Author name code: golub ADS astronomy entries on 2022-09-14 author:"Golub, Leon" ------------------------------------------------------------------------ Title: Defining the Middle Corona Authors: West, Matthew J.; Seaton, Daniel B.; Wexler, David B.; Raymond, John C.; Del Zanna, Giulio; Rivera, Yeimy J.; Kobelski, Adam R.; DeForest, Craig; Golub, Leon; Caspi, Amir; Gilly, Chris R.; Kooi, Jason E.; Alterman, Benjamin L.; Alzate, Nathalia; Banerjee, Dipankar; Berghmans, David; Chen, Bin; Chitta, Lakshmi Pradeep; Downs, Cooper; Giordano, Silvio; Higginson, Aleida; Howard, Russel A.; Mason, Emily; Mason, James P.; Meyer, Karen A.; Nykyri, Katariina; Rachmeler, Laurel; Reardon, Kevin P.; Reeves, Katharine K.; Savage, Sabrina; Thompson, Barbara J.; Van Kooten, Samuel J.; Viall, Nicholeen M.; Vourlidas, Angelos Bibcode: 2022arXiv220804485W Altcode: The middle corona, the region roughly spanning heliocentric altitudes from $1.5$ to $6\,R_\odot$, encompasses almost all of the influential physical transitions and processes that govern the behavior of coronal outflow into the heliosphere. Eruptions that could disrupt the near-Earth environment propagate through it. Importantly, it modulates inflow from above that can drive dynamic changes at lower heights in the inner corona. Consequently, this region is essential for comprehensively connecting the corona to the heliosphere and for developing corresponding global models. Nonetheless, because it is challenging to observe, the middle corona has been poorly studied by major solar remote sensing missions and instruments, extending back to the Solar and Heliospheric Observatory (SoHO) era. Thanks to recent advances in instrumentation, observational processing techniques, and a realization of the importance of the region, interest in the middle corona has increased. Although the region cannot be intrinsically separated from other regions of the solar atmosphere, there has emerged a need to define the region in terms of its location and extension in the solar atmosphere, its composition, the physical transitions it covers, and the underlying physics believed to be encapsulated by the region. This paper aims to define the middle corona and give an overview of the processes that occur there. Title: The Airborne Infrared Spectrometer: Development, Characterization, and the 2017 August 21 Eclipse Observation Authors: Samra, Jenna E.; Marquez, Vanessa; Cheimets, Peter; DeLuca, Edward E.; Golub, Leon; Hannigan, James W.; Madsen, Chad A.; Vira, Alisha; Adams, Arn Bibcode: 2022AJ....164...39S Altcode: 2021arXiv210509419S On 2017 August 21, the Airborne Infrared Spectrometer (AIR-Spec) observed the total solar eclipse at an altitude of 14 km from aboard the NSF/NCAR Gulfstream V research aircraft. The instrument successfully observed the five coronal emission lines that it was designed to measure: Si X 1.431 μm, S XI 1.921 μm, Fe IX 2.853 μm, Mg VIII 3.028 μm, and Si IX 3.935 μm. Characterizing these magnetically sensitive emission lines is an important first step in designing future instruments to monitor the coronal magnetic field, which drives space weather events, as well as coronal heating, structure, and dynamics. The AIR-Spec instrument includes an image stabilization system, feed telescope, grating spectrometer, and slit-jaw imager. This paper details the instrument design, optical alignment method, image processing, and data calibration approach. The eclipse observations are described and the available data are summarized. Title: Parallel Plasma Loops and the Energization of the Solar Corona Authors: Peter, Hardi; Chitta, Lakshmi Pradeep; Chen, Feng; Pontin, David I.; Winebarger, Amy R.; Golub, Leon; Savage, Sabrina L.; Rachmeler, Laurel A.; Kobayashi, Ken; Brooks, David H.; Cirtain, Jonathan W.; De Pontieu, Bart; McKenzie, David E.; Morton, Richard J.; Testa, Paola; Tiwari, Sanjiv K.; Walsh, Robert W.; Warren, Harry P. Bibcode: 2022ApJ...933..153P Altcode: 2022arXiv220515919P The outer atmosphere of the Sun is composed of plasma heated to temperatures well in excess of the visible surface. We investigate short cool and warm (<1 MK) loops seen in the core of an active region to address the role of field-line braiding in energizing these structures. We report observations from the High-resolution Coronal imager (Hi-C) that have been acquired in a coordinated campaign with the Interface Region Imaging Spectrograph (IRIS). In the core of the active region, the 172 Å band of Hi-C and the 1400 Å channel of IRIS show plasma loops at different temperatures that run in parallel. There is a small but detectable spatial offset of less than 1″ between the loops seen in the two bands. Most importantly, we do not see observational signatures that these loops might be twisted around each other. Considering the scenario of magnetic braiding, our observations of parallel loops imply that the stresses put into the magnetic field have to relax while the braiding is applied: the magnetic field never reaches a highly braided state on these length scales comparable to the separation of the loops. This supports recent numerical 3D models of loop braiding in which the effective dissipation is sufficiently large that it keeps the magnetic field from getting highly twisted within a loop. Title: New Observations of the IR Emission Corona from the 2019 July 2 Eclipse Flight of the Airborne Infrared Spectrometer Authors: Samra, Jenna E.; Madsen, Chad A.; Cheimets, Peter; DeLuca, Edward E.; Golub, Leon; Marquez, Vanessa; Reyes, Naylynn Tañón Bibcode: 2022ApJ...933...82S Altcode: 2021arXiv210608760S The Airborne Infrared Spectrometer (AIR-Spec) was commissioned during the 2017 total solar eclipse, when it observed five infrared coronal emission lines from a Gulfstream V research jet owned by the National Science Foundation and operated by the National Center for Atmospheric Research. The second AIR-Spec research flight took place during the 2019 July 2 total solar eclipse across the south Pacific. The 2019 eclipse flight resulted in seven minutes of observations, during which the instrument measured all four of its target emission lines: S XI 1.393 μm, Si X 1.431 μm, S XI 1.921 μm, and Fe IX 2.853 μm. The 1.393 μm S XI line was detected for the first time, and probable first detections were made of Si XI 1.934 μm and Fe X 1.947 μm. The 2017 AIR-Spec detection of Fe IX was confirmed and the first observations were made of the Fe IX line intensity as a function of solar radius. Telluric absorption features were used to calibrate the wavelength mapping, instrumental broadening, and throughput of the instrument. AIR-Spec underwent significant upgrades in preparation for the 2019 eclipse observation. The thermal background was reduced by a factor of 30, providing a 5.5× improvement in signal-to-noise ratio, and the postprocessed pointing stability was improved by a factor of 5 to <10″ rms. In addition, two imaging artifacts were identified and resolved, improving the spectral resolution and making the 2019 data easier to interpret. Title: Real-Time Solar Flare Predictions for Improved Flare Observations Authors: Vievering, J. T.; Athiray, P. S.; Buitrago-Casas, J. C.; Chamberlin, P.; Glesener, L.; Golub, L.; Knoer, V.; Krucker, S.; Machol, J.; Pantazides, A.; Peck, C.; Reeves, K.; Savage, S.; Schmit, D.; Smith, B.; Vigil, G.; Winebarger, A. Bibcode: 2022heli.conf.4038V Altcode: Improving near-term flare forecasts is important for observatories targeting flare physics that are restricted in FOV and/or observing time. We propose a tool that aggregates near-real-time signatures of flare onset to provide early flare predictions. Title: Probing the Physics of the Solar Atmosphere with the Multi-slit Solar Explorer (MUSE). II. Flares and Eruptions Authors: Cheung, Mark C. M.; Martínez-Sykora, Juan; Testa, Paola; De Pontieu, Bart; Chintzoglou, Georgios; Rempel, Matthias; Polito, Vanessa; Kerr, Graham S.; Reeves, Katharine K.; Fletcher, Lyndsay; Jin, Meng; Nóbrega-Siverio, Daniel; Danilovic, Sanja; Antolin, Patrick; Allred, Joel; Hansteen, Viggo; Ugarte-Urra, Ignacio; DeLuca, Edward; Longcope, Dana; Takasao, Shinsuke; DeRosa, Marc L.; Boerner, Paul; Jaeggli, Sarah; Nitta, Nariaki V.; Daw, Adrian; Carlsson, Mats; Golub, Leon; The Bibcode: 2022ApJ...926...53C Altcode: 2021arXiv210615591C Current state-of-the-art spectrographs cannot resolve the fundamental spatial (subarcseconds) and temporal (less than a few tens of seconds) scales of the coronal dynamics of solar flares and eruptive phenomena. The highest-resolution coronal data to date are based on imaging, which is blind to many of the processes that drive coronal energetics and dynamics. As shown by the Interface Region Imaging Spectrograph for the low solar atmosphere, we need high-resolution spectroscopic measurements with simultaneous imaging to understand the dominant processes. In this paper: (1) we introduce the Multi-slit Solar Explorer (MUSE), a spaceborne observatory to fill this observational gap by providing high-cadence (<20 s), subarcsecond-resolution spectroscopic rasters over an active region size of the solar transition region and corona; (2) using advanced numerical models, we demonstrate the unique diagnostic capabilities of MUSE for exploring solar coronal dynamics and for constraining and discriminating models of solar flares and eruptions; (3) we discuss the key contributions MUSE would make in addressing the science objectives of the Next Generation Solar Physics Mission (NGSPM), and how MUSE, the high-throughput Extreme Ultraviolet Solar Telescope, and the Daniel K Inouye Solar Telescope (and other ground-based observatories) can operate as a distributed implementation of the NGSPM. This is a companion paper to De Pontieu et al., which focuses on investigating coronal heating with MUSE. Title: Probing the Physics of the Solar Atmosphere with the Multi-slit Solar Explorer (MUSE). I. Coronal Heating Authors: De Pontieu, Bart; Testa, Paola; Martínez-Sykora, Juan; Antolin, Patrick; Karampelas, Konstantinos; Hansteen, Viggo; Rempel, Matthias; Cheung, Mark C. M.; Reale, Fabio; Danilovic, Sanja; Pagano, Paolo; Polito, Vanessa; De Moortel, Ineke; Nóbrega-Siverio, Daniel; Van Doorsselaere, Tom; Petralia, Antonino; Asgari-Targhi, Mahboubeh; Boerner, Paul; Carlsson, Mats; Chintzoglou, Georgios; Daw, Adrian; DeLuca, Edward; Golub, Leon; Matsumoto, Takuma; Ugarte-Urra, Ignacio; McIntosh, Scott W.; the MUSE Team Bibcode: 2022ApJ...926...52D Altcode: 2021arXiv210615584D The Multi-slit Solar Explorer (MUSE) is a proposed mission composed of a multislit extreme ultraviolet (EUV) spectrograph (in three spectral bands around 171 Å, 284 Å, and 108 Å) and an EUV context imager (in two passbands around 195 Å and 304 Å). MUSE will provide unprecedented spectral and imaging diagnostics of the solar corona at high spatial (≤0.″5) and temporal resolution (down to ~0.5 s for sit-and-stare observations), thanks to its innovative multislit design. By obtaining spectra in four bright EUV lines (Fe IX 171 Å, Fe XV 284 Å, Fe XIX-Fe XXI 108 Å) covering a wide range of transition regions and coronal temperatures along 37 slits simultaneously, MUSE will, for the first time, "freeze" (at a cadence as short as 10 s) with a spectroscopic raster the evolution of the dynamic coronal plasma over a wide range of scales: from the spatial scales on which energy is released (≤0.″5) to the large-scale (~170″ × 170″) atmospheric response. We use numerical modeling to showcase how MUSE will constrain the properties of the solar atmosphere on spatiotemporal scales (≤0.″5, ≤20 s) and the large field of view on which state-of-the-art models of the physical processes that drive coronal heating, flares, and coronal mass ejections (CMEs) make distinguishing and testable predictions. We describe the synergy between MUSE, the single-slit, high-resolution Solar-C EUVST spectrograph, and ground-based observatories (DKIST and others), and the critical role MUSE plays because of the multiscale nature of the physical processes involved. In this first paper, we focus on coronal heating mechanisms. An accompanying paper focuses on flares and CMEs. Title: A Strategy for a Coherent and Comprehensive Basis for Understanding the Middle Corona Authors: West, M. J.; Seaton, D. B.; Alzate, N.; Caspi, A.; DeForest, C. E.; Gilly, C. R.; Golub, L.; Higginson, A. K.; Kooi, J. E.; Mason, J. P.; Rachmeler, L. A.; Reeves, K. K.; Reardon, K.; Rivera, Y. J.; Savage, S.; Viall, N. M.; Wexler, D. B. Bibcode: 2022heli.conf.4060W Altcode: We describe a strategy for coherent and comprehensive observations needed to achieve a fundamental understanding of the middle solar corona. Title: The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) Authors: Champey, P. R.; Winebarger, A. R.; Kobayashi, K.; Athiray, P. S.; Hertz, E.; Savage, S.; Beabout, B.; Beabout, D.; Broadway, D.; Bruccoleri, A. R.; Cheimets, P.; Davis, J.; Duffy, J.; Golub, L.; Gregory, D. A.; Griffith, C.; Haight, H.; Heilmann, R. K.; Hogue, B.; Hohl, J.; Hyde, D.; Kegley, J.; Kolodzieczjak, J.; Ramsey, B.; Ranganathan, J.; Robertson, B.; Schattenburg, M. L.; Speegle, C. O.; Vigil, G.; Walsh, R.; Weddenorf, B.; Wright, E. Bibcode: 2022JAI....1150010C Altcode: The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) is a sounding rocket instrument that flew on July 30, 2021 from the White Sands Missile Range, NM. The instrument was designed to address specific science questions that require differential emission measures of the solar soft X-ray spectrum from 6 - 25Å(0.5 - 2.1keV). MaGIXS comprises a Wolter-I telescope, a slit-jaw imaging system, an identical pair of grazing incidence paraboloid mirrors, a planar grating and a CCD camera. While implementing this design, some limitations were encountered in the production of the X-ray mirrors, which ended up as a catalyst for the development of a deterministic polishing approach and an improved meteorological technique that utilizes a computer-generated hologram (CGH). The opto-mechanical design approach addressed the need to have adjustable and highly repeatable interfaces to allow for the complex alignment between the optical sub-assemblies. The alignment techniques employed when mounting the mirrors and throughout instrument integration and end-to-end testing are discussed. Also presented are spatial resolution measurements of the end-to-end point-spread-function that were obtained during testing in the X-ray Cryogenic Facility (XRCF) at NASA Marshall Space Flight Center. Lastly, unresolved issues and off-nominal performance are discussed. Title: Probing the Physics of the Solar Atmosphere with the Multi-slit Solar Explorer (MUSE): II. Flares and Eruptions Authors: Cheung, Chun Ming Mark; Martinez-Sykora, Juan; Testa, Paola; De Pontieu, Bart; Chintzoglou, Georgios; Rempel, Matthias; Polito, Vanessa; Kerr, Graham; Reeves, Katharine; Fletcher, Lyndsay; Jin, Meng; Nobrega, Daniel; Danilovic, Sanja; Antolin, Patrick; Allred, Joel; Hansteen, Viggo; Ugarte-Urra, Ignacio; DeLuca, Edward; Longcope, Dana; Takasao, Shinsuke; DeRosa, Marc; Boerner, Paul; Jaeggli, Sarah; Nitta, Nariaki; Daw, Adrian; Carlsson, Mats; Golub, Leon Bibcode: 2021AGUFMSH51A..08C Altcode: Current state-of-the-art spectrographs cannot resolve the fundamental spatial (sub-arcseconds) and temporal scales (less than a few tens of seconds) of the coronal dynamics of solar flares and eruptive phenomena. The highest resolution coronal data to date are based on imaging, which is blind to many of the processes that drive coronal energetics and dynamics. As shown by IRIS for the low solar atmosphere, we need high-resolution spectroscopic measurements with simultaneous imaging to understand the dominant processes. In this paper: (1) we introduce the Multi-slit Solar Explorer (MUSE), a spaceborne observatory to fill this observational gap by providing high-cadence (<20 s), sub-arcsecond resolution spectroscopic rasters over an active region size of the solar transition region and corona; (2) using advanced numerical models, we demonstrate the unique diagnostic capabilities of MUSE for exploring solar coronal dynamics, and for constraining and discriminating models of solar flares and eruptions; (3) we discuss the key contributions MUSE would make in addressing the science objectives of the Next Generation Solar Physics Mission (NGSPM), and how MUSE, the high-throughput EUV Solar Telescope (EUVST) and the Daniel K Inouye Solar Telescope (and other ground-based observatories) can operate as a distributed implementation of the NGSPM. This is a companion paper to De Pontieu et al. (2021, also submitted to SH-17), which focuses on investigating coronal heating with MUSE. Title: The Multiview Observatory for Solar Terrestrial Science (MOST) Authors: Gopalswamy, Nat; Kucera, Therese; Leake, James; MacDowall, Robert; Wilson, Lynn; Kanekal, Shrikanth; Shih, Albert; Christe, Steven; Gong, Qian; Viall, Nicholeen; Tadikonda, Sivakumar; Fung, Shing; Yashiro, Seiji; Makela, Pertti; Golub, Leon; DeLuca, Edward; Reeves, Katharine; Seaton, Daniel; Savage, Sabrina; Winebarger, Amy; DeForest, Craig; Desai, Mihir; Bastian, Tim; Lazio, Joseph; Jensen, P. E., C. S. P., Elizabeth; Manchester, Ward; Wood, Brian; Kooi, Jason; Wexler, David; Bale, Stuart; Krucker, Sam; Hurlburt, Neal; DeRosa, Marc; Pevtsov, Alexei; Tripathy, Sushanta; Jain, Kiran; Gosain, Sanjay; Petrie, Gordon; Kholikov, Shukirjon; Zhao, Junwei; Scherrer, Philip; Woods, Thomas; Chamberlin, Philip; Kenny, Megan Bibcode: 2021AGUFMSH12A..07G Altcode: The Multiview Observatory for Solar Terrestrial Science (MOST) is a comprehensive mission concept targeting the magnetic coupling between the solar interior and the heliosphere. The wide-ranging imagery and time series data from MOST will help understand the solar drivers and the heliospheric responses as a system, discerning and tracking 3D magnetic field structures, both transient and quiescent in the inner heliosphere. MOST will have seven remote-sensing and three in-situ instruments: (1) Magnetic and Doppler Imager (MaDI) to investigate surface and subsurface magnetism by exploiting the combination of helioseismic and magnetic-field measurements in the photosphere; (2) Inner Coronal Imager in EUV (ICIE) to study large-scale structures such as active regions, coronal holes and eruptive structures by capturing the magnetic connection between the photosphere and the corona to about 3 solar radii; (3) Hard X-ray Imager (HXI) to image the non-thermal flare structure; (4) White-light Coronagraph (WCOR) to seamlessly study transient and quiescent large-scale coronal structures extending from the ICIE field of view (FOV); (5) Faraday Effect Tracker of Coronal and Heliospheric structures (FETCH), a novel radio package to determine the magnetic field structure and plasma column density, and their evolution within 0.5 au; (6) Heliospheric Imager with Polarization (HIP) to track solar features beyond the WCOR FOV, study their impact on Earth, and provide important context for FETCH; (7) Radio and Plasma Wave instrument (M/WAVES) to study electron beams and shocks propagating into the heliosphere via passive radio emission; (8) Solar High-energy Ion Velocity Analyzer (SHIVA) to determine spectra of electrons, and ions from H to Fe at multiple spatial locations and use energetic particles as tracers of magnetic connectivity; (9) Solar Wind Magnetometer (MAG) to characterize magnetic structures at 1 au; (10) Solar Wind Plasma Instrument (SWPI) to characterize plasma structures at 1 au. MOST will have two large spacecraft with identical payloads deployed at L4 and L5 and two smaller spacecraft ahead of L4 and behind L5 to carry additional FETCH elements. MOST will build upon SOHO and STEREO achievements to expand the multiview observational approach into the first half of the 21st Century. Title: Preliminary Results from the Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) Authors: Winebarger, Amy; Savage, Sabrina; Kobayashi, Ken; Champey, Patrick; Golub, Leon; Walsh, Robert; Athiray, P. S.; Bradshaw, Stephen; Cheimets, Peter; Cirtain, Jonathan; DeLuca, Edward; Del Zanna, Giulio; Mason, Helen; McKenzie, David; Ramsey, Brian; Reeves, Katharine; Testa, Paola; Vigil, Genevieve; Warren, Harry Bibcode: 2021AGUFMSH51A..06W Altcode: Coronal heating mechanisms are notoriously difficult to constrain with current observations. We present new observations from an instrument designed to measure a critical diagnostic of the frequency heating events in active regions. The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) is a sounding rocket mission that aims to observe the soft x-ray solar spectrum (0.6 2.5 nm) with both spatial and spectral resolution. This wavelength range has several high temperature and abundance diagnostics that can be used to infer the coronal heating frequency. MaGIXS will observe the Sun through a 12 x 33 slot, producing ``overlappograms, where the spatial and spectral information are overlapped and must be unfolded. In this presentation, I will report on the MaGIXS launch and data collection and provide preliminary analysis of MaGIXS observations. Title: Exploring the middle corona: new instrumentation to address science questions critical to understanding the thermal structure and dynamic evolution of the middle corona Authors: DeLuca, Edward; Winebarger, Amy; Reeves, Katharine; Golub, Leon; Samra, Jenna; Madsen, Chad; Rivera, Yeimy; Karna, Nishu; Savage, Sabrina; Seaton, Daniel; West, Matthew; Downs, Cooper; Del Zanna, Giulio Bibcode: 2021AGUFMSH25F2150D Altcode: The global structure of the largely unexplored middle corona determines the physical properties of the inner heliosphere, affects the formation and acceleration of the solar wind, and controls the dynamics of eruptive events. Tracing the short and long term global evolution of the extended corona, identifying changes in corona/heliosphere connectivity and following the dynamic evolution of eruptive events in this unexplored region will provide observational data that will clarify how the corona transitions from closed to open, illuminate the genesis of coronal mass ejections, and provide input for the design of the next generation of physics based space weather forecasts. This poster outlines several critical science questions and identifies the measurements that are required to make substantial progress towards addressing the questions. We review and discuss the instrumentation necessary to capture the observations needed for meaningful progress in this area as well as the role of simulations in the interpretation of the observations. Title: Calibration of the Marshall Grazing Incidence X-Ray Spectrometer Experiment. II. Flight Instrument Calibration Authors: Athiray, P. S.; Winebarger, Amy R.; Champey, Patrick; Kobayashi, Ken; Savage, Sabrina; Beabout, Brent; Beabout, Dyana; Broadway, David; Bruccoleri, Alexander R.; Cheimets, Peter; Golub, Leon; Gullikson, Eric; Haight, Harlan; Heilmann, Ralf K.; Hertz, Edward; Hogue, William; Johnson, Steven; Kegley, Jeffrey; Kolodziejczak, Jeffery; Madsen, Chad; Schattenburg, Mark L.; Siler, Richard; Vigil, Genevieve D.; Wright, Ernest Bibcode: 2021ApJ...922...65A Altcode: The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) is a sounding rocket experiment that observes the soft X-ray spectrum of the Sun from 6.0-24 Å (0.5-2.0 keV), successfully launched on 2021 July 30. End-to-end alignment of the flight instrument and calibration experiments are carried out using the X-ray and Cryogenic Facility at NASA Marshall Space Flight Center. In this paper, we present the calibration experiments of MaGIXS, which include wavelength calibration, measurement of line spread function, and determination of effective area. Finally, we use the measured instrument response function to predict the expected count rates for MaGIXS flight observation looking at a typical solar active region. Title: Calibration of the MaGIXS experiment II: Flight Instrument Calibration Authors: Athiray, P. S.; Winebarger, Amy R.; Champey, Patrick; Kobayashi, Ken; Savage, Sabrina; Beabout, Brent; Beabout, Dyana; Broadway, David; Bruccoleri, Alexander R.; Cheimets, Peter; Golub, Leon; Gullikson, Eric; Haight, Harlan; Heilmann, Ralf K.; Hertz, Edward; Hogue, William; Johnson, Steven; Kegley, Jeffrey; Kolodziejczak, Jeffery; Madsen, Chad; Schattenburg, Mark L.; Siler, Richard; Vigil, Genevieve D.; Wright, Ernest Bibcode: 2021arXiv210901720A Altcode: The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) is a sounding rocket experiment that observes the soft X-ray spectrum of the Sun from 6.0 - 24 Angstrom (0.5 - 2.0 keV), successfully launched on 30 July 2021. End-to-end alignment of the flight instrument and calibration experiments are carried out using the X-ray and Cryogenic Facility (XRCF) at NASA Marshall Space Flight Center. In this paper, we present the calibration experiments of MaGIXS, which include wavelength calibration, measurement of line spread function, and determination of effective area. Finally, we use the measured instrument response function to predict the expected count rates for MaGIXS flight observation looking at a typical solar active region Title: The First Solar Flare Sounding Rocket Campaign and Its Potential Impacts for High Energy Solar Instrumentation Authors: Savage, S.; Winebarger, A.; Glesener, L.; Golub, L.; Chamberlin, P.; Hi-C Flare Team; Foxsi-4 Team; Snifs Team Bibcode: 2021AAS...23831315S Altcode: Solar flares are an essential driver of space weather as they account for the rapid release of powerful amounts of energy (~1032 ergs) in a matter of seconds to hours. Observations from the past several decades have yielded a wealth of understanding of these events while at the same time presenting countless new questions. Key gaps in our knowledge remain that cannot be satisfactorily answered with available instrumentation, and we are now at the precipice of the value of incremental improvements in technology versus the need for design breakthroughs. The latter requires exceptional testing in order to justify vast investments within Explorer-class mission programs. High energy instrumentation often invokes the additional requirement of testing above the absorption layer of the Earth's atmosphere. The NASA sounding rocket program has been an invaluable pathway for developing such cutting-edge technologies. However, these suborbital missions have been severely limited for the development of flare-specific instrumentation due to the current inability to remain in a holding pattern until a flare occurs at the White Sands Missile Range (~1 hour) compounded by the short duration of a flight (~5 minutes of science observations) in which it is nearly impossible to capture a flare per chance. In response to this deficiency, a pilot solar flare campaign has been established to test the ability to launch multiple sounding rockets (two nearly simultaneously) with instrumentation optimized to observe flares from the Poker Flat Research Range in Alaska, taking advantage of the site's ability to accommodate a long holding pattern (~4 hours per day for several weeks). This capability has been utilized extensively by the geospace communities. We present an overview of the first three payloads participating in this pilot program, Hi-C Flare, FOXSI 4, and SNIFS, and discuss how this new technology development paradigm could enable the next wave of exploratory flare missions. Title: Marshall Grazing Incidence X-ray Spectrometer Slitjaw Imager Implementation and Performance Authors: Vigil, Genevieve D.; Winebarger, Amy R.; Kobayashi, Ken; Cheimets, Peter N.; Champey, Patrick R.; Savage, Sabrina L.; Golub, Leon; Watkinson, Benjamin; Beabout, Brent; Weddendorf, Bruce; Walsh, Robert W. Bibcode: 2021SoPh..296...90V Altcode: The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) is a slit spectrograph designed to fly on a sounding-rocket and to observe the Sun in soft X-rays (SXRs) to determine the frequency of coronal heating events. The MaGIXS wavelength range (≈ 0.6 - 2.5 nm) has a significant number of diagnostic lines formed at coronal temperatures, but developing SXR instrumentation presents several challenges, including how to efficiently perform context imaging. A slitjaw image is required for pointing the instrument during flight and for co-alignment with coordinated data sets after flight, but operating in the SXR regime implies that a simple normal-incidence optical system could not be employed to image the same wavelength range as the spectrograph. Therefore, to avoid the complexity of additional grazing-incidence optics, the MaGIXS slitjaw system is designed to image in the extreme ultraviolet (EUV) between roughly 20 - 80 nm. The temperature sensitivity of this EUV bandpass will observe complementary features visible to the MaGIXS instrument. The image on the slitjaw is then converted, via a phosphor coating, to readily detectable visible light. Presented here is the design, implementation, and characterization of the MaGIXS slitjaw imaging system. The slitjaw instrument is equipped with an entrance filter that passes EUV light, along with X-rays, onto the slit, exciting a fluorescent coating and causing it to emit in the visible. This visible light can then be imaged by a simple implementation of commercial off-the-shelf (COTS) optics and low-light camera. Such a design greatly reduces the complexity of implementing and testing the slitjaw imager for an X-ray instrument system and will accomplish the pointing and co-alignment requirements for MaGIXS. Title: Physical Characteristics of Unstructured Coronal Clouds Authors: Asgari-Targhi, M.; Golub, L.; Hahn, M.; Karna, N.; Savin, D. W. Bibcode: 2021ApJ...910..113A Altcode: Active regions in the inner solar corona, when observed in X-ray emission, consist of bright, hot loops surrounded by unstructured clouds. The emission from the clouds extends to a height of ≍4-5 × 104 km at temperatures of ≍2-3 MK. These "hot clouds" are variable, but persist for many days and do not appear to connect directly to the active region streamers or other large-scale structures observed higher in the corona. We present an observational analysis of these diffuse structures to establish basic plasma parameters such as magnetic field strength, particle density, and temperature. The values of β, the ratio of the plasma pressure to the magnetic field pressure, were found to be generally less than unity, though often approaching unity in the upper portions of the active region, where the hot clouds are located. The magnetic field may therefore only partially confine these regions and inhibit flare-like instabilities that could otherwise be driven by gradients of plasma pressure and current density. Title: High resolution soft X-ray spectroscopy and the quest for the hot (5-10 MK) plasma in solar active regions Authors: Del Zanna, Giulio; Andretta, Vincenzo; Cargill, Peter J.; Corso, Alain J.; Daw, Adrian N.; Golub, Leon; Klimchuk, James A.; Mason, Helen E. Bibcode: 2021FrASS...8...33D Altcode: 2021arXiv210306156D We discuss the diagnostics available to study the 5--10 MK plasma in the solar corona, which is key to understanding the heating in the cores of solar active regions. We present several simulated spectra, and show that excellent diagnostics are available in the soft X-rays, around 100 Angstroms, as six ionisation stages of Fe can simultaneously be observed, and electron densities derived, within a narrow spectral region. As this spectral range is almost unexplored, we present an analysis of available and simulated spectra, to compare the hot emission with the cooler component. We adopt recently designed multilayers to present estimates of count rates in the hot lines, with a baseline spectrometer design. Excellent count rates are found, opening up the exciting opportunity to obtain high-resolution spectroscopy of hot plasma. Title: Imaging Evidence for Solar Wind Outflows Originating from a Coronal Mass Ejection Footpoint Authors: Lörinčík, Juraj; Dudík, Jaroslav; Aulanier, Guillaume; Schmieder, Brigitte; Golub, Leon Bibcode: 2021ApJ...906...62L Altcode: 2020arXiv201004250L We report on Atmospheric Imaging Assembly observations of plasma outflows originating in a coronal dimming during a 2015 April 28 filament eruption. After the filament started to erupt, two flare ribbons formed, one of which had a well-visible hook enclosing a core (twin) dimming region. Along multiple funnels located in this dimming, a motion of plasma directed outward started to be visible in the 171 and 193 Å filter channels of the instrument. In time-distance diagrams, this motion generated a strip-like pattern, which lasted for more than 5 hr and whose characteristics did not change along the funnel. We therefore suggest the motion is a signature of outflows corresponding to velocities ranging between ≍70 and 140 km s-1. Interestingly, the pattern of the outflows and their velocities were found to be similar to those we observed in a neighboring ordinary coronal hole. Therefore, the outflows were most likely a signature of a coronal mass ejection-induced solar wind flowing along the open-field structures rooted in the dimming region. Further, the evolution of the hook encircling the dimming region was examined in the context of the latest predictions imposed for 3D magnetic reconnection. The observations indicate that the filament's footpoints were, during their transformation to the dimming region, reconnecting with surrounding canopies. To our knowledge, our observations present the first imaging evidence for outflows of plasma from a dimming region. Title: The First Solar Flare Sounding Rocket Campaign and Its Potential Impacts for High Energy Solar Instrumentation Authors: Savage, S. L.; Winebarger, A. R.; Glesener, L.; Reeves, K.; Kobayashi, K.; Golub, L. Bibcode: 2020AGUFMSH056..02S Altcode: Solar flares are an essential driver of space weather as they account for the rapid release of powerful amounts of energy (~1032 ergs) in a matter of seconds to hours. Observations from the past several decades have yielded a wealth of understanding of these events while at the same time presenting countless new questions. Key gaps in our knowledge remain that cannot be satisfactorily answered with available instrumentation, and we are now at the precipice of the value of incremental improvements in technology versus the need for design breakthroughs. The latter requires exceptional testing in order to justify vast investments within Explorer-class mission programs. High energy instrumentation often invokes the additional requirement of testing above the absorption layer of the Earth's atmosphere. The NASA sounding rocket program has been an invaluable pathway for developing such cutting-edge technologies. However, these suborbital missions have been severely limited for the development of flare-specific instrumentation due to the current inability to remain in a holding pattern until a flare occurs at the White Sands Missile Range (~1 hour) compounded by the short duration of a flight (~5 minutes of science observations) in which it is nearly impossible to capture a flare per chance. In response to this deficiency, a pilot solar flare campaign has been established to test the ability to launch at least two sounding rockets with instrumentation optimized to observe flares from the Poker Flats Research Range in Alaska, taking advantage of the site's ability to accommodate a long holding pattern (~4 hours per day for several weeks). This capability has been utilized extensively by the geospace communities. We will present the first two payloads selected specifically for this solar pilot program, Hi-C FLARE and FOXSI 4, and discuss how this new technology development paradigm could enable the next wave of exploratory flare missions. Title: Updates on the Fundamentals of Impulsive Energy Release in the Corona Explorer (FIERCE) mission concept Authors: Shih, A. Y.; Glesener, L.; Krucker, S.; Guidoni, S. E.; Christe, S.; Reeves, K.; Gburek, S.; Caspi, A.; Alaoui, M.; Allred, J. C.; Battaglia, M.; Baumgartner, W.; Dennis, B. R.; Drake, J. F.; Goetz, K.; Golub, L.; Hannah, I. G.; Hayes, L.; Holman, G.; Inglis, A.; Ireland, J.; Kerr, G. S.; Klimchuk, J. A.; McKenzie, D. E.; Moore, C. S.; Musset, S.; Reep, J. W.; Ryan, D.; Saint-Hilaire, P.; Savage, S. L.; Schwartz, R.; Seaton, D. B.; Steslicki, M.; Woods, T. N. Bibcode: 2020AGUFMSH0480012S Altcode: The Fundamentals of Impulsive Energy Release in the Corona Explorer ( FIERCE ) Medium-Class Explorer (MIDEX) mission concept addresses the following science questions:

What are the physical origins of space-weather events?

How are particles accelerated at the Sun?

How is impulsively released energy transported throughout the solar atmosphere?

How is the solar corona heated?

FIERCE achieves its science objectives through co-optimized X-ray and extreme ultraviolet (EUV) observations by the following instruments:

FOXSI, a focusing hard X-ray spectroscopic imager that is able to capture the full range of emission in flares and CMEs (e.g., faint coronal sources near bright chromospheric sources)

THADIS, a high-resolution, fast-cadence EUV imager that will not saturate for even intense flares to follow dynamic changes in the configuration of plasma structures

STC, a soft X-ray spectrometer that provides detailed thermal and elemental composition diagnostics

If selected, FIERCE will launch in 2025, near the peak of the next solar cycle, which is also well timed with perihelia of Parker Solar Probe and Solar Orbiter . We describe the status and latest updates of the mission concept since it was proposed to NASA last year. We also highlight the anticipated science return from co-observations with other observatories/instruments such as the Expanded Owens Valley Solar Array (EOVSA) or the STIX instrument on Solar Orbiter . Title: Alignment of the Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) telescope mirror and spectrometer optics assemblies Authors: Hertz, Edward; Cheimets, Peter; Hohl, Jacob; Samra, Jenna; Marquez, Vanessa; Winebarger, Amy; Champey, Patrick; Kobayashi, Ken; Savage, Sabrina; Golub, Leon; Bruccoleri, Alexander R.; Heilmann, Ralf K.; Schattenburg, Mark L.; Ramsey, Brian Bibcode: 2020SPIE11444E..8AH Altcode: The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) is a NASA sounding rocket instrument designed and built to observe X-ray emissions from the Sun's atmosphere in the 6-24Å (0.5-2.0keV) range while achieving high spectral and spatial resolution along a 8-arcminute long slit. We describe the alignment process and discuss the results achieved for assembling the Telescope Mirror Assembly (TMA) and the Spectrometer Optics Assembly (SOA) prior to final integration into the MaGIXS instrument. The MaGIXS mirrors are full shell, electroformed nickel replicated on highly polished mandrels at the Marshall Space Flight Center (MSFC). The TMA carries a single shell, Wolter Type-1 mirror pair (primary and secondary) formed on a common mandrel. The SOA includes a matched pair of identical parabolic mirrors and a planar varied-line spacing (VLS) diffraction grating. We performed the subassembly alignment and mounting at the Smithsonian Astrophysical Observatory (SAO) using metrology and precision positioning systems constructed around the Centroid Detector Assembly (CDA), originally built for the alignment of the Chandra mirror shells. The MaGIXS instrument launch has been postponed until 2021 due to the COVID-19 pandemic. Title: The LUCI instrument Authors: West, M. J.; Kintziger, C.; Haberreiter, M.; Berghmans, D.; Gissot, S.; Golub, L.; Shestov, S.; Davies, J. A.; Luntama, J. P. Bibcode: 2020AGUFMSH0300007W Altcode: LUCI (Lagrange eUv Coronal Imager) is a solar imager in the Extreme UltraViolet (EUV) that is being developed as part of the Lagrange mission, a mission designed to be positioned at the L5 Lagrangian point to monitor space weather from its source on the Sun, through the heliosphere, to the Earth. LUCI will provide solar coronal images at a 2-3 minute cadence in a pass-band centred on 19.5 nm. Observations made through this pass-band allow for the detection and monitoring of semi-static coronal structures such as coronal holes, prominences, and active regions; as well as transient phenomena such as solar flares, limb Coronal Mass Ejections (CMEs), EUV waves, and coronal dimmings.

