Author name code: rust ADS astronomy entries on 2022-09-14 author:"Rust, David Maurice" ------------------------------------------------------------------------ Title: The thermal architecture of the ESA ARIEL payload at the end of phase B1 Authors: Morgante, G.; Terenzi, L.; Desjonqueres, L.; Eccleston, P.; Bishop, G.; Caldwell, A.; Crook, M.; Drummond, R.; Hills, M.; Hunt, T.; Rust, D.; Puig, L.; Tirolien, T.; Focardi, M.; Zuppella, P.; Holmes, W.; Amiaux, J.; Czupalla, M.; Rataj, M.; Jessen, N. C.; Pedersen, S. M.; Pascale, E.; Pace, E.; Malaguti, G.; Micela, G. Bibcode: 2022ExA....53..905M Altcode: 2022ExA...tmp...37M The Atmospheric Remote-sensing Infrared Exoplanets Large-survey (ARIEL) is the fourth medium (M4) mission selected in the context of the ESA Cosmic Vision 2015-2025 programme, with a launch planned in 2028. During 4 years of flight operations, ARIEL will probe the chemical and physical properties of approximately 1000 known exoplanets by observing their atmosphere, to study how planetary systems form and evolve [1, 2]. The mission is designed as a transit and eclipse spectroscopy survey, operated by a 1-m class telescope feeding two instruments, the Fine Guidance system (FGS) and the ARIEL InfraRed Spectrometer (AIRS), that accommodate photometric and spectroscopic channels covering the band from 0.5 to 7.8 μm in the visible to near-IR range [3, 4]. The mission high sensitivity requirements ask for an extremely stable thermo-mechanical platform. The payload thermal control is based on a passive and active cooling approach. Passive cooling is achieved by a V-Groove shields system that exploits the L2 orbit favourable thermal conditions to cool the telescope and the optical bench to stable temperatures <60 K. The FGS focal planes operate at the optical bench temperature while the AIRS channel detectors require a colder reference, lower than 42 K. This is provided by an active cooling system based on a Neon Joule-Thomson cold end, fed by a mechanical compressor. In this paper we report the thermal architecture of the payload at the end of Phase B1 and present the requirements that drive the design together with the analyses results and the expected performances. Title: Solar Orbiter - Solar Wind Analyser Suite: Design and performance of the Electron Analyser System for the measurement of Solar Wind Electrons Authors: Kataria, D. O.; Lewis, G.; Owen, C. J.; Berthomier, M.; Leblanc, F.; Al-Janabi, K.; Anekallu, C.; Hancock, B.; Malpuss, A.; Mayall, A.; Nicolaou, G.; Rust, D.; Watson, G.; Wicks, R. T. Bibcode: 2020AGUFMSH0360015K Altcode: Solar Orbiter, launched in February 2020, will sample the near-Sun (< 0.3 AU) and high helio-latitude (> 30 degrees) environments using a state of the art complement of both in situ and remote sensing instruments. In this contribution, we discuss details of the Electron Analyser System (EAS), one of 3 sensor units which make up the Solar Wind Analyser (SWA) in-situ suite of instruments. EAS consists of two top-hat electrostatic analyser heads, each with a field of view (FOV) of 90° x 360°, mounted orthogonal to each other to provide full sky coverage. The analysers are enhanced performance top-hats with a deflection system enabling electrostatic steering of the incoming particles to cover a ±45° FOV and a variable geometric factor system enabling electrostatic control of particle throughput by up to an order of magnitude. The sensor is additionally mounted at the end of a 4-metre boom, minimising FOV blockage by the spacecraft and its appendages as well as the impact of photo- and secondary-electrons on the low-energy solar wind plasma. Details of the design will be presented along with charged particle optics and ground calibration results and preliminary in-flight performance will be discussed. The instrument has several features for flexible sampling of solar wind electron plasma as well as for monitoring the health of the sensor throughout the life of the mission. These will also be discussed. Title: The Solar Orbiter Solar Wind Analyser (SWA) suite Authors: Owen, C. J.; Bruno, R.; Livi, S.; Louarn, P.; Al Janabi, K.; Allegrini, F.; Amoros, C.; Baruah, R.; Barthe, A.; Berthomier, M.; Bordon, S.; Brockley-Blatt, C.; Brysbaert, C.; Capuano, G.; Collier, M.; DeMarco, R.; Fedorov, A.; Ford, J.; Fortunato, V.; Fratter, I.; Galvin, A. B.; Hancock, B.; Heirtzler, D.; Kataria, D.; Kistler, L.; Lepri, S. T.; Lewis, G.; Loeffler, C.; Marty, W.; Mathon, R.; Mayall, A.; Mele, G.; Ogasawara, K.; Orlandi, M.; Pacros, A.; Penou, E.; Persyn, S.; Petiot, M.; Phillips, M.; Přech, L.; Raines, J. M.; Reden, M.; Rouillard, A. P.; Rousseau, A.; Rubiella, J.; Seran, H.; Spencer, A.; Thomas, J. W.; Trevino, J.; Verscharen, D.; Wurz, P.; Alapide, A.; Amoruso, L.; André, N.; Anekallu, C.; Arciuli, V.; Arnett, K. L.; Ascolese, R.; Bancroft, C.; Bland, P.; Brysch, M.; Calvanese, R.; Castronuovo, M.; Čermák, I.; Chornay, D.; Clemens, S.; Coker, J.; Collinson, G.; D'Amicis, R.; Dandouras, I.; Darnley, R.; Davies, D.; Davison, G.; De Los Santos, A.; Devoto, P.; Dirks, G.; Edlund, E.; Fazakerley, A.; Ferris, M.; Frost, C.; Fruit, G.; Garat, C.; Génot, V.; Gibson, W.; Gilbert, J. A.; de Giosa, V.; Gradone, S.; Hailey, M.; Horbury, T. S.; Hunt, T.; Jacquey, C.; Johnson, M.; Lavraud, B.; Lawrenson, A.; Leblanc, F.; Lockhart, W.; Maksimovic, M.; Malpus, A.; Marcucci, F.; Mazelle, C.; Monti, F.; Myers, S.; Nguyen, T.; Rodriguez-Pacheco, J.; Phillips, I.; Popecki, M.; Rees, K.; Rogacki, S. A.; Ruane, K.; Rust, D.; Salatti, M.; Sauvaud, J. A.; Stakhiv, M. O.; Stange, J.; Stubbs, T.; Taylor, T.; Techer, J. -D.; Terrier, G.; Thibodeaux, R.; Urdiales, C.; Varsani, A.; Walsh, A. P.; Watson, G.; Wheeler, P.; Willis, G.; Wimmer-Schweingruber, R. F.; Winter, B.; Yardley, J.; Zouganelis, I. Bibcode: 2020A&A...642A..16O Altcode: The Solar Orbiter mission seeks to make connections between the physical processes occurring at the Sun or in the solar corona and the nature of the solar wind created by those processes which is subsequently observed at the spacecraft. The mission also targets physical processes occurring in the solar wind itself during its journey from its source to the spacecraft. To meet the specific mission science goals, Solar Orbiter will be equipped with both remote-sensing and in-situ instruments which will make unprecedented measurements of the solar atmosphere and the inner heliosphere. A crucial set of measurements will be provided by the Solar Wind Analyser (SWA) suite of instruments. This suite consists of an Electron Analyser System (SWA-EAS), a Proton and Alpha particle Sensor (SWA-PAS), and a Heavy Ion Sensor (SWA-HIS) which are jointly served by a central control and data processing unit (SWA-DPU). Together these sensors will measure and categorise the vast majority of thermal and suprathermal ions and electrons in the solar wind and determine the abundances and charge states of the heavy ion populations. The three sensors in the SWA suite are each based on the top hat electrostatic analyser concept, which has been deployed on numerous space plasma missions. The SWA-EAS uses two such heads, each of which have 360° azimuth acceptance angles and ±45° aperture deflection plates. Together these two sensors, which are mounted on the end of the boom, will cover a full sky field-of-view (FoV) (except for blockages by the spacecraft and its appendages) and measure the full 3D velocity distribution function (VDF) of solar wind electrons in the energy range of a few eV to ∼5 keV. The SWA-PAS instrument also uses an electrostatic analyser with a more confined FoV (-24° to +42° × ±22.5° around the expected solar wind arrival direction), which nevertheless is capable of measuring the full 3D VDF of the protons and alpha particles arriving at the instrument in the energy range from 200 eV/q to 20 keV/e. Finally, SWA-HIS measures the composition and 3D VDFs of heavy ions in the bulk solar wind as well as those of the major constituents in the suprathermal energy range and those of pick-up ions. The sensor resolves the full 3D VDFs of the prominent heavy ions at a resolution of 5 min in normal mode and 30 s in burst mode. Additionally, SWA-HIS measures 3D VDFs of alpha particles at a 4 s resolution in burst mode. Measurements are over a FoV of -33° to +66° × ±20° around the expected solar wind arrival direction and at energies up to 80 keV/e. The mass resolution (m/Δm) is > 5. This paper describes how the three SWA scientific sensors, as delivered to the spacecraft, meet or exceed the performance requirements originally set out to achieve the mission's science goals. We describe the motivation and specific requirements for each of the three sensors within the SWA suite, their expected science results, their main characteristics, and their operation through the central SWA-DPU. We describe the combined data products that we expect to return from the suite and provide to the Solar Orbiter Archive for use in scientific analyses by members of the wider solar and heliospheric communities. These unique data products will help reveal the nature of the solar wind as a function of both heliocentric distance and solar latitude. Indeed, SWA-HIS measurements of solar wind composition will be the first such measurements made in the inner heliosphere. The SWA data are crucial to efforts to link the in situ measurements of the solar wind made at the spacecraft with remote observations of candidate source regions. This is a novel aspect of the mission which will lead to significant advances in our understanding of the mechanisms accelerating and heating the solar wind, driving eruptions and other transient phenomena on the Sun, and controlling the injection, acceleration, and transport of the energetic particles in the heliosphere. Title: d'Azambuja, Lucien Authors: Martres, M. J.; Rust, David M. Bibcode: 2014bea..book..528M Altcode: No abstract at ADS Title: Micro-Sigmoids as Progenitors of Polar Coronal Jets Authors: Raouafi, N. -E.; Bernasconi, P. N.; Rust, D. M.; Georgoulis, M. K. Bibcode: 2012ASPC..454..299R Altcode: Observations from the Hinode X-ray telescope (XRT) are used to study the structure of X-ray bright points (XBPs), sources of coronal jets. Several jet events are found to erupt from S-shaped bright points, suggesting that coronal micro-sigmoids are progenitors of the jets. The observations may help to explain numerous characteristics of coronal jets, such as helical structures and shapes. They also suggest that solar activity may be self-similar within a wide range of scales in terms of both properties and evolution of the observed coronal structures. Title: Micro-Sigmoids as Progenitors of Polar Coronal Jets Authors: Raouafi, N. -E.; Bernasconi, P. N.; Rust, D. M.; Georgoulis, M. K. Bibcode: 2010arXiv1009.2951R Altcode: Observations from the Hinode X-ray telescope (XRT) are used to study the structure of X-ray bright points (XBPs), sources of coronal jets. Several jet events are found to erupt from S-shaped bright points, suggesting that coronal micro-sigmoids are progenitors of the jets. The observations may help to explain numerous characteristics of coronal jets, such as helical structures and shapes. They also suggest that solar activity may be self-similar within a wide range of scales in terms of both properties and evolution of the observed coronal structures. Title: Micro-sigmoids as Progenitors of Coronal Jets: Is Eruptive Activity Self-similarly Multi-scaled? Authors: Raouafi, N. -E.; Georgoulis, M. K.; Rust, D. M.; Bernasconi, P. N. Bibcode: 2010ApJ...718..981R Altcode: 2010arXiv1005.4042R Observations from the X-ray telescope (XRT) on Hinode are used to study the nature of X-ray-bright points, sources of coronal jets. Several jet events in the coronal holes are found to erupt from small-scale, S-shaped bright regions. This finding suggests that coronal micro-sigmoids may well be progenitors of coronal jets. Moreover, the presence of these structures may explain numerous observed characteristics of jets such as helical structures, apparent transverse motions, and shapes. Analogous to large-scale sigmoids giving rise to coronal mass ejections (CMEs), a promising future task would perhaps be to investigate whether solar eruptive activity, from coronal jets to CMEs, is self-similar in terms of properties and instability mechanisms. Title: Solar Magnetic Helicity Injected into the Heliosphere: Magnitude, Balance, and Periodicities Over Solar Cycle 23 Authors: Georgoulis, M. K.; Rust, D. M.; Pevtsov, A. A.; Bernasconi, P. N.; Kuzanyan, K. M. Bibcode: 2009ApJ...705L..48G Altcode: Relying purely on solar photospheric magnetic field measurements that cover most of solar cycle 23 (1996-2005), we calculate the total relative magnetic helicity injected into the solar atmosphere, and eventually shed into the heliosphere, over the latest cycle. Large active regions dominate the helicity injection process with ~5.7 × 1045 Mx2 of total injected helicity. The net helicity injected is lsim1% of the above output. Peculiar active-region plasma flows account for ~80% of this helicity; the remaining ~20% is due to solar differential rotation. The typical helicity per active-region CME ranges between (1.8-7) × 1042 Mx2 depending on the CME velocity. Accounting for various minor underestimation factors, we estimate a maximum helicity injection of ~6.6 × 1045 Mx2 for solar cycle 23. Although no significant net helicity exists over both solar hemispheres, we recover the well-known hemispheric helicity preference, which is significantly enhanced by the solar differential rotation. We also find that helicity injection in the solar atmosphere is an inherently disorganized, impulsive, and aperiodic process. Title: Just how much Helicity did the Sun Shed in Solar Cycle 23? Magnitude, Balance, Periodicities, and Further Implications Authors: Georgoulis, Manolis K.; Rust, D. M.; Pevtsov, A. A.; Bernasconi, P. N.; Kuzanyan, K. M. Bibcode: 2009SPD....40.0606G Altcode: Using solar magnetic field measurements, we calculate the total relative magnetic helicity injected in the solar atmosphere and eventually

transported to the heliosphere in the course of the latest solar cycle. We report on (i) the magnitude of the heliospheric helicity over cycle 23, (ii) the net helicity and its significance, and (iii) the possible

periodicities of helicity injection in the solar atmosphere. Our simple calculations raise several questions regarding the fundamental nature of solar magnetism. The lack of significant net helicity may place the solar dynamo in the category of

astrophysical dynamos without a net helicity effect over an average time scale. The strong enhancement of the hemispheric helicity preference by solar differential rotation - although the latter has a much weaker effect than intrinsic active-region plasma flows - warrants further investigation. Finally, the absence of any credible periodicity of helicity injection, in spite of numerous reported periodicities in solar activity, perhaps prompts the re-evaluation of the notion that the Sun works through a sequence of internal cycles: active-region emergence and evolution appears as an inherently disorganized, aperiodic process. Title: On the Helical Fields Guiding Near-Relativistic Electron Beams in the Heliosphere Authors: Rust, David M.; Haggerty, D. K.; Georgoulis, M. K.; Stenborg, G. Bibcode: 2009SPD....40.3202R Altcode: Wavelet processing of the LASCO images of the solar corona brings out many subtle details that are easily missed in the intensity images. Specifically, wavelet processing can enhance the edges on large and small scales making it easier to detect and define helical features. We used the processed LASCO images obtained during the period 1997 -2001 to study the structure and motions of nearly radial streamers extending from coronal holes adjacent to flaring active regions. Some of the streamers show outward-propagating twist. These helical fields extend into the heliosphere where they would reach 1 AU with a path length generally greater than the 1.2 AU of idealized fields following the Parker spiral. We focused on the regions from our earlier work (Rust et al., ApJ 687, 635, 2008) on flares associated with beams of near-relativistic electrons detected at 1 AU with the ACE spacecraft. Our study shows that the electron beam's typical delay of about 10 min in arriving at 1 AU may be due to their following a helical path from Sun to Earth. According to the reconnection jet model, the helical component may be introduced to open fields by earlier events involving reconnections with emerging, twisted flux ropes. Our study implies that the escaping electrons may be accelerated at the same time as the trapped electrons that produce X-ray flare emissions.

NASA supported this work with grant NNG 05GM69G. Title: On the plumbing system of volcanic complexes: field constraints from the Isle of Skye (UK) and FEM elasto-plastic modelling including gravity and tectonics. Authors: Bistacchi, A.; Pisterna, R.; Romano, V.; Rust, D.; Tibaldi, A. Bibcode: 2009EGUGA..11.8581B Altcode: The plumbing system that connects a sub-volcanic magma reservoir to the surface has been the object of field characterization and mechanical modelling efforts since the pioneering work by Anderson (1936), who produced a detailed account of the spectacular Cullin Cone-sheet Complex (Isle of Skye, UK) and a geometrical and mechanical model aimed at defining the depth to the magma chamber. Since this work, the definition of the stress state in the half space comprised between the magma reservoir and the surface (modelled either as a flat surface or a surface comprising a volcanic edifice) was considered the key point in reconstructing dike propagation paths from the magma chamber. In fact, this process is generally seen as the propagation in an elastic media of purely tensional joints (mode I or opening mode propagation), which follow trajectories perpendicular to the least compressive principal stress axis. Later works generally used different continuum mechanics methodologies (analytic, BEM, FEM) to solve the problem of a pressure source (the magma chamber, either a point source or a finite volume) in an elastic (in some cases heterogeneous) half space (bounded by a flat topography or topped by a "volcano"). All these models (with a few limited exceptions) disregard the effect of the regional stress field, which is caused by tectonic boundary forces and gravitational body load, and consider only the pressure source represented by the magma chamber (review in Gudmundsson, 2006). However, this is only a (sometimes subordinate) component of the total stress field. Grosfils (2007) first introduced the gravitational load (but not tectonic stresses) in an elastic model solved with FEM in a 2D axisymmetric half-space, showing that "failure to incorporate gravitational loading correctly" affect the calculated stress pattern and many of the predictions that can be drawn from the models. In this contribution we report on modelling results that include: 2D axisymmetric or true 3D geometry; gravitational body load; anisotropic tectonic stresses; different shapes and depths of the magma chamber; different overpressure levels in the magma chamber; different shapes of the topographic surface (e.g. flat, volcano, caldera); linear-elastic or elasto-plastic Drucker-Prager rheology. The latter point, which in our opinion constitutes a fundamental improvement in the model, has proven necessary because in a purely elastic model the stress state would rise at levels that cannot be sustained by geologic materials. Particularly around and above the magma chamber, yielding is expected, influencing the stress field in the remaining modelling domain. The non-linear problem has been solved with the commercial finite element package Comsol Multiphysics, using a parametric solver. At the same time, a field structural analysis of the classical Cuillin Cone-sheet Complex has been performed. This analysis has shown that four distinct families of cone sheets of different age do exist. Among these, the sheets with the higher dip angle range (80-65°) are confirmed as purely tensional joints, but those with a lower dip angle range (60-40°) are quite often (when suitable markers are available) associated with a measurable shear component. Combining these new field observations with mechanical modelling results, we propose a new interpretation for the Cuillin Cone Sheet Complex. The plumbing system was composed by both purely tensional joints and mesoscopic faults with a shear component, produced in response to the regional stress field perturbed by the magma chamber, and later passively re-used as magma emplacement conduits. Under this assumption, the observed geometry of the Cuillin Cone-sheet Complex is consistent with a relatively shallow magma chamber with a flattened laccolite shape. The shape of the palaeotopography, now completely eroded, has also been considered, but is more weakly constrained by modelling results. References: Anderson E.M., 1936. The dynamics of the formation of cone-sheets, ring-dykes and cauldron subsidences. Proc R Soc Edinburgh, 56, 128-157. Grosfils E.B., 2007. Magma reservoir failure on the terrestrial planets: Assessing the importance of gravitational loading in simple elastic models. Journal of Volcanology and Geothermal Research, 166 (2), 47-75. Gudmundsson A. , 2006. How local stresses control magma-chamber ruptures, dyke injections, and eruptions in composite volcanoes. Earth Science Reviews, 79 (1), 1-31. Title: The Helical Fields of CMEs and the Paths of Near-Relativistic Electrons into the Heliosphere Authors: Rust, D. M.; Haggerty, D. K.; Stenborg, G. Bibcode: 2009EGUGA..11.6412R Altcode: Wavelet processing of the LASCO images of the solar corona brings out many subtle details that are easily missed in the intensity images. Specifically, wavelet processing can enhance the edges of large and small scale structures making it easier to detect and define motions. We used the processed LASCO images obtained during the period 1998 - 2001, of maximum activity of the last sunspot cycle, to study the structure and motions of the CME legs and the nearby fields. Many CMEs show large-scale latitudinal leg displacements that resemble screw threads leaving the Sun. The helical fields extend into the heliosphere after, and sometimes before, the associated CME has left the LASCO C2 field of view. We focused our attention on the CMEs that were analyzed by Simnett et al., Ap. J. 579, 854, 2002. They linked those CMEs to beams of near- relativistic electrons detected at 1 AU with the ACE spacecraft. Our study shows that the electron beams' typical delay of about 10 min in arriving at 1 AU may be due to their following a longer, helical path from Sun to Earth than the usually assumed Parker spiral length of 1.2 AU. The study implies that the escaping electrons may be accelerated at the same time as the trapped electrons that produce hard X-ray flare emissions. When that is the case, there is no need to invoke acceleration in the CME fronts. Title: On the Solar Origins of Open Magnetic Fields in the Heliosphere Authors: Rust, David M.; Haggerty, Dennis K.; Georgoulis, Manolis K.; Sheeley, Neil R.; Wang, Yi-Ming; DeRosa, Marc L.; Schrijver, Carolus J. Bibcode: 2008ApJ...687..635R Altcode: A combination of heliospheric and solar data was used to identify open magnetic fields stretching from the lower corona to Earth orbit. 35 near-relativistic electron beams detected at the ACE spacecraft "labeled" the heliospheric segments of the open fields. An X-ray flare occurred <20 minutes before injection of the electrons in 25 events. These flares labeled the solar segment of the open fields. The flares occurred in western-hemisphere active regions (ARs) with coronal holes whose polarity agreed with the polarity of the beam-carrying interplanetary fields in 23 of the 25 events. We conclude that electron beams reach 1 AU from open AR fields adjacent to flare sites. The Wang & Sheeley implementation of the potential-field source-surface model successfully identified the open fields in 36% of cases. Success meant that the open fields reached the source surface within 3 heliographic deg of the interplanetary magnetic field connected to ACE at 1 AU. Inclusion of five near misses improves the success rate to 56%. The success rate for the Schrijver & DeRosa PFSS implementation was 50%. Our results suggest that, even if the input magnetic data are updated frequently, the PFSS models succeed in only ~50% of cases to identify the coronal segment of open fields. Development of other techniques is in its infancy. Title: Probing Open Magnetic Fields at the Sun with near-relativistic electron beams Authors: Haggerty, D. K.; Rust, D. M.; Georgoulis, M. K. Bibcode: 2008AGUSMSH43B..06H Altcode: Processes associated with solar flares accelerate and inject near-relativistic electrons onto open coronal field lines. Some of these electron events propagate nearly scatter-free to 1 AU, where their spectra and angular distributions can be measured. We used a carefully selected list of electron events for which both the solar and near-Earth positions are well known. Soft X-ray images from Yohkoh determined the positions of coronal holes near active regions as well as the flares associated with the electron events. We chose relatively small events that exhibit nearly Gaussian shaped time-intensity profiles. These events should incur minimal coronal and heliospheric transport effects, which can affect the Sun-to-Earth path length. Twenty-five events met our criteria for inclusion in the study. We use three different methods to estimate the path-length of the electrons and two different potential-field source-surface calculations to trace the open fields from their intersection with the heliospheric field at 2.5 solar radii down to the base of the corona. We report on the successes and failures of these PFSS models to identify open fields in/near active regions and to indicate correctly which open coronal fields are connected to the interplanetary magnetic field at Earth. Title: Survey of Magnetic Helicity Injection in Regions Producing X-Class Flares Authors: LaBonte, B. J.; Georgoulis, M. K.; Rust, D. M. Bibcode: 2007ApJ...671..955L Altcode: Virtually all X-class flares produce a coronal mass ejection (CME), and each CME carries magnetic helicity into the heliosphere. Using magnetograms from the Michelson Doppler Imager on the Solar and Heliospheric Observatory, we surveyed magnetic helicity injection into 48 X-flare-producing active regions recorded by the MDI between 1996 July and 2005 July. Magnetic helicity flux was calculated according to the method of Chae for the 48 X-flaring regions and for 345 non-X-flaring regions. Our survey revealed that a necessary condition for the occurrence of an X-flare is that the peak helicity flux has a magnitude >6×1036 Mx2 s-1. X-flaring regions also consistently had a higher net helicity change during the ~6 day measurement intervals than nonflaring regions. We find that the weak hemispherical preference of helicity injection, positive in the south and negative in the north, is caused by the solar differential rotation, but it tends to be obscured by the intrinsic helicity injection, which is more disorganized and tends to be of opposite sign. An empirical fit to the data shows that the injected helicity over the range 1039-10 43 Mx2 s-1 is proportional to magnetic flux squared. Similarly, over a range of 0.3-3000 days, the time required to generate the helicity in a CME is inversely proportional to the magnetic flux squared. Most of the X-flare regions generated the helicity needed for a CME in a few days to a few hours. Title: Quantitative Forecasting of Major Solar Flares Authors: Georgoulis, Manolis K.; Rust, David M. Bibcode: 2007ApJ...661L.109G Altcode: We define the effective connected magnetic field, Beff, a single metric of the flaring potential in solar active regions. We calculated Beff for 298 active regions (93 X- and M-flaring, 205 nonflaring) as recorded by SOHO/MDI during a 10 yr period covering much of solar cycle 23. We find that Beff is a robust criterion for distinguishing flaring from nonflaring regions. A well-defined 12 hr conditional probability for major flares depends solely on Beff. This probability exceeds 0.95 for M-class and X-class flares if Beff>1600 G and Beff>2100 G, respectively, while the maximum calculated Beff-values are near 4000 G. Active regions do not give M-class and X-class flares if Beff<200 G and Beff<750 G, respectively. We conclude that Beff is an efficient flare-forecasting criterion that can be computed on a timely basis from readily available data. Title: Assessment Of The Eruptive Potential In Solar Active Regions Authors: Georgoulis, Manolis K.; Rust, D. M. Bibcode: 2007AAS...210.9325G Altcode: 2007BAAS...39Q.215G Solar active regions involving massive amounts of magnetic flux and conspicuous polarity inversion lines have always been considered likely sources of major flares and fast active-region CMEs. We quantify the magnetic complexity in the photospheric boundary of active regions and thereafter infer a well-defined 12-24-hour likelihood of major eruptions. Vector magnetograms are not required for our analysis, which is validated by application to about 300 active regions observed by SoHO/MDI over a period of a few to several days each. The proposed single metric favors a well-defined physical mechanism for major flares and CMEs and may lead to a detailed, quantitative, understanding of the flare/CME phenomenon. This work has received partial support by NASA Grant NNG05-GM47G. Title: The Fundamental Role Of Magnetic Helicity In Major Solar Eruptions Authors: Rust, David M.; Georgoulis, M. K. Bibcode: 2007AAS...210.2913R Altcode: 2007BAAS...39R.139R What is the role magnetic helicity plays in solar eruptions? To find out, we calculate the magnetic helicity flux for 48 X-class flaring solar active regions and for 345 M-class flaring regions. Each region was observed over a period of a few, to several, days by SoHO/MDI. We find consistently higher helicity buildup rates for the X-flaring regions. X-class flares do not occur if the peak helicity flux is smaller than 6 x 1036 Mx2/s, with most nonflaring regions showing much smaller peaks. The weak hemispheric preference of magnetic

helicity is caused by the solar differential rotation, but it is blurred by the intrinsic helicity injection which is more disorganized and of opposite sign. Notably, X-flaring regions can generate the helicity for a typical CME within a few hours to a few days, contrary to most flare-quiescent regions that require from several tens to hundreds of days. We conclude that accumulation of magnetic helicity is a precondition for major flare/CME events. This work has received partial support by NASA Grants NAG5-13504 and NNG05-GM47G. Title: Obituary: Barry James LaBonte, 1950-2005 Authors: Rust, David Maurice Bibcode: 2006BAAS...38.1277R Altcode: Dr. Barry J. LaBonte, age 55, a senior solar physicist in the Space Department of the Johns Hopkins University Applied Physics Laboratory, died on 24 October 2005 in Philadelphia of complications following surgery. He was an internationally recognized expert on solar magnetic fields, the solar cycle, and on the sophisticated instruments needed for studying them.

