gary-allen

explanation blue bibcodes open ADS page with paths to full text

Author name code: gary-allen
ADS astronomy entries on 2022-09-14
author:"Gary, G. Allen"

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Title: On the Estimation of the SHARP Parameter MEANALP from AIA
Images Using Deep Neural Networks
Authors: Benson, B.; Pan, W. D.; Prasad, A.; Gary, G. A.; Hu, Q.
2021SoPh..296..163B Altcode:
Space-weather HMI Active Region Patches (SHARPs) data from the
Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics
Observatory (SDO) provides high cadence data from the full-disk
photospheric magnetic field. The SHARP's MEANALP (αm)
parameter, which characterizes the twist, can provide a measure of
nonpotentiality of an active region, which can be a condition for
the occurrence of solar flares. The SDO/Atmospheric Imaging Assembly
(AIA) captures images at a higher cadence (12 or 24 seconds) than the
SDO/HMI. Hence, if the αm can be inferred from the AIA data,
we can estimate the magnetic field evolution of an active region at a
higher temporal cadence. Shortly before a flare occurs, we observed
a change in the αm in some active regions that produced
stronger (M- or X-class) flares. Therefore, we study the ability of
neural networks to estimate the αm parameter from SDO/AIA
images. We propose a classification and regression scheme to train
deep neural networks using AIA filtergrams of active regions with the
objective to estimate the αm of active regions outside
our training set. Our results show a classification accuracy greater
than 85% within two classes to identify the range of the αm
parameter. We also attempt to understand the nature of the solar images
using variational autoencoders. Thus, this study opens a promising new
application of neural networks which can be extended to other SHARP
parameters in the future.

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Title: Forecasting Solar Cycle 25 Using Deep Neural Networks
Authors: Benson, B.; Pan, W. D.; Prasad, A.; Gary, G. A.; Hu, Q.
2020SoPh..295...65B Altcode: 2020arXiv200512406B
With recent advances in the field of machine learning, the use of
deep neural networks for time series forecasting has become more
prevalent. The quasi-periodic nature of the solar cycle makes it a good
candidate for applying time series forecasting methods. We employ a
combination of WaveNet and Long Short-Term Memory neural networks to
forecast the sunspot number using the years 1749 to 2019 and total
sunspot area using the years 1874 to 2019 time series data for the
upcoming Solar Cycle 25. Three other models involving the use of LSTMs
and 1D ConvNets are also compared with our best model. Our analysis
shows that the WaveNet and LSTM model is able to better capture the
overall trend and learn the inherent long and short term dependencies
in time series data. Using this method we forecast 11 years of monthly
averaged data for Solar Cycle 25. Our forecasts show that the upcoming
Solar Cycle 25 will have a maximum sunspot number around 106 ± 19.75
and maximum total sunspot area around 1771 ± 381.17. This indicates
that the cycle would be slightly weaker than Solar Cycle 24.

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Title: Comparison of Two Coronal Magnetic Field Models to Reconstruct
a Sigmoidal Solar Active Region with Coronal Loops
Authors: Duan, Aiying; Jiang, Chaowei; Hu, Qiang; Zhang, Huai; Gary,
G. Allen; Wu, S. T.; Cao, Jinbin
2017ApJ...842..119D Altcode: 2017arXiv170600595D
Magnetic field extrapolation is an important tool to study the
three-dimensional (3D) solar coronal magnetic field, which is difficult
to directly measure. Various analytic models and numerical codes exist,
but their results often drastically differ. Thus, a critical comparison
of the modeled magnetic field lines with the observed coronal loops is
strongly required to establish the credibility of the model. Here we
compare two different non-potential extrapolation codes, a nonlinear
force-free field code (CESE-MHD-NLFFF) and a non-force-free field
(NFFF) code, in modeling a solar active region (AR) that has a
sigmoidal configuration just before a major flare erupted from the
region. A 2D coronal-loop tracing and fitting method is employed to
study the 3D misalignment angles between the extrapolated magnetic
field lines and the EUV loops as imaged by SDO/AIA. It is found that
the CESE-MHD-NLFFF code with preprocessed magnetogram performs the best,
outputting a field that matches the coronal loops in the AR core imaged
in AIA 94 Å with a misalignment angle of ∼10°. This suggests that
the CESE-MHD-NLFFF code, even without using the information of the
coronal loops in constraining the magnetic field, performs as good
as some coronal-loop forward-fitting models. For the loops as imaged
by AIA 171 Å in the outskirts of the AR, all the codes including the
potential field give comparable results of the mean misalignment angle
(∼30°). Thus, further improvement of the codes is needed for a
better reconstruction of the long loops enveloping the core region.

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Title: Determining the 3D Structure of the Corona Using Vertical
Height Constraints on Observed Active Region Loops
Authors: Gary, G. Allen; Hu, Qiang; Lee, Jong Kwan; Aschwanden,
Markus J.
2014SoPh..289.3703G Altcode: 2014SoPh..tmp...87G
The corona associated with an active region is structured by
high-temperature, magnetically dominated closed and open loops. The
projected 2D geometry of these loops is captured in EUV filtergrams. In
this study using SDO/AIA 171 Å filtergrams, we expand our previous
method to derive the 3D structure of these loops, independent of
heliostereoscopy. We employ an automated loop recognition scheme
(Occult-2) and fit the extracted loops with 2D cubic Bézier
splines. Utilizing SDO/HMI magnetograms, we extrapolate the magnetic
field to obtain simple field models within a rectangular cuboid. Using
these models, we minimize the misalignment angle with respect to
Bézier control points to extend the splines to 3D (Gary, Hu, and Lee
2014). The derived Bézier control points give the 3D structure of
the fitted loops. We demonstrate the process by deriving the position
of 3D coronal loops in three active regions (AR 11117, AR 11158, and
AR 11283). The numerical minimization process converges and produces
3D curves which are consistent with the height of the loop structures
when the active region is seen on the limb. From this we conclude that
the method can be important in both determining estimates of the 3D
magnetic field structure and determining the best magnetic model among
competing advanced magnetohydrodynamics or force-free magnetic-field
computer simulations.

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Title: A Small-scale Eruption Leading to a Blowout Macrospicule Jet
in an On-disk Coronal Hole
Authors: Adams, Mitzi; Sterling, Alphonse C.; Moore, Ronald L.; Gary,
G. Allen
2014ApJ...783...11A Altcode:
We examine the three-dimensional magnetic structure and dynamics
of a solar EUV-macrospicule jet that occurred on 2011 February 27
in an on-disk coronal hole. The observations are from the Solar
Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA) and
the SDO Helioseismic and Magnetic Imager (HMI). The observations
reveal that in this event, closed-field-carrying cool absorbing
plasma, as in an erupting mini-filament, erupted and opened,
forming a blowout jet. Contrary to some jet models, there was no
substantial recently emerged, closed, bipolar-magnetic field in the
base of the jet. Instead, over several hours, flux convergence and
cancellation at the polarity inversion line inside an evolved arcade
in the base apparently destabilized the entire arcade, including its
cool-plasma-carrying core field, to undergo a blowout eruption in the
manner of many standard-sized, arcade-blowout eruptions that produce
a flare and coronal mass ejection. Internal reconnection made bright
"flare" loops over the polarity inversion line inside the blowing-out
arcade field, and external reconnection of the blowing-out arcade field
with an ambient open field made longer and dimmer EUV loops on the
outside of the blowing-out arcade. That the loops made by the external
reconnection were much larger than the loops made by the internal
reconnection makes this event a new variety of blowout jet, a variety
not recognized in previous observations and models of blowout jets.

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Title: Erratum: Erratum to: A Rapid, Manual Method to Map Coronal-Loop
Structures of an Active Region Using Cubic Bézier Curves and Its
Applications to Misalignment Angle Analysis
Authors: Gary, G. Allen; Hu, Qiang; Lee, Jong Kwan
2014SoPh..289..867G Altcode:
No abstract at ADS

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Title: A Rapid, Manual Method to Map Coronal-Loop Structures of an
Active Region Using Cubic Bézier Curves and Its Applications to
Misalignment Angle Analysis
Authors: Gary, G. Allen; Hu, Qiang; Lee, Jong Kwan
2014SoPh..289..847G Altcode:
A rapid and flexible manual method is described that maps individual
coronal loops of a 2D EUV image as Bézier curves using only four points
per loop. Using the coronal loops as surrogates of magnetic-field
lines, the mapping results restrict the magnetic-field models
derived from extrapolations of magnetograms to those admissible and
inadmissible via a fitness parameter. We outline explicitly how the
coronal loops can be employed in constraining competing magnetic-field
models by transforming 2D coronal-loop images into 3D field lines. The
magnetic-field extrapolations must satisfy not only the lower boundary
conditions of the vector field (the vector magnetogram) but also
must have a set of field lines that satisfies the mapped coronal
loops in the volume, analogous to an upper boundary condition. This
method uses the minimization of the misalignment angles between the
magnetic-field model and the best set of 3D field lines that match
a set of closed coronal loops. The presented method is an important
tool in determining the fitness of magnetic-field models for the solar
atmosphere. The magnetic-field structure is crucial in determining
the overall dynamics of the solar atmosphere.

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Title: Coronal Loop Mapping to Infer the Best Magnetic Field Models
for Active Region Prominences
Authors: Gary, G. Allen; Hu, Qiang; Lee, Jong Kwan
2014IAUS..300..416G Altcode:
This article comments on the results of a new, rapid, and
flexible manual method to map on-disk individual coronal loops of a
two-dimensional EUV image into the three-dimensional coronal loops. The
method by Gary, Hu, and Lee (2013) employs cubic Bézier splines to
map coronal loops using only four free parameters per loop. A set of 2D
splines for coronal loops is transformed to the best 3D pseudo-magnetic
field lines for a particular coronal model. The results restrict the
magnetic field models derived from extrapolations of magnetograms to
those admissible and inadmissible via a fitness parameter. This method
uses the minimization of the misalignment angles between the magnetic
field model and the best set of 3D field lines that match a set of
closed coronal loops. We comment on the implication of the fitness
parameter in connection with the magnetic free energy and comment on
extensions of our earlier work by considering the issues of employing
open coronal loops or employing partial coronal loop.

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Title: A Small-Scale Filament Eruption Leading to a Blowout
Macrospicule Jet in an On-Disk Coronal Hole
Authors: Sterling, Alphonse C.; Adams, M.; Moore, R. L.; Tennant,
A. F.; Gary, G. A.
2013SPD....44...17S Altcode:
We observe an eruptive jet that occurred in an on-disk solar coronal
hole, using EUV images from the Solar Dynamics Observatory (SDO)
Atmospheric Imaging Assembly (AIA), supplemented by magnetic data from
the SDO Helioseismic and Magnetic Imager (HMI). This jet is similar to
features variously called macrospicules or erupting minifilaments. After
an initial pre-eruptive phase, a concentration of absorbing, cool
material in the AIA images moves with a substantially-horizontal motion
toward a region of open magnetic field, and subsequently jets out along
that vertical field. Prior to and during the jet's ~20 min lifetime,
the magnetic flux integrated over the local region shows flux changes
of &amp;lt 20% of the background flux levels, with a time-averaged
emergence rate of no more than &lt;3 × 10^15 Mx/s in the neighborhood
of the jet. Contrary to some jet models, there was no substantial
recently-emerged bipolar field in the base of the jet. Instead, there
was an established evolving magnetic arcade that held mini-filament-like
cool plasma in its core field. We propose that subtle evolution of the
magnetic flux in and around this arcade destabilized its core field,
as in some standard-sized arcade blowout eruptions that produce a flare
and CME following the slow rise of a standard-sized filament in the
core of the arcade. Closed field carrying the cool plasma erupted into
the open field and formed the blowout jet, evidently at least partly
by interchange reconnection with the open field. Internal reconnection
made compact bright "flare" loops inside the blowing-out arcade, while,
on the outside, interchange reconnection made longer and dimmer EUV
"crinkle" loops. That the loops made by the external reconnection were
considerably larger than the loops made by the internal reconnection
makes this event a new variety of blowout jet, a variety not recognized
in previous observations and models of blowout jets.

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Title: Beckers Effect in a Fabry-Pérot Imaging Interferometer and
Its Effects on Magnetic Field Measurements
Authors: Robinson, Brian; Balasubramaniam, K.; Gary, G.
2012AAS...22020623R Altcode:
The Beckers effect and its impact on the optical performance of a
triple-etalon Fabry-Pérot imaging spectral interferometer, such
as that intended for use in the Advanced Technology Solar Telescope
visible tunable filter, are analyzed in terms of its impacts on line
profiles and spatial resolution. In this multi-etalon design, the
interferometer is mounted in a telecentric beam. The Beckers effect
refers to the pupil apodization in this configuration caused by the
dependence of the spectral transmittance of Fabry-Pérot etalons on the
angle of incidence of impinging rays. We find that the effect on the
imaging and spectral performance can be significant even for the high
F-number intermediate images required for narrowband imaging. We go on
to explore the impact on Stokes line profiles at 6303Å as well as the
cross-talk caused by the degraded point spread function, and analyze
the resultant error in the calculated magnetic fields. We gratefully
acknowledge the National Science Foundation and the National Solar
Observatory for their support of this work.

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Title: Modeling of Magnetic Non-Potentiality of Active Region using
a 3D Data-Driven Active Region Evolution Model: Seeking Necessary
and Sufficient Conditions for Solar Eruption
Authors: Wu, S. T.; Falconer, D.; Hu, Q.; Wang, A.; Gary, G. A.
2012AAS...22020439W Altcode:
One of the major interesting problems for space weather forecasting is
to have the capability of predicting solar eruptive events. To achieve
this goal, we must investigate the evolution of an Active Region. In
this presentation, we will present an investigation of the magnetic
field structures for two productive Active Regions using a data-driven
3D MHD model: AR 10720 of Jan 15, 2005, where the measured magnetic
field from Big Bear Solar Observatory (BBSO) digital vector magnetogram
(DGVM) was used and (ii) AR11117 of October 25, 2010 where the vector
magnetic field are measured by SDO/HMI. The numerical results include
the change of magnetic flux, the net electric current, the length
of magnetic shear of the main neutral line, and the flux normalized
measure of the field twist. From these results we found the above four
non-potential magnetic parameters increase and decrease before and after
solar eruption. In other words, these four parameters are necessary
conditions for solar eruption. Then we reveal a particular feature:
“the fragmented neutral line”. This fragmented neutral line could
be interpreted as the variability of the shear angle (angle between the
observed and potential horizontal field) along the neutral line. It may
be an additional condition for eruption. This suggests that the active
region probability of producing an eruption is not only dependent on
active region free energy but also on the variability of the shear
angle which appears to correspond to the fragmented neutral line.

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Title: Response to “Comment on `Resolving the 180° Ambiguity in
Solar Vector Magnetic Field Data: Evaluating the Effects of Noise,
Spatial Resolution, and Method Assumptions' ”
Authors: Leka, K. D.; Barnes, Graham; Gary, G. Allen; Crouch, A. D.;
Liu, Y.
2012SoPh..276..441L Altcode: 2011arXiv1110.2697L
We address points recently discussed in Georgoulis (2011, Solar Phys.,
doi:10.1007/s11207-011-9819-1) in reference to Leka et al. (2009b,
Solar Phys.260, 83). Most importantly, we find that the results of
Georgoulis (2011) support a conclusion of Leka et al. (2009b): that
limited spatial resolution and the presence of unresolved magnetic
structures can challenge ambiguity-resolution algorithms. Moreover,
the findings of both Metcalf et al. (2006, Solar Phys.237, 267) and
Leka et al. (2009b) are confirmed in Georgoulis (2011): a method's
performance can be diminished when the observed field fails to
conform to that method's assumptions. The implication of boundaries
in models of solar magnetic structures is discussed; we confirm that
the distribution of the field components in the model used in Leka
et al. (2009b) is closer to what is observed on the Sun than what is
proposed in Georgoulis (2011). It is also shown that method does matter
with regards to simulating limited spatial resolution and avoiding an
inadvertent introduction of bias. Finally, the assignment of categories
to data-analysis algorithms is revisited; we argue that assignments
are only useful and elucidating when used appropriately.

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Title: Obituary: Einar A. Tandberg-Hanssen (1921-2011)
Authors: Gary, G.; Emslie, A.; Hathaway, David; Moore, Ronald
2011BAAS...43..032G Altcode:
Dr. Einar Andreas Tandberg-Hanssen was born on 6 August 1921,
in Bergen, Norway, and died on July 22, 2011, in Huntsville, AL,
USA, due to complications from ALS (Amyotrophic lateral sclerosis,
often referred to as Lou Gehrig's disease). His parents were
administrator Birger Tandberg-Hanssen (1883-1951) and secretary Antonie
"Mona" Meier (1895-1967). He married Erna Rönning (27 October
1921 - 22 November 1994), a nurse, on 22 June 1951. She was the
daughter of Captain Einar Rönning (1890-1969) and Borghild Lyshaug
(1897-1980). Einar and Erna had two daughters, Else Biesman (and
husband Allen of Rapid City, SD, USA) and Karin Brock (and husband
Mike of Gulf Shores, AL, USA). At the time of his death Einar had eight
grandchildren and eight great-grandchildren. Dr. Tandberg-Hanssen
was an internationally-known member of the solar physics community,
with over a hundred published scientific papers and several books,
including Solar Activity (1967), Solar Prominences (1974), The
Physics of Solar Flares (1988) and The Nature of Solar Prominences
(1995). Einar grew up in Langesund and Skien, Norway, where he
took the qualifying exams at Skien High School in 1941. After the war
he studied natural sciences at the University of Oslo and received his
undergraduate degree in astronomy in 1950. He worked as a research
assistant in the Institute of Theoretical Astrophysics at the University
of Oslo for three intervals in the 1950s, interspersed by fellowships
at the Institut d'Astrophysique in Paris, Caltech in Pasadena, CA, the
High Altitude Observatory in Boulder, CO, and the Cavendish Laboratory
in the UK (at the invitation of British radio-astronomer Sir Martin
Ryle). He earned a doctorate in astrophysics at the University in
Oslo in 1960 with a dissertation titled "An Investigation of the
Temperature Conditions in Prominences with a Special Study of the
Excitation of Helium." From 1959-61, Tandberg-Hanssen was a
professor at the University in Oslo. He then traveled back to the High
Altitude Observatory in Boulder, Colorado, where he was employed until
1974. He was then employed at the Space Science Laboratory at NASA's
Marshall Space Flight Center (MSFC) in Huntsville, Alabama. There,
he was a Senior Research Scientist and later Deputy Director of the
Laboratory. He served as Lab Director from 1987 until his retirement
from NASA in 1993. He promptly took a part-time post within the Center
for Space Plasma and Aeronomic Research at The University of Alabama
in Huntsville, where he worked until his death. During his tenure
at NASA, he, along with Dr. Mona Hagyard and Dr. S. T. Wu, built up
a substantial, internationally-based group of solar physicists at
MSFC and UA Huntsville. He was a lead investigator on two instruments
aboard NASA spacecraft: the S-056 X-Ray Event Analyzer on the Skylab
Apollo Telescope Mount (which provided pioneering, high-time-cadence
temperature and density information on solar X-ray-emitting regions)
and the Ultraviolet Spectrometer and Polarimeter on the Solar Maximum
Mission (which carried out sweeping new studies of EUV emission from
solar active regions and flares). Dr. Tandberg-Hanssen's books about
various aspects of solar activity, viz.Solar Activity (Blaisdell, 1967),
Solar Prominences (Reidel, 1974), The Physics of Solar Flares (with
A. G. Emslie) (Cambridge, 1988), and The Nature of Solar Prominences
(Reidel, 1995), have become international standard works within the
discipline of solar physics. In 1982, Dr. Tandberg-Hanssen
was elected to membership in the Norwegian Academy of Science
and Letters. From 1979-82 and 1982-85, respectively, he served as
vice-president and president of Commission 10 of the International
Astronomical Union (IAU). He served as president of the Federation of
Astronomical and Geophysical Data Analysis Services from 1990-1994. He
has received the NASA Exceptional Service Medal. He was also a long
time editor of the journal Solar Physics. Dr. Tandberg-Hanssen's
Solar Physics Memoir paper, entitled Solar Prominences - An Intriguing
Phenomenon http://www.springerlink.com/content/1166j74k577kv332/
was published shortly before his death. The article starts with an
autobiographical account, where the author relates how his several
study-trips abroad gradually led him to the study of solar physics
in general, and prominences particularly. Einar's residence
as a research fellow at the Institut d'Astrophysique in Paris in
the 1950s laid the foundation for a lifelong interest in France and
French culture. His great interest in and knowledge of French mediaeval
churches, as well as the Norwegian stave churches, is reflected in two
books, Letters to My Daughters (Ivy House Pub. Group, 2004), and The Joy
of Travel: More Letters to My Daughters (Pentland Press, 2007), which
serve as a review, tourist guide and history book, shaped in the form of
letters home to his two daughters, from his many travels in Norway and
France. Einar was a true gentleman and a true scholar. As evidenced
by his papers, his books, and his dealings with others, he was always
seeking not only to expand his own knowledge and understanding, but also
to find new ways of communicating his remarkable insight to others. He
is survived by his daughters, Else and Karin, and their families.