In this presentation I will discuss LUCI's latest design characteristics and the rationale behind several of the design decisions. I will present the observational advantages for space-weather monitoring from the L5 point, especially with an instrument such as LUCI, which will have a novel off-axis 'wide' field-of-view, designed to observe the solar disk extending out in to the middle corona, close to the the Sun-Earth line. I will present proxy data highlighting structures that can be seen in this region and the current roadmap for the instrument development. Title: The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) solar sounding rocket campaign - Calibration and performance Authors: Athiray, P. S.; Winebarger, A. R.; Champey, P. R.; Kobayashi, K.; Savage, S. L.; Vigil, G. D.; Beabout, B.; Beabout, D.; Cheimets, P.; Hertz, E.; Golub, L. Bibcode: 2020AGUFMSH0480008A Altcode: The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) is a sounding rocket experiment that is designed to observe, for the first time, soft X-ray spectra of high-temperature, low-emission plasma of coronal structures spatially resolved along a narrow slit. MaGIXS observation involves a set of high temperature spectral lines in soft X-rays from 0.5 - 2.0 keV from an active region core, which will extend the DEM coverage from 3MK to 10MK constraining the slope of the DEM fall-off. The novel instrument design includes a Wolter-I type telescope and a 3-optic grazing-incidence spectrometer. The spectrometer consists of a finite conjugate mirror pair and a blazed planar, varied line spaced grating, which disperses the rays on to a CCD and provides a high spatial and spectral resolution. Component level instrument testing, integration of the instrument and end-to-end X-ray calibration are carried out using the X-ray and Cryogenic Facility (XRCF) at NASA Marshall Space Flight Center. MaGIXS is scheduled for launch in 2021. We will present the results of X-ray calibration tests for MaGIXS and discuss the expected inflight performance through different solar observation scenarios. Title: Space Weather, Extreme Ultraviolet Instruments and the Multithermal Corona Authors: Golub, L.; DeLuca, E.; Reeves, K. Bibcode: 2020AGUFMSH0300004G Altcode: Observation of the solar corona from Earth orbit or from other locations such as L1 or L5 using suitably-chosen Extreme UltraViolet (EUV) wavelengths offers the possibility of addressing two major goals that will improve our ability to forecast and predict geoeffective space weather events: 1.) improve our understanding of the coronal conditions that control the opening and closing of the corona to the heliosphere and consequent solar wind streams, and 2.) improve our understanding of the physical processes that control the early evolution of CMEs and the formation of shocks from the solar surface out to beyond the nominal source surface. The time-varying solar corona is structured not only in space and in time but also in temperature. A method for efficiently observing multiple wavelengths, thereby recording emission lines formed at different temperatures, simultaneously is therefore desirable. These observations are especially necessary for CME detection, as the departing magnetized plasma shows markedly different structures at different temperatures and even the detectability of the event varies dramatically at different EUV wavelengths. EUV measurements can help to: i.) determine coronal structuring from its roots out to beyond 2.5 R_s; ii.) measure the changes in coronal connectivity; iii.) distinguish between and test solar wind models; iv.) establish the impact of pre-existing coronal structures on CME evolution; v.) confront theories of SEP acceleration and preconditioning; and vi.) establish the extent of energy release behind CMEs. Title: LUCI onboard Lagrange, the next generation of EUV space weather monitoring Authors: West, Matthew J.; Kintziger, Christian; Haberreiter, Margit; Gyo, Manfred; Berghmans, David; Gissot, Samuel; Büchel, Valeria; Golub, Leon; Shestov, Sergei; Davies, Jackie A. Bibcode: 2020JSWSC..10...49W Altcode: 2020arXiv200904788W Lagrange eUv Coronal Imager (LUCI) is a solar imager in the Extreme UltraViolet (EUV) that is being developed as part of the Lagrange mission, a mission designed to be positioned at the L5 Lagrangian point to monitor space weather from its source on the Sun, through the heliosphere, to the Earth. LUCI will use an off-axis two mirror design equipped with an EUV enhanced active pixel sensor. This type of detector has advantages that promise to be very beneficial for monitoring the source of space weather in the EUV. LUCI will also have a novel off-axis wide field-of-view, designed to observe the solar disk, the lower corona, and the extended solar atmosphere close to the Sun-Earth line. LUCI will provide solar coronal images at a 2-3 min cadence in a pass-band centred on 19.5. Observations made through this pass-band allow for the detection and monitoring of semi-static coronal structures such as coronal holes, prominences, and active regions; as well as transient phenomena such as solar flares, limb coronal mass ejections (CMEs), EUV waves, and coronal dimmings. The LUCI data will complement EUV solar observations provided by instruments located along the Sun-Earth line such as PROBA2-SWAP, SUVI-GOES and SDO-AIA, as well as provide unique observations to improve space weather forecasts. Together with a suite of other remote-sensing and in-situ instruments onboard Lagrange, LUCI will provide science quality operational observations for space weather monitoring. Title: EUV imaging and spectroscopy for improved space weather forecasting Authors: Golub, Leon; Cheimets, Peter; DeLuca, Edward E.; Madsen, Chad A.; Reeves, Katharine K.; Samra, Jenna; Savage, Sabrina; Winebarger, Amy; Bruccoleri, Alexander R. Bibcode: 2020JSWSC..10...37G Altcode: Accurate predictions of harmful space weather effects are mandatory for the protection of astronauts and other assets in space, whether in Earth or lunar orbit, in transit between solar system objects, or on the surface of other planetary bodies. Because the corona is multithermal (i.e., structured not only in space but also in temperature), wavelength-separated data provide crucial information that is not available to imaging methods that integrate over temperature. The extreme ultraviolet (EUV) wavelengths enable us to focus directly on high temperature coronal plasma associated with solar flares, coronal mass ejections (CMEs), and shocked material without being overwhelmed by intensity from the solar disk. Both wide-field imaging and spectroscopic observations of the solar corona taken from a variety of orbits (e.g., Earth, L1, or L5) using suitably-chosen EUV instrumentation offer the possibility of addressing two major goals to enhance our space weather prediction capability, namely: (1) Improve our understanding of the coronal conditions that control the opening and closing of the corona to the heliosphere and consequent solar wind streams, and (2) Improve our understanding of the physical processes that control the early evolution of CMEs and the formation of shocks, from the solar surface out into the extended corona. Title: Observation and Modeling of High-temperature Solar Active Region Emission during the High-resolution Coronal Imager Flight of 2018 May 29 Authors: Warren, Harry P.; Reep, Jeffrey W.; Crump, Nicholas A.; Ugarte-Urra, Ignacio; Brooks, David H.; Winebarger, Amy R.; Savage, Sabrina; De Pontieu, Bart; Peter, Hardi; Cirtain, Jonathan W.; Golub, Leon; Kobayashi, Ken; McKenzie, David; Morton, Richard; Rachmeler, Laurel; Testa, Paola; Tiwari, Sanjiv; Walsh, Robert Bibcode: 2020ApJ...896...51W Altcode: Excellent coordinated observations of NOAA active region 12712 were obtained during the flight of the High-resolution Coronal Imager (Hi-C) sounding rocket on 2018 May 29. This region displayed a typical active region core structure with relatively short, high-temperature loops crossing the polarity inversion line and bright "moss" located at the footpoints of these loops. The differential emission measure (DEM) in the active region core is very sharply peaked at about 4 MK. Further, there is little evidence for impulsive heating events in the moss, even at the high spatial resolution and cadence of Hi-C. This suggests that active region core heating is occurring at a high frequency and keeping the loops close to equilibrium. To create a time-dependent simulation of the active region core, we combine nonlinear force-free extrapolations of the measured magnetic field with a heating rate that is dependent on the field strength and loop length and has a Poisson waiting time distribution. We use the approximate solutions to the hydrodynamic loop equations to simulate the full ensemble of active region core loops for a range of heating parameters. In all cases, we find that high-frequency heating provides the best match to the observed DEM. For selected field lines, we solve the full hydrodynamic loop equations, including radiative transfer in the chromosphere, to simulate transition region and chromospheric emission. We find that for heating scenarios consistent with the DEM, classical signatures of energy release, such as transition region brightenings and chromospheric evaporation, are weak, suggesting that they would be difficult to detect. Title: A New Facility for Airborne Solar Astronomy: NASA's WB-57 at the 2017 Total Solar Eclipse Authors: Caspi, Amir; Seaton, Daniel B.; Tsang, Constantine C. C.; DeForest, Craig E.; Bryans, Paul; DeLuca, Edward E.; Tomczyk, Steven; Burkepile, Joan T.; Casey, Thomas "Tony"; Collier, John; Darrow, Donald "DD"; Del Rosso, Dominic; Durda, Daniel D.; Gallagher, Peter T.; Golub, Leon; Jacyna, Matthew; Johnson, David "DJ"; Judge, Philip G.; Klemm, Cary "Diddle"; Laurent, Glenn T.; Lewis, Johanna; Mallini, Charles J.; Parent, Thomas "Duster"; Propp, Timothy; Steffl, Andrew J.; Warner, Jeff; West, Matthew J.; Wiseman, John; Yates, Mallory; Zhukov, Andrei N.; NASA WB-57 2017 Eclipse Observing Team Bibcode: 2020ApJ...895..131C Altcode: 2020arXiv200409658C NASA's WB-57 High Altitude Research Program provides a deployable, mobile, and stratospheric platform for scientific research. Airborne platforms are of particular value for making coronal observations during total solar eclipses because of their ability both to follow the Moon's shadow and to get above most of the atmospheric air mass that can interfere with astronomical observations. We used the 2017 August 21 eclipse as a pathfinding mission for high-altitude airborne solar astronomy, using the existing high-speed visible-light and near/midwave infrared imaging suite mounted in the WB-57 nose cone. In this paper, we describe the aircraft, the instrument, and the 2017 mission; operations and data acquisition; and preliminary analysis of data quality from the existing instrument suite. We describe benefits and technical limitations of this platform for solar and other astronomical observations. We present a preliminary analysis of the visible-light data quality and discuss the limiting factors that must be overcome with future instrumentation. We conclude with a discussion of lessons learned from this pathfinding mission and prospects for future research at upcoming eclipses, as well as an evaluation of the capabilities of the WB-57 platform for future solar astronomy and general astronomical observation. Title: The Drivers of Active Region Outflows into the Slow Solar Wind Authors: Brooks, David H.; Winebarger, Amy R.; Savage, Sabrina; Warren, Harry P.; De Pontieu, Bart; Peter, Hardi; Cirtain, Jonathan W.; Golub, Leon; Kobayashi, Ken; McIntosh, Scott W.; McKenzie, David; Morton, Richard; Rachmeler, Laurel; Testa, Paola; Tiwari, Sanjiv; Walsh, Robert Bibcode: 2020ApJ...894..144B Altcode: 2020arXiv200407461B Plasma outflows from the edges of active regions have been suggested as a possible source of the slow solar wind. Spectroscopic measurements show that these outflows have an enhanced elemental composition, which is a distinct signature of the slow wind. Current spectroscopic observations, however, do not have sufficient spatial resolution to distinguish what structures are being measured or determine the driver of the outflows. The High-resolution Coronal Imager (Hi-C) flew on a sounding rocket in 2018 May and observed areas of active region outflow at the highest spatial resolution ever achieved (250 km). Here we use the Hi-C data to disentangle the outflow composition signatures observed with the Hinode satellite during the flight. We show that there are two components to the outflow emission: a substantial contribution from expanded plasma that appears to have been expelled from closed loops in the active region core and a second contribution from dynamic activity in active region plage, with a composition signature that reflects solar photospheric abundances. The two competing drivers of the outflows may explain the variable composition of the slow solar wind. Title: Improving Space Weather Forecasting with EUV Observations Authors: Golub, L. Bibcode: 2020LPICo2241.5023G Altcode: Accurate predictions of harmful space weather effects are mandatory for the protection of astronauts at the Moon. Observation of the corona at EUV wavelengths offers the possibility of improving our forecasts of geo- and seleno-effective events. Title: Is the High-Resolution Coronal Imager Resolving Coronal Strands? Results from AR 12712 Authors: Williams, Thomas; Walsh, Robert W.; Winebarger, Amy R.; Brooks, David H.; Cirtain, Jonathan W.; De Pontieu, Bart; Golub, Leon; Kobayashi, Ken; McKenzie, David E.; Morton, Richard J.; Peter, Hardi; Rachmeler, Laurel A.; Savage, Sabrina L.; Testa, Paola; Tiwari, Sanjiv K.; Warren, Harry P.; Watkinson, Benjamin J. Bibcode: 2020ApJ...892..134W Altcode: 2020arXiv200111254W Following the success of the first mission, the High-Resolution Coronal Imager (Hi-C) was launched for a third time (Hi-C 2.1) on 2018 May 29 from the White Sands Missile Range, NM, USA. On this occasion, 329 s of 17.2 nm data of target active region AR 12712 were captured with a cadence of ≈4 s, and a plate scale of 0.129 arcsec pixel-1. Using data captured by Hi-C 2.1 and co-aligned observations from SDO/AIA 17.1 nm, we investigate the widths of 49 coronal strands. We search for evidence of substructure within the strands that is not detected by AIA, and further consider whether these strands are fully resolved by Hi-C 2.1. With the aid of multi-scale Gaussian normalization, strands from a region of low emission that can only be visualized against the contrast of the darker, underlying moss are studied. A comparison is made between these low-emission strands and those from regions of higher emission within the target active region. It is found that Hi-C 2.1 can resolve individual strands as small as ≈202 km, though the more typical strand widths seen are ≈513 km. For coronal strands within the region of low emission, the most likely width is significantly narrower than the high-emission strands at ≈388 km. This places the low-emission coronal strands beneath the resolving capabilities of SDO/AIA, highlighting the need for a permanent solar observatory with the resolving power of Hi-C. Title: Total solar eclipse 2017 in USA: deep coronal spectra Authors: Koutchmy, S.; Baudin, F.; Abdi, Sh.; Golub, L.; Sèvre, F. Bibcode: 2019sf2a.conf..363K Altcode: Total eclipses permit a deep analysis of both the inner and the outer parts of the solar corona using the Thomson scattered (inverse Compton effect on free electrons at millions degrees T^{\circ} ) continuum White- Light (W-L) radiations and the spectrum of forbidden emission lines from hot highly ionized ions of iron, nickel, argon, etc. Spectra are largely affected by the superposition of the solar light scattered and diffracted by the interplanetary dust particles orbiting the Sun at large distances but intercepted along the line of sight (los)\citep{1973ApJ...186..671K}. Sometimes the parasitic light due to multiple scattering from the ground and from the Earth atmosphere should be removed using the light observed on the Moon image background. After sufficiently dispersing the W-L corona, the Fraunhofer (F) spectrum of the dust corona appears with its absorption (dark) lines of known equivalent widths and the continuum Thomson radiation can be extracted. The identified emission (bright) lines of ions with different degrees of ionization are studied to permit an evaluation of i/ relative abundances (compared to photospheric abundances), ii/ temperatures, iii/ non-thermal velocities and the resulting from the analysis of the departures from a Gaussian profile of net Doppler shifts after integration along the los. 60 spectra were obtained during the totality using a specially designed slit spectroscopic experiment for providing an accurate analysis of the most typical "broadly averaged" parts of the quasi-minimum of activity type corona. With the scanning +/- 3 solar radii long slit a .072 nm FWHM effective resolution was obtained in the range of 510 to 590 nm. The background sky was exceptionally clear during this US total eclipse of Aug. 21, 2017 as observed from our site in Idaho; spectra are without significant parasitic light on the Moon disk. The K+F continuum corona is well exposed up to at least 1 solar radius (Rs) from the limb and further out with a lower S/N ratio, showing several forbidden coronal emission lines. The F-corona can be measured even at the solar limb where its intensity reached near 6\% of the K-corona intensity. Streamers, active region enhancements and polar coronal holes (CHs) are well measured on each 1 sec exposure time coronal spectra see Fig. \ref{author1:fig1}; the 2^{nd} contact showing the chromospheric and the most inner layers emission lines was observed with a fast sequence and exposure time 10 times shorter. New weak emission lines were also discovered and/or confirmed see Fig. \ref{author1:fig2} ; their identifications are proposed. The rarely observed high FIP ArX \citep{2018ApJ...852...52D} line is recorded almost everywhere and a new nearby FeX line is well identified; the classical low FIP FeXIV and NiXIII lines are well recorded everywhere without over-exposure. For the 1st time hot lines are also measured at low levels inside the CH regions, at both poles. The radial variations of the corrected non-thermal turbulent velocities of the lines do not show a great departure from the average values. No significantly large Doppler shifts are seen nowhere in the inner and the middle corona although the whole corona is almost covered.\citep{Koutchmy} The corona is confirmed to be made of a mixing of hot and less hot components everywhere around the Sun, due to the yet unidentified magnetic origin heating processes reflected in our spectra and in the line profiles. Coronal density variations are well reflected by the K-corona continuum intensity variations the azimuthal and radial direction variations will permit the interpretation of the emission measures to be compared with the simultaneously obtained AIA images from the SDO space mission. The W-L images taken simultaneously shows a much better spatial resolution with images of bright background well known stars that permit to deduce an excellent absolute calibration needed to deduce the electron densities and to check our F-corona model, see \ref{author1:fig3}. Title: Improving Space Weather Forecasting With Wide-Field EUV Observations Authors: Golub, L.; Savage, S. L. Bibcode: 2019AGUFMSH13A..05G Altcode: Observation of the solar corona from earth orbit or from other locations such as L1 or L5 using suitably-chosen EUV wavelengths offers the possibility of addressing two major goals that will improve our ability to forecast and predict geoeffective space weather events: 1.) improve our understanding of the coronal conditions that control the opening and closing of the corona to the heliosphere, and 2.) improve our understanding of the physical processes that control the evolution of CMEs and the formation of shocks from the solar surface out to beyond the nominal source surface. Forecasting models such as EUHFORIA find that predictions at 1 au are extremely sensitive to the initial conditions input to the model, and EUV imaging plus spectroscopic imaging data, such as that proposed by the COSIE investigation, can determine 8 of the 10 parameters used. This combination of EUV measurements can help to: i.) determine coronal structuring from its roots out to beyond 2.5 R_s; ii.) measure the changes in coronal connectivity; iii.) distinguish between and test solar wind models; iv.) establish the impact of pre-existing coronal structures on CME evolution; v.) confront theories of SEP acceleration and preconditioning; and vi.) establish the extent of energy release behind CMEs. Title: Hi-C 2.1 Observations of Jetlet-like Events at Edges of Solar Magnetic Network Lanes Authors: Panesar, Navdeep K.; Sterling, Alphonse C.; Moore, Ronald L.; Winebarger, Amy R.; Tiwari, Sanjiv K.; Savage, Sabrina L.; Golub, Leon E.; Rachmeler, Laurel A.; Kobayashi, Ken; Brooks, David H.; Cirtain, Jonathan W.; De Pontieu, Bart; McKenzie, David E.; Morton, Richard J.; Peter, Hardi; Testa, Paola; Walsh, Robert W.; Warren, Harry P. Bibcode: 2019ApJ...887L...8P Altcode: 2019arXiv191102331P We present high-resolution, high-cadence observations of six, fine-scale, on-disk jet-like events observed by the High-resolution Coronal Imager 2.1 (Hi-C 2.1) during its sounding-rocket flight. We combine the Hi-C 2.1 images with images from the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) and the Interface Region Imaging Spectrograph (IRIS), and investigate each event’s magnetic setting with co-aligned line-of-sight magnetograms from the SDO/Helioseismic and Magnetic Imager (HMI). We find that (i) all six events are jetlet-like (having apparent properties of jetlets), (ii) all six are rooted at edges of magnetic network lanes, (iii) four of the jetlet-like events stem from sites of flux cancelation between majority-polarity network flux and merging minority-polarity flux, and (iv) four of the jetlet-like events show brightenings at their bases reminiscent of the base brightenings in coronal jets. The average spire length of the six jetlet-like events (9000 ± 3000 km) is three times shorter than that for IRIS jetlets (27,000 ± 8000 km). While not ruling out other generation mechanisms, the observations suggest that at least four of these events may be miniature versions of both larger-scale coronal jets that are driven by minifilament eruptions and still-larger-scale solar eruptions that are driven by filament eruptions. Therefore, we propose that our Hi-C events are driven by the eruption of a tiny sheared-field flux rope, and that the flux rope field is built and triggered to erupt by flux cancelation. Title: Young Solar Wind in the Grip of the Sun's Corona Authors: Kasper, J. C.; Bale, S. D.; Belcher, J. W.; Berthomier, M.; Case, A. W.; Chandran, B. D. G.; Curtis, D. W.; Gallagher, D. L.; Gary, S. P.; Golub, L.; Halekas, J. S.; Ho, G. C.; Horbury, T. S.; Hu, Q.; Huang, J.; Klein, K. G.; Korreck, K. E.; Larson, D. E.; Livi, R.; Maruca, B.; Lavraud, B.; Louarn, P.; Maksimovic, M.; Martinović, M.; McGinnis, D.; Pogorelov, N. V.; Richardson, J. D.; Skoug, R. M.; Steinberg, J. T.; Stevens, M. L.; Szabo, A.; Velli, M.; Whittlesey, P. L.; Wright, K. H., Jr.; Zank, G. P.; MacDowall, R. J.; McComas, D. J.; McNutt, R. L., Jr.; Pulupa, M.; Raouafi, N. E.; Schwadron, N. Bibcode: 2019AGUFMSH11A..02K Altcode: The birthplace of the solar wind is the corona of our Sun, where unidentified mechanisms heat the plasma to millions of Kelvin and magnetic fields shape the flow of particles and waves. The plasma is unstable, accelerating as it expands away from the Sun, exceeding the speed of sound at a heliocentric distance of a few solar radii (Rs) and the Alfvén speed at 36 Rs, beyond which the wind decouples from the corona. Here, we show the first observations of the young, low-Alfvén-mach-number wind obtained by the Solar Wind Electrons Alphas and Protons (SWEAP) plasma instruments on Parker Solar Probe (PSP) during its first two encounters with the Sun. Once PSP dropped below a quarter of the distance from the Sun to the Earth, SWEAP began to detect (for the first time) a persistent and growing rotational circulation of the plasma around the Sun peaking at 40-50 km/s at perihelion as the Alfvén mach number fell to 1.5. This finding may support theories for enhanced stellar angular momentum loss due to rigid coronal rotation, but the circulation is large, and angular momentum does not appear to be conserved, suggesting that torques still act on the young wind at these distances. PSP also measured numerous intense and organized Alfvénic velocity spikes with strong propagating field reversals and large jumps in speed. These field reversals and jets call for an overhaul in our understanding of the turbulent fluctuations that may, by energizing the solar wind, hold the key to its origin. Title: Combined Next-Generation X-ray and EUV Observations with the FIERCE Mission Concept Authors: Shih, A. Y.; Glesener, L.; Christe, S.; Reeves, K.; Gburek, S.; Alaoui, M.; Allred, J. C.; Baumgartner, W.; Caspi, A.; Dennis, B. R.; Drake, J. F.; Goetz, K.; Golub, L.; Guidoni, S. E.; Inglis, A.; Hannah, I. G.; Holman, G.; Hayes, L.; Ireland, J.; Kerr, G. S.; Klimchuk, J. A.; Krucker, S.; McKenzie, D. E.; Moore, C. S.; Musset, S.; Reep, J. W.; Ryan, D.; Saint-Hilaire, P.; Savage, S. L.; Seaton, D. B.; Steslicki, M.; Woods, T. N. Bibcode: 2019AGUFMSH33A..08S Altcode: While there have been significant advances in our understanding of impulsive energy release at the Sun through the combination of RHESSI X-ray observations and SDO/AIA EUV observations, there is a clear science need for significantly improved X-ray and EUV observations. These new observations must capture the full range of emission in flares and CMEs (e.g., faint coronal sources near bright chromospheric sources), connect the intricate evolution of energy release with dynamic changes in the configuration of plasma structures, and identify the signatures of impulsive energy release in even the quiescent Sun. The Fundamentals of Impulsive Energy Release in the Corona Explorer ( FIERCE ) MIDEX mission concept makes these observations by combining the two instruments previously proposed on the FOXSI SMEX mission concept - a focusing hard X-ray spectroscopic imager and a soft X-ray spectrometer - with a high-resolution EUV imager that will not saturate for even intense flares. All instruments observe at high cadence to capture the initiation of solar transient events and the fine time structure within events. FIERCE would launch in mid-2025, near the peak of the next solar cycle, which is also well timed with perihelions of Parker Solar Probe and Solar Orbiter. Title: Alfvénic velocity spikes and rotational flows in the near-Sun solar wind Authors: Kasper, J. C.; Bale, S. D.; Belcher, J. W.; Berthomier, M.; Case, A. W.; Chandran, B. D. G.; Curtis, D. W.; Gallagher, D.; Gary, S. P.; Golub, L.; Halekas, J. S.; Ho, G. C.; Horbury, T. S.; Hu, Q.; Huang, J.; Klein, K. G.; Korreck, K. E.; Larson, D. E.; Livi, R.; Maruca, B.; Lavraud, B.; Louarn, P.; Maksimovic, M.; Martinovic, M.; McGinnis, D.; Pogorelov, N. V.; Richardson, J. D.; Skoug, R. M.; Steinberg, J. T.; Stevens, M. L.; Szabo, A.; Velli, M.; Whittlesey, P. L.; Wright, K. H.; Zank, G. P.; MacDowall, R. J.; McComas, D. J.; McNutt, R. L.; Pulupa, M.; Raouafi, N. E.; Schwadron, N. A. Bibcode: 2019Natur.576..228K Altcode: The prediction of a supersonic solar wind1 was first confirmed by spacecraft near Earth2,3 and later by spacecraft at heliocentric distances as small as 62 solar radii4. These missions showed that plasma accelerates as it emerges from the corona, aided by unidentified processes that transport energy outwards from the Sun before depositing it in the wind. Alfvénic fluctuations are a promising candidate for such a process because they are seen in the corona and solar wind and contain considerable energy5-7. Magnetic tension forces the corona to co-rotate with the Sun, but any residual rotation far from the Sun reported until now has been much smaller than the amplitude of waves and deflections from interacting wind streams8. Here we report observations of solar-wind plasma at heliocentric distances of about 35 solar radii9-11, well within the distance at which stream interactions become important. We find that Alfvén waves organize into structured velocity spikes with duration of up to minutes, which are associated with propagating S-like bends in the magnetic-field lines. We detect an increasing rotational component to the flow velocity of the solar wind around the Sun, peaking at 35 to 50 kilometres per second—considerably above the amplitude of the waves. These flows exceed classical velocity predictions of a few kilometres per second, challenging models of circulation in the corona and calling into question our understanding of how stars lose angular momentum and spin down as they age12-14. Title: Coronal Solar Magnetism Observatory Science Objectives Authors: Gibson, S. E.; Tomczyk, S.; Burkepile, J.; Casini, R.; DeLuca, E.; de Toma, G.; de Wijn, A.; Fan, Y.; Golub, L.; Judge, P. G.; Landi, E.; McIntosh, S. W.; Reeves, K.; Seaton, D. B.; Zhang, J. Bibcode: 2019AGUFMSH11C3395G Altcode: Space-weather forecast capability is held back by our current lack of basic scientific understanding of CME magnetic evolution, and the coronal magnetism that structures and drives the solar wind. Comprehensive observations of the global magnetothermal environment of the solar atmosphere are needed for progress. When fully implemented, the COSMO suite of synoptic ground-based telescopes will provide the community with comprehensive and simultaneous measurements of magnetism, temperature, density and plasma flows and waves from the photosphere through the chromosphere and out into the corona. We will discuss how these observations will uniquely address a set of science objectives that are central to the field of solar and space physics: in particular, to understand the storage and release of magnetic energy, to understand CME dynamics and consequences for shocks, to determine the role of waves in solar atmospheric heating and solar wind acceleration, to understand how the coronal magnetic field relates to the solar dynamo, and to constrain and improve space-weather forecast models. Title: Fine-scale Explosive Energy Release at Sites of Prospective Magnetic Flux Cancellation in the Core of the Solar Active Region Observed by Hi-C 2.1, IRIS, and SDO Authors: Tiwari, Sanjiv K.; Panesar, Navdeep K.; Moore, Ronald L.; De Pontieu, Bart; Winebarger, Amy R.; Golub, Leon; Savage, Sabrina L.; Rachmeler, Laurel A.; Kobayashi, Ken; Testa, Paola; Warren, Harry P.; Brooks, David H.; Cirtain, Jonathan W.; McKenzie, David E.; Morton, Richard J.; Peter, Hardi; Walsh, Robert W. Bibcode: 2019ApJ...887...56T Altcode: 2019arXiv191101424T The second Hi-C flight (Hi-C 2.1) provided unprecedentedly high spatial and temporal resolution (∼250 km, 4.4 s) coronal EUV images of Fe IX/X emission at 172 Å of AR 12712 on 2018 May 29, during 18:56:21-19:01:56 UT. Three morphologically different types (I: dot-like; II: loop-like; III: surge/jet-like) of fine-scale sudden-brightening events (tiny microflares) are seen within and at the ends of an arch filament system in the core of the AR. Although type Is (not reported before) resemble IRIS bombs (in size, and brightness with respect to surroundings), our dot-like events are apparently much hotter and shorter in span (70 s). We complement the 5 minute duration Hi-C 2.1 data with SDO/HMI magnetograms, SDO/AIA EUV images, and IRIS UV spectra and slit-jaw images to examine, at the sites of these events, brightenings and flows in the transition region and corona and evolution of magnetic flux in the photosphere. Most, if not all, of the events are seated at sites of opposite-polarity magnetic flux convergence (sometimes driven by adjacent flux emergence), implying likely flux cancellation at the microflare’s polarity inversion line. In the IRIS spectra and images, we find confirming evidence of field-aligned outflow from brightenings at the ends of loops of the arch filament system. In types I and II the explosion is confined, while in type III the explosion is ejective and drives jet-like outflow. The light curves from Hi-C, AIA, and IRIS peak nearly simultaneously for many of these events, and none of the events display a systematic cooling sequence as seen in typical coronal flares, suggesting that these tiny brightening events have chromospheric/transition region origin. Title: The High-Resolution Coronal Imager, Flight 2.1 Authors: Rachmeler, Laurel A.; Winebarger, Amy R.; Savage, Sabrina L.; Golub, Leon; Kobayashi, Ken; Vigil, Genevieve D.; Brooks, David H.; Cirtain, Jonathan W.; De Pontieu, Bart; McKenzie, David E.; Morton, Richard J.; Peter, Hardi; Testa, Paola; Tiwari, Sanjiv K.; Walsh, Robert W.; Warren, Harry P.; Alexander, Caroline; Ansell, Darren; Beabout, Brent L.; Beabout, Dyana L.; Bethge, Christian W.; Champey, Patrick R.; Cheimets, Peter N.; Cooper, Mark A.; Creel, Helen K.; Gates, Richard; Gomez, Carlos; Guillory, Anthony; Haight, Harlan; Hogue, William D.; Holloway, Todd; Hyde, David W.; Kenyon, Richard; Marshall, Joseph N.; McCracken, Jeff E.; McCracken, Kenneth; Mitchell, Karen O.; Ordway, Mark; Owen, Tim; Ranganathan, Jagan; Robertson, Bryan A.; Payne, M. Janie; Podgorski, William; Pryor, Jonathan; Samra, Jenna; Sloan, Mark D.; Soohoo, Howard A.; Steele, D. Brandon; Thompson, Furman V.; Thornton, Gary S.; Watkinson, Benjamin; Windt, David Bibcode: 2019SoPh..294..174R Altcode: 2019arXiv190905942R The third flight of the High-Resolution Coronal Imager (Hi-C 2.1) occurred on May 29, 2018; the Sounding Rocket was launched from White Sands Missile Range in New Mexico. The instrument has been modified from its original configuration (Hi-C 1) to observe the solar corona in a passband that peaks near 172 Å, and uses a new, custom-built low-noise camera. The instrument targeted Active Region 12712, and captured 78 images at a cadence of 4.4 s (18:56:22 - 19:01:57 UT; 5 min and 35 s observing time). The image spatial resolution varies due to quasi-periodic motion blur from the rocket; sharp images contain resolved features of at least 0.47 arcsec. There are coordinated observations from multiple ground- and space-based telescopes providing an unprecedented opportunity to observe the mass and energy coupling between the chromosphere and the corona. Details of the instrument and the data set are presented in this paper. Title: New deep coronal spectra from the 2017 total solar eclipse Authors: Koutchmy, S.; Baudin, F.; Abdi, Sh.; Golub, L.; Sèvre, F. Bibcode: 2019A&A...632A..86K Altcode: 2019arXiv191001372K Context. The origin of the high temperature of the solar corona, in both the inner bright parts and the more outer parts showing flows toward the solar wind, is not understood well yet. Total eclipses permit a deep analysis of both the inner and the outer parts of the corona using the continuum white-light (W-L) radiations from electrons (K-corona), the superposed spectrum of forbidden emission lines from ions (E-corona), and the dust component with F-lines (F-corona).
Aims: By sufficiently dispersing the W-L spectrum, the Fraunhofer (F) spectrum of the dust component of the corona appears and the continuum Thomson radiation can be evaluated. The superposed emission lines of ions with different degrees of ionization are studied to allow the measurement of temperatures, non-thermal velocities, Doppler shifts, and abundances to constrain the proposed heating mechanisms and understand the origin of flows that lead to solar wind.
Methods: We describe a slit spectroscopic experiment of high spectral resolution to provide an analysis of the most typical parts of the quasi-minimum type corona observed during the total solar eclipse of Aug. 21, 2017 from Idaho, USA. Streamers, active region enhancements, and polar coronal holes (CHs) are measured well using deep spectra.
Results: Sixty spectra are obtained during the totality with a long slit, covering ±3 solar radii in the range of 510 nm to 590 nm. The K+F continuum corona is exposed well up to two solar radii. The F-corona can be measured even at the solar limb. New weak emission lines were discovered or confirmed. The rarely observed Ar X line is detected almost everywhere; the Fe XIV and Ni XIII lines are clearly detected everywhere. For the first time hot lines are also measured inside the CH regions. The radial variations of the non-thermal turbulent velocities of the lines do not show a great departure from the average values. No significantly large Doppler shifts are seen anywhere in the inner or the middle corona. The wings of the Fe XIV line show some non-Gaussianity.
Conclusions: Deep slit coronal spectra offered an opportunity for diagnosing several aspects of coronal physics during a well observed total eclipse without extended investments. The analysis of the ionic emission line profiles offers several powerful diagnostics of the coronal dynamics; the precise measurement of the F-continuum component provides insight into the ubiquitous dust corona at the solar limb. Title: FIERCE Science: Expected Results From a High-Energy Medium-Class Explorer Authors: Glesener, L.; Shih, A. Y.; Christe, S.; Reeves, K.; Gburek, S.; Alaoui, M.; Allred, J. C.; Baumgartner, W.; Caspi, A.; Dennis, B. R.; Drake, J. F.; Golub, L.; Goetz, K.; Guidoni, S. E.; Hannah, I. G.; Hayes, L.; Holman, G.; Inglis, A.; Ireland, J.; Kerr, G. S.; Klimchuk, J. A.; Krucker, S.; McKenzie, D. E.; Moore, C. S.; Musset, S.; Reep, J. W.; Ryan, D.; Saint-Hilaire, P.; Savage, S. L.; Seaton, D. B.; Steslicki, M.; Woods, T. N. Bibcode: 2019AGUFMSH31C3313G Altcode: A variety of individual X-ray and EUV instruments have probed high-energy aspects of the Sun over the decades, each contributing pieces to the puzzles of the energization, heating, and acceleration of solar plasma and particles. But fundamental difficulties in sensitivity and dynamic range impart big challenges in probing the details of particle acceleration sites, understanding how eruptions and flares are initiated, and tracking the intricacies of energy transfer as flares evolve. The Fundamentals of Impulsive Energy Release in the Corona Explorer ( FIERCE ) mission will make substantial leaps forward in these scientific ventures by combining a variety of instruments into one platform, each optimized to have high sensitivity and dynamic range. FIERCE is a proposed NASA Heliophysics Medium-Class Explorer that will investigate high-energy solar phenomena across a variety of spectral and spatial dimensions. It combines hard X-ray imaging spectroscopy (via focusing, for the first time for a solar-dedicated spacecraft), spatially integrated soft X-ray spectroscopy, and fast, high-resolution extreme ultraviolet imaging at coronal and flare temperatures. FIERCE uses this array of instruments to make important contributions toward probing the genesis of space weather events, the acceleration of particles, the transport of flare energy, and the heating of the corona. Here, we present some of the expected science outcomes for the FIERCE observatory, concentrating on the ways in which FIERCE can probe confined and eruptive events, particle acceleration everywhere it may occur on the Sun, and the connections of solar high-energy phenomena to the heliosphere. Title: High-Altitude Instrumentation for Infrared Observations of the Solar Corona Authors: Samra, J.; Cheimets, P.; DeLuca, E.; Golub, L.; Hannigan, J. W.; Judge, P. G.; Madsen, C. A.; Marquez, V.; Tañón Reyes, N.; Tomczyk, S. Bibcode: 2019AGUFMSH43B..07S Altcode: High-altitude infrared remote sensing is a promising new method for measuring coronal plasma and magnetic fields. We present new results from a recent airborne eclipse mission and outline concepts for future airborne and balloon-based instruments for coronal spectroscopy and spectro-polarimetry.

The airborne infrared spectrometer (AIR-Spec) was commissioned during the 2017 total solar eclipse, when it observed five infrared coronal emission lines from the NSF Gulfstream V research jet. These magnetically sensitive emission lines of highly ionized magnesium, silicon, sulfur, and iron are promising candidates for future observations of the coronal magnetic field, and their characterization is an important first step toward developing the next generation of instrumentation for coronal magnetometry. The second AIR-Spec research flight took place during the July 2, 2019 total solar eclipse across the south Pacific. Higher sensitivity and reduced jitter enabled more precise measurements of emission line properties and plasma density, temperature, and line-of-sight velocity up to one solar radius from the solar limb. Atmospheric absorption was significant, even at altitude, and atmospheric modeling was required to extract accurate line intensities.

AIR-Spec is a slit spectrometer that measures light over a 1.55 solar radius field of view in three spectral passbands between 1.4 and 3 microns. The successful eclipse missions overcame a number of engineering challenges, centered around maintaining adequate resolution and signal-to-noise ratio in a compact and inexpensive package on a moving platform. AIR-Spec is a pathfinder for future infrared spectrometers and spectro-polarimeters, including a balloon-based coronagraph that will measure the global coronal magnetic field and an airborne spectrometer that will survey the infrared emission corona during a future eclipse. Title: Novel observations of the middle corona during the 2017 total solar eclipse Authors: Caspi, A.; Seaton, D. B.; Tsang, C.; DeForest, C.; Bryans, P.; Samra, J.; DeLuca, E.; Tomczyk, S.; Burkepile, J.; Gallagher, P.; Golub, L.; Judge, P. G.; Laurent, G. T.; West, M.; Zhukov, A. Bibcode: 2019AGUFMSH13A..10C Altcode: Total solar eclipses offer rare opportunities to study the middle corona. This intriguing region contains complex interfaces and transitions between physical regimes, but has historically been under-observed due to the challenges of observing its dim emission so close to the bright inner corona and blinding solar disk. The unique circumstances of a total solar eclipse coupled with a high-altitude observing platform provide nearly space-quality observing conditions, including for wavelengths inaccessible by ground-based observatories, but with availability of ground-quality resources, including high-speed, high-resolution, wide-field coronography typically inaccessible from space. We used the 2017 August 21 "Great American" total solar eclipse to observe the solar corona from ~1.02 to ~3 RSun in both visible (533.9 ± 4.75 nm) and medium-wave infrared (3-5 μm) light using stabilized telescopes on two of NASA's WB-57F high-altitude research aircraft. This pathfinding mission utilized existing instrumentation to evaluate the platform performance, guide instrumentation development, and explore new discovery space for future studies of the middle corona.

We present the high-speed (30 Hz), high-resolution (3 arcsec/pixel) visible and IR observations obtained during the eclipse, and analysis of these observations in the context of coronal structure and dynamics. We discuss the limitations of the prototype data and pathways forward for future instrumentation and missions optimized for the range of observable parameters in the middle corona. We also discuss the benefits of such eclipse studies to an understanding of the corona as a single, unified system, from its origins at the solar surface to its extension into the heliosphere, particularly within the context of a developing multi- and inter-disciplinary research collaboration, COHERENT (the "Corona as a Holistic Environment" Research Network). Title: Unfolding Overlappogram Data: Preparing for the COOL-AID instrument on Hi-C FLARE Authors: Winebarger, A. R.; De Pontieu, B.; Cheung, C. M. M.; Martinez-Sykora, J.; Hansteen, V. H.; Testa, P.; Golub, L.; Savage, S. L.; Samra, J.; Reeves, K. Bibcode: 2019AGUFMSH33A..06W Altcode: During a solar flare, energy released in the corona streams to the solar chromosphere, where plasma is heated and then evaporated upward. The magnitude of these velocities and their evolution as a function of time can provide quantitative information on the magnitude of energy released and the method by which it is transported in a solar flare. Measuring these velocities, however, is quite challenging. Typically, they are measured with single slit spectrometers, where light passing through a long but narrow slit is dispersed and emission lines formed across a range of temperatures are observed. The main issue with using single slit spectrometers to make this measurement is that they are rarely pointed at the right place at the right time. Additionally, their fields of view are limited by narrow slit widths, and although rastering can effectively expand the field of view, it does so at the cost of time. This combination means that single slit spectrometers cannot adequately capture the evolution of the flare velocities. On the contrary, slitless spectrometers can make "overlappograms'', which provide both imaging and spectral information over a large field of view. However, spatial information from different spectral lines can overlap in the dispersion direction, making the data difficult to interpret. Furthermore, the spectral resolution of slitless spectrometers are limited and typically worse than single-slit spectrometers, since no line fitting (and hence sub-pixel sampling) is possible.