Barry LaBonte was born in Providence, Rhode Island on 28 April 1950. His parents were Arlene and William LaBonte, and Barry was the oldest of their three children. He excelled early in mathematics and was admitted to the California Institute of Technology, where he earned a BS in economics and a PhD in astronomy. From 1978 to 1981, he did his postdoctoral work at the Mount Wilson Observatory where he and Dr. Robert Howard discovered and analyzed the solar torsional oscillations, which are global flow patterns somewhat analogous to the jet streams of terrestrial weather. They described their findings in a series of thirteen papers in three years. LaBonte and Howard also showed that magnetic fields on the sun are much more dynamic than were previously thought. Contrary to the impression that a few, long-lived sunspots give, the total replacement of the surface magnetic flux occurs within only ten days.

In 1981 Barry became an astronomer at the Institute for Astronomy of the University of Hawaii, where he taught undergraduate and advanced graduate courses and became head of the Mees Solar Observatory. In addition to further work on solar magnetism, he initiated a research program in solar acoustic oscillations, which led to the discovery that sunspots absorb acoustic waves of the global oscillations of the sun. Doug Braun, Tom Duvall, and Barry LaBonte calculated that sunspot magnetic fields, contrary to earlier expectations, absorb enough p-mode energy to alter the spectrum of the global oscillations. It was later shown that sensitive analysis of the oscillations on the face of the sun could detect the presence of sunspots on the invisible side, before they rotate into view. The method, called helioseismic acoustic imaging, has led to much improved two-week predictions of solar activity on the earth-facing side of the sun. While at the University of Hawaii, he guided the work of graduate students and postdocs, and many of his students are among today's outstanding solar researchers.

Barry served the AAS Solar Physics Division variously as a member of the Steering Committee, Nominating Committee, and the Hale Prize Committee. He served the nation on the NSF-NASA-DOE Astronomy and Astrophysics Advisory Committee and the NASA Solar and Heliospheric Physics Management and Operations Working Group.

He worked hard to improve the visibility of heliospheric physics at NASA, where it encountered a very barren stretch in the late 1980s and early 1990s. With the initiation of the "Living With a Star" program in 2000, Barry moved to the East Coast where at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland, he could work more effectively on solar space missions.

Barry felt at home with all aspects of solar physics, and he found excitement in the fact that solar and heliospheric science had an impact on earth and man-made systems. At APL, he worked principally on the interpretation of solar magnetic activity. He also helped to develop the technology of the Solar Bolometric Imager, a unique telescope for precise measurements of the sources of the variations in the sun's radiative output. The torsional oscillations that LaBonte and Howard discovered may be one source of subtle and unexplained variations. Barry also was interested in the flow of magnetic helicity into the corona. He developed a program to automatically compute from near real-time data the amount of helicity entering the corona each day. He used the program to compile helicity data on hundreds of sunspot groups and concluded that there is a threshold accumulation of helicity needed for the occurrence of a large flare. His work always involved fundamental science that could possibly lead to accurate forecasts of solar activity and its effect on geospace. When he died, he was studying the three-dimensional structure of the magnetic fields and electric currents in the solar corona in order to understand the disequilibrium that produces solar eruptions.

I first met Barry when he was a summer intern working with George Simon at the Sacramento Peak Observatory in Sunspot, New Mexico in the early 1970s. Besides working on the solar granulation, Barry learned how to use the Doppler-Zeeman analyzer, the first of the many solar magnetographs that he used to such advantage in his productive career. We had common scientific interests, which led me to follow his career closely, although I was on the East Coast and he was in Hawaii. We had both done our thesis under Hal Zirin and our postdoc with Bob Howard and had haunted many of the same scientific meetings, so I felt I knew him well. At APL he brought a depth of understanding and quick intelligence to our little solar group that lighted up every day.

Barry was more than an imaginative, witty, and productive scientist whose contributions greatly advanced solar physics. He was also a devoted father, rarely taking off from work except to be with his children. Inspired by his daughter Hillary's decision to train for an operatic career, he became an opera buff. He was an avid reader of history, especially military history, and was a member of the Hawaii Bunny Club and the Howard County Hare Raisers. He is survived by his wife, Beatrice Hawkins, and by their three children, Allan, Hillary, and Anna. Title: Mapping Solar Open Magnetic Fields With Near-Relativistic Electron Beams Authors: Rust, D. M.; Haggerty, D. K. Bibcode: 2006AGUFMSH11A0367R Altcode: We used a combination of heliospheric and solar data to identify a set of open fields for which both the solar and near-Earth positions are known. The purpose is to test existing and developing models of magnetic field topology. The models are provided by other members of the Living With a Star Targeted Research & Technology Heliospheric Magnetic Field Focus Team. For our part, we concentrated on the solar phenomena associated with near-relativistic electron energization and transport, because near-relativistic electrons emit or excite many forms of detectable electromagnetic (EM) radiation. The EM radiations help us identify the solar end or `origin' of individual open field lines, and the near-Earth ends can be identified by their association with electron beam events at 1 AU, using the EPAM instrument on the ACE spacecraft. The total number of events that met our criteria for inclusion in the study is about 200. For each event, we used the measured solar wind speed to estimate the curvature of the field line, from which we could infer the Carrington longitude of the open field on the `source surface' at 2.5 solar radii. Potential field source surface calculations supplied by I.-M. Wang and N. R. Sheeley allowed us to trace the open fields from their intersection with the heliospheric field at 2.5 solar radii down to the base of the corona. Our study was specifically designed to test two contrasting open field models: (1) a model with widely distributed open fields and (2) a model with open fields only in well- defined coronal holes. We will present the preliminary results of the study and several case studies. This work was supported by NASA TR&T grant NNG05GM69G. Title: Narrow-band Filter Observations of the Red-Line Corona at the 29 March 2006 Eclipse Authors: Rust, David M.; Noble, M. W.; Pasachoff, J. M.; Babcock, B. A.; Bruck, M. A.; Wittenmyer, R. A. Bibcode: 2006SPD....37.0110R Altcode: 2006BAAS...38..217R We report on observations of the corona above active region NOAA 10866, which was on the solar east limb at S 06 on 29 March 2006. Filtergrams were obtained at six 0.22 Å steps across the profile of the Fe X line at 6374.5 Å during the total solar eclipse, starting at about 1052 UT. The telescope was a 35-cm Schmidt-Cassegrain Meade RCX400 with the solar image relayed to a 512 x 512-pixel Andor Ixon DV887 CCD camera via telecentric optics and two narrow-bandpass filters: (1) a 2 Å thin-film Andover Corp. blocker and (2) a 0.16 Å tunable Fabry-Perot etalon, made by the CSIRO Australian Centre for Precision Optics. The F-P etalon is a Y-cut lithium niobate wafer of 0.200-mm thickness coated with reflective and conductive thin-film layers. Application of a voltage to the etalon produces a passband shift of 0.0011 Å/volt. Calibration at the eclipse site in Kastellorizo, Greece, was maintained by reference to a WSTech thermo-electrically stabilized diode laser tuned to 6375.16 Å. The profile and Doppler shifts of the Fe X line will be discussed.The expedition was supported by NSF (ATM-0552116), the Committee for Research and Exploration of the National Geographic Society, NASA's Planetary Astronomy Division for the CCD cameras (NNG04GE48G), Sigma Xi, and the Rob Spring Fund and the Ryan Patrick Gaishin Fund at Williams College. Title: Probing Solar Open Magnetic Fields With Near-relativistic Electron Beams. Authors: Haggerty, Dennis K.; Rust, D.; Sheeley, N. R.; Wang, Y. Bibcode: 2006SPD....37.1102H Altcode: 2006BAAS...38R.238H To achieve better understanding of our Sun-Earth environment, NASA's Living with a Star (LWS) program addresses question that cut across discipline boundaries. We present preliminary results on probing solar open magnetic fields with near-relativistic electron beams. This effort is directed at the major question: What determines the topology and evolution of the magnetic fields that stretch from the surface of the Sun to the outer boundary of the heliosphere? During nine years of operation, nearly an entire solar cycle, the ACE/EPAM instrument has measured well over 600 near-relativistic electron events. Approximately 30% of these electron events are impulsive with beam-like anisotropies and are predominantly from flares on the western hemisphere. Near-relativistic electrons are accelerated in the low corona and are released onto open coronal field lines, where they propagate nearly scatter-free out to 1 AU. Near-relativistic electrons are ideal probes of coronal open field lines because the transit time to 1 AU is 10 minutes as compared to lower energy ions that spend more time in the interplanetary medium and are therefore much more subject to transport processes. In this work we use observations of electrons from 1 AU, observations of various electromagnetic emissions associated with electron acceleration at the Sun, and observations and models of open magnetic field lines at the Sun to pinpoint the location of electron acceleration. Title: Coronal Observations at the 29 March 2006 Total Solar Eclipse Authors: Pasachoff, J. M.; Babcock, B. A.; Souza, S. P.; Bruck, M. A.; Hess, P. W.; Kimmel, S. B.; Levitt, J. S.; Steele, A. S.; Tsykalova, A. E.; Rust, D. M.; Noble, M. W.; Wittenmyer, R.; Kern, J.; Hawkins, R. L.; Seiradakis, J. H.; Voulgaris, A.; Pistikoudis, G.; Nestoras, J.; Demianski, M. Bibcode: 2006SPD....37.0107P Altcode: 2006BAAS...38Q.216P We report on our eclipse expedition to Kastellorizo, Greece, in the Dodecanese off the Turkish coast. We observed 3 min 00 sec of totality on 29 March 2006. All our observations worked very well. One of them was high-time-resolution (10 Hz) observations in the coronal green line looking at coronal loops; another was similar observations in the coronal red line; both are to determine among theories of coronal heating and continue earlier reports of excess Fourier power in the 1 Hz range. As we knew from SOHO observations from the day before the eclipse, an active region was stationed right on the east limb and it gave us very suitable loops to study, with pointing in agreement with TRACE. A third set of observations used a very narrow-band filter (Fabry-Perot), with 1/6 angstrom resolution, to make velocity (Doppler) images of the same coronal loops. A fourth set of observations used a telescope we had built to match the size of the now defunct innermost coronagraph on the NASA/ESA SOHO, and it indeed was used to merge with SOHO EIT disk coronal images and SOHO LASCO outer coronal coronagraph images. Further, radial-filter "Newkirk camera" images captured the role of magnetic fields in shaping coronal streamers, which we also display in mergers of images with sequential exposure times.

The expedition was supported by NSF (ATM-0552116), the Committee for Research and Exploration of the National Geographic Society, NASA's Planetary Astronomy Division for the CCD cameras (NNG04GE48G), Sigma Xi, and the Rob Spring Fund and the Ryan Patrick Gaishin Fund at Williams College. Title: Emergence of undulatory magnetic flux tubes by small scale reconnections Authors: Pariat, E.; Aulanier, G.; Schmieder, B.; Georgoulis, M. K.; Rust, D. M.; Bernasconi, P. N. Bibcode: 2006AdSpR..38..902P Altcode: With Flare Genesis Experiment (FGE), a balloon borne observatory launched in Antarctica on January 2000, series of high spatial resolution vector magnetograms, Dopplergrams, and Hα filtergrams have been obtained in an emerging active region (AR 8844). Previous analyses of this data revealed the occurence of many short-lived and small-scale H α brightenings called 'Ellerman bombs' (EBs) within the AR. We performed an extrapolation of the field above the photosphere using the linear force-free field approximation. The analysis of the magnetic topology reveals a close connexion between the loci of EBs and the existence of "Bald patches" (BP) regions (BPs are regions where the vector magnetic field is tangential to the photosphere). Some of these EBs/BPs are magnetically connected by low-lying field lines, presenting a serpentine shape. This results leads us to conjecture that arch filament systems and active regions coronal loops do not result from the smooth emergence of large scale Ω-loops, but rather from the rise of flat undulatory flux tubes which get released from their photospheric anchorage by reconnection at BPs, which observational signature is Ellerman bombs. Title: Observation of Small Scale Reconnection Role in Undulated Flux Tube Emergence Authors: Pariat, E.; Aulanier, G.; Schmieder, B.; Georgoulis, M. K.; Rust, D. M.; Bernasconi, P. N. Bibcode: 2005ESASP.596E..34P Altcode: 2005ccmf.confE..34P No abstract at ADS Title: The Sun and the Heliosphere as an Integrated System Authors: Rust, David M. Bibcode: 2005EOSTr..86..386R Altcode: The heliosphere is a bay in the interstellar space around the Sun where the solar wind blows lustily and holds back the magnetic fields and plasma of the local interstellar cloud. According to recent measurements from the Voyager 1 spacecraft, the radius of this bay, which is where the solar wind ceases to be supersonic, is about 94 astronomical units (AU) (1 AU = distance from the Sun to Earth). Much of what happens at the outer edges of the heliosphere is determined by what happens on the Sun. Magnetic fields generated in the solar interior boil to the surface and emerge into the outer atmosphere, called the corona, where they destabilize and propel coronal mass ejections (CMEs) into the heliosphere. The corona is also the source of the solar wind. Title: Advanced Automated Solar Filament Detection And Characterization Code: Description, Performance, And Results Authors: Bernasconi, Pietro N.; Rust, David M.; Hakim, Daniel Bibcode: 2005SoPh..228...97B Altcode: We present a code for automated detection, classification, and tracking of solar filaments in full-disk Hα images that can contribute to Living With a Star science investigations and space weather forecasting. The program can reliably identify filaments; determine their chirality and other relevant parameters like filament area, length, and average orientation with respect to the equator. It is also capable of tracking the day-by-day evolution of filaments while they travel across the visible disk. The code was tested by analyzing daily Hα images taken at the Big Bear Solar Observatory from mid-2000 until beginning of 2005. It identified and established the chirality of thousands of filaments without human intervention. We compared the results with a list of filament proprieties manually compiled by Pevtsov, Balasubramaniam and Rogers (2003) over the same period of time. The computer list matches Pevtsov's list with a 72% accuracy. The code results confirm the hemispheric chirality rule stating that dextral filaments predominate in the north and sinistral ones predominate in the south. The main difference between the two lists is that the code finds significantly more filaments without an identifiable chirality. This may be due to a tendency of human operators to be biased, thereby assigning a chirality in less clear cases, while the code is totally unbiased. We also have found evidence that filaments obeying the chirality rule tend to be larger and last longer than the ones that do not follow the hemispherical rule. Filaments adhering to the hemispheric rule also tend to be more tilted toward the equator between latitudes 10 and 30, than the ones that do not. Title: Observational Evidence of the Kink Instability In Solar Eruptions Authors: Rust, D. M. Bibcode: 2005AGUSMSH54B..02R Altcode: Two approaches to studying the role of source region magnetic fields for CMEs are described. First, observational evidence is used to infer that the MHD helical kink instability is associated with at least some filament eruptions and CMEs. In seven cases, the sense of twist and writhe in the source regions were determined from movies of erupting filaments. In every case the sense of twist was the same as the sense of writhe, as required for a kink. Next, we consider six different cases in which the chirality and axis orientation of interplanetary flux ropes could be compared with the corresponding signatures in the source regions at the Sun. In four cases, the chirality and orientation inferred from these pre-eruption flux rope signatures agreed well with the interplanetary flux rope signatures. In two cases, the flux rope axis orientations differed by about 150 degrees. These results suggest that the flux ropes existed prior to eruption, that they become flux ropes in interplanetary space, and, at least in some cases, that the kink instability is the likely cause of eruption. Title: Comparison of Interplanetary Disturbances at the NEAR Spacecraft with Coronal Mass Ejections at the Sun Authors: Rust, D. M.; Anderson, B. J.; Andrews, M. D.; Acuña, M. H.; Russell, C. T.; Schuck, P. W.; Mulligan, T. Bibcode: 2005ApJ...621..524R Altcode: We examined interplanetary (IP) magnetic field disturbances recorded by the Near Earth Asteroid Rendezvous-Shoemaker spacecraft (NEAR) when it was above either the east or west solar limb as seen from Earth; we then identified the associated coronal mass ejections (CMEs) detected above the limbs by the SOHO LASCO coronagraph. We found 10 cases in which a nonrecurring IP disturbance could be associated with a CME. Eight of the disturbances included a magnetic flux rope signature. Flux rope chirality and axis orientation were determined for each one and compared with chirality and axis orientation at the Sun, as inferred from flux rope signatures-filaments and sigmoids-that could be associated with the CMEs. In most cases, the chirality and orientation inferred from these preeruption flux rope signatures agreed well with the flux rope signatures at NEAR. These results suggest, in agreement with Plunkett and coworkers, that the flux ropes existed prior to eruption and that the flux ropes on the Sun become flux ropes in IP space. Comparisons of the CME speeds to the time-of-flight average speeds showed that flux ropes are less accelerated or decelerated by the solar wind than are the CME leading edges. These results imply that the faint features or loops that make up the CME leading edges are probably distinct from the flux ropes. Title: Observational Evidence of the Kink Instability in Solar Filament Eruptions and Sigmoids Authors: Rust, D. M.; LaBonte, B. J. Bibcode: 2005ApJ...622L..69R Altcode: Two lines of observational evidence are used to infer that the MHD helical kink instability is associated with solar eruptions. The senses of twist and writhe are determined in images of seven erupting filaments obtained at 10830, 1600, 195, and 171 Å. In every case the sense of twist is the same as the sense of writhe, as required for a kink. From images in the soft X-ray and EUV spectrum, measurements of the height/width ratio of 623 sigmoids show a mean value of 5.47, which is the ratio expected for kinked flux ropes. Title: Finding the sources of irradiance variation at sunspot minimum . Authors: Bernasconi, P. N.; Foukal, P.; Rust, D. M.; LaBonte, B. J. Bibcode: 2005MmSAI..76..907B Altcode: In 2006-2007 the Solar Bolometric Imager (SBI) will operate in the polar stratosphere where near-space conditions can be attained for 10 to 30 days. The instrument will provide bolometric (wavelength-integrated light) and color temperature images of the Sun. At the upcoming sunspot minimum, SBI observations will be able to detect subtle sources of solar irradiance variation with the least confusion by signals from the magnetic fields. This is the best observational approach to characterizing potential causes of the long-term irradiance variations. Possible predicted sources of secular variability include torsional waves and meridional flow variations. SBI uses a 30-cm diameter F/12 Dall-Kirkham telescope with uncoated mirrors, and neutral density filters to provide broadband (bolometric) sensitivity that varies only by ±7% over the wavelengths from 0.31 mu m to 2.6 mu m. Inferred solar irradiance variations will be compared with space based full-disk radiometric measurements. Title: Transport of Magnetic Helicity and Dynamics of Solar Active Regions Authors: Georgoulis, M. K.; Labonte, B. J.; Rust, D. M. Bibcode: 2005HiA....13..117G Altcode: We outline a simple method to monitor variations of the magnetic helicity the current helicity and the non-potential (free) magnetic energy on the photospheric boundary of solar active regions. Explicit manifestations of dynamical activity in the solar atmosphere such as flares coronal mass ejections and filament eruptions may be related to these variations. While similar methods require knowledge of the vector potential and the velocity field vector on the photosphere our method requires only the photospheric potential magnetic field corresponding to the observed magnetograms. The calculation of the potential field for any given magnetogram is straightforward. Moreover our method relies on the constant-alpha force-free approximation assumed to hold in the active region. Whether the above is a realistic assumption can be tested using an array of well-documented methods. Therefore our technique may prove quite useful to at least a subset of active regions in which the linear force-free approximation is justifiable. Title: Magnetic Helicity in Sigmoids, Coronal Mass Ejections and Magnetic Clouds Authors: Rust, D. M. Bibcode: 2005HiA....13..105R Altcode: Filaments coronal mass ejections (CMEs) and magnetic clouds (MCs) all show signatures of twisted and writhing magnetic fields. CMEs are often associated with MCs whose fields are regularly probed with sensitive magnetometers. These measurements reveal that MC fields are helical and each cloud carries magnetic helicity away from the sun. It is more difficult to determine the helicity of the corresponding features - filaments and coronal structures - on the sun. This talk will survey helicity estimates of solar features including their hemispherical distributions and evidence for writhe and twist in the fields. The distribution of magnetic helicity in the solar atmosphere may provide important clues to the workings of the solar dynamo. Title: Finding the Sources of Irradiance Variation at Sunspot Minimum Authors: Rust, D. M.; Bernasconi, P. N.; Foukal, P. V.; Labonte, B. J. Bibcode: 2004AGUFMSH51E..02R Altcode: In 2006-2007 the Solar Bolometric Imager (SBI) and the Multi-Spectral Imager (MSI) will operate in the polar stratosphere where near-space conditions can be attained for 10 to 20 days. The instruments will provide bolometric (wavelength-integrated light) and color temperature images of the Sun. At the upcoming sunspot minimum, SBI observations will be able to detect subtle sources of solar irradiance variation with the least confusion by signals from the magnetic fields. This is the best observational approach to characterizing potential causes of the long-term irradiance variations. Possible predicted sources of secular variability include torsional waves and meridional flow variations. SBI uses a 30-cm diameter F/12 Dall-Kirkham telescope with uncoated mirrors, and neutral density filters to provide broadband (bolometric) sensitivity that varies only by ±7 percent over the wavelengths from 0.28 microns to 2.6 microns. The MSI is a CCD-based imager that will provide diagnostics of solar magnetic and thermal structures while SBI assesses their radiance. Sunspots, faculae and magnetic network will be identified from the MSI images. Sonic filtering of the MSI images will isolate the oscillatory signal. That signal will be used to remove oscillations from SBI averages to reduce the solar noise. Inferred solar irradiance variations will be compared with SORCE/TIM and ACRIMSAT measurements. The images and data products will be openly available via the Web. Title: An Integrated Program to Forecast Geostorms Authors: Labonte, B. J.; Rust, D.; Bernasconi, P.; Georgoulis, M. Bibcode: 2004AGUFMSA51B0243L Altcode: We have developed several operational products and automated tools for assessing the helicity content of solar regions and their probability of launching a geoeffective coronal mass ejection. These include detection of active region sigmoids, measurement of magnetic helicity injection in active regions, measurement of the sense of helicity in solar filaments, and the estimate of magnetic helicity content of active regions from vector magnetogram observations. In this presentation we discuss a new program to integrate the separate products and tools into a single product that provides a quantitative mid-term forecast of solar activity that results in geomagnetic storms. Title: Advanced Automated Solar Filament Detection and Characterization Code: Description, Performance, and Results Authors: Bernasconi, P. N.; Rust, D. M. Bibcode: 2004AGUFMSA51B0235B Altcode: We have developed a code for automated detection and classification of solar filaments in full-disk H-alpha images that can contribute to Living With a Star science investigations and space weather forecasting. The program can reliably identify filaments, determine their chirality and other relevant parameters like the filaments area and their average orientation with respect to the equator, and is capable of tracking the day-by-day evolution of filaments while they travel across the visible disk. Detecting the filaments when they appear and tracking their evolution can provide not only early warnings of potentially hazardous conditions but also improve our understanding of solar filaments and their implications for space weather at 1 AU. The code was recently tested by analyzing daily H-alpha images taken at the Big Bear Solar Observatory during a period of four years (from mid 2000 until mid 2004). It identified and established the chirality of more than 5000 filaments without human intervention. We compared the results with the filament list manually compiled by Pevtsov et al. (2003) over the same period of time. The computer list matches the Pevtsov et al. list fairly well. The code results confirm the hemispherical chirality rule: dextral filaments predominate in the north and sinistral ones predominate in the south. The main difference between the two lists is that the code finds significantly more filaments without an identifiable chirality. This may be due to a tendency of human operators to be biased, thereby assigning a chirality in less clear cases, while the code is totally unbiased. We also have found evidence that filaments with definite chirality tend to be larger and last longer than the ones without a clear chirality signature. We will describe the major code characteristics and present and discuss the tests results. Title: Resistive Emergence of Undulatory Flux Tubes Authors: Pariat, E.; Aulanier, G.; Schmieder, B.; Georgoulis, M. K.; Rust, D. M.; Bernasconi, P. N. Bibcode: 2004ApJ...614.1099P Altcode: During its 2000 January flight, the Flare Genesis Experiment observed the gradual emergence of a bipolar active region, by recording a series of high-resolution photospheric vector magnetograms and images in the blue wing of the Hα line. Previous analyses of these data revealed the occurrence of many small-scale, transient Hα brightenings identified as Ellerman bombs (EBs). They occur during the flux emergence, and many of them are located near moving magnetic dipoles in which the vector magnetic field is nearly tangential to the photosphere. A linear force-free field extrapolation of one of the magnetograms was performed to study the magnetic topology of small-scale EBs and their possible role in the flux emergence process. We found that 23 out of 47 EBs are cospatial with bald patches (BPs), while 15 are located at the footpoints of very flat separatrix field lines passing through distant BPs. We conclude that EBs can be due to magnetic reconnection, not only at BP locations, but also along their separatrices, occurring in the low chromosphere. The topological analysis reveals, for the first time, that many EBs and BPs are linked by a hierarchy of elongated flux tubes showing aperiodic spatial undulations, whose wavelengths are typically above the threshold of the Parker instability. These findings suggest that arch filament systems and coronal loops do not result from the smooth emergence of large-scale Ω-loops from below the photosphere, but rather from the rise of undulatory flux tubes whose upper parts emerge because of the Parker instability and whose dipped lower parts emerge because of magnetic reconnection. EBs are then the signature of this resistive emergence of undulatory flux tubes. Title: Broadband Measurements of Facular Photometric Contrast Using the Solar Bolometric Imager Authors: Foukal, Peter; Bernasconi, Pietro; Eaton, Harry; Rust, David Bibcode: 2004ApJ...611L..57F Altcode: We present the first photometric measurements of solar faculae in broadband light. Our measurements were made during the recent flight of the Solar Bolometric Imager (SBI), a 30 cm balloon-borne telescope that imaged the Sun with a spectrally constant response between about 0.31 and 2.6 μm. Our curve of facular contrast versus limb distance agrees well with values obtained by the blackbody correction of monochromatic measurements. This decreases uncertainty in the facular irradiance contribution, which limits searches for other possible mechanisms of solar luminosity variation, besides changes of photospheric magnetism. Title: Emerging Flux and the Heating of Coronal Loops Authors: Schmieder, B.; Rust, D. M.; Georgoulis, M. K.; Démoulin, P.; Bernasconi, P. N. Bibcode: 2004ApJ...601..530S Altcode: We use data collected by a multiwavelength campaign of observations to describe how the fragmented, asymmetric emergence of magnetic flux in NOAA active region 8844 triggers the dynamics in the active-region atmosphere. Observations of various instruments on board Yohkoh, SOHO, and TRACE complement high-resolution observations of the balloon-borne Flare Genesis Experiment obtained on 2000 January 25. We find that coronal loops appeared and evolved rapidly ~6+/-2 hr after the first detection of emerging magnetic flux. In the low chromosphere, flux emergence resulted in intense Ellerman bomb activity. Besides the chromosphere, we find that Ellerman bombs may also heat the transition region, which showed ``moss'' ~100% brighter in areas with Ellerman bombs as compared to areas without Ellerman bombs. In the corona, we find a spatiotemporal anticorrelation between the soft X-ray (SXT) and the extreme ultraviolet (TRACE) loops. First, SXT loops preceded the appearance of the TRACE loops by 30-40 minutes. Second, the TRACE and SXT loops had different shapes and different footpoints. Third, the SXT loops were longer and higher than the TRACE loops. We conclude that the TRACE and the SXT loops were formed independently. TRACE loops were mainly heated at their footpoints, while SXT loops brightened in response to coronal magnetic reconnection. In summary, we observed a variety of coupled activity, from the photosphere to the active-region corona. Links between different aspects of this activity lead to a unified picture of the evolution and the energy release in the active region. Title: Emerging Flux and the Heating of Coronal Loops Authors: Schmieder, B.; Démoulin, P.; Rust, D. M.; Georgoulis, M. K.; Bernasconi, P. N. Bibcode: 2004IAUS..219..483S Altcode: 2003IAUS..219E..18S We suggest that coronal loop heating is caused by dissipation of magnetic energy as new magnetic flux emerges from the photosphere. Based on data from a multi wavelength campaign of observations during the flight of the Flare Genesis Experiment we describe how emergence of flux from the photosphere appears directly to heat the corona to 2-3 MK. Following intense heating the loops cool and become visible through the filters of the TRACE (Transition Region and Coronal Explorer)instrument at one million degrees. We determine the relaxation time of the cooling and compare it withtheoretical heating functions. The proposed mechanism is well accepted in flare loops but we suggest that the mechanism is generally valid and helps to explain the visibility of active region loops in transition region lines. Title: The solar bolometric imager Authors: Bernasconi, P. N.; Eaton, H. A. C.; Foukal, P.; Rust, D. M. Bibcode: 2004AdSpR..33.1746B Altcode: The balloon-borne Solar Bolometric Imager (SBI) will provide the first bolometric (integrated light) maps of the solar photosphere. It will evaluate the photometric contribution of magnetic structures more accurately than has been possible with spectrally selective imaging over restricted wavebands. More accurate removal of the magnetic feature contribution will enable us to determine if solar irradiance variation mechanisms exist other than the effects of photospheric magnetism. The SBI detector is an array of 320 × 240 ferro-electric thermal IR elements whose spectral absorptance has been extended and flattened by a deposited layer of gold-black. The telescope itself is a 30-cm Dall-Kirkham design with uncoated primary and secondary pyrex mirrors. The combination of telescope and bolometric array provides an image of the Sun with a flat spectral response between 0.28 and 2.6 μm, over a field of view of 917 × 687 arcsec, and a pixel size of 2.8 arcsec. After a successful set of ground-based tests, the instrument is being readied for a one-day stratospheric balloon flight that will take place in September 2003. The observing platform will be the gondola previously used for the Flare Genesis Experiment (FGE), retrofitted to house and control the SBI telescope and detector. The balloon flight will enable SBI to image over essentially the full spectral range accepted by non-imaging space-borne radiometers such as ACRIM, making the data sets complementary. The SBI flight will also provide important engineering data to validate the space worthiness of the novel gold-blackened thermal array detectors, and verify the thermal performance of the SBI's uncoated optics in a vacuum environment. Title: Emergence of undulatory magnetic flux tubes by small scale reconnections Authors: Pariat, E.; Aulanier, G.; Schmieder, B.; Georgoulis, M. K.; Rust, D. M.; Bernasconi, P. N. Bibcode: 2004cosp...35.1482P Altcode: 2004cosp.meet.1482P With Flare Genesis Experiment (FGE), a balloon borne observatory launched in Antarctica on January 2000, series of high spatial resolution vector magnetograms, Dopplergrams, and Hα filtergrams have been obtained in an emerging active region (AR 8844). Previous analyses of this data revealed the occurence of many short-lived and small-scale Hα brightenings called 'Ellerman bombs' (EBs) within the AR. We performed an extrapolation of the field above the photosphere using the linear force-free field approximation. The analysis of the magnetic topology reveals a close connexion between the loci of EBs and the existence of ``Bald patches'' regions (BPs are regions where the vector magnetic field is tangential to the photosphere). Among 47 identified EBs, we found that 23 are co-spatial with a BP, while 19 are located at the footpoint of very flat separatrix field lines passing throught a distant BP. We reveal for the first time that some of these EBs/BPs are magneticaly connected by low-lying lines, presenting a 'sea-serpent' shape. This results leads us to conjecture that arch filament systems and active regions coronal loops do not result from the smooth emergence of large scale Ω loops, but rather from the rise of flat undulatory flux tubes which get released from their photospheric anchorage by reconnection at BPs, whose observational signature is Ellerman bombs. Title: Lorentz Forces and Helicity Diagnostics in Solar Active Regions Based on a Fast Resolution of the Azimuthal Ambiguity in Solar Vector Magnetograms Authors: Georgoulis, Manolis K.; Labonte, Barry J.; Rust, David M. Bibcode: 2004hell.conf...82G Altcode: No abstract at ADS Title: First Results Of The Solar Bolometric Imager Authors: Bernasconi, P. N.; Foukal, P.; Eaton, H. H.; Rust, D. M. Bibcode: 2003AGUFMSH32A1101B Altcode: On September 1 2003, the Solar Bolometric Imager (SBI) successfully observed the Sun for several hours while suspended from a balloon in the stratosphere above New Mexico. The SBI represents a totally new approach in finding the sources of the solar irradiance variation. The mission provided the first bolometric (integrated light) maps of the solar photosphere, that will allow to evaluate the photometric contribution of magnetic structures more accurately than has been achievable with spectrally selective imaging over restricted wavebands. The more accurate removal of the magnetic features contribution will enable us to determine if solar irradiance variation mechanisms exist other than the effects of photospheric magnetism. The SBI detector was an array of 320 x 240 thermal IR elements whose spectral absorptance has been extended and flattened by a deposited layer of gold-black. The telescope was a 30-cm Dall-Kirkham with uncoated primary and secondary pyrex mirrors. The combination of telescope and bolometric array provided an image of the Sun with a flat spectral response between 0.28 and 2.6 microns, over a field of view of 917 x 687 arcsec with a pixel size of 2.8 arcsec. The observing platform was the gondola previously used for the Flare Genesis Experiment (FGE), retrofitted to house and control the SBI telescope and detector. During the 9 hours of flight the SBI gathered several thousand bolometric images that are now being processed to produce the first maps of the total solar irradiance. The SBI flight is also providing important engineering data to validate the space worthiness of the novel gold-blackened thermal array detectors, and to verify the thermal performance of the SBI's uncoated optics in a vacuum environment. In this paper we will briefly describe the characteristics of the SBI, its in flight performance, and we will present the first results of the analysis of the bolometric images. This work was funded by NASA under grant# NAG5-10998. Title: Measuring Magnetic Helicity Transport in Solar Active Regions: a Practical Implementation Authors: Rust, D. M.; Labonte, B. J. Bibcode: 2003AGUFMSH51A..02R Altcode: The causes of solar eruptions are not well understood, but it is clear that the emergence of magnetic flux and the accumulation of twisted (helical) magnetic fields in the solar atmosphere are preconditions for eruption. It has been very difficult to study these indicators because the magnetic data were unreliable due to varying `seeing' conditions. However, SOHO produces reliable magnetograms every 95 minutes. Chae (Astrophys. J. 560, L95, 2001) showed how SOHO (Solar and Heliospheric Observatory) data can yield reliable estimates of magnetic flux and magnetic helicity accumulation in the solar atmosphere. Chae's results suggest that regular time-series analyses of magnetograms could provide a useful early indicator of the build up of energy in the solar corona. Our objective has been to develop simple quantitative indicators of pre-eruption build-up and thereby warn of potential space weather related disturbances in space systems. We use the SOHO data, but in the near future the Solar B and SDO missions will provide much better magnetograms. So far, we have used Chae's method to map helicity transport in several regions with solar flares. We will show how advective helicity transport influences flare rate. We will also compare our results with analyses of vector magnetograms, which show both advective and convective helicity transport. Title: An Automated System for Detecting Sigmoids in Solar X-ray Images Authors: LaBonte, B. J.; Rust, D. M.; Bernasconi, P. N. Bibcode: 2003SPD....34.0504L Altcode: 2003BAAS...35R.814L The probability of a coronal mass ejection (CME) occurring is linked to the appearance of structures, called sigmoids, in satellite X-ray images of the sun. By examination of near real time images, we can detect sigmoids visually and estimate the probability of a CME and the probability that it will cause a major geomagnetic storm. We have devised a pattern recognition system to detect the sigmoids in Yohkoh SXT and GOES SXI X-ray images automatically. When implemented in a near real time environment, this system should allow long term, 3 - 7 day, forecasts of CMEs and their potential for causing major geomagnetic storms. Title: Evidence for Flux Ropes in the Solar Corona Authors: Rust, D. M. Bibcode: 2003SPD....34.0415R Altcode: 2003BAAS...35..813R Although twisted magnetic flux ropes are clearly ejected from the Sun, as demonstrated by LASCO and EIT movies of erupting prominences, there has been some controversy about whether flux ropes exist in the corona before ejection. It has been argued that they are formed only upon ejection. The issue is important because of the need to understand how eruptions are initiated. Now a clearer picture of solar flux ropes is emerging with recent high-resolution observations of solar filaments. Filament's twist and writhe are frequently detectable even when they do not escape the Sun. The observations of November 1, 2001 and May 27, 2002 made by the TRACE solar telescope both appear to show the sudden eruption without ejection of a filament, with transformation of some internal twist into a writhe of approx. + 1. Since magnetic helicity is approximately conserved, even in these rapid events, it follows that these kink events are strong evidence that flux ropes are present in the corona. We suggest that a flux rope may undergo several kink instabilities before it is ejected from the Sun. We identify coronal X-ray sigmoids as the aftermath of these sudden kink events. NASA supported this work under grant NAG5-11584. Title: The Solar Bolometric Imager: Characteristics and Performance. Authors: Bernasconi, P. N.; Foukal, P.; Rust, D. M. Bibcode: 2003SPD....34.2002B Altcode: 2003BAAS...35..844B The Solar Bolometric Imager (SBI) is an innovative solar telescope capable of recording the first bolometric (integrated light) maps of the photosphere. It will enable evaluation of the photometric contribution of magnetic structures more accurately than has been achievable with spectrally selective imaging. The SBI has an angular resolution of 5", sufficient to distinguish sunspots, faculae and enhanced network. These photospheric magnetic structures are known to be linked closely to irradiance variations. Accurate removal of irradiance variations linked to the magnetic features will enable us to determine if other solar irradiance variation mechanisms exist.