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Title: Observed Aspects of Reconnection in Solar Eruptions
Authors: Moore, Ronald L.; Sterling, Alphonse C.; Gary, G. Allen;
Cirtain, Jonathan W.; Falconer, David A.
2011SSRv..160...73M Altcode: 2011SSRv..tmp..113M; 2011SSRv..tmp..189M; 2011SSRv..tmp...30M
The observed magnetic field configuration and signatures of reconnection
in the large solar magnetic eruptions that make major flares and coronal
mass ejections and in the much smaller magnetic eruptions that make
X-ray jets are illustrated with cartoons and representative observed
eruptions. The main reconnection signatures considered are the imaged
bright emission from the heated plasma on reconnected field lines. In
any of these eruptions, large or small, the magnetic field that drives
the eruption and/or that drives the buildup to the eruption is initially
a closed bipolar arcade. From the form and configuration of the magnetic
field in and around the driving arcade and from the development of the
reconnection signatures in coordination with the eruption, we infer
that (1) at the onset of reconnection the reconnection current sheet
is small compared to the driving arcade, and (2) the current sheet can
grow to the size of the driving arcade only after reconnection starts
and the unleashed erupting field dynamically forces the current sheet to
grow much larger, building it up faster than the reconnection can tear
it down. We conjecture that the fundamental reason the quasi-static
pre-eruption field is prohibited from having a large current sheet is
that the magnetic pressure is much greater than the plasma pressure
in the chromosphere and low corona in eruptive solar magnetic fields.

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Title: Modeling of Solar Active Region Using Three-Dimensional
Time-Dependent Magnetohydrodynamic (MHD) Simulation
Authors: Hu, Qiang; Wang, A.; Gary, G. A.; Wu, S. T.
2011shin.confE..19H Altcode:
A data-driven, self-consistent, and three-dimensional
magnetohydrodynamic model together with time-dependent boundary
conditions based on the method of characteristics to accommodate
the observations on the photosphere are presented. To illustrate
this model, Active Regions 10720 and 11117 observed by SOHO/MDI and
SDO/HMI, respectively, are chosen for the analyses. Specific physical
parameters are derived and shown to characterize the dynamic evolution
of the active region magnetic field that may play a role leading to
eruptions. Recent development in coronal loop identification that may
help in model validation will also be reported.

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Title: Optimal Pre-Initial Conditions for Data-Driven MHD Simulations
of Solar Active Regions
Authors: Hu, Q.; Wang, A.; Wu, S.; Gary, G. A.
2010AGUFMSH42A..04H Altcode:
With the available high-quality photospheric vector magnetic field
measurements returned by the Solar Dynamics Observatory (SDO), both for
an active region and also possibly on a global scale, we present our
approach of non-force-free extrapolation of the solar coronal magnetic
field from vector magnetograms. In particular, we combine our analysis
with data-driven MHD simulation of solar active regions that utilizes a
vector magnetogram as part of the bottom boundary conditions. We also
derive an approximation for the coronal plasma pressure distribution
based on the extrapolated non-force-free magnetic field. We provide
our extrapolated magnetic field and the corresponding plasma pressure
estimate as initial input to the MHD system. Then several case studies
with different initial plasma pressure estimates are presented. We
show that our extrapolation result is a viable and optimal choice in
terms of agreement with observed photospheric vector magnetogram as
pre-initial conditions for data-driven self-consistent MHD simulation
of solar active regions. We further discuss the potential application
of the combined approach to the dynamic simulation of solar active
region evolution.

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Title: A Combined Approach for Coronal Magnetic Field Modeling
Authors: Hu, Qiang; Wang, A.; Wu, S. T.; Gary, G. A.
2010AAS...21640523H Altcode:
With the expectation of high-quality photospheric vector magnetic
field measurements to be returned by the Solar Dynamics Observatory,
both for a finite active region and also possibly on a global scale,
we present our approach of non-force-free extrapolation of the solar
coronal magnetic field from vector magnetograms. In particular,
we combine our analysis with sophisticated MHD simulations of solar
active regions by providing our extrapolation result as initial input
to the MHD system. We derive an approximation for the coronal plasma
pressure based on the extrapolated non-force-free magnetic field. We
show that our extrapolation result is close to a fully evolved MHD state
through the self-consistent dynamic simulation. We further discuss the
potential application of the method to the full-disk vector magnetic
field measurements to be returned by SDO. QH acknowledges NASA grants
NNX07AO73G and NNX10AG03G for support.

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Title: Non-force-free extrapolation of solar coronal magnetic field
using vector magnetograms
Authors: Hu, Qiang; Dasgupta, B.; Derosa, M. L.; Büchner, J.; Gary,
G. A.
2010JASTP..72..219H Altcode:
We report our recent improvement in non-force-free extrapolation
of coronal magnetic field, using vector magnetograms. Based on the
principle of minimum (energy) dissipation rate (MDR), a generally
non-force-free magnetic field solution is expressed as the superposition
of one potential field and two (constant-[alpha]) linear force-free
fields, with distinct [alpha] parameters. With a known potential field,
the system is reduced to a second-order one that can be solved using
one single-layer vector magnetogram. We devise an iteration procedure
to determine the potential field, by achieving satisfactory agreement
between the MDR-model computed and measured transverse magnetic
field vectors on the bottom boundary. We illustrate this approach by
applying it to real magnetograph measurement of solar active region
AR 10953. We show that the results are satisfactory as judged from
the quantitative magnetic field measurement, and the behavior of the
derived Lorentz force.

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Title: Non-force-free Extrapolation of Coronal Magnetic Field with
Applications to Vector Magnetograms
Authors: Hu, Q.; Wang, A.; Dasgupta, B.; Gary, G. A.; Wu, S.
2009AGUFMSH41B1654H Altcode:
Motivated by increasingly more advanced solar observations, we recently
develop a method of non-force-free extrapolation of the solar coronal
magnetic field from vector magnetograms, especially those for a finite
active region. Based on a more complex variational principle, the
principle of minimum (energy) dissipation rate (MDR), we adopt and
solve a more complex equation governing the coronal magnetic field
that is non-force-free in general. We describe the theoretical basis
in the context of general solar atmosphere conditions, and derive
the extrapolation approach utilizing vector magnetograms as bottom
boundary conditions. We illustrate the approach using both MHD numerical
simulation results, and real vector magnetograph measurements of solar
active regions. We wish to establish the validity of our approach,
especially by detailed inter-comparison with self-consistent, full MHD
simulation results, and investigations of the dynamics associated with
non-vanishing forces.

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Title: Minimum Dissipative Processes in Laboratory and Astrophysical
Plasmas
Authors: Janaki, M. S.; Dasgupta, B.; Hu, Q.; Shaikh, D.; Zank, G. P.;
Gary, G. A.
2009AGUFMNG43A1206J Altcode:
The usual theory of plasma relaxation, based on selective decay
of magnetic energy over the (global) magnetic helicity predicts
a force-free state for a plasma. Such force-free state is often
unrealistic in nature, an alternative theory of relaxation has been
proposed by many authors, which is based on a well-known theorem of
irreversible thermodynamics, principle of minimum entropy production
rate. This is equivalent to minimum dissipation rate of energy. To
demonstrate this, we perform self-consistent, time-dependent numerical
simulations of dissipative plasmas at a higher Landquist number,
typically ~ O(106-107), using full three dimensional compressible
MHD code with a numerical resolution of 1283. Our simulations follow
the time variation of global helicity, magnetic energy, and the
dissipation rate and show that the global helicity remains approximately
constant while magnetic energy is decaying faster and dissipation
rate is decaying even faster than the magnetic energy. Existence of a
perpendicular component of current is also demonstrated. We describe the
application of our model to various laboratory plasma devices, like,
Reversed Field Pinch (RFP) Tokamak, Field Reversed Configurations
(FRC) and Spheromak. Using a two fluid description, we also show
that Solar arcade structures can be modeled as a minimum dissipative
relaxed state, and different types of arcade structures are generated
with the variation of a single parameter characterizing the relaxed
state. Finally, we outline a novel approach to non-force free coronal
magnetic field extrapolation from vector magnetograms.

---------------------------------------------------------
Title: Resolving the 180° Ambiguity in Solar Vector Magnetic
Field Data: Evaluating the Effects of Noise, Spatial Resolution,
and Method Assumptions
Authors: Leka, K. D.; Barnes, Graham; Crouch, A. D.; Metcalf, Thomas
R.; Gary, G. Allen; Jing, Ju; Liu, Y.
2009SoPh..260...83L Altcode:
The objective testing of algorithms for performing ambiguity
resolution in vector magnetic field data is continued, with an
examination of the effects of noise in the data. Through the use
of analytic magnetic field models, two types of noise are "added"
prior to resolving: noise to simulate Poisson photon noise in the
observed polarization spectra, and a spatial binning to simulate the
effects of unresolved structure. The results are compared through
the use of quantitative metrics and performance maps. We find that
while no algorithm severely propagates the effects of Poisson noise
beyond very local influences, some algorithms are more robust against
high photon-noise levels than others. In the case of limited spatial
resolution, loss of information regarding fine-scale structure can
easily result in erroneous solutions. Our tests imply that photon
noise and limited spatial resolution can act so as to make assumptions
used in some ambiguity resolution algorithms no longer consistent
with the observed magnetogram. We confirm a finding of the earlier
comparison study that results can be very sensitive to the details of
the treatment of the observed boundary and the assumptions governing
that treatment. We discuss the implications of these findings, given the
relative sensitivities of the algorithms to the two sources of noise
tested here. We also touch on further implications for interpreting
observational vector magnetic field data for general solar physics
research.

---------------------------------------------------------
Title: The "Main Sequence" of Explosive Solar Active Regions:
Discovery and Interpretation
Authors: Falconer, David A.; Moore, Ronald L.; Gary, G. Allen;
Adams, Mitzi
2009ApJ...700L.166F Altcode:
We examine the location and distribution of the production of coronal
mass ejections (CMEs) and major flares by sunspot active regions
in the phase space of two whole-active-region magnetic quantities
measured from 1897 SOHO/MDI magnetograms. These magnetograms track the
evolution of 44 active regions across the central disk of radius 0.5
R Sun. The two quantities are LWLSG,
a gauge of the total free energy in an active region's magnetic field,
and LΦ, a measure of the active region's total magnetic
flux. From these data and each active region's history of production
of CMEs, X flares, and M flares, we find (1) that CME/flare-productive
active regions are concentrated in a straight-line "main sequence"
in (log LWLSG, log LΦ) space, (2)
that main-sequence active regions have nearly their maximum attainable
free magnetic energy, and (3) evidence that this arrangement plausibly
results from equilibrium between input of free energy to an explosive
active region's magnetic field in the chromosphere and corona by
contortion of the field via convection in and below the photosphere
and loss of free energy via CMEs, flares, and coronal heating, an
equilibrium between energy gain and loss that is analogous to that of
the main sequence of hydrogen-burning stars in (mass, luminosity) space.

---------------------------------------------------------
Title: Evaluation of a Selected Case of the Minimum Dissipative Rate
Method for Non-Force-Free Solar Magnetic Field Extrapolations
Authors: Gary, G. Allen
2009SoPh..257..271G Altcode:
The minimum dissipative rate (MDR) method for deriving a coronal
non-force-free magnetic field solution is partially evaluated. These
magnetic field solutions employ a combination of three linear
(constant-α) force-free-field solutions with one being a potential
field (i.e., α=0). The particular case of the solutions where the other
two α's are of equal magnitude but of opposite sign is examined. This
is motivated by studying the SOLIS (Synoptic Optical Long-term
Investigation of the Sun (SOLIS), a National Solar Observatory facility)
vector magnetograms of AR 10987, which show a global α value consistent
with an α=0 value as evaluated by (∇×B)z/Bz
over the region. Typical of the current state of the observing
technology, there is no definitive twist for input into the general MDR
method. This suggests that the special α case, of two α's with equal
magnitudes and opposite signs, is appropriate given the data. Only
for an extensively twisted active region does a dominant, nonzero α
normally emerge from a distribution of local values. For a special set
of conditions, is it found that (i) the resulting magnetic field is a
vertically inflated magnetic field resulting from the electric currents
being parallel to the photosphere, similar to the results of Gary and
Alexander (Solar Phys. 186:123, 1999), and (ii) for α≈(αmax
/2), the Lorentz force per unit volume normalized by the square
of the magnetic field is on the order of 1.4×10−10
cm−1. The Lorentz force (FL) is a factor of
ten higher than that of the magnetic force d(B2/8π)/dz,
a component of FL. The calculated photospheric electric
current densities are an order of magnitude smaller than the maximum
observed in all active regions. Hence both the Lorentz force density and
the generated electric current density seem to be physically consistent
with possible solar dynamics. The results imply that the field could
be inflated with an overpressure along the neutral line. However,
the implementation of this or any other extrapolation method using
the electric current density as a lower boundary condition must be
done cautiously, with the current magnetography.

---------------------------------------------------------
Title: Analyses of magnetic field structures for active region 10720
using a data-driven 3D MHD model
Authors: Wu, S. T.; Wang, A. H.; Gary, G. Allen; Kucera, Ales; Rybak,
Jan; Liu, Yang; Vrśnak, Bojan; Yurchyshyn, Vasyl
2009AdSpR..44...46W Altcode:
In order to understand solar eruptive events (flares and CMEs) we
need to investigate the changes at the solar surface. Thus, we use
a data-driven, three-dimensional magnetohydrodynamic (MHD) model to
analyze a flare and coronal mass ejection productive active region,
AR 10720 on January 15, 2005. The measured magnetic field from Big
Bear Solar Observatory (BBSO) digital vector magnetograph (DGVM) was
used to model the non-potential coronal magnetic field changes and the
evolution of electric current before and after the event occurred. The
numerical results include the change of magnetic flux ( Φ), the net
electric current ( IN), the length of magnetic shear of the
main neutral line ( Lss), the flux normalized measure of
the field twist (α={μIN}/{Φ}) with μ being the magnetic
permeability. The current helicity ( Hc) injected into the
corona and the photospheric surface velocity are also computed. The
characteristic parameters of the buildup process before the event and
the decay process after the event are investigated and the amount of
magnetic energy converted to drive the event is estimated.

---------------------------------------------------------
Title: The "Main Sequence” of Explosive Solar Active Regions:
Discovery and Interpretation
Authors: Falconer, David; Moore, R. L.; Gary, G. A.; Adams, M.
2009SPD....40.1925F Altcode:
We examine the location and distribution of the production of coronal
mass ejections (CMEs) and major flares by sunspot active regions in
the phase space of two whole-active-region magnetic quantities measured
from 1865 SOHO/MDI magnetograms. These magnetograms track the evolution
of 44 full-grown active regions across the central disk of radius 0.5
RSun. The two quantities are LWLSG,
a gauge of the total free energy in an active region's magnetic
field above the photosphere, and LΦ, a measure of the
active region's total magnetic flux. We compiled each active region's
production of CMEs, X flares, and M flares during its rotation across
the disk. In addition, at the time of each magnetogram, we evaluated
from the NOAA Catalog of Active Region Flares a flare-power measure, the
active region's 48-hour average power output in 1-8 Å radiation from
X and M flares. From these data, we find that (1) CME/flare-productive
active regions are concentrated in a straight-line "main sequence” in
(Log LWLSG, Log LΦ) space, (2) this
line is close behind a front of maximum attainable magnetic twist, and
(3) the average flare-power measure increases sharply across this line
as the leading front is approached. These results suggest that the main
sequence of explosive active regions is the consequence of equilibrium
between input of free energy by contortion of the field via convection
in and below the photosphere and loss of free energy via CMEs, flares,
and coronal heating, an equilibrium between energy gain and loss
that is analogous to that of the main sequence of hydrogen-burning
stars in Mass-Luminosity space. This work was funded by NASA's
LWS TR&amp;T Program, NSF's SHINE Program, AFOSR's MURI Program,
and NASA's Technical Excellence Initiative Program.

---------------------------------------------------------
Title: Future possibilities for doppler and magnetic field
measurements in the extended solar atmosphere: Dissecting the
transition region
Authors: Gary, G. Allen; Davis, John M.; West, Edward A.
2009AdSpR..43...96G Altcode:
For the first time, a vacuum ultraviolet (VUV) telescope can be built
to rapidly observe the magnetic fields, plasma flows, and heating
events in the Sun’s atmosphere. These observations can provide key
data for space weather models. The vacuum ultraviolet region allows
remote sensing of the upper levels of the solar atmosphere where the
magnetic field dominates the physics. A VUV Fabry-Pérot interferometer
(FPI) will allow us to observe the magnetic field, flows, and heating
events in the mid-transition region (between the chromosphere and
corona). Observations of this region are needed to directly probe the
magnetic structure and activity at the base of the corona where the
magnetic field is approximately force-free, i.e., where gas pressures
are very small. This is a key element in developing accurate models of
the Sun’s dynamics for space weather. The specific region of interest
is the 100 km thick transition region, between the chromosphere and
the much hotter corona, which strongly emits at 155 nm from triply
ionized carbon (C3+) at 100,000 K. This is best observed
by an imaging interferometer that combines the best attributes of
a spectrograph and an imager. We present the latest results from the
NASA Marshall Space Flight Center (MSFC) FPI. The major elements of the
tunable CIV VUV FPI are the 35 mm MgF2 etalon plates with a
plate finesse of F&gt;25 at 155 nm, the π-dielectric coatings, a Hansen
mechanical mount in a pressurize canister, and the piezoelectric control
system. The control system for the etalon is a capacitance-stabilized
Hovemere Ltd. standard system. The special Cascade Optical Corporation
reflectance coatings are 25 pi-multilayers of high low refractive layers
paired in phase. This CIV interferometer, when flown above Earth’s
atmosphere, will obtain narrow-passband images, magnetograms, and
Dopplergrams of the transition region in the CIV 155 nm line at a rapid
cadence. We recently measured the MSFC VUV FPI using the University
of Toronto’s fluoride excimer laser as a proxy for CIV 155 nm. The
test demonstrated the first tunable interferometer with the passband
required for a VUV filter magnetograph. The measured values have a
full-width half-maximum (FWHM) passband of 10 pm, a free-spectral range
(FSR) of 61 pm, and a transmittance of 58% at 157 nm. The resulting VUV
interferometer finesse is 5.9. With this success, we are developing an
instrument suitable for a flight on an orbiting solar observatory. A
description of the interferometer for this mission is described.

---------------------------------------------------------
Title: Magnetogram Measures of Total Nonpotentiality for Prediction
of Solar Coronal Mass Ejections from Active Regions of Any Degree
of Magnetic Complexity
Authors: Falconer, D. A.; Moore, R. L.; Gary, G. A.
2008ApJ...689.1433F Altcode:
For investigating the magnetic causes of coronal mass ejections
(CMEs) and for forecasting the CME productivity of active regions,
in previous work we have gauged the total nonpotentiality of a
whole active region by either of two measures, LSSM
and LSGM, two measures of the magnetic field along the
main neutral line in a vector magnetogram of the active region. This
previous work was therefore restricted to nominally bipolar active
regions, active regions that have a clearly identifiable main neutral
line. In the present paper, we show that our work can be extended
to include multipolar active regions of any degree of magnetic
complexity by replacing LSSM and LSGM with their
generalized counterparts, WLSS and WLSG, which
are corresponding integral measures covering all neutral lines in an
active region instead of only the main neutral line. In addition, we
show that for active regions within 30 heliocentric degrees of disk
center, WLSG can be adequately measured from line-of-sight
magnetograms instead of vector magnetograms. This approximate measure
of active-region total nonpotentiality,LWLSG,
with the extensive set of 96 minute cadence full-disk line-of-sight
magnetograms from SOHO MDI, can be used to study the evolution of
active-region total nonpotentiality leading to the production of CMEs.

---------------------------------------------------------
Title: Analyses of Hinode Magnetic Field Observations Using a 3D
MHD Model
Authors: Gary, G. A.; Wu, S. T.; Wang, A. H.
2008ASPC..397..167G Altcode:
A data-driven 3D MHD model (Wu et al. 2006) is used to investigate
the sources of solar eruptive events. As an example, the Hinode data
on 12 December 2006 (AR 10930) have been used to deduce the physical
parameters before and after the observed flare. These parameters
including the main length of strong magnetic shear and strong transverse
field L_{ss} and current helicity. The 3D magnetic field lines are
drawn and show the field topology before the flare. These are very
preliminary results, and further study is needed for correlation
between an active region configuration and an eruptive phenomenon.