For the next generation of the High-resolution Coronal Imager (Hi-C) Rocket Experiment, which we are proposing to launch during a solar flare, we are including the COronal OverLapagram - Ancillary Imaging Diagnostics (COOL-AID) instrument. COOL-AID is a slitless spectrometer based on the COronal Spectrographic Imager in the EUV (COSIE) design, but with a narrow passband coating around 12.9 nm (the same passband as the primary Hi-C telescope), a spatial resolution of ~1"x2", and a velocity resolution of ~5 km/s. The goal of the COOL-AID instrument is to determine the velocity associated with the Fe XXI 12.9 nm spectral line during a solar flare. In this talk, we will demonstrate the unfolding method developed by Cheung et al (2019) to determine the velocity information from a simulated COOL-AID data set. Title: Solar Eclipse Observations from the Ground and Air from 0.31 to 5.5 Microns Authors: Judge, Philip; Berkey, Ben; Boll, Alyssa; Bryans, Paul; Burkepile, Joan; Cheimets, Peter; DeLuca, Edward; de Toma, Giuliana; Gibson, Keon; Golub, Leon; Hannigan, James; Madsen, Chad; Marquez, Vanessa; Richards, Austin; Samra, Jenna; Sewell, Scott; Tomczyk, Steven; Vera, Alysha Bibcode: 2019SoPh..294..166J Altcode: We present spectra and broad-band polarized light data from a novel suite of instruments deployed during the 21st August 2017 total solar eclipse. Our goals were to survey solar spectra at thermal infrared wavelengths during eclipse, and to test new technology for measuring polarized coronal light. An infrared coronal imaging spectrometer, flown at 14.3 km altitude above Kentucky, was supported on the ground by observations from Madras, Oregon (elevation 683 m) and Camp Wyoba on Casper Mountain, Wyoming (2402 m). In Wyoming we deployed a new infrared Fourier Transform Spectrometer (FTS), three low-dispersion spectrometers loaned to us by Avantes, a novel visible-light camera PolarCam, sensitive to linear polarization, and one of two infrared cameras from FLIR Systems, the other operated at Madras. Circumstances of eclipse demanded that the observations spanned 17:19 to 18:26 UT. We analyze spectra of the limb photosphere, the chromosphere, prominences, and coronal lines from 310 nm to 5.5 μm. We calibrated data photometrically using the solar disk as a source. Between different spectrometers, the calibrations were consistent to better than 13%. But the sensitivities achieved were insufficient to detect coronal lines from the ground. The PolarCam data are in remarkable agreement with polarization data from the K-Cor synoptic instrument on Mauna Loa, and with FLIR intensity data acquired in Madras. We discuss new results, including a detection of the He I 1083 nm multiplet in emission during the whole of totality. The combination of the FTS and AIR-Spec spectra reveals for the first time the effects of the telluric extinction on the infrared coronal emission lines, to be observed with upcoming Daniel K. Inouye Solar Telescope. Title: Solar Active Region Heating Diagnostics from High-temperature Emission Using the MaGIXS Authors: Athiray, P. S.; Winebarger, Amy R.; Barnes, Will T.; Bradshaw, Stephen J.; Savage, Sabrina; Warren, Harry P.; Kobayashi, Ken; Champey, Patrick; Golub, Leon; Glesener, Lindsay Bibcode: 2019ApJ...884...24A Altcode: 2019arXiv190902541A The relative amount of high-temperature plasma has been found to be a useful diagnostic to determine the frequency of coronal heating on sub-resolution structures. When the loops are infrequently heated, a broad emission measure (EM) over a wider range of temperatures is expected. A narrower EM is expected for high-frequency heating where the loops are closer to equilibrium. The soft X-ray spectrum contains many spectral lines that provide high-temperature diagnostics, including lines from Fe XVII-XIX. This region of the solar spectrum will be observed by the Marshall Grazing Incidence Spectrometer (MaGIXS) in 2020. In this paper, we derive the expected spectral line intensity in MaGIXS to varying amounts of high-temperature plasma to demonstrate that a simple line ratio provides a powerful diagnostic to determine the heating frequency. Similarly, we examine ratios of AIA channel intensities, filter ratios from a XRT, and energy bands from the FOXSI sounding rocket to determine their sensitivity to this parameter. We find that both FOXSI and MaGIXS provide good diagnostic capabilities for high-temperature plasma. We then compare the predicted line ratios to the output of a numerical model and confirm that the MaGIXS ratios provide an excellent diagnostic for heating frequency. Title: State of the Profession Considerations for Laboratory Astrophysics Authors: Savin, Daniel Wolf; Babb, James F.; Barklem, Paul; Bellan, Paul M.; Betancourt-Martinez, Gabriele; Blum, Jürgen; Boersma, Christiaan; Boryta, Mark D.; Brisset, Julie; Brogan, Crystal; Cami, Jan; Caselli, Paola; Chutjian, Ara; Corrales, Lia; Crabtree, Kyle; Dominguez, Gerardo; Federman, Steven R.; Fontes, Christopher J.; Freedman, Richard; Gavilan-Marin, Lisseth; Gibson, Brad; Golub, Leon; Gorczyca, Thomas W.; Hahn, Michael; Hartmann, Dieter; Hörst, Sarah M.; Hudson, Reggie L.; Ji, Hantao; Kreckel, Holger; Kuhn, Jeffrey; Lawler, James E.; Lee, Timothy J.; Leutenegger, Maurice A.; Mancini, Roberto; Marler, Joan P.; Mashonkina, Lyudmila I.; McCarthy, Michael C.; McCoustra, Martin; McGuire, Brett A.; Milam, Stefanie N.; Montgomery, Mike; Murphy, Nicholas A.; Nave, Gillian; Nelson, Robert M.; Nollett, Kenneth M.; Norton, Aimee A.; Novotný, Oldřich; Papol, Anthony; Raymond, John C.; Salama, Farid; Sciamma-O'Brien, Ella M.; Smith, Randall; Sosolik, Chad; Sousa-Silva, Clara; Spyrou, Artemis; Stancil, Phillip C.; Sung, Keeyoon; Tennyson, Jonathan; Timmes, Frank; Trimble, Virginia L.; Venot, Olivia; Wahlgren, Glenn; Wargelin, Bradford J.; Winget, Don; Wood, Michael P. Bibcode: 2019BAAS...51g...7S Altcode: 2019astro2020U...7S Astrophysics advances, in part, through laboratory astrophysics studies of the underlying processes controlling the observed properties of the Cosmos. These studies encompass both theoretical and experimental research. Robust support for laboratory astrophysics is critically needed to maximize the scientific return of astronomical observations. Title: Unfolding Overlapped Slitless Imaging Spectrometer Data for Extended Sources Authors: Winebarger, Amy R.; Weber, Mark; Bethge, Christian; Downs, Cooper; Golub, Leon; DeLuca, Edward; Savage, Sabrina; del Zanna, Giulio; Samra, Jenna; Madsen, Chad; Ashraf, Afra; Carter, Courtney Bibcode: 2019ApJ...882...12W Altcode: 2018arXiv181108329W Slitless spectrometers can provide simultaneous imaging and spectral data over an extended field of view, thereby allowing rapid data acquisition for extended sources. In some instances, when the object is greatly extended or the spectral dispersion is too small, there may be locations in the focal plane where emission lines at different wavelengths contribute. It is then desirable to unfold the overlapped regions in order to isolate the contributions from the individual wavelengths. In this paper, we describe a method for such an unfolding, using an inversion technique developed for an extreme ultraviolet imaging spectrometer and coronagraph named the COronal Spectroscopic Imager in the EUV (COSIE). The COSIE spectrometer wavelength range (18.6-20.5 nm) contains a number of strong coronal emission lines and several density sensitive lines. We focus on optimizing the unfolding process to retrieve emission measure maps at constant temperature, maps of spectrally pure intensity in the Fe XII and Fe XIII lines, and density maps based on both Fe XII and Fe XIII diagnostics. Title: Investigating Coronal Magnetism with COSMO: Science on the Critical Path To Understanding The ``Weather'' of Stars and Stellarspheres Authors: McIntosh, Scott; Tomczyk, Steven; Gibson, Sarah E.; Burkepile, Joan; de Wijn, Alfred; Fan, Yuhong; deToma, Giuliana; Casini, Roberto; Landi, Enrico; Zhang, Jie; DeLuca, Edward E.; Reeves, Katharine K.; Golub, Leon; Raymond, John; Seaton, Daniel B.; Lin, Haosheng Bibcode: 2019BAAS...51g.165M Altcode: 2019astro2020U.165M The Coronal Solar Magnetism Observatory (COSMO) is a unique ground-based facility designed to address the shortfall in our capability to measure magnetic fields in the solar corona. Title: Signatures of the non-Maxwellian κ-distributions in optically thin line spectra. II. Synthetic Fe XVII-XVIII X-ray coronal spectra and predictions for the Marshall Grazing-Incidence X-ray Spectrometer (MaGIXS) Authors: Dudík, Jaroslav; Dzifčáková, Elena; Del Zanna, Giulio; Mason, Helen E.; Golub, Leon L.; Winebarger, Amy R.; Savage, Sabrina L. Bibcode: 2019A&A...626A..88D Altcode: 2019arXiv190510356D
Aims: We investigated the possibility of diagnosing the degree of departure from the Maxwellian distribution using the Fe XVII-Fe XVIII spectra originating in plasmas in collisional ionization equilibrium, such as in the cores of solar active regions or microflares.
Methods: The original collision strengths for excitation are integrated over the non-Maxwellian electron κ-distributions characterized by a high-energy tail. Synthetic X-ray emission line spectra were calculated for a range of temperatures and κ. We focus on the 6-24 Å spectral range to be observed by the upcoming Marshall Grazing-Incidence X-ray Spectrometer MaGIXS.
Results: We find that many line intensity ratios are sensitive to both T and κ. Best diagnostic options are provided if a ratio involving both Fe XVII and Fe XVIII is combined with another ratio involving lines formed within a single ion. The sensitivity of such diagnostics to κ is typically a few tens of per cent. Much larger sensitivity, of about a factor of two to three, can be obtained if the Fe XVIII 93.93 Å line observed by SDO/AIA is used in conjuction with the X-ray lines.
Conclusions: We conclude that the MaGIXS instrument is well-suited for detection of departures from the Maxwellian distribution, especially in active region cores. Title: Astrophysical Science enabled by Laboratory Astrophysics Studies in Atomic, Molecular, and Optical (AMO) Physics Authors: Savin, Daniel Wolf; Babb, James F.; Bellan, Paul M.; Brogan, Crystal; Cami, Jan; Caselli, Paola; Corrales, Lia; Dominguez, Gerardo; Federman, Steven R.; Fontes, Chris J.; Freedman, Richard; Gibson, Brad; Golub, Leon; Gorczyca, Thomas W.; Hahn, Michael; Hartmann, Dieter; Hörst, Sarah M.; Hudson, Reggie L.; Kuhn, Jeffrey; Lawler, James E.; Leutenegger, Maurice A.; Marler, Joan P.; McCarthy, Michael C.; McGuire, Brett A.; Milam, Stefanie N.; Murphy, Nicholas A.; Nave, Gillian; Norton, Aimee A.; Papol, Anthony; Raymond, John C.; Salama, Farid; Sciamma-O'Brien, Ella M.; Smith, Randall; Sosolik, Chad; Sousa-Silva, Clara; Stancil, Phillip C.; Timmes, Frank; Trimble, Virginia L.; Wargelin, Bradford J. Bibcode: 2019BAAS...51c..96S Altcode: 2019astro2020T..96S We highlight a few of the many astrophysical advances that will become possible with advances in AMO laboratory astrophysics. This submission supersedes the previous submission. Title: COSMO Science Authors: Gibson, Sarah; Tomczyk, Steven; Burkepile, Joan; Casini, Roberto; Deluca, Ed; de Toma, Giuliana; deWijn, Alfred; Fan, Yuhong; Golub, Leon; Judge, Philip; Landi, Enrico; Lin, Haosheng; McIntosh, Scott; Reeves, Kathy; Seaton, Dan; Zhang, Jie Bibcode: 2019shin.confE..32G Altcode: Space-weather forecast capability is held back by our current lack of basic scientific understanding of CME magnetic evolution, and the coronal magnetism that structures and drives the solar wind. Comprehensive observations of the global magnetothermal environment of the solar atmosphere are needed for progress. When fully implemented, the COSMO suite of synoptic ground-based telescopes will provide the community with comprehensive and simultaneous measurements of magnetism, temperature, density and plasma flows and waves from the photosphere through the chromosphere and out into the corona. We will discuss how these observations will uniquely address a set of science objectives that are central to the field of solar and space physics: in particular, to understand the storage and release of magnetic energy, to understand CME dynamics and consequences for shocks, to determine the role of waves in solar atmospheric heating and solar wind acceleration, to understand how the coronal magnetic field relates to the solar dynamo, and to constrain and improve space-weather forecast models. Title: Solar Coronal Structure: Loops, Clouds, or Both? Authors: Golub, Leon; Asgari-Targhi, Mahboubeh; Coppi, Bruno; Basu, Bamandas Bibcode: 2019RNAAS...3....4G Altcode: 2019RNAAS...3a...4G No abstract at ADS Title: Perspectives on Astrophysics Based on Atomic, Molecular, and Optical (AMO) Techniques Authors: Savin, Daniel Wolf; Babb, James F.; Bellan, Paul M.; Brogan, Crystal; Cami, Jan; Caselli, Paola; Corrales, Lia; Dominguez, Gerardo; Federman, Steven R.; Fontes, Chris J.; Freedman, Richard; Gibson, Brad; Golub, Leon; Gorczyca, Thomas W.; Hahn, Michael; Hörst, Sarah M.; Hudson, Reggie L.; Kuhn, Jeffrey; Lawler, James E.; Leutenegger, Maurice A.; Marler, Joan P.; McCarthy, Michael C.; McGuire, Brett A.; Milam, Stefanie N.; Murphy, Nicholas A.; Nave, Gillian; Norton, Aimee A.; Papol, Anthony; Raymond, John C.; Salama, Farid; Sciamma-O'Brien, Ella M.; Smith, Randall; Sosolik, Chad; Sousa-Silva, Clara; Stancil, Phillip C.; Timmes, Frank; Trimble, Virginia L.; Wargelin, Bradford J. Bibcode: 2018arXiv181106157S Altcode: About two generations ago, a large part of AMO science was dominated by experimental high energy collision studies and perturbative theoretical methods. Since then, AMO science has undergone a transition and is now dominated by quantum, ultracold, and ultrafast studies. But in the process, the field has passed over the complexity that lies between these two extremes. Most of the Universe resides in this intermediate region. We put forward that the next frontier for AMO science is to explore the AMO complexity that describes most of the Cosmos. Title: Book Review: The Sun Authors: Golub, Leon; Pasachoff, Jay M. Bibcode: 2018JAHH...21..241C Altcode: No abstract at ADS Title: Predicting the COSIE-C Signal from the Outer Corona up to 3 Solar Radii Authors: Del Zanna, Giulio; Raymond, John; Andretta, Vincenzo; Telloni, Daniele; Golub, Leon Bibcode: 2018ApJ...865..132D Altcode: 2018arXiv180807951D We present estimates of the signal to be expected in quiescent solar conditions, as would be obtained with the COronal Spectrographic Imager in the EUV in its coronagraphic mode (COSIE-C). COSIE-C has been proposed to routinely observe the relatively unexplored outer corona, where we know that many fundamental processes affecting both the lower corona and the solar wind are taking place. The COSIE-C spectral band, 186-205 Å, is well-known as it has been observed with Hinode EIS. We present Hinode EIS observations that we obtained in 2007 out to 1.5 R ⊙, to show that this spectral band in quiescent streamers is dominated by Fe XII and Fe XI and that the ionization temperature is nearly constant. To estimate the COSIE-C signal in the 1.5-3.1 R ⊙ region we use a model based on CHIANTI atomic data and SoHO UVCS observations in the Si XII and Mg X coronal lines of two quiescent 1996 streamers. We reproduce the observed EUV radiances with a simple density model, photospheric abundances, and a constant temperature of 1.4 MK. We show that other theoretical or semi-empirical models fail to reproduce the observations. We find that the coronal COSIE-C signal at 3 R ⊙ should be about 5 counts/s per 3.″1 pixel in quiescent streamers. This is unprecedented and opens up a significant discovery space. We also briefly discuss stray light and the visibility of other solar features. In particular, we present UVCS observations of an active region streamer, indicating increased signal compared to the quiet Sun cases. Title: Polar Coronal Plumes as Tornado-like Jets Authors: Tavabi, E.; Koutchmy, S.; Golub, L. Bibcode: 2018ApJ...866...35T Altcode: 2018arXiv180807322T We examine the dynamical behavior of white-light polar-plume structures in the inner corona that are observed from the ground during total solar eclipses, based on their extreme ultraviolet (EUV) hot and cool emission line counterparts observed from space. EUV observations from Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) of a sequence of rapidly varying coronal hole structures are analyzed. Evidence of events showing acceleration in the 1.25 Mk line of Fe XII at 193 Å is given. The structures along the plume show an outward velocity of about 140 km s-1 that can be interpreted as an upward propagating wave in the 304 Å and 171 Å lines; higher speeds are seen in 193 Å (up to 1000 km s-1). The ejection of the cold He II plasma is delayed by about 4 minutes in the lowest layer and is delayed more than 12 minutes in the highest level compared to the hot 193 Å behavior. A study of the dynamics using time-slice diagrams reveals that a large amount of fast ejected material originates from below the plume, at the footpoints. The release of plasma material appears to come from a cylinder with quasi-parallel edge-enhanced walls. After the initial phase of a longitudinal acceleration, the speed substantially reduces, and the ejecta disperse into the environment. Finally, the detailed temporal and spatial relationships between the cool and hot components were studied with simultaneous multiwavelength observations, using more AIA data. The outward-propagating perturbation of the presumably magnetic walls of polar plumes supports the suggestion that Alfvén waves propagate outwardly along these radially extended walls. Title: The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) Authors: Kobayashi, Ken; Winebarger, Amy R.; Savage, Sabrina; Champey, Patrick; Cheimets, Peter N.; Hertz, Edward; Bruccoleri, Alexander R.; Scholvin, Jorg; Golub, Leon; Ramsey, Brian; Ranganathan, Jaganathan; Marquez, Vanessa; Allured, Ryan; Parker, Theodore; Heilmann, Ralf K.; Schattenburg, Mark L. Bibcode: 2018SPIE10699E..27K Altcode: The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) is a NASA sounding rocket instrument designed to obtain spatially resolved soft X-ray spectra of the solar atmosphere in the 6-24 Å (0.5-2.0 keV) range. The instrument consists of a single shell Wolter Type-I telescope, a slit, and a spectrometer comprising a matched pair of grazing incidence parabolic mirrors and a planar varied-line space diffraction grating. The instrument is designed to achieve a 50 mÅ spectral resolution and 5 arcsecond spatial resolution along a +/-4-arcminute long slit, and launch is planned for 2019. We report on the status and our approaches for fabrication and alignment for this novel optical system. The telescope and spectrometer mirrors are replicated nickel shells, and are currently being fabricated at the NASA Marshall Space Flight Center. The diffraction grating is currently under development by the Massachusetts Institute of Technology (MIT); because of the strong line spacing variation across the grating, it will be fabricated through e-beam lithography. Title: Eclipse Science from 50,000 Feet: New Coronal Results from NASA WB-57F High-Altitude Aircraft Observations of the 2017 Total Solar Eclipse Authors: Caspi, Amir; Tsang, Constantine; Seaton, Daniel B.; DeForest, Craig; Bryans, Paul; DeLuca, Edward; Tomczyk, Steven; Burkepile, Joan; Casey, Thomas Anthony; Collier, John; Darrow, Donald DD; Del Rosso, Dominic; Durda, Daniel D.; Gallagher, Peter; Gascar, Jasmine; Golub, Leon; Jacyna, Matthew; Johnson, David DJ; Judge, Philip G.; Klemm, Cary; Laurent, Glenn Thomas; Lewis, Johanna; Mallini, Charles; Parent, Thomas Duster; Propp, Timothy; Steffl, Andrew; Warner, Jeff; West, Matthew John; Wiseman, John; Yates, Mallory; Zhukov, Andrei Bibcode: 2018tess.conf31302C Altcode: Total solar eclipses present rare opportunities to study the complex solar corona, down to altitudes of just a few percent of a solar radius above the surface. Studying the corona is critical to gaining a better understanding of the dominant driver of space weather that affects human assets on Earth and elsewhere. For example, it is still poorly understood how the corona is heated to temperatures of 1-2 MK globally and up to 5-10 MK above active regions, while the underlying chromosphere is 100 times cooler. The stability of large-scale coronal structures and the extent of their reach to the middle and outer corona are also not well known, limited in large part by sensitivities and fields of view of existing observations.

Airborne observations during a total eclipse provide unique advantages. By flying in the stratosphere at altitudes of 50 kft or higher, they avoid all weather, the seeing quality is enormously improved, and additional wavelengths such as near-IR also become available due to significantly reduced water absorption. An airborne observatory can also follow the Moon's shadow, increasing the total observing time by 50% or more.

We present current results of solar coronal measurements from airborne observations of the 2017 Great American Total Solar Eclipse using two of NASA's WB-57 high-altitude research aircraft, each equipped with two 8.7-inch telescopes feeding high-sensitivity visible (green line and nearby continuum) and medium-wave IR (3-5 μm) cameras operating at high cadence (30 Hz) with ∼3 arcsec/pixel platescale and ±3 Rsun fields of view. The two aircraft flew along the eclipse path, separated by ∼110 km, to observe a total of ∼7.5 minutes of totality in both visible and MWIR. These observations enable groundbreaking studies of high-speed coherent motion - including possible Alfvén waves and nanojets - in the lower and middle corona that could shed light on coronal heating processes and the formation and stability of coronal structures. Our MWIR observations of a cool prominence and hot coronal active region plasma will be combined with spectra from the AIR-Spec instrument, flown concurrently on NCAR's HIAPER GV. We review the WB-57 eclipse mission and the current results of analysis on the visible and IR coronal measurements, along with an outlook for future analysis and missions. Title: Using DSG to build the capability of space weather forecasting in deep space. Authors: DeLuca, Edward; Golub, Leon; Korreck, Kelly; Savage, Sabrina L.; McKenzie, David E.; Rachmeler, Laurel; Winebarger, Amy R.; Martens, Petrus C. Bibcode: 2018tess.conf22002D Altcode: The prospect of astronaut missions to deep space and off the sun-earth line raises new challenges for space weather awareness and forecasting. Combined efforts of the science and human flight communities are needed to identify the requirements and identify pathways that will allow us to address the requirements for protecting human life and equipment, on a timescale consistent with the deep space exploration program. <p class="p1" The Deep Space Gateway provides a platform where we can develop, test and validate a combined space weather instrumentation, analysis and forecasting system that can be used when out of routine contact with near earth based assets. This presentation will attempt to outline the bounds of the problem and start the discussion about how to build an independent space weather program. Title: Editorial: Data: Insights and Challenges in a Time of Abundance Authors: Timmes, Frank; Golub, Leon Bibcode: 2018ApJS..236....1T Altcode: No abstract at ADS Title: CisLunar Interchangeable Observatory for Heliophysics (CLIOH): A Deep Space Gateway Solar Viewing Platform for Technology Development and Research Payloads Authors: Savage, S.; DeLuca, E.; Cheimets, P.; Golub, L.; Kobayashi, K.; McKenzie, D.; Rachmeler, L.; Winebarger, A. Bibcode: 2018LPICo2063.3061S Altcode: The Deep Space Gateway offers an unparalleled opportunity to test and operate solar instrumentation in a radiation hard environment, which can be achieved via an external pointing platform designed to accommodate multiple interchangeable payloads. Title: Using DSG to Build the Capability of Space Weather Forecasting in Deep Space Authors: DeLuca, E. E.; Golub, L.; Korreck, K.; Savage, S.; McKenzie, D. D.; Rachmeler, L.; Winebarger, A.; Martens, P. Bibcode: 2018LPICo2063.3050D Altcode: The prospect of astronaut missions to deep space and off the Sun-Earth line raises new challenges for space weather awareness and forecasting. We need to identify the requirements and pathways that will allow us to protect human life and equipment. Title: The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) Authors: Winebarger, A. R.; Savage, S. L.; Kobayashi, K.; Champey, P. R.; McKenzie, D. E.; Golub, L.; Testa, P.; Reeves, K.; Cheimets, P.; Cirtain, J. W.; Walsh, R. W.; Bradshaw, S. J.; Warren, H.; Mason, H. E.; Del Zanna, G. Bibcode: 2017AGUFMSH44A..06W Altcode: For over four decades, X-ray, EUV, and UV spectral observations have been used to measure physical properties of the solar atmosphere. At wavelengths below 10 nm, however, observations of the solar corona with simultaneous spatial and spectral resolution are limited, and not since the late 1970's have spatially resolved solar X-ray spectra been measured. Because the soft X-ray regime is dominated by emission lines formed at high temperatures, X-ray spectroscopic techniques yield insights to fundamental physical processes that are not accessible by any other means. Using a novel implementation of corrective optics, the Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) will measure, for the first time, the solar spectrum from 0.6- 2.4 nm with a 6 arcsec resolution over an 8 arcmin slit. The MaGIXS mission will address on of the fundamental problems of coronal physics: the nature of coronal heating. There are several observables in the MaGIXS wavelength range that will constrain the heating frequency and hence discriminate between competing coronal heating theories. In this presentation, we will present the MaGIXS scientific motivation and provide an update on instrument development. MaGIXS will be launched from White Sands Missile Range in the summer of 2019. Title: Chasing the Great American 2017 Total Solar Eclipse: Coronal Results from NASA's WB-57F High-Altitude Research Aircraft Authors: Caspi, A.; Tsang, C.; DeForest, C. E.; Seaton, D. B.; Bryans, P.; Burkepile, J.; Casey, T. A.; Collier, J.; Darrow, D.; DeLuca, E.; Durda, D. D.; Gallagher, P.; Golub, L.; Judge, P. G.; Laurent, G. T.; Lewis, J.; Mallini, C.; Parent, T.; Propp, T.; Steffl, A.; Tomczyk, S.; Warner, J.; West, M. J.; Wiseman, J.; Zhukov, A. Bibcode: 2017AGUFMSH24A..05C Altcode: Total solar eclipses present rare opportunities to study the complex solar corona, down to altitudes of just a few percent of a solar radius above the surface, using ground-based and airborne observatories that would otherwise be dominated by the intense solar disk and high sky brightness. Studying the corona is critical to gaining a better understanding of physical processes that occur on other stars and astrophysical objects, as well as understanding the dominant driver of space weather that affects human assets at Earth and elsewhere. For example, it is still poorly understood how the corona is heated to temperatures of 1-2 MK globally and up to 5-10 MK above active regions, while the underlying chromosphere is 100 times cooler; numerous theories abound, but are difficult to constrain due to the limited sensitivities and cadences of prior measurements. The origins and stability of coronal fans, and the extent of their reach to the middle and outer corona, are also not well known, limited in large part by sensitivities and fields of view of existing observations. Airborne observations during the eclipse provide unique advantages; by flying in the stratosphere at altitudes of 50 kft or higher, they avoid all weather, the seeing quality is enormously improved, and additional wavelengths such as near- IR also become available due to significantly reduced water absorption. For an eclipse, an airborne observatory can also follow the shadow, increasing the total observing time by 50% or more. We present results of solar coronal measurements from airborne observations of the 2017 Great American Total Solar Eclipse using two of NASA's WB-57 high-altitude research aircraft, each equipped with two 8.7" telescopes feeding high-sensitivity visible (green-line) and medium-wave IR (3-5 μm) cameras operating at high cadence (30 Hz) with 3 arcsec/pixel platescale and ±3 R_sun fields of view. The aircraft flew along the eclipse path, separated by 110 km, to observe a summed 7.5 minutes of totality in both visible and NIR, enabling groundbreaking studies of high-speed wave motions and nanojets in the lower corona, the structure and extent of coronal fans, and constraints on a potential primordial dust ring around the Sun. We review the mission, and the results of analysis on the visible and IR coronal measurements. Title: ASPIRE - Airborne Spectro-Polarization InfraRed Experiment Authors: DeLuca, E.; Cheimets, P.; Golub, L.; Madsen, C. A.; Marquez, V.; Bryans, P.; Judge, P. G.; Lussier, L.; McIntosh, S. W.; Tomczyk, S. Bibcode: 2017AGUFMSH13B2480D Altcode: Direct measurements of coronal magnetic fields are critical for taking the next step in active region and solar wind modeling and for building the next generation of physics-based space-weather models. We are proposing a new airborne instrument to make these key observations. Building on the successful Airborne InfraRed Spectrograph (AIR-Spec) experiment for the 2017 eclipse, we will design and build a spectro-polarimeter to measure coronal magnetic field during the 2019 South Pacific eclipse. The new instrument will use the AIR-Spec optical bench and the proven pointing, tracking, and stabilization optics. A new cryogenic spectro-polarimeter will be built focusing on the strongest emission lines observed during the eclipse. The AIR-Spec IR camera, slit jaw camera and data acquisition system will all be reused. The poster will outline the optical design and the science goals for ASPIRE. Title: Endogenous Magnetic Reconnection in Solar Coronal Loops Authors: Asgari-Targhi, M.; Coppi, B.; Basu, B.; Fletcher, A.; Golub, L. Bibcode: 2017AGUFMSH11A2420A Altcode: We propose that a magneto-thermal reconnection process occurring in coronal loops be the source of the heating of the Solar Corona [1]. In the adopted model, magnetic reconnection is associated with electron temperature gradients, anisotropic electron temperature fluctuations and plasma current density gradients [2]. The input parameters for our theoretical model are derived from the most recent observations of the Solar Corona. In addition, the relevant (endogenous) collective modes can produce high energy particle populations. An endogenous reconnection process is defined as being driven by factors internal to the region where reconnection takes place. *Sponsored in part by the U.S. D.O.E. and the Kavli Foundation* [1] Beafume, P., Coppi, B. and Golub, L., (1992) Ap. J. 393, 396. [2] Coppi, B. and Basu, B. (2017) MIT-LNS Report HEP 17/01. Title: Eclipse Science Results from the Airborne Infrared Spectrometer (AIR-Spec) Authors: Samra, J.; Cheimets, P.; DeLuca, E.; Golub, L.; Judge, P. G.; Lussier, L.; Madsen, C. A.; Marquez, V.; Tomczyk, S.; Vira, A. Bibcode: 2017AGUFMSH24A..06S Altcode: We present the first science results from the commissioning flight of the Airborne Infrared Spectrometer (AIR-Spec), an innovative solar spectrometer that will observe the 2017 solar eclipse from the NSF/NCAR High-Performance Instrumented Airborne Platform for Environmental Research (HIAPER). During the eclipse, AIR-Spec will image five magnetically sensitive coronal emission lines between 1.4 and 4 microns to determine whether they may be useful probes of coronal magnetism. The instrument will measure emission line intensity, FWHM, and Doppler shift from an altitude of over 14 km, above local weather and most of the absorbing water vapor. Instrumentation includes an image stabilization system, feed telescope, grating spectrometer, infrared camera, and visible slit-jaw imager. Results from the 2017 eclipse are presented in the context of the mission's science goals. AIR-Spec will identify line strengths as a function of position in the solar corona and search for the high frequency waves that are candidates for heating and acceleration of the solar wind. The instrument will also identify large scale flows in the corona, particularly in polar coronal holes. Three of the five lines are expected to be strong in coronal hole plasmas because they are excited in part by scattered photospheric light. Line profile analysis will probe the origins of the fast and slow solar wind. Finally, the AIR-Spec measurements will complement ground based eclipse observations to provide detailed plasma diagnostics throughout the corona. AIR-Spec will measure infrared emission of ions observed in the visible from the ground, giving insight into plasma heating and acceleration at radial distances inaccessible to existing or planned spectrometers. Title: The Marshall Grazing Incidence X-ray Spectrometer Authors: Kobayashi, Ken; Winebarger, Amy R.; Savage, Sabrina; Champey, Patrick; Cheimets, Peter N.; Hertz, Edward; Bruccoleri, Alexander R.; Golub, Leon; Ramsey, Brian; Ranganathan, Jaganathan; Marquez, Vanessa; Allured, Ryan; Parker, Theodore; Heilmann, Ralf K.; Schattenburg, Mark L. Bibcode: 2017SPIE10397E..1IK Altcode: The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) is a NASA sounding rocket instrument designed to obtain spatially resolved soft X-ray spectra of the solar atmosphere in the 6-24 Å (0.5-2.0 keV) range. The instrument consists of a single shell Wolter Type-I telescope, a slit, and a spectrometer comprising a matched pair of grazing incidence parabolic mirrors and a planar varied-line space diffraction grating. The instrument is designed to achieve a 50 mÅ spectral resolution and 5 arcsecond spatial resolution along a +/-4-arcminute long slit, and launch is planned for 2019. We report on the status and our approaches for fabrication and alignment for this novel optical system. The telescope and spectrometer mirrors are replicated nickel shells, and are currently being fabricated at the NASA Marshall Space Flight Center. The diffraction grating is currently under development by the Massachusetts Institute of Technology (MIT); because of the strong line spacing variation across the grating, it will be fabricated through e-beam lithography. Title: First results from the NASA WB-57 airborne observations of the Great American 2017 Total Solar Eclipse Authors: Caspi, Amir; Tsang, Constantine; DeForest, Craig; Seaton, Daniel B.; Bryans, Paul; Tomczyk, Steven; Burkepile, Joan; Judge, Phil; DeLuca, Edward E.; Golub, Leon; Gallagher, Peter T.; Zhukov, Andrei; West, Matthew; Durda, Daniel D.; Steffl, Andrew J. Bibcode: 2017SPD....4810701C Altcode: Total solar eclipses present rare opportunities to study the complex solar corona, down to altitudes of just a few percent of a solar radius above the surface, using ground-based and airborne observatories that would otherwise be dominated by the intense solar disk and high sky brightness. Studying the corona is critical to gaining a better understanding of physical processes that occur on other stars and astrophysical objects, as well as understanding the dominant driver of space weather that affects human assets at Earth and elsewhere. For example, it is still poorly understood how the corona is heated to temperatures of 1-2 MK globally and up to 5-10 MK above active regions, while the underlying chromosphere is 100 times cooler; numerous theories abound, but are difficult to constrain due to the limited sensitivities and cadences of prior measurements. The origins and stability of coronal fans, and the extent of their reach to the middle and outer corona, are also not well known, limited in large part by sensitivities and fields of view of existing observations.Airborne observations during the eclipse provide unique advantages; by flying in the stratosphere at altitudes of 50 kft or higher, they avoid all weather, the seeing quality is enormously improved, and additional wavelengths such as near-IR also become available due to significantly reduced water absorption. For an eclipse, an airborne observatory can also follow the shadow, increasing the total observing time by 50% or more.We present the first results from airborne observations of the 2017 Great American Total Solar Eclipse using two of NASA's WB-57 research aircraft, each equipped with two 8.7" telescopes feeding high-sensitivity visible (green-line) and near-IR (3-5 µm) cameras operating at high cadence (30 Hz) with ~3 arcsec/pixel platescale and ±3 R_sun fields of view. The aircraft will fly along the eclipse path, separated by ~90 km, to observe a summed ~8 minutes of totality in both visible and NIR, enabling groundbreaking studies of high-speed wave motions and nanojets in the lower corona, the structure and extent of coronal fans, and constraints on a potential primordial dust ring around the Sun. Title: Solving the Coronal Heating Problem using X-ray Microcalorimeters Authors: Christe, Steven; Bandler, Simon; DeLuca, Edward; Caspi, Amir; Golub, Leon; Smith, Randall; Allred, Joel; Brosius, Jeffrey W.; Dennis, Brian; Klimchuk, James Bibcode: 2017arXiv170100795C Altcode: Even in the absence of resolved flares, the corona is heated to several million degrees. However, despite its importance for the structure, dynamics, and evolution of the solar atmosphere, the origin of this heating remains poorly understood. Several observational and theoretical considerations suggest that the heating is driven by small, impulsive energy bursts which could be Parker-style "nanoflares" (Parker 1988) that arise via reconnection within the tangled and twisted coronal magnetic field. The classical "smoking gun" (Klimchuk 2009; Cargill et al. 2013) for impulsive heating is the direct detection of widespread hot plasma (T > 6 MK) with a low emission measure. In recent years there has been great progress in the development of Transition Edge Sensor (TES) X-ray microcalorimeters that make them more ideal for studying the Sun. When combined with grazing-incidence focusing optics, they provide direct spectroscopic imaging over a broad energy band (0.5 to 10 keV) combined with extremely impressive energy resolution in small pixels, as low as 0.7 eV (FWHM) at 1.5 keV (Lee 2015), and 1.56 eV (FWHM) at 6 keV (Smith 2012), two orders of magnitude better than the current best traditional solid state photon-counting spectrometers. Decisive observations of the hot plasma associated with nanoflare models of coronal heating can be provided by new solar microcalorimeters. These measurements will cover the most important part of the coronal spectrum for searching for the nanoflare-related hot plasma and will characterize how much nanoflares can heat the corona both in active regions and the quiet Sun. Finally, microcalorimeters will enable to study all of this as a function of time and space in each pixel simultaneously a capability never before available. Title: MWA Observations of Solar Radio Bursts and the Quiet Sun Authors: Cairns, I.; Oberoi, D.; Morgan, J.; Bastian, T.; Bhatnagar, S.; Bisi, M.; Benkevitch, L.; Bowman, J.; Donea, A.; Giersch, O.; Jackson, B.; Chat, G. L.; Golub, L.; Hariharan, K.; Herne, D.; Kasper, J.; Kennewell, J.; Lonsdale, C.; Lobzin, V.; Matthews, L.; Mohan, A.; Padmanabhan, J.; Pankratius, V.; Pick, M.; Subramanian, P.; Ramesh, R.; Raymond, J.; Reeves, K.; Rogers, A.; Sharma, R.; Tingay, S.; Tremblay, S.; Tripathi, D.; Webb, D.; White, S.; Abidin, Z. B. Z. Bibcode: 2017mwa..prop..A06C Altcode: A hundred hours of observing time for solar observations is requested during the 2017-A observing semester. These data will be used to address science objectives for solar burst science (Goal A), studies of weak non-thermal radiation (Goal B) and quiet sun science (Goal C). Goal A will focus on detailed investigations of individual events seen in the MWA data, using the unsurpassed spectroscopic imaging ability of the MWA to address some key solar physics questions. Detailed observations of type II bursts, of which MWA has observed two, will be one focus, with MWA polarimetric imaging observations of type III bursts another focus. Goal B will address studies of the numerous short lived and narrow band emission features, significantly weaker than those seen by most other instruments revealed by the MWA. These emission features do not resemble any known types of solar bursts, but are possible signatures of "nanoflares" which have long been suspected to play a role in coronal heating. A large database of these events is needed to be able to reliably estimate their contribution to coronal heating. These observations will contribute to this database. Goal C will focus on characterizing the Sun's background thermal emission, their short and long term variability and looking for evidence of a scattering disc around the Sun. Title: Development of the User Interface for AIR-Spec Authors: Cervantes Alcala, E.; Guth, G.; Fedeler, S.; Samra, J.; Cheimets, P.; DeLuca, E.; Golub, L. Bibcode: 2016AGUFMSM51A2458C Altcode: The airborne infrared spectrometer (AIR-Spec) is an imaging spectrometer that will observe the solar corona during the 2017 total solar eclipse. This eclipse will provide a unique opportunity to observe infrared emission lines in the corona. Five spectral lines are of particular interest because they may eventually be used to measure the coronal magnetic field. To avoid infrared absorption from atmospheric water vapor, AIR-Spec will be placed on an NSF Gulfstream aircraft flying above 14.9 km. AIR-Spec must be capable of taking stable images while the plane moves. The instrument includes an image stabilization system, which uses fiber-optic gyroscopes to determine platform rotation, GPS to calculate the ephemeris of the sun, and a voltage-driven mirror to correct the line of sight. An operator monitors a white light image of the eclipse and manually corrects for residual drift. The image stabilization calculation is performed by a programmable automatic controller (PAC), which interfaces with the gyroscopes and mirror controller. The operator interfaces with a separate computer, which acquires images and computes the solar ephemeris. To ensure image stabilization is successful, a human machine interface (HMI) was developed to allow connection between the client and PAC. In order to make control of the instruments user friendly during the short eclipse observation, a graphical user interface (GUI) was also created. The GUI's functionality includes turning image stabilization on and off, allowing the user to input information about the geometric setup, calculating the solar ephemeris, refining estimates of the initial aircraft attitude, and storing data from the PAC on the operator's computer. It also displays time, location, attitude, ephemeris, gyro rates and mirror angles. Title: COSIE: A Wide-field EUV Imager and Spectrograph for the ISS Authors: Golub, L.; Savage, S. L. Bibcode: 2016AGUFMSH31C..08G Altcode: We propose a novel dual-use EUV imager designed to observe the dynamics of the solar corona from the solar surface out to 3 R_sol. The COSIE instrument is proposed as an MoO within the SMEX program, with the objectives of: 1.) understanding the dynamics of the Transition Corona, the region of the upper corona in which the plasma beta changes from low to high and the atmosphere transitions from being dominated by magnetically confined closed structures to high beta with generally open radially-directed regions with outflowing solar wind streams; 2.) providing new tools for space weather forecasting via early detection of coronal mass ejections (CMEs), determination of early acceleration and path changes, and modelling of the CME magnetic configuration at event initiation. The observing mode is switchable via a mechanism that switches between ultra-high sensitivity direct imaging and a spectroscopic imaging mode with the goal of understanding the dynamics of the evolving CME structure and of high temperature plasma above and around active regions. COSIE is intended to mount to the ISS, tracking the Sun continuously during its daylight passes. Title: The importance of high-resolution observations of the solar corona Authors: Winebarger, A. R.; Cirtain, J. W.; Golub, L.; Walsh, R. W.; De Pontieu, B.; Savage, S. L.; Rachmeler, L.; Kobayashi, K.; Testa, P.; Brooks, D.; Warren, H.; Mcintosh, S. W.; Peter, H.; Morton, R. J.; Alexander, C. E.; Tiwari, S. K. Bibcode: 2016AGUFMSH31B2577W Altcode: The spatial and temporal resolutions of the available coronal observatories are inadequate to resolve the signatures of coronal heating. High-resolution and high-cadence observations available with the Interface Region Imaging Spectrograph (IRIS) and the High-resolution Coronal Imager (Hi-C) instrument hint that 0.3 arcsec resolution images and < 10 s cadence provide the necessary resolution to detect heating events. Hi-C was launched from White Sands Missile Range on July 11, 2012 (before the launch with IRIS) and obtained images of a solar active region in the 19.3 nm passband. In this presentation, I will discuss the potential of combining a flight in Hi-C with a 17.1 nm passband, in conjunction with IRIS. This combination will provide, for the first time, a definitive method of tracing the energy flow between the chromosphere and corona and vice versa. Title: An Airborne Infrared Spectrometer for Solar Eclipse Observations Authors: DeLuca, E.; Samra, J.; Golub, L.; Cheimets, P. Bibcode: 2016AGUFMSM51A2457D Altcode: The airborne infrared spectrometer (AIR-Spec) is an innovative solar spectrometer that will observe the 2017 solar eclipse from the NSF/NCAR High-Performance Instrumented Airborne Platform for Environmental Research (HIAPER). AIR-Spec will image five infrared coronal emission lines to determine whether they may be useful probes of coronal magnetism. AIR-Spec consists of an optical system (feed telescope and a cooled grating spectrometer and infrared detector) and an image stabilization system, which uses a fast steering mirror to correct the line-of-sight for platform perturbations. To ensure that the instrument meets its research goals, both systems are undergoing extensive performance modeling and testing. We will present preliminary results of November flight tests of the image stabilization systems, a critical component of the program. Title: Solar Wind Electrons Alphas and Protons (SWEAP) Investigation: Design of the Solar Wind and Coronal Plasma Instrument Suite for Solar Probe Plus Authors: Kasper, Justin C.; Abiad, Robert; Austin, Gerry; Balat-Pichelin, Marianne; Bale, Stuart D.; Belcher, John W.; Berg, Peter; Bergner, Henry; Berthomier, Matthieu; Bookbinder, Jay; Brodu, Etienne; Caldwell, David; Case, Anthony W.; Chandran, Benjamin D. G.; Cheimets, Peter; Cirtain, Jonathan W.; Cranmer, Steven R.; Curtis, David W.; Daigneau, Peter; Dalton, Greg; Dasgupta, Brahmananda; DeTomaso, David; Diaz-Aguado, Millan; Djordjevic, Blagoje; Donaskowski, Bill; Effinger, Michael; Florinski, Vladimir; Fox, Nichola; Freeman, Mark; Gallagher, Dennis; Gary, S. Peter; Gauron, Tom; Gates, Richard; Goldstein, Melvin; Golub, Leon; Gordon, Dorothy A.; Gurnee, Reid; Guth, Giora; Halekas, Jasper; Hatch, Ken; Heerikuisen, Jacob; Ho, George; Hu, Qiang; Johnson, Greg; Jordan, Steven P.; Korreck, Kelly E.; Larson, Davin; Lazarus, Alan J.; Li, Gang; Livi, Roberto; Ludlam, Michael; Maksimovic, Milan; McFadden, James P.; Marchant, William; Maruca, Bennet A.; McComas, David J.; Messina, Luciana; Mercer, Tony; Park, Sang; Peddie, Andrew M.; Pogorelov, Nikolai; Reinhart, Matthew J.; Richardson, John D.; Robinson, Miles; Rosen, Irene; Skoug, Ruth M.; Slagle, Amanda; Steinberg, John T.; Stevens, Michael L.; Szabo, Adam; Taylor, Ellen R.; Tiu, Chris; Turin, Paul; Velli, Marco; Webb, Gary; Whittlesey, Phyllis; Wright, Ken; Wu, S. T.; Zank, Gary Bibcode: 2016SSRv..204..131K Altcode: 2015SSRv..tmp..119K The Solar Wind Electrons Alphas and Protons (SWEAP) Investigation on Solar Probe Plus is a four sensor instrument suite that provides complete measurements of the electrons and ionized helium and hydrogen that constitute the bulk of solar wind and coronal plasma. SWEAP consists of the Solar Probe Cup (SPC) and the Solar Probe Analyzers (SPAN). SPC is a Faraday Cup that looks directly at the Sun and measures ion and electron fluxes and flow angles as a function of energy. SPAN consists of an ion and electron electrostatic analyzer (ESA) on the ram side of SPP (SPAN-A) and an electron ESA on the anti-ram side (SPAN-B). The SPAN-A ion ESA has a time of flight section that enables it to sort particles by their mass/charge ratio, permitting differentiation of ion species. SPAN-A and -B are rotated relative to one another so their broad fields of view combine like the seams on a baseball to view the entire sky except for the region obscured by the heat shield and covered by SPC. Observations by SPC and SPAN produce the combined field of view and measurement capabilities required to fulfill the science objectives of SWEAP and Solar Probe Plus. SWEAP measurements, in concert with magnetic and electric fields, energetic particles, and white light contextual imaging will enable discovery and understanding of solar wind acceleration and formation, coronal and solar wind heating, and particle acceleration in the inner heliosphere of the solar system. SPC and SPAN are managed by the SWEAP Electronics Module (SWEM), which distributes power, formats onboard data products, and serves as a single electrical interface to the spacecraft. SWEAP data products include ion and electron velocity distribution functions with high energy and angular resolution. Full resolution data are stored within the SWEM, enabling high resolution observations of structures such as shocks, reconnection events, and other transient structures to be selected for download after the fact. This paper describes the implementation of the SWEAP Investigation, the driving requirements for the suite, expected performance of the instruments, and planned data products, as of mission preliminary design review. Title: An airborne infrared spectrometer for solar eclipse observations Authors: Samra, Jenna; Cheimets, Peter; DeLuca, Edward; Galeros, John; Gauron, Thomas; Golub, Leon; Guth, Giora; Hertz, Edward; Judge, Philip; Koutchmy, Serge; Marquez, Vanessa Bibcode: 2016SPIE.9908E..5US Altcode: This paper presents the design of an innovative solar spectrometer that will y on the NSF/NCAR Gulfstream V High-Performance Instrumented Airborne Platform for Environmental Research (GV HIAPER) during the 2017 solar eclipse. The airborne infrared spectrometer (AIR-Spec) is groundbreaking in two aspects: it will image infrared coronal emission lines that have never been measured, and it will bring high resolution imaging to GV HIAPER. The instrument development faces the challenges of achieving adequate resolution and signal-to-noise ratio in a compact package mounted to a noisy moving platform. To ensure that AIR-Spec meets its research goals, the instrument is undergoing pre-flight modeling and testing. The results are presented with reference to the instrument requirements. Title: An Airborne Infrared Spectrometer for Solar Eclipse Observations Authors: Samra, Jenna; DeLuca, Edward; Golub, Leon; Cheimets, Peter; Judge, Philip Bibcode: 2016shin.confE.155S Altcode: The airborne infrared spectrometer (AIR-Spec) is an innovative solar spectrometer that will observe the 2017 solar eclipse from the NSF/NCAR High-Performance Instrumented Airborne Platform for Environmental Research (HIAPER). AIR-Spec will image five infrared coronal emission lines to determine whether they may be useful probes of coronal magnetism.

The solar magnetic field provides the free energy that controls coronal heating, structure, and dynamics. Energy stored in coronal magnetic fields is released in flares and coronal mass ejections and ultimately drives space weather. Therefore, direct coronal field measurements have significant potential to enhance understanding of coronal dynamics and improve solar forecasting models. Of particular interest are observations of field lines in the transitional region between closed and open flux systems, providing important information on the origin of the slow solar wind.

While current instruments routinely observe only the photospheric and chromospheric magnetic fields, AIR-Spec will take a step toward the direct observation of coronal fields by measuring plasma emission in the infrared at high spatial and spectral resolution. During the total solar eclipse of 2017, AIR-Spec will search for five magnetically sensitive coronal emission lines between 1.4 and 4 μm from the HIAPER Gulfstream V at an altitude above 14.9 km. The instrument will measure emission line intensity, width, and Doppler shift, map the spatial distribution of infrared emitting plasma, and search for waves in the emission line velocities.