The SBI detector is an array of 320 x 240 ferro-electric thermal IR elements whose spectral absorptance has been extended and flattened by a deposited layer of gold-black. The telescope is a 30-cm Dall-Kirkham design with uncoated primary and secondary pyrex mirrors. The combination of telescope and bolometric array provides an image of the sun with a flat spectral response between 0.28 microns and 2.6 microns, over a field of view of 917" x 687", and a pixel size of 2.8". After completion of ground tests, the balloon-borne instrument will make a one-day stratospheric flight in September 2003.

Observing from an altitude of over 30 km, the SBI will image the sun over nearly the full spectral range accepted by non-imaging satellite-borne radiometers such as ACRIM, making the data sets complementary. The SBI flight will also provide important engineering data to validate the space worthiness of the novel gold-blackened thermal array detectors, and to verify the thermal performance of the SBI's optics in a vacuum environment.

Here we will describe the SBI in more detail and present the results of various instrument performance tests, including solar observations from the ground, in preparation for the balloon flight.

This work is funded by NASA under grant NAG5-10998. Title: Magnetic Helicity Pumping by Twisted Flux Tube Expansion Authors: Chae, Jongchul; Moon, Y. -J.; Rust, D. M.; Wang, Haimin; Goode, Philip R. Bibcode: 2003JKAS...36...33C Altcode: No abstract at ADS Title: Near-infrared chromospheric observatory Authors: Labonte, Barry; Rust, David M.; Bernasconi, Pietro N.; Georgoulis, Manolis K.; Fox, Nicola J.; Kalkofen, Wolfgang; Lin, Haosheng Bibcode: 2003SPIE.4853..140L Altcode: NICO, the Near Infrared Chromosphere Observatory, is a platform for determining the magnetic structure and fources of heating for the solar chromosphere. NICO, a balloon-borne observatory, will use the largest solar telescope flying to map the magnetic fields, velocities, and heating events of the chromosphere and photosphere in detail. NICO will introduce new technologies to solar flight missions, such as wavefront sensing for monitoring telescope alignment, real-time correlation tracking and high-speed image motion compensation, and wide aperture Fabry-Perot etalons for extended spectral scanning. Title: Magnetic Helicity in Filaments, CMES and Magnetic Clouds Authors: Rust, David Bibcode: 2003IAUJD...3E..23R Altcode: Filaments coronal mass ejections (CMEs) and magnetic clouds (MCs) all show signatures of twisted and writhing magnetic fields. CMEs are often associated with MCs whose fields are regularly probed with sensitive magnetometers. These measurements reveal that MC fields are helical and each cloud carries magnetic helicity away from the sun. It is more difficult to determine the helicity of the corresponding features - filaments and coronal structures - on the sun. This talk will survey helicity estimates of solar features including their hemispherical distributions and evidence for writhe and twist in the fields. The distribution of magnetic helicity in the solar atmosphere may provide important clues to the workings of the solar dynamo. Title: The helicial flux rope structure of solar filaments Authors: Rust, D. M. Bibcode: 2003AdSpR..32.1895R Altcode: According to J. B. Taylor's relaxation theory for magnetized plasmas, helical flux ropes should be the fundamental building blocks of magnetism in the solar atmosphere. Although flux ropes are clearly ejected from the Sun, there has been some controversy about whether they exist in the sun's atmosphere before ejection. The issue is important because of the need to understand how eruptions are initiated. A clearer picture of solar flux ropes is emerging with recent high-resolution observations of solar filaments. Their twist and writhe are frequently detectable. This report describes some examples of filaments that suddenly writhe (kink) and do not escape the sun. The observations of November 1, 2001 and May 27, 2002 both appear to show the sudden eruption of a filament with probable transformation of some internal twist into a writhe of approx. + 1. Also described is one event in which a well observed filament did erupt. It is associated with a magnetic flux rope detected with the NEAR spacecraft magnetometer. Title: Transport of Helicity and Dynamics of Solar Active Regions Authors: Georgoulis, Manolis K.; Rust, David M.; Labonte, Barry J. Bibcode: 2003IAUJD...3E..29G Altcode: We outline a simple method to monitor variations of the magnetic helicity the current helicity and the non-potential (free) magnetic energy on the photospheric boundary of solar active regions. Explicit manifestations of dynamical activity in the solar atmosphere such as flares coronal mass ejections and filament eruptions may be related to these variations. While similar methods require knowledge of the vector potential and the velocity field vector on the photosphere our method requires only the photospheric potential magnetic field corresponding to the observed magnetograms. The calculation of the potential field for any given magnetogram is straightforward. Moreover our method relies on the constant-alpha force-free approximation assumed to hold in the active region. Whether the above is a realistic assumption can be tested using an array of well-documented methods. Therefore our technique may prove quite useful to at least a subset of active regions in which the linear force-free approximation is justifiable. Title: Flare Genesis Experiment: magnetic topology of Ellerman bombs Authors: Schmieder, B.; Pariat, E.; Aulanier, G.; Georgoulis, M. K.; Rust, D. M.; Bernasconi, P. N. Bibcode: 2002ESASP.506..911S Altcode: 2002svco.conf..911S; 2002ESPM...10..911S Flare Genesis Experiment (FGE), a balloon borne Observatory was launched in Antarctica on January 10, 2000 and flew during 17 days. FGE consists of an 80 cm Cassegrain telescope with an F/1.5 ultra-low-expansion glass primary mirror and a crystalline silicon secondary mirror. A helium-filled balloon carried the FGE to an altitude of 37 km (Bernasconi et al. 2000, 2001). We select among all the observations a set of high spatial and temporal resolution observations of an emerging active region with numerous Ellerman bombs (EBs). Statistical and morphology analysis have been performed. We demonstrate that Ellerman bombs are the result of magnetic reconnection in the low chromosphere by a magnetic topology analysis. The loci of EBs coincide with "bald patches" (BPs). BPs are regions where the vector field is tangential to the boundary (photosphere) along an inversion line. We conclude that emerging flux through the photosphere is achieved through resistive emergence of U loops connecting small Ω loops before rising in the chromosphere and forming Arch Filament System (AFS). Title: Statistics, morphology, and energetics of Ellerman bombs Authors: Georgoulis, Manolis K.; Rust, David M.; Bernasconi, Pietro N.; Schmieder, Brigitte Bibcode: 2002ESASP.505..125G Altcode: 2002IAUCo.188..125G; 2002solm.conf..125G We have performed a detailed analysis of several hundreds Hα Ellerman bombs in the low chromosphere, above an emerging flux region. We find that Ellerman bombs may be small-scale, low-altitude, magnetic reconnection events that heat the low chromosphere in the active region. Their energy content varies between 1027 erg and 1028 erg, typical of sub-flaring activity. Title: The Near-Infrared Chromosphere Observatory Authors: Rust, David M.; Bernasconi, Pietro N.; Labonte, Barry J.; Georgoulis, Manolis K.; Fox, Nicola J.; Kalkofen, Wolfgang; Lin, Haoseng Bibcode: 2002ESASP.505..561R Altcode: 2002IAUCo.188..561R; 2002solm.conf..561R The Near-Infrared Chromosphere Observatory (NICO) is a proposed balloon-borne observatory aiming to investigate the magnetic structure and the sources of heating in the solar chromosphere. NICO will be based on the successful Flare Genesis Experiment (FGE), a pioneer in applying novel technologies for the study of the Sun. NICO will map magnetic fields, velocity fields, and heating events in the chromosphere with unprecedented quality. Title: Vector magnetic field observations of flux tube emergence Authors: Schmieder, B.; Aulanier, G.; Pariat, E.; Georgoulis, M. K.; Rust, D. M.; Bernasconi, P. N. Bibcode: 2002ESASP.505..575S Altcode: 2002IAUCo.188..575S; 2002solm.conf..575S With Flare Genesis Experiment (FGE), a balloon borne Observatory high spatial and temporal resolution vector magnetograms have been obtained in an emerging active region. The comparison of the observations (FGE and TRACE) with a linear force-free field analysis of the region shows where the region is non-force-free. An analysis of the magnetic topology furnishes insights into the existence of "bald patches" regions (BPs are regions where the vector field is tangential to the boundary (photosphere) along an inversion line). Magnetic reconnection is possible and local heating of the chromopshere is predicted near the BPs. Ellerman bombs (EBs) were found to coincide with few BPs computed from a linear force-free extrapolation of the observed longitudinal field. But when the actual observations of transverse fields were used to identify BPs, then the correspondence with EB positions improved significantly. We conclude that linear force-free extrapolations must be done with the true observed vertical fields, which require the measurement of the three components of the magnetic field. Title: Moving Dipolar Features in an Emerging Flux Region Authors: Bernasconi, P. N.; Rust, D. M.; Georgoulis, M. K.; Labonte, B. J. Bibcode: 2002SoPh..209..119B Altcode: On 25 January, 2000, we observed active region NOAA 8844 with the Flare Genesis Experiment (FGE), a balloon-borne observatory with an 80-cm solar telescope. FGE was equipped with a vector polarimeter and a tunable Fabry-Pérot narrow-band filter. It recorded time series of filtergrams, vector magnetograms and Dopplergrams at the Ca i 6122.2 Å line, and Hα filtergrams with a cadence between 2.5 and 7.5 min. At the time of the observations, NOAA 8844 was located at approximately 5° N 30° W. The region was growing rapidly; new magnetic flux was constantly emerging in three supergranules near its center. We report on the structure and behavior of peculiar moving dipolar features (MDFs) in the emerging flux, and we describe in detail how the FGE data were analyzed. In longitudinal magnetograms, the MDFs appeared to be small dipoles flowing into sunspots and supergranule boundaries. Previously, dipolar moving magnetic features (MMFs) have only been observed flowing out from sunspots. The FGE vector magnetograms show that the MDFs occurred in a region with nearly horizontal fields, the MDFs being distinguished as undulations in these fields. We identify the MDFs as stitches where the emerging flux ropes were still tied to the photosphere by trapped mass. We present a U-loop model that accounts for their unusual structure and behavior, as well as showing how emerging flux sheds entrained mass. Title: Statistics, Morphology, and Energetics of Ellerman Bombs Authors: Georgoulis, Manolis K.; Rust, David M.; Bernasconi, Pietro N.; Schmieder, Brigitte Bibcode: 2002ApJ...575..506G Altcode: We investigate the statistical properties of Ellerman bombs in the dynamic emerging flux region NOAA Active Region 8844, underneath an expanding arch filament system. High-resolution chromospheric Hα filtergrams (spatial resolution 0.8"), as well as photospheric vector magnetograms (spatial resolution 0.5") and Dopplergrams, have been acquired by the balloon-borne Flare Genesis Experiment. Hα observations reveal the first ``seeing-free'' data set on Ellerman bombs and one of the largest samples of these events. We find that Ellerman bombs occur and recur in preferential locations in the low chromosphere, either above or in the absence of photospheric neutral magnetic lines. Ellerman bombs are associated with photospheric downflows, and their loci follow the transverse mass flows on the photosphere. They are small-scale events, with typical size 1.8"×1.1" , but this size depends on the instrumental resolution. A large number of Ellerman bombs are probably undetected, owing to limited spatial resolution. Ellerman bombs occur in clusters that exhibit fractal properties. The fractal dimension, with an average value ~1.4, does not change significantly in the course of time. Typical parameters of Ellerman bombs are interrelated and obey power-law distribution functions, as in the case of flaring and subflaring activity. We find that Ellerman bombs may occur on separatrix, or quasi-separatrix, layers, in the low chromosphere. A plausible triggering mechanism of Ellerman bombs is stochastic magnetic reconnection caused by the turbulent evolution of the low-lying magnetic fields and the continuous reshaping of separatrix layers. The total energies of Ellerman bombs are estimated in the range (1027, 1028) ergs, the temperature enhancement in the radiating volume is ~2×103 K, and the timescale of radiative cooling is short, of the order of a few seconds. The distribution function of the energies of Ellerman bombs exhibits a power-law shape with an index ~-2.1. This suggests that Ellerman bombs may contribute significantly to the heating of the low chromosphere in emerging flux regions. Title: Helicity Build-up and the Role of CMEs Authors: Rust, D. M. Bibcode: 2002AAS...200.6503R Altcode: 2002BAAS...34..751R Coronal mass ejections are often associated with interplanetary magnetic clouds, whose fields are regularly probed with sensitive magnetometers. The measurements reveal that magnetic cloud fields are helical, and each cloud carries helicity away from the sun. There is no known mechanism for returning helicity to the sun. This talk will survey the possible solar sources of magnetic helicity. Included are fieldline footpoint motions, effects of Coriolis forces, effects of convection, shear associated with differential rotation, and, of course, the internal dynamo. Besides the survey of possible mechanisms for helicity generation, we will consider the global view of the flow of helicity from the sun into interplanetary space. This work is supported by the NASA Solar and Heliospheric Physics Program under grant NAG5-7921. Title: The Near-Infrared Chromosphere Observatory (NICO) Authors: Rust, D. M.; Bernasconi, P. N.; LaBonte, B. J.; Georgoulis, M. K.; Kalkofen, W.; Fox, N. J.; Lin, H. Bibcode: 2002AAS...200.3902R Altcode: 2002BAAS...34..701R NICO is a proposed cost-effective platform for determining the magnetic structure and sources of heating for the solar chromosphere. It is a balloon-borne observatory that will use the largest solar telescope flying and very high data rates to map the magnetic fields, velocities, and heating events of the chromosphere and photosphere in unprecedented detail. NICO is based on the Flare Genesis Experiment (FGE), which has pioneered in the application of technologies important to NASA's flight program. NICO will also introduce new technologies, such as wavefront sensing for monitoring telescope alignment; real-time correlation tracking and high-speed image motion compensation for smear-free imaging; and wide aperture Fabry-Perot filters for extended spectral scanning. The telescope is a classic Cassegrain design with an 80-cm diameter F/1.5 primary mirror made of Ultra-Low-Expansion glass. The telescope structure is graphite-epoxy for lightweight, temperature-insensitive support. The primary and secondary mirror surfaces are coated with silver to reflect more than 97% of the incident solar energy. The secondary is made of single-crystal silicon, which provides excellent thermal conduction from the mirror surface to its mount, with negligible thermal distortion. A third mirror acts as a heat dump. It passes the light from a 15-mm diameter aperture in its center, corresponding to a 322"-diameter circle on the solar surface, while the rest of the solar radiation is reflected back out of the front of the telescope. The telescope supplies the selected segment of the solar image to a polarization and spectral analysis package that operates with an image cadence 1 filtergram/sec. On-board data storage is 3.2 Terabytes. Quick-look images will be sent in near real time to the ground via the TDRSS communications link. Title: Photospheric Vertical Current Density and Overlying Atmospheric Activity in an Emerging Flux Region Authors: Georgoulis, M. K.; Rust, D. M.; Bernasconi, P. N.; Schmieder, B. Bibcode: 2002AAS...200.2004G Altcode: 2002BAAS...34..673G Using high-resolution vector magnetograms obtained by the balloon-borne Flare Genesis Experiment (FGE), we construct maps of the vertical current density in the emerging flux region NOAA 8844. The vertical current density has been decomposed into components that are field-aligned and perpendicular to the magnetic field, thus allowing a straightforward identification of force-free areas, as well as of areas where the force-free approximation breaks down. Small-scale chromospheric activity, such as H α Ellerman bombs and Ultraviolet bright points in 1600 Åshow a remarkable correlation with areas of strong current density. Simultaneous data of overlying coronal loops, observed by TRACE in the Extreme Ultraviolet (171 Åand 195 Å), have been carefully co-aligned with the FGE photospheric maps. We find that the footpoints of the TRACE loops always coincide with strong vertical currents and enhancements of the current helicity density. We also investigate whether the force-free approximation is valid on the photosphere during various evolutionary stages of the active region. Title: Investigation of the Sources of Irradiance Variation on the Sun (ISIS) Authors: LaBonte, B. J.; Bernasconi, P. N.; Rust, D.; Foukal, P.; Hudson, H.; Spruit, H. Bibcode: 2002AAS...200.5608L Altcode: 2002BAAS...34..736L There is a persistent correlation of the longterm climate change and solar irradiance. ISIS is designed to understand the physical basis of this correlation. ISIS combines an innovative bolometric imager and a multiband CCD imager. The bolometric imager has uniform response from 200 nm to 3000 nm, spatial resolution < 5 arcseconds, and precision of < 0.1% in a one minute integration. The multiband imager records ultraviolet irradiance variation in the band from 200 to 350 nm, measures photospheric temperature structure, and provides chromospheric structure in Ca II K and H-alpha, with spatial resolution <1.0 arcsecond. Designed for flight on the Solar Dynamics Observatory, ISIS will provide the comprehensive photometric measurements needed to characterize the irradiance variation from identifiable structures and challenge theoretical models of convection and the solar dynamo. Title: The Solar Bolometric Imager Authors: Bernasconi, P. N.; Foukal, P.; Rust, D. M. Bibcode: 2002AAS...200.5605B Altcode: 2002BAAS...34R.735B The Solar Bolometric Imager (SBI) is an innovative solar telescope capable of recording images in essentially total photospheric light, with an angular resolution of 5", sufficient to distinguish sunspots, faculae and enhanced network. These are the photospheric magnetic structures so far linked most closely to irradiance variation. The balloon-borne SBI will provide the first bolometric maps of the photosphere, to evaluate the photometric contribution of magnetic structures more accurately than has been achievable so far, using spectrally selective imaging over restricted wavebands. More accurate removal of the magnetic feature contribution will enable us to determine whether other solar irradiance mechanisms exist besides the effects of photospheric magnetism. The SBI detector is an array of 320 X 240 ferro-electric thermal IR elements whose spectral absorptance has been extended and flattened by a deposited layer of gold-black. The telescope itself is a 30-cm Dall-Kirkham design with uncoated primary and secondary pyrex mirrors. The combination of telescope and bolometric array provides an image of the solar irradiance with a flat spectral response between 0.28 um and 2.6 um, over a field of view of 15.2' X 11.4', and a pixel size of 2.8". After a successful set of ground-based tests, the instrument is being readied for a one-day stratospheric balloon flight that will take place in September 2003. The observing platform will be the gondola previously used for the Flare Genesis Experiment project (FGE), retrofitted to house and control the SBI telescope and detector. The balloon flight will enable SBI to image over essentially the full spectral range accepted by non-imaging space borne radiometers such as ACRIM, making the data sets complementary. The SBI flight will also provide important engineering data to validate the space worthiness of the novel gold-blackened thermal array detectors, and verify the thermal performance of the SBI's uncoated optics in a vacuum environment. This work was funded by NASA under grant NAG5-10998. Title: An Automated System for Detecting Sigmoids in Solar X-ray Images Authors: LaBonte, B. J.; Rust, D. M.; Bernasconi, P. N. Bibcode: 2002AGUSMSH52A..02L Altcode: The probability of a coronal mass ejection (CME) occurring is linked to the appearance of structures, called sigmoids, in satellite X-ray images of the sun. By examination of near real time images, we can detect sigmoids visually and estimate the probability of a CME and the probability that it will cause a major geomagnetic storm. We have devised a pattern recognition system to detect the sigmoids in Yohkoh and GOES (when available) X-ray images automatically. When implemented in a near real time environment, this system should allow long term, 3 - 7 day, forecasts of CMEs and their potential for causing major geomagnetic storms. Title: Magnetic helicity, coronal mass ejections and the solar cycle Authors: Rust, David M. Bibcode: 2002ESASP.477...39R Altcode: 2002scsw.conf...39R Here is a brief review of current thinking about the origin and function of magnetic helicity in coronal mass ejections. Magnetic helicity is thought to be generated either by the solar dynamo, by Coriolis forces in the turbulent convection zone, or by differential rotation's effective shearing of coronal fields. The mechanisms are discussed, especially with regard to what they suggest that observers should use to detect the build-up of helicity in coronal features so that the onset of a CME can be forecast. Title: Magnetic measurements of flux emergence Authors: Rust, David Bibcode: 2002ocnd.confE..33R Altcode: No abstract at ADS Title: Comparison of magnetic helicity close to the sun and in magnetic clouds Authors: Rust, D. Bibcode: 2002cosp...34E1203R Altcode: 2002cosp.meetE1203R Magnetic helicity is present in the solar atmosphere - as inferred from vector magnetograph measurements, solar filaments, S-shaped coronal structures known as sigmoids, and sunspot whorls. I will survey the possible solar sources of this magnetic helicity. Included are fieldline footpoint motions, effects of Coriolis forces, effects of convection, shear associated with differential rotation, and, of course, the internal dynamo. Besides the survey of possible local mechanisms for helicity generation, I will consider the global view of the flow of helicity from the sun into interplanetary space. The principal agents by which the sun sheds helicity are coronal mass ejections (CMEs). They are often associated with interplanetary magnetic clouds (MCs), whose fields are regularly probed with sensitive spacecraft magnetometers. MCs yield more direct measurements of helicity. They show that each MC carries helicity away from the sun. A major issue in solar-heliospheric research is whether the amount of helicity that MCs carry away in a solar cycle can be accounted for by the helicity generation mechanisms proposed so far. The NASA Solar and Heliospheric Physics Program supports this work under grants NAG5- 7921 and NAG 5-11584. Title: The solar bolometric imager Authors: Rust, D.; Bernasconi, P.; Foukal, P. Bibcode: 2002cosp...34E1200R Altcode: 2002cosp.meetE1200R The balloon-borne Solar Bolometric Imager (SBI) will provide the first bolometric (integrated light) maps of the photosphere, to evaluate the photometric contribution of magnetic structures more accurately than has been achievable with spectrally selective imaging over restricted wavebands. More accurate removal of the magnetic feature contribution will enable us to determine if solar irradiance variation mechanisms exist other than the effects of photospheric magnetism. The SBI detector is an array of 320 x 240 ferro -electric thermal IR elements whose spectral absorptance has been extended and flattened by a deposited layer of gold- black. The telescope itself is a 30-cm Dall-Kirkham design with uncoated primary and secondary pyrex mirrors. The combination of telescope and bolometric array provides an image of the sun with a flat spectral response between 0.28 microns and 2.6 microns, over a field of view of 15.2 x 11.4 min, and a pixel size of 2.8 arcsec. After a successful set of ground-based tests, the instrument is being readied for a one-day stratospheric balloon flight that will take place in September 2003. The observing platform will be the gondola previously used for the Flare Genesis Experiment (FGE), retrofitted to house and control the SBI telescope and detector. The balloon flight will enable SBI to image over essentially the full spectral range accepted by non-imaging space-borne radiometers such as ACRIM, making the data sets complementary. The SBI flight will also provide important engineering data to validate the space worthiness of the novel gold-blackened thermal array detectors, and verify the thermal performance of the SBI's uncoated optics in a vacuum environment. This work was funded by NASA under grant NAG5-10998. Title: The Flare Genesis Experiment Authors: Rust, D. M. Bibcode: 2002STIN...0246802R Altcode: Using the Flare Genesis Experiment (FGE), a balloon-borne observatory with an 80-cm solar telescope we observed the active region NOAA 8844 on January 25, 2000 for several hours. FGE was equipped with a vector polarimeter and a tunable Fabry-Perot narrow-band filter. It recorded time series of filtergrams, vector magnetograms, and Dopplergrams at the Ca(I) 6122.2 angstrom line, and H-alpha filtergrams with a cadence between 2.5 and 7.5 minutes. At the time of the observations, NOAA 8844 was located at approximately 5 N 30 W. The region was rapidly growing during the observations; new magnetic flux was constantly emerging in three supergranules near its center. We describe in detail how the FGE data were analyzed and report on the structure and behavior of peculiar moving dipolar features (MDFs) observed in the active region. In longitudinal magnetograms, the MDFs appeared to be small dipoles in the emerging fields. The east-west orientation of their polarities was opposite that of the sunspots. The dipoles were oriented parallel to their direction of motion, which was in most cases towards the sunspots. Previously, dipolar moving magnetic features have only been observed flowing out from sunspots. Vector magnetograms show that the magnetic field of each MDF negative part was less inclined to the local horizontal than the ones of the positive part. We identify the MDFs as undulations, or stitches, where the emerging flux ropes are still tied to the photosphere. We present a U-loop model that can account for their unusual structure and behavior, and it shows how emerging flux can shed its entrained mass. Title: A new paradigm for solar filament eruptions Authors: Rust, David M. Bibcode: 2001JGR...10625075R Altcode: This article discusses the formation, magnetic structure, and eruption of solar filaments in terms of two contrasting paradigms. The standard paradigm is that filaments are formed by condensation of plasma on coronal magnetic fields that are twisted or dimpled as a result of photospheric motions. According to this paradigm, filaments erupt when photospheric motions shear the fields, increasing their energy and decreasing their stability. According to a new paradigm, subsurface motions generate toroidal magnetic flux ropes, and after these flux ropes emerge to form active regions, the most twisted parts migrate into the corona to form filaments. Filaments become unstable and are ejected after a sufficient accumulation of twist (i.e., magnetic helicity). Various proposed mechanisms for producing the needed helicity are reviewed, and several observational tests are proposed to differentiate among the possible mechanisms. Title: Sunspot Formation from Emerging Flux Ropes - Observations from Flare Genesis Authors: Rust, D. M.; Bernasconi, P. N.; Georgoulis, M. K.; LaBonte, B. J.; Schmieder, B. Bibcode: 2001AGUSM..SP42A09R Altcode: From January 10 to 27, 2000, the Flare Genesis payload observed the Sun while suspended from a balloon in the stratosphere above Antarctica. The goal of the mission was to acquire a long time series of high-resolution images and vector magnetograms of the solar photosphere and chromosphere. We obtained images, magnetograms and Dopplergrams in the magnetically sensitive Ca I line at 6122 Angstroms. Additional simultaneous images were obtained in the wing of H-alpha. On January 25, 2000, we observed in NOAA region 8844 at N05 W30. The rapid development of a sunspot group that apparently included a delta spot (two polarities within one umbra). We considered a variety of models for interpreting these observations, including a twisted flux tube, a bipole that annihilates, a bipole that submerges, and a field distorted by mass loading. From the vector magnetograms and Doppler measurements, we conclude that nearly horizontal flux ropes are swept into the developing spot where they tilt upward to contribute to the familiar nearly vertical sunspot fields. The largest flux rope exhibited a twisted structure, and its angle with respect to the vertical was so great that it could be mistaken for a positive magnetic field merging into a negative sunspot. Flare Genesis was supported by NASA grant NAG5-8331 and by NSF grant OPP-9909167. Title: Ellerman Bombs in a Solar Active Region: Statistical Properties and Implications Authors: Georgoulis, M. K.; Rust, D. M.; Bernasconi, P. N. Bibcode: 2001AGUSM..SP52B05G Altcode: We