---------------------------------------------------------
Title: Anatomy of the Solar Ultraviolet Magnetograph Investigation
Sounding Rocket
Authors: Abunaemeh, M. A.; Cirtain, J.; Kobayashi, K.; Winebarger,
A. R.; West, E. A.; Davis, J. M.; Gary, G. A.
2008AGUSMSP51B..01A Altcode:
A major focus of solar physics is to understand how the solar magnetic
field stores and releases the energy that drives the dynamic phenomena
of the outer atmosphere, namely flares and coronal mass ejections
(CMEs). A crucial element in our current knowledge is how the field
evolves as it changes from being pressure-dominated in the photosphere
to being force-free in the corona. There have been ways to study
the evolution indirectly by extrapolation or through morphology,
but direct and quantitative measurements of magnetic field strength
in the force-free corona is difficult and few attempts have ever been
made. The Solar Ultraviolet Magnetograph Investigation (SUMI) sounding
rocket has been developed by NASA Marshall Space and Flight Center
(MSFC)and National Space and Science Center (NSSTC) to measure the
linear and circular polarization of magnetically sensitive 280nm Mg
II line and also to measure the circular polarization of the 155nm C
IV emission lines originating in this force-free region. SUMI uses a
Ritchey-Chretien telescope design with dielectric coating applied to the
front surfaces of both telescope mirrors for the purpose of decreasing
the thermal load. The out-of-band radiation is transmitted and then
reflected out of the telescope. The polarimeter consists of a MgF2
rotatable waveplate and a double Wollaston polarizing beamsplitter. The
waveplate is designed to measure the circular polarization at C IV
(270° retardance at 155nm) and a full Stokes vector at Mg II (131°
retardance at 280nm). SUMI measures both orthogonal polarizations in
both C IV and Mg II simultaneously. Two toroidal varied-line-spacing
(TVLS) grating are used, one for each polarization. There are two
Mg II cameras, one for each polarization, and one C IV camera that
captures both polarizations. All cameras use back- illuminated CCDs
with measured quantum efficiency of more than 60%. SUMI is in the last
stage of alignment and system testing and is expected to be launched
in summer 2008. This SUMI result will be an essential complement to
visible-light magnetographs for understanding how magnetic energy
stored in a sheared field region is released in flares and CMEs. We
will be describing the anatomy of the SUMI sounding rocket and the
detector test and calibration program and the NASA/MFSC and NSSTC
facilities where the instrument is being developed.

---------------------------------------------------------
Title: The "Main Sequence" of Explosive Solar Active Regions:
Discovery and Interpretation
Authors: Falconer, D.; Moore, R.; Gary, G. A.
2008AGUSMSP24A..07F Altcode:
From ~ 2000 MDI magnetograms of 44 evolving active regions within
30 heliocentric degrees of disk center, we measured active-region
magnetic size and total nonpotentiality. Besides displaying the upper
limit on active- region size above which the sun rarely produces
active regions and the lower limit on active-region size below which
a magnetic flux concentration is not an active region, we discovered
that active-region total nonpotentiality has an upper bound that
increases with active-region magnetic size. For a given size, an active
region can have only so much total nonpotentiality. We show that this
limit amounts to an upper bound on a particular measure of an active
region's nonpotentiality per unit flux, that is, an upper bound on a
flux-normalized measure of an active region's nonpotentiality. This
limit plausibly represents an upper bound on the overall degree of
twist in an active region's magnetic field. If so, an active region's
magnetic twist can increase to this limit but go no further. After being
near the limit for a while the active region can loose nonpotentiality
and retreat from the limit. Albeit entirely different physics, this
evolution is analogous to how stars evolve to the main sequence,
stay there a while and then evolve away from it. Unlike the stellar
evolution path, an active region can evolve to its limit multiple
times. We present evidence that what is enforcing this upper limit on
flux-normalized nonpotentiality is that as an active region's magnetic
field becomes more twisted, it more rapidly releases energy in the form
of flares and CMEs. When an active region's energy-burn-down rate by
flares and CMEs equals the rate of buildup of its nonpotential energy,
it can get no more nonpotential. The upper limit on flux- normalized
nonpotentiality is determined by the burn-down rate dependence on the
flux-normalized nonpotentiality and an upper limit on how rapidly an
active region's nonpotentiality can buildup. This work is funded by
the NASA LWS TR&amp;T Program, by the NSF SHINE Program, by the AFOSR
MURI Program, and by the NASA Technical Excellence Initiative.

---------------------------------------------------------
Title: Comparison of Five Numerical Codes for Automated Tracing of
Coronal Loops
Authors: Aschwanden, Markus J.; Lee, Jong Kwan; Gary, G. Allen; Smith,
Michael; Inhester, Bernd
2008SoPh..248..359A Altcode:
The three-dimensional (3D) modeling of coronal loops and filaments
requires algorithms that automatically trace curvilinear features in
solar EUV or soft X-ray images. We compare five existing algorithms
that have been developed and customized to trace curvilinear features
in solar images: i) the oriented-connectivity method (OCM), which is
an extension of the Strous pixel-labeling algorithm (developed by Lee,
Newman, and Gary); ii) the dynamic aperture-based loop-segmentation
method (developed by Lee, Newman, and Gary); iii) unbiased detection of
curvilinear structures (developed by Steger, Raghupathy, and Smith); iv)
the oriented-direction method (developed by Aschwanden); and v) ridge
detection by automated scaling (developed by Inhester). We test the
five existing numerical codes with a TRACE image that shows a bipolar
active region and contains over 100 discernable loops. We evaluate the
performance of the five codes by comparing the cumulative distribution
of loop lengths, the median and maximum loop length, the completeness
or detection efficiency, the accuracy, and flux sensitivity. These
algorithms are useful for the reconstruction of the 3D geometry of
coronal loops from stereoscopic observations with the STEREO spacecraft,
or for quantitative comparisons of observed EUV loop geometries with
(nonlinear force-free) magnetic field extrapolation models.

---------------------------------------------------------
Title: Future Possibilities for Doppler and Magnetic Field
Measurements in the Extended Solar Atmosphere
Authors: Gary, Gilmer Allen; Davis, John M.; West, Edward A.; Gary,
Gilmer Allen
2008cosp...37..978G Altcode: 2008cosp.meet..978G
For the first time, a vacuum ultraviolet telescope can be built to
observe magnetic fields, plasma flows, and heating events in the Sun's
atmosphere. These observations can provide key data for space weather
models. The vacuum ultraviolet (VUV) region allows remote sensing of
the upper levels of the solar atmosphere where the magnetic field
dominates the physics. A VUV Fabry- Perot interferometer (FPI)
will allow us to observe the magnetic field, flows, and heating
events in the mid-transition region (between the chromosphere and
corona). Observations of this region are needed to directly probe the
magnetic structure and activity at the base of the corona where the
magnetic field is approximately force-free, i.e., where gas pressures
are very small. This is a key element in developing accurate models of
the Sun's dynamics for space weather. The specific region of interest
is the 100km-thick transition region, between the chromosphere and
the much hotter corona. This region radiates strongly at 155 nm from
the triply ionized carbon (CIV) lines formed at 100,000 K. The region
is best studied using an imaging interferometer that combines the
best attributes of a spectrograph and an imager. The major elements
of the NASA Marshall Space Flight Center (MSFC) tunable CIV VUV FP
interferometer are the 35mm magnesium fluoride etalon plates with
a plate finesse of F greater than 25 at 155 nm, the pi-dielectric
coatings, a Hansen mechanical mount in a pressurize canister, and the
piezoelectric control system. The control system for the etalon is
a capacitance-stabilized Hovemere Ltd. standard system. The special
Cascade Optical Corporation reflectance coatings are 25 pimultilayers
of high-low refractive layers paired in phase. We recently measured
the MSFC VUV FPI using the University of Toronto's fluoride excimer
laser as a proxy for the CIV 155nm line. The test demonstrated that
the tunable interferometer possessed the passband required for a VUV
filter magnetograph. The measured values have a full-width half-maximum
(FWHM) passband of 10pm, a free-spectral range (FSR) of 61 pm, and a
transmittance of 58 percent at 157 nm. The resulting VUV interferometer
finesse is 5.9. With this successful demonstration, we have proposed a
Small Explorer mission that will obtain rapid cadence, narrow-passband
images, magnetograms, and Dopplergrams of the transition region in the
CIV 155 nm line. The observations will be used to conduct studies of the
evolution of the solar magnetic field from non-force free conditions
in the photosphere to nearly force free conditions in the transition
region and its role in coronal heating and solar flares.

---------------------------------------------------------
Title: Evolution strategies optimization of the multiple Fabry-Perót
imaging interferometer for the advanced technology solar telescope
Authors: Robinson, Brian; Gary, G. Allen; Balasubramaniam, K. S.
2008OptEn..47j3002R Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Solar confocal interferometers for sub-picometer-resolution
spectral filters
Authors: Gary, G. A.; Pietraszewski, C.; West, E. A.; Dines, T. C.
2007A&A...467..375G Altcode:
Aims:The confocal Fabry-Pérot interferometer allows sub-picometer
spectral resolution of Fraunhofer line profiles. Such high spectral
resolution is needed to keep pace with the higher spatial resolution
of the new set of large-aperture solar telescopes. The line-of-sight
spatial resolution derived for line profile inversions would then track
the improvements of the transverse spatial scale provided by the larger
apertures. In particular, profile inversion allows improved velocity
and magnetic field gradients to be determined independent of multiple
line analysis using different energy levels and ions. The confocal
interferometer's unique properties allow a simultaneous increase
in both étendue and spectral power. The higher throughput for the
interferometer provides significant decrease in the aperture, which
is important in spaceflight considerations. Methods: We have
constructed and tested two confocal interferometers. A slow-response
thermal-controlled interferometer provides a stable system for
laboratory investigation, while a piezoelectric interferometer provides
a rapid response for solar observations. Results: In this paper
we provide design parameters, show construction details, and report
on the laboratory test for these interferometers. The field of view
versus aperture for confocal interferometers is compared with other
types of spectral imaging filters. We propose a multiple etalon system
for observing with these units using existing planar interferometers
as pre-filters. The radiometry for these tests established that high
spectral resolution profiles can be obtained with imaging confocal
interferometers. These sub-picometer spectral data of the photosphere
in both the visible and near-infrared can provide important height
variation information. However, at the diffraction-limited spatial
resolution of the telescope, the spectral data is photon starved due
to the decreased spectral passband.

---------------------------------------------------------
Title: Forecasting coronal mass ejections from line-of-sight
magnetograms
Authors: Falconer, D. A.; Moore, R. L.; Gary, G. A.
2007JASTP..69...86F Altcode: 2007JATP...69...86F
We show that the length of strong-gradient, strong-field main neutral
line, LSGM, which can be measured from line-of-sight
magnetograms such as from SOHO/MDI, is both a measure of active-region
nonpotentiality and a useful predictor of an active region's future
Coronal mass ejections (CME) productivity. To demonstrate that
LSGM is a nonpotentiality measure, we show that it is
strongly correlated with a direct measure of nonpotentiality. For an
appropriate choice of a threshold value, an active region's measured
LSGM can be used as a predictor of whether the active
region will produce a CME within a few days after the magnetogram. For
our set of 36 Marshall Space Flight CentreMSFC vector magnetograms of
bipolar active regions, LSGM is found to have a success rate
of 80% for prediction of CME productivity in the 0 2 day window. The
development of LSGM as a method of measuring nonpotentiality
for forecasting large, fast CMEs from present space-based assets is
of value to NASA's space exploration initiative (manned missions to
the Moon and Mars).

---------------------------------------------------------
Title: Solar CIV vacuum-ultraviolet Fabry-Perot interferometers
Authors: Gary, G. A.; West, E. A.; Rees, D.; McKay, J. A.; Zukic,
M.; Herman, P.
2007A&A...461..707G Altcode:
Aims:A tunable, high spectral resolution, high effective finesse,
vacuum ultraviolet (VUV) Fabry-Perot interferometer (FPI) is designed
for obtaining narrow-passband images, magnetograms, and Dopplergrams
of the transition region emission line of CIV (155 nm). Methods:
The integral part of the CIV narrow passband filter package (with a 2-10
pm FWHM) consists of a multiple etalon system composed of a tunable
interferometer that provides high-spectral resolution and a static
low-spectral resolution interferometer that allows a large effective
free spectral range. The prefilter for the interferometers is provided
by a set of four mirrors with dielectric high-reflective coatings. A
tunable VUV piezoelectric-control interferometer has undergone testing
using the surrogate F{2} eximer laser line at 157 nm for the CIV
line. We present the results of these tests with a description of the
overall concept for a complete narrow-band CIV spectral filter. The
static interferometer of the filter will be built using a set of fixed
MgF{2} plates. The four-mirror prefilter is designed to have dielectric
multilayer Π-stacks employing the concept used in the Ultraviolet
Imager of NASA's Polar Spacecraft. A 10-pm dual etalon system allows
the effective free spectral range to be commensurate with the prefilter
profile. With an additional etalon, a triple etalon system would allow
a spectrographic resolution of 2 pm. The basic strategy has been to
combine the expertise of spaceflight etalon manufacturing with VUV
coating technology to build a VUV FPI which combines the best attributes
of imagers and spectrographs into a single compact instrument. Results: High spectral-resolution spectro-polarimetry observations
of the transition region CIV emission can be performed to increase
our understanding of the magnetic forces, mass motion, evolution, and
energy release within the solar atmosphere at the base of the corona
where most of the magnetic field is approximately force-free. The 2D
imaging of the full vector magnetic field at the height of maximum
magnetic influence (minimum plasma beta) can be accomplished, albeit
difficult, by measuring the Zeeman splitting of the CIV resonance
pair. Designs of multiple VUV FPIs can be developed for integration
into future orbiting solar observatories to obtain rapid cadence,
spectral imaging of the transition region.

---------------------------------------------------------
Title: C IV Vacuum Ultraviolet Fabry-Perot Interferometers for
Transition-Region Magnetography
Authors: Gary, G. A.; West, E. A.; Rees, D. E.; Zukic, M.; Herman,
P.; Li, J.
2006ASPC..358..181G Altcode:
The vacuum ultraviolet region allows remote sensing of the upper
levels of the solar atmosphere where the magnetic field dominates
the physics. Obtaining an imaging interferometer that observes the
transition region is the goal of this program. This paper gives
a summary of our instrument development program (1998-2005) for a
high-spectral-resolution, piezoelectric tunable Vacuum Ultraviolet
Fabry-Perot Interferometer (VUV FPI) for obtaining narrow-passband
images, magnetograms, and Dopplergrams of the transition region emission
line of C IV (155 nm). A VUV interferometer will allow us to observe
the magnetic field, flows, and heating events in the mid-transition
region. The MSFC VUV FPI has measured values of FWHM ∼ 9 pm,
FSR ∼ 62 pm, finesse ∼5.3, and transmittance ∼ 50% at 157
nm. For the measurements, the University of Toronto's F2
eximer laser was used as an appropriate proxy for C IV 155 nm. This
has provided the first tunable interferometer with a FWHM compatible
to VUV filter magnetograph.

---------------------------------------------------------
Title: Large Field-of-View KD*P Modulator for Solar Polarization
Measurements
Authors: West, E. A.; Gary, G. A.
2006ASPC..358..209W Altcode:
This paper describes the evolution of the Marshall Space Flight
Center's (MSFC) electro-optical polarimeter with emphasis on the
field-of-view characteristics of the KD*P modulator. Understanding those
characteristics was essential to the success of the MSFC solar vector
magnetograph. We show how the field-of-view (FOV) errors of KD*P look
similar to the linear polarization patterns seen in simple sunspots,
and why the placement of the KD*P in a collimated beam was essential in
separating the instrumental polarization from the solar signal. Finally,
we describe a modulator design which minimizes those FOV errors.

---------------------------------------------------------
Title: 3-D Structure of Sunspots Using Imaging Spectroscopy
Authors: Balasubramaniam, K. S.; Gary, G. A.; Reardon, K.
2006ASPC..354..237B Altcode:
We use the Interferometric BIdimensional Spectrometer (IBIS) of the
INAF/Arcetri Astrophysical Observatory and installed at the National
Solar Observatory (NSO) Dunn Solar Telescope, to understand the
structure of sunspots. Using the spectral lines Fe I 6301.5 Å, Fe II
7224.4 Å, and Ca II 8542.6 Å, we examine the spectroscopic variation
of sunspot penumbral and umbral structures at the heights of formation
of these lines. These high resolution observations were acquired on
2004 July 30 -- 31, of active region NOAA 10654, using the high order
NSO adaptive optics system. We map the spatio-temporal variation of
Doppler signatures in these spectral lines, from the photosphere to
the chromosphere. From a 70-minute temporal average of individual
32-second cadence Doppler observations we find that the averaged
velocities decrease with height. They are about 3.5 times larger in the
deeper photosphere (Fe II 7224.4 Å; height-of-formation ≈ 50 km)
than in the upper photosphere Fe I 6301.5 Å; height-of-formation
≈ 350 km), There is a remarkable coherence of Doppler signals
over the height difference of 300 km. From a high-speed animation
of the Doppler sequence we find evidence for what appears to be
ejection of high speed gas concentrations from edges of penumbral
filaments into the surrounding granular photosphere. The Evershed
flow persists a few arcseconds beyond the traditionally demarcated
penumbra-granulation boundary. We present these and other results and
discuss the implications of these measurements for sunspot models.

---------------------------------------------------------
Title: The Solar Ultraviolet Magnetograph Investigation: Polarization
Properties
Authors: West, E. A.; Kobayashi, K.; Gary, G. A.; Davis, J. M.
2006ASPC..358..161W Altcode:
This paper describes the objectives of the Marshall Space Flight
Center (MSFC) Solar Ultraviolet Magnetograph Investigation (SUMI)
and the optical components that have been developed to meet those
objectives. A sounding rocket payload is being developed to test the
feasibility of magnetic-field measurements in the Sun's transition
region. The optics have been optimized for simultaneous measurements
of two magnetic lines formed in the transition region (C IV 1550 Å
and Mg II 2800 Å). Finally, we illustrate the polarization properties
of the SUMI polarimeter and toroidal variable-line-space gratings.

---------------------------------------------------------
Title: An Overview of Existing Algorithms for Resolving the
180° Ambiguity in Vector Magnetic Fields: Quantitative
Tests with Synthetic Data
Authors: Metcalf, Thomas R.; Leka, K. D.; Barnes, Graham; Lites,
Bruce W.; Georgoulis, Manolis K.; Pevtsov, A. A.; Balasubramaniam,
K. S.; Gary, G. Allen; Jing, Ju; Li, Jing; Liu, Y.; Wang, H. N.;
Abramenko, Valentyna; Yurchyshyn, Vasyl; Moon, Y. -J.
2006SoPh..237..267M Altcode: 2006SoPh..tmp...14M
We report here on the present state-of-the-art in algorithms used
for resolving the 180° ambiguity in solar vector magnetic field
measurements. With present observations and techniques, some assumption
must be made about the solar magnetic field in order to resolve
this ambiguity. Our focus is the application of numerous existing
algorithms to test data for which the correct answer is known. In
this context, we compare the algorithms quantitatively and seek to
understand where each succeeds, where it fails, and why. We have
considered five basic approaches: comparing the observed field to a
reference field or direction, minimizing the vertical gradient of the
magnetic pressure, minimizing the vertical current density, minimizing
some approximation to the total current density, and minimizing some
approximation to the field's divergence. Of the automated methods
requiring no human intervention, those which minimize the square of
the vertical current density in conjunction with an approximation for
the vanishing divergence of the magnetic field show the most promise.

---------------------------------------------------------
Title: Magnetic Causes of Solar Coronal Mass Ejections: Dominance
of the Free Magnetic Energy over the Magnetic Twist Alone
Authors: Falconer, D. A.; Moore, R. L.; Gary, G. A.
2006ApJ...644.1258F Altcode:
We examine the magnetic causes of coronal mass ejections (CMEs)
by examining, along with the correlations of active-region magnetic
measures with each other, the correlations of these measures with
active-region CME productivity observed in time windows of a few days,
either centered on or extending forward from the day of the magnetic
measurement. The measures are from 36 vector magnetograms of bipolar
active regions observed within ~30° of disk center by the Marshal
Space Flight Center (MSFC) vector magnetograph. From each magnetogram,
we extract six whole-active-region measures twice, once from the
original plane-of-the-sky magnetogram and again after deprojection of
the magnetogram to disk center. Three of the measures are alternative
measures of the total nonpotentiality of the active region, two are
alternative measures of the overall twist in the active-region's
magnetic field, and one is a measure of the magnetic size of the
active region (the active region's magnetic flux content). From the
deprojected magnetograms, we find evidence that (1) magnetic twist and
magnetic size are separate but comparably strong causes of active-region
CME productivity, and (2) the total free magnetic energy in an active
region's magnetic field is a stronger determinant of the active region's
CME productivity than is the field's overall twist (or helicity)
alone. From comparison of results from the non-deprojected magnetograms
with corresponding results from the deprojected magnetograms, we find
evidence that (for prediction of active-region CME productivity and for
further studies of active-region magnetic size as a cause of CMEs),
for active regions within ~30° of disk center, active-region total
nonpotentiality and flux content can be adequately measured from
line-of-sight magnetograms, such as from SOHO MDI.