AIR-Spec consists of an optical system (feed telescope, grating spectrometer, and infrared detector) and an image stabilization system, which uses a fast steering mirror to correct the line-of-sight for platform perturbations. To ensure that the instrument meets its research goals, both systems are undergoing extensive performance modeling and testing. These results are shown with reference to the science requirements. Title: On the alignment and focusing of the Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) Authors: Champey, Patrick; Winebarger, Amy; Kobayashi, Ken; Savage, Sabrina; Cirtain, Jonathan; Cheimets, Peter; Hertz, Edward; Golub, Leon; Ramsey, Brian; McCracken, Jeff; Marquez, Vanessa; Allured, Ryan; Heilmann, Ralf K.; Schattenburg, Mark; Bruccoleri, Alexander Bibcode: 2016SPIE.9905E..73C Altcode: The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) is a NASA sounding rocket instrument that is designed to observe soft X-ray emissions from 24 - 6.0 Å (0.5 - 2.0 keV energies) in the solar atmosphere. For the first time, high-temperature, low-emission plasma will be observed directly with 5 arcsecond spatial resolution and 22 mÅ spectral resolution. The unique optical design consists of a Wolter - I telescope and a 3-optic grazing- incidence spectrometer. The spectrometer utilizes a finite conjugate mirror pair and a blazed planar, varied line spaced grating, which is directly printed on a silicon substrate using e-beam lithography. The grating design is being finalized and the grating will be fabricated by the Massachusetts Institute of Technology (MIT) and Izentis LLC. Marshall Space Flight Center (MSFC) is producing the nickel replicated telescope and spectrometer mirrors using the same facilities and techniques as those developed for the ART-XC and FOXSI mirrors. The Smithsonian Astrophysical Observatory (SAO) will mount and align the optical sub-assemblies based on previous experience with similar instruments, such as the Hinode X-Ray Telescope (XRT). The telescope and spectrometer assembly will be aligned in visible light through the implementation of a theodolite and reference mirrors, in addition to the centroid detector assembly (CDA) - a device designed to align the AXAF-I nested mirrors. Focusing of the telescope and spectrometer will be achieved using the X-ray source in the Stray Light Facility (SLF) at MSFC. We present results from an alignment sensitivity analysis performed on the on the system and we also discuss the method for aligning and focusing MaGIXS. Title: An Airborne Infrared Spectrometer for Solar Eclipse Observations Authors: Samra, Jenna; DeLuca, Edward E.; Golub, Leon; Cheimets, Peter; Philip, Judge Bibcode: 2016SPD....4730106S Altcode: The airborne infrared spectrometer (AIR-Spec) is an innovative solar spectrometer that will observe the 2017 solar eclipse from the NSF/NCAR High-Performance Instrumented Airborne Platform for Environmental Research (HIAPER). AIR-Spec will image five infrared coronal emission lines to determine whether they may be useful probes of coronal magnetism.The solar magnetic field provides the free energy that controls coronal heating, structure, and dynamics. Energy stored in coronal magnetic fields is released in flares and coronal mass ejections and ultimately drives space weather. Therefore, direct coronal field measurements have significant potential to enhance understanding of coronal dynamics and improve solar forecasting models. Of particular interest are observations of field lines in the transitional region between closed and open flux systems, providing important information on the origin of the slow solar wind.While current instruments routinely observe only the photospheric and chromospheric magnetic fields, AIR-Spec will take a step toward the direct observation of coronal fields by measuring plasma emission in the infrared at high spatial and spectral resolution. During the total solar eclipse of 2017, AIR-Spec will observe five magnetically sensitive coronal emission lines between 1.4 and 4 µm from the HIAPER Gulfstream V at an altitude above 14.9 km. The instrument will measure emission line intensity, width, and Doppler shift, map the spatial distribution of infrared emitting plasma, and search for waves in the emission line velocities.AIR-Spec consists of an optical system (feed telescope, grating spectrometer, and infrared detector) and an image stabilization system, which uses a fast steering mirror to correct the line-of-sight for platform perturbations. To ensure that the instrument meets its research goals, both systems are undergoing extensive performance modeling and testing. These results are shown with reference to the science requirements. Title: A Wide-Field Coronal EUV Imager for the ISS Authors: Golub, Leon; Savage, Sabrina Bibcode: 2016SPD....47.0805G Altcode: We propose a novel dual-usage EUV imager designed to observe the solar corona from the solar surface out to ~3 R_sol, with the objectives of: 1. determining the dynamics of the Transition Corona, the region in which the corona changes from low-beta and dominated by magnetically confined closed structures to high beta and having generally open regions with outflowing solar wind streams and mostly radial streamer structures; 2. providing new tools for space weather forecasting via early detection of a coronal mass ejection (CME) eruption, early acceleration and path detection, and modelling of the CME magnetic structure and configuration at launch. The latter goal will be achieved in combination with ground-based measurements. A mechanism switches the observing mode to spectroscopic imaging with the goal of understanding the dynamics of CMEs and of high-temperature plasma above and around active regions. The instrument is intended to mount to the ISS, tracking the Sun continuously during its daylight passes, and will be proposed as a Mission of Opportunity within the SMEX program. Title: Is it Possible to Use the Green Coronal Line Instead of X rays to Cancel an Effect of the Coronal Emissivity Deficit in Estimation of the Prominence Total Mass from Decrease of the EUV-corona Intensities? Authors: Schwartz, P.; Heinzel, P.; Jejčič, S.; Rybák, J.; Kotrč, P.; Fárník, F.; Kupryakov, Yu. A.; Deluca, E. E.; Golub, L.; Jibben, P. R.; Anzer, U.; Tlatov, A. G. .; Guseva, S. A. Bibcode: 2016ASPC..504...89S Altcode: Total masses of six quiescent prominences observed from April through June 2011 were estimated using multi-spectral observations (in EUV, X-rays, Hα, and Ca <small>II</small> H). The method for the total mass estimation is based on the fact that the intensity of the EUV solar corona at wavelengths below 912 Å is reduced at a prominence by the absorption in resonance continua (photoionisation) of hydrogen and possibly by helium and subsequently an amount of absorbed radiation is proportional to the column density of hydrogen and helium plasma. Moreover, the deficit of the coronal emissivity in volume occupied by the cool prominence plasma also contributes to the intensity decrease. The observations in X-rays which are not absorbed by the prominence plasma, allow us to separate these two mechanisms from each other. The X-ray observations of XRT onboard the Hinode satellite made with the Al-mesh focal filter were used because the X-ray coronal radiation formed in plasma of temperatures of the order of 106 K was registered and EUV spectral lines occurring in the 193, 211 and 335 Å channels of the Atmospheric Imaging Assembly of the Solar Dynamics Observatory satellite are also formed at such temperatures. Unfortunately, the Al-mesh filter has a secondary peak of the transmittance at around 171 Å which causes a contribution from the EUV corona to the measured data of up to 11 % in the quiet corona. Thus, absorption in prominence plasma influences XRT X-ray data when using the Al-mesh filter. On the other hand, other X-ray XRT filters are more sensitive to plasma of much higher temperatures (log T of the order of 7), thus observations using these filters cannot be used together with the AIA observations in the method for mass estimations. This problem could be solved using observations in the green coronal line instead of X-rays. Absorption of the green coronal line by a prominence plasma is negligible and this line is formed at temperatures of the order of 106 K. We compare values of the total mass of the prominence observed on 20 October 2012 on the SE limb estimated when using XRT X-ray observations and observations in the green coronal line obtained at Kislovodsk Mountain Astronomical Station of the Pulkovo observatory (Russia). Title: Low-density laboratory spectra near the He II λ304 line Authors: Träbert, Elmar; Beiersdorfer, Peter; Brickhouse, Nancy S.; Golub, Leon Bibcode: 2016A&A...586A.115T Altcode:
Aims: To interpret the EUV spectra of the solar corona, one hopes for laboratory data of specific chemical elements obtained under coronal conditions.
Methods: EUV spectra of He, C, N, O, F, Ne, S, Ar, Fe, and Ni in a 40 Å wide wavelength interval near λ304 were excited in an electron beam ion trap.
Results: We observe some two hundred lines about half of which are not yet identified and included in spectral models.
Conclusions: Our data provide a check on the atomic data bases underlying the spectral models that are used to interpret solar corona data. However, a multitude of mostly weak additional lines taken together represent a flux that is comparable to that of various primary lines.

Research supported by the Solar and Heliospherical Physics Program of the National Aeronautics and Space Administration under award NNH10AN31I. Title: Simultaneous IRIS and Hinode/EIS Observations and Modelling of the 2014 October 27 X2.0 Class Flare Authors: Polito, V.; Reep, J. W.; Reeves, K. K.; Simões, P. J. A.; Dudík, J.; Del Zanna, G.; Mason, H. E.; Golub, L. Bibcode: 2016ApJ...816...89P Altcode: 2015arXiv151206378P We present a study of the X2-class flare which occurred on 2014 October 27 and was observed with the Interface Region Imaging Spectrograph (IRIS) and the EUV Imaging Spectrometer (EIS) on board the Hinode satellite. Thanks to the high cadence and spatial resolution of the IRIS and EIS instruments, we are able to compare simultaneous observations of the Fe xxi 1354.08 Å and Fe xxiii 263.77 Å high-temperature emission (≳10 MK) in the flare ribbon during the chromospheric evaporation phase. We find that IRIS observes completely blueshifted Fe xxi line profiles, up to 200 km s-1 during the rise phase of the flare, indicating that the site of the plasma upflows is resolved by IRIS. In contrast, the Fe xxiii line is often asymmetric, which we interpret as being due to the lower spatial resolution of EIS. Temperature estimates from SDO/AIA and Hinode/XRT show that hot emission (log(T[K]) > 7.2) is first concentrated at the footpoints before filling the loops. Density-sensitive lines from IRIS and EIS give estimates of electron number density of ≳1012 cm-3 in the transition region lines and 1010 cm-3 in the coronal lines during the impulsive phase. In order to compare the observational results against theoretical predictions, we have run a simulation of a flare loop undergoing heating using the HYDRAD 1D hydro code. We find that the simulated plasma parameters are close to the observed values that are obtained with IRIS, Hinode, and AIA. These results support an electron beam heating model rather than a purely thermal conduction model as the driving mechanism for this flare. Title: Airborne Infrared Spectrograph for Eclipse Observations Authors: Golub, L.; Cheimets, P.; DeLuca, E. E.; Samra, J.; Judge, P. G. Bibcode: 2015AGUFMSH51C2454G Altcode: Direct measurements of the coronal magnetic field have significant potential to enhance our understanding of coronal dynamics, and improve forecasting models. Of particular interest are observations of coronal field lines in the Transition Corona, the transitional region between closed and open flux systems, providing important information on eruptive instabilities and on the origin of the slow solar wind. While current instruments routinely observe the photospheric and chromospheric magnetic fields, the proposed airborne spectrometer will take a step toward the direct observation of coronal fields by measuring plasma emission in the infrared at high spatial and spectral resolution. The targeted lines are five forbidden magnetic dipole transitions between 1.4 and 4 um. The airborne system will consist of a telescope, grating spectrometer and pointing/stabilization system to be flown on the NSF/NCAR High-performance Instrumented Airborne Platform for Environmental Research (HIAPER) during the 21 August 2017 total solar eclipse. We will discuss the scientific objectives of the 2017 flight, describe details of the instrument design, and present the observing program for the eclipse. Title: The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) Authors: Champey, P. R.; Winebarger, A. R.; Kobayashi, K.; Savage, S. L.; Cirtain, J. W.; Cheimets, P.; Hertz, E.; Golub, L.; Ramsey, B.; McCracken, J.; Heilmann, R.; Schattenburg, M.; Bruccoleri, A. Bibcode: 2015AGUFMSH43B2458C Altcode: The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) is a NASA soundingrocket instrument designed to observe soft X-ray emissions at 0.5 - 2.0 keV energies in thesolar atmosphere. The primary science goal is to differentiate steady, low-frequency heatingevents from sporadic, high-frequency heating events in the active region core For the first time, high-temperature, low-emission plasma will be observed directly with 5 arcsec spatialand 22 mÅ spectral resolution. The novel optical design consists of a Wolter I telescope anda 3-optic grazing-incidence spectrograph. The X-ray spectrograph utilizes a finite conjugatemirror pair and a planar, nanoprinted-silicon varied line space grating, which is being devel-oped by the Massachusetts Institute of Technology (MIT). The telescope and spectrographmirrors will be nickel replicated and coated with iridium. Mandrel fabrication and nickelreplication will be done at MSFC as part of its replicated X-ray optics program. Mounting,alignment, and integration of the ight optics will be performed at the Harvard-SmithsonianCenter for Astrophysics (SAO). The MaGIXS science camera is being developed at MSFCand is based on CLASP heritage, which obtained read noise performance of 5.5 e?- RMS. Thecamera will include a e2v Technologies 2kx2k frame transfer CCD with 4-channel readout(500 kpixel/s/channel). We will present an overview of the MaGIXS optical system andfabrication of the telescope and spectrograph mirrors. Title: Limb Event Brightenings and Fast Ejection Using IRIS Mission Observations Authors: Tavabi, E.; Koutchmy, S.; Golub, L. Bibcode: 2015SoPh..290.2871T Altcode: 2015SoPh..tmp..118T; 2015arXiv150706794T The Interface Region Imaging Spectrograph (IRIS) of the recently commissioned NASA small explorer mission provides significantly more complete and higher resolution spectral coverage of the dynamical conditions inside the chromosphere and transition region (TR) than has been available ever before. High temporal, spatial (0.3″) and spectral resolution observations from the ultraviolet IRIS spectra near the solar limb reveal high-energy limb event brightenings (LEBs) at low chromospheric heights at about 1 Mm above the limb. They can be characterized as explosive events producing jets. We selected two events showing spectra of a confined eruption just off or near the quiet-Sun limb, the jet part showing obvious moving material with short-duration large Doppler shifts in three directions that were identified as macrospicules on slit-jaw (SJ) images in Si IV and He II 304 Å. The events were analyzed from a sequence of very close rasters taken near the central meridian and the South Pole limb. We analyzed the processed SJ images and the simultaneously observed fast spectral sequences, which have large Doppler shifts, with a pair of redshifted elements together with a faster blueshifted element from almost the same position. Shifts correspond to velocities of up to 100 kms−1 in projection on the plane of the sky. Erupting spicules and macrospicules from these regions are visible in images taken before and after the spectra. The cool low first ionization potential (FIP) element simultaneous line emissions of the Mg II h and k resonance lines do not clearly show a similar signature because of optical thickness effects, but the Si IV broadband SJ images do. The bidirectional plasma jets ejected from a small reconnection site are interpreted to be the result of coronal loop-loop interactions that lead to reconnection in nearby sites. Title: Book review: Nearest Star: The surprising science of our Sun (Golub & Pasachoff) Authors: Smith, L.; Golub, L.; Pasachoff, J. M. Bibcode: 2015JBAA..125..183S Altcode: No abstract at ADS Title: Joint High Temperature Observation of a Small C6.5 Solar Flare With Iris/Eis/Aia Authors: Polito, V.; Reeves, K. K.; Del Zanna, G.; Golub, L.; Mason, H. E. Bibcode: 2015ApJ...803...84P Altcode: We present the observation of a C6.5 class flare on 2014 February 3, obtained with the Interface Region Imaging Spectrograph (IRIS) and the EUV Imaging Spectrometer (EIS) on board HINODE. We follow the details of the impulsive phase with IRIS and the gradual decay phase with both IRIS and EIS. The IRIS Slit-Jaw Imager and Atmospheric Imaging Assembly (AIA) are used to precisely co-align the two sets of spectroscopic observations. Of particular interest is the Fe xxi 1354.08 Å spectral line, which is the highest temperature emission (∼10 MK) observed in the IRIS wavelength range. We show the evolution of the Fe xxi profiles during the impulsive phase of the flare at the same ribbon location with a 75 s temporal cadence. Totally blueshifted (∼82 km {{s}-1}) profiles are found at the very early phase of the flare and gradually decrease in about 6 minutes. This result is consistent with 1D model predictions during chromospheric evaporation in flares. The blueshifted components also exhibit large non-thermal broadening, which decreases simultaneously with the blueshifted velocity. After the evaporation first occurs, the Fe xxi intensity progressively moves from the footpoints to the top of the hot flare loops seen in the AIA 131 Å images, where the emission is observed to be at rest and thermal. Emission measure estimates from IRIS/EIS/AIA observations during the gradual phase show isothermal loop top structures cooling from about 13.5 to 12 MK with electron densities of the order of ∼ 5-6× {{10}10} c{{m}-3}. Title: Internetwork Chromospheric Bright Grains Observed With IRIS and SST Authors: Martínez-Sykora, Juan; Rouppe van der Voort, Luc; Carlsson, Mats; De Pontieu, Bart; Pereira, Tiago M. D.; Boerner, Paul; Hurlburt, Neal; Kleint, Lucia; Lemen, James; Tarbell, Ted D.; Title, Alan; Wuelser, Jean-Pierre; Hansteen, Viggo H.; Golub, Leon; McKillop, Sean; Reeves, Kathy K.; Saar, Steven; Testa, Paola; Tian, Hui; Jaeggli, Sarah; Kankelborg, Charles Bibcode: 2015ApJ...803...44M Altcode: 2015arXiv150203490M The Interface Region Imaging Spectrograph (IRIS) reveals small-scale rapid brightenings in the form of bright grains all over coronal holes and the quiet Sun. These bright grains are seen with the IRIS 1330, 1400, and 2796 Å slit-jaw filters. We combine coordinated observations with IRIS and from the ground with the Swedish 1 m Solar Telescope (SST) which allows us to have chromospheric (Ca ii 8542 Å, Ca ii H 3968 Å, Hα, and Mg ii k 2796 Å) and transition region (C ii 1334 Å, Si iv 1403 Å) spectral imaging, and single-wavelength Stokes maps in Fe i 6302 Å at high spatial (0\buildrel{\prime\prime}\over{.} 33), temporal, and spectral resolution. We conclude that the IRIS slit-jaw grains are the counterpart of so-called acoustic grains, i.e., resulting from chromospheric acoustic waves in a non-magnetic environment. We compare slit-jaw images (SJIs) with spectra from the IRIS spectrograph. We conclude that the grain intensity in the 2796 Å slit-jaw filter comes from both the Mg ii k core and wings. The signal in the C ii and Si iv lines is too weak to explain the presence of grains in the 1300 and 1400 Å SJIs and we conclude that the grain signal in these passbands comes mostly from the continuum. Although weak, the characteristic shock signatures of acoustic grains can often be detected in IRIS C ii spectra. For some grains, a spectral signature can be found in IRIS Si iv. This suggests that upward propagating acoustic waves sometimes reach all the way up to the transition region. Title: Homologous Helical Jets: Observations By IRIS, SDO, and Hinode and Magnetic Modeling With Data-Driven Simulations Authors: Cheung, Mark C. M.; De Pontieu, B.; Tarbell, T. D.; Fu, Y.; Tian, H.; Testa, P.; Reeves, K. K.; Martínez-Sykora, J.; Boerner, P.; Wülser, J. P.; Lemen, J.; Title, A. M.; Hurlburt, N.; Kleint, L.; Kankelborg, C.; Jaeggli, S.; Golub, L.; McKillop, S.; Saar, S.; Carlsson, M.; Hansteen, V. Bibcode: 2015ApJ...801...83C Altcode: 2015arXiv150101593C We report on observations of recurrent jets by instruments on board the Interface Region Imaging Spectrograph, Solar Dynamics Observatory (SDO), and Hinode spacecraft. Over a 4 hr period on 2013 July 21, recurrent coronal jets were observed to emanate from NOAA Active Region 11793. Far-ultraviolet spectra probing plasma at transition region temperatures show evidence of oppositely directed flows with components reaching Doppler velocities of ±100 km s-1. Raster Doppler maps using a Si iv transition region line show all four jets to have helical motion of the same sense. Simultaneous observations of the region by SDO and Hinode show that the jets emanate from a source region comprising a pore embedded in the interior of a supergranule. The parasitic pore has opposite polarity flux compared to the surrounding network field. This leads to a spine-fan magnetic topology in the coronal field that is amenable to jet formation. Time-dependent data-driven simulations are used to investigate the underlying drivers for the jets. These numerical experiments show that the emergence of current-carrying magnetic field in the vicinity of the pore supplies the magnetic twist needed for recurrent helical jet formation. Title: Total mass of six quiescent prominences estimated from their multi-spectral observations Authors: Schwartz, P.; Heinzel, P.; Kotrč, P.; Fárník, F.; Kupryakov, Yu. A.; DeLuca, E. E.; Golub, L. Bibcode: 2015A&A...574A..62S Altcode: Context. Total masses of six solar prominences were estimated using prominence multi-spectral observations (in EUV, X-rays, Hα, and Ca ii H). The observations were made during the observing campaign from April through June 2011.
Aims: The aim of the work was to apply a complex method for the prominence mass estimations that can be used later for other prominences observed during the observing campaign.
Methods: Our method is based on the fact that intensity of the EUV solar corona at wavelengths below 912 Å is reduced by the absorption in resonance continua of hydrogen and helium (photoionisation) and at the same time also by a deficit of the coronal emissivity in volume occupied by the cool prominence plasma. Both mechanisms contribute to intensity decrease simultaneously. The observations in X-rays allow us to separate these mechanisms from each other. Coronal emission behind a prominence is not estimated by any temporal or spatial interpolation, but by using a new method based on comparing the ratio of the optical thickness at 193 Å and 211 Å determined from the observations with the theoretical ratio.
Results: Values of the total mass estimated for six prominences are between 2.9 × 1011 and 1.7 × 1012 kg. The column density of hydrogen is of the order of 1018-1019 cm-2. Our results agree with results of other authors.
Conclusions: The method is now ready to be used for all 30 prominences observed during the campaign. Then in the near future it will be possible to obtain a statistics of the total mass of quiescent solar prominences. Title: Filling the Gap: Viewing the Corona from the Disk to the Source Surface Authors: Golub, L. Bibcode: 2014AGUFMSH52B..05G Altcode: Only recently has it become clear that the solar corona viewed in the EUV is detected out to far greater distances above the limb than had been expected (Seaton etal 2013). The reasons for the visibility of streamers out to >2 R_sol are unclear (Goaryaev etal 2014), but the fact that such structures can be seen is indisputable (Masson etal 2014). The EUV imaging instruments that have been used for these observations, such as TRACE, SWAP, STEREO and AIA, were not specifically designed to detect the extended corona, and such detection typically requires multiple exposures and mosaics. An instrument designed to obtain views of the extended EUV corona out to the nominal source surface with high efficiency is straightforward to build, and would provide 100X to 1000X higher sensitivity than current instruments. The main advantages of such EUV observations are: 1. the coronal dynamics and eruptions (such as CMEs) and the locations and effects of nearby streamers are visible from the start of the event on-disk; 2. the initial conditions of an event, including initial acceleration, changes of path due to interaction with nearby coronal structures, and propagation of coronal waves from the eruption site, are all directly seen; 3. the evolution of the eruption from the solar surface out to the inner edge of a white-light coronagraph can be seen, thus filling the gap in such WL images (Byrne etal 2014). We will present a class of simple EUV wide-field imager designs for implementation on a low-cost platform. Operation in the EUV implies that Sun-centered pointing tolerances can be relaxed, dust and scattering are negligible issues, and simple optics will fulfill all requirements. Implementation on a Sun-pointed spinning spacecraft is possible without great difficulty. Title: Toward the Direct Measurement of Coronal Magnetic Fields: An Airborne Infrared Spectrometer for Eclipse Observations Authors: Samra, J.; DeLuca, E. E.; Golub, L.; Cheimets, P. Bibcode: 2014AGUFMSH53B4214S Altcode: The solar magnetic field enables the heating of the corona and provides its underlying structure. Energy stored in coronal magnetic fields is released in flares and coronal mass ejections (CME) and provides the ultimate source of energy for space weather. Therefore, direct measurements of the coronal magnetic field have significant potential to enhance understanding of coronal dynamics and improve solar forecasting models. Of particular interest are observations of coronal field lines in the transitional region between closed and open flux systems, providing important information on the origin of the slow solar wind. While current instruments routinely observe only the photospheric and chromospheric magnetic fields, a proposed airborne spectrometer will take a step toward the direct observation of coronal fields by measuring plasma emission in the infrared at high spatial and spectral resolution. The targeted lines are four forbidden magnetic dipole transitions between 2 and 4 μm. The airborne system will consist of a telescope, grating spectrometer, and pointing/stabilization system to be flown on the NSF/NCAR High-performance Instrumented Airborne Platform for Environmental Research (HIAPER) during the August 2017 total solar eclipse. The project incorporates several optical engineering challenges, centered around maintaining adequate spectral and spatial resolution in a compact and inexpensive package and on a moving platform. Design studies are currently underway to examine the tradeoffs between various optical geometries and control strategies for the pointing/stabilization system. The results will be presented and interpreted in terms of the consequences for the scientific questions. In addition, results from a laboratory prototype and simulations of the final system will be presented. Title: The High-Resolution Coronal Imager (Hi-C) Authors: Kobayashi, Ken; Cirtain, Jonathan; Winebarger, Amy R.; Korreck, Kelly; Golub, Leon; Walsh, Robert W.; De Pontieu, Bart; DeForest, Craig; Title, Alan; Kuzin, Sergey; Savage, Sabrina; Beabout, Dyana; Beabout, Brent; Podgorski, William; Caldwell, David; McCracken, Kenneth; Ordway, Mark; Bergner, Henry; Gates, Richard; McKillop, Sean; Cheimets, Peter; Platt, Simon; Mitchell, Nick; Windt, David Bibcode: 2014SoPh..289.4393K Altcode: 2014SoPh..tmp..104K The High-Resolution Coronal Imager (Hi-C) was flown on a NASA sounding rocket on 11 July 2012. The goal of the Hi-C mission was to obtain high-resolution (≈ 0.3 - 0.4''), high-cadence (≈ 5 seconds) images of a solar active region to investigate the dynamics of solar coronal structures at small spatial scales. The instrument consists of a normal-incidence telescope with the optics coated with multilayers to reflect a narrow wavelength range around 19.3 nm (including the Fe XII 19.5-nm spectral line) and a 4096×4096 camera with a plate scale of 0.1'' pixel−1. The target of the Hi-C rocket flight was Active Region 11520. Hi-C obtained 37 full-frame images and 86 partial-frame images during the rocket flight. Analysis of the Hi-C data indicates the corona is structured on scales smaller than currently resolved by existing satellite missions. Title: High-resolution Laboratory Spectra of the λ193 Channel of the Atmospheric Imaging Assembly Instrument on Board Solar Dynamics Observatory Authors: Träbert, Elmar; Beiersdorfer, Peter; Brickhouse, Nancy S.; Golub, Leon Bibcode: 2014ApJS..215....6T Altcode: Extreme ultraviolet spectra of C, O, F, Ne, S, Ar, Fe, and Ni have been excited in an electron beam ion trap and studied with much higher resolution than available on the Solar Dynamics Observatory (SDO) in order to ascertain the spectral composition of the SDO/Atmospheric Imaging Assembly (AIA) observations. We present our findings in the wavelength range 182-200 Å, which, overall, corroborate the working models of how to interpret the SDO/AIA data. We find, however, that the inclusion of a number of additional lines might improve the data interpretation. Title: Hot explosions in the cool atmosphere of the Sun Authors: Peter, H.; Tian, H.; Curdt, W.; Schmit, D.; Innes, D.; De Pontieu, B.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser, J. P.; Martínez-Sykora, Juan; Kleint, L.; Golub, L.; McKillop, S.; Reeves, K. K.; Saar, S.; Testa, P.; Kankelborg, C.; Jaeggli, S.; Carlsson, M.; Hansteen, V. Bibcode: 2014Sci...346C.315P Altcode: 2014arXiv1410.5842P The solar atmosphere was traditionally represented with a simple one-dimensional model. Over the past few decades, this paradigm shifted for the chromosphere and corona that constitute the outer atmosphere, which is now considered a dynamic structured envelope. Recent observations by the Interface Region Imaging Spectrograph (IRIS) reveal that it is difficult to determine what is up and down, even in the cool 6000-kelvin photosphere just above the solar surface: This region hosts pockets of hot plasma transiently heated to almost 100,000 kelvin. The energy to heat and accelerate the plasma requires a considerable fraction of the energy from flares, the largest solar disruptions. These IRIS observations not only confirm that the photosphere is more complex than conventionally thought, but also provide insight into the energy conversion in the process of magnetic reconnection. Title: The unresolved fine structure resolved: IRIS observations of the solar transition region Authors: Hansteen, V.; De Pontieu, B.; Carlsson, M.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser, J. P.; Pereira, T. M. D.; De Luca, E. E.; Golub, L.; McKillop, S.; Reeves, K.; Saar, S.; Testa, P.; Tian, H.; Kankelborg, C.; Jaeggli, S.; Kleint, L.; Martínez-Sykora, J. Bibcode: 2014Sci...346E.315H Altcode: 2014arXiv1412.3611H The heating of the outer solar atmospheric layers, i.e., the transition region and corona, to high temperatures is a long-standing problem in solar (and stellar) physics. Solutions have been hampered by an incomplete understanding of the magnetically controlled structure of these regions. The high spatial and temporal resolution observations with the Interface Region Imaging Spectrograph (IRIS) at the solar limb reveal a plethora of short, low-lying loops or loop segments at transition-region temperatures that vary rapidly, on the time scales of minutes. We argue that the existence of these loops solves a long-standing observational mystery. At the same time, based on comparison with numerical models, this detection sheds light on a critical piece of the coronal heating puzzle. Title: Evidence of nonthermal particles in coronal loops heated impulsively by nanoflares Authors: Testa, P.; De Pontieu, B.; Allred, J.; Carlsson, M.; Reale, F.; Daw, A.; Hansteen, V.; Martinez-Sykora, J.; Liu, W.; DeLuca, E. E.; Golub, L.; McKillop, S.; Reeves, K.; Saar, S.; Tian, H.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser, J. P.; Kleint, L.; Kankelborg, C.; Jaeggli, S. Bibcode: 2014Sci...346B.315T Altcode: 2014arXiv1410.6130T The physical processes causing energy exchange between the Sun’s hot corona and its cool lower atmosphere remain poorly understood. The chromosphere and transition region (TR) form an interface region between the surface and the corona that is highly sensitive to the coronal heating mechanism. High-resolution observations with the Interface Region Imaging Spectrograph (IRIS) reveal rapid variability (~20 to 60 seconds) of intensity and velocity on small spatial scales (≲500 kilometers) at the footpoints of hot and dynamic coronal loops. The observations are consistent with numerical simulations of heating by beams of nonthermal electrons, which are generated in small impulsive (≲30 seconds) heating events called “coronal nanoflares.” The accelerated electrons deposit a sizable fraction of their energy (≲1025 erg) in the chromosphere and TR. Our analysis provides tight constraints on the properties of such electron beams and new diagnostics for their presence in the nonflaring corona. Title: Prevalence of small-scale jets from the networks of the solar transition region and chromosphere Authors: Tian, H.; DeLuca, E. E.; Cranmer, S. R.; De Pontieu, B.; Peter, H.; Martínez-Sykora, J.; Golub, L.; McKillop, S.; Reeves, K. K.; Miralles, M. P.; McCauley, P.; Saar, S.; Testa, P.; Weber, M.; Murphy, N.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser, J. P.; Kleint, L.; Kankelborg, C.; Jaeggli, S.; Carlsson, M.; Hansteen, V.; McIntosh, S. W. Bibcode: 2014Sci...346A.315T Altcode: 2014arXiv1410.6143T As the interface between the Sun’s photosphere and corona, the chromosphere and transition region play a key role in the formation and acceleration of the solar wind. Observations from the Interface Region Imaging Spectrograph reveal the prevalence of intermittent small-scale jets with speeds of 80 to 250 kilometers per second from the narrow bright network lanes of this interface region. These jets have lifetimes of 20 to 80 seconds and widths of ≤300 kilometers. They originate from small-scale bright regions, often preceded by footpoint brightenings and accompanied by transverse waves with amplitudes of ~20 kilometers per second. Many jets reach temperatures of at least ~105 kelvin and constitute an important element of the transition region structures. They are likely an intermittent but persistent source of mass and energy for the solar wind. Title: On the prevalence of small-scale twist in the solar chromosphere and transition region Authors: De Pontieu, B.; Rouppe van der Voort, L.; McIntosh, S. W.; Pereira, T. M. D.; Carlsson, M.; Hansteen, V.; Skogsrud, H.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser, J. P.; De Luca, E. E.; Golub, L.; McKillop, S.; Reeves, K.; Saar, S.; Testa, P.; Tian, H.; Kankelborg, C.; Jaeggli, S.; Kleint, L.; Martinez-Sykora, J. Bibcode: 2014Sci...346D.315D Altcode: 2014arXiv1410.6862D The solar chromosphere and transition region (TR) form an interface between the Sun’s surface and its hot outer atmosphere. There, most of the nonthermal energy that powers the solar atmosphere is transformed into heat, although the detailed mechanism remains elusive. High-resolution (0.33-arc second) observations with NASA’s Interface Region Imaging Spectrograph (IRIS) reveal a chromosphere and TR that are replete with twist or torsional motions on sub-arc second scales, occurring in active regions, quiet Sun regions, and coronal holes alike. We coordinated observations with the Swedish 1-meter Solar Telescope (SST) to quantify these twisting motions and their association with rapid heating to at least TR temperatures. This view of the interface region provides insight into what heats the low solar atmosphere. Title: Open questions on prominences from coordinated observations by IRIS, Hinode, SDO/AIA, THEMIS, and the Meudon/MSDP Authors: Schmieder, B.; Tian, H.; Kucera, T.; López Ariste, A.; Mein, N.; Mein, P.; Dalmasse, K.; Golub, L. Bibcode: 2014A&A...569A..85S Altcode: 2014arXiv1407.3171S Context. A large prominence was observed by multiple instruments on the ground and in space during an international campaign on September 24, 2013, for three hours (12:12 UT -15:12 UT). Instruments used in the campaign included the newly launched (June 2013) Interface Region Imaging Spectrograph (IRIS), THEMIS (Tenerife), the Hinode Solar Optical Telescope (SOT), the Solar Dynamic Observatory's Atmospheric Imaging Assembly (SDO/AIA), and the Multichannel Subtractive Double Pass spectrograph (MSDP) in the Meudon Solar Tower. The movies obtained in 304 Å with the EUV imager SDO/AIA, and in Ca II line by SOT show the dynamic nature of the prominence.
Aims: The aim of this work is to study the dynamics of the prominence fine structures in multiple wavelengths to understand their formation.
Methods: The spectrographs IRIS and MSDP provided line profiles with a high cadence in Mg II h (2803.5 Å) and k (2796.4 Å) lines along four slit positions (IRIS), and in Hα in a 2D field of view (MSDP). The spectropolarimetry of THEMIS (Tenerife) allowed us to derive the magnetic field of the prominence using the He D3 line depolarization (Hanle effect combined with the Zeeman effect).
Results: The magnetic field is found to be globally horizontal with a relatively weak field strength (8-15 Gauss). On the other hand, the Ca II movie reveals turbulent-like motion that is not organized in specific parts of the prominence. We tested the addition of a turbulent magnetic component. This model is compatible with the polarimetric observations at those places where the plasma turbulence peaks. On the other hand, the Mg II line profiles show multiple peaks well separated in wavelength. This is interpreted by the existence of small threads along the line of sight with a large dispersion of discrete values of Doppler shifts, from 5 km s-1 (a quasi-steady component) to 60-80 km s-1. Each peak corresponds to a Gaussian profile, and not to a reversed profile as was expected by the present non-LTE radiative transfer modeling. This is a very surprising behavior for the Mg II line observed in prominences.
Conclusions: Turbulent fields on top of the macroscopic horizontal component of the magnetic field supporting the prominence give rise to the complex dynamics of the plasma. The plasma with the high velocities (70 km s-1 to 100 km s-1 if we take into account the transverse velocities) may correspond to condensation of plasma along more or less horizontal threads of the arch-shape structure visible in 304 Å. The steady flows (5 km s-1) would correspond to a more quiescent plasma (cool and prominence-corona transition region) of the prominence packed into dips in horizontal magnetic field lines. The very weak secondary peaks in the Mg II profiles may reflect the turbulent nature of parts of the prominence.