have embedded the concept of Self-Organized Criticality (SOC) in deterministic Cellular Automata (CA) models in an attempt to simulate the emergence of flaring and sub-flaring activity in solar active regions. SOC CA models reproduce reasonably well several aspects of the statistical properties of flares and, moreover, they allow predictions regarding the respective properties of the unresolved nanoflares. We compare the above-mentioned predictions with observed arcsecond and sub-arcsecond activity on the low-chromosphere, in a newly formed active region. The source of the observations is the Flare Genesis Experiment (FGE) which has provided us with high-resolution maps of the magnetic field and the velocity field vectors on the photospheric boundary, as well as Hα filtergrams on the low-chromosphere. Moreover, UV and EUV data from TRACE are used for determining the activity on the overlying atmospheric layers. We present preliminary results on the statistical properties of transient Hα brightenings (Ellerman Bombs) which correlate well with significant overlying UV emission. Implications of these results, as well as potential directions for modeling the low-lying activity in the solar atmosphere are discussed. This work was sponsored by NASA grant NAG5-8331 and NSF grant OPP-9909162 Title: Peculiar Moving Magnetic Features Observed With the Flare Genesis Experiment Authors: Bernasconi, P. N.; Rust, D. M.; Georgoulis, M. K.; LaBonte, B. J.; Schmieder, B. Bibcode: 2001AGUSM..SP51A02B Altcode: With the Flare Genesis Experiment (FGE), a balloon-borne 80-cm solar telescope, we observed the active region NOAA 8844 on January 25, 2000 for several hours. FGE was equipped with a vector polarimeter and a lithium-niobate Fabry-Perot narrow-band filter. It recorded time series of filtergrams, vector magnetograms, and dopplergrams at the CaI 6122.2 Angstroms line, as well as Hα filtergrams, with a cadence between 2.5 and 7.5 minutes. At the time of the observations NOAA 8844 was located at approximately 5 deg N, 30 deg W. It was a new flux emergence that first appeared on the solar disk two days before and was still showing a very dynamic behavior. Its two main polarity parts were rapidly moving away from each other and new magnetic flux was constantly emerging from its center. Here we describe the structure and behavior of peculiar small moving magnetic dipoles (called moving magnetic features MMF's) that we observed near the trailing negative polarity sunspot of NOAA 8844. Presentations by D. M. Rust, and by M. K. Georgoulis at this meeting will focus on other aspects of the same active region. The MMF's took the form of small dipoles that first emerged into the photosphere near the center of a supergranular cell located next to the main trailing flux concentration. They rapidly migrated towards the spot, following the supergranular flow. The two polarities of the little dipoles did not separate; they moved together with same speed and in the same direction. The dipoles were oriented parallel to their motion toward the negative spot, with the positive polarity always leading. MMF's usually move away from sunspots, and their orientation is the reverse of what we see here. In addition, we noted that the dipole structure was not symmetric. The field lines of the trailing part of the MMF's (negative polarity) were always much more perpendicular to the local horizontal than the ones of the leading part. The trailing part looked more compact and circular, while the leading part was more elongated in the direction of the motion. We conclude that we observed a new type of MMF's with a totally different magnetic structure than previously seen. We present a possible model that could explain their unusual structure and behavior. This work was supported by NASA grant NAG5-8331 and NSF grant OPP-9909167. Title: High Resolution Vector Magnetograms with the Flare Genesis Vector Polarimeter Authors: Bernasconi, P. N.; Rust, D. M.; Eaton, H. A. C. Bibcode: 2001ASPC..236..399B Altcode: 2001aspt.conf..399B No abstract at ADS Title: The origin and development of the May 1997 magnetic cloud Authors: Webb, D. F.; Lepping, R. P.; Burlaga, L. F.; DeForest, C. E.; Larson, D. E.; Martin, S. F.; Plunkett, S. P.; Rust, D. M. Bibcode: 2000JGR...10527251W Altcode: A complete halo coronal mass ejection (CME) was observed by the SOHO Large-Angle and Spectrometric Coronagraph (LASCO) coronagraphs on May 12, 1997. It was associated with activity near Sun center, implying that it was aimed earthward. Three days later on May 15 an interplanetary shock and magnetic cloud/flux rope transient was detected at the Wind spacecraft 190 RE upstream of Earth. The long enduring southward magnetic fields associated with these structures triggered a geomagnetic storm. The CME was associated with a small coronal arcade that formed over a filament eruption with expanding double ribbons in Hα emission. The flare was accompanied by a circular EUV wave, and the arcade was flanked by adjacent dimming regions. We surmise that these latter regions marked the feet of a flux rope that expanded earthward into the solar wind and was observed as the magnetic cloud at Wind. To test this hypothesis we determined key parameters of the solar structures on May 12 and compared them with the modeled flux rope parameters at Wind on May 15. The measurements are consistent with the flux rope originating in a large coronal structure linked to the erupting filament, with the opposite-polarity feet of the rope terminating in the depleted regions. However, bidirectional electron streaming was not observed within the cloud itself, suggesting that there is not always a good correspondence between such flows and ejecta. Title: Solar Chromosphere: Ellerman Bombs Authors: Rust, D. Bibcode: 2000eaa..bookE2263R Altcode: In 1917, Ellerman discovered short-lived, intense brightenings at tiny (<1 arcsec) points in the lower solar CHROMOSPHERE. A typical Ellerman bomb lasts less than 10 min. Its spectrum is characterized by very broad emission wings on the hydrogen Balmer lines. On a photographic negative, the pattern of a bomb's emission resembles a mustache or whisker. Reinforcing the allusion to mustaches is the ... Title: Solar Prominences Authors: Rust, D. Bibcode: 2000eaa..bookE2044R Altcode: Prominences are clouds of relatively cool and dense gas in the solar atmosphere. These clouds change shape and come and go, but they do not drift like terrestrial clouds. Prominences are suspended above magnetic channels (see SOLAR FILAMENT CHANNELS) that change little from day to day. They are trapped in magnetic fields in the solar atmosphere, but they churn slowly, at heights of up to 100 000 ... Title: The Solar Terrestrial Relations Observatory - Mission Overview Authors: Davila, J. M.; Rust, D. M.; Sharer, P. J. Bibcode: 2000SPD....31R0293D Altcode: 2000BAAS...32.1291D Starting in 2004, the two identical STEREO spacecraft will drift slowly off the Sun-Earth line, providing a series of differing perspectives on CMEs and other solar and heliospheric structures. At the end of the prime science (2-year) mission, the spacecraft will each be about 45 degrees from Earth, one leading Earth and one trailing. Each spacecraft will carry a cluster of telescopes, including coronagraphs, EUV imagers, and particle detectors. When the images are combined with solar magnetograms and other data from observatories on the ground or in low Earth orbit, both the buildup of magnetic energy and the lift off and trajectory of CMEs can be studied. Interpreting the STEREO data will pose a new challenge to the solar community. We discuss the STEREO mission design, instrument complement and the development of the trajectory design that, we believe, maximizes the scientific potential of the mission. Title: Solar Filaments as Tracers of Sub-surface Processes Authors: Rust, D. M. Bibcode: 2000JApA...21..177R Altcode: No abstract at ADS Title: Balloon-borne telescope for high-resolution solar imaging and polarimetry Authors: Bernasconi, Pietro N.; Rust, David M.; Eaton, Harry A.; Murphy, Graham A. Bibcode: 2000SPIE.4014..214B Altcode: In January 2000, an 80-cm F/1.5 Ritchey-Chretien solar telescope flew for 17 days suspended from a balloon in the stratosphere above Antarctica. The goal was to acquire long time series of high spatial resolution images and vector- magnetograms of the solar photosphere and chromosphere. Such observations will help to advance our basic scientific understanding of solar activity, in particular flares. Flying well above the turbulent layers of the Earth's atmosphere, the telescope should be able to operate close to its diffraction limited resolution of 0.2 arcsec, providing high resolution observations of small scale solar features. To achieve this goal we developed a platform for the optical telescope that is stable to nearly 10 arcsec. We also developed an image motion compensation system that stabilizes the solar image on the CCD focal plane to about 1 arcsec. Title: New Results from the Flare Genesis Experiment Authors: Rust, D. M.; Bernasconi, P. N.; Eaton, H. A.; Keller, C.; Murphy, G. A.; Schmieder, B. Bibcode: 2000SPD....31.0302R Altcode: 2000BAAS...32..834R From January 10 to 27, 2000, the Flare Genesis solar telescope observed the Sun while suspended from a balloon in the stratosphere above Antarctica. The goal of the mission was to acquire long time series of high-resolution images and vector magnetograms of the solar photosphere and chromosphere. Images were obtained in the magnetically sensitive Ca I line at 6122 Angstroms and at H-alpha (6563 Angstroms). The FGE data were obtained in the context of Max Millennium Observing Campaign #004, the objective of which was to study the ``Genesis of Solar Flares and Active Filaments/Sigmoids." Flare Genesis obtained about 26,000 usable images on the 8 targeted active regions. A preliminary examination reveals a good sequence on an emerging flux region and data on the M1 flare on January 22, as well as a number of sequences on active filaments. We will present the results of our first analysis efforts. Flare Genesis was supported by NASA grants NAG5-4955, NAG5-5139, and NAG5-8331 and by NSF grant OPP-9615073. The Air Force Office of Scientific Research and the Ballistic Missile Defense Organization supported early development of the Flare Genesis Experiment. Title: Design and Performance of the Flare Genesis Experiment Authors: Bernasconi, P. N.; Rust, D. M.; Eaton, H. A.; Murphy, G. A. Bibcode: 2000SPD....31.0289B Altcode: 2000BAAS...32..826B In January 2000, an 80-cm F/1.5 Ritchey-Chretien solar telescope flew for18 days suspended from a balloon in the stratosphere above Antarctica. The goal of the flight was to acquire long time series of high-resolution images and vector magnetograms of the solar photosphere and chromosphere. Such observations will help to advance our basic scientific understanding of solar activity, in particular, flares and coronal mass ejections. Flying well above the turbulent layers of the Earth's atmosphere, the telescope obtained unprecedented sharp and stable observations of small-scale solar features. To achieve this goal we developed a platform for the optical telescope that is stable to nearly 10 arcsec. In addition, we developed an image motion compensation system that stabilizes the solar image on the focal plane to about 1 arcsec. When the payload was in line of sight with the ground station, communications were accomplished via a low-speed radio link for sending commands and receiving telemetry and a high-speed downlink for receiving images. During the rest of the flight, contact with the payload was sporadic and only instrument status could be telemetered down. After the flight, the data were recovered from on-board tapes. This presentation will focus on the description of the instrument and its operating principle. Preliminary results from the January 2000 flight will be presented in a companion paper. Title: Solar physics at APL. Authors: Rust, D. M. Bibcode: 1999JHATD..20..570R Altcode: Solar reserach at APL aims to understand the fundamental physics that govern solar activity. The tools are telescopes, models, and interplanetary sampling of solar ejecta. The work is relevant to APL's mission because solar energetic protons disable satellites and endanger astronauts. Solar activity also causes geomagnetic storms, which can lead to communications disruptions, electric power network problems, satellite orbit shifts and, sometimes, satellite failure. Predicting storm conditions requires understanding solar magnetism and its fluctuations. APL scientists have made major contributions to solar activity research and have taken the lead in developing a variety of new solar research tools. They are now starting work on the Solar Terrestrial Relations Observatory, a major space mission. Title: A Search for Toroidal Magnetic Fields in the Solar Photosphere Authors: Rust, D. M. Bibcode: 1999AAS...194.9404R Altcode: 1999BAAS...31..991R Observations of an East-West asymmetry in photospheric magnetic fields, as reported by Duvall et al. (Solar Phys. 61, 233, 1979), Howard (Solar Phys. 39, 275, 1974, and Solar Phys. 134, 233, 1991), and Shrauner and Scherrer (Solar Phys. 153, 131, 1994) may possibly be explained in terms of a normal component contaminated by a toroidal component. The toroidal component has already been traced in solar filaments and by its effect on chromospheric fine structure. Taking advantage of the highly stable observing conditions offered by the SOHO Michelson-Doppler Imager (MDI), we searched for evidence of toroidal fields in the photosphere. Although the MDI is sensitive only to the line-of-sight component of the fields, toroidal fields reveal themselves by East-West asymmetries in average field strength and in large-scale features, such as boundaries between positive and negative fields. We report on analysis of calibrated full-disk MDI magnetograms for a one-year period. Title: High Resolution polarimetry with a Balloon-Borne Telescope: The Flare Genesis Experiment Authors: Bernasconi, P.; Rust, D.; Murphy, G.; Eaton, H. Bibcode: 1999ASPC..183..279B Altcode: 1999hrsp.conf..279B No abstract at ADS Title: Intercomparison of NEAR and Wind interplanetary coronal mass ejection observations Authors: Mulligan, T.; Russell, C. T.; Anderson, B. J.; Lohr, D. A.; Rust, D.; Toth, B. A.; Zanetti, L. J.; Acuna, M. H.; Lepping, R. P.; Gosling, J. T. Bibcode: 1999JGR...10428217M Altcode: Nearly 4 months of continuous interplanetary magnetic field measurements September 1997 through December 1997 have allowed us to compare four interplanetary coronal mass ejection (ICME) events seen by the NEAR and Wind spacecraft. When the spacecraft are in close proximity (separated by 1° in azimuth relative to the sun) the ICMEs seen by Wind and NEAR have similar signatures as expected for structures with dimensions along the solar wind flow of ~0.2 AU. When the NEAR spacecraft is separated by ~5.4° in azimuth from the Earth the vector signature of ICMEs seen at NEAR begins to differ from those seen at Wind even though the magnitude of the field in the events and the background solar wind show similarities at the two spacecraft. When the spacecraft are separated by 11.3° the magnetic signatures are quite different and sometimes ICMEs are seen only at one of the two locations. Nevertheless, in all cases the magnetic helicity of the cloud structures seen at NEAR is the same as at Wind. The radial speeds of the shock and ICME leading edge as they cross Wind and the time delays of those events, for which we have some assurance that they also arrived at NEAR, indicate that the ICMEs decelerate measurably as they travel near 1 AU. Title: Magnetic Helicity in Solar Filaments and Coronal Mass Ejections Authors: Rust, D. M. Bibcode: 1999GMS...111..221R Altcode: 1999mhsl.conf..221R Erupting solar filaments are often coiled and the knots of plasma in them rotate as though constrained to follow helical magnetic field lines. Starting with this evidence of magnetic helicity in filaments, this article reviews observations and recent models of solar filaments with an emphasis on how to infer their magnetic helicity. Results from telescopic observations are often controversial. They are being supplemented by in situ measurements of the ejected magnetic fields and plasmas that pass by interplanetary spacecraft. Correlations of solar events with interplanetary magnetic cloud properties yield insights into the nature of magnetic helicity on the Sun. Examples include the segregation of magnetic helicity, with negative/positive helicity dominating in the north/south, and an association of filament eruptions with helical kink instabilities. Title: The Solar STEREO Mission Authors: Rust, D. M. Bibcode: 1998ESASP.417..133R Altcode: 1998cesh.conf..133R No abstract at ADS Title: New Perspectives on Solar Prominences Authors: Webb, David F.; Schmieder, Brigitte; Rust, David M. Bibcode: 1998ASPC..150.....W Altcode: 1998npsp.conf.....W; 1998IAUCo.167.....W No abstract at ADS Title: Solar Flares Authors: Rust, David Bibcode: 1998fsam.conf...81R Altcode: The Sun is constantly changing. Not an hour goes by without a rise or fall in solar x-radiation or radio emission. Not a day goes by without a solar flare. Our active star, this inconsistent Sun, this gaseous cloud that blows in all directions, warms the air we breathe and nourishes the food we eat. From Earth, it seems the very model of stability, but in space it often creates havoc. Over the past century, solar physicists have learned how to detect even the weakest of solar outbursts or flares. We know that flares must surely trace their origins to the magnetic strands stretched and tangled by the rolling plasma of the solar interior. Although a century of astrophysical research has produced widely accepted, fundamental understanding about the Sun, we have yet to predict successfully the emergence of any magnetic fields from inside the Sun or the ignition of any flare. As in any physical experiment, the ability to predict events not only validates the scientific ideas, it also has practical value. In astrophysics, a demonstrated understanding of sunspots, flares, and ejections of plasma would allow us to approach many other mysteries, such as stellar X-ray bursters, with tested theories. Title: European Plans for the Solar/Heliospheric Stereo Mission Authors: Bothmer, V.; Bougeret, J. -L.; Cargill, P.; Davila, J.; Delaboudiniere, J. -P.; Harrison, R.; Koutchmy, S.; Liewer, P.; Maltby, P.; Rust, D.; Schwenn, R. Bibcode: 1998ESASP.417..145B Altcode: 1998cesh.conf..145B No abstract at ADS Title: Analysis of SOHO Images and NEAR Magnetometer Data on the Coronal Mass Ejection from the Sun's West Limb on August 13, 1997 Authors: Rust, D. M.; Anderson, B. J.; Andrews, M. D.; Strachan, L.; Zanetti, L. J. Bibcode: 1998EOSTr..79..257R Altcode: Coronal observations made by the SOHO telescopes provide unprecedented information on coronal dynamics including corona mass ejections. The best images and spectra are obtained for events that take place within 30 degrees of the plane of the sky. It is difficult to combine analyses of these data with analyses of in-situ data on CME debris in interplanetary space because in-situ data are generally available only for events aimed at Earth. However, the NEAR (Near-Earth Asteroid Rendezvous) spacecraft trajectory to the asteroid Eros provides opportunities to combine interplanetary magnetic field observations well off the Sun-Earth line with SOHO coronal imaging. We present an analysis of a CME that was ejected off the west limb of the Sun on August 13, 1997. As observed by the SOHO telescopes, various features in the CME propagated outward with gradual acceleration so that at 29 solar radii, velocities of the features ranged between 260 and about 500 km/s, as projected into the observation plane. At this time the NEAR spacecraft was 58 to the west of the Sun-Earth line at a distance of 1.78 AU from the Sun. On August 20, 1997, the NEAR magnetometer observed a magnetic cloud with a clear flux rope signature for about 6 hours. The flux rope was embedded in the CME disturbance witch lasted approximately 30 hours at NEAR. The cloud arrival time at NEAR corresponds to time-averaged propagation speeds of 400 - 500 km/s. This strongly indicates that NEAR observed the magnetic cloud associated with the August 13 CME. The magnetic cloud field had right- hand helicity. The CME appears to have originated with the disappearance of a southern-hemisphere filament at 45 degrees west longitude. Southern- hemisphere filaments usually, have right-hand helicity. Since the twist of the field is known, we are searching for rotational motions in the CME which could indicate whether the CME fields are twisting up or unwinding. All in all, this study demonstrates the type of analyses that can be performed using coronal imaging and in-situ observations from spacecraft at widely separated heliolongitudes. Opportunities for such analyses are very rare now, and they are hindered by limited data sets in the best of cases, but they will be abundant during the Solar Stereo Mission. Title: The Solar-B Mission Authors: Antiochos, Spiro; Acton, Loren; Canfield, Richard; Davila, Joseph; Davis, John; Dere, Kenneth; Doschek, George; Golub, Leon; Harvey, John; Hathaway, David; Hudson, Hugh; Moore, Ronald; Lites, Bruce; Rust, David; Strong, Keith; Title, Alan Bibcode: 1997STIN...9721329A Altcode: Solar-B, the next ISAS mission (with major NASA participation), is designed to address the fundamental question of how magnetic fields interact with plasma to produce solar variability. The mission has a number of unique capabilities that will enable it to answer the outstanding questions of solar magnetism. First, by escaping atmospheric seeing, it will deliver continuous observations of the solar surface with unprecedented spatial resolution. Second, Solar-B will deliver the first accurate measurements of all three components of the photospheric magnetic field. Solar-B will measure both the magnetic energy driving the photosphere and simultaneously its effects in the corona. Solar-B offers unique programmatic opportunities to NASA. It will continue an effective collaboration with our most reliable international partner. It will deliver images and data that will have strong public outreach potential. Finally, the science of Solar-B is clearly related to the themes of origins and plasma astrophysics, and contributes directly to the national space weather and global change programs. Title: The Solar Terrestrial Relations Observatory (STEREO) Authors: Rust, D. M. Bibcode: 1997SPD....28.1103R Altcode: 1997BAAS...29..915R One of the most important scientific advances of the space age was the discovery of coronal mass ejections (CMEs). CMEs can severely disturb Earth's space environment, but lacking adequate perspective, no one can tell when a CME will impact Earth or with what effect. No one has a clear idea of CME structure or extent in interplanetary space. And, the events that most affect Earth are the ones least likely to be detected with ground-based or Earth-orbiting telescopes. STEREO will provide a totally new perspective on solar eruptions and their consequences for Earth. Achieving this perspective will require moving away from our customary lookout point. But STEREO means much more than stereo pictures. Two spacecraft will carry identical clusters of telescopes, including coronagraphs and X-ray or EUV imagers, and each will carry identical sets of plasma, magnetic field and energetic particle detectors. The principal science goal is to determine the structure and evolution of CMEs and their effects throughout the heliosphere. We will characterize CMEs at their onset, track them through interplanetary space, and sample them when the reach Earth's orbit. STEREO has been recommended for a NASA new start in year 2000 by the Sun Earth Connections Roadmap workshop. The mission is being studied by a Science Definition Team. The mission and the work of the team so far will be discussed. Title: Solar Vector Magnetic Field Research Authors: Rust, David M. Bibcode: 1997STIN...9841524R Altcode: The principal effort was development and flight of the Flare Genesis Experiment (FGE). The FGE is a balloon borne solar telescope that can provide the sharpest view ever of the evolution of activity on the Sun. The goal of the FGE is to obtain the observations needed for a breakthrough in solar flare research both sooner and at significantly lower cost than either a satellite or adaptive optics can offer. The FGE flight was a historic first. This effort has shown that a meter class solar telescope can take advantage of the modern long duration ballooning program in Antarctica to achieve science goals that are central to solar activity research. Title: Advanced Solar Probe Experiment Module (AD SOLEM) Authors: McNutt, Ralph L.; Gold, Robert E.; Keath, Edwin P.; Rust, David M.; Krimigis, Stamatios M.; Zanetti, Lawrence J.; Willey, C. E.; Williams, B. D.; Kurth, William S.; Gurnett, Donald A.; Acuna, Mario H.; Burlaga, L.; Gloeckler, G.; Ipavich, Fred M.; Lazarus, Alan J.; Steinburg, John T.; Brueckner, Guenter E.; Socker, Dennis G.; Holzer, Tom E.; Bochsler, Peter A.; Kallenbach, Reinald; Roux, Alain Bibcode: 1996SPIE.2804....2M Altcode: A small, low-power suite of fields and particles and imaging experiments is required for fulfilling the critical science objectives for a near-sun flyby mission. We discuss how an integrated instrument suite using novel sensors and advanced detector/microelectronics/packaging techniques can be implemented for such a payload. Critical tradeoffs between science requirements, measurement strategies and these resource limits are discussed, and critical enabling components are identified. The instrument site consists of 6 major investigations, some with multiple sensors, power conditioners for both high and low voltages and a common DPU. The concept design is essentially a dress-rehearsal of how a payload could realistically make the measurements needed to answer the critical science questions while operating within a real-world physics, engineering and technology context. Title: Missions to the Sun Authors: Rust, David M. Bibcode: 1996SPIE.2804.....R Altcode: No abstract at ADS Title: Heliospheric Links Explorer (HELIX) Authors: Rust, David M.; Crooker, N. U.; Golub, Leon; Hundhausen, A. J.; Lanzerotti, L. J.; Lazarus, Alan J.; Seehafer, Norbert; Zanetti, Lawrence J.; Zwickl, Ron W. Bibcode: 1996SPIE.2804...39R Altcode: The proposed HELIX mission consists of two spacecraft that will enable stereoscopic imaging of solar mass ejections, starting with their origins on the Sun and continuing to 1 AU and beyond. With a complement of telescopes and plasma detectors, the HELIX spacecraft will test magnetic helicity conservation and other approaches to understanding the physics of solar mass ejections. The mission will help explain how and why solar ejections occur and how they evolve in interplanetary space. 