescope throughputs have been confirmed with
greater accuracy. Results are presented on Mo/Si multilayer bandpass
changes with time and experimental potassium bromide and tellurium
filters.
Title: The Multi-Spectral Solar Telescope Array. II - Soft X-ray/EUV
reflectivity of the multilayer mirrors
Authors: Barbee, Troy W., Jr.; Weed, J. W.; Hoover, Richard B. C., Jr.;
Allen, Max J.; Lindblom, Joakim F.; O'Neal, Ray H.; Kankelborg, Charles
C.; Deforest, Craig E.; Paris, Elizabeth S.; Walker, Arthur B. C.
Bibcode: 1992SPIE.1546..432B
Altcode: 1992SPIE.2011..432B
We have developed seven compact soft X-ray/EUV (XUV) multilayer
coated and two compact FUV interference film coated Cassegrain and
Ritchey-Chretien telescopes for a rocket borne observatory, the
Multi-Spectral Solar Telescope Array. We report here on extensive
measurements of the efficiency and spectral bandpass of the XUV
telescopes carried out at the Stanford Synchrotron Radiation Laboratory.
Title: Narrow band solar images in the soft X-ray regime with
multilayer optics
Authors: Walker, Arthur B. C., Jr.; Kankelborg, Charles C.; Hoover,
Richard B.; Barbee, Troy W., Jr.; Baker, Phillip C.
Bibcode: 1992SPIE.1546..345W
Altcode: 1992SPIE.2011..345W
High quality multilayers with 2d spacings as short as about 44 A have
been used successfully for astronomical observations. Observation of
both the sun and cosmic X-ray sources (for which radiation longward of
the carbon edge at about 44 A is strongly attenuated by interstellar
matter) are possible at wavelengths shorter than 40 A with current
multilayer technology, if mirrors are used at nonnormal angles of
incidence. We discuss several configurations which are suitable for
high resolution solar imaging observations in the wavelength interval
between 0.5 and 50 A. We also describe the design and anticipated
performance of a multilayer optical system we are currently developing
for a rocketborne solar observatory.
Title: Multi-spectral solar telescope array II: Soft X-ray/EUV
reflectivity of the multilayer mirrors.
Authors: Barbee, T. W., Jr.; Weed, J. W.; Hoover, R. B.; Allen,
M. J.; Lindblom, J. F.; O'Neal, R. H.; Kankelborg, C. C.; Deforest,
C. E.; Paris, E. S.; Walker, A. B. C., Jr.; Willis, T. D.; Gluskin,
E.; Pianetta, P.; Baker, P. C.
Bibcode: 1991OptEn..30.1067B
Altcode:
The authors have developed seven compact soft X-ray/EUV (XUV)
multilayer-coated and two compact FUV interference-film-coated
Cassegrain and Ritchey-Chrétien telescopes for a rocket-borne
observatory, the Multi-Spectral Solar Telescope Array. They report on
extensive measurements of the efficiency and spectral bandpass of the
XUV telescopes.
Title: The Ultra High Resolution XUV
Spectroheliograph. Pt. 2. Predicted performance.
Authors: Walker, A. B. C., Jr.; Lindblom, J. F.; Timothy, J. G.;
Allen, M. J.; Deforest, C. E.; Kankelborg, C.; O'Neal, R. H.; Paris,
E. S.; Willis, T.; Barbee, T. W., Jr.; Hoover, R. B.
Bibcode: 1991SPIE.1343..319W
Altcode:
The authors have developed an Ultra High Resolution XUV
Spectroheliograph (UHRXS) for flight among the initial scientific
instruments to be placed on the Space Station "Freedom". The principal
UHRXS instruments are nine multilayer Ritchey-Chrétien telescopes
covering the spectral range from ≡70 Å to ≡300 Å. The XUV images
will be recorded on high resolution photographic film, allowing angular
resolutions as high as 0.1″to be achieved for a 1.0° field. The
authors present an analysis of the expected sensitivity and resolving
power of the UHRXS telescopes, and the diagnostic response of the
various UHRXS instruments to structures in the solar atmosphere between
10,000K and 100,000,000K.
Title: Performance of the Multi-Spectral Solar Telescope Array V:
temperature diagnostic response to the optically thin solar plasma
Authors: Deforest, Craig E.; Kankelborg, Charles C.; Allen, Maxwell
J.; Paris, Elizabeth S.; Willis, Thomas D.; Lindblom, Joakim F.;
O'Neal, Ray H.; Walker, Arthur B.; Barbee, Troy W.; Hoover, Richard
B.; Barbee, Troy W.; Gluskin, Efim S.
Bibcode: 1991SPIE.1343..404D
Altcode:
No abstract at ADS
Title: Performance of compact multilayer coated telescopes at soft
x-ray/EUV and far ultraviolet wavelenghts.
Authors: Hoover, R. B.; Barbee, T. W., Jr.; Baker, P. C.; Lindblom,
J. F.; Allen, M. J.; de Forrest, C.; Kankelborg, C.; O'Neal, R. H.;
Paris, E.; Walker, A. B. C., Jr.
Bibcode: 1990OptEn..29.1281H
Altcode: 1990OptEn..29.1281W
The authors have developed compact soft X-ray/EUV (XUV) and
far-ultraviolet (FUV) multilayer coated telescopes for the study of
the solar chromosphere corona, and corona/solar wind interface. In
this paper they report on the performance of the Ritchey-Chreńtien
telescopes.
Title: Performance of compact multilayer coated telescopes at soft
x-ray/EUV and far-ultraviolet wavelengths I
Authors: Hoover, Richard B.; Barbee, Troy W.; Baker, Phillip C.;
Lindblom, Joakim F.; Allen, Maxwell J.; Deforest, Craig E.; Kankelborg,
Charles C.; O'Neal, Ray H.; Paris, Elizabeth S.; Walker, Arthur B.
Bibcode: 1990SPIE.1235..821H
Altcode:
No abstract at ADS
Title: Multi-Spectral Solar Telescope Array
Authors: Walker, A. B. C., Jr.; Allen, M. J.; Deforest, C.; Kankelborg,
C.; Lindblom, J. F.; O'Neal, R. H.; Paris, E.; Hoover, R. B.; Barbee,
T. W., Jr.
Bibcode: 1990BAAS...22..808W
Altcode:
No abstract at ADS