Movies are available in electronic form at http://www.aanda.org Title: An Interface Region Imaging Spectrograph First View on Solar Spicules Authors: Pereira, T. M. D.; De Pontieu, B.; Carlsson, M.; Hansteen, V.; Tarbell, T. D.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt, N.; Wülser, J. P.; Martínez-Sykora, J.; Kleint, L.; Golub, L.; McKillop, S.; Reeves, K. K.; Saar, S.; Testa, P.; Tian, H.; Jaeggli, S.; Kankelborg, C. Bibcode: 2014ApJ...792L..15P Altcode: 2014arXiv1407.6360P Solar spicules have eluded modelers and observers for decades. Since the discovery of the more energetic type II, spicules have become a heated topic but their contribution to the energy balance of the low solar atmosphere remains unknown. Here we give a first glimpse of what quiet-Sun spicules look like when observed with NASA's recently launched Interface Region Imaging Spectrograph (IRIS). Using IRIS spectra and filtergrams that sample the chromosphere and transition region, we compare the properties and evolution of spicules as observed in a coordinated campaign with Hinode and the Atmospheric Imaging Assembly. Our IRIS observations allow us to follow the thermal evolution of type II spicules and finally confirm that the fading of Ca II H spicules appears to be caused by rapid heating to higher temperatures. The IRIS spicules do not fade but continue evolving, reaching higher and falling back down after 500-800 s. Ca II H type II spicules are thus the initial stages of violent and hotter events that mostly remain invisible in Ca II H filtergrams. These events have very different properties from type I spicules, which show lower velocities and no fading from chromospheric passbands. The IRIS spectra of spicules show the same signature as their proposed disk counterparts, reinforcing earlier work. Spectroheliograms from spectral rasters also confirm that quiet-Sun spicules originate in bushes from the magnetic network. Our results suggest that type II spicules are indeed the site of vigorous heating (to at least transition region temperatures) along extensive parts of the upward moving spicular plasma. Title: Observations of Subarcsecond Bright Dots in the Transition Region above Sunspots with the Interface Region Imaging Spectrograph Authors: Tian, H.; Kleint, L.; Peter, H.; Weber, M.; Testa, P.; DeLuca, E.; Golub, L.; Schanche, N. Bibcode: 2014ApJ...790L..29T Altcode: 2014arXiv1407.1060T Observations with the Interface Region Imaging Spectrograph (IRIS) have revealed numerous sub-arcsecond bright dots in the transition region above sunspots. These bright dots are seen in the 1400 Å and 1330 Å slit-jaw images. They are clearly present in all sunspots we investigated, mostly in the penumbrae, but also occasionally in some umbrae and light bridges. The bright dots in the penumbrae typically appear slightly elongated, with the two dimensions being 300-600 km and 250-450 km, respectively. The long sides of these dots are often nearly parallel to the bright filamentary structures in the penumbrae but sometimes clearly deviate from the radial direction. Their lifetimes are mostly less than one minute, although some dots last for a few minutes or even longer. Their intensities are often a few times stronger than the intensities of the surrounding environment in the slit-jaw images. About half of the bright dots show apparent movement with speeds of ~10-40 km s-1 in the radial direction. Spectra of a few bright dots were obtained and the Si IV 1402.77 Å line profiles in these dots are significantly broadened. The line intensity can be enhanced by one to two orders of magnitude. Some relatively bright and long-lasting dots are also observed in several passbands of the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory, and they appear to be located at the bases of loop-like structures. Many of these bright dots are likely associated with small-scale energy release events at the transition region footpoints of magnetic loops. Title: The Interface Region Imaging Spectrograph (IRIS) Authors: De Pontieu, B.; Title, A. M.; Lemen, J. R.; Kushner, G. D.; Akin, D. J.; Allard, B.; Berger, T.; Boerner, P.; Cheung, M.; Chou, C.; Drake, J. F.; Duncan, D. W.; Freeland, S.; Heyman, G. F.; Hoffman, C.; Hurlburt, N. E.; Lindgren, R. W.; Mathur, D.; Rehse, R.; Sabolish, D.; Seguin, R.; Schrijver, C. J.; Tarbell, T. D.; Wülser, J. -P.; Wolfson, C. J.; Yanari, C.; Mudge, J.; Nguyen-Phuc, N.; Timmons, R.; van Bezooijen, R.; Weingrod, I.; Brookner, R.; Butcher, G.; Dougherty, B.; Eder, J.; Knagenhjelm, V.; Larsen, S.; Mansir, D.; Phan, L.; Boyle, P.; Cheimets, P. N.; DeLuca, E. E.; Golub, L.; Gates, R.; Hertz, E.; McKillop, S.; Park, S.; Perry, T.; Podgorski, W. A.; Reeves, K.; Saar, S.; Testa, P.; Tian, H.; Weber, M.; Dunn, C.; Eccles, S.; Jaeggli, S. A.; Kankelborg, C. C.; Mashburn, K.; Pust, N.; Springer, L.; Carvalho, R.; Kleint, L.; Marmie, J.; Mazmanian, E.; Pereira, T. M. D.; Sawyer, S.; Strong, J.; Worden, S. P.; Carlsson, M.; Hansteen, V. H.; Leenaarts, J.; Wiesmann, M.; Aloise, J.; Chu, K. -C.; Bush, R. I.; Scherrer, P. H.; Brekke, P.; Martinez-Sykora, J.; Lites, B. W.; McIntosh, S. W.; Uitenbroek, H.; Okamoto, T. J.; Gummin, M. A.; Auker, G.; Jerram, P.; Pool, P.; Waltham, N. Bibcode: 2014SoPh..289.2733D Altcode: 2014arXiv1401.2491D; 2014SoPh..tmp...25D The Interface Region Imaging Spectrograph (IRIS) small explorer spacecraft provides simultaneous spectra and images of the photosphere, chromosphere, transition region, and corona with 0.33 - 0.4 arcsec spatial resolution, two-second temporal resolution, and 1 km s−1 velocity resolution over a field-of-view of up to 175 arcsec × 175 arcsec. IRIS was launched into a Sun-synchronous orbit on 27 June 2013 using a Pegasus-XL rocket and consists of a 19-cm UV telescope that feeds a slit-based dual-bandpass imaging spectrograph. IRIS obtains spectra in passbands from 1332 - 1358 Å, 1389 - 1407 Å, and 2783 - 2834 Å, including bright spectral lines formed in the chromosphere (Mg II h 2803 Å and Mg II k 2796 Å) and transition region (C II 1334/1335 Å and Si IV 1394/1403 Å). Slit-jaw images in four different passbands (C II 1330, Si IV 1400, Mg II k 2796, and Mg II wing 2830 Å) can be taken simultaneously with spectral rasters that sample regions up to 130 arcsec × 175 arcsec at a variety of spatial samplings (from 0.33 arcsec and up). IRIS is sensitive to emission from plasma at temperatures between 5000 K and 10 MK and will advance our understanding of the flow of mass and energy through an interface region, formed by the chromosphere and transition region, between the photosphere and corona. This highly structured and dynamic region not only acts as the conduit of all mass and energy feeding into the corona and solar wind, it also requires an order of magnitude more energy to heat than the corona and solar wind combined. The IRIS investigation includes a strong numerical modeling component based on advanced radiative-MHD codes to facilitate interpretation of observations of this complex region. Approximately eight Gbytes of data (after compression) are acquired by IRIS each day and made available for unrestricted use within a few days of the observation. Title: Detection of Supersonic Downflows and Associated Heating Events in the Transition Region above Sunspots Authors: Kleint, L.; Antolin, P.; Tian, H.; Judge, P.; Testa, P.; De Pontieu, B.; Martínez-Sykora, J.; Reeves, K. K.; Wuelser, J. P.; McKillop, S.; Saar, S.; Carlsson, M.; Boerner, P.; Hurlburt, N.; Lemen, J.; Tarbell, T. D.; Title, A.; Golub, L.; Hansteen, V.; Jaeggli, S.; Kankelborg, C. Bibcode: 2014ApJ...789L..42K Altcode: 2014arXiv1406.6816K Interface Region Imaging Spectrograph data allow us to study the solar transition region (TR) with an unprecedented spatial resolution of 0.''33. On 2013 August 30, we observed bursts of high Doppler shifts suggesting strong supersonic downflows of up to 200 km s-1 and weaker, slightly slower upflows in the spectral lines Mg II h and k, C II 1336, Si IV 1394 Å, and 1403 Å, that are correlated with brightenings in the slitjaw images (SJIs). The bursty behavior lasts throughout the 2 hr observation, with average burst durations of about 20 s. The locations of these short-lived events appear to be the umbral and penumbral footpoints of EUV loops. Fast apparent downflows are observed along these loops in the SJIs and in the Atmospheric Imaging Assembly, suggesting that the loops are thermally unstable. We interpret the observations as cool material falling from coronal heights, and especially coronal rain produced along the thermally unstable loops, which leads to an increase of intensity at the loop footpoints, probably indicating an increase of density and temperature in the TR. The rain speeds are on the higher end of previously reported speeds for this phenomenon, and possibly higher than the free-fall velocity along the loops. On other observing days, similar bright dots are sometimes aligned into ribbons, resembling small flare ribbons. These observations provide a first insight into small-scale heating events in sunspots in the TR. Title: Dynamics of the Transition Corona Authors: Masson, Sophie; McCauley, Patrick; Golub, Leon; Reeves, Katharine K.; DeLuca, Edward E. Bibcode: 2014ApJ...787..145M Altcode: 2013arXiv1301.0740M Magnetic reconnection between the open and closed magnetic fields in the corona is believed to play a crucial role in the corona/heliosphere coupling. At large scale, the exchange of open/closed connectivity is expected to occur in pseudo-streamer (PS) structures. However, there is neither clear observational evidence of how such coupling occurs in PSs, nor evidence for how the magnetic reconnection evolves. Using a newly developed technique, we enhance the off-limb magnetic fine structures observed with the Atmospheric Imaging Assembly and identify a PS-like feature located close to the northern coronal hole. We first identify that the magnetic topology associated with the observation is a PS, null-point (NP) related topology bounded by the open field. By comparing the magnetic field configuration with the EUV emission regions, we determined that most of the magnetic flux associated with plasma emission are small loops below the PS basic NP and open field bounding the PS topology. In order to interpret the evolution of the PS, we referred to a three-dimensional MHD interchange reconnection modeling the exchange of connectivity between small closed loops and the open field. The observed PS fine structures follow the dynamics of the magnetic field before and after reconnecting at the NP obtained by the interchange model. Moreover, the pattern of the EUV plasma emission is the same as the shape of the expected plasma emission location derived from the simulation. These morphological and dynamical similarities between the PS observations and the results from the simulation strongly suggest that the evolution of the PS, and in particular the opening/closing of the field, occurs via interchange/slipping reconnection at the basic NP of the PS. Besides identifying the mechanism at work in the large-scale coupling between the open and closed fields, our results highlight that interchange reconnection in PSs is a gradual physical process that differs from the impulsive reconnection of the solar-jet model. Title: The Substructure of the Solar Corona Observed in the Hi-C Telescope Authors: Winebarger, Amy R.; Cirtain, Jonathan W.; Golub, Leon; DeLuca, Ed; Savage, Sabrina; Alexander, Caroline; Schuler, Timothy Bibcode: 2014AAS...22432320W Altcode: In the summer of 2012, the High-resolution Coronal Imager (Hi-C) flew aboard a NASA sounding rocket and collected the highest spatial resolution images ever obtained of the solar corona. One of the goals of the Hi-C flight was to characterize the substructure of the solar corona. We therefore calculate how the intensity scales from a low-resolution (AIA) pixels to high-resolution (Hi-C) pixels for both the dynamic events and “background” emission (meaning, the steady emission over the 5 minutes of data acquisition time). We find there is no evidence of substructure in the background corona; the intensity scales smoothly from low-resolution to high-resolution Hi-C pixels. In transient events, however, the intensity observed with Hi-C is, on average, 2.6 times larger than observed with AIA. This increase in intensity suggests that AIA is not resolving these events. This result suggests a finely structured dynamic corona embedded in a smoothly varying background. Title: Visibility of Extended Coronal Structures and CMEs in the EUV Authors: Schanche, Nicole; Golub, Leon Bibcode: 2014AAS...22432347S Altcode: Extended coronal structures around active regions and coronal mass ejections (CMEs) have often been seen in the extreme-ultraviolet (EUV) channels to the full extent of the AIA and SWAP field of views 1.3 and 1.7 Rsun). Using off-pointed comet data in AIA we sum a large number of frames to evaluate the off-limb distance to which streamers can be detected. For CMEs, we compared the events classified as halo CMEs in the white-light LASCO CACTus catalog from July-September 2013 to the AIA and SWAP data collected around those events. We discovered that roughly 80% of events could be seen in the EUV using both regular and running difference movies, with the most effective channels being the 193 and 304Å channels. By projecting out the signal strength of several of these events, we conclude that these EUV events can in many cases be detected to over 2.5 Rsun. A larger field-of-view telescope would make it possible to track the development of these structures and events from the disk out to several solar radii, complementing the traditional white-light methods. Title: An Airborne Infrared Telescope and Spectrograph for Solar Eclipse Observations Authors: DeLuca, Edward E.; Cheimets, Peter; Golub, Leon Bibcode: 2014AAS...22412356D Altcode: The solar infrared spectrum offers great possibilities for direct spatially resolved measurements of the solar coronal magnetic fields, via imaging of the plasma that is constrained to follow the magnetic field direction and via spectro-polarimetry that permits measurement of the field strength in the corona. Energy stored in coronal magnetic fields is released in flares and coronal mass ejections (CME) and provides the ultimate source of energy for space weather. The large scale structure of the coronal field, and the opening up of the field in a transition zone between the closed and open corona determines the speed and structure of the solar wind, providing the background environment through which CMEs propagate. At present our only direct measurements of the solar magnetic fields are in the photosphere and chromosphere. The ability to determine where and why the corona transitions from closed to open, combined with measurements of the field strength via infrared coronal spectro-polarimetry will give us a powerful new tool in our quest to develop the next generation of forecasting models.We describe a first step in achieving this goal: a proposal for a new IR telescope, image stabilization system, and spectrometer, for the NCAR HIPER GV aircraft. The telescope/spectrograph will operate in the 2-6micron wavelength region, during solar eclipses, starting with the trans-north American eclipse in August 2017. The HIAPER aircraft flying at ~35,000 ft will provide an excellent platform for IR observations. Our imaging and spectroscopy experiment will show the distribution and intensity of IR forbidden lines in the solar corona. Title: High-resolution Laboratory Measurements of Coronal Lines in the 198-218 Å Region Authors: Beiersdorfer, Peter; Träbert, Elmar; Lepson, Jaan K.; Brickhouse, Nancy S.; Golub, Leon Bibcode: 2014ApJ...788...25B Altcode: We present high-resolution laboratory measurements of the emission from various ions of C, N, O, F, Ne, S, Ar, Fe, and Ni in the extreme ultraviolet wavelength band centered around the λ211 Fe XIV channel of the Atmospheric Imaging Assembly on the Solar Dynamics Observatory. While all of the strong iron lines in this region are well known, we note many weaker lines of iron that are not yet identified. The high resolution of our measurements also allows us to resolve several lines in Fe XI, Fe XII, and Fe XIII between 200 and 205 Å, whose identities were in question based on a disagreement between different databases. The spectra of the elements other than iron are much less known, and we find a multitude of lines that are not yet in the databases. For example, the CHIANTI database clearly disagrees with the NIST data listings on several of the argon lines we observe and also it contains only about half of the observed sulfur lines. Title: Discovery of Finely Structured Dynamic Solar Corona Observed in the Hi-C Telescope Authors: Winebarger, Amy R.; Cirtain, Jonathan; Golub, Leon; DeLuca, Edward; Savage, Sabrina; Alexander, Caroline; Schuler, Timothy Bibcode: 2014ApJ...787L..10W Altcode: In the Summer of 2012, the High-resolution Coronal Imager (Hi-C) flew on board a NASA sounding rocket and collected the highest spatial resolution images ever obtained of the solar corona. One of the goals of the Hi-C flight was to characterize the substructure of the solar corona. We therefore examine how the intensity scales from AIA resolution to Hi-C resolution. For each low-resolution pixel, we calculate the standard deviation in the contributing high-resolution pixel intensities and compare that to the expected standard deviation calculated from the noise. If these numbers are approximately equal, the corona can be assumed to be smoothly varying, i.e., have no evidence of substructure in the Hi-C image to within Hi-C's ability to measure it given its throughput and readout noise. A standard deviation much larger than the noise value indicates the presence of substructure. We calculate these values for each low-resolution pixel for each frame of the Hi-C data. On average, 70% of the pixels in each Hi-C image show no evidence of substructure. The locations where substructure is prevalent is in the moss regions and in regions of sheared magnetic field. We also find that the level of substructure varies significantly over the roughly 160 s of the Hi-C data analyzed here. This result indicates that the finely structured corona is concentrated in regions of heating and is highly time dependent. Title: High-resolution Observations of the Shock Wave Behavior for Sunspot Oscillations with the Interface Region Imaging Spectrograph Authors: Tian, H.; DeLuca, E.; Reeves, K. K.; McKillop, S.; De Pontieu, B.; Martínez-Sykora, J.; Carlsson, M.; Hansteen, V.; Kleint, L.; Cheung, M.; Golub, L.; Saar, S.; Testa, P.; Weber, M.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser, J. P.; Kankelborg, C.; Jaeggli, S.; McIntosh, S. W. Bibcode: 2014ApJ...786..137T Altcode: 2014arXiv1404.6291T We present the first results of sunspot oscillations from observations by the Interface Region Imaging Spectrograph. The strongly nonlinear oscillation is identified in both the slit-jaw images and the spectra of several emission lines formed in the transition region and chromosphere. We first apply a single Gaussian fit to the profiles of the Mg II 2796.35 Å, C II 1335.71 Å, and Si IV 1393.76 Å lines in the sunspot. The intensity change is ~30%. The Doppler shift oscillation reveals a sawtooth pattern with an amplitude of ~10 km s-1 in Si IV. The Si IV oscillation lags those of C II and Mg II by ~3 and ~12 s, respectively. The line width suddenly increases as the Doppler shift changes from redshift to blueshift. However, we demonstrate that this increase is caused by the superposition of two emission components. We then perform detailed analysis of the line profiles at a few selected locations on the slit. The temporal evolution of the line core is dominated by the following behavior: a rapid excursion to the blue side, accompanied by an intensity increase, followed by a linear decrease of the velocity to the red side. The maximum intensity slightly lags the maximum blueshift in Si IV, whereas the intensity enhancement slightly precedes the maximum blueshift in Mg II. We find a positive correlation between the maximum velocity and deceleration, a result that is consistent with numerical simulations of upward propagating magnetoacoustic shock waves. Title: Sparkling Extreme-ultraviolet Bright Dots Observed with Hi-C Authors: Régnier, S.; Alexander, C. E.; Walsh, R. W.; Winebarger, A. R.; Cirtain, J.; Golub, L.; Korreck, K. E.; Mitchell, N.; Platt, S.; Weber, M.; De Pontieu, B.; Title, A.; Kobayashi, K.; Kuzin, S.; DeForest, C. E. Bibcode: 2014ApJ...784..134R Altcode: 2014arXiv1402.2457R Observing the Sun at high time and spatial scales is a step toward understanding the finest and fundamental scales of heating events in the solar corona. The high-resolution coronal (Hi-C) instrument has provided the highest spatial and temporal resolution images of the solar corona in the EUV wavelength range to date. Hi-C observed an active region on 2012 July 11 that exhibits several interesting features in the EUV line at 193 Å. One of them is the existence of short, small brightenings "sparkling" at the edge of the active region; we call these EUV bright dots (EBDs). Individual EBDs have a characteristic duration of 25 s with a characteristic length of 680 km. These brightenings are not fully resolved by the SDO/AIA instrument at the same wavelength; however, they can be identified with respect to the Hi-C location of the EBDs. In addition, EBDs are seen in other chromospheric/coronal channels of SDO/AIA, which suggests a temperature between 0.5 and 1.5 MK. Based on their frequency in the Hi-C time series, we define four different categories of EBDs: single peak, double peak, long duration, and bursty. Based on a potential field extrapolation from an SDO/HMI magnetogram, the EBDs appear at the footpoints of large-scale, trans-equatorial coronal loops. The Hi-C observations provide the first evidence of small-scale EUV heating events at the base of these coronal loops, which have a free magnetic energy of the order of 1026 erg. Title: Nearest Star Authors: Golub, Leon; Pasachoff, Jay M. Bibcode: 2014nest.book.....G Altcode: Preface; Acknowledgments; 1. The Sun; 2. The once and future Sun; 3. What we see: the solar disk; 4. What we don't see; 5. Eclipses; 6. Space missions; 7. Between fire and ice; 8. Space weather; Bibliography; Glossary; Index. Title: High-resolution Laboratory Spectra on the λ131 Channel of the AIA Instrument On Board the Solar Dynamics Observatory Authors: Träbert, Elmar; Beiersdorfer, Peter; Brickhouse, Nancy S.; Golub, Leon Bibcode: 2014ApJS..211...14T Altcode: Extreme ultraviolet spectra of C, O, F, Ne, Si, S, Ar, Ca, Fe, and Ni have been excited in an electron beam ion trap and studied with much higher resolution than available on Solar Dynamics Observatory (SDO) in order to ascertain the spectral composition of the SDO observations. We presently show our findings in the wavelength range 124-134 Å, which encompasses the λ131 observation channel of the Atmospheric Imaging Assembly (AIA). While the general interpretation of the spectral composition of the λ131 Fe channel is being corroborated, a number of new lines have been observed that might help to improve the diagnostic value of the SDO/AIA data. Title: Diagnostics for the O IV and Si IV lines observed by IRIS Authors: Dudik, Jaroslav; Mason, Helen; Del Zanna, Giulio; Golub, Leon; Dzifcakova, Elena Bibcode: 2014cosp...40E.754D Altcode: We investigate the formation of the IRIS O IV and Si IV lines under non-Maxwellian conditions characterized by kappa-distributions. It is found that the Si IV lines are always formed at lower temperatures than the O IV lines. However, as the departure from the Maxwellian increases, the peak formation temperatures are shifted progressively to lower and lower temperatures. Coupled with the slope of the differential emission measure (DEM), it is possible for the Si IV lines to be formed very close to the solar chromosphere, with the majority of the O IV intensities coming from a different, higher part of the transition region. The predicted spectra for kappa-distributions exhibit very low O IV intensities compared to Si IV, analogously to what is observed by the IRIS spacecraft. Potential density diagnostics are discussed, as well as the contribution of photoexcitation to the formation of these lines. Title: Observation of nano-flares and transient coronal heating Authors: Serge, Koutchmy; Golub, Leon; Bazin, Cyrille; Tavabi, Ehsan Bibcode: 2014cosp...40E2970S Altcode: Nano-flares are the best candidate for heating the bulk of the corona but their signature is still not clearly recognized in the data. The Hinode XRT provided many high resolution partial frame sequences that allowed study of intermittent flash events in quiet areas, suggesting a definite signature of nano-flares. The Yohkoh so-called SXR transient brightenings are now recorded by XRT with a wealth of detail. The typical resolution and low noise of XRT permits detection at a much lower intensity threshold and a much shorter duration. In order to evaluate what is a nano-flare, we selected a well-observed solar disk event seen at the beginning of the XRT mission, when the Sun was still very quiet. This single flare event is recorded outside of any active region and does not show any GOES or RHESSI signature, even at the lowest level. This nano-flare shows structures suggestive of rather horizontal low lying loops with a short intense flash phase. No jet is observed. EUV brightening counterparts exist, including the 304Å TR emission, detected by the SECCHI EUV imagers on the two STEREO spacecrafts. Filtergrams taken simultaneously at a fast rate in Hα are deeply processed to look at the resulting effects, seen as a faint brightening and a cool transient very small scale feature. We argue in favor of many similar SXR events permanently occurring at the TR levels, not showing strong EUV brightenings but with horizontally stretched structures similar to the recently described Hi-C reconnection events called magnetic “braids” that include twists and possibly counter flows. Title: Total mass loading of prominences estimated from their multi-spectral observations Authors: Schwartz, Pavol; Heinzel, Peter; Kotrč, Pavel; Fárník, František; Kupryakov, Yurij A.; DeLuca, Edward E.; Golub, Leon Bibcode: 2014IAUS..300..458S Altcode: The total mass of several quiescent prominences observed in EUV by the AIA instrument on board SDO, in soft X-rays by XRT on Hinode and in Hα and CaII H by the SLS and HSFA spectrographs of the Ondřejov observatory, was estimated. Values of asymmetry of coronal emissivity obtained during the mass computations are compared with those estimated from 193 Å intensities measured at the disk edge and just above the limb. Title: Solar Transition Region Lines Observed by the Interface Region Imaging Spectrograph: Diagnostics for the O IV and Si IV Lines Authors: Dudík, J.; Del Zanna, G.; Dzifčáková, E.; Mason, H. E.; Golub, L. Bibcode: 2014ApJ...780L..12D Altcode: 2013arXiv1311.6978D The formation of the transition region O IV and Si IV lines observable by the Interface Region Imaging Spectrograph (IRIS) is investigated for both Maxwellian and non-Maxwellian conditions characterized by a κ-distribution exhibiting a high-energy tail. The Si IV lines are formed at lower temperatures than the O IV lines for all κ. In non-Maxwellian situations with lower κ, the contribution functions are shifted to lower temperatures. Combined with the slope of the differential emission measure, it is possible for the Si IV lines to be formed at very different regions of the solar transition region than the O IV lines; possibly close to the solar chromosphere. Such situations might be discernible by IRIS. It is found that photoexcitation can be important for the Si IV lines, but is negligible for the O IV lines. The usefulness of the O IV ratios for density diagnostics independently of κ is investigated and it is found that the O IV 1404.78 Å/1399.77 Å ratio provides a good density diagnostics except for very low T combined with extreme non-Maxwellian situations. Title: Anti-parallel EUV Flows Observed along Active Region Filament Threads with Hi-C Authors: Alexander, Caroline E.; Walsh, Robert W.; Régnier, Stéphane; Cirtain, Jonathan; Winebarger, Amy R.; Golub, Leon; Kobayashi, Ken; Platt, Simon; Mitchell, Nick; Korreck, Kelly; DePontieu, Bart; DeForest, Craig; Weber, Mark; Title, Alan; Kuzin, Sergey Bibcode: 2013ApJ...775L..32A Altcode: 2013arXiv1306.5194A Plasma flows within prominences/filaments have been observed for many years and hold valuable clues concerning the mass and energy balance within these structures. Previous observations of these flows primarily come from Hα and cool extreme-ultraviolet (EUV) lines (e.g., 304 Å) where estimates of the size of the prominence threads has been limited by the resolution of the available instrumentation. Evidence of "counter-steaming" flows has previously been inferred from these cool plasma observations, but now, for the first time, these flows have been directly imaged along fundamental filament threads within the million degree corona (at 193 Å). In this work, we present observations of an AR filament observed with the High-resolution Coronal Imager (Hi-C) that exhibits anti-parallel flows along adjacent filament threads. Complementary data from the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) and Helioseismic and Magnetic Imager are presented. The ultra-high spatial and temporal resolution of Hi-C allow the anti-parallel flow velocities to be measured (70-80 km s-1) and gives an indication of the resolvable thickness of the individual strands (0.''8 ± 0.''1). The temperature of the plasma flows was estimated to be log T (K) = 5.45 ± 0.10 using Emission Measure loci analysis. We find that SDO/AIA cannot clearly observe these anti-parallel flows or measure their velocity or thread width due to its larger pixel size. We suggest that anti-parallel/counter-streaming flows are likely commonplace within all filaments and are currently not observed in EUV due to current instrument spatial resolution. Title: Structure of solar coronal loops: from miniature to large-scale Authors: Peter, H.; Bingert, S.; Klimchuk, J. A.; de Forest, C.; Cirtain, J. W.; Golub, L.; Winebarger, A. R.; Kobayashi, K.; Korreck, K. E. Bibcode: 2013A&A...556A.104P Altcode: 2013arXiv1306.4685P
Aims: We use new data from the High-resolution Coronal Imager (Hi-C) with its unprecedented spatial resolution of the solar corona to investigate the structure of coronal loops down to 0.2''.
Methods: During a rocket flight, Hi-C provided images of the solar corona in a wavelength band around 193 Å that is dominated by emission from Fe xii showing plasma at temperatures around 1.5 MK. We analyze part of the Hi-C field-of-view to study the smallest coronal loops observed so far and search for the possible substructuring of larger loops.
Results: We find tiny 1.5 MK loop-like structures that we interpret as miniature coronal loops. Their coronal segments above the chromosphere have a length of only about 1 Mm and a thickness of less than 200 km. They could be interpreted as the coronal signature of small flux tubes breaking through the photosphere with a footpoint distance corresponding to the diameter of a cell of granulation. We find that loops that are longer than 50 Mm have diameters of about 2'' or 1.5 Mm, which is consistent with previous observations. However, Hi-C really resolves these loops with some 20 pixels across the loop. Even at this greatly improved spatial resolution, the large loops seem to have no visible substructure. Instead they show a smooth variation in cross-section.
Conclusions: That the large coronal loops do not show a substructure on the spatial scale of 0.1'' per pixel implies that either the densities and temperatures are smoothly varying across these loops or it places an upper limit on the diameter of the strands the loops might be composed of. We estimate that strands that compose the 2'' thick loop would have to be thinner than 15 km. The miniature loops we find for the first time pose a challenge to be properly understood through modeling.

Appendices are available in electronic form at http://www.aanda.org Title: Evidence for the release of magnetic free energy using Hi-C observations Authors: Cirtain, Jonathan W.; Winebarger, A. R.; Golub, L.; Korreck, K. E.; Kobayashi, K. Bibcode: 2013SPD....4420001C Altcode: The Hi-C sounding rocket data can be used to determine the rate and approximate magnitude of free energy released by the active region coronal magnetic field. We present the results from the analysis of two regions within the Hi-C field-of-view. Hi-C data is also used to determine the temperature and density of structures and we offer conclusions on the spatial scale for these features. Title: Detecting Nanoflare Heating Events in Subarcsecond Inter-moss Loops Using Hi-C Authors: Winebarger, Amy R.; Walsh, Robert W.; Moore, Ronald; De Pontieu, Bart; Hansteen, Viggo; Cirtain, Jonathan; Golub, Leon; Kobayashi, Ken; Korreck, Kelly; DeForest, Craig; Weber, Mark; Title, Alan; Kuzin, Sergey Bibcode: 2013ApJ...771...21W Altcode: The High-resolution Coronal Imager (Hi-C) flew aboard a NASA sounding rocket on 2012 July 11 and captured roughly 345 s of high-spatial and temporal resolution images of the solar corona in a narrowband 193 Å channel. In this paper, we analyze a set of rapidly evolving loops that appear in an inter-moss region. We select six loops that both appear in and fade out of the Hi-C images during the short flight. From the Hi-C data, we determine the size and lifetimes of the loops and characterize whether these loops appear simultaneously along their length or first appear at one footpoint before appearing at the other. Using co-aligned, co-temporal data from multiple channels of the Atmospheric Imaging Assembly on the Solar Dynamics Observatory, we determine the temperature and density of the loops. We find the loops consist of cool (~105 K), dense (~1010 cm-3) plasma. Their required thermal energy and their observed evolution suggest they result from impulsive heating similar in magnitude to nanoflares. Comparisons with advanced numerical simulations indicate that such dense, cold and short-lived loops are a natural consequence of impulsive magnetic energy release by reconnection of braided magnetic field at low heights in the solar atmosphere. Title: Dynamics of the Transition Corona Authors: Masson, Sophie; McCauley, P.; Golub, L.; Reeves, K.; DeLuca, E. E. Bibcode: 2013SPD....44...27M Altcode: Magnetic reconnection between open and closed magnetic field in the corona is believed to play a crucial role in the corona / heliosphere coupling. At large scale, the exchange of open /closed connectivity is expected to occur in pseudo-streamer structures. However, there is neither clear observational evidence of how such coupling occurs in pseudo-streamers, nor evidence for how the magnetic reconnection evolves. Using a newly-developed technique, we enhance the off-limb magnetic fine structures observed with AIA and identify a pseudo-streamer-like feature located close to the northern coronal hole. We first identify that the magnetic topology associated with the observation is a pseudo-streamer, null-point-related topology bounded by open field. We then compare the evolution of the observed pseudo- streamer fine structure in the location of strong currents, i.e. in the region of energy dissipation, with the dynamics of the magnetic field resulting from the interchange reconnection obtained in a fully 3D MHD simulation. The morphological and dynamical similarities between the pseudo-streamer observations and the results from the simulation strongly suggest that the evolution of the pseudo-streamer is caused by interchange reconnection in a null-point topology that is embedded in Quasi-Separatrix layers. Besides identifying the mechanism at work in the large-scale coupling between open and closed field, our results highlight that interchange reconnection in pseudo-streamers is a gradual physical process that differs from the impulsive reconnection of the solar-jet model. Title: The Interface Region Imaging Spectrograph (IRIS) Authors: De Pontieu, Bart; Title, A. M.; Lemen, J.; Wuelser, J.; Tarbell, T. D.; Schrijver, C. J.; Golub, L.; Kankelborg, C.; Carlsson, M.; Hansteen, V. H.; Worden, S.; IRIS Team Bibcode: 2013SPD....44...03D Altcode: The solar chromosphere and transition region (TR) form a highly structured and dynamic interface region between the photosphere and the corona. This region not only acts as the conduit of all mass and energy feeding into the corona and solar wind, it also requires an order of magnitude more energy to heat than the corona. Nevertheless, the chromosphere remains poorly understood, because of the complexity of the required observational and analytical tools: the interface region is highly complex with transitions from optically thick to optically thin radiation, from pressure to magnetic field domination, and large density and temperature contrasts on small spatial scales. The Interface Region Imaging Spectrograph (IRIS) was selected for a NASA SMEX mission in 2009 and is scheduled to launch on 26-June-2013 (with first light scheduled for mid July). IRIS addresses critical questions: (1) Which types of non-thermal energy dominate in the chromosphere and beyond? (2) How does the chromosphere regulate mass and energy supply to the corona and heliosphere? (3) How do magnetic flux and matter rise through the lower atmosphere, and what role does flux emergence play in flares and mass ejections? These questions are addressed with a high-resolution near and far UV imaging spectrometer sensitive to emission from plasma at temperatures between 5,000 K and 10 MK. IRIS has a field-of-view of 120 arcsec, a spatial resolution of 0.4 arcsec, and velocity resolution of 0.5 km/s. The IRIS investigation includes a strong numerical modeling component based on advanced radiative MHD codes to facilitate interpretation of observations. We describe the IRIS instrumentation and numerical modeling, and present the plans for observations, calibration and data distribution. We will highlight some of the issues that IRIS observations can help resolve. More information can be found at http://iris.lmsal.com Title: Observing Coronal Nanoflares in Active Region Moss Authors: Testa, Paola; De Pontieu, Bart; Martínez-Sykora, Juan; DeLuca, Ed; Hansteen, Viggo; Cirtain, Jonathan; Winebarger, Amy; Golub, Leon; Kobayashi, Ken; Korreck, Kelly; Kuzin, Sergey; Walsh, Robert; DeForest, Craig; Title, Alan; Weber, Mark Bibcode: 2013ApJ...770L...1T Altcode: 2013arXiv1305.1687T The High-resolution Coronal Imager (Hi-C) has provided Fe XII 193Å images of the upper transition region moss at an unprecedented spatial (~0.''3-0.''4) and temporal (5.5 s) resolution. The Hi-C observations show in some moss regions variability on timescales down to ~15 s, significantly shorter than the minute-scale variability typically found in previous observations of moss, therefore challenging the conclusion of moss being heated in a mostly steady manner. These rapid variability moss regions are located at the footpoints of bright hot coronal loops observed by the Solar Dynamics Observatory/Atmospheric Imaging Assembly in the 94 Å channel, and by the Hinode/X-Ray Telescope. The configuration of these loops is highly dynamic, and suggestive of slipping reconnection. We interpret these events as signatures of heating events associated with reconnection occurring in the overlying hot coronal loops, i.e., coronal nanoflares. We estimate the order of magnitude of the energy in these events to be of at least a few 1023 erg, also supporting the nanoflare scenario. These Hi-C observations suggest that future observations at comparable high spatial and temporal resolution, with more extensive temperature coverage, are required to determine the exact characteristics of the heating mechanism(s). Title: Bright Points: Multithermal Analysis as a Test of Steady Heating Models Authors: Schmelz, J. T.; Winebarger, A. R.; Kimble, J. A.; Pathak, S.; Golub, L.; Jenkins, B. S.; Worley, B. T. Bibcode: 2013ApJ...770..160S Altcode: X-ray bright points are small, million-degree features in the solar atmosphere composed of short coronal loops. They are magnetically driven structures associated with photospheric magnetic bipoles. Their relatively small size and simple structure suggest they are ideal candidates for comparisons with coronal heating models. In this paper, we present the analysis of 12 bright points using data from the EUV Imaging Spectrometer on Hinode and the Michelson Doppler Imager on Solar and Heliospheric Observatory. Using the spectroscopy data, we construct differential emission measure (DEM) curves, calculate the electron density, and find DEM-weighted temperatures. In addition, we determine the most likely ionization balance. Using the magnetic field observations, we complete potential field extrapolations of the magnetograms and estimate the loop lengths. Using this information, we construct models assuming the bright points are formed of hundreds of strands, each heated steadily and uniformly. We formulate the models so that the observed emission measure distribution is matched within a few percent. We then compare the densities determined from the models, (1.4-5.0) × 109, to those calculated from spectral data, (0.6-2.0) × 109. We find the majority of bright points do not agree with steady uniform heating models; instead they are underdense relative to their expected density by a factor of 0.16-0.82. Title: SDO/AIA Prominence physical conditions Authors: Schmieder, B.; Parenti, S.; Dudik, J.; Aulanier, G.; Heinzel, P.; Zapior, M.; Golub, L. Bibcode: 2013enss.confE..27S Altcode: SDO/AIA has carried out continuous observations of prominences in multiple wavelengths, with high spatial and temporal resolution. These data provide us an opportunity to understand the physical conditions and dynamics of prominences. The surprising brightness of prominences in some coronal lines has been well explained by the presence of transition region lines in the bandpass of the filters (171 A, 131 A), a result that leads us to revise our model of the transition region of prominences and to consider a relatively dense transition region in some prominence evolutionary phases or in some viewing orientation. An additional aspect of prominence dynamics will be presented with a new quasi-static MHD model proposed for bubbles and plumes. We propose an alternative to the interpretation that thermal instabilities are responsible for the formation of bubbles. The bubbles are found to correspond to magnetic separatrices formed by emerging magnetic field close to prominence footpoints. Title: Three 2012 Transits of Venus: From Earth, Jupiter, and Saturn Authors: Pasachoff, Jay M.; Schneider, G.; Babcock, B. A.; Lu, M.; Edelman, E.; Reardon, K.; Widemann, T.; Tanga, P.; Dantowitz, R.; Silverstone, M. D.; Ehrenreich, D.; Vidal-Madjar, A.; Nicholson, P. D.; Willson, R. C.; Kopp, G. A.; Yurchyshyn, V. B.; Sterling, A. C.; Scherrer, P. H.; Schou, J.; Golub, L.; McCauley, P.; Reeves, K. Bibcode: 2013AAS...22131506P Altcode: We observed the 2012 June 6/5 transit seen from Earth (E/ToV), simultaneously with Venus Express and several other spacecraft not only to study the Cytherean atmosphere but also to provide an exoplanet-transit analog. From Haleakala, the whole transit was visible in coronal skies; among our instruments was one of the world-wide Venus Twilight Experiment's nine coronagraphs. Venus's atmosphere became visible before first contact. SacPeak/IBIS provided high-resolution images at Hα/carbon-dioxide. Big Bear's NST also provided high-resolution observations of the Cytherean atmosphere and black-drop evolution. Our liaison with UH's Mees Solar Observatory scientists provided magneto-optical imaging at calcium and potassium. Solar Dynamics Observatory's AIA and HMI, and the Solar Optical Telescope (SOT) and X-ray Telescope (XRT) on Hinode, and total-solar-irradiance measurements with ACRIMSAT and SORCE/TIM, were used to observe the event as an exoplanet-transit analog. On September 20, we imaged Jupiter for 14 Hubble Space Telescope orbits, centered on a 10-hour ToV visible from Jupiter (J/ToV), as an exoplanet-transit analog in our own solar system, using Jupiter as an integrating sphere. Imaging was good, although much work remains to determine if we can detect the expected 0.01% solar irradiance decrease at Jupiter and the even slighter differential effect between our violet and near-infrared filters caused by Venus's atmosphere. We also give a first report on our currently planned December 21 Cassini UVIS observations of a transit of Venus from Saturn (S/ToV). Our E/ToV expedition was sponsored by the Committee for Research and Exploration/National Geographic Society; supplemented: NASA/AAS's Small Research Grant Program. We thank Rob Ratkowski, Stan Truitt, Rob Lucas, Aram Friedman, and Eric Pilger '82 at Haleakala, and Joseph Gangestad '06 at Big Bear for assistance, and Lockheed Martin Solar and Astrophysics Lab and Hinode science and operations teams for support for coordinated observations with NASA satellites. Our J/ToV observations were based on observations made with HST, operated by AURA, Inc., under NASA contract NAS 5-26555; these observations are associated with program #13067. Title: Energy release in the solar corona from spatially resolved magnetic braids Authors: Cirtain, J. W.; Golub, L.; Winebarger, A. R.; de Pontieu, B.; Kobayashi, K.; Moore, R. L.; Walsh, R. W.; Korreck, K. E.; Weber, M.; McCauley, P.; Title, A.; Kuzin, S.; Deforest, C. E. Bibcode: 2013Natur.493..501C Altcode: It is now apparent that there are at least two heating mechanisms in the Sun's outer atmosphere, or corona. Wave heating may be the prevalent mechanism in quiet solar periods and may contribute to heating the corona to 1,500,000 K (refs 1, 2, 3). The active corona needs additional heating to reach 2,000,000-4,000,000 K this heat has been theoretically proposed to come from the reconnection and unravelling of magnetic `braids'. Evidence favouring that process has been inferred, but has not been generally accepted because observations are sparse and, in general, the braided magnetic strands that are thought to have an angular width of about 0.2 arc seconds have not been resolved. Fine-scale braiding has been seen in the chromosphere but not, until now, in the corona. Here we report observations, at a resolution of 0.2 arc seconds, of magnetic braids in a coronal active region that are reconnecting, relaxing and dissipating sufficient energy to heat the structures to about 4,000,000 K. Although our 5-minute observations cannot unambiguously identify the field reconnection and subsequent relaxation as the dominant heating mechanism throughout active regions, the energy available from the observed field relaxation in our example is ample for the observed heating. Title: The Interface Region Imaging Spectrograph (IRIS) Authors: De Pontieu, B.; Title, A. M.; Lemen, J. R.; Wuelser, J.; Tarbell, T. D.; Schrijver, C.; Golub, L.; Kankelborg, C. C.; Hansteen, V. H.; Carlsson, M. Bibcode: 2012AGUFMSH33D2256D Altcode: The solar chromosphere and transition region (TR) form a highly structured and dynamic interface region between the photosphere and the corona. This region not only acts as the conduit of all mass and energy feeding into the corona and solar wind, it also requires an order of magnitude more energy to heat than the corona. Nevertheless, the chromosphere remains poorly understood, because of the complexity of the required observational and analytical tools: the interface region is highly complex with transitions from optically thick to optically thin radiation, from pressure to magnetic field domination, and large density and temperature contrasts on small spatial scales. The Interface Region Imaging Spectrograph (IRIS) was selected for a NASA SMEX mission in 2009 and is scheduled to launch in early 2013. IRIS addresses critical questions: (1) Which types of non-thermal energy dominate in the chromosphere and beyond? (2) How does the chromosphere regulate mass and energy supply to the corona and heliosphere? (3) How do magnetic flux and matter rise through the lower atmosphere, and what role does flux emergence play in flares and mass ejections? These questions are addressed with a high-resolution near and far UV imaging spectrometer sensitive to emission from plasma at temperatures between 5,000 K and 10 MK. IRIS has a field-of-view of 120 arcsec, a spatial resolution of 0.4 arcsec, and velocity resolution of 0.5 km/s. The IRIS investigation includes a strong numerical modeling component based on advanced radiative MHD codes to facilitate interpretation of observations. We will describe the IRIS instrumentation and numerical modeling, and present the status of the IRIS observatory development. We will highlight some of the issues that IRIS observations can help resolve. Title: Loop Evolution Observed with AIA and Hi-C Authors: Mulu-Moore, F.; Winebarger, A. R.; Cirtain, J. W.; Kobayashi, K.; Korreck, K. E.; Golub, L.; Kuzin, S.; Walsh, R. W.; DeForest, C.; De Pontieu, B.; Title, A. M.; Weber, M. Bibcode: 2012AGUFMSH33A2225M Altcode: In the past decade, the evolution of EUV loops has been used to infer the loop substructure. With the recent launch of High Resolution Coronal Imager (Hi-C), this inference can be validated. In this presentation we discuss the first results of loop analysis comparing AIA and Hi-C data. Title: The Fundamental Structure of Coronal Loops Authors: Winebarger, A. R.; Warren, H. P.; Cirtain, J. W.; Kobayashi, K.; Korreck, K. E.; Golub, L.; Kuzin, S.; Walsh, R. W.; DeForest, C.; De Pontieu, B.; Title, A. M.; Weber, M. Bibcode: 2012AGUFMSH31B..06W Altcode: During the past ten years, solar physicists have attempted to infer the coronal heating mechanism by comparing observations of coronal loops with hydrodynamic model predictions. These comparisons often used the addition of sub-resolution strands to explain the observed loop properties. On July 11, 2012, the High Resolution Coronal Imager (Hi-C) was launched on a sounding rocket. This instrument obtained images of the solar corona was 0.2-0.3'' resolution in a narrowband EUV filter centered around 193 Angstroms. In this talk, we will compare these high resolution images to simultaneous density measurements obtained with the Extreme Ultraviolet Imaging Spectrograph (EIS) on Hinode to determine whether the structures observed with Hi-C are resolved. Title: Science Enabled by Advances in UV/EUV Technologies Authors: Golub, L. Bibcode: 2012AGUFMSA13D..01G Altcode: The development of EUV multilayer coating technology has permitted high-quality reflective optics to be constructed for operation at EUV wavelengths, and the availability of low-cost rapid flight opportunities has enabled the use of this technology to address major questions in solar science. We present a brief overview of the way in which the technology developed and was applied to solar studies and we discuss some of the significant achievements that have resulted from the use of this instrumentation in sounding rockets and satellites. We conclude with a discussion of some new directions for this technology and some indications of the directions that the work may take. Title: The 2012 Transit of Venus for Cytherean Atmospheric Studies and as an Exoplanet Analog Authors: Pasachoff, Jay M.; Schneider, G.; Babcock, B. A.; Lu, M.; Reardon, K. P.; Widemann, T.; Tanga, P.; Dantowitz, R.; Willson, R.; Kopp, G.; Yurchyshyn, V.; Sterling, A.; Scherrer, P.; Schou, J.; Golub, L.; Reeves, K. Bibcode: 2012DPS....4450806P Altcode: We worked to assemble as complete a dataset as possible for the Cytherean atmosphere in collaboration with Venus Express in situ and to provide an analog of spectral and total irradiance exoplanet measurements. From Haleakala, the whole transit was visible in coronal skies; our B images showed the evolution of the visibility of Venus's atmosphere and of the black-drop effect, as part of the Venus Twilight Experiment's 9 coronagraphs distributed worldwide with BVRI. We imaged the Cytherean atmosphere over two minutes before first contact, with subarcsecond resolution, with the coronagraph and a separate refractor. The IBIS imaging spectrometer at Sacramento Peak Observatory at H-alpha and carbon-dioxide also provided us high-resolution imaging. The NST of Big Bear Solar Observatory also provided high-resolution vacuum observations of the Cytherean atmosphere and black drop evolution. Our liaison with UH's Mees Solar Observatory scientists provided magneto-optical imaging at calcium and potassium. Spaceborne observations included the Solar Dynamics Observatory's AIA and HMI, and the Solar Optical Telescope (SOT) and X-ray Telescope (XRT) on Hinode, and total-solar-irradiance measurements with ACRIMSAT and SORCE/TIM, to characterize the event as an exoplanet-transit analog. Our expedition was sponsored by the Committee for Research and Exploration/National Geographic Society. Some of the funds for the carbon-dioxide filter for IBIS were provided by NASA through AAS's Small Research Grant Program. We thank Rob Lucas, Aram Friedman, and Eric Pilger '82 for assistance with Haleakala observing, Rob Ratkowski of Haleakala Amateur Astronomers for assistance with equipment and with the site, Stan Truitt for the loan of his Paramount ME, and Steve Bisque/Software Bisque for TheSky X controller. We thank Joseph Gangestad '06 of Aerospace Corp., a veteran of our 2004 expedition, for assistance at Big Bear. We thank the Lockheed Martin Solar and Astrophysics Laboratory and Hinode science and operations teams for planning and support. Title: Design, performance prediction, and measurements of the interface region imaging spectrograph (IRIS) telescope Authors: Podgorski, William A.; Cheimets, Peter N.; Golub, Leon; Lemen, James R.; Title, Alan M. Bibcode: 2012SPIE.8443E..3DP Altcode: This paper discusses the design of the IRIS Small Explorer (SMEX) Cassegrain telescope, as well as its intended and measured performance. Lockheed Martin, along with SAO, Montana State University, and Stanford University are developing the IRIS instrument for a mission to examine the solar spectra in two bands, one centered on 1369 Å, and the other centered on 2810 Å. SAO led the design and construction of the telescope feed, with assistance from Lockheed and Montana State University. The telescope posed a number of implementation challenges, which are discussed here, including the fact that no effective filters exist to isolate the science spectra to the exclusion of the rest of the solar flux, making it necessary to allow full sunlight into the telescope. Title: In-band and out-of-band reflectance calibrations of the EUV multilayer mirrors of the atmospheric imaging assembly instrument aboard the Solar Dynamics Observatory Authors: Soufli, Regina; Spiller, Eberhard; Windt, David L.; Robinson, Jeff C.; Gullikson, Eric M.; Rodriguez-de Marcos, Luis; Fernandez-Perea, Monica; Baker, Sherry L.; Aquila, Andrew L.; Dollar, Franklin J.; Méndez, José Antonio; Larruquert, Juan I.; Golub, Leon; Boerner, Paul Bibcode: 2012SPIE.8443E..3CS Altcode: Experimental multilayer reflectance data on flight mirrors and witnesses for three extreme ultraviolet (EUV) channels of the Atmospheric Imaging Assembly (AIA) instrument aboard NASA’s Solar Dynamics Observatory are presented and compared to theoretical models. The relevance of these results to the performance of the AIA instrument is discussed. Title: The interface region imaging spectrograph for the IRIS Small Explorer mission Authors: Wülser, Jean-Pierre; Title, Alan M.; Lemen, James R.; De Pontieu, Bart; Kankelborg, Charles C.; Tarbell, Theodore D.; Berger, Thomas E.; Golub, Leon; Kushner, Gary D.; Chou, Catherine Y.; Weingrod, Isaac; Holmes, Buck; Mudge, Jason; Podgorski, William A. Bibcode: 2012SPIE.8443E..08W Altcode: The Interface Region Imaging Spectrograph (IRIS) is a NASA SMall EXplorer mission scheduled for launch in January 2013. The primary goal of IRIS is to understand how the solar atmosphere is energized. The IRIS investigation combines advanced numerical modeling with a high resolution UV imaging spectrograph. IRIS will obtain UV spectra and images with high resolution in space (0.4 arcsec) and time (1s) focused on the chromosphere and transition region of the Sun, a complex interface region between the photosphere and corona. The IRIS instrument uses a Cassegrain telescope to feed a dual spectrograph and slit-jaw imager that operate in the 133-141 nm and 278-283 nm ranges. This paper describes the instrument with emphasis on the imaging spectrograph, and presents an initial performance assessment from ground test results. Title: Asymmetric Structure of Quiescent Filament Channels Observed by Hinode/XRT and STEREO/EUVI Authors: Su, Y.; van Ballegooijen, A.; Golub, L. Bibcode: 2012ASPC..454..113S Altcode: 2012arXiv1208.1529S We present a study on the structure of quiescent filament channels observed by Hinode/XRT and STEREO/EUVI from December 2006 to February 2009. For 10 channels identified on the solar disk, we find that the emission on the two sides of the channel is asymmetric in both X-rays and EUV: one side has curved bright features while the other side has straight faint features. We interpret the results in terms of a magnetic flux rope model. The asymmetry in the emission is due to the variation in axial magnetic flux along the channel, which causes one polarity to turn into the flux rope, while the field lines from the other polarity are open or connected to very distant sources. For 70 channels identified by cavities at the limb, the asymmetry cannot be clearly identified. Title: Cooler and Hotter X-ray Bright Points from Hinode/XRT Observations Authors: Kariyappa, R.; DeLuca, E. E.; Saar, S. H.; Golub, L.; Damé, L.; Varghese, B. A. Bibcode: 2012ASPC..454..149K Altcode: We use a 7-hour (17:00 UT - 24:00 UT) time sequence of soft X-ray images observed almost simultaneously in two filters (Ti_poly and Al_mesh) on April 14, 2007 with X-Ray Telescope (XRT) on-board the Hinode mission to determine the temperature of X-ray bright points (XBPs). A sample of 14 XBPs and 2 background coronal regions have been identified and selected on both the images for detailed analysis. The temperature of XBPs is determined by filter ratio method. We find that the XBPs show temperature fluctuations and that the average temperature ranges from 1.1 MK to 3.4 MK which may correspond to different X-ray fluxes. These results suggest the existence of cooler and hotter XBPs and that the heating rate of XBPs is highly variable on short time scales. Title: Prominences observations with SDO/AIA Authors: Parenti, Susanna; Schmieder, Brigitte; Golub, Leon; Heinzel, Petr Bibcode: 2012cosp...39.1447P Altcode: 2012cosp.meet.1447P The Prominence-Corona-Transition-Region (PCTR) plays a key role in the thermal and pressure equilibrium of prominences. However, several open issues limit our knowledge of this important interface. Among them we find the thermal structure and the maximum temperature of its emitting plasma. This work is a new step toward resolving these issues. By noting that prominences may be observed in emission in the 171 and 131 SDO/AIA images, while they are seen in absorption in others (e.g. 193) we investigate the temperature content of these channels. Using the CHIANTI atomic database and previously derived prominence DEMs, we built synthetic spectra in these AIA channels to establish the main contributors. We find that the Fe IX line always dominates the 171 band, even in absence of a coronal plasma, while the 131 channel is dominated by Fe VIII. Our conclusion is that the PCTR reaches, at least, 4x 10^5 K. Title: On the Nature of Prominence Emission Observed by SDO/AIA Authors: Parenti, S.; Schmieder, B.; Heinzel, P.; Golub, L. Bibcode: 2012ApJ...754...66P Altcode: 2012arXiv1205.5460P The prominence-corona transition region (PCTR) plays a key role in the thermal and pressure equilibrium of solar prominences. Our knowledge of this interface is limited and several major issues remain open, including the thermal structure and, in particular, the maximum temperature of the detectable plasma. The high signal-to-noise ratio of images obtained by the Atmospheric Imaging Assembly (AIA) on NASA's Solar Dynamics Observatory clearly shows that prominences are often seen in emission in the 171 and 131 bands. We investigate the temperature sensitivity of these AIA bands for prominence observations, in order to infer the temperature content in an effort to explain the emission. Using the CHIANTI atomic database and previously determined prominence differential emission measure distributions, we build synthetic spectra to establish the main emission-line contributors in the AIA bands. We find that the Fe IX line always dominates the 171 band, even in the absence of plasma at >106 K temperatures, while the 131 band is dominated by Fe VIII. We conclude that the PCTR has sufficient plasma emitting at >4 × 105 K to be detected by AIA. Title: Plasmoid Ejection at a Solar Total Eclipse Authors: Koutchmy, S.; Bazin, C.; Berghmans, D.; De Groof, A.; Druckmüller, M.; Tavabi, E.; Engell, A.; Filippov, B.; Golub, L.; Lamy, Ph.; Linker, J.; Mikic, Z.; Mouette, J.; Nitschelm, Ch.; Seaton, D.; Slemzin, V. Bibcode: 2012EAS....55..223K Altcode: The existence of coronal plasmoids has been postulated for many years in order to supply material to streamers and possibly to the solar wind (SW). The W-L SoHO C2 Lasco coronagraph observations were made under the 2.2 solar radii (R0) occulting disk to look at the ultimate sources of the SW; EUV imagers are preferably devoted to the analysis of the corona on and very near the solar disk. Here, in addition to eclipse white-light (W-L) snapshots, we used the new SWAP space-borne imager designed for the systematic survey of coronal activity in the EUV lines near 17.4 nm, over a field of view (FOV) up to 2 R0. Using summed and co-aligned images, the corona can then be evaluated for the 1st time up to the limit of this FOV. At the time of the July 11, 2010, solar total eclipse a 20h continuous run of observations was collected, including images taken during eclipse totality from several ground observing locations where W-L data were collected. A plasmoid-like off-limb event was followed using the SWAP summed Title: On the Visibility of Solar Prominences in SDO/AIA Channels Authors: Heinzel, P.; Schmieder, B.; Parenti, S.; Golub, L. Bibcode: 2012ASPC..456...75H Altcode: Prominences in EUV lines are observed as dark structures over the limb due absorption and emission blocking mechanisms. However, at 171 Å is observed emission in prominences with TRACE and SDO/AIA, and it is believed to be due to the prominence-corona transition region (PCTR) emitting in cool lines. To check this, we use the Differential Emission Measure (DEM) recently obtained for quiescent prominences using SOHO/SUMER spectra (Parenti and Vial 2007) and compute the synthetic spectra in selected AIA channels. We then compare 171 Å and 195 Å channels and derive conclusions concerning the PCTR emissivity, as well well as the absorption and blocking. The emission seen in the 171 Å channel can be used to better constrain prominence DEM curves. Title: Temperature Diagnostic of a Brightening Observed by Hinode/XRT Authors: Dudík, J.; Reeves, K. K.; Schmieder, B.; Dzifčáková, E.; Golub, L. Bibcode: 2012ASPC..456..137D Altcode: We analyze the temperature distribution of the active region brightening observed by HINODE/XRT. The temperature structure is derived using various filter-ratio techniques and DEM analysis. The results are compared and it is found that the filter-ratio techniques are accurate only for relatively narrow DEMs. Title: Hot Plasma Detected in Active Regions by HINODE/XRT and SDO/AIA Authors: Reale, F.; Testa, P.; Guarrasi, M.; DeLuca, E.; Peres, G.; Golub, L. Bibcode: 2012ASPC..456..129R Altcode: Multiple ratios of Hinode/XRT filters showed evidence of a minor very hot emission measure component in active regions. Recently also SDO/AIA detected hot plasma in the core of an active region. Here we provide estimates showing that the amount of emission measure of the hot component detected with SDO is consistent with that detected with Hinode/XRT. Title: The Fifth Hinode Science Meeting Authors: Golub, L.; De Moortel, I.; Shimizu, T. Bibcode: 2012ASPC..456.....G Altcode: No abstract at ADS Title: Differential Emission Measure Analysis for AIA and XRT Observations of Comet Lovejoy (C/2011 W3) Authors: McCauley, Patrick; Saar, S. H.; Raymond, J.; Golub, L. E. Bibcode: 2012AAS...22020115M Altcode: We present observations of Comet Lovejoy (C/2011 W3) recorded by the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory (SDO) and the X-Ray Telescope (XRT) aboard the Hinode satellite. Lovejoy, a member of the Kreutz family of sungrazing comets, came to within 1.2 solar radii during its perihelion approach and escaped, despite expectations to the contrary, on December 6, 2011. The most significant sungrazer since the launch of SDO, Lovejoy provides an unprecedented opportunity to examine the effects of a comet traversing the solar corona. Both the ingress and egress were detected in seven AIA passbands (131, 171, 193, 211, 304, 335, and 1600 Angstroms), with XRT successfully imaging the outbound trip using its Al-mesh filter. We estimate the temperature structure of the emitting plasma using a differential emission measure analysis and explore interactions with the solar magnetic field. In several cases, secondary lines in a given channel appear to be the dominant comet-related emitters. Use of a radial filter for improved contrast of the faint cometary emission is also discussed. Title: Defining the "Blind Spot" of Hinode EIS and XRT Temperature Measurements Authors: Winebarger, Amy R.; Warren, Harry P.; Schmelz, Joan T.; Cirtain, Jonathan; Mulu-Moore, Fana; Golub, Leon; Kobayashi, Ken Bibcode: 2012ApJ...746L..17W Altcode: Observing high-temperature, low emission measure plasma is key to unlocking the coronal heating problem. With current instrumentation, a combination of EUV spectral data from Hinode Extreme-ultraviolet Imaging Spectrometer (EIS; sensitive to temperatures up to 4 MK) and broadband filter data from Hinode X-ray Telescope (XRT; sensitive to higher temperatures) is typically used to diagnose the temperature structure of the observed plasma. In this Letter, we demonstrate that a "blind spot" exists in temperature-emission measure space for combined Hinode EIS and XRT observations. For a typical active region core with significant emission at 3-4 MK, Hinode EIS and XRT are insensitive to plasma with temperatures greater than ~6 MK and emission measures less than ~1027 cm-5. We then demonstrate that the temperature and emission measure limits of this blind spot depend upon the temperature distribution of the plasma along the line of sight by considering a hypothetical emission measure distribution sharply peaked at 1 MK. For this emission measure distribution, we find that EIS and XRT are insensitive to plasma with emission measures less than ~1026 cm-5. We suggest that a spatially and spectrally resolved 6-24 Å spectrum would improve the sensitivity to these high-temperature, low emission measure plasma. Title: The Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO) Authors: Lemen, James R.; Title, Alan M.; Akin, David J.; Boerner, Paul F.; Chou, Catherine; Drake, Jerry F.; Duncan, Dexter W.; Edwards, Christopher G.; Friedlaender, Frank M.; Heyman, Gary F.; Hurlburt, Neal E.; Katz, Noah L.; Kushner, Gary D.; Levay, Michael; Lindgren, Russell W.; Mathur, Dnyanesh P.; McFeaters, Edward L.; Mitchell, Sarah; Rehse, Roger A.; Schrijver, Carolus J.; Springer, Larry A.; Stern, Robert A.; Tarbell, Theodore D.; Wuelser, Jean-Pierre; Wolfson, C. Jacob; Yanari, Carl; Bookbinder, Jay A.; Cheimets, Peter N.; Caldwell, David; Deluca, Edward E.; Gates, Richard; Golub, Leon; Park, Sang; Podgorski, William A.; Bush, Rock I.; Scherrer, Philip H.; Gummin, Mark A.; Smith, Peter; Auker, Gary; Jerram, Paul; Pool, Peter; Soufli, Regina; Windt, David L.; Beardsley, Sarah; Clapp, Matthew; Lang, James; Waltham, Nicholas Bibcode: 2012SoPh..275...17L Altcode: 2011SoPh..tmp..106L; 2011SoPh..tmp..172L; 2011SoPh..tmp..241L; 2011SoPh..tmp..115L The Atmospheric Imaging Assembly (AIA) provides multiple simultaneous high-resolution full-disk images of the corona and transition region up to 0.5 R⊙ above the solar limb with 1.5-arcsec spatial resolution and 12-second temporal resolution. The AIA consists of four telescopes that employ normal-incidence, multilayer-coated optics to provide narrow-band imaging of seven extreme ultraviolet (EUV) band passes centered on specific lines: Fe XVIII (94 Å), Fe XVII, XXI (131 Å), Fe IX (171 Å), Fe XII, XXIV (193 Å), Fe XIV (211 Å), He II (304 Å), and Fe XVI (335 Å). One telescope observes C IV (near 1600 Å) and the nearby continuum (1700 Å) and has a filter that observes in the visible to enable coalignment with images from other telescopes. The temperature diagnostics of the EUV emissions cover the range from 6×104 K to 2×107 K. The AIA was launched as a part of NASA's Solar Dynamics Observatory (SDO) mission on 11 February 2010. AIA will advance our understanding of the mechanisms of solar variability and of how the Sun's energy is stored and released into the heliosphere and geospace. Title: Initial Calibration of the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO) Authors: Boerner, Paul; Edwards, Christopher; Lemen, James; Rausch, Adam; Schrijver, Carolus; Shine, Richard; Shing, Lawrence; Stern, Robert; Tarbell, Theodore; Title, Alan; Wolfson, C. Jacob; Soufli, Regina; Spiller, Eberhard; Gullikson, Eric; McKenzie, David; Windt, David; Golub, Leon; Podgorski, William; Testa, Paola; Weber, Mark Bibcode: 2012SoPh..275...41B Altcode: The Atmospheric Imaging Assembly (AIA) instrument onboard the Solar Dynamics Observatory (SDO) is an array of four normal-incidence reflecting telescopes that image the Sun in ten EUV and UV wavelength channels. We present the initial photometric calibration of AIA, based on preflight measurements of the response of the telescope components. The estimated accuracy is of order 25%, which is consistent with the results of comparisons with full-disk irradiance measurements and spectral models. We also describe the characterization of the instrument performance, including image resolution, alignment, camera-system gain, flat-fielding, and data compression. Title: Observations and Interpretation of a Low Coronal Shock Wave Observed in the EUV by the SDO/AIA Authors: Ma, Suli; Raymond, John C.; Golub, Leon; Lin, Jun; Chen, Huadong; Grigis, Paolo; Testa, Paola; Long, David Bibcode: 2011ApJ...738..160M Altcode: 2011arXiv1106.6056M Taking advantage of both the high temporal and spatial resolutions of the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory, we studied a limb coronal shock wave and its associated extreme ultraviolet (EUV) wave that occurred on 2010 June 13. Our main findings are: (1) the shock wave appeared clearly only in the channels centered at 193 Å and 211 Å as a dome-like enhancement propagating ahead of its associated semi-spherical coronal mass ejection (CME) bubble; (2) the density compression of the shock is 1.56 according to radio data and the temperature of the shock is around 2.8 MK (3) the shock wave first appeared at 05:38 UT, 2 minutes after the associated flare has started and 1 minute after its associated CME bubble appeared; (4) the top of the dome-like shock wave set out from about 1.23 R sun and the thickness of the shocked layer is ~2 × 104 km (5) the speed of the shock wave is consistent with a slight decrease from about 600 km s-1 to 550 km s-1 and (6) the lateral expansion of the shock wave suggests a constant speed around 400 km s-1, which varies at different heights and directions. Our findings support the view that the coronal shock wave is driven by the CME bubble, and the on-limb EUV wave is consistent with a fast wave or at least includes the fast wave component. Title: The Marshall Grazing Incidence X-ray Spectrograph (MaGIXS) Authors: Kobayashi, Ken; Cirtain, Jonathan; Golub, Leon; Winebarger, Amy; Hertz, Edward; Cheimets, Peter; Caldwell, David; Korreck, Kelly; Robinson, Brian; Reardon, Patrick; Kester, Thomas; Griffith, Charles; Young, Mark Bibcode: 2011SPIE.8147E..1MK Altcode: 2011SPIE.8147E..54K The Marshall Grazing Incidence X-ray Spectrograph (MaGIXS) is a proposed sounding rocket experiment designed to observe spatially resolved soft X-ray spectra of the solar corona for the first time. The instrument is a purely grazing-incidence design, consisting of aWolter Type-1 sector telescope and a slit spectrograph. The telescope mirror is a monolithic Zerodur mirror with both the parabolic and hyperbolic surfaces. The spectrograph comprises a pair of paraboloid mirrors acting as a collimator and reimaging mirror, and a planar varied-line-space grating, with reflective surfaces operate at a graze angle of 2 degrees. This produces a flat spectrum on a detector covering a wavelength range of 6-24Å (0.5-1.2 keV). The design achieves 20 mÅ spectral resolution (10 mÅ /pixel) and 5 arcsec spatial resolution (2.5 arcsec / pixel) over an 8-arcminute long slit. The spectrograph is currently being fabricated as a laboratory prototype. A flight candidate telescope mirror is also under development. Title: Solar Dynamics Observatory Discovers Thin High Temperature Strands in Coronal Active Regions Authors: Reale, Fabio; Guarrasi, Massimiliano; Testa, Paola; DeLuca, Edward E.; Peres, Giovanni; Golub, Leon Bibcode: 2011ApJ...736L..16R Altcode: 2011arXiv1106.1591R One scenario proposed to explain the million degree solar corona is a finely stranded corona where each strand is heated by a rapid pulse. However, such fine structure has neither been resolved through direct imaging observations nor conclusively shown through indirect observations of extended superhot plasma. Recently, it has been shown that the observed difference in the appearance of cool and warm coronal loops (~1 MK and ~2-3 MK, respectively)—warm loops appearing "fuzzier" than cool loops—can be explained by models of loops composed of subarcsecond strands, which are impulsively heated up to ~10 MK. That work predicts that images of hot coronal loops (gsim 6 MK) should again show fine structure. Here we show that the predicted effect is indeed widely observed in an active region with the Solar Dynamics Observatory, thus supporting a scenario where impulsive heating of fine loop strands plays an important role in powering the active corona. Title: Structure and Dynamics of the 2010 July 11 Eclipse White-light Corona Authors: Pasachoff, J. M.; Rušin, V.; Druckmüllerová, H.; Saniga, M.; Lu, M.; Malamut, C.; Seaton, D. B.; Golub, L.; Engell, A. J.; Hill, S. W.; Lucas, R. Bibcode: 2011ApJ...734..114P Altcode: The white-light corona (WLC) during the total solar eclipse on 2010 July 11 was observed by several teams in the Moon's shadow stretching across the Pacific Ocean and a number of isolated islands. We present a comparison of the WLC as observed by eclipse teams located on the Tatakoto Atoll in French Polynesia and on Easter Island, 83 minutes later, combined with near-simultaneous space observations. The eclipse was observed at the beginning of the solar cycle, not long after solar minimum. Nevertheless, the solar corona shows a plethora of different features (coronal holes, helmet streamers, polar rays, very faint loops and radial-oriented thin streamers, a coronal mass ejection, and a puzzling "curtain-like" object above the north pole). Comparing the observations from the two sites enables us to detect some dynamic phenomena. The eclipse observations are further compared with a hairy-ball model of the magnetic field and near-simultaneous images from the Atmospheric Imaging Assembly on NASA's Solar Dynamics Observatory, the Extreme Ultraviolet Imager on NASA's Solar Terrestrial Relations Observatory, the Sun Watcher, using Active Pixel System Detector and Image Processing on ESA's PRoject for Onboard Autonomy, and the Naval Research Laboratory's Large Angle and Spectrometric Coronagraph on ESA's Solar and Heliospheric Observatory. The Ludendorff flattening coefficient is 0.156, matching the expected ellipticity of coronal isophotes at 2 R sun, for this rising phase of the solar-activity cycle. Title: Observations and Magnetic Field Modeling of the Flare/coronal Mass Ejection Event on 2010 April 8 Authors: Su, Yingna; Surges, Vincent; van Ballegooijen, Adriaan; DeLuca, Edward; Golub, Leon Bibcode: 2011ApJ...734...53S Altcode: We present a study of the flare/coronal mass ejection event that occurred in Active Region 11060 on 2010 April 8. This event also involves a filament eruption, EIT wave, and coronal dimming. Prior to the flare onset and filament eruption, both SDO/AIA and STEREO/EUVI observe a nearly horizontal filament ejection along the internal polarity inversion line, where flux cancellations frequently occur as observed by SDO/HMI. Using the flux-rope insertion method developed by van Ballegooijen, we construct a grid of magnetic field models using two magneto-frictional relaxation methods. We find that the poloidal flux is significantly reduced during the relaxation process, though one relaxation method preserves the poloidal flux better than the other. The best-fit pre-flare NLFFF model is constrained by matching the coronal loops observed by SDO/AIA and Hinode/XRT. We find that the axial flux in this model is very close to the threshold of instability. For the model that becomes unstable due to an increase of the axial flux, the reconnected field lines below the X-point closely match the observed highly sheared flare loops at the event onset. The footpoints of the erupting flux rope are located around the coronal dimming regions. Both observational and modeling results support the premise that this event may be initiated by catastrophic loss of equilibrium caused by an increase of the axial flux in the flux rope, which is driven by flux cancellations. Title: High-resolution EUV imaging of the solar corona in the ARKA project Authors: Shestov, S.; Bogachev, S.; Kuzin, S.; Golub, L. Bibcode: 2011simi.conf...39S Altcode: ARKA – is a new space-borne mission, being developed in cooperation by Lavochkin Science and Production Association (Russia), Lebedev Physical Institute (Russia) and Smithsonian Astrophysical Laboratory (USA), to be launched in 2018. The main goal of the ARKA project – EUV observation of the solar corona with unprecedented spatial resolution of 0.15 arc.sec./pixel. Such a high resolution will be achieved by using Richey-Chr tien optical schema with F=15 m and large-area 4k x 4k CCD detectors. The instrument promises as significant improvement in resolution over AIA and TRACE as that achieved in going from SOHO/EIT instrument to the TRACE telescope, with consequent likelihood of dramatic advances in our understanding of coronal dynamics. The key scientific goals of these hi-res observations are the following: observations of small-scale magnetic filed in the corona and its role in the heating of coronal plasma, diagnostics of coronal and chromospheric plasma using MHD seismology, observations of when and how 3D magnetic reconnection occurs in flaring active regions, characterization the triggering and initial development of the CMEs.