---------------------------------------------------------
Title: Imaging Spectroscopy Of Sunspots Using IBIS
Authors: Balasubramaniam, K. S.; Gary, G. A.; Reardon, K.
2006SPD....37.0712B Altcode: 2006BAAS...38..229B
We use the Interferometric BIdimensional Spectrometer (IBIS) of
the INAF/Arcetri Astrophysical Observatory and installed at the
National Solar Observatory (NSO) Dunn Solar Telescope, to understand
the structure of sunspots. These high resolution observations were
acquired on 2004 July 30-31, of active region NOAA 10654, using the
high order NSO adaptive optics system. We map the spatio-temporal
variation of the penumbral Doppler signatures in three spectral
lines, FeI 6301.5 Å, FeII 7224.4 Å, and CaII 8542.6 Å, from the
photosphere to the chromosphere. From a 70-minute temporal average
of individual 32-second cadence Doppler observations we find that
the averaged velocities decrease with height, about 3.5 times larger
in the deeper photosphere (FeII 7224.4 Å height-of-formation ≈50
km) than in the upper photosphere FeI 6301.5 Å height-of-formation
≈350 km), There is a remarkable coherence of Doppler signals over
the height difference of 300 km. From a high-speed animation of the
Doppler sequence we find evidence for what appears to be ejection of
high speed gas concentrations from edges of penumbral filaments into
the surrounding granular photosphere. The Evershed flow persists a few
arcseconds beyond the traditionally demarcated penumbra-granulation
boundary. We present these and other results and discuss implications
of these measurements for sunspot models.

---------------------------------------------------------
Title: Oriented connectivity-based method for segmenting solar loops
Authors: Lee, Jong Kwan; Newman, Timothy S.; Gary, G. Allen
2006PatRe..39..246L Altcode:
A method based on oriented connectivity that can automatically segment
arc-like structures (solar loops) from intensity images of the Sun's
corona is introduced. The method is a constructive approach that
uses model-guided processing to enable extraction of credible loop
structures. Since the solar loops are vestiges of the solar magnetic
field, the model-guided processing exploits external estimates of this
field's local orientations that are derived from a physical magnetic
field model. Empirical studies of the method's effectiveness are
also presented. The oriented connectivity-based method is the first
automatic method for the segmentation of solar loops.

---------------------------------------------------------
Title: Advanced technology solar telescope multiple Fabry-Pérot
interferometer telecentric optical design
Authors: Robinson, Brian M.; Balasubramaniam, K. S.; Gary, Gilmer A.
2006OptEn..45b3001R Altcode:
We present four preliminary designs for a telecentric optical
train supporting the Advanced Technology Solar Telescope (ATST)
multiple Fabry-Pérot interferometer (MFPI), which is to be used as
an imaging spectrometer and imaging spectropolarimeter. The point
of departure for all three designs is the F/40 telecentric image
at the Coudé focus of the ATST. The first design, representing the
high-spectral-resolution mode of operation, produces an intermediate
F/300 telecentric image within the triple étalon system and a 34-arcsec
field of view (FOV). The second design, intermediate between high- and
low-spectral-resolution modes of operation, produces an intermediate
F/150 telecentric image at the étalons and a 1.1-arcmin FOV. The
third and fourth designs each represent a low-resolution mode of
operation, producing an F/82 telecentric image at the étalons and
a 2-arcmin FOV. Each design results in good telecentricity and image
quality. Departures from telecentricity at the intermediate image plane
cause field-dependent shifts of the bandpass peak, which are negligible
compared to the bandpass FWHM. The root mean square (rms) geometric spot
sizes at the final image plane fit well within the area of a camera
pixel, which is itself in accordance with the Nyquist criterion, half
the width of the 28-µm-wide resolution element (as determined from
the diffraction limit of the ATST). For each configuration, we also
examine the impact that the Beckers effect (the pupil apodization
caused by the angle-dependent amplitude transmittance of the MFPI)
has on the image quality of the MFPI instrument.

---------------------------------------------------------
Title: MTRAP: the magnetic transition region probe
Authors: Davis, J. M.; West, E. A.; Moore, R. L.; Gary, G. A.;
Kobayashi, K.; Oberright, J. E.; Evans, D. C.; Wood, H. J.; Saba,
J. L. R.; Alexander, D.
2005SPIE.5901..273D Altcode:
The Magnetic Transition Region Probe is a space telescope designed to
measure the magnetic field at several heights and temperatures in the
solar atmosphere, providing observations spanning the chromospheric
region where the field is expected to become force free. The primary
goal is to provide an early warning system (hours to days) for solar
energetic particle events that pose a serious hazard to astronauts in
deep space and to understand the source regions of these particles. The
required magnetic field data consist of simultaneous circular and linear
polarization measurements in several spectral lines over the wavelength
range from 150 to 855 nm. Because the observations are photon limited
an optical telescope with a large (&gt;18m2) collecting area
is required. To keep the heat dissipation problem manageable we have
chosen to implement MTRAP with six separate Gregorian telescopes, each
with ~ 3 m2 collecting area, that are brought to a common
focus. The necessary large field of view (5 × 5 arcmin2)
and high angular resolution (0.025 arcsec pixels) require large
detector arrays and, because of the requirements on signal to noise
(103), pixels with large full well depths to reduce the
readout time and improve the temporal resolution. The optical and
engineering considerations that have gone into the development of a
concept that meets MTRAP's requirements are described.

---------------------------------------------------------
Title: The solar ultraviolet magnetograph investigation: polarization
properties
Authors: West, E. A.; Porter, J. G.; Davis, J. M.; Gary, G. A.;
Kobayashi, K.; Noble, M.
2005SPIE.5901..226W Altcode:
This paper will describe the objectives of the Marshall Space
Flight Center (MSFC) Solar Ultraviolet Magnetograph Investigation
(SUMI) and the optical components that have been developed to meet
those objectives. A sounding rocket payload is being developed to
test the feasibility of magnetic field measurements in the Sun's
transition region. The optics have been optimized for simultaneous
measurements of two magnetic lines formed in the transition region (CIV
at 1550Å and MgII at 2800Å). Finally, this paper will concentrate
on the polarization properties of the SUMI polarimeter and toroidal
variable-line-space gratings.

---------------------------------------------------------
Title: Shape and Reconnection of the Exploding Magnetic Field in
the Onset of CMEs
Authors: Moore, R. L.; Sterling, A. C.; Falconer, D. A.; Gary, G. A.
2005AGUSMSH54B..01M Altcode:
From chromospheric and coronal images and line-of-sight and vector
magnetograms of magnetic regions that produce CMEs, and from
chromospheric and coronal movies of the onsets of CME eruptions,
it appears that the magnetic field that explodes to drive the CME
is initially the strongly sheared core of a magnetic arcade encasing
a polarity dividing line in the magnetic flux. Before or during the
onset of the explosion, the sheared core field becomes a flux rope,
often carrying chromospheric material within it. For the erupting flux
rope to drive the explosion, that is, for its magnetic energy content
to decrease in the explosion, the flux rope's cross-sectional area
must increase faster than its length. For instance, for isotropic
expansion, the area increases as the square of the length, and the
magnetic energy content of the flux rope decreases as the inverse of
the length. The instability that initiates the eruption of the flux
rope might be an ideal MHD kink instability, or might involve runaway
tether-cutting reconnection. The reconnection begins below the flux
rope (internal to the arcade) when the overall field configuration
of the region is effectively that of a single bipole. When the flux
rope resides in a multi-bipolar configuration having a magnetic null
above the flux rope, the runaway tether-cutting reconnection might
begin either below the flux rope or at the null above (external to)
the arcade. We present examples of observed CME onsets that illustrate
the above alternatives. In each example, reconnection below the flux
rope begins early in the eruption. This indicates that internal
tether cutting reconnection (classic tether-cutting reconnection)
is important in unleashing the CME explosion in all cases, including
those in which the explosion may be triggered by MHD kinking or by
external reconnection (classic breakout reconnection).

---------------------------------------------------------
Title: Triple Fabry-Pérot Imaging Interferometer for High Resolution
Solar Spectroscopy using the ATST
Authors: Robinson, B. M.; Gary, G. A.; Balasubramaniam, K. S.
2005AGUSMSP34A..05R Altcode:
We present a telecenrically mounted triple Fabry-Pérot imaging
interferometer for the NSOs Advanced Technology Solar Telescope
(ATST). It consists of three Fabry-Pérot etalons and the feed and
imaging optics. This system provides high throughput, flexibility
and breadth of operation when compared to other spectroscopic
imaging systems. It can operate in four distinct modes: as a
spectro-polarimeter, a filter-vector magnetograph, an intermediate-band
imager, and broadband high-resolution imager. In the proposed
telecentric mount configuration, the transmittance of the etalon system
is not a function of position in the field, so that instantaneous
spectroscopic measurements can be performed across the entire field
of view; however, the transmission peak of the interferometer is
broadened. Mitigation of this broadening requires a low F# image at
the etalons. Together with the requirement that the field of view be
large enough to observe large-scale processes in the solar atmosphere,
this limitation dictates that the diameter of the etalons have a large
aperture. Specifically, for a spectrographic passband full-width at
half-maximum (FWHM) of around 2 pm, and entrance pupil diameter of 4 m,
and a field of view of 35", the required etalon diameter is around 200
mm. This is beyond the size of current Fabry-Pérot etalons and near
the current projected limit of manufacturability. The development
of this instrument will bring these large etalons to realization
and take Fabry-Pérot imaging interferometry to the next level of
operational capability within telescopes of large aperture. This
instrument will provide spectral, spatial, and temporal resolution
which is not currently available to large aperture solar astronomy,
but which is necessary, in conjunction with the new class telescopes,
to the continuing discovery of laws that govern the dynamics of the sun
and the earth-sun connection. The resolution afforded by higher aperture
telescopes and instrumentation will give scientists new insight into
the magnetohydrodynamic processes occurring on the Sun via simultaneous
spectral and spatial measurements across the entire field of view. We
will describe the optical train supporting the filter system and the
expected imaging performance. We will analyze the effects of spectral
resolution of the instrument due etalon spacing parameters, optical
configuration, and the plate defect finesse. We present calculations of
the pupil apodization for three modes of operation and the consequences
for the imaging and spectroscopic performance of the system; and a
treatment of noise contributions from the parasitic off-band spectral
orders and ghost images arising from multiple reflections within the
etalon system.

---------------------------------------------------------
Title: Photospheric and Chromospheric structure of Sunspots using
IBIS.
Authors: Balasubramaniam, K. S.; Gary, G. A.; Reardon, K.
2005AGUSMSP11A..04B Altcode:
We use the Interferometric BIdimensional Spectrometer (IBIS) of the
INAF/Arcetri Astrophysical Observatory and installed at the National
Solar Observatory's (NSO) Dunn Solar Telescope, to understand the
structure of sunspots. Using the spectral lines FeI 6301.5Å, FeII
7224.4Å and CaII 8542.6Å, we examine the spectroscopic variation of
sunspot penumbral and umbral structures about the heights of formation
of these lines. Simultaneous white-light imaging data helps us to
register and track the images. We map the spatio-temporal variation
of Doppler signatures in these spectral lines, from the photosphere
to the chromosphere, and discuss the implication of these variations
for sunspot models. These high resolution observations were acquired
on 2004 July 30-31, on a sunspot NOAA 10654, using the higher order
NSO adaptive optics system.

---------------------------------------------------------
Title: The Marshall Space Flight Center solar ultraviolet magnetograph
Authors: West, Edward A.; Porter, Jason G.; Davis, John M.; Gary,
G. A.; Noble, Matthew W.; Lewis, Matthew; Thomas, Roger J.
2004SPIE.5488..801W Altcode:
This paper will describe the objectives of the Marshall Space
Flight Center (MSFC) Solar Ultraviolet Magnetograph Investigation
(SUMI) and the optical components that have been developed to meet
those objectives. In order to test the scientific feasibility of
measuring magnetic fields in the UV, a sounding rocket payload
is being developed. This paper will discuss: (1) the scientific
measurements that will be made by the SUMI sounding rocket program,
(2) how the optics have been optimized for simultaneous measurements of
two magnetic lines CIV (1550Å) and MgII (2800Å), and (3) the optical,
reflectance, transmission and polarization measurements that have been
made on the SUMI telescope mirrors and polarimeter.

---------------------------------------------------------
Title: Optical design for a Fabry-Perot image interferometer for
solar observations
Authors: Moretto, Gilberto; Gary, G. Allen; Balasubramaniam, K. S.;
Rimmele, Thomas R.
2004SPIE.5492.1773M Altcode:
We outline here a preliminary optical design study for a telecentric
tunable Fabry-Perot etalon system. The first result of the optical
optimization into a design, which delivers performance image quality
and telecentricity, is presented here. Bearing in mind the possible
use of such a study design - as a possible instrument for the Advanced
Technology Solar Telescope (ATST) - we also show that a hybrid design
strategy delivers a compact design that will fit inside the ATST's
Coude optical tables.

---------------------------------------------------------
Title: Instrumentation for the Advanced Technology Solar Telescope
Authors: Rimmele, Thomas R.; Hubbard, Robert P.; Balasubramaniam,
K. S.; Berger, Tom; Elmore, David; Gary, G. Allen; Jennings, Don;
Keller, Christoph; Kuhn, Jeff; Lin, Haosheng; Mickey, Don; Moretto,
Gilberto; Socas-Navarro, Hector; Stenflo, Jan O.; Wang, Haimin
2004SPIE.5492..944R Altcode:
The 4-m aperture Advanced Technology Solar Telescope (ATST) is the
next generation ground based solar telescope. In this paper we provide
an overview of the ATST post-focus instrumentation. The majority of
ATST instrumentation is located in an instrument Coude lab facility,
where a rotating platform provides image de-rotation. A high order
adaptive optics system delivers a corrected beam to the Coude lab
facility. Alternatively, instruments can be mounted at Nasmyth or
a small Gregorian area. For example, instruments for observing the
faint corona preferably will be mounted at Nasmyth focus where maximum
throughput is achieved. In addition, the Nasmyth focus has minimum
telescope polarization and minimum stray light. We describe the set of
first generation instruments, which include a Visible-Light Broadband
Imager (VLBI), Visible and Near-Infrared (NIR) Spectropolarimeters,
Visible and NIR Tunable Filters, a Thermal-Infrared Polarimeter &amp;
Spectrometer and a UV-Polarimeter. We also discuss unique and efficient
approaches to the ATST instrumentation, which builds on the use of
common components such as detector systems, polarimetry packages and
various opto-mechanical components.

---------------------------------------------------------
Title: Eruption of a Multiple-Turn Helical Magnetic Flux Tube in a
Large Flare: Evidence for External and Internal Reconnection That
Fits the Breakout Model of Solar Magnetic Eruptions
Authors: Gary, G. Allen; Moore, R. L.
2004ApJ...611..545G Altcode:
We present observations and an interpretation of a unique multiple-turn
spiral flux tube eruption from active region 10030 on 2002 July 15. The
TRACE C IV observations clearly show a flux tube that is helical and
erupting from within a sheared magnetic field. These observations are
interpreted in the context of the breakout model for magnetic field
explosions. The initiation of the helix eruption, as determined by a
linear backward extrapolation, starts 25 s after the peak of the flare's
strongest impulsive spike of microwave gyrosynchrotron radiation early
in the flare's explosive phase, implying that the sheared core field
is not the site of the initial reconnection. Within the quadrupolar
configuration of the active region, the external and internal
reconnection sites are identified in each of two consecutive eruptive
flares that produce a double coronal mass ejection (CME). The first
external breakout reconnection apparently releases an underlying sheared
core field and allows it to erupt, leading to internal reconnection in
the wake of the erupting helix. This internal reconnection releases the
helix and heats the two-ribbon flare. These events lead to the first
CME and are followed by a second breakout that initiates a second and
larger halo CME. The strong magnetic shear in the region is compatible
with the observed rapid proper motion and evolution of the active
region. The multiple-turn helix originates from above a sheared-field
magnetic inversion line within a filament channel, and starts to erupt
only after fast breakout reconnection has started. These observations
are counter to the standard flare model and support the breakout model
for eruptive flare initiation.

---------------------------------------------------------
Title: Forecasting Coronal Mass Ejections from Magnetograms
Authors: Falconer, D. A.; Moore, R. L.; Gary, G. A.; Balasubramanian,
S.
2004AAS...204.2705F Altcode: 2004BAAS...36..693F
We report further results from our ongoing assessment of
magnetogram-based measures of active-region nonpotentiality (magnetic
shear and twist), magnetic complexity and size as predictors of
coronal mass ejections (CMEs). From a set of 36 vector magnetograms
of predominantly bipolar active regions (Falconer, Moore, &amp;
Gary 2004, ApJ, submitted), we have found: (1) Each of five different
measures of active-region nonpotentiality has a 75-80 (with correlation
confidence level &gt; 95%) in predicting whether an active region will
produce a CME within 2 days after the magnetogram. (2) One of these
measures can be obtained from a line-of-sight magnetogram without use
of a vector magnetogram. Hence this measure appears to be the best
practical measure of active-region nonpotentiality for operational
CME forecasting. (3) Our measure of active-region size has a 65%
success rate in predicting CMEs in this window, but the correlation
is not statistically significant (confidence level ∼ 80%) for our
sample size. We have applied a measure of active-region complexity (the
fraction of magnetic flux not in the active region's primary bipole)
to our set of 36 magnetograms and found a correlation with the CME
productivity of the active regions. We are also applying measures of
nonpotentiality, size, and complexity to multi-bipolar active regions to
assess their CME-prediction ability for these more complicated active
regions. This work was funded by NASA through its LWS TR&amp;T
Program and its Solar and Heliospheric Physics SR&amp;T Program,
and by NSF through its Solar Terrestrial Research and SHINE Programs.

---------------------------------------------------------
Title: A measure from line-of-sight magnetograms for prediction of
coronal mass ejections
Authors: Falconer, D. A.; Moore, R. L.; Gary, G. A.
2003JGRA..108.1380F Altcode:
From a sample of 17 vector magnetograms of 12 bipolar active regions we
have recently found (1) that a measure of the overall nonpotentiality
(the overall twist and shear in the magnetic field) of an active region
is given by the strong shear length LSS, the length of
the portion of the main neutral line on which the observed transverse
fields is strong (&gt;150 Guass (G)) and strongly sheared (shear angle
&gt;45°), and (2) that LSS is well correlated with the
coronal mass ejection (CME) productivity of the active regions during
the ±2-day time window centered on the day of the magnetogram. In the
present paper, from the same sample of 17 vector magnetograms, we show
that there is a viable proxy for LSS that can be measured
from a line-of-sight magnetogram. This proxy is the strong gradient
length LSG, the length of the portion of the main neutral
line on which the potential transverse field is strong (&gt;150 G), and
the gradient of the line-of-sight field is sufficiently steep (greater
than ∼50 G/Mm). In our sample of active regions, LSG is
statistically significantly correlated with LSS (correlation
confidence level &gt;95%), and LSG is as strongly
correlated with active region CME productivity as is LSS
(correlation confidence level ∼99.7%). Because LSG can
be measured from line-of-sight magnetograms obtained from conventional
magnetographs, such as the magnetograph mode of the Michelson Doppler
Imager (MDI) on board the Solar and Heliospheric Observatory, it is
a dependable substitute for LSS for use in operational
CME forecasting. In addition, via measurement of LSG, the
years-long, nearly continuous sequence of 1.5-hour cadence full disk
line-of-sight magnetograms from MDI can be used to track the growth
and decay of the large-scale nonpotentiality in active regions and to
examine the role of this evolution in active region CME productivity.

---------------------------------------------------------
Title: Automated Coronal Loop Identification using Digital Image
Processing Techniques
Authors: Lee, J. K.; Gary, G. A.; Newman, T. S.
2003SPD....34.0305L Altcode: 2003BAAS...35..809L
The results of a Master's thesis study of computer algorithms
for automatic extraction and identification (i.e., collectively,
"detection") of optically-thin, 3-dimensional, (solar) coronal-loop
center "lines" from extreme ultraviolet and X-ray 2-dimensional images
will be presented. The center lines, which can be considered to be
splines, are proxies of magnetic field lines. Detecting the loops
is challenging because there are no unique shapes, the loop edges
are often indistinct, and because photon and detector noise heavily
influence the images. Three techniques for detecting the projected
magnetic field lines have been considered and will be described in
the presentation. The three techniques used are (i) linear feature
recognition of local patterns (related to the inertia-tensor concept),
(ii) parametric space inferences via the Hough transform, and (iii)
topological adaptive contours (snakes) that constrain curvature and
continuity. Since coronal loop topology is dominated by the magnetic
field structure, a first-order magnetic field approximation using
multiple dipoles provides a priori information that has also been
incorporated into the detection process. Synthesized images have been
generated to benchmark the suitability of the three techniques, and the
performance of the three techniques on both synthesized and solar images
will be presented and numerically evaluated in the presentation. The
process of automatic detection of coronal loops is important in the
reconstruction of the coronal magnetic field where the derived magnetic
field lines provide a boundary condition for magnetic models ( cf. ,
Gary (2001, Solar Phys., 203, 71) and Wiegelmann &amp; Neukirch (2002,
Solar Phys., 208, 233)). . This work was supported by NASA's Office
of Space Science - Solar and Heliospheric Physics Supporting Research
and Technology Program.