3D images and velocity maps and in-situ space plasma and magnetic field measurements will allow identification and tracking of ejected plasma. Detection of eruptions aimed at Earth will be an immediate practical benefit of the mission. The HELIX mission should lead to the development of a reliable storm prediction capability that will be of significant value to communications systems operators, electric power networks, NASA operators and others. Title: Flare Genesis Experiment Authors: Murphy, Graham A.; Rust, David M.; Strohbehn, Kim; Eaton, Harry A.; Keil, Stephen L.; Keller, Christoph U.; Wiborg, P. H. Bibcode: 1996SPIE.2804..141M Altcode: In January 1996, the Flare Genesis Experiment was carried for 19 days by a 29.4 M cu. ft helium-filled balloon in the stratosphere above Antarctica, during which over 14000 images of the Sun were recorded. Long-duration ballooning provides a relatively inexpensive means to observe the Sun under near-space conditions and to develop instrumentation and techniques that will be used on future solar space missions. The purpose of the flight was to improve understanding of the mechanisms involved in many different types of solar activity, particularly flares and solar filament eruptions. Achieving this goal demanded the development of a platform for an 80-cm F/1.5 optical telescope that would be stable to 10 arcseconds. In addition, we developed an image motion compensation system capable of holding the Sun's image to better than the system's 0.2 arcsecond diffraction limit. Other key elements on board included a lithium-niobate Fabry-Perot etalon filter to provide a tunable 0.016-nm bandpass over a wide wavelength range, a fast 1534 X 1024-pixel Kodak CCD camera, and 180 GBytes of on-board storage. There was also a system for sending commands and receiving telemetry and a high-speed downlink for sending images during periods when the payload was in line of sight of the ground station. On- board computers provided a command and control system capable of near-autonomous operation. During most of the flight, contact with the payload was sporadic, so operation was primarily under autonomous control. Title: Solar Terrestrial Relations Observatory (STEREO) Authors: Davila, Joseph M.; Rust, David M.; Pizzo, Victor J.; Liewer, Paulett C. Bibcode: 1996SPIE.2804...34D Altcode: The solar output changes on a variety of timescales, from minutes, to years, to tens of years and even to hundreds of years. The dominant timescale of variation is, of course, the 11-year solar cycle. Observational evidence shows that the physics of solar output variation is strongly tied to changes in the magnetic field, and perhaps the most dramatic manifestation of a constantly changing magnetic field is the Coronal Mass Ejection (CME). On August 5 - 6, 1996 the Second Workshop to discuss missions to observe these phenomena from new vantage points, organized by the authors, was held in Boulder, Colorado at the NOAA Space Environmental Center. The workshop was attended by approximately 20 scientists representing 13 institutions from the United States and Europe. The purpose of the Workshop was to discuss the different concepts for multi- spacecraft observation of the Sun which have been proposed, to develop a list of scientific objectives, and to arrive at a consensus description of a mission to observe the Sun from new vantage points. The fundamental goal of STEREO is to discover how coronal mass ejections start at the Sun and propagate in interplanetary space. The workshop started with the propositions that coronal mass ejections are fundamental manifestations of rapid large-scale change in the global magnetic structure of the Sun, that CME's are a major driver of coronal evolution, and that they may play a major role in the solar dynamo. Workshop participants developed a mission concept that will lead to a comprehensive characterization of CME disturbances through build-up, initiation, launch, and propagation to Earth. It will also build a clear picture of long-term evolution of the corona. Participants in the workshop recommended that STEREO be a joint mission with the European scientific community and that it consist of four spacecraft: `East' at 1 AU near L4, 60 deg from EArth to detect active regions 5 days before they can be seen by terrestrial telescopes. `West' at L5 views the sources of energetic particle events reaching Earth. `Earth Orbiter' to view the Sun, solar plasma and Earth's magnetosphere, and `North-South' in a 1 AU orbit tilted 30 deg from the ecliptic plane to provide measurements of polar fields and high-latitude activity. All spacecraft will carry solar activity imagers (e.g., EUV telescope and white-light coronagraph) and radio burst detectors to support a tomography program. All will carry sensitive polarimeters that will image CME's from 40 solar radii to 1 AU, and all will carry instruments for situ plasma and energetic particle sampling. East and North-South have solar vector magnetographs. Title: A Possible Mechanism Governing the Production and Evolution of Ellerman Bombs Authors: Diver, Declan A.; Brown, John C.; Rust, David M. Bibcode: 1996SoPh..168..105D Altcode: A hydrodynamic-magnetofluid hybrid analysis of lower chromospheric shear flows in the Sun may explain the occurrence and time development of Ellerman bombs. The analysis assumes that the erupting material forming the bomb is driven initially by the Kelvin-Helmholtz fluid instability applied to the interface between two atmospheric fluid layers, characterized by a steep density change across the boundary and driven by flow fields around sunspots. The ensuing instability eventually evolves into a magnetofluid phenomenon by virtue of the trapping and bending of the interfacial magnetic field, giving rise to a dense globule of material entering, and persisting in, the upper layers and due to Ohmic dissipation having a significantly enhanced temperature compared with ambient material. Title: Escape of magnetic toroids from the Sun Authors: Bieber, John W.; Rust, David M. Bibcode: 1996AIPC..382..430B Altcode: Analysis of heliospheric magnetic fields at 1 AU shows that 1024 Mx of net toroidal flux escapes from the Sun per solar cycle. This rate is compared with the apparent rate of flux emergence at the solar surface, and it is concluded that escaping toroids will remove at least 20% of the emerging flux, and may remove as much as 100% of emerging flux if multiple eruptions occur on the toroids. The data imply that flux escapes the Sun with an efficiency far exceeding Parker's upper limit estimate of 3%. Toroidal flux escape is almost certainly the source of the observed overwinding of the interplanetary magnetic field spiral. Two mechanisms to facilitate net flux escape are discussed: helicity charging to push open the fields and flux transport with reconnection to close them off. We estimate the Sun will shed ~2×1045 Mx2 of magnetic helicity per solar cycle, leading to a mean helicity density of 100 Mx2 cm-3 at 1 AU, which agrees well with observations. Title: Helicity conservation in expanding plasmas: Application to interplanetary magnetic clouds Authors: Kumar, Ashok; Rust, D. M. Bibcode: 1996AIPC..382..434K Altcode: Magnetic energy of a plasma, expanding under the constraint of magnetic helicity conservation, decreases with expansion. Part of this lost magnetic energy might go into heating the plasma. This is used to explain the high temperatures observed in interplanetary magnetic clouds (IMCs). IMCs are modeled as intrinsic-scale flux ropes ejected from the Sun, and it is assumed that their total magnetic helicity, flux and mass are conserved during evolution. The temperature of an expanding cloud goes through a maximum that may be two orders of magnitude higher than the starting value. The model also provides scaling laws for the magnetic field strength, temperature, radial size, density, asymmetry of the magnetic field strength profile, slope of the plasma velocity profile inside clouds, and plasma beta, as functions of distance from the Sun which are then compared with the cloud data obtained between 0.3 and 4 AU from the Sun. Title: Interplanetary magnetic clouds, helicity conservation, and current-core flux-ropes Authors: Kumar, Ashok; Rust, D. M. Bibcode: 1996JGR...10115667K Altcode: A current-core flux-rope model for interplanetary magnetic clouds is presented which explains their average thermodynamic and magnetic properties. It is assumed that during a magnetic cloud's evolution, its total magnetic helicity, flux and mass are conserved and that the dynamics of a cloud is governed by the Lorentz self-force acting on its curved portions. Total magnetic energy and current in a magnetic cloud decrease monotonically as it elongates. Part of this magnetic energy is lost in overcoming solar gravity, part goes into the bulk kinetic energy, and the rest can be assumed to go into heating the plasma inside the cloud. Due to this dissipation of magnetic energy as heat, the temperature of an expanding cloud goes through a maximum before the cloud leaves the corona. The temperature may reach 1.7×106 K. As a cloud expands into interplanetary space, the total plasma beta asymptotically approaches a constant value between 0.39 and 0.52, irrespective of its initial value. Apart from explaining the heating and expansion of magnetic clouds, this model also provides expressions (scaling laws) for the magnetic field strength, temperature, radius, density, asymmetry of the magnetic field strength profile, slope of the plasma velocity profile inside clouds, and plasma beta, as functions of distance from the Sun. These theoretical results are compared with cloud data obtained between 0.3 and 4 AU from the Sun. The comparisons show a good agreement between observation and theory. Title: Evidence for Helically Kinked Magnetic Flux Ropes in Solar Eruptions Authors: Rust, D. M.; Kumar, A. Bibcode: 1996ApJ...464L.199R Altcode: Images of the X-ray corona near the solar disk's center were examined for large, transient brightenings of the type known to be associated with H alpha filament eruptions and coronal mass ejections. Many of the brightenings were sigmoid (S-shaped). The measured ratios of length to width of the sigmoid features are shown to be consistent with ratios predicted by a simple model based on a kinked and twisted magnetic flux rope. Many of the studied sigmoid brightenings evolved into arcades of bright loops. Such arcades are often associated with coronal mass ejections, and it is suggested that the cause of the ejections is an MHD helical kink instability in the H alpha filament/coronal arcade complexes. Reverse-S brightenings outnumbered forward-S brightenings by six to one in the northern hemisphere. Forward-S brightenings were similarly predominant in the south. This hemispherical segregation suggests that the magnetic fields in the transient features are systematically twisted. Globally, the implied distribution of magnetic helicity is similar to the distribution that Martin et al. discovered in quiescent H alpha filaments. Title: The Flare Genesis Experiment Authors: Rust, D. M.; Murphy, G. A.; Strohbehn, K.; Keil, S. L.; Keller, C. U. Bibcode: 1996AAS...188.6705R Altcode: 1996BAAS...28Q.934R The goal of the Flare Genesis Experiment is to make solar observations at the highest practicable resolution in order to improve understanding of the mechanisms involved in many different types of solar activity, particularly flares and solar filament eruptions. Achieving this goal demanded the development of a balloon-borne platform for an 80-cm F/1.5 optical telescope that could maintain 10 arcsec pointing stability. The first flight of the Flare Genesis Experiment took place in January 1996. In the stratosphere, 37 km above Antarctica, for more than 19 days, the Flare Genesis telescope pointed at the Sun with the planned stability. While the primary science objective, to measure the vector magnetic fields using two liquid crystal polarization modulators, was not achieved on this flight, 18,000 continuum images were obtained. They demonstrate that the major engineering challenges for such a flight were overcome. In addition, we developed an image motion compensation system capable of limiting the motion of the Sun's image on the focal plane to less than the system's 0.2 arcsec diffraction limit. Other key elements on board included a lithium-niobate Fabry-Perot etalon filter to provide a tunable 0.016-nm bandpass over a wide wavelength range, a 1538 x 1024- pixel CCD camera and 100 GBytes of on-board storage. We will describe the payload design and how the instruments performed. We will discuss how the constraints of long duration Antarctic ballooning guided the final design and impacted the results. Two more flights are planned before the next solar maximum. Such long-duration balloon flights provide a relatively inexpensive means to observe the Sun at the highest resolution and to develop instrumentation and techniques for future space missions. Title: Origins of Solar Activity Authors: Rust, David M. Bibcode: 1996jhu..rept.....R Altcode: Work under the subject grant began in August 1992, when Mr. J. J. Blanchette began study and data analysis in the area of solar flare research. Mr. Blanchette passed all requirements toward a Ph.D., except for the thesis. Mr. Blanchette worked with the APL Flare Genesis Experiment team to build a balloon-borne solar vector magnetograph. Other work on the magnetograph was partially supported by AFOSR grant F49620-94-1-0079. Mr. Blanchette assisted the Flare Genesis team prepare the telescope and focal plane optical elements for a test flight. He participated in instrument integ ration and in launch preparations for the flight, which took place on January 23, 1994. Mr. Blanchette was awarded a Masters Degree in Astrophysics by the Johns Hopkins University in recognition of his achievements. Mr. Blanchette indicated a desire to suspend work on the Ph.D. degree, and he left the AASERT program on August 31, 1994. Under the guidance of his advisor at JHU/APL, Dr. David M. Rust, Mr. Blanchette gained enough background in solar physics so that he can contribute to observational, analytical, and presentation efforts in solar research. Beginning in August 1995, Mr. Ashok Kumar was supported by the grant. Mr. Kumar demonstrated remarkable theoretical insight into the problems of solar activity. He developed the concept of intrinsic scale magnetic flux ropes in the solar atmosphere and interplanetary space. His model can explain the heating of interplanetary magnetic clouds. Recently, his idea has been extended to explain solar wind heating. If the idea is confirmed by further comparison with observations, it will be a major breakthrough in space physics and it may lead to an explanation for why the solar corona's temperature is over a million degrees. Title: Magnetic Helicity And Its Relationship To The Origins Of Solar Eruptions Authors: Rust, D. M. Bibcode: 1996APS..MAY.L1406R Altcode: From an analysis of solar magnetic fields and of images of the sun's corona, we may be able to test a novel conjecture that was advanced by J. B. Taylor to explain the behavior of plasmas in fusion experiments. The proposed principle of conservation of magnetic helicity may explain many problems of solar activity, e.g., why there are solar eruptions, how the solar wind and corona are heated, and how the solar dynamo functions. Helicity conservation asserts that coiled magnetic fields, once formed, remain coiled, even as they undergo the kind of dramatic transformations seen in solar flares and mass ejections. Helicity conservation may be no less important in understanding and describing space plasmas than conservation of mass and magnetic flux. Helicity conservation has not yet been widely used in solar physics, but recent measurements of helicity on the solar surface and in the solar wind suggest that application of helicity conservation could lay the foundation for major advances in understanding the solar dynamo and magnetic fields throughout the universe. Title: Toroidal Magnetic Fields in the Solar Atmosphere Authors: Rust, D. M. Bibcode: 1996AAS...188.3508R Altcode: 1996BAAS...28..872R The recent discovery that filaments in opposite hemispheres of the Sun tend to exhibit opposite magnetic helicity has prompted a reexamination of the global properties of solar filaments, photospheric magnetic fields, and interplanetary magnetic clouds. It is suggested that observations of East- West asymmetry in high-latitude and mid-latitude photospheric fields can be explained as measurements of the component normal to the surface contaminated by a toroidal component. The toroidal component can also be traced by its effect on chromospheric fine structure and by measurements of the magnetic field direction inside and beneath solar filaments. Since filaments frequently erupt and become interplanetary magnetic clouds, their field direction can be determined by in situ measurements at 1 AU. These measurements are consistent with the field results obtained by traditional remote sensing. The variations in direction of the surface toroidal component over the past three solar cycles are consistent with those expected from naive models. Title: Balloon-Borne Polarimetry Authors: Rust, D. M.; Murphy, G.; Strohbehn, K.; Keller, C. U. Bibcode: 1996SoPh..164..403R Altcode: For about two weeks in 1995, the balloon-borne Flare Genesis Experiment will continuously observe the Sun well above the turbulent, image-blurring layers of the Earth's atmosphere. The polarization-free 80 cm telescope will supply images to a liquid-crystal based vector magnetograph, which will measure magnetic features at a resolution of 0.2 arcsec. An electrically tunable lithium-niobate Fabry-Perot provides a spectral resolution of about 0.015 nm. In a follow-up series of Antarctic balloon flights, the Flare Genesis Experiment (FGE) will provide unprecedented details about sunspots, flares, magnetic elements, filaments, and the quiet solar atmosphere. Title: Helicity Conservation in Expanding Magnetized Plasmas: Flux Ropes in The Solar Wind Authors: Kumar, Ashok; Rust, David M. Bibcode: 1996ASPC...95..315K Altcode: 1996sdit.conf..315K No abstract at ADS Title: Magnetic Helicity, MHD Kink Instabilities and Reconnection in the Corona Authors: Rust, D. M. Bibcode: 1996ASPC..111..353R Altcode: 1997ASPC..111..353R Yohkoh images of the X-ray corona were examined for large transient brightenings near solar disk center. Many of the brightenings were sigmoid (S-shaped). Reverse-S brightenings outnumbered forward-S brightenings by 6 to 1 in the northern hemisphere. Forward-S brightenings were similarly predominant in the south. This hemispherical segregation is consistent with the twisting patterns discovered in Hα filaments, and it suggests that the magnetic fields in the transient brightenings are also twisted. The ratios of width to length of the sigmoid brightenings are those of kinked, twisted flux ropes, and it is suggested that filaments (and coronal mass ejections) erupt because of MHD helical kink instabilities. This would imply that solar eruptions are not accidental events. Rather, they result from helicity-conserving reconnections among fields twisted systematically by helicity-generating forces of the solar dynamo. Interplanetary field measurements show that the total magnetic helicity ejected in a solar cycle is of the same order as the total helicity generated inside the Sun by Coriolis forces. Title: The Escape of Magnetic Flux from the Sun Authors: Bieber, J. W.; Rust, D. M. Bibcode: 1995ApJ...453..911B Altcode: Analysis of heliospheric magnetic fields at 1 AU shows that 1024 Mx of net azimuthal flux is ejected by the Sun per solar cycle. This rate is identified with the rate of toroidal flux generation. It is compared with indicators of flux ejection from the solar atmosphere, including coronal mass ejections (CM Es), filament eruptions, and active region loop expansion. The rate is consistent with estimates of flux escaping in these phenomena. The toroidal flux escape rate is compared with the apparent rate of flux emergence at the solar surface, and it is concluded that escaping toroids will remove at least 20% of the emerging flux, and probably remove 100% of emerging flux, since multiple eruptions occur on the toroids. The data imply that flux escapes the Sun with an efficiency far exceeding Parker's upper limit estimate of 3 %. Toroidal flux escape is almost certainly the source of the observed overwinding of the interplanetary magnetic field spiral. Two mechanisms to facilitate net flux escape are discussed: helicity charging to push open the fields and flux transport with reconnection to close them off. We estimate the Sun will shed ∼2 × 1045 Mx2 of magnetic helicity per solar cycle, leading to a mean helicity density of 100 Mx2 cm-3 at 1 AU, which agrees well with observations. Helicity shedding and flux escape are seen as essential to the cyclic renewal of the solar dynamo. It is argued that because lefthanded and right-handed helical fields accumulate in the northern and southern hemispheres, separately, conservation of magnetic helicity requires that the dynamo-generated fields be expelled. The mean lifetime of magnetic flux on the solar surface is 3-6 months. The mechanisms described here should also enable Sun-like stars to shed dynamo-generated fields. Title: Escape of magnetic toroids from the Sun Authors: Bieber, John W.; Rust, David M. Bibcode: 1995sowi.conf...46B Altcode: Analysis of heliospheric magnetic fields at 1 AU shows that 1024 Mx of net azimuthal flux escapes from the Sun per solar cycle. This rate is consistent with rates derived from other indicators of flux escape, including coronal mass ejections and filament eruptions. The toroidal flux escape rate is compared with the apparent rate of flux emergence at the solar surface, and it is concluded that escaping toroids will remove at least 20% of the emerging flux, and may remove as much as 100% of emerging flux if multiple eruptions occur on the toroids. The data imply that flux escapes the Sun with an efficiency far exceeding Parker's upper limit estimate of 3%. Toroidal flux escape is almost certainly the source of the observed overwinding of the interplanetary magnetic field spiral. Two mechanisms to facilitate net flux escape are discussed: helicity charging to push open the fields and flux transport with reconnection to close them off. We estimate the Sun will shed approximately 2 x 1045 of magnetic helicity per solar cycle, leading to a mean helicity density of 100 Mx2cm-3 at 1 AU, which agrees well with observations. Title: Magnetic clouds, helicity conservation, and intrinsic scale flux ropes Authors: Kumar, A.; Rust, D. M. Bibcode: 1995sowi.conf...46K Altcode: An intrinsic-scale flux-rope model for interplanetary magnetic clouds, incorporating conservation of magnetic helicity, flux and mass is found to adequately explain clouds' average thermodynamic and magnetic properties. In spite their continuous expansion as they balloon into interplanetary space, magnetic clouds maintain high temperatures. This is shown to be due to magnetic energy dissipation. The temperature of an expanding cloud is shown to pass through a maximum above its starting temperature if the initial plasma beta in the cloud is less than 2/3. Excess magnetic pressure inside the cloud is not an important driver of the expansion as it is almost balanced by the tension in the helical field lines. It is conservation of magnetic helicity and flux that requires that clouds expand radially as they move away from the Sun. Comparison with published data shows good agreement between measured cloud properties and theory. Parameters determined from theoretical fits to the data, when extended back to the Sun, are consistent with the origin of interplanetary magnetic clouds in solar filament eruptions. A possible extension of the heating mechanism discussed here to heating of the solar corona is discussed. Title: Evolution of Solar Filaments into Interplanetary Magnetic Clouds: Effect of Magnetic Hellcity Conservation Authors: Kumar, A.; Rust, D. M. Bibcode: 1995SPD....26..305K Altcode: 1995BAAS...27..953K No abstract at ADS Title: Helicity charging and eruption of magnetic flux from the sun Authors: Rust, D. M.; Kumar, A. Bibcode: 1994ESASP.373...39R Altcode: 1994soho....3...39R No abstract at ADS Title: Helical Magnetic Fields in Filaments Authors: Rust, D. M.; Kumar, A. Bibcode: 1994SoPh..155...69R Altcode: For both even and odd-numbered solar cycles, right-hand heliform filaments predominate at middle and high latitudes in the northern hemisphere while left-handed ones predominate in the south. This recent discovery has prompted a re-examination of past measurements of magnetic fields in prominences. This re-examination indicates that Rust (1967), in his interpretation of solar cycle 20 measurements in terms of the Kippenhahn-Schlüter model, and Leroy, Bommier, and Sahal-Bréchot (1984), in their interpretation of solar cycle 21 measurements in terms of the Kuperus-Raadu model were both misled by the global pattern of helicity. While the original magnetic field measurements are consistent with the new results about heliform magnetic fields in filaments, neither of the well-known classes of two-dimensional models can produce both the proper axial field direction and the observed pattern of helicity. A global, subsurface velocity pattern that would twist the fields before emergence as filaments seems to be required. In this paper a twisted-flux-rope model consistent with the new understanding of filament fields is presented. The model is based on a constant-α solution of the magnetostatic equations, where electric current densityj(r) =αB(r). The model filament has dimensions in general agreement with observations. It is shown to be stable if the length is less than 140 000 km to 1,400 000 km, depending on the value ofα. The model also provides a new explanation of eruptive prominences and for the origin of the entrained material. Title: Preflare State Authors: Rust, David M.; Sakurai, Takashi; Gaizauskas, Victor; Hofmann, Axel; Martin, Sara F.; Priest, Eric R.; Wang, Jing-Xiu Bibcode: 1994SoPh..153....1R Altcode: Discussion on the preflare state held at the Ottawa Flares 22 Workshop focused on the interpretation of solar magnetograms and of Hα filament activity. Magnetograms from several observatories provided evidence of significant build up of electric currents in flaring regions. Images of X-ray emitting structures provided a clear example of magnetic relaxation in the course of a flare. Emerging and cancelling magnetic fields appear to be important for triggering flares and for the formation of filaments, which are associated with eruptive flares. Filaments may become unstable by the build up of electric current helicity. Examples of heliform eruptive filaments were presented at the Workshop. Theoretical models linking filaments and flares are briefly reviewed. Title: Spawning and Shedding Helical Magnetic Fields in the Solar Atmosphere Authors: Rust, D. M. Bibcode: 1994GeoRL..21..241R Altcode: Measurements of the helical fields in interplanetary magnetic clouds have corroborated recent evidence that the magnetic fields in solar filaments in the northern and southern hemispheres of the Sun are preferentially left-handed and right-handed heliform, respectively. In 13 cases out of 16, the chirality of magnetic clouds passing Earth about 4 days after a filament eruption or an eruptive solar flare corresponded to the predominant chirality in the hemisphere originating the solar event. Active regions and sunspots also indicate that helicity is segregated by hemisphere. Torque due to an equatorial jet stream beneath the photosphere may twist the fields. Title: The flare genesis project Authors: Rust, D. M. Bibcode: 1994AdSpR..14b..89R Altcode: 1994AdSpR..14...89R The feasibility of a balloon-borne experiment to understand how the magnetic fields at the solar surface emerge, coalesce, unravel and erupt in solar flares was studied. A key component of the Flare Genesis instrument will be a solar telescope with an 0.8-meter-diameter lightweight mirror. Effects of pendulation and jitter, gravity and temperature on the images formed by the telescope were studied to determine whether it will maintain the desired resolution of ~0.2 sec of arc at float altitude. The principal conclusions of the study are that (1)sufficient image stability can be maintained at the focal plane; (2) polarization sensitivity of 2 × 10-4 is achievable; and (3) the data system can store ~ 2000 magnetograms on-board in the course of a 10-to-14-day Antarctic flight. Title: Active Region Development: Results from the JHU/APL Vector Magnetograph Authors: Rust, D. M.; Murphy, G.; Balasubramaniam, K. S.; Gullixson, C. A.; Henry, T.; Coulter, R. L.; Keil, S. L. Bibcode: 1994ASPC...68..263R Altcode: 1994sare.conf..263R No abstract at ADS Title: Are Flares Necessary? Authors: Rust, D. M. Bibcode: 1994ASPC...68..335R Altcode: 1994sare.conf..335R No abstract at ADS Title: A Correlation Between Sunspot Whirls and Filament Type Authors: Rust, D. M.; Martin, S. F. Bibcode: 1994ASPC...68..337R Altcode: 1994sare.conf..337R No abstract at ADS Title: A Biologically-Inspired Image Position Sensor Authors: Strohbehm, K.; Rust, D.; Andreou, A.; Jenkins, R. Bibcode: 1993rtpf.conf...32S Altcode: No abstract at ADS Title: Continued development of an ultra-narrow bandpass filter for solar research Authors: Rust, David M. Bibcode: 1993jhu..reptS....R Altcode: The objective of work under this task was to develop ultranarrow optical bandpass filters and related technology necessary for construction of a compact solar telescope capable of operating unattended in space. The scientific problems to which such a telescope could be applied include solar seismology, solar activity monitoring, solar irradiance variations, solar magnetic field evolution, and the location of targets for narrow-field specialized telescopes. We have demonstrated a Y-cut lithium-niobate Fabry-Perot etalon. This filter will be used on the Flare Genesis Experiment. We also obtained solar images with a Z-cut etalon. The technical report on etalon filters is attached to this final report. We believe that work under this grant will lead to the commercial availability of a universal optical filter with approximately 0.1 A bandwidth. Progress was made toward making a suitable 1-2 A tunable blocker filter, but it now appears that the best approach is to make a double-cavity etalon that will not require such a narrow blocker. Broader band blockers are commercially available. Title: Origins of solar activity. First year report, AASERT grant Authors: Rust, David M. Bibcode: 1993jhu..reptR....R Altcode: This report describes the first year of training and progress of Mr. J.J. Blanchette toward a Ph.D. in Physics, with specialization in Solar Physics. Mr. Blanchette has met all academic requirements in order to proceed with his thesis research. He is a full-time graduate research fellow, and he has gained a good background in solar activity research. He has taken on the task of implementing the focal-plane functions of the Target Selector Telescope of the Flare Genesis Experiment, a balloon-borne telescope for solar activity research. During the report period, Mr. Blanchette presented a description of his work on solar active region NOAA 7260 at the 24th meeting of the Solar Physics Division of the AAS. Title: Vector Magnetography of a Large Sunspot Authors: Rust, D. M.; Murphy, G. A.; Blanchette, J. J.; Cauzzi, C.; Keil, S.; Balasubramaniam, K. S. Bibcode: 1993BAAS...25.1205R Altcode: No abstract at ADS Title: It's the Helicity, Stupid! Authors: Rust, D. M. Bibcode: 1993BAAS...25.1225R Altcode: No abstract at ADS Title: Solar vector magnetic field research Authors: Rust, David M. Bibcode: 1993jhu..reptQ....R Altcode: The objective of the project was to measure the magnetic fields in solar active regions, develop methods for predicting solar flares on the basis of the measurements, and improve the instrumentation for solar magnetic field measurements. In cooperation with the staff at the Solar Branch of the USAF Phillips Laboratory, field measurements were made almost daily during the grant period. The principal result of analyses carried out so far is that so-called sheared magnetic fields are neither necessary nor sufficient for solar flaring. The crucial element seems to be emerging magnetic flux and local development of shear in the hour before flare onset. A need for greatly improved instrumentation was identified. A new vector magnetograph was designed for operation above the image-degrading layers of the atmosphere. Fourteen technical publications and presentations appeared under grant sponsorship. Title: Origins and effects of solar flares Authors: Rust, D. M. Bibcode: 1993beps.proc...73R Altcode: During the 1989 - 1991 peak of solar activity, geomagnetic storms from interplanetary shocks caused a massive failure in the Canadian power grid, minor failures in other power eqipment, and many communications disruptions and satellite malfunctions. The proton storms would have been lethal for unshielded space travellers. Had the power managers been given a credible, timely forecast of the solar storm, they could have protected their generating equipment and the grid. They do not keep protective circuits in place full-time because that reduces efficiency and increases the cost of power distribution. Nor will astronauts