The ARKA instrumentation is planned to be launched on a KARAT statellite, on the 5th satellite of the Russian small-satellite program. The instrumentation will include 2 high-resolution F=15 m telescopes, one developed by SAO for 193 and one by LPI for 304 spectral range, a full-Sun context imager for 171 and high-energy full-Sun telescope for the 5-100 keV. The two latter instruments will considerably supplement hi-resolution EUV telescopes, allowing full-Sun monitoring of flares and CMEs. Title: Dynamics of Coronal Mass Ejection Origins Authors: Ma, Suli; Lin, J.; Golub, L. Bibcode: 2011SPD....42.1304M Altcode: 2011BAAS..43S.1304M Coronal mass ejections (CMEs) are massive eruptions of magnetised plasma that is believed to be originated from the solar corona. CMEs are known to play a significant role in driving disastrous space weather. This thesis focuses on understanding the dynamics of CMEs source regions with the observations made by STEREO, the Solar Terrestrial Relations Observatory.

The successful launch of STEREO provides us with the first-ever stereoscopic measurements to study the 3D structures of CMEs. With the data from Extreme Ultra-Violet Imager (EUVI) and coronagraphs COR1 and COR2 onboard both STEREO Ahead (A) and STEREO Behind (B) and the data from other instruments, we studied of the initiation of a CME and its associated phenomena. The CME occurs on 2007 December 7, during which the separation angle of STEREO A with B is about 42.4°. This offers us a good opportunity to study the initiation of the CME stereoscopically. Using the data from both STEREO A and B, we made a detailed comparison for the morphologies and kinematics of its associated "EIT wave". The results indicate that the nascent CME seems to affect the morphology of the EIT wave, vise verse, i.e., the morphology of EIT wave reflects the morphology of the CME.

Taking the advantage of the two viewpoints of the STEREO spacecrafts from January 1 to August 31, 2009, we identified 34 CMEs that originated from almost one quarter of the Sun which faces the Earth. It is found that about 33% of them had no distinct low coronal signature (such as coronal dimming, coronal wave, filament eruption, post-eruptive arcade). It might be a new challenge for our present models of CME origination. Title: The Interface Region Imaging Spectrograph (IRIS) NASA SMEX Authors: Lemen, James; Title, A.; De Pontieu, B.; Schrijver, C.; Tarbell, T.; Wuelser, J.; Golub, L.; Kankelborg, C. Bibcode: 2011SPD....42.1512L Altcode: 2011BAAS..43S.1512L The solar chromosphere and transition region (TR) is highly structured, dynamic, and intimately connected to the corona. It requires more than ten times the energy required to heat the corona, and yet it has received far less interest because of the complexity of the required observational and analytical tools. In the TR the density drops by six orders of magnitude and the temperature increases by three orders of magnitude. Hinode observations reveal the importance the magnetic field has on this region of the solar atmosphere that acts as the interface between the photosphere and the corona. The Interface Region Imaging Spectrograph (IRIS) was selected for a NASA SMEX mission in 2009 and is scheduled to launch in December 2012. IRIS addresses critical questions in order to understand the flow of energy and mass through the chromosphere and TR, namely: (1) Which types of non-thermal energy dominate in the chromosphere and beyond? (2) How does the chromosphere regulate mass and energy supply to the corona and heliosphere? (3) How do magnetic flux and matter rise through the lower atmosphere, and what roles dos flux emergence play in flares and mass ejections? These questions are addressed with a high-resolution imaging spectrometer that observes Near- and Far-VU emissions that are formed at temperatures between 5,000K and 1.5 x 106 K. IRIS has a field-of-view of 120 arcsec, a spatial resolution of 0.4 arcsec, and velocity resolution of 0.5 km/s. Members of the IRIS investigation team are developing advanced radiative MHD codes to facilitate comparison with and interpretation of observations. We present the status of the IRIS observatory development, which completed its Critical Design Review in December 2010. Title: The Solar Corona and a CME at the 2010 Total Eclipse Authors: Pasachoff, Jay M.; Rusin, V.; Druckmüllerová, H.; Saniga, M.; Lu, M.; Malamut, C.; Seaton, D. B.; Golub, L.; Engell, A. J.; Hill, S. W.; Lucas, R. Bibcode: 2011SPD....42.1813P Altcode: 2011BAAS..43S.1813P The 11 July 2010 total solar eclipse was observed on the ground from French Polynesia and, 83 minutes later, from Easter Island, and near-simultaneous images were made with spacecraft instruments including AIA/SDO, HMI/SDO, EUVI/STEREO, SWAP/PROBA2, EIT/SOHO, and LASCO/SOHO. We report on changes in the corona detectable with high-resolution image processing of the ground-based eclipse coronal imaging, including two CME's that were seen to evolve. We compare with the spacecraft images to give a complete depiction of coronal structure at the time of the eclipse, which corresponded to a low but rising phase of the solar-activity cycle.