---------------------------------------------------------
Title: Parametric Transformation Analysis of Observed Coronal
Magnetic Structures
Authors: Gary, G. A.
2003SPD....34.1609G Altcode: 2003BAAS...35..834G
Twisted coronal features are important signatures for predicting
solar eruptive events, and yet not clearly understood. We present
new results for determining the complex, non-potential magnetic
field configurations of active regions. This research uses free-form
deformation mathematics to generate the 3-dimensional coronal magnetic
field. We use a parametric representation of the magnetic field lines
such that the field lines can be manipulated to match the observed EUV
and SXR coronal loops. The objective is to derive sigmoidal magnetic
field solutions which allow beta &gt; 1 regions to be included,
aligned and non-aligned electric currents to be calculated, and the
Lorentz force to be determined. The advantage of our technique is that
the solution is independent of the unknown upper and side boundary
conditions, allows non-vanishing magnetic forces, and provides a global
magnetic field solution, which contains high- and low-beta regimes and
is consistent with the observed coronal structure of the region. We
show that the mathematical description is unique and physical. This
work was supported by NASA's Office of Space Science - Solar and
Heliospheric Physics Supporting Research and Technology program.

---------------------------------------------------------
Title: CME Prediction from Line-of-Sight Magnetograms
Authors: Falconer, D. A.; Moore, R. L.; Gary, G. A.
2003SPD....34.0503F Altcode: 2003BAAS...35R.814F
We have previously shown for bipolar active regions that measures of
active-region nonpotentiality from vector magnetograms are correlated
with active-region CME productivity (Falconer, Moore, &amp; Gary
2002, ApJ, 569, 1016). Guided by those measures and results, we have
now obtained a measure from line-of-sight magnetograms that is well
correlated both with our measures of active-region nonpotentiality from
vector magnetograms and with active-region CME productivity. The measure
is the length of strong-gradient main neutral line (LG). This
is the length of a bipolar region's main neutral line on which the
potential transverse field is greater than 150G, and the gradient in
the line-of-sight field is greater than 50G/Mm. From the sample
of 17 MSFC magnetograms of 12 basically bipolar active regions used in
our previous paper, we find that LG is strongly correlated
(99.7%) with one of our vector-magnetogram measures of nonpotentiality,
the length of strong-gradient main neutral line LSS. We
also find that LG is as strongly correlated (99.7%)
with CME productivity as is LSS. Being obtainable from
line-of-sight magnetograms, LG makes the much larger data
set of line-of-sight magnetograms (i.e. from SOHO/MDI and Kitt Peak)
available for CME prediction study. This is especially important for
evolutionary studies, with SOHO/MDI having no day/night, cloudy weather,
or atmospheric seeing problems. This work was supported by funding
from NSF's Division of Atmospheric Sciences (Space Weather and Shine
Programs) and by NASA's Office of Space Science (Living with a Star
Program and Solar and Heliospheric Physics Supporting Research and
Technology Program).

---------------------------------------------------------
Title: SUMI - The Solar Ultraviolet Magnetograph Investigation
Authors: Porter, J. G.; West, E. A.; Davis, J. M.; Gary, G. A.; Noble,
M. W.; Thomas, R. J.; Rabin, D. M.; Uitenbroek, H.
2003SPD....34.2015P Altcode: 2003BAAS...35..847P
Solar physics has been successful in characterizing the full vector
magnetic field in the photosphere, where the ratio of gas pressure to
magnetic pressure (β ) is greater than 1. However, at higher levels
in the atmosphere, where β is much less than 1 and flares and CMEs
are believed to be triggered, observations are difficult, severely
limiting the understanding of these processes. In response to this
situation, we are developing SUMI (the Solar Ultraviolet Magnetograph
Investigation) a unique instrument designed to measure the circular
and linear polarization of upper chromospheric Mg II lines (280 nm) and
circular polarization of transition region C IV lines (155 nm). To date
the telescope mirrors have been built, tested and coated with dielectric
stacks designed to reflect only the wavelengths of interest. We have
also developed a unique UV polarimeter and completed the design of a
high-resolution spectrograph that uses dual toroidal varied-line-space
(TVLS) gratings. Incorporating measurements of those components
developed so far, the revised estimate of the system throughput exceeds
our original estimate by more than an order of magnitude. A sounding
rocket flight is anticipated in 2006. Our objectives and progress
are detailed in this presentation. This work is supported by
NASA SR&amp;T.

---------------------------------------------------------
Title: Multiple Etalon Systems for the Advanced Technology Solar
Telescope
Authors: Gary, G. A.; Balasubramaniam, K. S.; Sigwarth, Michael
2003SPIE.4853..252G Altcode:
Multiple etalon systems are discussed that meet the science requirements
for a narrow-passband imaging system for the 4-meter National Solar
Observatory (NSO)/Advance Technology Solar Telescope (ATST). A
multiple etalon system can provide an imaging interferometer that
works in four distinct modes: as a spectro-polarimeter, a filter-vector
magnetograph, an intermediate-band imager, and broadband high-resolution
imager. Specific dual and triple etalon configurations are described
that provide a spectrographic passband of 2.0-3.5 pm and reduce
parasitic light levels to 10-4 as required for precise
polarization measurement, e.g., Zeeman measurements of magnetic
sensitive lines. A TESOS-like (Telecentric Etalon SOlar Spectrometer)
triple etalon system provides a spectral purity of 10-5. The
triple designs have the advantage of reducing the finesse requirement
on each etalon; allow the use of more stable blocking filters, and have
very high spectral purity. A dual-etalon double-pass (Cavallini-like)
system can provide a competing configuration. Such a dual-etalon design
can provide high contrast. The selection of the final focal plane
instrument will depend on a trade-off between an ideal instrument and
practical reality. The trade study will include the number of etalons,
their aperture sizes, complexities of the optical train, number of
blocking filters, configuration of the electronic control system,
computer interfaces, temperature controllers, etalon controllers,
and their associated feedback electronics. The heritage of single and
multiple etalon systems comes from their use in several observatories,
including the Marshall Space Flight Center (MSFC) Solar Observatory,
Sacramento Peak Observatory (NSO), and Kiepenheuer-Institut für
Sonnenphysik (KIS, Germany), Mees Solar Observatory (University of
Hawaii), and Arcetri Astrophysical Observatory (Italy). The design
of the ATST multiple etalon system will benefit from the experience
gained at these observatories.

---------------------------------------------------------
Title: High Resolution Imaging Spectroscopy of Sunspots
Authors: Balasubramaniam, K. S.; Titus, T.; Gary, G. Allen
2003ASPC..286..259B Altcode: 2003ctmf.conf..259B
No abstract at ADS

---------------------------------------------------------
Title: Forecasting Coronal Mass Ejections from Vector Magnetograms
Authors: Falconer, D. A.; Moore, R. L.; Gary, G. A.
2002AAS...200.2005F Altcode: 2002BAAS...34..673F
In a 17 vector magnetogram study of 12 bipolar active regions
(Falconer, Moore, &amp; Gary 2002, ApJ in press), we evaluated from
each vector magnetogram four global measures of the magnetic field of
the observed active region, and examined the correlation of each of
these quantities with the CME productivity of the active regions. The
four global magnetic quantities were 1) the total magnetic flux (Φ ),
which is a measure of the size of an active region, and three measures
of the global nonpotentiality of an active region: 2) the length of
strong-field, strong-shear main neutral line (LSS), the
net current (IN), and the magnetic twist parameter ( α =μ
IN/Φ ). The CME productivity of each active region for each
day of its disk passage was determined from Yohkoh/SXT coronal X-ray
images together with GOES X-ray flux observations and, when available,
SOHO/LASCO observations. For a centered time window of 5 days (day of
the magnetogram +/- 2 days) for CME production, for each of the three
measures of global nonpotentiality, whether the measure was above its
median value was well correlated with whether the active region produced
any CMEs. For each, the confidence level of the correlation was &gt;=
99%. The sample size was too small to show a statistically significant
correlation (confidence level &gt;= 95%) of the global nonpotentiality
measures with future CME production, that is, from the date of the
magnetogram forward. We are doubling our sample, and will report on
our statistical evaluation of global nonpotentiality as a predictor of
future CME productivity. The vector magnetograms of the added active
regions are from the first year of operation (September 2000 - October
2001) of the upgraded MSFC vector magnetograph. This work is funded by
NSF through its Space Weather Program, and by NASA through its Living
With a Star Targeted Research and Technology Program and its Solar and
Heliospheric Physics Supporting Research and Technology Program. The
upgrade of the MSFC vector magnetograph was funded by the HESSI mission.

---------------------------------------------------------
Title: Correlation of the Coronal Mass Ejection Productivity of
Solar Active Regions with Measures of Their Global Nonpotentiality
from Vector Magnetograms: Baseline Results
Authors: Falconer, D. A.; Moore, R. L.; Gary, G. A.
2002ApJ...569.1016F Altcode:
From conventional magnetograms and chromospheric and coronal images,
it is known qualitatively that the fastest coronal mass ejections
(CMEs) are magnetic explosions from sunspot active regions in which
the magnetic field is globally strongly sheared and twisted from its
minimum-energy potential configuration. In this paper, we present
measurements from active region vector magnetograms that begin to
quantify the dependence of the CME productivity of an active region
on the global nonpotentiality of its magnetic field. From each of 17
magnetograms of 12 bipolar active regions, we obtain a measure of the
size of the active region (the magnetic flux content, Φ) and three
different measures of the global nonpotentiality (LSS, the
length of strong-shear, strong-field main neutral line; IN,
the net electric current arching from one polarity to the other;
and α=μIN/Φ, a flux-normalized measure of the field
twist). From these measurements and the observed CME productivity of
the active regions, we find that: (1) All three measures of global
nonpotentiality are statistically significantly correlated with
each other and with the active region flux content. (2) All three
measures of global nonpotentiality are significantly correlated with
CME productivity. The flux content has some correlation with CME
productivity, but at a less than statistically significant confidence
level (less than 95%). (3) The net current is less strongly correlated
with CME productivity than is α, and the correlation of flux
content with CME productivity is weaker still. If these differences
in correlation strength, and a significant correlation of α with
flux content, persist to larger samples of active regions, this would
suggest that active region size does not affect CME productivity except
through global nonpotentiality. (4) For each of the four global magnetic
quantities, the correlation with CME productivity is stronger for a +/-2
day time window for the CME production than for windows half as wide or
twice as wide. This plausibly results from most CME-productive active
regions producing less than one CME per day, and from active region
evolution often significantly changing the global nonpotentiality over
the course of several days. These results establish that measures of
active region global nonpotentiality from vector magnetograms (such as
LSS, IN, and α) should be useful for prediction
of active region CMEs.

---------------------------------------------------------
Title: Development of a new vector magnetograph at Marshall Space
Flight Center
Authors: West, Edward A.; Hagyard, Mona J.; Gary, G. Allen; Smith,
James; Adams, Mitzi; Cloyd, Richard A.
2002SPIE.4481..270W Altcode:
This paper will describe a new vector magnetograph that has been
developed at Marshall Space Flight Center. This magnetograph was a test
ed for space flight concepts. One of those concepts that is currently
being tested is the increased sensitivity to linear polarization by
replacing electro-optical and rotating waveplates with a rotating linear
analyzer. Our paper will describe the motivation for developing this
magnetograph, compare this instrument with traditional magnetograph
designs.

---------------------------------------------------------
Title: Development of a polarimeter for magnetic field measurements
in the ultraviolet
Authors: West, Edward A.; Porter, Jason G.; Davis, John M.; Gary,
G. Allen; Adams, Mitzi
2002SPIE.4481..109W Altcode:
The polarizing optics that are being developed for the Solar UV
Magnetograph Investigation (SUMI) are described. This polarimeter
is being designed for a sounding rocket payload which will make
simultaneous measurements of two magnetically sensitive lines CIV and
MgII. With a limited observing program, the polarizing optics will be
optimized for circular and linear polarization measurements in active
regions. The Q polarization will represent exploratory measurements of
the transverse field in strong sunspots. This paper will give a brief
overview of the SUMI instrument and its scientific goals, will describe
the polarimeter that will be used in the sounding rocket program,
and will present some of the measurements that have been made on the
SUMI polarization optics.

---------------------------------------------------------
Title: Use of Yohkoh SXT in Measuring the Net Current and CME
Productivity of Active Regions
Authors: Falconer, D. A.; Moore, R. L.; Gary, G. A.
2002mwoc.conf..303F Altcode:
In our investigation of the correlation of global nonpotentiality of
active regions to their CME productivity (Falconer, D. A. 2001, JGR,
in press, and Falconer, Moore, &amp; Gary, 2000, EOS 82, 20 S323),
we use Yohkoh SXT images for two purposes. The first use is to help
resolve the 180o ambiguity in the direction of the observed
transverse magnetic field. Resolution of the 180o ambiguity
is important, since the net current, one of our measures of global
nonpotentiality, is derived from integrating the dot product of the
transverse field around a contour (IN = int BTcdot
dl). The ambiguity results from the observed transverse field being
determined from the linear polarization, which gives the plane of the
direction, but leaves a 180o ambiguity. Automated methods
to resolve the ambiguity ranging from the simple acute angle rule
(Falconer, D. A. 2001) to the more sophisticated annealing method
(Metcalf T. R. 1994). For many active regions, especially ones that are
nearly potential these methods work well. But for very nonpotential
active regions where the shear angle (the angle between the observed
and potential transverse field) is near 90o throughout
large swaths along the main neutral line, both methods can resolve
the ambiguity incorrectly for long segments of the neutral line. By
determining from coronal images, such as those from Yohkoh/SXT, the
sense of shear along the main neutral line in the active region, these
cases can be identified and corrected by a modification of the acute
angle rule described here. The second use of Yohkoh/SXT in this study
is to check for the cusped coronal arcades of long-duration eruptive
flares. This signature is an excellent proxy for CMEs, and was used
by Canfield, Hudson, and McKenzie (1999 GRL V26, 6, 627-630). This
work is funded by NSF through the Space Weather Program and by NASA
through the Solar Physics Supporting Research and Technology Program.

---------------------------------------------------------
Title: Optical characteristics of the Marshall Space Flight Center
solar ultraviolet magnetograph
Authors: West, Edward A.; Porter, Jason G.; Davis, John M.; Gary,
G. Allen; Adams, Mitzi; Smith, W. Scott; Hraba, John F.
2001SPIE.4498..101W Altcode:
This paper will describe the scientific objectives of the Marshall
Space Flight Center (MSFC) Solar Ultraviolet Magnetograph Investigation
(SUMI) and the optical components that have been developed to meet
those objectives. In order to test the scientific feasibility of
measuring magnetic fields in the UV, a sounding rocket payload is being
developed. This paper will discuss: (1) the scientific measurements that
will be made by the SUMI sounding rocket program, (2) how the optics
have been optimized for simultaneous measurements of two magnetic lines
CIV (1550 Angstroms) and MgII (2800 Angstroms), and (3) the optical,
reflectance, transmission and polarization measurements that have been
made on the SUMI telescope mirrors and polarimeter.

---------------------------------------------------------
Title: Plasma Beta above a Solar Active Region: Rethinking the
Paradigm
Authors: Gary, G. Allen
2001SoPh..203...71G Altcode:
In this paper, we present a model of the plasma beta above an active
region and discuss its consequences in terms of coronal magnetic field
modeling. The β-plasma model is representative and derived from a
collection of sources. The resulting β variation with height in the
solar atmosphere is used to emphasize that the assumption that the
magnetic pressure dominates over the plasma pressure must be carefully
employed when extrapolating the magnetic field. This paper points out
(1) that the paradigm that the coronal magnetic field can be constructed
from a force-free magnetic field must be used in the correct context,
since the force-free region is sandwiched between two regions which have
β&gt;1, (2) that the chromospheric Mg ii-C iv magnetic measurements
occur near the β-minimum, and (3) that, moving from the photosphere
upwards, β can return to ∼1 at relatively low coronal heights,
e.g., R∼1.2 Rs.

---------------------------------------------------------
Title: Deriving Coronal Magnetic Fields Using Parametric
Transformation Analysis
Authors: Gary, G. A.
2001AGUSM..SP51A01G Altcode:
When plasma β &gt;1 then the gas pressure dominates over the magnetic
pressure. This ratio as a function along the coronal magnetic field
lines varies from β &gt; 1 in the photosphere at the base of the field
lines, to β &lt;&lt; 1 in the mid-corona, to β &gt; 1 in the upper
corona. Almost all magnetic field extrapolations do not or cannot
take into account the full range of β . They essentially assume β
&lt;&lt; 1 , since the full boundary conditions do not exist in the
β &gt; 1 regions. We use a basic parametric representation of the
magnetic field lines such that the field lines can be manipulated
to match linear features in the EUV and SXR coronal images in a
least squares sense. This research employs free-form deformation
mathematics to generate the associated coronal magnetic field. In our
research program, the complex magnetic field topology uses Parametric
Transformation Analysis (PTA) which is a new and innovative method to
describe the coronal fields that we are developing. In this technique
the field lines can be viewed as being embedded in a plastic medium,
the frozen-in-field-line concept. As the medium is deformed the field
lines are similarly deformed. However the advantage of the PTA method
is that the field line movement represents a transformation of one
magnetic field solution into another magnetic field solution. When
fully implemented, this method will allow the resulting magnetic field
solution to fully match the magnetic field lines with EUV/SXR coronal
loops by minimizing the differences in direction and dispersion of a
collection of PTA magnetic field lines and observed field lines. The
derived magnetic field will then allow β &gt; 1 regions to be included,
the electric currents to be calculated, and the Lorentz force to be
determined. The advantage of this technique is that the solution is
(i) independent of the upper and side boundary conditions, (ii) allows
non-vanishing magnetic forces, and (iii) provides a global magnetic
field solution, which contains high- and low- β regimes and maximizes
the similarity between the field lines structure and all the coronal
images of the region. The coronal image analysis is crucial to the
investigation and for the first time these images can be exploited
to derive the coronal magnetic field in a well-posed mathematical
formulation. This program is an outgrowth of an investigation in
which an extrapolated potential field was required to be "inflated" in
order to have the field lines match the Yohkoh/SXT images (Gary &amp;
Alexander 1999, Solar Physics, 186, 123). The field lines were radially
stretched resulting in a better match to the coronal loops of an active
region. The PTA method of radial and non-radial deformations of field
lines to provide a match to the EUV/SXR images will be presented.

---------------------------------------------------------
Title: Prediction of Coronal Mass Ejections from Vector Magnetograms:
Quantitative Measures as Predictors
Authors: Falconer, D. A.; Moore, R. L.; Gary, G. A.
2001AGUSM..SH41C04F Altcode:
In a pilot study of 4 active regions (Falconer, D.A. 2001, JGR, in
press), we derived two quantitative measures of an active region's
global nonpotentiality from the region's vector magnetogram, 1) the
net current (IN), and 2) the length of the strong-shear,
strong-field main neutral line (LSS), and used these two
measures of the CME productivity of the active regions. We compared the
global nonpotentiality measures to the active regions' CME productivity
determined from GOES and Yohkoh/SXT observations. We found that two
of the active regions were highly globally nonpotential and were
CME productive, while the other two active regions had little global
nonpotentiality and produced no CMEs. At the Fall 2000 AGU (Falconer,
Moore, &amp; Gary, 2000, EOS 81, 48 F998), we reported on an expanded
study (12 active regions and 17 magnetograms) in which we evaluated
four quantitative global measures of an active region's magnetic field
and compared these measures with the CME productivity. The four global
measures (all derived from MSFC vector magnetograms) included our two
previous measures (IN and LSS) as well as two new
ones, the total magnetic flux (Φ ) (a measure of an active region's
size), and the normalized twist (α =μ IN/Φ ). We found
that the three measures of global nonpotentiality (IN,
LSS, α ) were all well correlated (&gt;99% confidence
level) with an active region's CME productivity within (2 days of
the day of the magnetogram. We will now report on our findings of how
good our quantitative measures are as predictors of active-region CME
productivity, using only CMEs that occurred after the magnetogram. We
report the preliminary skill test of these quantitative measures as
predictors. We compare the CME prediction success of our quantitative
measures to the CME prediction success based on an active region's past
CME productivity. We examine the cases of the handful of false positive
and false negatives to look for improvements to our predictors. This
work is funded by NSF through the Space Weather Program and by NASA
through the Solar Physics Supporting Research and Technology Program.

