Author name code: gary-allen ADS astronomy entries on 2022-09-14 author:"Gary, G. Allen" ------------------------------------------------------------------------ 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. Bibcode: 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. Title: Forecasting Solar Cycle 25 Using Deep Neural Networks Authors: Benson, B.; Pan, W. D.; Prasad, A.; Gary, G. A.; Hu, Q. Bibcode: 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. 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 Bibcode: 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. 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. Bibcode: 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. 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 Bibcode: 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. 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 Bibcode: 2014SoPh..289..867G Altcode: No abstract at ADS 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 Bibcode: 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. Title: Coronal Loop Mapping to Infer the Best Magnetic Field Models for Active Region Prominences Authors: Gary, G. Allen; Hu, Qiang; Lee, Jong Kwan Bibcode: 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. 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. Bibcode: 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 &lt 20% of the background flux levels, with a time-averaged emergence rate of no more than <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. Title: Beckers Effect in a Fabry-Pérot Imaging Interferometer and Its Effects on Magnetic Field Measurements Authors: Robinson, Brian; Balasubramaniam, K.; Gary, G. Bibcode: 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. 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. Bibcode: 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. 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. Bibcode: 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. Title: Obituary: Einar A. Tandberg-Hanssen (1921-2011) Authors: Gary, G.; Emslie, A.; Hathaway, David; Moore, Ronald Bibcode: 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. Title: Observed Aspects of Reconnection in Solar Eruptions Authors: Moore, Ronald L.; Sterling, Alphonse C.; Gary, G. Allen; Cirtain, Jonathan W.; Falconer, David A. Bibcode: 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. 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. Bibcode: 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. Title: Optimal Pre-Initial Conditions for Data-Driven MHD Simulations of Solar Active Regions Authors: Hu, Q.; Wang, A.; Wu, S.; Gary, G. A. Bibcode: 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. Title: A Combined Approach for Coronal Magnetic Field Modeling Authors: Hu, Qiang; Wang, A.; Wu, S. T.; Gary, G. A. Bibcode: 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. 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. Bibcode: 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. 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. Bibcode: 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. 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. Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 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&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. Bibcode: 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>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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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&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 Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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 (>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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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 & 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. Bibcode: 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. Bibcode: 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, & 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 > 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&T Program and its Solar and Heliospheric Physics SR&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. Bibcode: 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 (>150 Guass (G)) and strongly sheared (shear angle >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 (>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 >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. Bibcode: 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 & 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. Bibcode: 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 > 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. Bibcode: 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, & 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. Bibcode: 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&T. Title: Multiple Etalon Systems for the Advanced Technology Solar Telescope Authors: Gary, G. A.; Balasubramaniam, K. S.; Sigwarth, Michael Bibcode: 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 Bibcode: 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. Bibcode: 2002AAS...200.2005F Altcode: 2002BAAS...34..673F In a 17 vector magnetogram study of 12 bipolar active regions (Falconer, Moore, & 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 >= 99%. The sample size was too small to show a statistically significant correlation (confidence level >= 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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, & 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. Bibcode: 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 Bibcode: 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>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. Bibcode: 2001AGUSM..SP51A01G Altcode: When plasma β >1 then the gas pressure dominates over the magnetic pressure. This ratio as a function along the coronal magnetic field lines varies from β > 1 in the photosphere at the base of the field lines, to β << 1 in the mid-corona, to β > 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 << 1 , since the full boundary conditions do not exist in the β > 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 > 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 & 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. Bibcode: 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, & 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 (>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. Bibcode: 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. Bibcode: 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. Bibcode: 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 <<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 Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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 & et al. (1999), and Fletcher & 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 Bibcode: 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>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 <~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. Bibcode: 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. Bibcode: 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 > 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 > 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 & Kopp global MHD model. In the active region, beta becomes larger than unity at approximately 1.2Rs. In the Pneuman & 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 > 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 > 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 Bibcode: 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. Bibcode: 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. Bibcode: 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 > 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. Bibcode: 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. Bibcode: 1997SoPh..174....1W Altcode: Dedicated to Yoshinari Nakagawa. Title: Rendering Three-Dimensional Solar Coronal Structures Authors: Gary, G. Allen Bibcode: 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. Bibcode: 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 (>~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. Bibcode: 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 (>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 Bibcode: 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 Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1991BAAS...23.1031G Altcode: No abstract at ADS Title: Solar vector magnetic field measurements. Authors: Gary, G. A.; Hagyard, M. J.; West, E. A. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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: 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. Bibcode: 1989epos.conf....1P Altcode: Contents: 1. Introduction. 2. Magnetohydrodynamic instability. 3. Preflare magnetic and velocity fields. 4. Coronal manifestations of preflare activity. 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 1984amd..conf...71F Altcode: No abstract at ADS Title: Characteristics of the MSFC, PDS microdensitometer. Authors: Fountain, W. F.; Gary, G. A.; Oda, H. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1974BAAS....6..463G Altcode: No abstract at ADS