on the moon or in deep space confine themselves full-time to thick-walled, radiation-resistant closets. To enable manned deep space exploration we have to find a way to determine what happens in solar flares. Only this will improve the forecasts. Expensive and restrictive protective measures would then have to be applied only when a major flare is clearly imminent. There is no generally accepted flare theory or description of the pre-flare state or of the instabilities. The Solar Maximum Mission (SMM) cleared up many questions about electromagnetic flare emissions and the structure of the flaring atmosphere, but the dynamic of the magnetic fields is still a mystery. Title: Plasma, magnetic, and electromagnetic measurements at nonmagnetic bodies. Authors: Rust, D. M.; Kumar, A.; Thompson, K. E. Bibcode: 1993atpi.workR..20R Altcode: A new type of image detector will simultaneously analyze the polarization of light at all picture elements in a scene. The integrated Dual Imaging Detector (IDID) consists of a polarizing beam splitter bonded to a charge-coupled device (CCD), with signal-analysis circuitry and analog-to-digital converters, all integrated on a silicon chip. The polarizing beam splitter can be either a Ronchi ruling, or an array of cylindrical lenslets, bonded to a birefringent wafer. The wafer, in turn, is bonded to the CCD so that light in the two orthogonal planes of polarization falls on adjacent pairs of pixels. The use of a high-index birefringent material, e.g., rutile, allows the IDID to operate at f-numbers as high as f/3.5. Other aspects of the detector are discussed. Title: Solar flare prediction needed Authors: Rust, D. Bibcode: 1993EOSTr..74..553R Altcode: “From veils of haze now comes the gleam, Here to a tender scarf it tapers, Here gushes forth a vivid stream; Then threads of light in a network surging Their silver veins through valleys run, Till, gathered by the hills converging, The sundered filaments are one.” Title: Solar flares: An overview Authors: Rust, David M. Bibcode: 1992AdSpR..12b.289R Altcode: 1992AdSpR..12..289R This is a survey of solar phenomena and physical models that may be useful for improving forecasts of solar flares and proton storms in interplanetary space. Knowledge of the physical processes that accelerate protons has advanced because of gamma-ray and X-ray observations from the Solar Maximum Mission telescopes. Protons are accelerated at the onset of flares, but the duration of any subsequent proton storm at 1 AU depends on the structure of the interplanetary fields. X-ray images of the solar corona show possible fast proton escape paths. Magnetographs and high-resolution visible-band images show the magnetic field structure near the acceleration region and the heating effects of sunward-directed protons. Preflare magnetic field growth and shear may be the most important clues to the physical processes that generate high energy solar particles. Any dramatic improvement in flare forecasts will require high resolution solar telescopes in space. Several possibilities for improvements in the art of flare forecasting are presented, among them: the use of acoustic tomography to probe for subsurface magnetic fields; a satellite-borne solar magnetograph; and an X-ray telescope to monitor the corona for eruptions. Title: A Search for Polarization in Ellerman Bombs Authors: Rust, David M.; Keil, Steven L. Bibcode: 1992SoPh..140...55R Altcode: Ellerman bombs, also called `moustaches', are transient brightenings at tiny (< 1 arc sec) points in the lower chromosphere whose spectra are characterized by elongated emission wings on the hydrogen Balmer lines. Babin and Koval recently found linear polarization as high as 20% in bombs, but no physical process that could produce such a high degree of polarization was suggested. A new observational study of polarization in Ellerman bombs is reported here. Images of 32 bombs were obtained with a digital video system viewing the Sun through a 6 Å filter at the Sacramento Peak Vacuum Tower Telescope. A novel polarizing beamsplitter divided each image into two interleaved polarized components which passed simultaneously through a single set of optics and were separated only during data analysis. The sensitivity threshold of the measurements was ∼ 1%. In 4 cases out of 32, linear polarization above 2% was detected. The higher incidence of > 2% polarization reported by Babin and Koval is not confirmed. Title: Variation of the Vector Magnetic Field in an Eruptive Flare Authors: Rust, D. M.; Cauzzi, G. Bibcode: 1992LNP...399...46R Altcode: 1992esf..coll...46R; 1992IAUCo.133...46R Observations of a 3B, M6 flare on April 2, 1991 appear to confirm earlier evidence that eruptive flares are triggered by measurable magnetic field changes. In the eight hours before the flare, the shear in the magnetic fields increased. The development that likely triggered the flare was the emergence into the active region and rapid proper motion of new flux. One of the small spots marking the negative magnetic leg of the new flux pushed into an established positive field at 0.2 km/s. Data from the JHU/APL vector magnetograph show that this motion led to the development of a sheared field. The flare started near the newly-sheared fields and spread to engulf most of the spot region. A magnetogram taken 45 min after flare onset shows possible relaxation of the sheared fields. Title: A biologically-inspired VSLI sunspot tracker. Authors: Rust, D. M.; Strohbehn, K. Bibcode: 1992BAAS...24.1075R Altcode: No abstract at ADS Title: Solar vector magnetic field research Authors: Rust, David M. Bibcode: 1991jhu..rept.....R Altcode: Observations have been made before and after a large solar flare. Magnetic features were observed that could be used to predict flares if they are a regular feature of such events. The observations were among the first to show the development of shear within one hour of flare onset. Observations of linear polarization have been made of transient brightenings at small points in the lower chromosphere. The association between these flare-like events and magnetic fields has been studied. A feasibility study has been made of observing the sun with a balloon-borne vector magnetograph. The APL vector magnetograph developed under an OSR URI is operational. Title: New instruments for solar research. Authors: Rust, D. M.; O'Byrne, J. W.; Sterner, R. E., II Bibcode: 1991JHATD..11...77R Altcode: New instruments have been installed at observatories in New Mexico and California for measuring solar magnetic fields and surface velocities. The magnetic fields provide the enrgy for all eruptive and accelerative processes on the Sun, and the surface velocities reveal the dynamics of the solar interior. The new instruments incorporate several technical innovations, including a lithium niobate filter for high spectral resolution. With this filter, circular and linear polarization and Doppler shifts are measured in solar spectral lines to yield estimates of the magnetic field vector in active sunspot regions. Title: A New Method for Calibrating Vector Magnetograms Authors: Cauzzi, G.; Rust, D. M.; O'Byrne, J. W. Bibcode: 1991BAAS...23R1054C Altcode: No abstract at ADS Title: A Search for Polarization in Ellerman Bombs Authors: Rust, D. M.; Keil, S. L. Bibcode: 1991BAAS...23R1029R Altcode: No abstract at ADS Title: Vector magnetography. Authors: Rust, D. M.; O'Byrne, J. W. Bibcode: 1991sopo.work...74R Altcode: Development of the JHU/APL vector magnetograph (VMG) at the National Solar Observatory gives insight into the advantages and drawbacks of trying to infer solar active region magnetic fields from filtergram measurements with 0.8 - 3.0 arcsec spatial resolution, several-minute temporal resolution and 120 - 180 mÅ spectral resolution. The use of a narrow-band filter and the weak-field approximation (WFA) of the Stokes profiles gives good temporal and spatial data on magnetic fields, but sacrifices information on the thermodynamic parameters. A model of the VMG's response in the wings of the Ca I line at 6122 Å shows that the range of validity of the WFA can be extended to 4000 G. It also shows that the response of the VMG is insensitive to the Doppler shifts due to the motions (<1 km/s) exhibited by most solar features. The role of vector magnetography with a narrow-band filter in flare research is emphasized and several examples of early observations with the VMG are given. Title: The Earth's climate and variability of the Sun over recent millennia: Geophysical, astronomical and archaeological aspects Authors: Rust, D. M. Bibcode: 1991EOSTr..72..157R Altcode: At the outer limits of the range of topics covered in these proceedings from a joint meeting of the British Royal Society and the French Academie des Sciences lie speculation and inaccessible places and times. The causes of the Sun's variability are hidden beneath its surface, and we can only speculate about whether solar magnetism, which provides the energy for the variations, is generated just below the surface or is a remnant of an ancient magnetism trapped in the core. An equally distant and inaccessible sphere is the gassy envelope around the prehistoric Earth where changes in climate presumably drove early man to alter his habits and homes. But as P. I. Kuniholm writes in this volume, climate change has often been appealed to in accounting for phenomena that cannot otherwise be accounted for. Archaeologists never imagined that physicists would try to reconstruct the Sun's past from such speculations. Between the two extremes of ignorance, however, a solid foundation is being built for a scientific account of the Sun's role in climate change. Title: Sociology of the SMY Authors: Rust, David M. Bibcode: 1991AdSpR..11e.123R Altcode: 1991AdSpR..11..123R No abstract at ADS Title: Etalon filters. Authors: Rust, D. M. Bibcode: 1991LFTR...50.....R Altcode: This article begins with a brief introduction to Fabry-Perot interferometers and goes on to describe the use of Fabry-Perot etalons as narrow-band filters. Properties of solid etalons with fused silica, mica and lithium niobate substrates are discussed and compared with those of the Lyot birefringent filter. Examples of applications of etalon filters in helioseismology, high-resolution imaging and vector magnetography are given. It is concluded that lithium niobate etalons can meet the LEST requirements for a universally tunable narrow-band filter. Title: New instruments for solar research Authors: Rust, David M.; O'Byrne, John W.; Sterner, Raymond E., II Bibcode: 1990JHATD..11...77R Altcode: In fulfilment of its goal to develop early detection and warning of emerging solar magnetic fields, the Center for Applied Solar Physics (CASP) has designed and constructed a solar vector magnetograph (VMG) that will provide unique data on the sunspot regions where flares originate. The instrument is reportedly beginning to approach its goals of measuring all three components of the solar magnetic field with a sensitivity of 50 to 100 G and a spatial resolution on the sun of about 700 km (1 arcsec). Importance of new high-resolution capabilities is stressed and the interpretation of VMG measurements is discussed. The performance of the solar VMG, installed in a 6-m dome at the National Solar Observatory at Sacramento Peak in Sunspot, New Mexico, and its construction and environment are described; particular attention is given to the use and function of the filters. Initial results are examined, including a description and analysis of a magnetogram obtained after installation of an improved blocking filter. Title: Activities and accomplishments of the Center for Applied Solar Physics, 1987 - 1990 Authors: Rust, David M. Bibcode: 1990jhu..reptQ....R Altcode: New instruments have been installed at observatories in New Mexico and California for measuring solar magnetic fields and surface velocities. The magnetic fields provide the energy for all eruptive and accelerative processes on the Sun, and the surface velocities reveal the dynamics of the solar interior. Early detection of emerging magnetic fields may give several hours' warning of impending solar flares and interplanetary shocks. The new instruments incorporate several technical innovations, including lithium niobate filter for high spectral resolution. With this filter, circular and linear polarization and Doppler shifts are measured in solar spectral lines to yield estimates of the magnetic field vector in active sunspot regions. A program of daily measurements is planned for study of the current peak in the 11-year solar cycle. Title: Emerging Flux Model of Solar Filament Formation Authors: Cheng, A. F.; Rust, D. M. Bibcode: 1990BAAS...22..900C Altcode: No abstract at ADS Title: Vector Magnetic Field Observations in Solar Active Regions Authors: Rust, D. M.; O'Byrne, J. W. Bibcode: 1990BAAS...22..808R Altcode: No abstract at ADS Title: Doppler-shifted Emission from Helium Ions Accelerated in Solar Flares Authors: Peter, Th.; Ragozin, E. N.; Urnov, A. M.; Uskov, D. B.; Rust, D. M. Bibcode: 1990ApJ...351..317P Altcode: This paper concerns the Doppler-shifted Ly-alpha radiation emitted by He II (304 A) in ion beams accelerated in solar flares downward from the solar corona into the chromosphere, where they are slowed down and finally stopped. It is found that the radiation from He II ions with E(0) greater than or equal to 150 keV/amu initially at the top of the atmosphere would lie typically one order of magnitude above the background. The radiation from He ions moving initially with E(0) greater than or equal to 400 keV/amu should be observable as long as the beam is driven by the flare. Radiative electron capture provides an effective cooling mechanism. Title: Recent Progress with the JHU/APL Solar Vector Magnetograph Authors: O'Byrne, J. W.; Rust, D. M.; Sterner, R. E. Bibcode: 1990BAAS...22..816O Altcode: No abstract at ADS Title: A low polarization solar vector magnetograph. Authors: Rust, D. M.; O'Byrne, J. W. Bibcode: 1990SPIE.1166..368R Altcode: A new instrument for measuring magnetic fields in the sun's atmosphere has recently been installed at the National Solar Observatory in New Mexico. At each point within the field of view, it detects both linear and circular polarization in a spectral line from which the solar magnetic field strength and direction may be deduced. The vector magnetograph has low instrumental polarization and low circular-to-linear crosstalk. Spectral resolution is provided by a solid lithium-niobate Fabry-Perot filter which may be electrically tuned to scan any solar spectral line. The instrument is capable of 0.7″spatial resolution and 0.015 nm spectral resolution. The instrument and its background are described, together with some test results. Title: Performance of the JHU/APL Solar Vector Magnetograph Authors: Rust, D. M.; O'Byrne, J. W.; Sterner, R. E. Bibcode: 1989BAAS...21.1186R Altcode: No abstract at ADS Title: High resolution vector magnetograph Authors: Rust, D. M.; O'Byrne, J. Bibcode: 1989hsrs.conf..378R Altcode: No abstract at ADS Title: The JHU/APL Vector Magnetograph Authors: O'Byrne, J. W.; Rust, D. M.; Harris, T. Bibcode: 1989BAAS...21..849O Altcode: No abstract at ADS Title: Review of Recent Solar Magnetic Field Observations Authors: Rust, D. M. Bibcode: 1989BAAS...21Q.854R Altcode: No abstract at ADS Title: Chromospheric explosions. Authors: Doschek, G. A.; Antiochos, S. K.; Antonucci, E.; Cheng, C. -C.; Culhane, J. L.; Fisher, G. H.; Jordan, C.; Leibacher, J. W.; MacNiece, P.; McWhirter, R. W. P.; Moore, R. L.; Rabin, D. M.; Rust, D. M.; Shine, R. A. Bibcode: 1989epos.conf..303D Altcode: The work of this team addressed the question of the response and relationship of the flare chromosphere and transition region to the hot coronal loops that reach temperatures of about 107K and higher. Flare related phenomena such as surges and sprays were also discussed. The team members debate three main topics: 1) whether the blue-shifted components of X-ray spectral lines are signatures of "chromospheric evaporation"; 2) whether the excess line broadening of UV and X-ray lines is accounted for by "convective velocity distribution" in evaporation; and 3) whether most chromospheric heating is driven by electron beams. These debates illustrated the strengths and weaknesses of our current observations and theories. Title: An optical instrument for measuring solar magnetism. Authors: Rust, David M.; O'Byrne, John W.; Harris, Terry J. Bibcode: 1988JHATD...9..349R Altcode: A new instrument for measuring solar magnetic fields, the solar vector magnetograph, is under construction at APL's Center for Applied Solar Physics. Its key attributes are high spatial resolution, high optical throughput, fine spectral selectivity, and ultra-low instrumental polarization. Title: The stable solar analyzer. Authors: Rust, D. M.; Appourchaux, T. Bibcode: 1988ESASP.286..227R Altcode: 1988ssls.rept..227R This paper presents a progress report on the development of an instrument with very high (1:1010) wavelength stability designed to measure solar surface velocities and magnetic fields. The instrument determines Doppler and Zeeman shifts in solar spectral lines by a 6-point weighted average. It is built around an electrically tunable solid lithium-niobate Fabry-Perot etalon that is stabilized against a diode laser which itself is locked to a resonance line of cesium 133. Key features are the unique etalon, which acts as a wide-angle 0.017-nm solar filter, the camera with a specially stabilized shutter, and the instrument control and data collection system. Use of the instrument in helioseismological research is emphasized. Title: Solar vector magnetograph for Max 1991 programs Authors: Rust, D. M.; Obyrne, J. W.; Harris, T. J. Bibcode: 1988fnsm.work..113R Altcode: An instrument for measuring solar magnetic fields is under construction. Key requirements for any solar vector magnetograph are high spatial resolution, high optical throughput, fine spectral selectivity, and ultralow instrumental polarization. An available 25 cm Cassegrain telescope will provide 0.5 arcsec spatial resolution. Spectral selection will be accomplished with a 150 mA filter based on electrically tunable solid Fabry-Perot etalon. Filter and polarization analyzer design concepts for the magnetograph are described in detail. The instrument will be tested at JHU/APL, and then moved to the National Solar Observatory in late 1988. It will be available to support the Max 1991 program. Title: Solar Vector Magnetograph for Max'91 Programs Authors: Rust, D. M.; O'Byrne, J. W.; Harris, T. J. Bibcode: 1988BAAS...20..912R Altcode: No abstract at ADS Title: Performance of a Stabilized Fabry-Perot Solar Analyzer Authors: Rust, D. M.; Appourchaux, T.; Hill, F. Bibcode: 1988IAUS..123..475R Altcode: A unique solar lineshift analyzer described by Rust, Burton and Leistner (1986) has been used to study solar oscillations. Operation of this "Stabilized Solar Analyzer" depends on the electro-optic effect in crystalline lithium niobate, the substrate of the solid Fabry-Perot etalon. For 10 days in February, 1986, at the Vacuum Tower Telescope of the Sacramento Peak Observatory, the authors obtained full-disk observations of the solar oscillations. Title: Rotation in the Solar Convection Zone Inferred from Fabry-Perot Observations of the 5-MIN Oscillations Authors: Hill, F.; Rust, D. M.; Appourchaux, T. Bibcode: 1988IAUS..123...49H Altcode: Full disk observations of the 5-min solar oscillations have been obtained with a lithium niobate Fabry-Perot filter. The equatorial solar rotation rate as a function of depth has been inferred from the sectoral modes of oscillation using the Backus-Gilbert optimal averaging inversion method. The results show a rotation rate that slowly decreases over the depths of 15 to 56 Mm below the photosphere. The results are in agreement with the previous Duvall-Harvey observations. Title: Highlights of the Study of Energy Release in Flares Authors: Rust, D. M.; Batchelor, D. A. Bibcode: 1987SoPh..114..399R Altcode: From February 26 to March 1, 1979, thirty-two solar flare investigators attended a workshop at Cambridge, Mass., to define objectives and devise a scientific program for the Study of Energy Release in Flares (SERF) during the coming solar maximum. Herein we review some major results of the ensuing five-year effort to observe and understand the flare energy release process and its effects (energetic particle production, coronal and chromospheric heating, electromagnetic radiations, and mass motions and ejections). The central issue — what processes store and release the energy liberated in flares — remains unresolved except in the most general terms (e.g., it is generally agreed that the energy is stored in sheared or stressed magnetic fields and released by field annihilation during some MHD instability). Resolving that issue s still one of the most important goals in solar physics, but the advances during the SERF program have brought it closer. Title: Electrooptic Fabry-Perot filter: development for the study of solar oscillations Authors: Burton, C. H.; Leistner, A. J.; Rust, D. M. Bibcode: 1987ApOpt..26.2637B Altcode: No abstract at ADS Title: Observations of Solar Oscillations with a Fabry-Perot Etalon Authors: Rust, D. M.; Hill, F.; Appourchaux, T. Bibcode: 1987BAAS...19R.933R Altcode: No abstract at ADS Title: X-Ray Image of Solar Flares from the Solar Maximum Mission Authors: Batchelor, D. A.; Rust, D. M. Bibcode: 1987sman.work..289B Altcode: Sequences of X-ray images of solar flares, obtained with the Hard X-ray Imaging Spectrometer (HXIS) on the SMM spacecraft, reveal interesting dynamical phenomena. The authors present here a preliminary analysis of the events as a group, and discuss some new aspects of the well-studied 1980 May 21 flare and a 1980 November 6 flare. Title: The Sun's spots and flares. Authors: Rust, David M. Bibcode: 1987swe..conf....2R Altcode: Recently, a NASA satellite has not only gathered much new information about sunspots and flares, but it also has had the unique experience of being repaired in outer space by astronauts. What has been accomplished with the telescopes of the satellite observatory, and what do solar physicists hope to achieve with it in the near future?Contents: Introduction. The repair mission. Research highlights. Gamma rays. X rays. Ultraviolet rays. Mass ejection. The solar constant. Title: Development of ultrastable filters and lasers for solar seismology. Authors: Rust, D. M.; Kunski, R.; Cohn, R. F. Bibcode: 1986JHATD...7..209R Altcode: The Stable Solar Analyzer is a recently developed instrument for the measurement of solar magnetic fields and surface velocities that is being employed at the U.S. National Solar Observatory to study the subsurface convection cells of the sun and the structure of surface and subsurface magnetic fields. The Analyzer is expected to ultimately be flown aboard such spacecraft as the ESA/NASA Solar and Heliospheric Observatory. This instrument is based on a crystalline lithium niobate Fabry-Perot filter that is used in conjunction with a stabilized laser that furnishes an absolute wavelength reference; this laser Fabry-Perot combination has achieved wavelength stabilities of the order of 2 parts in 10 to the 10th, over a six-hour interval. Title: A tunable, solid, Fabry-Perot etalon for solar seismology. Authors: Rust, David M.; Burton, Clive H.; Leistner, Achim J. Bibcode: 1986SPIE..627...39R Altcode: A solid etalon has been designed and fabricated from a 50-mm diameter wafer of optical-quality lithium niobate. The finished etalon has a free spectral range of 0.325 nm at 588 nm. The parallel faces are coated with silver, and the central 15-mm aperture of the etalon has a finesse of 18.6. The reflective faces double as electrodes, and application of voltage will shift the passband. This feature was used in a servo circuit to stabilize the passband against temperature and tilt-induced drifts to better than three parts in one billion. Operated in the stabilized mode for day-long sessions, this filter alternately samples the wings of a narrow atomic absorption line in the solar spectrum and produces a signal proportional to velocity on the solar disk. The Fourier transform of this signal yields information on acoustic waves in the solar interior. Title: Chromospheric explosions. Authors: Doschek, G. A.; Antiochos, S. K.; Antonucci, E.; Cheng, C. -C.; Culhane, J. L.; Fisher, G. H.; Jordan, C.; Leibacher, J. W.; MacNiece, P.; McWhirter, R. W. P.; Moore, R. L.; Rabin, D. M.; Rust, D. M.; Shine, R. A. Bibcode: 1986NASCP2439....4D Altcode: The work of this team addressed the question of the response and relationship of the flare chromosphere and transition region to the hot coronal loops that reach temperatures of about 107K and higher. Flare related phenomena such as surges and sprays are also discussed. The team members debated three main topics: 1. whether the blue-shifted components of X-ray spectral lines are signatures of "chromospheric evaporation"; 2. whether the excess line broadening of UV and X-ray lines is accounted for by "convective velocity distribution" in evaporation; and 3. whether most chromospheric heating is driven by electron beams. Title: Flare surge event of 7 November 1980. Authors: Sotirovski, P.; Simon, G.; Rust, D. M. Bibcode: 1986lasf.conf...71S Altcode: No abstract at ADS Title: White light flares and atmospheric modeling (Working Group report). Authors: Machado, M. E.; Avrett, E. H.; Falciani, R.; Fang, C.; Gesztelyi, L.; Henoux, J. -C.; Hiei, E.; Neidig, D. F.; Rust, D. M.; Sotirovski, P.; Svestka, Z.; Zirin, H. Bibcode: 1986lasf.conf..483M Altcode: The authors give a short summary of their discussions, and a set of recommendations which may help in the study of white light flare emission processes. Title: Influence of Solar Flares on the X-Ray Corona Authors: Rust, D. M.; Batchelor, D. A. Bibcode: 1986ASSL..123...93R Altcode: 1986shtd.symp...93R Sequences of X-ray images of solar flares, obtained with the Hard X-ray Imaging Spectrometer (HXIS) on the SMM spacecraft, reveal many dynamical phenomena. Movies of 20 flares recorded with 6-sec time resolution were examined. The authors present a preliminary analysis of the events as a group, and discuss some new aspects of the well-studied 1980 May 21 flare and a 1980 November 6 flare. Title: On the causes of white-light flares. Authors: Rust, David M. Bibcode: 1986lasf.conf..282R Altcode: 1986lasf.symp..282R White-light flares generally exhibit two distinct phases, the impulsive and the main phase. Spectral characteristics of the optical and X-ray emissions associated with these two phases are reviewed. Events that show no Balmer discontinuity or only a small one during the main phase are examined in detail. It is concluded that intense 1 - 10 Å X-ray emission may heat the upper photosphere sufficiently to produce H- continuum emission. The effects of a high-temperature, high-pressure coronal flare plasma upon the chromosphere and photosphere are examined with the aid of recent model atmosphere calculations. It is concluded that white-light flares lacking Balmer discontinuities are due to the extreme narrowing of the chromosphere under the high-temperature and high-pressure conditions prevailing in flares rated M5 and above on the GOES X-ray scale. Title: Evidence for and against electron beams in solar flares. Authors: Brown, J. C.; Rust, D. Bibcode: 1986lasf.conf..431B Altcode: 1986lasf.symp..431B The theoretical and observational evidence for the interpretation of hard X-ray bursts as non-thermal bremsstrahlung from a collision-dominated thick target electron beam is reviewed critically as on this interpretation rests the extensive work being done on beam heating of solar flares. It is concluded that the thick target model cannot be rejected but that it poses a number of problems too serious to be lightly dismissed. Title: Multiwavelength Analysis of a Well Observed Flare from Solar Maximum Mission Authors: MacNeice, P.; Pallavicini, R.; Mason, H. E.; Simnett, G. M.; Antonucci, E.; Shine, R. A.; Rust, D. M.; Jordan, C.; Dennis, B. R. Bibcode: 1985SoPh...99..167M Altcode: We describe and analyse observations of an M1.4 flare which began at 17: 00 UT on 12 November, 1980. Ground based Hα and magnetogram data have been combined with EUV, soft and hard X-ray observations made with instruments on-board the Solar Maximum Mission (SMM) satellite. The preflare phase was marked by a gradual brightening of the flare site in Ov and the disappearance of an Hα filament. Filament ejecta were seen in Ov moving southward at a speed of about 60 km s−1, before the impulsive phase. The flare loop footpoints brightened in Hα and the CaXIX resonance line broadened dramatically 2 min before the impulsive phase. Non-thermal hard X-ray emission was detected from the loop footpoints during the impulsive phase while during the same period blue-shifts corresponding to upflows of 200-250 km s−1 were seen in Ca XIX. Evidence was found for energy deposition in both the chromosphere and corona at a number of stages during the flare. We consider two widely studied mechanisms for the production of the high temperature soft X-ray flare plasma in the corona, i.e. chromospheric evaporation, and a model in which the heating and transfer of material occurs between flux tubes during reconnection. Title: Analysis of a White Light Flare Spectrum Authors: Boyer, R.; Sotirovsky, P.; Machado, M. E.; Rust, D. M. Bibcode: 1985SoPh...98..255B Altcode: The continuum emission of an X1 flare on 26 March, 1970 observed close to the solar limb (N 05 E 64) was analyzed by a photometric determination of the contrast ΔI(λ)/I0(λ) in the wavelength range 3558-5920 Å. Two possible mechanisms for the emission were investigated, namely hydrogen Paschen and H continua. We show the unlikeness of the Paschen possibility and derive strong constraints on the temperature structure and energy deposition mechanism imposed by the H continuum process. Title: A Fabry-Perot Etalon for Differential Spectral Imaging Authors: Rust, D. M.; Burton, C.; Abell, R. Bibcode: 1985BAAS...17..642R Altcode: No abstract at ADS Title: Survey of Solar X-Ray Flare Dynamics Authors: Batchelor, D. A.; Rust, D. M. Bibcode: 1985BAAS...17..628B