---------------------------------------------------------
Title: Overview of the Solar Ultraviolet Magnetograph Investigation
Authors: West, Edward A.; Porter, Jason G.; Davis, John M.; Gary,
G. Allen; Rabin, Douglas M.; Thomas, Roger J.; Davila, Joseph M.
2000SPIE.4139..350W Altcode:
Traditional magnetographs measure the solar magnetic field at the
visible 'surface' of the Sun, the photosphere. The Solar Ultraviolet
Magnetograph Investigation (SUMI) is a hardware development study
for an instrument to measure the solar magnetic field higher in the
atmosphere, in the upper chromosphere and in the transition region at
the base of the corona. The magnetic pressure at these levels is much
stronger than the gas pressure (in contrast to the situation at the
photosphere), so the field controls the structure and dynamics of the
atmosphere. Rapid changes in the magnetic structure of the atmosphere
become possible at this height, with the release of energy. Measurements
of the vector magnetic field in this region will significantly improve
our understanding of the physical processes heating the Sun's upper
atmosphere and driving transient phenomena such as flares and coronal
mass ejections. The instrument will incorporate new technologies to
achieve the polarization efficiencies required to measure the magnetic
splitting of lines in the VUV an UV (CIV at 1550 angstrom and
MgII at 2800 angstrom). We describe the scientific goals,
the optical components that are being developed for a sounding rocket
program, and the SUMI baseline design.

---------------------------------------------------------
Title: Erratum: An Assessment of Magnetic Conditions for Strong
Coronal Heating in Solar Active Regions by Comparing Observed Loops
with Computed Potential Field Lines
Authors: Falconer, D. A.; Gary, G. A.; Moore, R. L.; Porter, J. G.
2000ApJ...538..467F Altcode:
In the paper “An Assessment of Magnetic Conditions for Strong
Coronal Heating in Solar Active Regions by Comparing Observed Loops
with Computed Potential Field Lines” by D. A. Falconer, G. A. Gary,
R. L. Moore, and J. G. Porter (ApJ, 528, 1004 [2000]), Figure 4 was
rotated 180° and so did not match the figure caption. The correct
orientation and figure caption is given here.

---------------------------------------------------------
Title: SUMI: The Solar Ultraviolet Magnetograph
Authors: Davis, J. M.; Porter, J. G.; Gary, G. A.; West, E. A.; Rabin,
D. M.; Thomas, R. J.; Davila, J. M.
2000SPD....31.0299D Altcode: 2000BAAS...32..828D
A major focus of solar physics is the measurement of the temporal
and spatial variability of solar magnetic fields from the photosphere
into the lower corona, together with the study of how their behavior
produces the dynamic phenomena in this region such as flares and
CMEs. Considerable success has been achieved in the characterization of
the full vector field in the photosphere, where β , the ratio of the
gas pressure to the magnetic pressure, is gtrsim1. At higher levels
in the atmosphere where β &lt;&lt;1, the magnetic field (through
the Lorentz force) controls the structure and dynamics of the solar
atmosphere, and rapid changes in structure with release of energy
become possible. However, observations of the field at these higher
levels have proven to be difficult, placing a serious limitation on our
understanding of the physical processes occurring there. This poster
will discuss the Solar Ultraviolet Magnetograph Investigation (SUMI),
a hardware development study for an instrument capable of measuring
the polarization in ultraviolet lines of C IV and Mg II formed in the
transition region and upper chromosphere. We are currently developing
optical technologies necessary to build an instrument that will
achieve a major advance in performance over that of earlier attempts
(e.g., SMM/UVSP). Initially configured as a sounding rocket payload,
such a UV magnetograph would allow us to make exploratory measurements
extending the observation of solar magnetic fields into new and dynamic
regimes. This work is supported by NASA through the SEC Program in
Solar Physics and the program for Technology Development for Explorer
Missions and Sofia.

---------------------------------------------------------
Title: Three-dimensional Stereoscopic Analysis of Solar Active Region
Loops. II. SOHO/EIT Observations at Temperatures of 1.5-2.5 MK
Authors: Aschwanden, Markus J.; Alexander, David; Hurlburt, Neal;
Newmark, Jeffrey S.; Neupert, Werner M.; Klimchuk, J. A.; Gary,
G. Allen
2000ApJ...531.1129A Altcode:
In this paper we study the three-dimensional structure of hot
(Te~1.5-2.5 MK) loops in solar active region NOAA
7986, observed on 1996 August 30 with the Extreme-ultraviolet
Imaging Telescope (EIT) on board the Solar and Heliospheric
Observatory (SOHO). This complements a first study (Paper I) on
cooler (Te~1.0-1.5 MK) loops of the same active region,
using the same method of Dynamic Stereoscopy to reconstruct the
three-dimensional geometry. We reconstruct the three-dimensional
coordinates x(s), y(s), z(s), the density ne(s), and
temperature profile Te(s) of 35 individual loop segments
(as a function of the loop coordinate s) using EIT 195 and 284 Å
images. The major findings are as follows. (1) All loops are found
to be in hydrostatic equilibrium, in the entire temperature regime
of Te=1.0-2.5 MK. (2) The analyzed loops have a height of
2-3 scale heights, and thus only segments extending over about one
vertical scale height have sufficient emission measure contrast for
detection. (3) The temperature gradient over the lowest scale height
is of order dT/ds~1-10 K km-1. (4) The radiative loss
rate is found to exceed the conductive loss rate by about two orders
or magnitude in the coronal loop segments, implying that the loops
cannot be in quasi-static equilibrium, since standard steady-state loop
models show that radiative and conductive losses are comparable. (5) A
steady state could only be maintained if the heating rate EH
matches exactly the radiative loss rate in hydrostatic equilibrium,
requiring a heat deposition length λH of the half density
scale height λ. (6) We find a correlation of p~L-1 between
loop base pressure and loop length, which is not consistent with the
scaling law predicted from steady-state models of large-scale loops. All
observational findings indicate consistently that the energy balance
of the observed EUV loops cannot be described by steady-state models.

---------------------------------------------------------
Title: An Assessment of Magnetic Conditions for Strong Coronal
Heating in Solar Active Regions by Comparing Observed Loops with
Computed Potential Field Lines
Authors: Falconer, D. A.; Gary, G. A.; Moore, R. L.; Porter, J. G.
2000ApJ...528.1004F Altcode:
We report further results on the magnetic origins of coronal heating
found from registering coronal images with photospheric vector
magnetograms. For two complementary active regions, we use computed
potential field lines to examine the global nonpotentiality of bright
extended coronal loops and the three-dimensional structure of the
magnetic field at their feet, and assess the role of these magnetic
conditions in the strong coronal heating in these loops. The two
active regions are complementary, in that one is globally potential
and the other is globally nonpotential, while each is predominantly
bipolar, and each has an island of included polarity in its trailing
polarity domain. We find the following: (1) The brightest main-arch
loops of the globally potential active region are brighter than the
brightest main-arch loops of the globally strongly nonpotential active
region. (2) In each active region, only a few of the mainarch magnetic
loops are strongly heated, and these are all rooted near the island. (3)
The end of each main-arch bright loop apparently bifurcates above the
island, so that it embraces the island and the magnetic null above the
island. (4) At any one time, there are other main-arch magnetic loops
that embrace the island in the same manner as do the bright loops but
that are not selected for strong coronal heating. (5) There is continual
microflaring in sheared core fields around the island, but the main-arch
bright loops show little response to these microflares. From these
observational and modeling results we draw the following conclusions:
(1) The heating of the main-arch bright loops arises mainly from
conditions at the island end of these loops and not from their global
nonpotentiality. (2) There is, at most, only a loose coupling between
the coronal heating in the bright loops of the main arch and the coronal
heating in the sheared core fields at their feet, although in both the
heating is driven by conditions/events in and around the island. (3)
The main-arch bright loops are likely to be heated via reconnection
driven at the magnetic null over the island. The details of how and
where (along the null line) the reconnection is driven determine
which of the split-end loops are selected for strong heating. (4)
The null does not appear to be directly involved in the heating of
the sheared core fields or in the heating of an extended loop rooted
in the island. Rather, these all appear to be heated by microflares
in the sheared core field.

---------------------------------------------------------
Title: Magnetic field configuration of active region NOAA 6555 at
the time of a long-duration flare on 23 March 1991 - An Exception
to Standard Flare Reconnection Model
Authors: Choudhary, Debi Prasad; Gary, G. Allen
1999SoPh..188..345C Altcode:
The high-resolution Hα images observed during the decay phase
of a long-duration flare on 23 March 1991 are used to study the
three-dimensional magnetic field configuration of the active region NOAA
6555. Whereas all the large flares in NOAA 6555 occurred at the location
of high magnetic shear and flux emergence, this long-duration flare was
observed in the region of low magnetic shear at the photosphere. The Hα
loops activity started soon after the maximum phase of the flare. There
were a few long loop at the initial phase of the activity. Some of
these were sheared in the chromosphere at an angle of about 45° to
the east-west axis. Gradually, an increasing number of shorter loops,
oriented along the east-west axis, started appearing. The chromospheric
Dopplergrams show blue shifts at the end points of the loops. By using
different magnetic field models, we have extrapolated the photospheric
magnetograms to chromospheric heights. The magnetic field lines computed
by using the potential field model correspond to most of the observed
Hα loops. The height of the Hα loops were derived by comparing them
with the computed field lines. From the temporal evolution of the Hα
loop activity, we derive the negative rate of appearance of Hα features
as a function of height. It is found that the field lines oriented along
one of the neutral lines were sheared and low lying. The higher field
lines were mostly potential. The paper also outlines a possible scenario
for describing the post-flare stage of the observed long-duration flare.

---------------------------------------------------------
Title: β in streamers
Authors: Suess, S. T.; Gary, G. A.; Nerney, S. F.
1999AIPC..471..247S Altcode: 1999sowi.conf..247S
The ratio of thermal pressure to magnetic pressure (β) is greater
than unity above ~1.2RS in streamers.

---------------------------------------------------------
Title: Constructing the Coronal Magnetic Field By Correlating
Parameterized Magnetic Field Lines With Observed Coronal Plasma
Structures
Authors: Gary, G. Allen; Alexander, David
1999SoPh..186..123G Altcode:
A method is presented for constructing the coronal magnetic field
from photospheric magnetograms and observed coronal loops. A set of
magnetic field lines generated from magnetogram data is parameterized
and then deformed by varying the parameterized values. The coronal flux
tubes associated with this field are adjusted until the correlation
between the field lines and the observed coronal loops is maximized. A
mathematical formulation is described which ensures that (i) the
normal component of the photospheric field remains unchanged, (ii)
the field is given in the entire corona over an active region, (iii)
the field remains divergence-free, and (iv) electric currents are
introduced into the field. It is demonstrated that a parameterization
of a potential field, comprising a radial stretching of the field,
can provide a match for a simple bipolar active region, AR 7999,
which crossed the central meridian on 1996 November 26. The result is a
non-force-free magnetic field with the Lorentz force being of the order
of 10−5.5 g cm s−2 resulting from an electric
current density of 0.079 μA m−2. Calculations show that
the plasma beta becomes larger than unity at a relatively low height of
∼0.25 r⊙ supporting the non-force-free conclusion. The
presence of such strong non-radial currents requires large transverse
pressure gradients to maintain a magnetostatic atmosphere, required
by the relatively persistent nature of the coronal structures observed
in AR 7999. This scheme is an important tool in generating a magnetic
field solution consistent with the coronal flux tube observations and
the observed photospheric magnetic field.

---------------------------------------------------------
Title: Rendering Three-Dimensional Solar Coronal Structures of Active
Region 8227
Authors: Gary, G. A.; Alexander, D.; Fletcher, L.
1999AAS...194.7807G Altcode: 1999BAAS...31..962G
Coronal X-ray and EUV synthesized images of Active Region 8227
(May-June 1996) are constructed and compared with TRACE, Yohkoh/SXT, and
SOHO/EIT observations. Using the rendering technique of Gary (1997) and
Alexander, Gary, and Thompson (1998), specific geometric and physical
models are used to integrate the plasma emission along the line of sight
to obtain a rendered image. The instrumental profiles are convolved
in the integration process as well as unique heating functions. We
analyze coronal X-ray and EUV structures via the constructing of
synthesized images and investigate how different heating rates within
the active region loop system affect the emission characteristics. The
intercomparison of the emission seen in different telescopes with
that predicted by the assumed model provides a diagnostic tool for
determining the properties of the heating and a physical explanation for
the observed distributions. Of particular note is the presence of bright
EUV emission at the base of hot X-ray loops, reminiscent of the "moss"
observed by Berger &amp; et al. (1999), and Fletcher &amp; De Pontieu
(1999). Gary, G. A.: 1997, Solar Physics, 174, 241. Alexander, D.,
Gary, G. A., and Thompson, B.J.: 1998, Proc. 2nd ASPE, PASP Conference
Series. Berger, T. E., De Pontieu, B., Schrijver, C. J., Title, A. M.,
1999. ApJ Letts. (submitted) Fletcher, L., De Pontieu, B. 1999, ApJ
Letts. (submitted)

---------------------------------------------------------
Title: Three-dimensional Stereoscopic Analysis of Solar Active
Region Loops. I. SOHO/EIT Observations at Temperatures of (1.0-1.5)
× 106 K
Authors: Aschwanden, Markus J.; Newmark, Jeffrey S.; Delaboudinière,
Jean-Pierre; Neupert, Werner M.; Klimchuk, J. A.; Gary, G. Allen;
Portier-Fozzani, Fabrice; Zucker, Arik
1999ApJ...515..842A Altcode:
The three-dimensional structure of solar active region NOAA 7986
observed on 1996 August 30 with the Extreme-Ultraviolet Imaging
Telescope (EIT) on board the Solar and Heliospheric Observatory
(SOHO) is analyzed. We develop a new method of dynamic stereoscopy to
reconstruct the three-dimensional geometry of dynamically changing
loops, which allows us to determine the orientation of the mean
loop plane with respect to the line of sight, a prerequisite to
correct properly for projection effects in three-dimensional loop
models. With this method and the filter-ratio technique applied
to EIT 171 and 195 Å images we determine the three-dimensional
coordinates [x(s), y(s), z(s)], the loop width w(s), the electron
density ne(s), and the electron temperature Te(s)
as a function of the loop length s for 30 loop segments. Fitting the
loop densities with an exponential density model ne(h)
we find that the mean of inferred scale height temperatures,
Tλe=1.22+/-0.23 MK, matches closely that of EIT
filter-ratio temperatures, TEITe=1.21+/-0.06
MK. We conclude that these cool and rather large-scale loops (with
heights of h~30-225 Mm) are in hydrostatic equilibrium. Most of the
loops show no significant thickness variation w(s), but we measure
for most of them a positive temperature gradient (dT/ds&gt;0) across
the first scale height above the footpoint. Based on these temperature
gradients we find that the conductive loss rate is about 2 orders of
magnitude smaller than the radiative loss rate, which is in strong
contrast to hot active region loops seen in soft X-rays. We infer a
mean radiative loss time of τrad~40 minutes at the loop
base. Because thermal conduction is negligible in these cool EUV
loops, they are not in steady state, and radiative loss has entirely
to be balanced by the heating function. A statistical heating model
with recurrent heating events distributed along the entire loop can
explain the observed temperature gradients if the mean recurrence time
is &lt;~10 minutes. We computed also a potential field model (from
SOHO/MDI magnetograms) and found a reasonable match with the traced
EIT loops. With the magnetic field model we determined also the height
dependence of the magnetic field B(h), the plasma parameter β(h),
and the Alfvén velocity vA(h). No correlation was found
between the heating rate requirement EH0 and the magnetic
field Bfoot at the loop footpoints.

---------------------------------------------------------
Title: Complex H α Loop Activity in a Long Duration Flare
Authors: Prasad, D.; Gary, G.; Ambastha, A.
1999ASPC..183..523P Altcode: 1999hrsp.conf..523P
No abstract at ADS

---------------------------------------------------------
Title: Beta in Streamers
Authors: Suess, Steven T.; Gary, G. A.; Nerney, S. F.
1999AIPC..471.....S Altcode:
Streamers are often described as regions of the corona in which the
density is higher than in coronal holes because the plasma is trapped by
closed loops of magnetic flux. In contrast, Magnetohydrodynamics (MHD)
models of the global corona show that the plasma beta identically equal
to 8(pi)p/B2 &gt; 1 in streamers above approximately 1.2Rs
heliocentric height (p=pressure, B=magnetic field strength). There are
three recent contributions to this topic. The first is that heating
near the cusp further drives Beta up and can result in release of new
slow solar wind from the top of the streamer. The second is SOHO/UVCS
observations, in combination with a potential field/source surface
model of the magnetic field, show beta &gt; 1 above 1.2Rs in a streamer
observed near solar sunspot minimum. The third is a magnetic field
reconstruction technique (using field deforming algorithms) which was
applied both to an isolated active region (AR 7999) and to the Pneuman
&amp; Kopp global MHD model. In the active region, beta becomes larger
than unity at approximately 1.2Rs. In the Pneuman &amp; Kopp model,
beta = 1.0 at the base of the streamer and rises with increasing
height, becoming 15-20 at 1.6Rs and 35-55 at 1.7RS. The collective
implication of these three results is that beta &gt; 1 everywhere in
streamers above approximately 1.2 Rs. Global simulations go on to show
that the reason streamers do not simply explode under such high beta
conditions is that they are held down by pressure from the sides due
to the magnetic fields (and low beta) in adjacent coronal holes. The
main role of the closed magnetic loops near the cusp is to keep the
streamer from continuously leaking plasma, as otherwise happens in a
magnetic pinch which is similar but has no closed loops. The purpose
of this note is to summarize the results implying that beta &gt;
1 is a general property of streamers above 1.2 Rs.

---------------------------------------------------------
Title: On Analysis of Dual Spacecraft Stereoscopic Observations to
Determine the Three-Dimensional Morphology and Plasma Properties of
Solar Coronal Flux Tubes
Authors: Gary, G. Allen; Davis, John M.; Moore, Ronald
1998SoPh..183...45G Altcode:
By using two spacecraft equipped with multi-bandpass X-ray telescopes,
it is possible to obtain direct 3-dimensional morphology of coronal
structures which is essential for understanding the energetics and
dynamics of the solar atmosphere. X-ray observations taken only in
orbit about the Earth are inadequate to fully resolve the 3-dimensional
nature of the solar corona. These Earth-orbit observations produce
2-dimensional images and an appropriate model must be included
to derive the 3-dimensional structures from the line-of-sight
information. Stereoscopic observations from space will remove this
limitation and are needed if we are to improve our knowledge of the
3-dimensional morphology of the corona.

---------------------------------------------------------
Title: Report on new mission concept study: Stereo X-Ray Corona
Imager mission
Authors: Liewer, Paulett C.; Davis, John M.; de Jong, E. M.; Gary,
G. A.; Klimchuk, James A.; Reinert, Richard P.
1998SPIE.3442...53L Altcode:
Studies of the 3D structure and dynamics of the solar corona
have been severely limited by the constraint of single viewpoint
observations. The Stereo X-Ray Coronal Imager (SXCI) mission will send
a single instrument, an X-ray telescope, into deep space expressly to
record stereoscopic images of the solar corona. The SXCI spacecraft
will be inserted into an approximately 1 ZAU heliocentric orbit leading
Earth by approximately 25 degrees at the end of nine months. The SXCI
x-ray telescope forms one element of a stereo pair, the second element
being an identical x-ray telescope in Earth orbit placed there as part
of the NOAA GOES program. X-ray emission is a powerful diagnostic of
the corona and its magnetic fields, and 3D information on the coronal
magnetic structure would be obtained by combining the data from the
two x-ray telescopes. This information can be used to address the major
solar physics questions of (1) what causes explosive coronal events such
as coronal mass ejections, eruptive flares and prominence eruptions and
(2) what causes the transient heating of coronal loops. Stereoscopic
views of the optically thin corona will resolve some ambiguities
inherent in single line-of-sight observations. Triangulation gives 3D
solar coordinates of features which can be seen in the simultaneous
images form both telescopes. As part of this study, tools were
developed for determining the 3D geometry of coronal features using
triangulation. Advanced technologies for visualization and analysis of
stereo images were tested. Results of mission and spacecraft studies
are also reported.