We acknowledge the support of NASA's MSFC NNX10AK47A, NSF REU AST-1005024 with DoD ASSURE, VEGA 2/0098/10 of the Slovak Acad. Sci, 205/09/1469 of the Czech Science Foundation, PRODEX C90345 of ESA/BELSPO, FP7/2007-2013/218816 SOTERIA, Lockheed Martin; for equipment: Nikon Professional Services, ASTELCO Systems GmbH (Germany), and National Geographic Society's Photographic Division; and colleagues Y.-M. Wang (NRL), S. Habbal (U. Hawaii), H. Lanteires (Tatakoto), and J. Kern (Carnegie Obs.). Title: Comparison Of Simulated And Observed Loop-top Emission In Flares Using The AIA Telescopes On SDO Authors: Reeves, Kathy; Engell, A.; Ji, L.; Smith, R.; Golub, L. Bibcode: 2011SPD....42.2122R Altcode: 2011BAAS..43S.2122R We investigate the temporal behavior of loop-top emission in flaring loops observed by AIA's six EUV passbands for several flares of different sizes. These flares are chosen because they exhibit extended periods of loop-top emission in the 193 A channel, thought to be hot emission from Fe XXIV. The flare light curves from this loop-top emission clearly show the progression of flare cooling through the various ionization states of iron that dominate the AIA bands. We use the model of Reeves, Warren & Forbes (2007), which predicts extended periods of loop-top flare emission, to model the flare loop energization, and explore the effects of different energy release rates and durations on the simulated flare light curves. We also explore the conditions under which non-equilibrium ionization effects may be important in these events. Title: Coronal-Temperature-Diagnostic Capability of the Hinode/ X-Ray Telescope Based on Self-Consistent Calibration Authors: Narukage, N.; Sakao, T.; Kano, R.; Hara, H.; Shimojo, M.; Bando, T.; Urayama, F.; DeLuca, E.; Golub, L.; Weber, M.; Grigis, P.; Cirtain, J.; Tsuneta, S. Bibcode: 2011SoPh..269..169N Altcode: 2010arXiv1011.2867N; 2011SoPh..tmp....1N The X-Ray Telescope (XRT) onboard the Hinode satellite is an X-ray imager that observes the solar corona with unprecedentedly high angular resolution (consistent with its 1″ pixel size). XRT has nine X-ray analysis filters with different temperature responses. One of the most significant scientific features of this telescope is its capability of diagnosing coronal temperatures from less than 1 MK to more than 10 MK, which has never been accomplished before. To make full use of this capability, accurate calibration of the coronal temperature response of XRT is indispensable and is presented in this article. The effect of on-orbit contamination is also taken into account in the calibration. On the basis of our calibration results, we review the coronal-temperature-diagnostic capability of XRT. Title: Temperature variability in X-ray bright points observed with Hinode/XRT Authors: Kariyappa, R.; Deluca, E. E.; Saar, S. H.; Golub, L.; Damé, L.; Pevtsov, A. A.; Varghese, B. A. Bibcode: 2011A&A...526A..78K Altcode:
Aims: We investigate the variability in temperature as a function of time among a sample of coronal X-ray bright points (XBPs).
Methods: We analysed a 7-h (17:00-24:00 UT) long time sequence of soft X-ray images observed almost simultaneously in two filters (Ti_poly and Al_mesh) on April 14, 2007 with X-ray telescope (XRT) onboard the Hinode mission. We identified and selected 14 XBPs for a detailed analysis. The light curves of XBPs were derived using the SolarSoft library in IDL. The temperature of XBPs was determined using the calibrated temperature response curves of the two filters by means of the intensity ratio method.
Results: We find that the XBPs show a high variability in their temperature and that the average temperature ranges from 1.1 MK to 3.4 MK. The variations in temperature are often correlated with changes in average X-ray emission. It is evident from the results of time series that the XBP heating rate can be highly variable on short timescales, suggesting that it has a reconnection origin. Title: Atmospheric Imaging Assembly Observations of Hot Flare Plasma Authors: Reeves, Katharine K.; Golub, Leon Bibcode: 2011ApJ...727L..52R Altcode: We present observations of hot plasma from solar eruptions recorded by the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory. AIA is the first narrowband instrument capable of taking images of hot plasma in the 5-15 MK range. We find that there are hot structures above flare loops, and that they are typically more diffuse and nebulous than the well-defined flare loops. Because of the narrowband response, high sensitivity, and high spatial resolution of AIA, these supra-arcade structures are visible in exquisite detail, particularly in the 131 Å and 94 Å channels. In one event, a C4.9 flare observed on 2010 November 3, hot plasma is seen to outline an erupting plasmoid and possibly a current sheet. We compare hot plasma observed with AIA to structures observed with the X-Ray Telescope on the Hinode mission and find that the plasma imaged in AIA contains more fine detail. These new AIA observations show that supra-arcade flare structures and coronal mass ejections are highly structured not only in space and time, but also in temperature. This thermal structuring is expected, based on modeling efforts, but has now been imaged directly for the first time over a large range of temperatures. Title: Flares and Their Underlying Magnetic Complexity Authors: Engell, Alexander J.; Siarkowski, Marek; Gryciuk, Magda; Sylwester, Janusz; Sylwester, Barbara; Golub, Leon; Korreck, Kelly; Cirtain, Jonathan Bibcode: 2011ApJ...726...12E Altcode: SphinX (Solar PHotometer IN X-rays), a full-disk-integrated spectrometer, observed 137 flare-like/transient events with active region (AR) 11024 being the only AR on disk. The Hinode X-Ray Telescope (XRT) and Solar Optical Telescope observe 67 of these events and identified their location from 12:00 UT on July 3 through 24:00 UT 2009 July 7. We find that the predominant mechanisms for flares observed by XRT are (1) flux cancellation and (2) the shearing of underlying magnetic elements. Point- and cusp-like flare morphologies seen by XRT all occur in a magnetic environment where one polarity is impeded by the opposite polarity and vice versa, forcing the flux cancellation process. The shearing is either caused by flux emergence at the center of the AR and separation of polarities along a neutral line or by individual magnetic elements having a rotational motion. Both mechanisms are observed to contribute to single- and multiple-loop flares. We observe that most loop flares occur along a large portion of a polarity inversion line. Point- and cusp-like flares become more infrequent as the AR becomes organized with separation of the positive and negative polarities. SphinX, which allows us to identify when these flares occur, provides us with a statistically significant temperature and emission scaling law for A and B class flares: EM = 6.1 × 1033 T 1.9±0.1. Title: Comparison of simulated and observed loop-top emission in flares using the AIA telescopes on SDO Authors: Engell, A.; Reeves, K. K.; Ji, L.; Deluca, E. E.; Smith, R.; Golub, L. Bibcode: 2010AGUFMSH11A1596E Altcode: We investigate the spatial and temporal behavior of emission in flaring loops observed by AIA's 193 (Fe XXIV/XII), 131(Fe XX), 094 (Fe XVIII), 335 (Fe XVI), 211 (Fe XIV), and 171 (Fe IX) channels for two C class flares and one M class flare. Plotting light curves from loop-top areas in the six channels reveals the temporal distributions as a function of the ionization stages, with the same characteristic behavior identifiable in all three flares. The order of appearance is from the highest ionization state (FeXXIV) to the lowest (Fe XVI), and the observations are compared with the Reeves, Warren & Forbes (2007) model of flare loop energization, calculated for the various AIA channels. We also model the effects of non-equilibrium ionization on the simulated light curves. Title: The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) Authors: Golub, L.; Cirtain, J. W.; Kobayashi, K.; Winebarger, A. R.; Korreck, K. E.; Testa, P. Bibcode: 2010AGUFMSH11B1631G Altcode: We present a novel design for a stigmatic grazing incidence X-ray spectrograph for flight on a NASA sounding rocket. MaGIXS is comprised of a Wolter I telescope, a slit, a pair of parabolic mirrors, a plano variable line-spaced grating and a CCD detector. This design and layout have been optimized to produce an optical system with peak effective area of 5 mm^2, a wavelength range of 0.6-2.4 nm, spectral resolution of 2.0 pm, and spatial pixels of 2.5 arcsec along a 5 arcminute slit. The resulting instrument will resolve the solar spectrum for features in the solar corona with a two orders of magnitude increase over previous soft x-ray spectrographs in spatial and spectral resolution. Title: Multi-stranded and Multi-thermal Solar Coronal Loops: Evidence from Hinode X-ray Telescope and EUV Imaging Spectrometer Data Authors: Schmelz, J. T.; Saar, S. H.; Nasraoui, K.; Kashyap, V. L.; Weber, M. A.; DeLuca, E. E.; Golub, L. Bibcode: 2010ApJ...723.1180S Altcode: Data from the X-Ray Telescope (XRT) and the EUV Imaging Spectrometer (EIS) on the Japanese/USA/UK Hinode spacecraft were used to investigate the spatial and thermal properties of an isolated quiescent coronal loop. We constructed differential emission measure (DEM) curves using Monte Carlo based, iterative forward fitting algorithms. We studied the loop as a whole, in segments, in transverse cuts, and point-by-point, always with some form of background subtraction, and find that the loop DEM is neither isothermal nor extremely broad, with approximately 96% of the EM between 6.2 <=log T<= 6.7, and an EM-weighted temperature of log T = 6.48 ± 0.16. We find evidence for a gradual change in temperature along the loop, with log T increasing only by ≈0.1 from the footpoints to the peak. The combine XRT-EIS data set does a good job of constraining the temperature distribution for coronal loop plasma. Our studies show that the strong constraints at high and low temperatures provided by the combined data set are crucial for obtaining reasonable solutions. These results confirm that the observations of at least some loops are not consistent with isothermal plasma, and therefore cannot be modeled with a single flux tube and must be multi-stranded. Title: The Role of Magnetic Topology in the Heating of Active Region Coronal Loops Authors: Lee, J. -Y.; Barnes, Graham; Leka, K. D.; Reeves, Katharine K.; Korreck, K. E.; Golub, L.; DeLuca, E. E. Bibcode: 2010ApJ...723.1493L Altcode: 2010arXiv1009.2070L We investigate the evolution of coronal loop emission in the context of the coronal magnetic field topology. New modeling techniques allow us to investigate the magnetic field structure and energy release in active regions (ARs). Using these models and high-resolution multi-wavelength coronal observations from the Transition Region and Coronal Explorer and the X-ray Telescope on Hinode, we are able to establish a relationship between the light curves of coronal loops and their associated magnetic topologies for NOAA AR 10963. We examine loops that show both transient and steady emission, and we find that loops that show many transient brightenings are located in domains associated with a high number of separators. This topology provides an environment for continual impulsive heating events through magnetic reconnection at the separators. A loop with relatively constant X-ray and EUV emission, on the other hand, is located in domains that are not associated with separators. This result implies that larger-scale magnetic field reconnections are not involved in heating plasma in these regions, and the heating in these loops must come from another mechanism, such as small-scale reconnections (i.e., nanoflares) or wave heating. Additionally, we find that loops that undergo repeated transient brightenings are associated with separators that have enhanced free energy. In contrast, we find one case of an isolated transient brightening that seems to be associated with separators with a smaller free energy. Title: Statistical Study of Coronal Mass Ejections With and Without Distinct Low Coronal Signatures Authors: Ma, S.; Attrill, G. D. R.; Golub, L.; Lin, J. Bibcode: 2010ApJ...722..289M Altcode: Taking advantage of the two viewpoints of the STEREO spacecraft, we present a statistical study of coronal mass ejections (CMEs) with and without distinct low coronal signatures (LCSs) from 2009 January 1 to August 31. During this period, the lines of sight from STEREO A and B are almost perpendicular and nearly a quarter of the Sun was observed by both. We identified 34 CMEs that originated from around this area and find that (1) about 1 out of 3 CMEs that were studied during 8 months of solar minimum activity are stealth CMEs; a CME is stealth if no distinct LCS (such as coronal dimming, coronal wave, filament eruption, flare, post-eruptive arcade) can be found on the disk. (2) The speeds of the stealth CMEs without LCSs are typically below 300 km s-1. Comparing with the slow CMEs with LCSs, the stealth CMEs did not show any clear differences in their velocity and acceleration evolution. (3) The source regions of the stealth CMEs are usually located in the quiet Sun rather than active regions. Detailed study indicates that more than half of the stealth CMEs in this paper showed some faint change of the coronal structures (likely parts of flux ropes) when they could be observed over the solar limb before or during the CME evolution. Finally, we note that space weather detection systems based on LCSs totally independent of coronagraph data may fail to detect a significant proportion of CMEs. Title: Structure and Dynamics of Quiescent Filament Channels Observed by Hinode/XRT and STEREO/EUVI Authors: Su, Yingna; van Ballegooijen, Adriaan; Golub, Leon Bibcode: 2010ApJ...721..901S Altcode: We present a study of the structure and dynamics of quiescent filament channels observed by Hinode/XRT and STEREO/EUVI at the solar minimum 23/24 from 2006 November to 2008 December. For 12 channels identified on the solar disk (Group I channels), we find that the morphology of the structure on the two sides of the channel is asymmetric in both X-rays and EUV: the eastern side has curved features while the western side has straight features. We interpret the results in terms of a magnetic flux rope model. The asymmetry in the morphology is due to the variation in axial flux of the flux rope along the channel, which causes the field lines from one polarity to turn into the flux rope (curved feature), while the field lines from the other polarity are connected to very distant sources (straight). For most of the 68 channels identified by cavities at the east and west limbs (Group II channels), the asymmetry cannot be clearly identified, which is likely due to the fact that the axial flux may be relatively constant along such channels. Corresponding cavities are identified only for 5 of the 12 Group I channels, while Group II channels are identified for all of the 68 cavity pairs. The studied filament channels are often observed as dark channels in X-rays and EUV. Sheared loops within Group I channels are often seen in X-rays, but are rarely seen in Group II channels as shown in the X-ray Telescope daily synoptic observations. A survey of the dynamics of studied filament channels shows that filament eruptions occur at an average rate of 1.4 filament eruptions per channel per solar rotation. Title: Structure and Dynamics of Quiescent Filament Channels Observed by Hinode/XRT and STEREO/EUVI Authors: Su, Yingna; van Ballegooijen, Adriaan; Golub, Leon Bibcode: 2010shin.confE..83S Altcode: We present a study on the structure and dynamics of quiescent filament channels observed by Hinode/XRT and STEREO/EUVI at the solar minimum 23/24 from December 2006 to December 2008. For 12 channels identified on the solar disk (Group I channels), we find that the emission on the two sides of the channel is asymmetric in both X-rays and EUV: eastern side has curved features while the western side has straight features. We interpret the results in terms of a magnetic flux rope model. The asymmetry in the emission is due to the variation in axial magnetic flux along the channel, which causes the field lines from one polarity to turn into the flux rope, while the field lines from the other polarity are connected to very distant sources. For 67 channels identified by cavities at the east and west limbs (Group II channels), the asymmetry cannot be clearly identified, which is likely due to the fact that these channels are nearly parallel to the equator and the axial flux may be relatively constant along such channels. Corresponding cavities are identified only for 5 of the 12 Group I channels, while Group II channels are identified for all of the 68 cavity pairs. The studied filament channels are often observed as dark channels in X-rays and EUV. Sheared loops within Group I channels are often seen in X-rays, but are rarely seen in Group II channels as shown in the XRT daily synoptic observations. A survey on the dynamics of studied filament channels shows that filament eruptions occur at an average rate of 1.4 filament eruptions per channel per solar rotation. Title: Flare Energy Build-Up in a Decaying Active Region Near a Coronal Hole Authors: Su, Yingna; van Ballegooijen, Adriaan; Schmieder, Brigitte; Berlicki, Arkadiusz; Guo, Yang; Golub, Leon; Huang, Guangli Bibcode: 2010shin.confE.131S Altcode: A B1.7 two-ribbon flare occurred in a highly non-potential decaying active region near a coronal hole at 10:00 UT on May 17, 2008. This flare is large in the sense that it involves the entire region, and it is associated with both a filament eruption and a CME. We present multi-wavelength observations from EUV (TRACE, STEREO/EUVI), X-rays (Hinode/XRT), and H-alpha (THEMIS, BBSO) prior to, during and after the flare. Prior to the flare, the region contained two filaments. The long J-shaped sheared loops corresponding to the southern filament were evolved from two short loop systems, which happened around 22:00 UT after a filament eruption on May 16. Formation of highly sheared loops in the south eastern part of the region was observed by STEREO 8 hours before the flare. We also perform non-linear force free field (NLFFF) modeling for the region at two times prior to the flare, using the flux rope insertion method. The models include the non-force-free effect of magnetic buoyancy in the photosphere. The best-fit NLFFF models show good fit to observations both in the corona (X-ray and EUV loops) and chromosphere (H-alpha filament). We find that the horizontal fields in the photosphere are relatively insensitive to the present of flux ropes in the corona. The axial flux of the flux rope in the NLFFF model on May 17 is twice that on May 16, and the model on May 17 is only marginally stable. We also find that the quasi-circular flare ribbons are associated with the separatrix between open and closed fields. This observation and NLFFF modeling suggest that this flare may be triggered by the reconnection at the null point on the separatrix surface. Title: Stigmatic grazing-incidence x-ray spectrograph for solar coronal observations Authors: Kobayashi, Ken; Cirtain, Jonathan; Golub, Leon; Korreck, Kelly; Cheimets, Peter; Hertz, Edward; Caldwell, David Bibcode: 2010SPIE.7732E..33K Altcode: 2010SPIE.7732E..98K We present the design for a stigmatic grazing incidence X-ray spectrograph designed for solar coronal observations. The spectrograph is composed of a slit, a pair of paraboloid mirrors and a plano varied-line-space grating. All reflective surfaces of the spectrograph operate at an angle of incidence of 88 degrees, and covers a wavelength range of 0.6 to 2.4nm (0.5 to 2.0keV). The design achieves 1.5pm spectral resolution and 15 μm spatial resolution over a 2.5mmlong slit. The current spectrograph design is intended for a sounding rocket experiment, and designed to fit inside a NASA sounding rocket payload behind a 1.1m focal length Wolter Type-1 telescope. This combination will have a 2.5arcsec spatial resolution and a 8 arcminute slit length. We are currently fabricating a laboratory prototype of the spectrograph to demonstrate the performance and establish the alignment procedures for a flight model. Title: Coronal Loop Evolution and Inferred Coronal Magnetic Energy in a Quiet Active Region Authors: Lee, Jin-Yi; Barnes, G.; Leka, K.; Reeves, K. K.; Korreck, K. E.; Golub, L. Bibcode: 2010AAS...21640514L Altcode: 2010BAAS...41R.891L We investigate changes in the properties of the coronal magnetic field in the context of different emission of coronal loops. Observations by the Transition Region and Coronal Explorer (TRACE), the Hinode/X-ray Telescope (XRT), and the SOHO/Michelson Doppler Imager (MDI), the X-ray and EUV light curves as well as the photospheric magnetic flux of NOAA active region 10963 are utilized to compare the coronal and photospheric magnetic fields. A Magnetic Charge Topology (MCT) model is used to establish potential magnetic field connectivity of the surface magnetic flux distribution. A Minimum Current Corona (MCC) model is applied to determine the coronal currents and quantify the energy build-up. The results of the MCC analysis are compared to the evolution of the coronal loop brightness, comparing areas of steady emission, transient emission, and temporal patterns of emission which imply coronal cooling. Title: Asymmetric Structure of Quiescent Filament Channels Observed by Hinode/XRT and STEREO/EUVI Authors: Su, Yingna; van Ballegooijen, A.; Golub, L. Bibcode: 2010AAS...21640513S Altcode: 2010BAAS...41..891S We present a study on the structure of quiescent filament channels observed by Hinode/XRT and STEREO/EUVI from December 2006 to February 2009. For 10 channels identified on the solar disk, we find that the emission on the two sides of the channel is asymmetric in both X-rays and EUV: one side has curved bright features while the other side has straight faint features. We interpret the results in terms of a magnetic flux rope model. The asymmetry in the emission is due to the variation in axial magnetic flux along the channel, which causes one polarity to turn into the flux rope, while the field lines from the other polarity are open or connected to very distant sources. For 70 channels identified by cavities at the limb, the asymmetry cannot be clearly identified. US members of the XRT team are supported by NASA contract NNM07AB07C to Smithsonian Astrophysical Observatory. Title: Statistical Study of CMEs with and without Distinct Low Coronal Signatures Authors: Ma, Suli; Attrill, G. D. R.; Golub, L.; Lin, J.; Wills-Davey, M. J. Bibcode: 2010AAS...21640804M Altcode: 2010BAAS...41R.816M Taking advantage of the two viewpoints of the STEREO spacecraft, we present a statistical study of CMEs with and without distinct low coronal signatures from January 1st to August 31st, 2009. During this period, the line of sight of STEREO A and that of STEREO B are almost perpendicular and nearly a quarter of the Sun was observed by both. We identified 35 front-side (as viewed from Earth) CMEs, around half of which had no distinct low coronal signature (such as dimming, coronal wave, filament eruption, post-eruptive arcade). Study of the CME kinematics showed that in the COR2 field of view there is no obvious difference between CMEs with and without low coronal signatures. The data from COR1 and EUVI suggest that both kinds of CMEs originate from below 1.4Rsun. We conclude that the region between 1.1-1.4Rsun is very important for understanding the nascent development of CMEs. Detailed study indicates that although there may be no major low coronal signatures for half of the CMEs, there still exist some subtle changes in the low corona before or during the CME appearance. Finally, this work acknowledges that automatic space weather detection systems based on low coronal signatures totally independent of coronagraph data, may fail to detect a significant proportion of CMEs. Title: Coronal Fine Linear Rays: Are They Fast Streams From Active Regions? Authors: Koutchmy, Serge; Lamy, Philippe; Viladrich, Christian; Filippov, Boris; Nikoghossian, Arthur; Golub, Leon Bibcode: 2010AIPC.1216..339K Altcode: Eclipse observations of the W-L corona show linear rays above active regions at times of solar maximum. We show that these linear rays are also observed in the field-of-view of the C2-LASCO coronagraph, in perfect correspondence with the eclipse results. A selected prominent case taken from the 2001 eclipse observation in Angola is analysed with several different methods, including the use of a synoptic map constructed using SoHO/LASCO C2 images. A clear signature of time variations near the eclipse observation is detected, suggesting that at least some parts of the beam are collimated. These observations strongly suggest high speed streams that apparently ignore the potential large scale coronal magnetic field rooted rather low in the corona. A possible origin is the neutral magnetic points located above the active region. Several mechanisms exist to explain how the plasma is accelerated in these regions to large quasi-relativistic velocities, possibly related to the occurrence of type III radio bursts. We point out a curious analogy with phenomena occurring inside coronal holes. Title: Is there a flare-like precursor of EUV waves and CMEs ? Authors: Filippov, Boris; Podladhikova, Olena; Golub, Leon; Koutchmy, Serge Bibcode: 2010cosp...38.2889F Altcode: 2010cosp.meet.2889F Filament eruptions with a flux rope are usually considered the cause of CMEs. It is however not clear why after reaching some critical height, the filament suddenly erupts and whether or not we always have a one to one correspondence. Additional factors can be considered, starting with the ubiquitous chromospheric (in H) and/or coronal running disturbances or waves seen with EUV and SXR filtergrams collected by different missions, including the newly operated SWAP of Proba-2, the GOES 14 SXR patrol instrument and the high resolution XRT of Hinode. The eruptions seem to be induced by a well focused but large explosive event originating from an unresolved region presumably situated rather low in the atmosphere, near the chromosphere-corona interface. A similar picture can be drawn from a new type of coronal flare observed with the XRT of Hinode outside of any active region and without any precursor. Both the quasi-thermal coronal flare and the large dynamical phenomenon originate or start from a very small unresolved region. We discuss the difference in mass, momentum and amount of energy involved for 2 selected events (25 Dec 2006 with XRT and 5 Feb 2010 with SWAP and other instruments) that are well documented. We want to examine at what height in the atmosphere these events are triggered and what is the relevance to the CME phenomenon, without speculating on the unresolved magnetic field context. The events were observed at solar activity minimum without any complication resulting from numerous active regions being present on the disk. Title: Modeling Twisted Coronal Loops: AR 10938 Authors: Golub, L.; Engell, A. J.; van Ballegooijen, A. A.; Korreck, K. E.; Reeves, K. K. Bibcode: 2009ASPC..415..268G Altcode: When modeling coronal loops by calculating the potential field from magnetograms it is often found that field lines highlighted of the potential field do not match the coronal loops observed in the data. To rectify this situation, we construct a non-potential field in which helical ``twisted'' currents with prescribed radii are inserted along certain potential field lines. We then relax the magnetic field to a non-linear force-free field (NLFFF) using magneto-frictional relaxation. In doing so, we find that we are able to approach a geometrical match between the field lines and the coronal loops observed in AR 10938 on January 18, 2007. Title: Jet phenomena above null points of the coronal magnetic field Authors: Filippov, B.; Koutchmy, S.; Golub, L. Bibcode: 2009Ge&Ae..49.1109F Altcode: Short-lived plasma jets of various scales, from giant X-ray jets more than 300 Mm in extent to numerous small jets with sizes typical of macrospicules, are the phenomena observed in the solar corona in extreme ultraviolet and X-ray emission. Small jets are particularly prominent in polar coronal holes. They are close neighbors of tiny bright loops and coincide in time with their sudden brightening and increase in size. The geometric shape of the jets and their location suggest that they arise near singular null points of the coronal magnetic field. These points appear in coronal holes due to the emergence of small bipolar or unipolar magnetic structures within large-scale unipolar cells. Polar jets show a distinct vertical plasma motion in a coronal hole that introduces significant momentum and mass into the solar wind flow. Investigating the dynamics of polar jets can elucidate certain details in the problem of fast solar wind acceleration. Title: EUV Solar Instrument Development at the Marshall Space Flight Center Authors: Kobayashi, K.; Cirtain, J. W.; Davis, J. M.; West, E.; Golub, L.; Korreck, K. E.; Tsuneta, S.; Bando, T. Bibcode: 2009AGUFMSH33B1500K Altcode: The three sounding rocket instrument programs currently underway at the NASA Marshall Space Flight Center represent major advances in solar observations, made possible by improvements in EUV optics and detector technology. The Solar Ultraviolet Magnetograph Instrument (SUMI) is an EUV spectropolarimeter designed to measure the Zeeman splitting of two chromospheric EUV lines, the 280 nm MgII and 155 nm CIV lines. SUMI directly observes the magnetic field in the low-beta region where most energetic phenomena are though to originate. In conjunction with visible-light magnetographs, this observation allows us to track the evolution of the magnetic field as it evolves from the photosphere to the upper chromosphere. SUMI incorporates a normal incidence Cassegrain telescope, a MgF2 double-Wollaston polarizing beam splitter and two TVLS (toroidal varied line space) gratings, and is capable of observing two orthogonal polarizations in two wavelength bands simultaneously. SUMI has been fully assembled and tested, and currently scheduled for launch in summer of 2010. The High-resolution Coronal Imager is a normal-incidence EUV imaging telescope designed to achieve 0.2 arcsecond resolution, with a pixel size of 0.1 arcsecond. This is a factor of 25 improvement in aerial resolution over the Transition Region And Coronal Explorer (TRACE). Images obtained by TRACE indicate presence of unresolved structures; higher resolution images will reveal the scale and topology of structures that make up the corona. The telescope mirrors are currently being fabricated, and the instrument has been funded for flight. In addition, a Lyman alpha spectropolarimeter is under development in collaboration with the National Astronomical Observatory of Japan. This aims to detect the linear polarization in the chromosphere caused by the Hanle effect. Horizontal magnetic fields in the chromosphere are expected to be detectable as polarization near disk center, and off-limb observations will reveal the magnetic field structure of filaments and prominences. Laboratory tests of candidate optical components are currently underway. Title: The Interface Region Imaging Spectrograph (IRIS) Small Explorer Authors: de Pontieu, B.; Title, A. M.; Schryver, C. J.; Lemen, J. R.; Golub, L.; Kankelborg, C. C.; Carlsson, M. Bibcode: 2009AGUFMSH33B1499D Altcode: The Interface Region Imaging Spectrograph (IRIS) was recently selected as a small explorer mission by NASA. The primary goal of IRIS is to understand how the solar atmosphere is energized. The IRIS investigation combines advanced numerical modeling with a high resolution 20 cm UV imaging spectrograph that will obtain spectra covering temperatures from 4,500 to 10 MK in three wavelength ranges (1332-1358 Angstrom, 1390-1406 Angstrom and 2785-2835 Angstrom) and simultaneous images covering temperatures from 4,500 K to 65,000 K. IRIS will obtain UV spectra and images with high resolution in space (1/3 arcsec) and time (1s) focused on the chromosphere and transition region of the Sun, a complex dynamic interface region between the photosphere and corona. In this region, all but a few percent of the non-radiative energy leaving the Sun is converted into heat and radiation. IRIS fills a crucial gap in our ability to advance Sun-Earth connection studies by tracing the flow of energy and plasma through this foundation of the corona and heliosphere. The IRIS investigation is led by PI Alan Title (LMSAL) with major participation by the Harvard Smithsonian Astrophysical Observatory, Montana State University, NASA Ames Research Center, Stanford University and the University of Oslo (Norway). IRIS is scheduled for launch in late 2012, and will have a nominal two year mission lifetime. Title: A New View of Coronal Waves from STEREO Authors: Ma, S.; Wills-Davey, M. J.; Lin, J.; Chen, P. F.; Attrill, G. D. R.; Chen, H.; Zhao, S.; Li, Q.; Golub, L. Bibcode: 2009ApJ...707..503M Altcode: On 2007 December 7, there was an eruption from AR 10977, which also hosted a sigmoid. An EUV Imaging Telescope (EIT) wave associated with this eruption was observed by EUVI on board the Solar Terrestrial Relations Observatory (STEREO). Using EUVI images in the 171 Å and the 195 Å passbands from both STEREO A and B, we study the morphology and kinematics of this EIT wave. In the early stages, images of the EIT wave from the two STEREO spacecrafts differ markedly. We determine that the EUV fronts observed at the very beginning of the eruption likely include some intensity contribution from the associated coronal mass ejection (CME). Additionally, our velocity measurements suggest that the EIT wave front may propagate at nearly constant velocity. Both results offer constraints on current models and understanding of EIT waves. Title: Evolution of Magnetic Properties for Two Active Regions Observed by Hinode/XRT and TRACE Authors: Lee, J. -Y.; Leka, K. D.; Barnes, G.; Reeves, K. K.; Korreck, K. E.; Golub, L. Bibcode: 2009ASPC..415..279L Altcode: We investigate two active regions observed by the Hinode X-ray Telescope (XRT) and the Transition Region and Coronal Explorer (TRACE). One active region shows constant brightness in both XRT and TRACE observations. The other active region shows a brightening in the TRACE observation just after a decrease in X-ray brightness indicating the cooling of a coronal loop. The coronal magnetic topology is derived using a magnetic charge topology (MCT) model for these two active regions applied to magnetograms from the Michelson Doppler Imager (MDI) on board the Solar and Heliospheric Observatory (SOHO). We discuss the results of the MCT analysis with respect to the light curves for these two active regions. Title: Magnetic energy build-up and coronal brightness evolution Authors: Lee, J.; Barnes, G.; Leka, K. D.; Reeves, K. K.; Korreck, K. E.; Golub, L. Bibcode: 2009AGUFMSH41B1664L Altcode: We have investigated changes in the properties of the coronal magnetic field in the context of different emission behaviors of coronal loops. Using observations by the Transition Region and Coronal Explorer (TRACE), the Hinode/X-ray Telescope (XRT), and the SoHO/Michelson Doppler Imager (MDI), NOAA active region 10963 has been analyzed in depth as to how different coronal signatures compare to inferred coronal energy build-up. A Magnetic Charge Topology (MCT) model was used to establish potential magnetic field connectivity of the surface magnetic flux distribution, and a Minimum Current Corona (MCC) model was applied to quantify the energy build-up along separator field lines. The results of the MCC analysis are compared to the evolution of the coronal brightness, comparing areas of steady emission, very transient emission, and temporal patterns of emission which imply coronal cooling. Title: Coronal Loop Temperatures Obtained with Hinode XRT: A Toothpaste-Tube Analogy Authors: Schmelz, J. T.; Saar, S. H.; Weber, M. A.; Deluca, E. E.; Golub, L. Bibcode: 2009ASPC..415..299S Altcode: Multi-filter data observed by the Hinode X-Ray Telescope on 10 and 2007 July 13 were used to investigate the thermal properties of coronal loops. At several positions along the loops, differential emission measure analysis revealed a strong peak at log T = 6.1 (which would predict the presence of a TRACE loop) and a much weaker hot component (which we speculated might be a nanoflare signature). TRACE observations, however, did not reveal the predicted loop, so we were forced to re-examine our assumptions. Good differential emission measure results require high- and low-temperature constraints, but our data sets did not contain images from the thinnest and thickest filters, which would be most likely to provide these constraints. Since differential emission measure programs aim to match observed intensities and get low values of χ2, they may place emission measure in high- and low-temperature bins where it does not belong. We draw an analogy to squeezing the toothpaste tube in the middle. Our analysis was repeated for a loop observed on 2007 May 13 when the instrument acquired data in 11 filters and filter combinations, including both the thinnest and thickest filters. These results show that the loop is multi-thermal, with significant emission measure in the range 6.0 < log T < 6.5. Title: A Vigorous Explorer Program Authors: Elvis, Martin; Beasley, Matthew; Brissenden, Roger; Chakrabarti, Supriya; Cherry, Michael; Devlin, Mark; Edelstein, Jerry; Eisenhardt, Peter; Feldman, Paul; Ford, Holland; Gehrels, Neil; Golub, Leon; Marshall, Herman; Martin, Christopher; Mather, John; McCandliss, Stephan; McConnell, Mark; McDowell, Jonathan; Meier, David; Millan, Robyn; Mitchell, John; Moos, Warren; Murray, Steven S.; Nousek, John; Oegerle, William; Ramsey, Brian; Green, James; Grindlay, Jonathan; Kaaret, Philip; Kaiser, Mary Elizabeth; Kaltenegger, Lisa; Kasper, Justin; Krolik, Julian; Kruk, Jeffrey W.; Latham, David; MacKenty, John; Mainzer, Amanda; Ricker, George; Rinehart, Stephen; Romaine, Suzanne; Scowen, Paul; Silver, Eric; Sonneborn, George; Stern, Daniel; Swain, Mark; Swank, Jean; Traub, Wesley; Weisskopf, Martin; Werner, Michael; Wright, Edward Bibcode: 2009arXiv0911.3383E Altcode: Explorers have made breakthroughs in many fields of astrophysics. The science from both these missions contributed to three Nobel Prizes - Giacconi (2002), Mather, and Smoot (2006). Explorers have: marked the definitive beginning of precision cosmology, discovered that short gamma-ray bursts are caused by compact star mergers and have measured metalicity to redshifts z>6. NASA Explorers do cutting-edge science that cannot be done by facility-class instruments. The Explorer program provides a rapid response to changing science and technology, to enable cutting-edge science at moderate cost. Explorers also enable innovation, and engage & train scientists, managers and engineers, adding human capital to NASA and the nation. The astrophysics Explorer launch rate now being achieved is 1 per 3 years, and budget projections are in the $150M/year range for the next five years. A newly Vigorous Explorer Program should be created to: 1. Reach the long-stated goal of annual astrophysics launches; 2. Find additional launch options for Explorers and actively encourage cost savings in launchers and spacecraft, such as new commercial vehicles and innovative partnerships. 3. Mitigate risk via stronger technical development and sub-orbital programs, and through longer, more thorough, Phase A programs, potentially reducing the need for a 30% contingency; 4. Strive to protect the funding for missions that have reached Phase B, to prevent significant launch slips and cancellations, with a goal of 4 to 5 years from Phase B to launch; 5. Review the project management procedures and requirements to seek cost reductions, including the risk management strategy and the review and reporting process; 6. Review and possibly modify the cost caps for all Explorer classes to optimize scientific returns per dollar. [ABRIDGED] Title: Flare Energy Build-up in a Decaying Active Region Near a Coronal Hole Authors: Su, Yingna; van Ballegooijen, Adriaan; Schmieder, Brigitte; Berlicki, Arkadiusz; Guo, Yang; Golub, Leon; Huang, Guangli Bibcode: 2009ApJ...704..341S Altcode: A B1.7 two-ribbon flare occurred in a highly non-potential decaying active region near a coronal hole at 10:00 UT on 2008 May 17. This flare is "large" in the sense that it involves the entire region, and it is associated with both a filament eruption and a coronal mass ejection. We present multi-wavelength observations from EUV (TRACE, STEREO/EUVI), X-rays (Hinode/XRT), and Hα (THEMIS, BBSO) prior to, during and after the flare. Prior to the flare, the region contained two filaments. The long J-shaped sheared loops corresponding to the southern filament were evolved from two short loop systems, which happened around 22:00 UT after a filament eruption on May 16. Formation of highly sheared loops in the southeastern part of the region was observed by STEREO 8 hr before the flare. We also perform nonlinear force-free field (NLFFF) modeling for the region at two times prior to the flare, using the flux rope insertion method. The models include the non-force-free effect of magnetic buoyancy in the photosphere. The best-fit NLFFF models show good fit to observations both in the corona (X-ray and EUV loops) and chromosphere (Hα filament). We find that the horizontal fields in the photosphere are relatively insensitive to the present of flux ropes in the corona. The axial flux of the flux rope in the NLFFF model on May 17 is twice that on May 16, and the model on May 17 is only marginally stable. We also find that the quasi-circular flare ribbons are associated with the separatrix between open and closed fields. This observation and NLFFF modeling suggest that this flare may be triggered by the reconnection at the null point on the separatrix surface. Title: Some Like It Hot: Coronal Heating Observations from Hinode X-ray Telescope and RHESSI Authors: Schmelz, J. T.; Kashyap, V. L.; Saar, S. H.; Dennis, B. R.; Grigis, P. C.; Lin, L.; De Luca, E. E.; Holman, G. D.; Golub, L.; Weber, M. A. Bibcode: 2009ApJ...704..863S Altcode: We have used Hinode X-Ray Telescope observations and RHESSI upper limits together to characterize the differential emission measure (DEM) from a quiescent active region. We find a relatively smooth DEM curve with the expected active region peak at log T = 6.4. We also find a high-temperature component with significant emission measure at log T gsim 7. This curve is consistent with previous observations of quiescent active regions in that it does not produce observable Fe XIX lines. It is different from that generated with X-Ray Telescope (XRT) data alone—RHESSI rules out the possibility of a separate high-temperature component with a peak of approximately log T = 7.4. The strength and position of the high-temperature peak in this XRT-only analysis was, however, poorly determined; adding RHESSI flux upper limits in the 4-13 keV energy range provide a strong high-temperature constraint which greatly improves the multi-thermal findings. The results of the present work as well as those from a growing number of papers on this subject imply that our previous understanding of the temperature distribution in active regions has been limited. Hot plasma (log T ≈ 7) appears to be prevalent, although in relatively small quantities as predicted by nanoflare models. Other models may need to be adjusted or updated to account for these new results. Title: Fan-Spine Topology Formation Through Two-Step Reconnection Driven by Twisted Flux Emergence Authors: Török, T.; Aulanier, G.; Schmieder, B.; Reeves, K. K.; Golub, L. Bibcode: 2009ApJ...704..485T Altcode: 2009arXiv0909.2235T We address the formation of three-dimensional nullpoint topologies in the solar corona by combining Hinode/X-ray Telescope (XRT) observations of a small dynamic limb event, which occurred beside a non-erupting prominence cavity, with a three-dimensional (3D) zero-β magnetohydrodynamics (MHD) simulation. To this end, we model the boundary-driven "kinematic" emergence of a compact, intense, and uniformly twisted flux tube into a potential field arcade that overlies a weakly twisted coronal flux rope. The expansion of the emerging flux in the corona gives rise to the formation of a nullpoint at the interface of the emerging and the pre-existing fields. We unveil a two-step reconnection process at the nullpoint that eventually yields the formation of a broad 3D fan-spine configuration above the emerging bipole. The first reconnection involves emerging fields and a set of large-scale arcade field lines. It results in the launch of a torsional MHD wave that propagates along the arcades, and in the formation of a sheared loop system on one side of the emerging flux. The second reconnection occurs between these newly formed loops and remote arcade fields, and yields the formation of a second loop system on the opposite side of the emerging flux. The two loop systems collectively display an anenome pattern that is located below the fan surface. The flux that surrounds the inner spine field line of the nullpoint retains a fraction of the emerged twist, while the remaining twist is evacuated along the reconnected arcades. The nature and timing of the features which occur in the simulation do qualititatively reproduce those observed by XRT in the particular event studied in this paper. Moreover, the two-step reconnection process suggests a new consistent and generic model for the formation of anemone regions in the solar corona. Title: The Solar Corona Authors: Golub, Leon; Pasachoff, Jay M. Bibcode: 2009soco.book.....G Altcode: 1. Introduction; 2. Brief history of coronal studies; 3. The coronal spectrum; 4. The solar cycle; 5. Ground-based observations; 6. Observations from space: I. The first 4 decades; 7. Activity of the inner corona; 8. Observations from space: II. Recent missions; 9. The solar wind; 10. Solar flares and coronal mass ejections; Notes; References; Index. Title: Does a Polar Coronal Hole's Flux Emergence Follow a Hale-Like Law? Authors: Savcheva, A.; Cirtain, J. W.; DeLuca, E. E.; Golub, L. Bibcode: 2009ApJ...702L..32S Altcode: Recent increases in spatial and temporal resolution for solar telescopes sensitive to EUV and X-ray radiation have revealed the prevalence of transient jet events in polar coronal holes. Using data collected by the X-Ray Telescope on Hinode, Savcheva et al. confirmed the observation, made first by the Soft X-ray Telescope on Yohkoh, that some jets exhibit a motion transverse to the jet outflow direction. The velocity of this transverse motion is, on average, 10 km s-1. The direction of the transverse motion, in combination with the standard reconnection model for jet production (e.g., Shibata et al.), reflects the magnetic polarity orientation of the ephemeral active region at the base of the jet. From this signature, we find that during the present minimum phase of the solar cycle the jet-base ephemeral active regions in the polar coronal holes had a preferred east-west direction, and that this direction reversed during the cycle's progression through minimum. In late 2006 and early 2007, the preferred direction was that of the active regions of the coming sunspot cycle (cycle 24), but in late 2008 and early 2009 the preferred direction has been that of the active regions of sunspot cycle 25. These findings are consistent with the observations of Wilson et al. suggesting that each cycle of solar activity begins at polar latitudes soon after the onset of the previous cycle. Title: Magnetic Nonpotentiality Accumulation Prior to a "Large" B1.7 Two-Ribbon Flare Authors: Su, Yingna; van Ballegooijen, A.; Schmieder, B.; Berlicki, A.; Guo, Y.; Golub, L. Bibcode: 2009SPD....40.2002S Altcode: A B1.7 two-ribbon flare occurred in a highly non-potential decaying active region near a coronal hole at 10:00 UT on May 17, 2008. This flare is "large" in the sense that it involves the entire region, and it is associated with both a filament eruption and a CME. We present multi-wavelength observations from EUV (TRACE, STEREO/EUVI), X-rays (Hinode/XRT), and H-alpha (THEMIS, BBSO) prior to, during and after the flare. Prior to the flare, the observed coronal loops are mainly two sets of highly sheared loops surrounding two filaments. The sheared loops in the southern part of the region appeared in TRACE around 22:00 UT after a filament ejection on May 16. We also performed non-linear force free field (NLFFF) modeling for the region prior to the flare, using the flux rope insertion method. The model at 11:42 UT on May 16 is based on THEMIS (vector) and MDI magnetograms, and the model at 08:03 UT on May 17 is based only on MDI magnetogram. The best-fit NLFFF models show good fit to observations both in the corona (X-ray and EUV loops) and chromosphere (H-alpha filament). In the photosphere, the vectors in the best-fit NLFFF model are similar to those in the potential model. However, in the chromosphere, the vectors in the best-fit NLFFF model present strong non-potentiality, especially at the end of the inserted flux rope. We also found that the axial flux of the flux rope in the NLFFF model on May 17 is much higher than that on May 16. Title: The Off-Axis Properties of the Hinode X-Ray Telescope (XRT): I. Vignetting Effect Authors: Shin, Junho; Martens, P. C. H.; Golub, L.; Deluca, E. E. Bibcode: 2009SPD....40.1804S Altcode: The X-Ray Telescope (XRT) aboard Hinode has observed a variety of coronal structures in the range of 34x34 arc min field-of-view (FOV) covering the full solar disk. In general, most astronomical telescopes are designed such that the best-focused image of an object can be achieved at or close to the on-axis position, and the optical performance varies systematically across the FOV. The Sun is, however, a large object whose size is about 30 arc min and coronal structures are observed not only at the disc center but also near the limb. For this reason, the optical structure of solar telescopes should be designed with care for improving the uniformity of the angular resolution over the full FOV. Since there is no unique solution for successfully implementing this kind of off-axis variation, the optical properties of the XRT have been examined using the data from the ground experiments as well as from in-flight observations for the calibration of systematic variations in the FOV.