Altcode: No abstract at ADS Title: Some design considerations for a satellite-borne magnetograph. Authors: Rust, D. M. Bibcode: 1985NASCP2374..141R Altcode: This paper reviews the design criteria for a compact magnetograph that can monitor solar magnetic fields from a free-flying satellite for 5 - 10 years. Title: Observational evidence for thermal wave fronts in solar flares Authors: Rust, D. M.; Simnett, G. M.; Smith, D. F. Bibcode: 1985ApJ...288..401R Altcode: Images in 3.5-30 keV X-rays obtained during the first few minutes of seven solar flares show rapid motions. In each case X-ray emission first appeared at one end of a magnetic field structure, and then propagated along the field at a velocity between 800 and 1700 km/s. The observed X-ray structures were 45,000-230,000 km long. Simultaneous H-alpha images were available in three cases; they showed brightenings when the fast-moving fronts arrived at the chromosphere. The fast-moving fronts are interpreted as electron thermal conduction fronts since their velocities are consistent with conduction at the observed temperatures of 1-3 x 10 to the 7th K. The inferred conductive heat flux of up to 10-billion ergs/s sq cm accounts for most of the energy released in the flares, implying that the flares were primarily thermal phenomena. Title: New Materials Applications in Solar Spectral Analysis Authors: Rust, D. M. Bibcode: 1985AuJPh..38..781R Altcode: The use of lithium niobate and liquid crystals in solar instrumentation designed for automatic measurement of spectral line shifts is described. A solid Fabry-Perot etalon of lithium niobate has an acceptance angle 5.3 times greater than an air-spaced Fabry-Perot filter for the same allowed passband broadening, and the lithium niobate device has no moving parts. The use of liquid crystals in Zeeman-effect analysers is also described. Progress toward implementation of devices with lithium niobate and liquid crystals in a solar telescope is described. Title: Fast-Moving Fronts in Solar Flare Loops Authors: Rust, D. M. Bibcode: 1985spit.conf.1073R Altcode: No abstract at ADS Title: Permanent Changes in Filaments Near Solar Flares Authors: Rust, D. M. Bibcode: 1984SoPh...93...73R Altcode: High resolution Hα images obtained before and after 57 importance 1N or larger flares have been examined for changes in the magnetic fields (B) transverse to the line of sight. It was assumed that Hα chromospheric structures outline B. In 37% of the cases, there was a reconfiguration of segments of filaments or of chromospheric fibrils. Examination of data from 21 non-flare intervals shows such changes in 24% of cases. When changes of any kind, including total disappearance and length changes, are included, the proportions for flare and non-flare intervals increase to 58% and 52%, respectively. It is concluded that flares do not cause enduring magnetic field changes in the chromosphere. Title: Flare Loops Heated by Thermal Conduction Authors: Rust, D. M.; Somov, B. V. Bibcode: 1984SoPh...93...95R Altcode: A flare observed with the Hard X-Ray Imaging Spectrometer (HXIS) was studied during its rise to maximum temperature and X-ray emission rate. Two proximate flare loops, of lengths 2.8 × 109 cm and 1.1 × 1010 cm, rose to temperatures of 21.5 × 106 K and 30 × 106 K, respectively, in 30 s. Assuming equal heat flux F into each loop from a thermal source at the point where they met, we derive a simple relationship between temperature T and loop length , which gives a loop temperture ratio of 0.68, in close agreement with the observed ratio of 0.72. The observations imply that heating in each loop was maintained by a thermal flux of ∼ 5 × 109 ergs cm-2 s-1. It is suggested that conductive heating adequately describes the rise and maximum phase emissions in the loops and that long flare loops reach higher temperatures than short loops during the impulsive phase because of an equipartition of energy between them at their point of interaction. Title: The Solar Maximum Observatory. Authors: Rust, D. M. Bibcode: 1984JHATD...5..188R Altcode: The successful retrieval and repair of the Solar Maximum Mission (SMM) satellite by Shuttle astronauts in April 1984 permitted continuance of solar flare observations that began in 1980. The SMM carries a soft X ray polychromator, gamma ray, UV and hard X ray imaging spectrometers, a coronagraph/polarimeter and particle counters. The data gathered thus far indicated that electrical potentials of 25 MeV develop in flares within 2 sec of onset. X ray data show that flares are composed of compressed magnetic loops that have come too close together. Other data have been taken on mass ejection, impacts of electron beams and conduction fronts with the chromosphere and changes in the solar radiant flux due to sunspots. Title: Spatial Development of X-Ray Emission during the Impulsive Phase of a Solar Flare Authors: de Jager, C.; Boelee, A.; Rust, D. M. Bibcode: 1984SoPh...92..245D Altcode: The flare of 11 November, 1980, 17∶25 UT occurred in a magnetically complex region. It was preceded by some ten minutes by a gradual flare originating over the magnetic inversion line, close to a small sunspot. This seems to have triggered the main flare (at 70 000 km distance) which originated between a large sunspot and the inversion line. The main flare started at 17∶23∶20 UT with a slight enhancement of hard X-rays (E > 30 keV) accompanied by the formation of a dark loop between two Hα bright ribbons. In 3-8 keV X-rays a southward expansion started at the same time, with ν ∼- 500 km s −1. At the same time a surge-like expansion started. It was observable slightly later in Hα, with southward velocities of ≳ 200 km s−1. The dark Hα loop dissolved at ∼ 17∶24 UT at which time several impulsive phenomena started such as a complex of hard X-ray bursts localized in a small area. At the end of the impulsive phase at 17∶25∶40 UT, a coronal explosion occurred directed southward with an initial expansion velocity of ∼ 1800 km s−1, decreasing in 40 s to ∼500 km s−1. Title: Flare Loops Heated by Thermal Conduction Authors: Rust, D. M.; Somov, B. V. Bibcode: 1984BAAS...16Q.544R Altcode: No abstract at ADS Title: Energy-transfer processes in flares Authors: Rust, D. M. Bibcode: 1984AdSpR...4g.191R Altcode: 1984AdSpR...4..191R This paper deals with Solar Maximum Year observations that can shed light on the roles of energetic electron beams and thermal conduction in solar flares. The emphasis is on X-ray and UV images and on the interpretation of chromospheric spectra. The format is that of a one-sided debate advocating the view that most of the flare energy that reaches the chromosphere is transferred by thermal conduction rather than by energetic electron beams. Reference is made to papers offering opposing points of view on this still controversial question. Title: Thermal Wave Fronts in Solar Flares Authors: Rust, D. M.; Simnett, G. M.; Smith, D. F. Bibcode: 1983BAAS...15Q.919R Altcode: No abstract at ADS Title: Solar activity. Authors: Rust, D. M. Bibcode: 1983RvGSP..21..349R Altcode: 1983RvGeo..21..349R The increased data base and scope of the theoretical models for solar flares are reviewed. Data have been gathered from the Skylab instrumentation, the Solar Maximum Mission, and the Very Large Array. Skylab X ray images revealed regularly spaced bright spots on the solar surface. Studies have also been performed on the emergence of magnetic fields, the coronal structures defined by magnetic fields above active regions, and the behavior and composition of post-flare loops. It has been found that coronal transients are associated with eruptive prominences with and without flares up to 70 pct of the time. Two classes of solar flares have been identified, i.e., small volume, low altitude with a short rise time, and long decay events with a larger coronal loop structure. Evidence for thermal and nonthermal causes for the electron velocity distribution in the flares is discussed. Finally, SMM data has shown chromospheric reactions to magnetic field variations in the photosphere and the response of the interplanetary medium to coronal transients. Title: Observations of H-alpha and microwave brightening caused by a distant solar flare Authors: Kundu, M. R.; Rust, D. M.; Bobrowsky, M. Bibcode: 1983ApJ...265.1084K Altcode: Three subflares were observed at 6 cm λ and at Hα (6563 Å) with the VLA and the Solar Observing Optical Network high resolution telescopes. Synthesized maps with integration times of 10 and 30 s show that most of the 6 cm burst emission originated in ≡10arcsec - 15arcsec features coincident with or adjacent to Hα flare kernels. During the onset of one of the subflares 6 cm emission was discovered in a loop stretching >105 km from the primary flare site; this emission was associated with faint Hα flarelike brightness at the remote footpoint of the loop. Assuming that the energy for the distant brightening originated at the primary flare site, it is found that ≡4 × 1024 ergs s-1 propagated along the connecting magnetic loop at a velocity of ≥ 6000 km s-1. Various possible mechanisms for the distant activation are discussed. Title: Coronal Disturbances and Their Terrestrial Effects Authors: Rust, D. M. Bibcode: 1983SSRv...34...21R Altcode: Coronal disturbances lead to geomagnetic storms, proton showers, auroras and a wide variety of other phenomena at Earth. Yet, attempts to link interplanetary and terrestrial phenomena to specific varieties of coronal disturbances have achieved only limited success. Here, several recent approaches to prediction of interplanetary consequences of coronal disturbances are reviewed. The relationships of shocks and energetic particles to coronal transients, of proton events to γ-ray bursts, of proton events to microwave bursts, of geomagnetic storms to filament eruptions and of solar wind speed increases to the flare site magnetic field direction are explored. A new phenomenon, transient coronal holes, is discussed. These voids in the corona appear astride the long decay enhancements (LDE's) of 2 50 Å X-ray emission that follow Hα filament eruptions. The transient holes are similar to long-lived coronal holes, which are the sources of high speed solar wind streams. There is some evidence that transient coronal holes are associated with transient solar wind speed increases. Title: Optical Observations of Simple and Complex Flares Authors: Rust, D. M. Bibcode: 1982Obs...102..118R Altcode: No abstract at ADS Title: Solar Flares, Proton Showers, and the Space Shuttle Authors: Rust, D. M. Bibcode: 1982Sci...216..939R Altcode: The space shuttle era will focus renewed attention on the hazards of the space environment to human habitation. The chief unpredictable hazard for astronauts is energetic proton radiation from solar flares. In some orbits, there is no reasonable level of shielding material that will protect shuttle occupants from potentially lethal doses of radiation. The effects of a solar flare that occurred during the first flight of the Columbia are discussed and current flare research reviewed. The emphasis is on progress made during the recent international Solar Maximum Year toward understanding the origins of proton showers. Title: Solar Maximum Year; Proceedings of the Symposium, Ottawa, Canada, May 16-June 2, 1982 Authors: Svestka, Z.; Rust, D. M.; Dryer, M. Bibcode: 1982AdSpR...2k....S Altcode: 1982AdSpR...2.....S Results of research conducted during the Solar Maximum Year from August 1979 to through February 1981 are presented, focusing on flare build-up, energy release in flares, and travelling interplanetary phenomena. Topics examined include the relation of solar flares to the evolution and proper motions of magnetic fields, pre-flare heating of filaments, mass motions in a quiescent filament, multiple wavelength observations of flaring active regions, energy transfer in solar flares, direct evidence for chromosphere evaporation in a well-observed compact flare, physics of the impulsive phase of solar flares, and the analysis of ultra-fast fine structures of microwave bursts. Also considered are the effects of electron-cyclotron masers during flares, high energy particle acceleration in flares, particle charge interchange during acceleration in flare regions, diamagnetic aspects of the coronal transient phenomenon, particle acceleration by coronal and interplanetary shock waves, and the propagation of energetic particles in the solar wind. For individual items see A83-35202 to A83-35235 Title: Study of energy release in flares Authors: Rust, D. M. Bibcode: 1982AdSpR...2k...5R Altcode: 1982AdSpR...2....5R No abstract at ADS Title: Origin and Location of the Hard X-Ray Emission in a Two-Ribbon Flare Authors: Hoyng, P.; Duijveman, A.; Machado, M. E.; Rust, D. M.; Svestka, Z.; Boelee, A.; de Jager, C.; Frost, K. T.; Lafleur, H.; Simnett, G. M.; van Beek, H. F.; Woodgate, B. E. Bibcode: 1981ApJ...246L.155H Altcode: No abstract at ADS Title: Optical and radio observations of the 1980 March 29, April 30, and June 7 flares Authors: Rust, D. M.; Benz, A.; Hurford, G. J.; Nelson, G.; Pick, M.; Ruzdjak, V. Bibcode: 1981ApJ...244L.179R Altcode: Ground-based solar observations are analyzed for three of the flares discussed in the accompanying Solar Maximum Mission reports. The principal conclusions are that H-alpha begins to brighten several minutes before the impulsive, hard X-ray bursts, that the preflare heating and impulsive phases of the three flares occurred in loop-shaped structures of about 3500 km semidiameter, and that after the impulsive phase a much larger volume (about 200 times) of flare plasma was present for the flare main phase. Evidence is presented for the escape of 100-500 keV electrons into the larger volume and into the corona during the impulsive phase. For the April 30 flare, the inferred origin of the hard X-ray burst is near the feet of the magnetic loops. Title: A Statistical Study of Solar Flares and Permanent Filament Changes Authors: Rust, D. M. Bibcode: 1981BAAS...13..820R Altcode: No abstract at ADS Title: VLA Observations of Large Scale Microwave Brightening Following a Flare Authors: Bobrowsky, M.; Kundu, M. R.; Rust, D. Bibcode: 1981BAAS...13..846B Altcode: No abstract at ADS Title: Análisis del flare en luz blanca del 7 de agosto de 1972. Espectro y estructura atmosférica Authors: Machado, M. E.; Rust, D. M. Bibcode: 1981BAAA...20..147M Altcode: Presentamos el análisis espectral de un flare en luz blanca ocurrido el 7-8-72. Los espectros obtenidos en la región λλ 3530 a 5895 Å y la secuencia de filtrogramas centrados en 4950 y 5900 Å (200 Å de banda pasante) constituyen la más completa información sobre un evento de esta naturaleza obtenida hasta el momento. El análisis del espectro de Fe I y de las líneas moleculares de CN y CH muestra que la máxima profundidad de penetración del flare es d 200 km sobre τ5000 = 1 en la Harvard-Smithsonian Reference Atmosphere. El análisis de las líneas de Balmer indica que el flare ocurrió en una capa muy delgada de la atmósfera y que el calentamiento y ionización fueron debidos a la inyección de electrones de energías superiores a 100 keV. El análisis de la emisión continua indica que ésta es producida por transiciones libre-ligado de hidrógeno a una temperatura de 8500 K ± 500 K. Title: Application of X-ray imaging techniques to auroral monitoring Authors: Rust, D. M.; Burstein, P. Bibcode: 1981eirs.sympT....R Altcode: The precipitation of energetic particles into the ionosphere produces bremsstrahlung X-rays and K-alpha line emission from excited oxygen and nitrogen. If viewed from a spacecraft in a highly elliptical polar orbit, this soft (0.3 - 3.0 keV) X-radiation will provide an almost uninterrupted record of dayside and nightside auroras. A grazing incidence X-ray telescope especially designed for such auroral monitoring is described. High photon collection efficiency will permit exposure times of approximately 100 seconds during substorms. Spectrophotometry will allow users to derive the energy spectrum of the precipitating particles. If placed in a 15 earth-radius orbit, the telescope can produce auroral X-ray images with 30 km resolution. Absolute position of X-ray auroras can be established with a small optical telescope co-aligned with the X-ray telescope. Comparison of X-ray and optical images will establish the height and global distribution of X-ray aurorae, relative to well-known optical auroras, thus melding the new X-ray results with knowledge of optical auroras. Title: Horizontal distribution of the X-ray energy deposit in the chromosphere and H alpha two ribbon flares Authors: Henoux, J. C.; Rust, D. Bibcode: 1980A&A....91..322H Altcode: The two-ribbon Hα brightening and the X-ray emitting coronal loop arcade during the very late phase of the 29 July 1973 flare are examined. By means of a simple geometrical model of the X-ray emitting structures, the horizontal distribution of X-radiation is computed for several different levels in the chromosphere. It is found that an arcade of X-ray emitting loops, commonly found over large two-ribbon flares, gives an energy deposit pattern in the chromosphere similar in shape to the Hα flare emission. Isophotes of the Hα brightening are compared to the X-ray energy deposit horizontal variation profiles from a single loop and from an arcade of loops. The brightest 29 July isophotes fit midway between the X-ray profiles associated respectively with a loop and an arcade. The maximum X-ray energy deposit rate of 1.5 106 ergs cm-2 s-1 is slightly higher than the peak Hα emission rate. It is concluded that X-ray radiation is an important source of energy for Hz flares. There seems to be no need for in- situ energy release in the chromosphere. Title: Evidence for Electron and Proton Beams in a White-Light Flare Authors: Rust, David M. Bibcode: 1980BAAS...12..910R Altcode: No abstract at ADS Title: Spatial and temporal correlation of high and low temperature solar flare emissions. Authors: Rust, D. M.; Buhmann, R. W.; Dennis, B. R.; Robinson, R. D.; Willson, R. F.; Simon, M. Bibcode: 1980BAAS...12..752R Altcode: No abstract at ADS Title: Energy Release in Solar Flares Authors: Emslie, A. G.; Rust, D. M. Bibcode: 1980SoPh...65..271E Altcode: We summarize key problems in our understanding of energy release in solar flares, as addressed by participants in a recent workshop. These problems fall into three broad areas: (i) Transport and thermalization of energy, (ii) acceleration of particles, and (iii) origin and effects of mass motions. We then describe how suitably coordinated collaborative observing sequences during the forthcoming Solar Maximum Year are potentially capable of resolving some of these issues. Title: Application of a Magnetograph and X-Ray Telescope to the Study of Coronal Structure Variations Authors: Rust, D. M. Bibcode: 1980NASCP2098..259R Altcode: 1980sscs.nasa..259R The application of magnetographs and X-ray imaging techniques to determine the magnitude, structure, origin, and evolution of the solar coronal magnetic field is examined. The spatial and temporal resolution of the X-ray telescope is discussed and a comparison of ground based magnetogram sequences versus a magnetograph in space is presented. Skylab photographs of the evolution of transient coronal holes are provided. Title: Mass ejections Authors: Rust, D. M.; Hildner, E.; Hansen, R. T.; Dryer, M.; McClymont, A. N.; McKenna-Lawlor, S. M. P.; McLean, D. J.; Schmahl, E. J.; Steinolfson, R. S.; Tandberg-Hanssen, E. Bibcode: 1980sfsl.work..273R Altcode: 1980sofl.symp..273R Observations and model simulations of solar mass ejection phenomena are examined in an investigation of flare processes. Consideration is given to Skylab and other observations of flare-associated sprays, eruptive prominences, surges and coronal transients, and to MHD, gas dynamic and magnetic loop models developed to account for them. Magnetic forces are found to confine spray material, which originates in preexisting active-region filaments, within steadily expanding loops, while surges follow unmoving, preexisting magnetic field lines. Simulations of effects of a sudden pressure pulse at the bottom of the corona are found to exhibit many characteristics of coronal transients associated with flares, and impulsive heating low in the chromosphere is found to be able to account for surges. The importance of the magnetic field as the ultimate source of energy which drives eruptive phenomena as well as flares is pointed out. Title: Solar Maximum Mission not the First - OSO-7/NASA Satellite 1972AUG Authors: Rust, D. M. Bibcode: 1980SciN..118..275R Altcode: No abstract at ADS Title: Solar forecast and real-time monitoring needs of the Study of Energy Release in Flares (SERF) Authors: Rust, D. M. Bibcode: 1979stp.....2..331R Altcode: Complementary, simultaneous observations of flares from as many observatories, both ground based and orbiting, as possible planned for the Solar Maximum Year are considered. The need for forecasts of solar activity on long term, one week, and two day intervals is described. Real time reporting is not needed, but daily summaries of activity and permanent records are important. Title: Warming Up for the Solar Maximum Year Authors: Rust, D. M. Bibcode: 1979S&T....58..315R Altcode: The paper examines the current technology that is used in studying solar activity and its effect on the planetary system. Attention is given to solar flares and methods for predicting their eruptions. The Solar Maximum Year (SMY) program that calls for intensive observations of three aspects of solar activity, including the source of solar flare energy, is presented. Two models that discuss whether solar flares are thermal or nonthermal phenomena are examined. Title: Slowly moving disturbances in the X-ray corona. Authors: Rust, D. M.; Svestka, Z. Bibcode: 1979SoPh...63..279R Altcode: Sequences of soft X-ray pictures, taken aboard Skylab between May and November, 1973, have made it possible to detect slowly moving disturbances originating in disrupted filaments and causing subsequent brightenings of distant coronal structures. With speeds decreasing from ∼400 km s-1 shortly after the filament disruption to ∼10 km s-1 four or five hours later, these disturbances appear to be identical with slow waves earlier inferred by Bruzek, Öhman, and Yajima from chromospheric observations. Title: Energy release in solar flares. Proceedings of the workshop on Energy Release in Flares Authors: Rust, D. M.; Emslie, A. G. Bibcode: 1979cammawork.....R Altcode: Parallel meetings of three small teams were held where theories of thermalization, particle acceleration, and mass motion in flares were discussed. An overview of the major scientific issues identified for the study of energy release in flares is given. More specific discussions of the three program areas are included. The concepts of Joint Observing Sequences and Collaborative Observing Sequences (COSs) developed by NASA's Solar Maximum Mission investigators are explained. Specific observations needed for each COS are listed. Title: Physical parameters in long-decay coronal enhancements. Authors: MacCombie, W. J.; Rust, D. M. Bibcode: 1979SoPh...61...69M Altcode: X-ray images have been studied quantitatively to determine electron temperature and density as functions of time in two long-decay X-ray enhancements (LDE's). This is the first study of the X-ray emission from LDE's to include all corrections for scattering and vignetting. Derived electron density is about twice that found by Vorpahl et al. (1977) and by Smith et al. (1977) in the same events. Our results are combined with those for two other LDE's to find their general characteristics. The LDE's all had the form of arcades of very bright loops which were 1-3 × 106 K hotter at the apices than along the legs. This temperature structure was maintained for at least 8 hr in each case. From this it is inferred that continual heating was taking place at the loop apices. Each LDE was preceded by a filament eruption and a white-light transient. Each was associated with a loop prominence system (LPS) composed of cool (Te < 105 K) loops nested 2-8 × 103 km below the hot LDE loops. And, although the energy release rates in the four events varied greatly even 4 hr after onset, they all had similar growth rates (loop height vs time ≅ 1 km s−1). Event lifetimes were very long, from 24 to 72 hr. After a survey of published models, it is concluded that only a magnetic reconnection model (e.g., Kopp and Pneuman, 1976) is consistent with these observations of the LDE-LPS phenomenon. Title: Coronal Manifestations of Eruptive Prominences - Observations and Interpretation. Authors: Rust, D. M. Bibcode: 1979phsp.coll..252R Altcode: 1979phsp.conf..252R; 1979IAUCo..44..252R Observations of the coronal manifestations associated with eruptive solar prominences are discussed. Coronal brightness changes observed to be associated with eruptive prominences include the appearance of a thin filament in X-ray and Fe XIV coronal emissions during the period of prominence activation, followed by the appearance of loop systems and slowly-moving disturbances (soft-X-ray brightness changes). Dramatic changes in the structure of the inner corona, observed in line emissions, include loop expansions, coronal whips, coronal realignments with prominence eruptions and transient coronal holes, all of which are indicative of magnetic field rearrangements. Scattering observations of outer coronal structure reveal an ejection of about 3 x 10 to the 15 g of mass from the inner corona through the outer corona in association with prominence eruptions. The close relationship of prominence eruptions and coronal loop transients is discussed, and eruptive prominences are interpreted in terms of the destabilization of magnetic fields around the prominences. Title: Discussion Authors: Acton, L. W.; Engvold, O.; Heasley, J. N.; Heyvaerts, J.; Hirayama, T.; Kundu, M. R.; Leroy, J. L.; Malville, J.; Rust, D. M.; Zirin, H. Bibcode: 1979phsp.coll...31A Altcode: 1979IAUCo..44...31A No abstract at ADS Title: Discussion Authors: Hirayama, T.; Maltby, P.; Malville, J.; Martin, S. F.; Rust, D. M.; Spicer, D. S. Bibcode: 1979phsp.coll..267H Altcode: 1979IAUCo..44..267H No abstract at ADS Title: Discussion Authors: Anzer, U.; Raadu, M. A.; Rompolt, B.; Rust, D. M.; Sheeley, N.; Spicer, D. S. Bibcode: 1979phsp.coll..171A Altcode: 1979IAUCo..44..171A No abstract at ADS Title: Discussion Authors: Engvold, O.; Gaizauskas, Gaizauskas; Rust, D. M.; Sheeley, N.; Tandberg-Hanssen, E.; Ohman, Y.; Zirin, H. Bibcode: 1979phsp.coll..207E Altcode: 1979IAUCo..44..207E No abstract at ADS Title: Solar flares Authors: Rust, D. M. Bibcode: 1979sswp.book...51R Altcode: The present paper deals with explosions in a magnetized solar plasma, known as flares, whose effects are seen throughout the electromagnetic spectrum, from gamma-rays through the visible and to the radio band. The diverse phenomena associated with flares are discussed, along with the physical mechanisms that have been advanced to explain them. The impact of solar flare research on the development of plasma physics and magnetohydrodynamics is noted. The rapid development of solar flare research during the past 20 years, owing to the availability of high-resolution images, detailed magnetic field measurements, and improved spectral data, is illustrated. Title: Discussion Authors: Acton, L. W.; Anzer, U.; Engvold, O.; Martin, S. F.; Pneuman, G. W.; Rust, D. M.; Tandberg-Hanssen, E.; Zirin, H. Bibcode: 1979phsp.coll..164A Altcode: 1979IAUCo..44..164A No abstract at ADS Title: Slowly-Moving Disturbances in the X-Ray Corona. Authors: Rust, D. M.; Svestka, Z. Bibcode: 1979phsp.coll..276R Altcode: 1979IAUCo..44..276R; 1979phsp.conf..276R A synoptic movie made from nearly 1000 pictures of the solar X-ray corona taken by the S-054 X-ray telescope on Skylab has led to the discovery of disturbances with propagation velocities under 100 km/sec and extending over distances of the order of one solar radius. The disturbances are revealed as brightened coronal structures at progressively greater distances from a central point, usually an active region with an activated or disappearing filament. In a number of cases these coronal brightenings were accompanied by quiescent filament disappearances. The inferred coronal velocities and the rates of damping were found to be in excellent agreement with the velocity curves deduced by Bruzek (1952), in his slow wave hypothesis, and possibly confirmed by Oehman and Oehman (1953) and Yajima (1971) to explain the activation of filaments at great distances from flares. The fact that many of the events showed little or no flaring associated with the filament disappearance at onset leads to the conclusion that the source of the slow disturbances is linked to the initial filament eruption itself, possibly in restructuring of the magnetic fields or in the coronal heating that typically accompanies active region filament eruptions. Title: Soft X-ray observations of large-scale coronal active region brightenings. Authors: Rust, D. M.; Webb, D. F. Bibcode: 1977SoPh...54..403R Altcode: One-hundred fifty-six large-scale enhancements of X-ray emission from solar active regions were studied on full-disk filterheliograms to determine characteristic morphology and expansion rates for heated coronal plasma. The X-ray photographs were compared with Hα observations of flares, sudden filament disappearances, sprays and loop prominence systems (LPS). Eighty-one percent of the X-ray events were correlated with Hα filament activity, but only forty-four percent were correlated with reported Hα flares. The X-ray enhancements took the form of loops or arcades of loops ranging in length from 60 000 km to 520 000 km and averaging 15 000 km in width. Lifetimes ranged from ≥3 hr to >24 hr. Event frequency was ∼1.4 per day. X-ray loop arcades evolved from sharp-edged clouds in cavities vacated by rising Hα filaments. Expansion velocities of the loops were ∼50 km s-1 immediately after excitation and 1-10 km s-1 several hours later. These long-lived loop arcades are identified with LPS, and it is suggested that the loops outlined magnetic fields which were reconnecting after filament eruptions. Another class of X-ray enhanced loops stretched outside