---------------------------------------------------------
Title: 3D-Stereoscopic Analysis of Solar Active Region Loops Observed
with SOHO/EIT
Authors: Aschwanden, M. J.; Newmark, J. S.; Delaboudiniere, J. -P.;
Neupert, W. M.; Klimchuk, J. A.; Gary, G. Allen; Portier-Fozzani,
F.; Zucker, A.
1998cee..workE..19A Altcode:
The three-dimensional (3D) structure of solar active region NOAA
7986 observed on 1996 August 30 with the Extrem-ultraviolet Imaging
Telescope (EIT) onboard the Solar and Heliospheric Observatory
(SoHO) is analyzed. We develop a new method of Dynamic Stereoscopy to
reconstruct the 3D geometry of dynamically changing loops, which allows
us to determine the orientation of the loop plane with respect to
the line-of-sight, a prerequisite to correct properly for projection
effects in 3D loop models. With this method and the filter-ratio
technique applied to EIT 171 angle and 195 angle images we determine
the 3D coordinates [x(s),y(s),z(s)], the loop width w(s), the electron
density n_e(s), and the electron temperature T_e(s) as function of
the loop length s for 30 loop segments. Fitting the loop densities
with an exponential density model n_e(h) we find that the mean of
inferred scale height temperatures, T_elambda = 1.22 plus or
minus 0.23 MK, matches closely that of EIT filter-ratio temperatures,
T_eEIT = 1.21 plus or minus 0.06 MK. We conclude that these
cool and rather large-scale loops (with heights of h ~30-225 Mm), which
dominate the EIT 171 angle images, are in hydrostatic equilibrium. Most
of the loops show no significant thickness variation w(s), but we can
measure for most of them a positive temperature gradient (dT/ds &gt;
0) across the first scale height above the footpoint. Based on these
temperature gradients we find that the conductive loss rate is about
two orders of magnitude smaller than the radiative loss rate, which is
in strong contrast to hot active region loops seen in SXR. We infer a
mean radiative loss time of τrad ~40 minutes. For steady
state models, the heating rate has to balance the radiative loss,
i.e. the heating rate has to scale with the squared density (E_H
propto n_e^2). From potential-field extrapolations we determine also
the magnetic field strength B(s), the plasma beta-parameter beta(s),
and the Alfven velocity v_A(s) along the loops, and discuss the findings
in the context of coronal heating models.

---------------------------------------------------------
Title: Analysis of Active Regions via 3D Rendering Techniques
Authors: Alexander, D.; Gary, G. Allen; Thompson, B. J.
1998ASPC..155..100A Altcode: 1998sasp.conf..100A
No abstract at ADS

---------------------------------------------------------
Title: Measurements and analyses of the 3-D solar magnetic
fields. Proceedings. Workshop, Huntsville, AL (USA), 9 - 11 Apr 1996.
Authors: Wu, S. -T.; Gary, G. A.
1997SoPh..174....1W Altcode:
Dedicated to Yoshinari Nakagawa.

---------------------------------------------------------
Title: Rendering Three-Dimensional Solar Coronal Structures
Authors: Gary, G. Allen
1997SoPh..174..241G Altcode:
An X-ray or EUV image of the corona or chromosphere is a 2D
representation of an extended 3D complex for which a general inversion
process is impossible. A specific model must be incorporated in order to
understand the full 3D structure. We approach this problem by modeling
a set of optically-thin 3D plasma flux tubes which we render these as
synthetic images. The resulting images allow the interpretation of the
X-ray/EUV observations to obtain information on (1) the 3D structure of
X-ray images, i.e., the geometric structure of the flux tubes, and on
(2) the internal structure using specific plasma characteristics, i.e.,
the physical structure of the flux tubes. The data-analysis technique
uses magnetograms to characterize photospheric magnetic fields and
extrapolation techniques to form the field lines. Using a new set of
software tools, we have generated 3D flux tube structures around these
field lines and integrated the plasma emission along the line of sight
to obtain a rendered image. A set of individual flux-tube images is
selected by a non-negative least-squares technique to provide a match
with an observed X-ray image. The scheme minimizes the squares of
the differences between the synthesized image and the observed image
with a non-negative constraint on the coefficients of the brightness
of the individual flux-tube loops. The derived images are used to
determine the specific photospheric foot points and physical data,
i.e., scaling laws for densities and loop lengths. The development
has led to computer efficient integration and display software that
is compatible for comparison with observations (e.g., Yohkoh SXT data,
NIXT, or EIT). This analysis is important in determining directly the
magnetic field configuration, which provides the structure of coronal
loops, and indirectly the electric currents or waves, which provide
the energy for the heating of the plasma. We have used very simple
assumptions (i.e., potential magnetic fields and isothermal corona)
to provide an initial test of the techniques before complex models are
introduced. We have separated the physical and geometric contributions
of the emission for a set of flux tubes and concentrated, in this
initial study, on the geometric contributions by making approximations
to the physical contributions. The initial results are consistent with
the scaling laws derived from the Yohkoh SXT data.

---------------------------------------------------------
Title: Neutral-Line Magnetic Shear and Enhanced Coronal Heating in
Solar Active Regions
Authors: Falconer, D. A.; Moore, R. L.; Porter, J. G.; Gary, G. A.;
Shimizu, T.
1997ApJ...482..519F Altcode:
By examining the magnetic structure at sites in the bright coronal
interiors of active regions that are not flaring but exhibit persistent
strong coronal heating, we establish some new characteristics of
the magnetic origins of this heating. We have examined the magnetic
structure of these sites in five active regions, each of which was well
observed by both the Yohkoh SXT and the Marshall Space Flight Center
Vector Magnetograph and showed strong shear in its magnetic field along
part of at least one neutral line (polarity inversion). Thus, we can
assess whether this form of nonpotential field structure in active
regions is a characteristic of the enhanced coronal heating and vice
versa. From 27 orbits' worth of Yohkoh SXT images of the five active
regions, we have obtained a sample of 94 persistently bright coronal
features (bright in all images from a given orbit), 40 long (&gt;~20,000
km) neutral-line segments having strong magnetic shear throughout
(shear angle greater than 45°), and 39 long neutral-line segments
having weak magnetic shear throughout (shear angle less than 45°). From
this sample, we find that (1) all of our persistently bright coronal
features are rooted in magnetic fields that are stronger than 150 G,
(2) nearly all (95%) of these enhanced coronal features are rooted near
neutral lines (closer than 10,000 km), (3) a great majority (80%) of the
bright features are rooted near strong-shear portions of neutral lines,
(4) a great majority (85%) of long strong-shear segments of neutral
lines have persistently bright coronal features rooted near them, (5)
a large minority (40%) of long weak-shear segments of neutral lines
have persistently bright coronal features rooted near them, and (6)
the brightness of a persistently bright coronal feature often changes
greatly over a few hours. From these results, we conclude that most
persistent enhanced heating of coronal loops in active regions (1)
requires the presence of a polarity inversion in the magnetic field
near at least one of the loop footpoints, (2) is greatly aided by the
presence of strong shear in the core magnetic field along that neutral
line, and (3) is controlled by some variable process that acts in this
magnetic environment. We infer that this variable process is low-lying
reconnection accompanying flux cancellation.

---------------------------------------------------------
Title: Evidence that Strong Coronal Heating Results from Photospheric
Magnetic Flux Cancellation
Authors: Moore, R. L.; Falconer, D. A.; Porter, J. G.; Gary, G. A.;
Shimizu, T.
1996AAS...188.8604M Altcode: 1996BAAS...28..963M
Soft X-ray images of the Sun's corona, such as those from the Yohkoh
SXT, show that the sites of strongest persistent (non-flare) coronal
heating are located within the strong (&gt;100 gauss) magnetic fields
in sunspot regions and are limited to only certain places within these
stong-field domains, covering only a fraction of the total area. We have
examined the structure of the magnetic field at these sites in 5 active
regions by superposing Yohkoh SXT coronal X-ray images on MSFC vector
magnetograms. We find: (1) nearly all of the enhanced (outstandingly
bright) coronal features that persist for tens of minutes are rooted
near polarity neutral lines in the photospheric magnetic flux; (2) in
most cases the core magnetic field closely straddling the neutral line
at the root of the strong heating is strongly sheared; (3) the enhanced
coronal X-ray brightness in the low-lying core fields shows spatial
substructure that fluctuates on time scales of minutes, in the manner
of microflaring; and (4) large parts of extensive enhanced coronal
features often last for no more than a few hours. From these results,
it appears that most enhanced coronal heating in active regions is a
consequence of some process that (1) acts only in the presence of a
photospheric polarity neutral line, (2) is episodic on times of about
an hour, (3) usually gives stronger coronal heating in the presence of
stronger magnetic shear, but is not required to act by the presence of
magnetic shear, and (4) is often accompanied by microflaring in the
core field. We point out that magnetic flux cancellation (driven by
photospheric flows at the neutral line) is a process that plausibly
meets all these requirements. The flux cancellation might directly
drive microflaring, or trigger microflaring in the sheared core field,
or both. The microflaring might directly produce the enhanced coronal
heating in the core fields as well as generate MHD waves that propagate
up into the enhanced extended coronal loops to provide the strong
coronal heating in these.

---------------------------------------------------------
Title: Potential Field Extrapolation Using Three Components of a
Solar Vector Magnetogram with a Finite Field of View
Authors: Gary, G. Allen
1996SoPh..163...43G Altcode:
The potential magnetic field from a finite planar boundary is
extrapolated into the upper hemisphere using information from all
three magnetic field components. The method determines, first,
the transverse field associated with the observed normal magnetic
intensity. Then by subtraction, the method determines the associated
transverse magnetic field observed in the interior (i.e., in the field
of view) of the magnetogram which is due to the normal flux exterior
to the field of view of the magnetogram. Inverting this information
gives an approximation to the exterior normal flux. The combination of
the observed normal flux of the interior and the approximation of the
exterior normal flux is employed to calculate the potential field. The
formulation of the problem results in an ill-posed integral inversion
problem in which a regularized solution is obtained using the singular
value decomposition (SVD) technique in conjunction with an appropriate
Tikhonov-Phillips filter. The technique can be applied to correcting
potential field calculations which are influenced by out-of-view
fluxes, e.g., for a high spatial resolution vector magnetogram with a
small field of view in which there is no supporting exterior data. The
problem studied is also important in providing a regularized solution
of the Cauchy potential problem. The method provides a much larger
range of convergence than the method of Gary and Musielak (1992), and,
in fact, is stable in the total upper hemisphere.

---------------------------------------------------------
Title: Reduction, Analysis, and Properties of Electric Current
Systems in Solar Active Regions
Authors: Gary, G. Allen; Demoulin, Pascal
1995ApJ...445..982G Altcode:
The specific attraction and, in large part, the significance of solar
magnetograms lie in the fact that they give the most important data on
the electric currents and the nonpotentiality of active regions. Using
the vector magnetograms from the Marshall Space Flight Center (MSFC),
we employ a unique technique in the area of data analysis for resolving
the 180 deg ambiguity in order to calculate the spatial structure of the
vertical electric current density. The 180 deg ambiguity is resolved
by applying concepts from the nonlinear multivariable optimization
theory. The technique is shown to be of particular importance in very
nonpotential active regions. The characterization of the vertical
electric current density for a set of vector magnetograms using this
method then gives the spatial scale, locations, and magnitude of these
current systems. The method, which employs an intermediate parametric
function which covers the magnetogram and which defines the local
`preferred' direction, minimizes a specific functional of the observed
transverse magnetic field. The specific functional that is successful is
the integral of the square of the vertical current density. We find that
the vertical electric current densities have common characteristics for
the extended bipolar (beta) (gamma) (delta)-regions studied. The largest
current systems have jz's which maximizes around 30 mA/sq
m and have a linear decreasing distribution to a diameter of 30 Mn.

---------------------------------------------------------
Title: Line-of-sight magnetic flux imbalances caused by electric
currents
Authors: Gary, G. Allen; Rabin, Douglas
1995SoPh..157..185G Altcode: 1995SoPh..157..185A
Several physical and observational effects may contribute to the
significant imbalances of magnetic flux that are often observed in
active regions. We consider an effect not previously treated: the
influence of electric currents in the photosphere. Electric currents can
cause a line-of-sight flux imbalance because of the directionality of
the magnetic field they produce. Currents associated with magnetic flux
tubes produce larger imbalances than do smoothly-varying distributions
of flux and current. We estimate the magnitude of this effect for
current densities, total currents, and magnetic geometry consistent
with observations. The expected imbalances lie approximately in
the range 0-15%, depending on the character of the current-carrying
fields and the angle from which they are viewed. Observationally,
current-induced flux imbalances could be indicated by a statistical
dependence of the imbalance on angular distance from disk center. A
general study of magnetic flux balance in active regions is needed to
determine the relative importance of other - probably larger -effects
such as dilute flux (too weak to measure or rendered invisible by
radiative transfer effects), merging with weak background fields,
and long-range connections between active regions.

---------------------------------------------------------
Title: Electric Current Systems in Solar Active Regions
Authors: Gary, G. Allen; Demoulin, Pascal
1994ASPC...68..171G Altcode: 1994sare.conf..171G
No abstract at ADS

---------------------------------------------------------
Title: Understanding Solar Active Phenomena: A Phenomenological
Approach
Authors: Machado, M. E.; Demoulin, P.; Gary, G. A.; Henoux, J. C.;
Mandrini, C. H.; Rovira, M. G.
1994step.conf..125M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Interpretation of Magnetic Field Structures from Observations
of Active Region AR 6659 in 1991 June 8-11
Authors: Wu, S. T.; Weng, F. S.; Hagyard, M. J.; Gary, G. A.
1993BAAS...25.1218W Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Interactive Flare Sites Within an Active Region Complex
Authors: Poletto, G.; Gary, G. A.; Machado, M. E.
1993SoPh..144..113P Altcode:
The problem of physical relationships between different active
regions has been dealt with only rarely and mainly in connection
with flares. How sympathetic activity can be triggered between
distant regions is therefore, so far, largely unknown. Soft X-ray
images of large-scale coronal structures connecting different active
regions were obtained by Skylab nearly 20 years ago, while SMM,
more recently, did not provide any clear evidence for this kind of
loop. As a consequence, we do not know how common these features are
nor how they form nor whether they represent the only means by which
distant active regions may be linked. In the latter case, however,
interconnecting loops should be detected by analyzing the interaction
between different active regions. We examine here a set of images of
an active region complex, acquired on June 24-25, 1980, by the Hard
X-ray Imaging Spectrometer on SMM, with the purpose of establishing
whether there was any interplay between the frequent activity observed
at different sites in the activity center and, in such a case, how the
interaction was established. By analyzing both quiet and active orbits
we show that, as a rule, activity originating in one region triggers the
other region's activity. However, we find little unambiguous evidence
for the presence of large-scale interconnecting loops. A comparison
of X-ray images with magnetic field observations suggested that we
interpret the active region behavior in terms of the interaction
between different loop systems, in a scenario quite analogous to the
interacting bipole representation of individual flares. We conclude
that active region interplay provides an easily observable case to
study the time-dependent topology and the mechanisms for the spreading
of activity in transient events over all energy scales.

---------------------------------------------------------
Title: A Regularization Method for Extrapolation of Solar Potential
Magnetic Fields
Authors: Gary, G. A.; Musielak, Z. E.
1992ApJ...392..722G Altcode:
The mathematical basis of a Tikhonov regularization method for
extrapolating the chromospheric-coronal magnetic field using
photospheric vector magnetograms is discussed. The basic techniques
show that the Cauchy initial value problem can be formulated for
potential magnetic fields. The potential field analysis considers a
set of linear, elliptic partial differential equations. It is found
that, by introducing an appropriate smoothing of the initial data
of the Cauchy potential problem, an approximate Fourier integral
solution is found, and an upper bound to the error in the solution is
derived. This specific regularization technique, which is a function
of magnetograph measurement sensitivities, provides a method to
extrapolate the potential magnetic field above an active region into
the chromosphere and low corona.

---------------------------------------------------------
Title: On Neutralized Currents in the Solar Corona
Authors: Wilkinson, Ladye K.; Emslie, A. G.; Gary, G. A.
1992ApJ...392L..39W Altcode:
Using Ampere's integral law applied to vector magnetograph transverse
field data, the current pattern in an active region associated with
flaring activity is analyzed. The greater sensitivity of this integral
formalism of Ampere's law may allow one to identify regions of weak
return current around the actual positive current region. The effects
of Faraday rotation on the inferred magnetic field measurements, and
hence on the deduced current pattern, are discussed. It is concluded
that the current patterns in the region consist either of a neutralized
current system, well modeled by a coaxial cable, or of a potential
field, with the apparent currents in the core an artifact induced by
magneto-optical effects. In either case, the data do not convincingly
show an unneutralized current system.

---------------------------------------------------------
Title: Interacting Confined-Eruptive Flare Sites Within a Magnetic
Active Region Complex
Authors: Gary, G. A.; Poletto, G.; Mechado, M. E.
1992AAS...180.4106G Altcode: 1992BAAS...24Q.795G
No abstract at ADS

---------------------------------------------------------
Title: The MSFC Solar GRO Guest Investigation
Authors: Hagyard, M. J.; Gary, G. A.; Moore, R. L.
1991BAAS...23.1073H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Magnetic Field Changes Associated with a Subflare and Surge
Authors: Hagyard, M. J.; West, E. A.; Gary, G. A.; Smith, J. E.
1991BAAS...23.1030H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A Regularization Method for the Extrapolation of Solar
Magnetic Fields
Authors: Gary, G. A.; Musielak, Z.
1991BAAS...23.1031G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Solar vector magnetic field measurements.
Authors: Gary, G. A.; Hagyard, M. J.; West, E. A.
1991sopo.work...65G Altcode:
This paper contains a discussion of recent results with the Marshall
Space Flight Center's (MSFC) filter vector magnetograph and the
co-aligned Hα telescope. This report emphasizes total vector magnetic
measurements and the co-spatial, co-temporal Hα observations. The
observations reported include magnetic shear data along the neutral
inversion line, vector field measurements below prominences,
and vector magnetic field measurements associated with flares and
surge activity. The importance of a large field of view and high
polarimetric sensitivity in solar vector magnetic field measurements
is also discussed.

---------------------------------------------------------
Title: On the Numerical Computation of Nonlinear Force-free Magnetic
Fields
Authors: Wu, S. T.; Sun, M. T.; Chang, H. M.; Hagyard, M. J.; Gary,
G. A.
1990ApJ...362..698W Altcode:
An algorithm has been developed to extrapolate nonlinear force-free
magnetic fields from the photosphere, given the proper boundary
conditions. This paper presents the results of this work, describing
the mathematical formalism that was developed, the numerical techniques
employed, and comments on the stability criteria and accuracy developed
for these numerical schemes. An analytical solution is used for a
benchmark test; the results show that the computational accuracy for
the case of a nonlinear force-free magnetic field was on the order of
a few percent (less than 5 percent). This newly developed scheme was
applied to analyze a solar vector magnetogram, and the results were
compared with the results deduced from the classical potential field
method. The comparison shows that additional physical features of the
vector magnetogram were revealed in the nonlinear force-free case.

---------------------------------------------------------
Title: Coaligned observations of solar magnetic fields at different
heights: MSFC Center director's discretionary fund final report
(Project No. 88-10)
Authors: Hagyard, M. J.; West, E. A.; Gary, G. A.; Smith, J. E.
1990STIN...9110832H Altcode:
The objective was to develop the capability for and coaligned
observations of the structure and evolution of the Sun's magnetic field
at two different heights in the solar atmosphere: the photosphere,
which is the lowest region observable with optical telescopes;
and the chromosphere, which lies just above the photosphere and
is the region where the magnetic field dominates the gas motion so
that a well-ordered structure governed by the field is observed. By
obtaining this three-dimensional picture of the solar magnetic field,
a better understanding can be developed of the magnetic forces that
produce and control the dynamic, high-energy phenomena occurring in
the solar atmosphere that can affect the entire heliosphere, including
the terrestrial environment.

---------------------------------------------------------
Title: A lunar based solar observatory rationale and concepts
Authors: Davis, John M.; Balasubramaniam, K. S.; Gary, G. A.; Moore,
Ronald L.
1990AIPC..207..567D Altcode: 1990am...proc..567D
The rationale for a lunar solar observatory is described and the
requirements for various candidate instruments are developed. The unique
characteristics of the lunar surface, its stability, low seismicity,
and long unobstructed paths make it an ideal site for a large, high
performance optical telescope. The capabilities of such an instrument is
used, as an example (1) for the science that might be achieved from the
lunar surface, (2) to identify the magnitude of the instrumentation,
and (3) to indicate the technologies that must be developed if such
an observatory is to become a reality.

---------------------------------------------------------
Title: Transformation of vector magnetograms and the problems
associated with the effects of perspective and the azimuthal ambiguity
Authors: Gary, G. Allen; Hagyard, M. J.
1990SoPh..126...21G Altcode:
Off-center vector magnetograms which use all three components of
the measured field provide the maximum information content from the
photospheric field and can provide the most consistent potential field
independent of the viewing angle by defining the normal component of
the field. The required transformations of the magnetic field vector
and the geometric mapping of the observed field in the image plane into
the heliographic plane have been described. Here we discuss the total
transformation of specific vector magnetograms to detail the problems
and procedures that one should be aware of in analyzing observational
magnetograms. The effect of the 180-deg ambiguity of the observed
transverse field is considered as well as the effect of curvature of
the photosphere. Specific results for active regions AR 2684 (September
23, 1980) and AR 4474 (April 26, 1984) from the Marshall Space Flight
Center Vector magnetograph are described which point to the need for
the heliographic projection in determining the field structure of an
active region.

---------------------------------------------------------
Title: Concerning the extrapolation of solar nonlinear force-free
magnetic fields
Authors: Gary, G. Allen
1990MmSAI..61..457G Altcode:
This paper contains a review and discussion of the mathematical basis
of the extrapolation techniques involved in using photospheric vector
magnetograms to obtain the coronal field above the surface. The two
basic techniques employing the Cauchy initial value problem and the
variational techniques are reviewed in terms of the mathematical and
practical applications. A short review is presented of the current
research on numerical modeling techniques in the area of extrapolating
vector magnetograms; specifically, algorithms to extrapolate nonlinear
force-free magnetic fields from the photosphere are considered.

---------------------------------------------------------
Title: Off Disk Center Potential Field Calculations Using Vector
Magnetograms
Authors: Venkatakrishnan, P.; Gary, G. Allen
1989SoPh..120..235V Altcode:
We investigate a potential field calculation for off disk-center
vector magnetograms that uses all the three components of the measured
field. There is neither any need for interpolation of grid points
between the image plane and the heliographic plane nor for an extension
or a truncation to a heliographic rectangle. Hence, the method provides
the maximum information content from the photospheric field as well
as the most consistent potential field independent of the viewing
angle. The introduction of polarimetric noise produces a less tolerant
extrapolation procedure than using the line-of-sight extrapolation,
but the resultant standard deviation is still small enough for the
practical utility of this method.

---------------------------------------------------------
Title: The Effects of Viewing Angle on the Inference of Magnetic
Shear in Preflare Active Regions
Authors: Wilkinson, Ladye Kathryn; Emslie, Gordon A.; Gary, G. Allen
1989SoPh..119...77W Altcode:
The magnetic shear at a point within an active region field
configuration can be defined (Hagyard et al., 1984b) as the difference
in angle between the observed photospheric transverse field and that of
a reference potential field calculated using the observed line-of-sight
field as a boundary condition. Using analytic models for non-potential
(but force-free) fields representative of preflaring active regions,
we calculate the degree of magnetic shear along the magnetic neutral
line that such fields would exhibit, as a function of the location
and orientation of the active region on the solar disk. We find that,
except for regions close to disk center, the position of the inferred
neutral line (zero line-of-sight field) is significantly different
from the actual neutral line (zero radial field), and that the
calculated reference potential field also varies significantly with
the position of the region. Thus the inferred degree of shear can
vary significantly with the position and orientation of the region,
due to (a) straightforward geometric projection effects, (b) the shift
of the inferred neutral line relative to its true position, and (c)
variations in the reference potential field. The significance of these
results for flare prediction is considered.

---------------------------------------------------------
Title: Problems in the Analysis of Off-Disk Center Vector Magnetograms
Authors: Gary, G. A.; Hagyard, M. J.
1989BAAS...21Q.838G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Design of the polarimeter for the Solar Activity Measurements
Experiments (SAMEX) vector magnetograph.
Authors: West, E. A.; Reichmann, E. J.; Hagyard, M. J.; Gary, G. A.
1989OptEn..28..131W Altcode:
In a study by the Marshall Space Flight Center (MSFC) for the Air
Force Geophysics Laboratory (AFGL), a design concept was developed
for a polarimeter on the vector magnetograph of the SAMEX satellite
(Solar Activity Measurements Experiments) that would be very sensitive
to solar vector magnetic fields. Analysis of the polarimeter designs to
minimize crosstalk between incident circularly polarized light and the
linear polarization measurement is stressed. After a polarimeter design
is selected, the calibration techniques to determine the systematic
errors in the "perfect" polarimeter are discussed.

---------------------------------------------------------
Title: Linear Force-free Magnetic Fields for Solar Extrapolation
and Interpretation
Authors: Gary, G. Allen
1989ApJS...69..323G Altcode:
This paper discusses the interconnection of the various linear
force-free magnetic field formulations, the specific phenomenological
and topological parameters of these formulations, and their
usefulness. Particularly, the limitations and usefulness of linear
force-free fields are discussed. Specific field configurations are
related to magnetographic interpretation. The relationship of the
integral and Fourier procedures is shown explicitly. The physical
interpretation of linear force-free fields is shown by analytic models
and from the Marshall Space Flight Center solar vector magnetograms.

---------------------------------------------------------
Title: Development of the SAMEX vector magnetograph at the Marshall
Space Flight Center
Authors: West, E. A.; Hagyard, M. J.; Gary, G. A.; Arnett, G. M.
1988fnsm.work...86W Altcode:
A breadboard design to prove the operational feasibility of SAMEX
Vector Magnetograph is being developed. Although the breadboard
design will not include all of the elements of the original design
concept, critical elements such as the large detector array and the
high resolution polarimeter will be important parts of the breadboard
design to study the data analysis and compression techniques that will
be needed in a SAMEX instrument, to study the calibration techniques for
systemmatic errors in the polarimeter, and to obtain high resolution
vector magnetograms during the next solar maximum. Although the SAMEX
polarimeter is not optimum for a ground-based patrol instrument,
the design concept can be confirmed with ground-based measurements
and direct comparisons with the existing vector magnetograph. The
extension of the scientific objectives for this breadboard design is
possible if a tunable filter can be acquired.

---------------------------------------------------------
Title: Active Region Coronal Loops: Structure and Variability
Authors: Haisch, Bernhard M.; Strong, Keith T.; Harrison, Richard A.;
Gary, G. A.
1988ApJS...68..371H Altcode:
X-ray images of a pair of active region loops are studied which show
significant, short time-scale variability in the line fluxes of O VIII,
Ne IX, and Mg XI and in the 3.5-11.5 keV soft X-ray bands. Vector
magnetograms and high-resolution UV images were used to model the
three-dimensional characteristics of the loops. X-ray light curves were
generated spanning four consecutive orbits for both loops individually,
and light curves of the loop tops and brightest points were also
generated. The largest variations involve flux changes of up to several
hundred percent on time scales of 10 minutes. No significant H-alpha
flare activity is reported, and loop temperatures remain in the four
to six million K range. The decay phases of the light curves indicate
radiative cooling, inhibition of conduction, and some type of 'continued
heating' due to ongoing, underlying activity at the microflare level.

---------------------------------------------------------
Title: The SAMEX vector magnetograph. A design study for a space-based
solarvector magnetograph.
Authors: Hagyard, M. J.; Gary, G. A.; West, E. A.
1988NASTM4048.....H Altcode: 1988STIN...8825424H
This report presents the results of a study performed to develop
a design concept for a space-based solar vector magnetograph and
hydrogen-alpha telescope. These instruments are two of the core
instruments for a proposed Air Force mission, the Solar Activity
Measurements Experiments (SAMEX). This mission is designed to study
the processes which give rise to solar activity in the solar atmosphere
and to develop techniques for predicting solar activity and its effect
on the terrestrial environment.

---------------------------------------------------------
Title: Chromospheric Emission Bifurcation of Sunspots
Authors: Gary, G. A.; Moore, R. L.
1988BAAS...20..704G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Development of an Image Processing System to Study Changes
in Coaligned Vector Magnetograms and H-alpha Images
Authors: West, E. A.; Hagyard, M. J.; Gary, G. A.
1988BAAS...20..711W Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Development of the SAMEX Vector Magnetograph at the Marshall
Space Flight Center
Authors: West, E. A.; Hagyard, M. J.; Gary, G. A.; Arnett, G. M.
1988BAAS...20Q.745W Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Nonpotential Features Observed in the Magnetic Field of an
Active Region
Authors: Gary, G. A.; Moore, R. L.; Hagyard, M. J.; Haisch, Bernhard M.
1987ApJ...314..782G Altcode:
A unique coordinated data set consisting of vector magnetograms,
H-alpha photographs, and high-resolution ultraviolet images of a
solar active region is used, together with mathematical models, to
calculate potential and force-free magnetic field lines and to examine
the nonpotential nature of the active region structure. It is found
that the overall bipolar magnetic field of the active region had a net
twist corresponding to net current of order 3 x 10 to the 12th A and
average density of order 4 x 10 to the -4th A/sq m flowing antiparallel
to the field. There were three regions of enhanced nonpotentiality
in the interior of the active region; in one the field had a marked
nonpotential twist or shear with height above the photosphere. The
measured total nonpotential magnetic energy stored in the entire
active region was of order 10 to the 32nd ergs, about 3 sigma above
the noise level.

---------------------------------------------------------
Title: Preflare magnetic and velocity fields
Authors: Hagyard, M. J.; Gaizauskas, V.; Chapman, G. A.; Deloach,
A. C.; Gary, G. A.; Jones, H. P.; Karpen, J. T.; Martres, M. -J.;
Porter, J. G.; Schmeider, B.
1986epos.conf.1.16H Altcode: 1986epos.confA..16H
A characterization is given of the preflare magnetic field, using
theoretical models of force free fields together with observed field
structure to determine the general morphology. Direct observational
evidence for sheared magnetic fields is presented. The role of this
magnetic shear in the flare process is considered within the context
of a MHD model that describes the buildup of magnetic energy, and the
concept of a critical value of shear is explored. The related subject
of electric currents in the preflare state is discussed next, with
emphasis on new insights provided by direct calculations of the vertical
electric current density from vector magnetograph data and on the role
of these currents in producing preflare brightenings. Results from
investigations concerning velocity fields in flaring active regions,
describing observations and analyses of preflare ejecta, sheared
velocities, and vortical motions near flaring sites are given. This
is followed by a critical review of prevalent concepts concerning the
association of flux emergence with flares

---------------------------------------------------------
Title: Accuracy Requirements for Vector Magnetic Field Measurements
for Solar Flare Prediction
Authors: Moore, R. L.; Gary, G. A.; Hagyard, M. J.; Davis, J. M.
1986BAAS...18.1043M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A digital imaging photometry system for cometary data
acquisition
Authors: Clifton, K. S.; Benson, C. M.; Gary, G. A.
1986nasa.reptV....C Altcode:
This report describes a digital imaging photometry system developed in
the Space Science Laboratory at the Marshall Space Flight center. The
photometric system used for cometary data acquisition is based on an
intensified secondary electron conduction (ISEC) vidicon coupled to a
versatile data acquisition system which allows real-time interactive
operation. Field tests on the Orion and Rosette nebulas indicate
a limiting magnitude of approximately mv = 14 over
the 40 arcmin field-of-view. Observations were conducted of Comet
Giacobini-Zinner in August 1985. The resulting data are discussed
in relation to the capabilities of the digital analysis system. The
development program concluded on August 31, 1985.

---------------------------------------------------------
Title: Non-Potential Features Observed in the Magnetic Field of an
Active Region
Authors: Gary, G. A.; Moore, R. L.; Hagyard, M. J.; Haisch, B. M.
1986BAAS...18..709G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Preflare activity.
Authors: Priest, E. R.; Gaizauskas, V.; Hagyard, M. J.; Schmahl, E. J.;
Webb, D. F.; Cargill, P.; Forbes, T. G.; Hood, A. W.; Steinolfson,
R. S.; Chapman, G. A.; Deloach, A. C.; Gary, G. A.; Jones, H. P.;
Karpen, J. T.; Martres, M. -J.; Porter, J. G.; Schmieder, B.; Smith,
J. B., Jr.; Toomre, J.; Woodgate, B.; Waggett, P.; Bentley, R.;
Hurford, G.; Schadee, A.; Schrijver, J.; Harrison, R.; Martens, P.
1986NASCP2439....1P Altcode:
Contents: 1. Introduction: the preflare state - a review of previous
results. 2. Magnetohydrodynamic instability: magnetic reconnection,
nonlinear tearing, nonlinear reconnection experiments, emerging flux and
moving satellite sunspots, main phase reconnection in two-ribbon flares,
magnetic instability responsible for filament eruption in two-ribbon
flares. 3. Preflare magnetic and velocity fields: general morphology of
the preflare magnetic field, magnetic field shear, electric currents in
the preflare active region, characterization of the preflare velocity
field, emerging flux. 4. Coronal manifestations of preflare activity:
defining the preflare regime, specific illustrative events, comparison
of preflare X-rays and ultraviolet, preflare microwave intensity and
polarization changes, non-thermal precursors, precursors of coronal
mass ejections, short-lived and long-lived HXIS sources as possible
precursors.

---------------------------------------------------------
Title: Characteristics, location and origin of flare activity in a
complex active region
Authors: Mechado, M. E.; Gary, G. A.; Hagyard, M. J.; Hernandez,
A. M.; Rovira, M. G.; Schmieder, B.; Smith, J. B.
1986AdSpR...6f..33M Altcode: 1986AdSpR...6...33M
We summarize the observational characteristics of series of multiple
loop flares from a complex active region. The location of the
highest observed photospheric magnetic shear is found to be the
commonly observed site of flare onset, but not, in many cases, the
magnetic region where the largest time-integrated energy release is
observed. The observations thus reveal a consistent pattern of energy
release processes as related to the magnetic field topology.

---------------------------------------------------------
Title: A Variational Approach to the Non-Linear Force-Free Magnetic
Fields
Authors: Gary, G. Allen
1985BAAS...17..641G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Computation of Solar Magnetic Fields from Photospheric
Observations
Authors: Hannakam, L.; Gary, G. A.; Teuber, D. L.
1984SoPh...94..219H Altcode:
The observational difficulties of obtaining the magnetic field
distribution in the chromosphere and corona of the Sun has led to
methods of extending photospheric magnetic measurements into the solar
atmosphere by mathematical procedures. A new approach to this problem
presented here is that a constant alpha force-free field can be uniquely
determined from the tangential components of the measured photospheric
flux alone. The vector magnetographs now provide measurements of
both the solar photospheric tangential and the longitudinal magnetic
field. This paper presents derivations for the computation of the
solar magnetic field from these type of measurements. The fields
considered are assumed to be a constant alpha force-free fields or
equivalent, producing vanishing Lorentz forces. Consequently, magnetic
field lines and currents are related by a constant and hence show an
identical distribution. The magnetic field above simple solar regions
are described from the solution of the field equations.

---------------------------------------------------------
Title: Characteristics of the MSFC PDS Microdensitometer
Authors: Fountain, W. F.; Gary, G. A.; Oda, H.
1984amd..conf...71F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Characteristics of the MSFC, PDS microdensitometer.
Authors: Fountain, W. F.; Gary, G. A.; Oda, H.
1984NASCP2317...71F Altcode:
This report summarizes the results of several parametric studies carried
out on the Marshall Space Flight Center (MSFC) PDS-10 microdensitometer
for the purposes of documenting and understanding the operation and
limitations of the system for inhouse research and to provide a bench
mark for comparison with other microdensitometers.

---------------------------------------------------------
Title: An H alpha velocity study of S 252.
Authors: Fountain, W. F.; Gary, G. A.; Odell, C. R.
1983ApJ...273..639F Altcode:
The H II region S252 (NGC 2175) was studied by means of H-alpha
radial velocities and line widths. The velocity structure appears
to be dominated by the western ionization front, abutting a dense
neutral cloud which is a CO source, and by symmetry abut the ionizing
star. This data, together with other studies of CO, H167-alpha, and
the H II radio continuum, allow construction of a model of S252. The
H II model is basically a double blister formed by a luminous hot star
being located between two orthogonal, elongated neutral clouds.

---------------------------------------------------------
Title: A study of Hα velocities in NGC 1499, NGC 7000, and IC
1318B/C.
Authors: Fountain, W. F.; Gary, G. A.; Odell, C. R.
1983ApJ...269..164F Altcode:
Multiple slit echelle spectrograph observations of the H-alpha emission
line are used to map the radial velocities of the California Nebula (NGC
1499), the North American Nebula complex (NGC 7000 and IC 5070), and
IC 1318B/C. The California Nebula is singularly constant in velocity,
considering its geometry. The North American Nebula complex reflects
a very simple, classical dynamical picture. The expansion discovered
earlier in IC 1318B/C is confirmed, detailed, and the model refined. The
new data, along with that in earlier papers of this series, show that
stellar wind acceleration and champagne flow mechanisms both play
important roles in determining the evolution of H II regions.

---------------------------------------------------------
Title: An investigation of the neutral and ionized gas in M16
Authors: Mufson, S. L.; Fountain, W. F.; Gary, G. A.; Howard, W. E.,
III; O'Dell, C. R.; Wolff, M. T.
1981ApJ...248..992M Altcode:
An attempt is made to understand the physical and kinematic conditions
in the M16 active star formation site, by means of mapping observations
of neutral and ionized hydrogen and observations of (C-12)O from
selected positions within the H II regions. The 21-cm maps suggest
that at least two neutral clouds are present in the M16 complex, one of
which is likely to be the remains of the cloud in which star formation
initially occurred, and the other is probably the cold gas remaining
from a disrupted cloud edge where the ionization front has crossed the
cloud-intercloud boundary. Multislit echelle spectra of the H-alpha line
are obtained to determine the physical conditions within the ionized
gas, and H-alpha maps show that the ionized gas is systematically
blueshifted in the east and splits into two streams in the southwest.

---------------------------------------------------------
Title: Erratum - an Internal Velocity Study of the Rosette Nebula
Authors: Fountain, W. F.; Gary, G. A.; O'dell, C. R.
1980ApJ...236.1056F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: An internal velocity study of the Rosette Nebula.
Authors: Fountain, W. F.; Gary, G. A.; Odell, C. R.
1979ApJ...229..971F Altcode:
Emission-line profiles of H-alpha were studied at about 700 points in
the Rosette Nebula by using a multislit echelle spectrograph. Numerical
analysis of the profiles indicates that variations in the line-of-sight
velocity occur within the nebula, reaching about + or - 20 km/s in the
inner regions. Evidence is presented that these highest velocities
are more probably inward, favoring a model where the central cavity
is due to a depletion resulting from rapid star formation

---------------------------------------------------------
Title: An Echelle Spectrograph Study of the Rosette Nebula
Authors: Fountain, W. F.; Gary, G. A.; O'dell, C. R.
1978BAAS...10R.397F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Spectrographic observations of Comet West (1975n).
Authors: Gary, G. A.; Fountain, W. F.; Odell, C. R.
1977PASP...89...97G Altcode:
The spectrum of comet West (1975 n) was recorded on March 7 and 11,
1976, in the wavelength interval from 5700 to 8200 A at an intermediate
resolution. One hundred twenty-two emission lines are reported, with
78 lines having identifications with spectral features of NH2, H2O(+),
C2, O I forbidden emission, and Na I.

---------------------------------------------------------
Title: The contribution of interstellar particles to the
interplanetary dust complex
Authors: Gary, G. A.
1977STIN...7724038G Altcode:
The Poynting-Robertson effect acting on interstellar particles passing
by the sun was shown to have the potential to capture and possibly
to contribute some of these particles to the interplanetary dust
complex. When the probability of encounter of the sun with interstellar
clouds is considered, the quasi-equilibrium mass rate of accretion by
this mechanism is comparable to the mass loss rate of the interplanetary
complex. The mechanism then produces a quasi-equilibrium condition to
maintain the interplanetary particle complex. This requires that the
interstellar particles have a repulsive force due to radiation pressure
less than the attractive gravitational force. If this assumption
is correct for a significant fraction of the particles, then at
intervals an interstellar cloud may pass sufficiently close to the sun
to allow the Poynting-Robertson effect to replenish the interplanetary
complex. The previously proposed mechanisms of gravitational encounters
and the solar gravitational lens as a method of capture of interstellar
particles are shown to be insufficient. Corrections to the formulations
of these two methods are given, and a closed form formula of the
Poynting-Robertson effect on hyperbolic orbits about a star is derived.

---------------------------------------------------------
Title: Interpretation of the anti-tail of comet Kohoutek as a particle
flow phenomenon.
Authors: Gary, G. A.; O'Dell, C. R.
1975NASSP.355...27G Altcode: 1975coko.conf...27G
No abstract at ADS

---------------------------------------------------------
Title: Interpretation of the anti-tail of comet Kohoutek as a particle
flow phenomenon
Authors: Gary, G. A.; Odell, C. R.
1974Icar...23..519G Altcode:
The appearance of a "sunward" spike, opposite in apparent orientation
to the normal Type-II tail in Comet Kohoutek is interpreted as evidence
for large particles ejected near perihelion. It is shown that the shape
and orientation can be satisfactorily explained in this manner, after
consideration of the increased mass flow at decreasing heliocentric
distance. The apparent length of the spike can be a measure of the
particle size ( d) and density ( ϱd) and a value of
ϱd≅0.004 g/cm 2 fits the Skylab observations.

---------------------------------------------------------
Title: SKYLAB observations of Comet Kohoutek
Authors: Snoddy, W. C.; Gary, G. A.
1974aiaa.conf.....S Altcode:
This paper summarizes the special operational procedures developed
to observe the Comet Kohoutek from Skylab and the scientific
results from these observations. Emphasis is placed on results
from Skylab experiments S052, White Light Coronagraph; S201, Far UV
Electronographic Camera; S233, Kohoutek Photometric Photography; S019,
UV Stellar Astronomy; S183, Ultraviolet Panorama Telescope; and S082B,
Ultraviolet Spectrography. Visual observations by the astronaut crew
and the significance of these observations are discussed.

---------------------------------------------------------
Title: Interpretation of the Anti-Tail of Comet Kohoutek as a Particle
Flow Phenomenon.
Authors: Gary, G. A.; O'dell, C. R.
1974BAAS....6..463G Altcode:
No abstract at ADS