active regions and accompanied sprays or lateral filament ejections. Hα brightenings occurred where these loops intersected the chromosphere. Inferred excitation velocities along the loops ranged between ∼300 and 1200 km s-1. It is suggested that these loops outlined closed magnetic fields guiding slow mode shocks from flares and filament eruptions. Title: Do surges heat the corona? Authors: Rust, D. M.; Webb, D. F.; MacCombie, W. Bibcode: 1977SoPh...54...53R Altcode: A comparison of X-ray filtergrams obtained during the Skylab mission 8 hr before and within 4 hr following 54 active region surges on the disk revealed only 6 cases of long-enduring, large-scale (> 10 000 km) coronal enhancements that might have been associated with surge activity. It is concluded that there is no evidence for any substantial increase in the temperature or amount of coronal material during reported surges. Title: An emerging flux model for the solar phenomenon. Authors: Heyvaerts, J.; Priest, E. R.; Rust, D. M. Bibcode: 1977ApJ...216..123H Altcode: An outline is presented of the physical processes involved in the emerging flux model, which appears to explain naturally many solar flare observations. The separate physical phases of the basic model include a preflare heating phase as the new flux emerges, an impulsive phase as high-energy particles are accelerated, a flash (or explosive) phase when the H-alpha intensity increases, and a main phase while it decreases. The extent and morphology of the main phase emission depend on the structure of the magnetic field region in which the new flux finds itself imbedded. It is suggested that a (small) simple loop flare occurs if the new flux appears in a region where no great amount of magnetic energy in excess of potential is stored. A two-ribbon flare occurs if the flux emerges near the polarity inversion line of an active region that has begun to develop filaments. Title: An emerging flux model for solar flares. Authors: Heyvaerts, J.; Priest, E.; Rust, D. M. Bibcode: 1977SoPh...53..255H Altcode: No abstract at ADS Title: Slowly Moving X-Ray Disturbances from Flares. Authors: Rust, D. M.; Svestka, Z. Bibcode: 1977BAAS....9..329R Altcode: No abstract at ADS Title: Expansion of an X-ray coronal arch into the outer corona. Authors: Rust, D. M.; Hildner, E. Bibcode: 1976SoPh...48..381R Altcode: An asymmetric, expanding arch, photographed in the inner corona with an X-ray telescope on 13 August, 1973, is identified as the source of the mass ejected in a white light transient in the outer corona. The morphology, angular position, estimated mass and apparent rate of upward acceleration of the lower coronal arch are similar to those of the arch seen passing through the outer corona. The mass of material removed from the lower corona is estimated at 2 × 1015 g, and the upward movement is consistent with a constant acceleration of 12.5 m s−2 between 1.3 and 5 R. Title: Coronal X-ray enhancements associated with Hα filament disappearances Authors: Webb, D. F.; Krieger, A. S.; Rust, D. M. Bibcode: 1976SoPh...48..159W Altcode: A survey of soft X-ray images from Skylab has revealed a class of large-scale transient X-ray enhancements in the lower corona which are typically associated with the disappearance of Hα filaments away from active regions. Contemporary with the Hα filament disappearance, X-ray emitting structures appeared at or near the filament location with shape and size resembling the filament. Eventually these structures faded, but the filament cavity was no longer obvious. Typically the peak of the X-ray event lagged the end of the filament disappearance by tens of minutes. The durations of the coronal X-ray enhancements were considerably longer than the associated Hα filament disappearances. Major flare effects, such as chromospheric brightenings, typically were not associated with these X-ray events. Title: Observations of Flare-Associated Magnetic Field Changes Authors: Rust, D. M. Bibcode: 1976RSPTA.281..427R Altcode: 1976RSLPT.281..427R Although it is widely accepted that energy for solar flares must be sought in rapid conversion of magnetic energy, observations of flare-associated magnetic field changes have proven difficult and controversial. Different observers have come to widely varying conclusions about the nature and reality of the reported flare-associated field changes. However, it is possible to reconcile these differences because most of the observations have been made at a level of precision comparable with the maximum field changes that even the largest flares could result from. High resolution filtergrams and magnetograms made within the past five years have made it possible to deduce that flares are associated with the emergence of new flux and with its reconnexion to older fields. Recent observations are reviewed. Title: Optical and Magnetic Measurements of the Photosphere and Low Chromosphere Authors: Rust, D. M. Bibcode: 1976RSPTA.281..353R Altcode: 1976RSLPT.281..353R Sequences of photographs at a resolution of 1' ' achieved during the past ten years have had a very significant impact upon our understanding of the development, mature structure and decay of active regions. Cinematic studies, especially, have allowed the emergence of new fields and their motions within the active centre to be studied in detail. Cinematic magnetic observations show how sunspots decay through the outward flight of tiny knots of magnetic flux. The newest advances are being made with arrays of photosensitive diodes at the focal planes of high dispersion spectrographs. The diode array at the Sacramento Peak Observatory produces simultaneous photometric observations at many different wavelengths throughout the visible and near infrared spectrum. Quantitative studies of magnetic fields and chromospheric structure are discussed. In particular, the moving magnetic features apparently produce surges in the superpenumbra around large sunspots. Title: Expansion of an X-ray Coronal Arch Into the Outer Corona Authors: Rust, D. M.; Hildner, E. Bibcode: 1976BAAS....8..368R Altcode: No abstract at ADS Title: Enhancement of Soft X-ray Emission Associated with the Motion of Cool Material Through the Lower Corona Authors: Rust, D. M.; Webb, D. F. Bibcode: 1976BAAS....8..316R Altcode: No abstract at ADS Title: An active role for magnetic fields in solar flares. Authors: Rust, D. M. Bibcode: 1976SoPh...47...21R Altcode: Magnetic fields in the low corona are the only plausible source of energy for solar flares. Other energy sources appear inadequate or uncorrelated with flares. Low coronal magnetic fields cannot be measured accurately, so most attention has been directed toward measurements of the photospheric magnetic fields from which coronal developments may be inferred. Observations of these magnetic fields are reviewed. It is concluded that, except possibly for the largest flares, changes in the photospheric magnetic fields in flaring centers are confined to evolutionary changes associated with emergence of new magnetic flux. Flare observations with the 10830 Å line of helium, in particular, are discussed. It is concluded that the brightest flare knots appear near points of emergent magnetic flux. Pre-flare activation and eruptions of Hα filaments are discussed. It is concluded that the rapid motions in filaments indicate unambiguously that the magnetic fields in the low corona are severely disrupted prior to most flares. The coronal signature of Hα filament eruptions is illustrated with soft X-ray photographs from the S-054 experiment of the NASA Skylab mission. An attempt is made, by studying X-ray flare morphology, to determine whether flares grow by reconnections between adjacent or intertwined magnetic elements or by triggering, in which each flaring loop drives adjacent loops to unstable states. It is concluded that successive loop brightenings are most easily interpreted as the result of magnetic field reconnections, although better time resolution is required to settle the question. A model of magnetic field reconnections for flares associated with filament activation and emerging magnetic flux is presented. Title: Magnetic fields in solar active regions. Authors: Rust, D. M. Bibcode: 1976npsa.conf...19R Altcode: No abstract at ADS Title: Magnetic Fields in Solar Active Regions Authors: Rust, D. M. Bibcode: 1976saop.book...33R Altcode: No abstract at ADS Title: Energy Balance in a Magnetically Confined Coronal Structure Observed by OSO-7 Authors: Neupert, W. M.; Nakagawa, Y.; Rust, D. M. Bibcode: 1975SoPh...43..359N Altcode: A model of a coronal region of enhanced Fexv and FeXVI emission is developed and its energy balance is examined using extreme ultraviolet observations from OSO-7 together with calculations of possible force-free coronal magnetic field configurations. The coronal emissions overlying the photospheric boundary between regions of opposite magnetic polarity are found to be associated with generally non-potential (current-carrying) magnetic fields in the forms of arches with footpoints in regions of opposite polarity. The orientation of these arches relative to the neutral line changes with degree of ionization of the emitting ion (which we infer from our limb observations to be a function of height) and may be evidence of differing electric currents along various field lines. The appearance of a coronal arch, seen side-on, can conveniently be represented by a parabola and a detailed analysis (Appendix) shows this to be a realistic approximation that should be generally useful in analyzing two-dimensional pictures of coronal structures. Applying this analysis to the most prominent coronal region observed in the radiations of Fexv and Fexvi, we find a maximum in the electron temperature, Te, of 2.6 × 106K at the top of arches whose heights are 20000-40000 km and whose footpoints are separated by ≈ 100000 km. A temperature gradient of ▽Te≈5 × 10-5K cm-1 is found in this coronal structure. Radiative losses are typically fifteen times greater than conductive losses and the energy deposition required to maintain the coronal feature is nearly uniformly distributed along its length. Title: A model for the solar flare Authors: Canfield, R. C.; Priest, E. R.; Rust, D. M. Bibcode: 1975STIN...7615007C Altcode: It is suggested that many solar flares occur due to an interaction between newly emerging magnetic flux and an active region filament. A current sheet forms between the new and old flux and, when its electric current density exceeds a critical value, rapid magnetic fields reconnection takes place. Electrons are then accelerated to high energies and follow the magnetic field lines down to the chromosphere where they produce several (typically three) bright H alpha knots. Magnetic energy is continuously released as reconnected prominence fields are allowed to untwist. Two ribbons of H alpha emission are produced by one or more of three mechanisms: energetic particles, thermal conduction or shocks due to infalling material. Title: The work of the diode array: He 10 830 observations of spicules and subflares Authors: Rust, D. M.; Bridges, C. A., III Bibcode: 1975SoPh...43..129R Altcode: At a spatial resolution of 1″ and with spectral passbands of 0.25-0.47 Å, the chromospheric fine structure was studied with an array of 512 silicon photodiodes. The high quantum efficiency of the diodes in the near infrared allowed low noise spectroheliograms to be constructed from observations in the lines of H I, Ca II, and He I. Magnetograms of the underlying photosphere were obtained simultaneously. Tachograms in the He 10830 Å line revealed 1″ points and elongated features that are interpreted as spicules seen against the disk. Active regions and filaments at 10830 are compared with Hα and Ca II (8542 Å) features. Filament contrast increases with the proximity of bright plage. Twelve subflares were studied and in eight cases, 3-5″ kernels of He I emission appeared over small, growing pores or over 5″ patches of magnetic field emerging through the photosphere. All the subflares showed 10830 emission, contrary to established belief that the 10830 line goes into emission only in the largest flares. All the subflares included at least one emission kernel over regions where the photospheric magnetic field, as seen with a resolution of 1-2″, broke down into a mosaic of both polarities with 3-5″ diam. elements. Title: Coronal X-ray Transient Events Associated with Hα Filament Disappearances Authors: Webb, D.; Krieger, A.; Rust, D.; Vaiana, G. Bibcode: 1975BAAS....7..430W Altcode: No abstract at ADS Title: Moving Coronal Clouds Observed with the Skylab S-054 X-ray Telescope. Authors: Rust, D. M.; Webb, D. T. Bibcode: 1975BAAS....7Q.431R Altcode: No abstract at ADS Title: EUV Emission, Filament Activation and Magnetic Fields in a Slow-Rise Flare Authors: Rust, D. M.; Nakagawa, Y.; Neupert, W. M. Bibcode: 1975SoPh...41..397R Altcode: The evolution of coronal and chromospheric structures is examined together with magnetograms for the 1B flare of January 19, 1972. Soft X-ray and EUV studies are based on the OSO-7 data. The Hα filtergrams and magnetograms came from the Sacramento Peak Observatory. Theoretical force-free magnetic field configurations are compared with structures seen in the soft X-ray, EUV and Hα images. Until the flare, two prominent spots were connected by a continuous dark filament and their overlying coronal structure underwent an expansion at the sunspot separation rate of 0.1 km s−1. On January 19, the flare occurred as new magnetic fields emerged at ∼ 1019 Mx h−1 beneath the filament, which untwisted and erupted as the flare began. The pre-flare coronal emissions remained unchanged during the flare except for the temporary addition of a localized enhancement that started 5 min after flare onset. EUV lines normally emitted in the upper transition region displayed a sudden enhancement coinciding in time and location with a bright Hα point, which is believed to be near the flare `trigger' or onset point. The EUV flash and the initial Hα brightening, both of which occurred near the center of the activated filament, were followed by a second EUV enhancement at the end of the filament. The complete disruption of the filament was accompanied by a third EUV enhancement and a rapid rise in the soft X-ray emission spatially coincident with the disappearing filament. From the change of magnetic field inferred from Hα filtergrams and from force-free field calculations, the energy available for the flare is estimated at approximately 1031 erg. Apparently, changes in the overlying coronal magnetic field were not required to provide the flare energy. Rather, it is suggested that the flare actually started in the twisted filament where it was compressed by emerging fields. Clearly, the flare started below the corona, and it appears that it derived its energy from the magnetic fields in or near the filament. Title: The Work of the Diode Array Authors: Rust, D. M.; Bridges, C. A. Bibcode: 1975BAAS....7..365R Altcode: No abstract at ADS Title: Inference of the Hard X-Ray Source Dimensions in the 1972, August 7, White Light Flare Authors: Rust, D. M. Bibcode: 1975IAUS...68..243R Altcode: No abstract at ADS Title: Analysis of the August 7, 1972 White Light Flare: Light Curves and Correlation with Hard X-Rays Authors: Rust, D. M.; Hegwer, F. Bibcode: 1975SoPh...40..141R Altcode: Cinematic, photometric observations of the 3B flare of August 7, 1972 are described in detail. The time resolution was 2 s; the spatial resolution was 1-2″. Flare continuum emissivity at 4950 Å and at 5900 Å correlated closely in time with the 60-100 keV non-thermal X-ray burst intensity. The observed peak emissivity was 1.5 × 1010 erg cm−2 s−1 and the total flare energy in the 3900-6900 Å range was ∼1030 erg. From the close temporal correspondence and from the small distance (3″) separating the layers where the visible emission and the X-rays arose, it is argued that the hard X-ray source must have had the same silhouette as the white light flare and that the emission patches had cross-sections of 3-5″. There was also a correlation between the location of the most intense visible emissions near sunspots and the intensity and polarization of the 9.4 GHz radio emission. The flare appeared to show at least three distinct particle acceleration phases: one, occurring at a stationary source and associated with proton acceleration gave a very bluish continuum and reached peak intensity at ∼ 1522 UT. At 1523 UT, a faint wave spread out at 40 km s−1 from flare center. The spectrum of the wave was nearly flat in the range 4950-5900 Å. Association of the wave with a slow drift of the microwave emission peak to lower frequencies and with a softening of the X-ray spectrum is interpreted to mean that the particle acceleration process weakened while the region of acceleration expanded. The observations are interpreted with the aid of the flare models of Brown to mean that the same beam of non-thermal electrons that was responsible for the hard X-ray bremsstrahlung also caused the heating of the lower chromosphere that produced the white light flare. Title: Analysis of the August 7, 1972 White Light Flare: Its Spectrum and Vertical Structure Authors: Machado, M. E.; Rust, D. M. Bibcode: 1974SoPh...38..499M Altcode: Spectral data on a white light wave occurring during the explosive phase of the August 7 flare were obtained simultaneously with three telescopes at the Sacramento Peak Observatory. Spectrograms in the region λλ3530 to 5895 and sequences of filtergrams (∼ 200 Å halfwidth) at 4950 Å and 5900 Å constitute the most complete record of white light flare emission obtained to date. Analysis of the iron line spectrum and of the CN and CH molecular lines shows that the maximum depth of the emission in the flare wave is about 200 km above the photosphere of the Harvard-Smithsonian Reference Atmosphere. Analysis of the Balmer lines gives an electron density of 3 × 1013 cm−3 where the continuum emission is present. From the Balmer line analysis, it is concluded that, in agreement with Canfield (1974) and Shmeleva and Syrovatskii (1973), the flare occurs in a thin layer and that the heating and ionization of the flaring layers are due to the injection of 100 keV electrons. There is no need to postulate filamentary structure in the flaring layer in order to explain the observations. Analysis of the continuum emission in the wave indicates that it is produced by free-bound transitions of hydrogen at a temperature of ∼ 8500 K. In the impulsive phase of the flare emission arose from short-lived bluish knots which could not be studied in detail. In the following phase, the one to which the conclusions in this paper refer, the continuum emission coincided with the Hα ribbon expansion (the explosive phase). We identify it with the `yellowish-white' flares reported by Trouvelot (1891) and others. Title: The late June 1972 CINOF flares Authors: Rust, D. M.; Roy, J. R. Bibcode: 1974erp..rept.....R Altcode: This report is the result of an analysis of observations obtained during the campaign for integrated observations of solar flares. The aim was to obtain a more complete set of optical, radio, X-ray, EUV, and particle observations of a normal solar flare than has been available from earlier, uncoordinated efforts. Flares observed in the McMath regions are discussed, with emphasis on optical and X-ray observations. Title: Gyro-Resonance Emission Transverse to the Magnetic Field of a Large Spot Group Authors: Graf, Werner; Rust, David M. Bibcode: 1974BAAS....6S.287G Altcode: No abstract at ADS Title: The Spectrum and Vertical Structure of the August 7, 1972 White Light Flare Authors: Machado, Marcos E.; Rust, David M. Bibcode: 1974BAAS....6Q.291M Altcode: No abstract at ADS Title: Preliminary Interpretation of Diode Array Simultaneous Observations of He I and Ca II Line Profiles in Collaboration with ATM Authors: Linsky, J. L.; Dunn, R. B.; Rust, D. M. Bibcode: 1974BAAS....6S.290L Altcode: No abstract at ADS Title: A 512-channel photodiode array for solar observations. Authors: Dunn, R. B.; Rust, D. M.; Spence, G. E. Bibcode: 1974inas.conf..109D Altcode: No abstract at ADS Title: A 512-channel photodiode array for solar observations Authors: Dunn, R. B.; Rust, D. M.; Spence, G. E. Bibcode: 1974SPIE...44..109D Altcode: The Sacramento Peak Observatory has developed and placed in operation an array of photodiodes in the focal plane of a high dispersion spectrograph. The diodes record solar phenomena in the 4000-11000 A range. Signals from the diodes are digitized and computer processed into photographs or other output forms in real time. By varying the placement of 32-diode blocks in the spectrograph, any combination of wavelengths may be used in the construction of spectrograms, spectroheliograms, magnetograms and tachograms. Spatial resolutions vary between 1/2 and 2 arcsec with a spectral resolution of up to 0.02 A. The signal-to-noise ratio for a single observation is limited in most cases by scintillation to 300:1. Several examples of computer processed photograms are given. Title: Magnetic fields, loop prominences and the great flares of August, 1972 Authors: Rust, David M.; Bar, Varda Bibcode: 1973SoPh...33..445R Altcode: Lines of magnetic force, computed under the assumption that the solar corona is free of electric currents, have been compared with loop prominence systems associated with three flares in August, 1972. The computed fields closely match the observations of loops at a height of 40000 km at times 3-4 h after onset of the associated flares. Inferred magnetic field intensities in the loops range from 1300 G where the loops converge into a sunspot to 50-80 G at 40 000 km above the photosphere. The first-seen and lowest-lying loops are sheared with respect to the calculated fields. Higher loops conform more closely to the current-free fieldlines. A model of Barnes and Sturrock is used to relate the degree of shear to the excess magnetic energy available during the flare of August 7. On various lines of evidence, it is suggested that magnetic energy was available to accelerate particles not only during the impulsive phase of the flare, but also during the following 2-3 h. The particle acceleration region seems to be in the magnetic fields just above the visible loops. The bright outer edges of the flare ribbons are identified as particle impact regions. The dense knots of loop prominence material fall to the ribbons' inner edges. Title: Analysis of the August 7, 1972 White Light Flare: Changes in the Magnetic and Velocity Fields Authors: Rust, David M. Bibcode: 1973SoPh...33..205R Altcode: Measurements with the Doppler-Zeeman Analyzer reveal red shifts and decreasing magnetic fields in the photosphere immediately below the center of the August 7, 1972 proton flare. These observations are combined with spectra and photographs of sunspot developments in the region to produce a consistent picture of fluctuations in orientation and strength in the fields of three spots intimately connected with the flare. Before the flare, the photosphere appears to experience an upheaval of material frozen into rising lines of magnetic force. After the start of the flare and through the following 4 h, the motion is downward. Title: Magnetic Fields of the Loop Prominences of August 2, 7, and 11, 1972 Authors: Bar, Varda; Rust, David M. Bibcode: 1973BAAS....5Q.269B Altcode: No abstract at ADS Title: Solar High-Resolution Radio Measurements of Active Regions at a Wavelength of 2.8 cm. Authors: Grebenkemper, C. J.; Rust, D. M. Bibcode: 1973BAAS....5R..21G Altcode: No abstract at ADS Title: The Great Solar Flares of August, 1972 Authors: Rust, David M. Bibcode: 1972S&T....44..226R Altcode: No abstract at ADS Title: Flares and Changing Magnetic Fields Authors: Rust, David M. Bibcode: 1972SoPh...25..141R Altcode: An observational study of maps of the longitudinal component of the photospheric fields in flaring active regions leads to the following conclusions: The broad-wing Hα kernels characteristic of the impulsive phase of flares occur within 10″ of neutral lines encircling features of isolated magnetic polarity (`satellite sunspots'). Title: Real-time Analysis of Flare-associated Photospheric Magnetic Fields Authors: Rust, David M. Bibcode: 1972BAAS....4..390R Altcode: No abstract at ADS Title: Magnetic Fields in Solar Active Regions Authors: Rust, David M. Bibcode: 1972PrAA...30...33R Altcode: No abstract at ADS Title: Coronal Magnetic Fields above Active Regions Authors: Rust, D. M.; Roy, J. -R. Bibcode: 1971IAUS...43..569R Altcode: No abstract at ADS Title: Vertical Velocities and Horizontal Wave Propagation in the Solar Photosphere Authors: Musman, Steven; Rust, David M. Bibcode: 1970SoPh...13..261M Altcode: We used the Sacramento Peak Doppler-Zeeman Analyzer to study the velocity and magnetic fields in 60″ × 300″ areas on the solar disk. We map the steady component of the line-of-sight velocity and longitudinal magnetic fields and compare them with the coarse Ca+ network. The collective phase behavior of the 5-min oscillations is studied in detail. We find large scale phase coherence, including waves with typical horizontal phase velocities of 100 km/sec which can be followed up to 50 000 km. The important oscillatory features are interpreted in terms of the properties of modified sound waves. We find no apparent relationship between the steady and oscillatory fields. Title: Magnetic Fields in Quiescent Solar Prominences. II. Photospheric Sources Authors: Rust, David M. Bibcode: 1970ApJ...160..315R Altcode: Magnetograph observations of the photospheric magnetic fields 100000 km on either side of quiescent filaments have been made by using the 5250 A line of iron. Resolution was 5". The region ("neutral band") below stable filaments is free of radial fields more intense than 5 gauss. Filament structure is extremely sensitive to fields near the neutral hand. Filaments detour around local field concentrations or thin down enough to squeeze by. Occasionally, a filament will break up and reform about 30" away from intruding fields. Comparisons of the magnetic flux through filaments with that measured on either side of the neutral band show that the magnetograph underestimates the flux outside active regions by a factor of 4. A comparison of observations with the Kippenhahn and Schltiter magnetohydrostatic model of prominences tends to confirm the correctness of the model. Sections of observed filaments are unstable and appear to be subject to disappearance when a nascent bipolar feature appears in the neutral band. Title: Comparisons of Photospheric Magnetograms and Hα Filtergrams Authors: Rust, David M.; Smith, Sara F. Bibcode: 1969BAAS....1..292R Altcode: No abstract at ADS Title: Two-Dimensional Observations of Solar Oscilating Regions Authors: Musman, Steven A.; Rust, David M. Bibcode: 1969BAAS....1S.287M Altcode: No abstract at ADS Title: Chromospheric Explosions and Satellite Sunspots Authors: Rust, David M. Bibcode: 1968IAUS...35...77R Altcode: No abstract at ADS Title: Magnetic Field Changes during Solar Flares. Authors: Rust, David M. Bibcode: 1968AJS....73S..75R Altcode: Longitudinal magnetic field intensities have been measured during flares in several solar active regions. The observations were made with the Mt. Wilson magnetograph operating on the Fe line at 5250 A. Spacial resolution was 10 sec of arc, and time resolution was 5 to 10 min. Observations of several subflares and Class 1 flares show that magnetic energy losses are comparable with estimated flare energies of about 1030 ergs. The magnetic energy in an active region increases in the half-hour preceeding the flare, and in a similar time just afterward it again increases to roughly the pre-flare value. The conclusion drawn is that flares start in an instable magnetic field configuration which forms as new sunspots rise to the photo- sphere or as established spots change. Observations are presented which show that flares begin near magnetic features that have the polarity opposite to that of the surrounding magnetic fields. These "satellite sunspots" are not always visible in integrated light. The fields of these features weaken simultaneously with flares and with explosive surges. Title: Magnetic Fields in Quiescent Solar Prominences. I. Observations Authors: Rust, David M. Bibcode: 1967ApJ...150..313R Altcode: A new magnetograph, operated on the Ha emission line, has been used to measure the line-of-sight field intensity in nearly 100 quiescent prominences The magnetic sensitivity is 2 gauss The measurement technique is described. The observed prominences were divided into three classes roughly according to their position with respect to active regions. High-latitude ("polar crown") prominences most distant from the current sunspot zone usually showed fields of about 5 gauss. More recently formed prominences near the high-latitude border of fading bipolar magnetic regions also showed 5 gauss fields. The third class, sunspot zone prominences, showed fields up to 60 gauss; however, the median field was only about 8 gauss. The observations of field intensity and polarity indicate that these are determined by the nearby and underlying photospheric fields. The characteristic size of the over-all field structures supporting prominences must be about 50000-100000 km. The pattern of polarities observed in the aged polar crown shows that there is no detectable large scale (Ro) distortion of the lines of force in the solar atmosphere by the differential rotation. Observations at 20" resolution reveal that the horizontal field intensity usually increases with height above the limb. This observed height gradient, aH/az 10- gauss/km, is necessary and sufficient to demonstrate the support of prominences by Lorentz forces. The observations tend to confirm the validity of the theoretical prominence model of Kippenhahn and SchlUter. Title: Measurements of the Magnetic Fields in Quiescent Solar Prominences. Authors: Rust, David Maurice Bibcode: 1966PhDT.........7R Altcode: No abstract at ADS Title: The solar magnetograph of the High Altitude Observatory Authors: Lee, R. H.; Rust, D. M.; Zirin, H. Bibcode: 1965ApOpt...4.1081L Altcode: Available from http://www.opticsInfoBase.org/abstract.cfm?id=13895;