The vignetting effect is an important optical characteristic for describing the performance of the telescope, which reflects the ability to collect incoming light at different locations and different photon energies. Especially, the determination of this vignetting effect is one of the essential calibration steps that should be performed before the observed images are used for any scientific purposes. Because a component of the XRT vignetting effect shows a wavelength dependence, special care should be taken when, for example, performing temperature analyses with thin and thick filters of flares occurring near the solar limb. In this presentation, we introduce the results of analysis of pre-launch calibration data obtained from MSFC/XRCF experiments. The two-dimensional off-axis variation of the XRT point spread function (PSF) and its energy dependence will be discussed in detail. Title: Observations Of Filament Channels By Hinode/XRT And STEREO/EUVI Authors: Su, Yingna; van Ballegooijen, A.; Golub, L. Bibcode: 2009SPD....40.1013S Altcode: We will present preliminary results of an investigation on filament channels observed by Hinode/XRT and STEREO/EUVI. We selected 8 filament channels that are located in active region remnants. Filament channels 1, 2 and 3 appear to be the same channel observed at different solar rotations, and channels 5, 6, 7 and 8 are also the same channel at different solar rotations. We study the X-ray and EUV structures as well as the evolution of these channels observed by Hinode/XRT and STEREO/EUV. The corresponding H-alpha filament information is provided by KSO and MLSO. In order to understand the magnetic configuration of filament channels, we will also explore non-linear force-free field modeling of two selected filament channels. The modeling is based on flux rope insertion method, and the magnetic field information is provided by SOLIS. Title: Magnetic Topology and Coronal Brightness Evolution: A Case Study Authors: Lee, Jin-Yi; Barnes, G.; Leka, K.; Reeves, K. K.; Korreck, K. E.; Golub, L. Bibcode: 2009SPD....40.1209L Altcode: We have applied a Magnetic Charge Topology model to investigate what changes in the properties of the magnetic field are responsible for different coronal emission behavior of the coronal loops in two different active regions. Observations from the X-ray Telescope (XRT) on board Hinode and the Transition Region and Coronal Expolorer (TRACE) were used, along with time-series of magnetograms for 24 hours from the Michelson Doppler Imager (MDI) on board the Solar and Heliospheric Observatory (SOHO). The magnetic connectivity and separator field lines were established by potential field extrapolation of the observed surface magnetic flux distribution. We present the evolution for the two active regions in terms of the changes in both the connections and in the separator flux, the latter indicative of locations of possible energy deposit or release. Title: Hinode X-Ray Telescope Detection of Hot Emission from Quiescent Active Regions: A Nanoflare Signature? Authors: Schmelz, J. T.; Saar, S. H.; DeLuca, E. E.; Golub, L.; Kashyap, V. L.; Weber, M. A.; Klimchuk, J. A. Bibcode: 2009ApJ...693L.131S Altcode: 2009arXiv0901.3122S The X-Ray Telescope (XRT) on the Japanese/USA/UK Hinode (Solar-B) spacecraft has detected emission from a quiescent active region core that is consistent with nanoflare heating. The fluxes from 10 broadband X-ray filters and filter combinations were used to construct differential emission measure (DEM) curves. In addition to the expected active region peak at log T = 6.3-6.5, we find a high-temperature component with significant emission measure at log T > 7.0. This emission measure is weak compared to the main peak—the DEM is down by almost three orders of magnitude—which accounts of the fact that it has not been observed with earlier instruments. It is also consistent with spectra of quiescent active regions: no Fe XIX lines are observed in a CHIANTI synthetic spectrum generated using the XRT DEM distribution. The DEM result is successfully reproduced with a simple two-component nanoflare model. Title: X-Ray Jet Dynamics in a Polar Coronal Hole Region Authors: Filippov, Boris; Golub, Leon; Koutchmy, Serge Bibcode: 2009SoPh..254..259F Altcode: 2007arXiv0711.4320F New X-ray observations of the north polar region taken from the X-ray Telescope (XRT) of the Hinode spacecraft are used to analyze several time sequences showing small loop brightenings with a long ray above. We focus on the formation of the jet and discuss scenarios to explain the main features of the events: the relationship with the expected surface magnetism, the rapid and sudden radial motion, and possibly the heating, based on the assumption that the jet occurs above a null point of the coronal magnetic field. We conclude that 2-D reconnection models should be complemented in order to explain the observational details of these events and suggest that alternative scenarios may exist. Title: On the Structure and Evolution of Complexity in Sigmoids: A Flux Emergence Model Authors: Archontis, V.; Hood, A. W.; Savcheva, A.; Golub, L.; Deluca, E. Bibcode: 2009ApJ...691.1276A Altcode: Sigmoids are structures with a forward or inverse S-shape, generally observed in the solar corona in soft X-ray emission. It is believed that the appearance of a sigmoid in an active region is an important factor in eruptive activity. The association of sigmoids with dynamic phenomena such as flares and coronal mass ejections (CMEs) make the study of sigmoids important. Recent observations of a coronal sigmoid, obtained with the X-Ray Telescope (XRT) on board Hinode, showed the formation and eruption phase with high spatial resolution. These observations revealed that the topological structure of the sigmoid is complex: it consists of many differently oriented loops that all together form two opposite J-like bundles or an overall S-shaped structure. A series of theoretical and numerical models have been proposed, over the past years, to explain the nature of sigmoids but there is no explanation on how the aforementioned complexity in sigmoids is built up. In this paper, we present a flux emergence model that leads to the formation of a sigmoid, whose structure and evolution of complexity are in good qualitative agreement with the recent observations. For the initial state of the experiment a twisted flux tube is placed below the photosphere. A density deficit along the axis of the tube makes the system buoyant in the middle and it adopts an Ω-shape as it rises toward the outer atmosphere. During the evolution of the system, expanding field lines that touch the photosphere at bald-patches (BPs) form two seperatrix surfaces where dissipation is enhanced and current sheets are formed. Originally, each of the BP seperatrix surfaces has a J-like shape. Each one of the J's consist of reconnected field lines with different shapes and different relative orientation. The further dynamical evolution of the emerging flux tube results in the occurrence of many sites that resemble rotational discontinuities. Thus, additional current layers are formed inside the rising magnetized volume increasing the complexity of the system. The reconnected field lines along these layers form an overall S-shaped structure. The reconnection process continues to occur leading to the formation of another current concentration in the middle of the sigmoid where a flaring episode occurs. This central brightening is accompanied by the eruption of a flux rope from the central area of the sigmoid and the appearance of "post-flare" loops underneath the current structure. Title: Observations and Nonlinear Force-Free Field Modeling of Active Region 10953 Authors: Su, Yingna; van Ballegooijen, Adriaan; Lites, Bruce W.; Deluca, Edward E.; Golub, Leon; Grigis, Paolo C.; Huang, Guangli; Ji, Haisheng Bibcode: 2009ApJ...691..105S Altcode: We present multiwavelength observations of a simple bipolar active region (NOAA 10953), which produced several small flares (mostly B class and one C8.5 class) and filament activations from April 30 to May 3 in 2007. We also explore nonlinear force-free field (NLFFF) modeling of this region prior to the C8.5 flare on May 2, using magnetograph data from SOHO/MDI and Hinode/SOT. A series of NLFFF models are constructed using the flux-rope insertion method. By comparing the modeled field lines with multiple X-ray loops observed by Hinode/XRT, we find that the axial flux of the flux rope in the best-fit models is (7± 2)× 1020 Mx, while the poloidal flux has a wider range of (0.1-10)× 1010 Mx cm-1. The axial flux in the best-fit model is well below the upper limit (~15× 1020 Mx) for stable force-free configurations, which is consistent with the fact that no successful full filament eruption occurred in this active region. From multiwavelength observations of the C8.5 flare, we find that the X-ray brightenings (in both RHESSI and XRT) appeared about 20 minutes earlier than the EUV brightenings seen in TRACE 171 Å images and filament activations seen in MLSO Hα images. This is interpreted as an indication that the X-ray emission may be caused by direct coronal heating due to reconnection, and the energy transported down to the chromosphere may be too low to produce EUV brightenings. This flare started from nearly unsheared flare loop, unlike most two-ribbon flares that begin with highly sheared footpoint brightenings. By comparing with our NLFFF model, we find that the early flare loop is located above the flux rope that has a sharp boundary. We suggest that this flare started near the outer edge of the flux rope, not at the inner side or at the bottom as in the standard two-ribbon flare model. Title: Observations and analysis of the April 9, 2008 CME using STEREO, Hinode TRACE and SoHO data Authors: Reeves, K. K.; Patsourakos, S.; Stenborg, G.; Miralles, M.; Deluca, E.; Forbes, T.; Golub, L.; Kasper, J.; Landi, E.; McKenzie, D.; Narukage, N.; Raymond, J.; Savage, S.; Su, Y.; van Ballegooijen, A.; Vourlidas, A.; Webb, D. Bibcode: 2008AGUFMSH12A..04R Altcode: On April 9, 2008 a CME originating from an active region behind the limb was well-observed by STEREO, Hinode, TRACE and SoHO. Several interesting features connected to this eruption were observed. (1) The interaction of the CME with open field lines from a nearby coronal hole appeared to cause an abrupt change in the direction of the CME ejecta. (2) The prominence material was heated, as evidenced by a change from absorption to emission in the EUV wavelengths. (3) Because the active region was behind the limb, the X-Ray Telescope on Hinode was able to take long enough exposure times to observe a faint current- sheet like structure, and it was able to monitor the dynamics of the plasma surrounding this structure. This event is also being studied in the context of activity that occurred during the Whole Heliosphere Interval (WHI). Title: Hinode, TRACE, SOHO, and Ground-based Observations of a Quiescent Prominence Authors: Heinzel, P.; Schmieder, B.; Fárník, F.; Schwartz, P.; Labrosse, N.; Kotrč, P.; Anzer, U.; Molodij, G.; Berlicki, A.; DeLuca, E. E.; Golub, L.; Watanabe, T.; Berger, T. Bibcode: 2008ApJ...686.1383H Altcode: A quiescent prominence was observed by several instruments on 2007 April 25. The temporal evolution was recorded in Hα by the Hinode SOT, in X-rays by the Hinode XRT, and in the 195 Å channel by TRACE. Moreover, ground-based observatories (GBOs) provided calibrated Hα intensities. Simultaneous extreme-UV (EUV) data were also taken by the Hinode EIS and SOHO SUMER and CDS instruments. Here we have selected the SOT Hα image taken at 13:19 UT, which nicely shows the prominence fine structure. We compare this image with cotemporaneous ones taken by the XRT and TRACE and show the intensity variations along several cuts parallel to the solar limb. EIS spectra were obtained about half an hour later. Dark prominence structure clearly seen in the TRACE and EIS 195 Å images is due to the prominence absorption in H I, He I, and He II resonance continua plus the coronal emissivity blocking due to the prominence void (cavity). The void clearly visible in the XRT images is entirely due to X-ray emissivity blocking. We use TRACE, EIS, and XRT data to estimate the amount of absorption and blocking. The Hα integrated intensities independently provide us with an estimate of the Hα opacity, which is related to the opacity of resonance continua as follows from the non-LTE radiative-transfer modeling. However, spatial averaging of the Hα and EUV data have quite different natures, which must be taken into account when evaluating the true opacities. We demonstrate this important effect here for the first time. Finally, based on this multiwavelength analysis, we discuss the determination of the column densities and the ionization degree of hydrogen in the prominence. Title: Small-scale Coronal Jets Authors: Koutchmy, S.; Filippov, B.; Golub, L. Bibcode: 2008ESPM...12.2.93K Altcode: Jet-like events are observed on different scales in the solar corona in EUV and X-rays. They range from gigantic coronal X-ray jets greater than 300 Mm in length to small but numerous jetlets. Polar coronal holes show a significant activity manifested in small loop brightenings and jetlet formation. Geometrical shape of the jetlets and their position indicate that they appear near the singular points of the magnetic field, namely, null points or X-points. These nulls arise due to the interaction between new emerging small dipoles and large-scale magnetic field of the coronal hole. The jetlets reveal some real observable vertical mass motion inside the coronal hole. It is difficult to measure the radial velocity of plasma within the jetlets but it seems large enough to significantly contribute as a large momentum into the solar wind. Finally jetlets could serve as injectors to the process of the solar fast wind acceleration. We believe that similar but even smaller processes could very often happen at smaller scale in the chromosphere near emerging magnetic ephemeral regions forming numerous jetlets of the upper chromosphere. They form the upper chromosphere and follow the direction of the surrounding magnetic field. At the epoch of low activity, the difference in the large-scale structure of the polar magnetic field and that of the low latitude quiet region magnetic field results in a prolateness of the chromosphere. Title: Hinode/XRT Diagnostics of Loop Thermal Structure Authors: Reale, F.; Parenti, S.; Reeves, K. K.; Weber, M.; Bobra, M. G.; Barbera, M.; Kano, R.; Narukage, N.; Shimojo, M.; Sakao, T.; Peres, G.; Golub, L. Bibcode: 2008ASPC..397...50R Altcode: We investigate possible diagnostics of the thermal structure of coronal loops from Hinode/XRT observations made with several filters. We consider the observation of an active region with five filters. We study various possible combinations of filter data to optimize for sensitivity to thermal structure and for signal enhancement. Title: Vertical Temperature Structures of the Solar Corona Derived with the Hinode X-Ray Telescope Authors: Kano, Ryouhei; Sakao, Taro; Narukage, Noriyuki; Tsuneta, Saku; Kotoku, Jun'ichi; Bando, Takamasa; Deluca, Edward; Lundquist, Loraine; Golub, Leon; Hara, Hirohisa; Matsuzaki, Keiichi; Shimojo, Masumi; Shibasaki, Kiyoto; Shimizu, Toshifumi; Nakatani, Ichiro Bibcode: 2008PASJ...60..827K Altcode: We obtained temperature structures in faint coronal features above and near the solar limb with the X-Ray Telescope aboard the Hinode satellite by accurately correcting the scattered X-rays from surrounding bright regions with occulted images during the solar eclipses. Our analysis yields a polar coronal hole temperature of about 1.0MK and an emission measure in the range of 1025.5-1026.0cm-5. In addition, our methods allow us to measure the temperature and emission measure of two distinct quiet-Sun structures: radial (plume-like) structures near the boundary of the coronal-hole and diffuse quiet Sun regions at mid-latitudes. The radial structures appear to have increasing temperature with height during the first 100Mm, and constant temperatures above 100Mm. For the diffuse quiet-Sun region the temperatures are the highest just above the limb, and appear to decrease with height. These differences may be due to different magnetic configurations. Title: The Hinode X-Ray Telescope (XRT): Camera Design, Performance and Operations Authors: Kano, R.; Sakao, T.; Hara, H.; Tsuneta, S.; Matsuzaki, K.; Kumagai, K.; Shimojo, M.; Minesugi, K.; Shibasaki, K.; DeLuca, E. E.; Golub, L.; Bookbinder, J.; Caldwell, D.; Cheimets, P.; Cirtain, J.; Dennis, E.; Kent, T.; Weber, M. Bibcode: 2008SoPh..249..263K Altcode: The X-ray Telescope (XRT) aboard the Hinode satellite is a grazing incidence X-ray imager equipped with a 2048×2048 CCD. The XRT has 1 arcsec pixels with a wide field of view of 34×34 arcmin. It is sensitive to plasmas with a wide temperature range from < 1 to 30 MK, allowing us to obtain TRACE-like low-temperature images as well as Yohkoh/SXT-like high-temperature images. The spacecraft Mission Data Processor (MDP) controls the XRT through sequence tables with versatile autonomous functions such as exposure control, region-of-interest tracking, flare detection, and flare location identification. Data are compressed either with DPCM or JPEG, depending on the purpose. This results in higher cadence and/or wider field of view for a given telemetry bandwidth. With a focus adjust mechanism, a higher resolution of Gaussian focus may be available on-axis. This paper follows the first instrument paper for the XRT (Golub et al., Solar Phys.243, 63, 2007) and discusses the design and measured performance of the X-ray CCD camera for the XRT and its control system with the MDP. Title: Analysis and interpretation of a fast limb CME with eruptive prominence, C-flare, and EUV dimming Authors: Koutchmy, S.; Slemzin, V.; Filippov, B.; Noens, J. -C.; Romeuf, D.; Golub, L. Bibcode: 2008A&A...483..599K Altcode: 2008arXiv0801.2746K Aims: Coronal mass ejections or CMEs are large dynamical solar-corona events. The mass balance and kinematics of a fast limb CME, including its prominence progenitor and the associated flare, will be compared with computed magnetic structures to look for their origin and effect.
Methods: Multi-wavelength ground-based and spaceborne observations are used to study a fast W-limb CME event of December 2, 2003, taking into account both on and off disk observations. Its erupting prominence is measured at high cadence with the Pic du Midi full Hα line-flux imaging coronagraph. EUV images from SOHO/EIT and CORONAS-F/SPIRIT space instruments are processed including difference imaging. SOHO/LASCO images are used to study the mass excess and motions. Computed coronal structures from extrapolated surface magnetic fields are compared to observations.
Results: A fast bright expanding coronal loop is identified in the region recorded slightly later by GOES as a C7.2 flare, followed by a brightening and an acceleration phase of the erupting material with both cool and hot components. The total coronal radiative flux dropped by ~7% in the 19.5 nm channel and by 4% in the 17.5 nm channel, revealing a large dimming effect at and above the limb over a 2 h interval. The typical 3-part structure observed 1 h later by the Lasco C2 and C3 coronagraphs shows a core shaped similarly to the eruptive filament/prominence. The total measured mass of the escaping CME (~1.5×1016 g from C2 LASCO observations) definitely exceeds the estimated mass of the escaping cool prominence material although assumptions made to analyze the Hα erupting prominence, as well as the corresponding EUV darkening of the filament observed several days before, made this evaluation uncertain by a factor of 2. This mass budget suggests that the event is not confined to the eruption region alone. From the current free extrapolation we discuss the shape of the magnetic neutral surface and a possible scenario leading to an instability, including the small scale dynamics inside and around the filament. Title: Observations and NLFFF Modeling of Active Region 10953 Authors: Su, Y.; van Ballegooijen, A.; Golub, L.; Deluca, E. Bibcode: 2008AGUSMSP43C..07S Altcode: We explored the non-linear force free field (NLFFF) modeling of a simple bipolar active region (NOAA 10953), which produced several small flares (mostly B class and one C8.5 class) and filament activations from April 30 to May 3 in 2007. These events appear to be associated with the frequent flux cancellations (SOHO/MDI) that occurred in the region close to the polarity inversion line. Some preliminary results of multi-wavelength observations of a C8.5 flare that occurred on May 2 will be presented. We constructed a series of NLFFF models for this active region at three times, using the flux-rope insertion method. The models are constructed based on MDI magnetograms, and constrained by Hα filaments and highly sheared loops observed by XRT aboard Hinode. We find good NLFFF models that fit the observations before the C8.5 flare, but not for the case after the flare. The flux rope contains highly sheared but weakly twisted magnetic fields. Before the C8.5 flare, this active region is close to an eruptiveon state: the axial flux in the flux rope is close to the upper limit for instability. Title: Magnetic Causes of the Eruption of a Quiescent Filament Authors: Schmieder, B.; Bommier, V.; Kitai, R.; Matsumoto, T.; Ishii, T. T.; Hagino, M.; Li, H.; Golub, L. Bibcode: 2008SoPh..247..321S Altcode: 2007SoPh..tmp..213S During the JOP178 campaign in August 2006, we observed the disappearance of our target, a large quiescent filament located at S25°, after an observation time of three days (24 August to 26 August). Multi-wavelength instruments were operating: THEMIS/MTR ("MulTi-Raies") vector magnetograph, TRACE ("Transition Region and Coronal Explorer") at 171 Å and 1600 Å and Hida Domeless Solar telescope. Counter-streaming flows (+/−10 km s−1) in the filament were detected more than 24 hours before its eruption. A slow rise of the global structure started during this time period with a velocity estimated to be of the order of 1 km s−1. During the hour before the eruption (26 August around 09:00 UT) the velocity reached 5 km s−1. The filament eruption is suspected to be responsible for a slow CME observed by LASCO around 21:00 UT on 26 August. No brightening in Hα or in coronal lines, no new emerging polarities in the filament channel, even with the high polarimetry sensitivity of THEMIS, were detected. We measured a relatively large decrease of the photospheric magnetic field strength of the network (from 400 G to 100 G), whose downward magnetic tension provides stability to the underlying stressed filament magnetic fields. According to some MHD models based on turbulent photospheric diffusion, this gentle decrease of magnetic strength (the tension) could act as the destabilizing mechanism which first leads to the slow filament rise and its fast eruption. Title: Coronal soft X-ray activity in the quiet Sun Authors: Grigis, Paolo; Golub, Leon; Deluca, Edward Bibcode: 2008cosp...37.1077G Altcode: 2008cosp.meet.1077G Small scale coronal activity in the quiet Sun is continuous, ubiquitous and driven by magnetic fields. Typical manifestations of this activity are seen in the form of brightenings in X-ray bright points, network flares, nanoflares. We present high-cadence Hinode/XRT soft X-ray observations of the quiet Sun corona and a statistical analysis of its variability on short timescales (minutes to hours). We explore the connection between this coronal activity (as mapped from the soft X-ray image sequences) and the underlying magnetic field structures. Title: Observations and NLFFF modeling of active region 10953 Authors: Su, Yingna; van Ballegooijen, Adriaan; Golub, Leon; Deluca, Edward Bibcode: 2008cosp...37.3075S Altcode: 2008cosp.meet.3075S We explore the non-linear force free field (NLFFF) modeling of a simple bipolar active region (NOAA 10953), which produced several small flares (mostly B class and one C8.5 class) and filament activations from April 30 to May 3 in 2007. These events appear to be associated with the frequent flux cancellations (SOHO/MDI) that occurred in the region close to the polarity inversion line. Some preliminary results of multi-wavelength observations of a C8.5 flare that occurred on May 2 will be presented. We constructed a series of NLFFF models for this active region at three times, using the flux-rope insertion method. The models are constructed based on MDI magnetograms, and constrained by Hα filaments and highly sheared loops observed by XRT aboard Hinode. We find good NLFFF models that fit the observations before the C8.5 flare, but not for the case after the flare. The flux rope contains highly sheared but weakly twisted magnetic fields. Before the C8.5 flare, this active region is close to an eruptive state: the axial flux in the flux rope is close to the upper limit for instability. Title: The Differential Emission Measure and Analysis of X-Ray Bright Points using Hinode's X-Ray Telescope (XRT) Authors: Farid, S. I.; Saar, S.; Deluca, E.; Golub, L.; Weber, M. Bibcode: 2007AGUFMSH22A0841F Altcode: The X-Ray telescope aboard Hinode utilizes up to thirteen filter combinations with one arc second resolution to provide unprecedented temperature coverage. In this study, we have used eleven X-Ray filters to examine the statistical properties of X-ray bright points including temperature, emission, and size distributions. We have analyzed what appears to be a population of XRBs that are hotter than the main group in order to identify any distinguishing properties.We discuss the results of our analysis and their implications on XBP classification. Title: Slipping Magnetic Reconnection in Coronal Loops Authors: Aulanier, Guillaume; Golub, Leon; DeLuca, Edward E.; Cirtain, Jonathan W.; Kano, Ryouhei; Lundquist, Loraine L.; Narukage, Noriyuki; Sakao, Taro; Weber, Mark A. Bibcode: 2007Sci...318.1588A Altcode: Magnetic reconnection of solar coronal loops is the main process that causes solar flares and possibly coronal heating. In the standard model, magnetic field lines break and reconnect instantaneously at places where the field mapping is discontinuous. However, another mode may operate where the magnetic field mapping is continuous but shows steep gradients: The field lines may slip across each other. Soft x-ray observations of fast bidirectional motions of coronal loops, observed by the Hinode spacecraft, support the existence of this slipping magnetic reconnection regime in the Sun’s corona. This basic process should be considered when interpreting reconnection, both on the Sun and in laboratory-based plasma experiments. Title: Evidence for Alfvén Waves in Solar X-ray Jets Authors: Cirtain, J. W.; Golub, L.; Lundquist, L.; van Ballegooijen, A.; Savcheva, A.; Shimojo, M.; DeLuca, E.; Tsuneta, S.; Sakao, T.; Reeves, K.; Weber, M.; Kano, R.; Narukage, N.; Shibasaki, K. Bibcode: 2007Sci...318.1580C Altcode: Coronal magnetic fields are dynamic, and field lines may misalign, reassemble, and release energy by means of magnetic reconnection. Giant releases may generate solar flares and coronal mass ejections and, on a smaller scale, produce x-ray jets. Hinode observations of polar coronal holes reveal that x-ray jets have two distinct velocities: one near the Alfvén speed (~800 kilometers per second) and another near the sound speed (200 kilometers per second). Many more jets were seen than have been reported previously; we detected an average of 10 events per hour up to these speeds, whereas previous observations documented only a handful per day with lower average speeds of 200 kilometers per second. The x-ray jets are about 2 × 103 to 2 × 104 kilometers wide and 1 × 105 kilometers long and last from 100 to 2500 seconds. The large number of events, coupled with the high velocities of the apparent outflows, indicates that the jets may contribute to the high-speed solar wind. Title: Continuous Plasma Outflows from the Edge of a Solar Active Region as a Possible Source of Solar Wind Authors: Sakao, Taro; Kano, Ryouhei; Narukage, Noriyuki; Kotoku, Jun'ichi; Bando, Takamasa; DeLuca, Edward E.; Lundquist, Loraine L.; Tsuneta, Saku; Harra, Louise K.; Katsukawa, Yukio; Kubo, Masahito; Hara, Hirohisa; Matsuzaki, Keiichi; Shimojo, Masumi; Bookbinder, Jay A.; Golub, Leon; Korreck, Kelly E.; Su, Yingna; Shibasaki, Kiyoto; Shimizu, Toshifumi; Nakatani, Ichiro Bibcode: 2007Sci...318.1585S Altcode: The Sun continuously expels a huge amount of ionized material into interplanetary space as the solar wind. Despite its influence on the heliospheric environment, the origin of the solar wind has yet to be well identified. In this paper, we report Hinode X-ray Telescope observations of a solar active region. At the edge of the active region, located adjacent to a coronal hole, a pattern of continuous outflow of soft-x-ray emitting plasmas was identified emanating along apparently open magnetic field lines and into the upper corona. Estimates of temperature and density for the outflowing plasmas suggest a mass loss rate that amounts to ~1/4 of the total mass loss rate of the solar wind. These outflows may be indicative of one of the solar wind sources at the Sun. Title: Fine Thermal Structure of a Coronal Active Region Authors: Reale, Fabio; Parenti, Susanna; Reeves, Kathy K.; Weber, Mark; Bobra, Monica G.; Barbera, Marco; Kano, Ryouhei; Narukage, Noriyuki; Shimojo, Masumi; Sakao, Taro; Peres, Giovanni; Golub, Leon Bibcode: 2007Sci...318.1582R Altcode: The determination of the fine thermal structure of the solar corona is fundamental to constraining the coronal heating mechanisms. The Hinode X-ray Telescope collected images of the solar corona in different passbands, thus providing temperature diagnostics through energy ratios. By combining different filters to optimize the signal-to-noise ratio, we observed a coronal active region in five filters, revealing a highly thermally structured corona: very fine structures in the core of the region and on a larger scale further away. We observed continuous thermal distribution along the coronal loops, as well as entangled structures, and variations of thermal structuring along the line of sight. Title: Magnetic Feature and Morphological Study of X-Ray Bright Points with Hinode Authors: Kotoku, Jun'ichi; Kano, Ryouhei; Tsuneta, Saku; Katsukawa, Yukio; Shimizu, Toshifumi; Sakao, Taro; Shibazaki, Kiyoto; Deluca, Edward E.; Korreck, Kelly E.; Golub, Leon; Bobra, Monica Bibcode: 2007PASJ...59S.735K Altcode: We observed X-ray bright points (XBPs) in a quiet region of the Sun with the X-Ray Telescope (XRT) aboard the Hinode satellite on 2006 December 19. XRT's high-resolution X-ray images revealed many XBPs with complicated structure and evolving dramatically with time. Almost all of the dynamic eruptions in the quiet region were composed of XBPs, and they had either loop or multiloop shapes, as is observed in larger flares. Brightening XBPs had strong magnetic fields with opposite polarities near their footpoints. While we have found a possible example of associated magnetic cancellation, other XBPs brighten and fade without any associated movement of the photospheric magnetic field. Title: A Study of Polar Jet Parameters Based on Hinode XRT Observations Authors: Savcheva, Antonia; Cirtain, Jonathan; Deluca, Edward E.; Lundquist, Loraine L.; Golub, Leon; Weber, Mark; Shimojo, Masumi; Shibasaki, Kiyoto; Sakao, Taro; Narukage, Noriyuki; Tsuneta, Saku; Kano, Ryouhei Bibcode: 2007PASJ...59S.771S Altcode: Hinode/SOHO campaign 7197 is the most extensive study of polar jet formation and evolution from within both the north and south polar coronal holes so far. For the first time, this study showed that the appearance of X-ray jets in the solar coronal holes occurs at very high frequency - about 60 jets d-1 on average. Using observations collected by the X-Ray Telescope on Hinode, a number of physical parameters from a large sample of jets were statistically studied. We measured the apparent outward velocity, the height, the width and the lifetime of the jets. In our sample, all of these parameters show peaked distributions with maxima at 160kms-1 for the outward velocity, 5 × 104 km for the height, 8 × 103 km for the width, and about 10min for the lifetime of the jets. We also present the first statistical study of jet transverse motions, which obtained transverse velocities of 0-35kms-1. These values were obtained on the basis of a larger (in terms of frequency) and better sampled set of events than what was previously statistically studied (Shimojo et al. 1996, PASJ, 48, 123). The results were made possible by the unique characteristics of XRT. We describe the methods used to determine the characteristics and set some future goals. We also show that despite some possible selection effects, jets preferably occur inside the polar coronal holes. Title: Evolution of the Sheared Magnetic Fields of Two X-Class Flares Observed by Hinode/XRT Authors: Su, Yingna; Golub, Leon; van Ballegooijen, Adriaan; Deluca, Edward E.; Reeves, Kathy K.; Sakao, Taro; Kano, Ryouhei; Narukage, Noriyuki; Shibasaki Kiyoto Bibcode: 2007PASJ...59S.785S Altcode: We present multi-wavelength observations of the evolution of the sheared magnetic fields in NOAA Active Region 10930, where two X-class flares occurred on 2006 December 13 and December 14, respectively. Observations made with the X-ray Telescope (XRT) and the Solar Optical Telescope (SOT) aboard Hinode suggest that the gradual formation of the sheared magnetic fields in this active region is caused by the rotation and west-to-east motion of an emerging sunspot. In the pre-flare phase of the two flares, XRT shows several highly sheared X-ray loops in the core field region, corresponding to a filament seen in the TRACE EUV observations. XRT observations also show that part of the sheared core field erupted, and another part of the sheared core field stayed behind during the flares, which may explain why a large part of the filament is still seen by TRACE after the flare. About 2-3 hours after the peak of each flare, the core field becomes visible in XRT again, and shows a highly sheared inner and less-sheared outer structure. We also find that the post-flare core field is clearly less sheared than the pre-flare core field, which is consistent with the idea that the energy released during the flares is stored in the highly sheared fields prior to the flare. Title: An On-Orbit Determination of the On-Axis Point Spread Function of the Hinode X-Ray Telescope Authors: Weber, Mark; Deluca, Edward E.; Golub, Leon; Cirtain, Jonathan; Kano, Ryouhei; Sakao, Taro; Shibasaki, Kiyoto; Narukage, Noriyuki Bibcode: 2007PASJ...59S.853W Altcode: The Hinode X-ray Telescope provides unprecedented observations of the solar corona in X-rays, due in part to its fine resolution. The X-ray point spread function (PSF) was measured before launch at the NASA X-ray Calibration Facility to have a FWHM of 0.8''. This paper describes the work to verify the PSF measurements using on-orbit observations of planetary transits and solar eclipses. Analysis of a Mercury transit gives a PSF FWHM = 1.0" ± 0.12". Title: What Determines the Intensity of Solar Flare/CME Events? Authors: Su, Yingna; Van Ballegooijen, Adriaan; McCaughey, James; Deluca, Edward; Reeves, Katharine K.; Golub, Leon Bibcode: 2007ApJ...665.1448S Altcode: We present a comprehensive statistical study addressing the question of what determines the intensity of a solar flare and associated coronal mass ejection (CME). For a sample of 18 two-ribbon flares associated with CMEs, we have examined the correlations between the GOES soft X-ray peak flare flux (PFF), the CME speed (VCME) obtained from SOHO LASCO observations, and six magnetic parameters of the flaring active region. These six parameters measured from both TRACE and SOHO MDI observations are: the average background magnetic field strength (B), the area of the region where B is counted (S), the magnetic flux of this region (Φ), the initial shear angle (θ1, measured at the flare onset), the final shear angle (θ2, measured at the time when the shear change stops), and the change of shear angle (θ12=θ1-θ2) of the footpoints. We have found no correlation between θ1 and the intensity of flare/CME events, while the other five parameters are either positively or negatively correlated with both log10(PFF) and VCME. Among these five parameters, Φ and θ12 show the most significant correlations with log10(PFF) and VCME. The fact that both log10(PFF) and VCME are highly correlated with θ12 rather than with θ1 indicates that the intensity of flare/CME events may depend on the released magnetic free energy rather than the total free energy stored prior to the flare. We have also found that a linear combination of a subset of these six parameters shows a much better correlation with the intensity of flare/CME events than each parameter itself, and the combination of log10Φ, θ1, and θ12 is the top-ranked combination. Title: The Hinode (Solar-B) Mission: An Overview Authors: Kosugi, T.; Matsuzaki, K.; Sakao, T.; Shimizu, T.; Sone, Y.; Tachikawa, S.; Hashimoto, T.; Minesugi, K.; Ohnishi, A.; Yamada, T.; Tsuneta, S.; Hara, H.; Ichimoto, K.; Suematsu, Y.; Shimojo, M.; Watanabe, T.; Shimada, S.; Davis, J. M.; Hill, L. D.; Owens, J. K.; Title, A. M.; Culhane, J. L.; Harra, L. K.; Doschek, G. A.; Golub, L. Bibcode: 2007SoPh..243....3K Altcode: The Hinode satellite (formerly Solar-B) of the Japan Aerospace Exploration Agency's Institute of Space and Astronautical Science (ISAS/JAXA) was successfully launched in September 2006. As the successor to the Yohkoh mission, it aims to understand how magnetic energy gets transferred from the photosphere to the upper atmosphere and results in explosive energy releases. Hinode is an observatory style mission, with all the instruments being designed and built to work together to address the science aims. There are three instruments onboard: the Solar Optical Telescope (SOT), the EUV Imaging Spectrometer (EIS), and the X-Ray Telescope (XRT). This paper provides an overview of the mission, detailing the satellite, the scientific payload, and operations. It will conclude with discussions on how the international science community can participate in the analysis of the mission data. Title: The X-Ray Telescope (XRT) for the Hinode Mission Authors: Golub, L.; DeLuca, E.; Austin, G.; Bookbinder, J.; Caldwell, D.; Cheimets, P.; Cirtain, J.; Cosmo, M.; Reid, P.; Sette, A.; Weber, M.; Sakao, T.; Kano, R.; Shibasaki, K.; Hara, H.; Tsuneta, S.; Kumagai, K.; Tamura, T.; Shimojo, M.; McCracken, J.; Carpenter, J.; Haight, H.; Siler, R.; Wright, E.; Tucker, J.; Rutledge, H.; Barbera, M.; Peres, G.; Varisco, S. Bibcode: 2007SoPh..243...63G Altcode: The X-ray Telescope (XRT) of the Hinode mission provides an unprecedented combination of spatial and temporal resolution in solar coronal studies. The high sensitivity and broad dynamic range of XRT, coupled with the spacecraft's onboard memory capacity and the planned downlink capability will permit a broad range of coronal studies over an extended period of time, for targets ranging from quiet Sun to X-flares. This paper discusses in detail the design, calibration, and measured performance of the XRT instrument up to the focal plane. The CCD camera and data handling are discussed separately in a companion paper. Title: Atomic force microscopy characterization of Zerodur mirror substrates for the extreme ultraviolet telescopes aboard NASA's Solar Dynamics Observatory Authors: Soufli, Regina; Baker, Sherry L.; Windt, David L.; Gullikson, Eric M.; Robinson, Jeff C.; Podgorski, William A.; Golub, Leon Bibcode: 2007ApOpt..46.3156S Altcode: The high-spatial frequency roughness of a mirror operating at extreme ultraviolet (EUV) wavelengths is crucial for the reflective performance and is subject to very stringent specifications. To understand and predict mirror performance, precision metrology is required for measuring the surface roughness. Zerodur mirror substrates made by two different polishing vendors for a suite of EUV telescopes for solar physics were characterized by atomic force microscopy (AFM). The AFM measurements revealed features in the topography of each substrate that are associated with specific polishing techniques. Theoretical predictions of the mirror performance based on the AFM-measured high-spatial-frequency roughness are in good agreement with EUV reflectance measurements of the mirrors after multilayer coating. Title: The Dynamics Of Fine Structures In Solar X-ray Jets Authors: Shimojo, Masumi; Narukage, N.; Kano, R.; Sakao, T.; Tsuneta, T.; Cirtain, J. W.; Lundquist, L. L.; Deluca, E. E.; Golub, L. Bibcode: 2007AAS...210.9422S Altcode: 2007BAAS...39Q.221S The X-ray telescope(XRT) aboard HINODE satellite has the great spatial/time resolution in X-ray range. And, the observations using XRT have revealed the fine structures of solar corona. From the observations, we found the fine thread structures in the X-ray jets and the structures move dynamically like wave. We also found that some X-ray jets start just after small loop expansion in the footpoint brightening. The observation results suggest that the reconnection process X-ray jets is very similar to that in large flares. Title: Coronal Temperature Diagnostics With Hinode X-ray Telescope Authors: Narukage, Noriyuki; Sakao, T.; Kano, R.; Shimojo, M.; Tsuneta, S.; Kosugi, T.; Deluca, E. E.; Golub, L.; Weber, M.; Cirtain, J.; Japan-US X-Ray Telescope Team Bibcode: 2007AAS...210.6304N Altcode: 2007BAAS...39..172N An X-ray telescope (XRT) on board HINODE satellite observes the Sun in X-rays with high special resolution (1arcsec 730km on solar the disk). This telescope has 9 X-ray filters with different temperature responses. Using these filters, the XRT can detect the coronal plasma with a wide temperature range from less than 1MK to more than 10MK. Moreover, based on observations with more than 2 filters, we can estimate the coronal temperature. In this paper, we use the filter ratio method for coronal temperature diagnostics. Using this method, we can easily estimate the averaged temperature of the coronal plasma along the line-of-sight. This method has been used frequently in the past, but the high quality XRT data give us temperature maps with unprecedented accuracy and resolution. The XRT usually takes the full Sun images with 2 kinds of filters 4 times a day. Using this data and filter ratio method, we can obtain full Sun temperature maps with high special resolution. In our analysis, we can derive reliable temperatures not only in active regions but also in quiet regions and coronal holes. This map can be created with the data set of one synoptic observation. This means that we can obtain 4 maps a day. The result is a full Sun temperature movie that gives us an unprecedented view of the time evolution of solar temperature. In this meeting, we will show the full Sun temperature movie and our coronal temperature analysis results. Title: Slip running reconnection in the Sun's atmosphere observed by RHESSI, SOHO, TRACE and Hinode Authors: Schmieder, B.; Aulanier, G.; Démoulin, P.; Pariat, E.; Golub, L. Bibcode: 2007AGUSMSH22A..01S Altcode: Solar double ribbon flares are commonly explained by magnetic field reconnections in the high corona. The bright ribbons, typically observed in Halpha, in EUV with SoHO, TRACE correspond to the ends of the reconnected loops. In most studied cases, the reconnection site is an X-point, where two magnetic separatrices intersect. In this presentation, we show a generalization of this model to 3D complex magnetic topologies where there are no null points, but quasi-separatrices layers instead. In that case, while the ribbons spread away during reconnection, we show that magnetic field lines can quickly slip along them. We propose that this new phenomenon could explain also fast moving HXR footpoints as observed by RHESSI, and that it may be observed in soft X rays with XRT. Title: Magnetic Shear in Two-ribbon Solar Flares Authors: Su, Yingna; Golub, L.; Van Ballegooijen, A.; McCaughey, J.; Deluca, E. E.; Reeves, K.; Gros, M. Bibcode: 2007AAS...210.3702S Altcode: 2007BAAS...39Q.151S To study shear motion of the footpoints in solar flares, we selected 50 X- and M- class two-ribbon flares observed by TRACE (in 1998-2005) as our data sample. We found that: 1) 86% (43 out of 50) of these flares show both strong-to-weak shear change of footpoints and ribbon separation. Shear motion of footpoints is thus a common feature in two-ribbon flares; 2) the initial and final shear angles of the footpoints in this type of flare are mainly in the range from 50° to 80° and 15° to 55°, respectively; 3) in 10 out of the 14 events with both measured shear angle and corresponding hard X-ray observations, the cessation of shear change is 0-2 minutes earlier than the end of the impulsive phase. This may suggest that the change from impulsive to gradual phase is related to magnetic shear change. We then selected 20 flares with measured shear angles and corresponding CMEs from our data sample. For these flares, we found that the magnetic flux and change of shear angle show comparably strong correlations with the peak flare flux and CME speed, while the intial shear angle does not. This result indicates that the intensity of flare/CME events may depend mainly on the released magnetic free energy rather than the total magnetic free energy stored prior to the eruption. After a successful launch last September, Hinode (Solar-B) caught two X-class solar flares, which occurred in AR 10930 on Dec 13 and 14, 2006. Using these new datasets (Hinode/XRT, Hinode/SOT, TRACE, and SOHO/MDI), we carried out a study of the evolution of the sheared magnetic fields involved in these flares, and some preliminary results will also be presented. The TRACE analysis was supported at Smithsonian Astrophysical Observatory by a contract from Lockheed Martin. Title: Intercalibration of the X-ray Telescope and the EUV Imaging Spectrometer on Hinode Authors: Golub, Leon; Cirtain, J.; DeLuca, E. E.; Hara, H.; Warren, H.; Weber, M. Bibcode: 2007AAS...210.9418G Altcode: 2007BAAS...39..220G The X-Ray Telescope and the Extreme-Ultra Violet Imaging Spectrometer on Hinode are designed to measure the emission of excited ions formed at temperatures ranging from 104-108 K. The temperature overlap of these two telescope is from 0.7 to 20 MK, and an on-orbit calibration of the sensitivity of the two instruments to solar features will provide a basis for future observational comparisons. Using calibrated samples of data from each instrument, and relying to a great extent on the CHIANTI spectral code, we have derived an estimate of the inter-calibration of the two telescope for a variety of different solar features and conditions. This is a major step in enhancing our ability to use the instruments together for providing quantitative diagnostics of the solar plasma. Title: Continuous Upflow of Plasmas at the Edge of an Active Region as Revealed by the X-ray Telescope (XRT) aboard Hinode Authors: Sakao, Taro; Kano, R.; Narukage, N.; Kotoku, J.; Bando, T.; DeLuca, E. E.; Lundquist, L. L.; Golub, L.; Kubo, M.; Katsukawa, Y.; Tsuneta, S.; Hara, H.; Matsuzaki, K.; Shimojo, M.; Shibasaki, K.; Shimizu, T.; Nakatani, I. Bibcode: 2007AAS...210.7205S Altcode: 2007BAAS...39Q.179S We present X-ray imaging observations with Hinode X-Ray Telescope (XRT) of an active region NOAA AR 10942 made in the period of 20-22 February 2007. A prominent feature that drew our particular attention is that there revealed continuous upflow of soft-X-ray-emitting plasmas along apparently-open field lines towards the outer corona emanating from the edge of the active region.

The field lines are originated from an ensamble of small spots of following polarity, and are located at a border between the active region and an adjacent equatorial coronal hole(s) located to the east. The upflow was observed to be continuous throughout the three days of observation intervals with projected velocity of 140 km/s, accompanied with undulating motion of the field lines.

We assert that these upflowing plasmas would be a possible source of slow solar wind material, which supports a foresighted notion which grew out of interplanetary scintillation observations that slow solar wind most likely has its origin in the vicinity of active regions with large flux expansion (Kojima et al. 1999).

A preliminaty analysis indicates that the temperature of the upflowing material near the base of the field lines is 1.3 MK with number density of 2 × 109 /cm3. Assuming that all the material is to escape to the interplanetary space, this leads to a mass loss rate of 2 × 1011 g/s which amounts to a good fraction of the total mass loss rate for solar wind. It is noteworthy that, even apart from this unique upflow, we see continuous (up)flows of plasmas anywhere around (surrounding) the active region.

Details of the upflow will be presented and their possible implication to slow solar wind discussed. Title: On-orbit Measurement Of The Hinode/XRT Point Spread Function Authors: Weber, Mark A.; Cirtain, J.; Golub, L.; DeLuca, E. E.; Martens, P.; XRT Team Bibcode: 2007AAS...210.9416W Altcode: 2007BAAS...39..220W The Hinode X-Ray Telescope provides unprecedented observations of the solar corona in x-rays, due in part to its fine resolution. The optical point spread function (PSF) was measured before launch at the NASA X-Ray Calibration Facility to have a FWHM of 0.92 arc-seconds. In this poster we describe our work to verify the PSF measurements using on-orbit data. The US XRT team is supported by a contract from NASA to SAO. Hinode is an international project supported by JAXA, NASA, PPARC, and ESA. We are grateful to the Hinode team for all their efforts in the design, development, and operation of the mission. Title: Temperature Structures Above Coronal Hole and Quiet Sun Authors: Kano, Ryouhei; Sakao, T.; Narukage, N.; Kotoku, J.; Bando, T.; DeLuca, E. E.; Lundquist, L.; Golub, L.; Tsuneta, S.; Hara, H.; Shibasaki, K.; Shimojo, M. Bibcode: 2007AAS...210.9436K Altcode: 2007BAAS...39..223K The X-ray Telescope (XRT) on board Hinode satelite has the capability to derive the temperature structure in the solar corona. We present the hieght dependence of the temperature above the limb. Because X-ray intensity above the limb is so faint, it is important to estimate the scattered light from disk corona. The eclipses happened on February 17 and March 19 in 2007 at Hinode orbit. On February 17, we took X-ray images above the south polar coronal hole, while Moon passed it. On March 19, we took the data for quiet Sun in the same way.

We can estimated the scattered light from the eclipse data, and derived the scatter-free X-ray images above the solar limb. In this meeting, we will present the temperatures above coronal hole and quiet Sun, based on the eclipse data. Title: A Statistical Study of Shear Motion of the Footpoints in Two-Ribbon Flares Authors: Su, Yingna; Golub, Leon; Van Ballegooijen, Adriaan A. Bibcode: 2007ApJ...655..606S Altcode: We present a statistical investigation of shear motion of the ultraviolet (UV) or extreme-ultraviolet (EUV) footpoints in two-ribbon flares, using the high spatial resolution data obtained in 1998-2005 by TRACE. To do this study, we have selected 50 well-observed X and M class two-ribbon flares as our sample. All 50 of these flares are classified into three types based on the motions of the footpoints with respect to the magnetic field (SOHO MDI). The relation between our classification scheme and the traditional classification scheme (i.e., ``ejective'' and ``confined'' flares) is discussed. We have found that 86% (43 out of 50) of these flares show both strong-to-weak shear change of footpoints and ribbon separation (type I flares), and 14% of the flares show no measurable shear change of conjugate footpoints, including two flares with very small ribbon separation (type II flares) and five flares having no ribbon separation at all through the entire flare process (type III flares). Shear motion of footpoints is thus a common feature in two-ribbon flares. A detailed analysis of the type I flares shows (1) for a subset of 20 flares, the initial and final shear angles of the footpoints are mainly in the range 50°-80° and 15°-55°, respectively; and (2) in 10 of the 14 flares having both measured shear angle and corresponding hard X-ray observations, the cessation of shear change is 0-2 minutes earlier than the end of the impulsive phase, which may suggest that the change from impulsive to gradual phase is related to magnetic shear change. Title: Magnetic activity and the solar corona: first results from the Hinode satellite . Authors: Reale, Fabio; Parenti, Susanna; Reeves, Kathy K.; Weber, Mark; Bobra, Monica G.; Barbera, Marco; Kano, Ryohei; Narukage, Noriyuki; Shimojo, Masumi; Sakao, Taro; Peres, Giovanni; Golub, Leon Bibcode: 2007MmSAI..78..591R Altcode: The structure, dynamics and evolution of the solar corona are governed by the magnetic field. In spite of significant progresses in our insight of the physics of the solar corona, several problems are still under debate, e.g. the role of impulsive events and waves in coronal heating, and the origin of eruptions, flares and CMEs. The Hinode mission has started on 22 september 2006 and aims at giving new answers to these questions. The satellite contains three main instruments, two high resolution telescopes, one in the optical and one in the X-ray band, and an EUV imaging spectrometer. On the Italian side, INAF/Osservatorio Astronomico di Palermo has contributed with the ground-calibration of the filters of the X-ray telescope. We present some preliminary mission results, with particular attention to the X-ray telescope data. Title: Coronal Dynamics and the AIA on SDO Authors: Golub, L. Bibcode: 2007sdeh.book...23G Altcode: No abstract at ADS Title: First Results From The Solar-B Mission, Part I Authors: Golub, L.; International Members, S. Bibcode: 2006AGUFMSH23A0337G Altcode: The Solar-B Observatory is a highly capable satellite equipped with three advanced solar telescopes. Its solar optical telescope (SOT) has an unprecedented 0.2 arcsec resolution for observation of the solar atmosphere from space in multiple optical passbands. It will also, for the first time, measure the vector magnetic fields from space. The X-ray telescope (XRT) has broad temperature coverage and a spatial a resolution three times as high as Yohkoh. The image cadence will be significantly higher than Yohkoh's and a flare buffer will provide exceptional capability for observing rapid changes at flare onset. The EUV imaging spectrometer (EIS) has sensitivity ten times as high as the ESA SOHO instrument and covers a broad range of transition region and coronal temperatures. Flexible operating modes permit slit, slot and raster options in a selectable number of spectral lines. Both XRT and EIS have 2 arcsec spatial resolution (1 arcsec pixels). Solar-B is the follow-up mission to the very successful Japan/UK/US Yohkoh mission. We present a status report from the initial operation of the observatory, showing some of the first observations obtained. Following a short commissioning phase, science planning and regular operations are due to begin January 2007. All mission data will be open and freely available to researchers shortly after receipt at the DARTS data archive hosted in Japan. Title: Analysis of Magnetic Shear in An X17 Solar Flare on October 28, 2003 Authors: Su, Y. N.; Golub, L.; Van Ballegooijen, A. A.; Gros, M. Bibcode: 2006SoPh..236..325S Altcode: An X17 class (GOES soft X-ray) two-ribbon solar flare on October 28, 2003 is analyzed in order to determine the relationship between the timing of the impulsive phase of the flare and the magnetic shear change in the flaring region. EUV observations made by the Transition Region and Coronal Explorer (TRACE) show a clear decrease in the shear of the flare footpoints during the flare. The shear change stopped in the middle of the impulsive phase. The observations are interpreted in terms of the splitting of the sheared envelope field of the greatly sheared core rope during the early phase of the flare. We have also investigated the temporal correlation between the EUV emission from the brightenings observed by TRACE and the hard X-ray (HXR) emission (E > 150 keV) observed by the anticoincidence system (ACS) of the spectrometer SPI on board the ESA INTEGRAL satellite. The correlation between these two emissions is very good, and the HXR sources (RHESSI) late in the flare are located within the two EUV ribbons. These observations are favorable to the explanation that the EUV brightenings mainly result from direct bombardment of the atmosphere by the energetic particles accelerated at the reconnection site, as does the HXR emission. However, if there is a high temperature (T > 20 MK) HXR source close to the loop top, a contribution of thermal conduction to the EUV brightenings cannot be ruled out. Title: The Atmospheric Imaging Assembly (AIA) for the Solar Dynamics Observatory Authors: Smith, Peter L.; Golub, L.; Bookbinder, J. A.; Reid, P. B.; Deluca, E. E.; Cheimets, P. N.; Podgorski, W. A.; Title, A. M.; Lemen, J. R.; Boerner, P. F.; SAO, Science, and LMSAL Engineering Teams Bibcode: 2006SPD....37.0119S Altcode: 2006BAAS...38Q.218S The Atmospheric Imaging Assembly (AIA) is being developed for the Solar Dynamics Observatory (SDO), which is designed to study the Sun as part of NASA's Living With a Star program. AIA comprises four normal-incidence telescopes with multilayer-coated optics; entrance-aperture and focal-plane filters limit the bandpasses. Solar radiation from the upper solar atmosphere at six wavelengths corresponding to temperatures between 6.3×105 and 1.5×107 K [Fe IX (171 Å) Fe XII, XXIV (193 Å) Fe XIV (211 Å) Fe XVI (335 Å) Fe XVIII (94 Å) and Fe XX, XXIII (131 Å)] will be recorded with high spatial resolution (0.6 arcsec pixels). Other channels enable observations of the chromosphere (He II 304 Å C IV 1550 Å) and the photosphere. Each telescope contains a 4096 x 4096 CCD camera system and has a 41 arcmin field of view. AIA will return 8 full-solar-disk images every 10 s. The 5-year SDO mission is scheduled to launch in late 2008. The imaging performance of the telescopes, which are being provided by the Smithsonian Astrophysical Observatory, and performance of the multilayer coatings, which are responsible for the large effective area of AIA, will be discussed in the context of AIA science goals. Title: The Hi-C Sounding Rocket Experiment Authors: Golub, Leon; Cirtain, J.; DeLuca, E.; Nystrom, G.; Kankelborg, C.; Klumpar, D.; Longcope, D.; Martens, P. Bibcode: 2006SPD....37.0605G Altcode: 2006BAAS...38R.226G The High-resolution Coronal Imager, Hi-C, is a pathfinder mission designed to place significant new limits on theories of coronal heating and dynamics by measuring the structures at size scales relevant to reconnection physics. The Hi-C instrument uses normal-incidence EUV multilayer technology, as developed in the NIXT and TRACE programs. A dual-channel long focal-length telescope and large format back-illuminated CCD camera provide spectroscopic imaging of the corona at 0.1 arcsec resolution.The main objective of the Hi-C investigation is to determine the geometric configuration and topology of the structures making up the inner corona. The secondary objective is to examine the dynamics of those structures, within the constraints of the 300-seconds of observing time available from a sounding rocket. The mission is designed to study the mechanisms for growth, diffusion and reconnection of magnetic fields, and to help understand the coupling of small-scale dynamic and eruptive processes to large-scale dynamics.Hi-C will benefit from a unique coordinated observation opportunity with investigations such as AIA on SDO, XRT on Solar-B, and STEREO. Hi-C will address basic plasma physics science goals of the SSSC by observing the small-scale processes that are ubiquitous in hot magnetized coronal plasma. The scientific objectives of Hi-C are central to the SSSC goal of understanding the Sun's activity and its effects on the terrestrial environment, by providing unique and unprecedented views of the dynamic activity in the solar atmosphere. Title: Magnetic Shear Change in Solar Flares Authors: Su, Yingna; Golub, L.; Van Ballegooijen, A. Bibcode: 2006SPD....37.0827S Altcode: 2006BAAS...38..235S; 2006SPD....37.0827Y It is well known that during a two-ribbon flare the two footpoint ribbons, residing in opposite magnetic polarities, expand outward and away from each other. However, the shear motion of the footpoints along the direction parallel to the magnetic inversion line has only been examined by several authors in some individual two-ribbon flares. This motion, also described as shear change of the footpoints, is interpreted by a magnetic field model with a highly sheared inner and less sheared outer magnetic field configuration during the pre-flare phase, and the cessation of the shear change during the impulsive phase is interpreted as a splitting of the envelope of the highly sheared core field. We have made a statistical investigation of the EUV footpoint shear motion along the direction parallel to the magnetic inversion line in two-ribbon flares, using the high spatial resolution data obtained in 1998-2005 by Transition Region and Coronal Explorer (TRACE). For this study we identified 52 well-observed X- and M- class two-ribbon flares which fit our criteria: (1) most portions of the two ribbons are inside the field of view (FOV); (2) TRACE obtained several images during the rise and impulsive phase, from which we can see the two ribbons and their evolution clearly; (3) limb flares, which make the two ribbons and their evolution unable to be seen are not considered. Our preliminary results are: a) 87% (45 out of 52 of these flares (Type I flare) show shear change of footpoints and ribbon separation; b) in most Type I flares, the cessation of shear change is 1-2 minutes earlier than the end of the impulsive phase; c) there is no obvious ribbon separation in those 7 flares (Type II flare) which have no shear change of the conjugate footpoints. Title: Coronal Dynamics and the AIA on SDO Authors: Golub, L. Bibcode: 2006SSRv..124...23G Altcode: 2007SSRv..tmp...48G We provide a brief overview of present-day studies of inner corona dynamics, with examples of mass ejections (CME), flares and active region dynamics. While the names of the topics have not changed in several decades, the internal details and the language used to express the nature of the problem have changed considerably. We conclude with a short discussion of the contribution to studies of coronal dynamics to be expected from the Atmospheric Imager Assembly (AIA) on the Solar Dynamics Observatory. Title: A statistical study of shear motion of EUV footpoints in two-ribbon flares Authors: Su, Y. N.; Golub, L.; van Ballegooijen, A. A.; Huang, G. L. Bibcode: 2006IAUS..233..409S Altcode: We present a statistical investigation of shear motion of the EUV footpoints in two-ribbon solar flares, using the high spatial resolution data obtained in 1998-2005 by the Transition Region and Coronal Explorer (TRACE). In this study we have selected 50 well-observed X- and M- class two-ribbon flares. Our preliminary results are: a) 86% (43 out of 50) of these flares show shear change of footpoints and ribbon separation; b) there is no obvious ribbon separation in those 7 flares which have no shear change of the conjugate footpoints; c) in most events, the cessation of shear change is 0-2 minutes earlier than the end of the impulsive phase. Title: The Reconnection and Microscale (RAM) Mission in the LWS Context Authors: Golub, L.; Deluca, E. Bibcode: 2005AGUFMSH54A..02G Altcode: Hot magnetized plasmas are ubiquitous throughout the universe. The physics governing the dynamics of such plasmas takes place on remarkably small spatial and temporal scales, while both the cause of and the response to this activity occur on large spatial scales. Understanding the dynamics, energetics, and coupling between magnetic fields and plasmas are key focal points of research in astro-, space, and solar physics. Studying the Sun provides unique opportunities to examine these processes with unprecedented detail and scope unattainable for more remote objects. Few problems have proved as resistant to solution as the production of high-energy particles in hot magnetized plasmas. Theory and observations indicate that both magnetic reconnection and shocks can accelerate particles to high energies, involving small-scale structures that ultimately affect a much larger volume. Reconnection has been invoked to explain a wide range of explosive solar activity, from surges to coronal mass ejections, requiring the creation and dissipation of fine-scale currents. The Reconnection and Microscale (RAM) Mission is focused on understanding these key processes on the Sun, with particular emphasis on the production of high-energy particles and radiation. RAM obtains imaging and spectroscopic data with unprecedented resolution, and distinguishes among proposed energy-release and particle-acceleration mechanisms by determining the fine-scale structure of heated and cooling threads, and by observing the detailed evolution of multithermal plasmas using high-cadence spectroscopic imaging with broad temperature coverage. Lessons learned will also be applicable to both laboratory and non-solar magnetoplasmas, from the magnetosphere to active galaxies. Title: Analysis of EUV Brightenings of Solar Flares Authors: Su, Y.; Golub, L.; van Ballegooijen, A.; Gros, M. Bibcode: 2005AGUFMSH13A0272S Altcode: An X17 class (GOES soft X-ray) two-ribbon solar flare occurred on 2003 October 28. EUV observations made by the Transition Region and Coronal Explorer (TRACE) show us that the two flare ribbons are initially composed of several discrete bright kernels. High time resolution hard X-ray (HXR) (E >150 KeV) data were obtained by the anticoincidence system (ACS) of the spectrometer SPI on board the ESA INTEGRAL satellite, and 8 spikes can be seen during the impulsive phase of the solar flare. The comparison of the evolution of EUV bright kernels and HXR light curves shows us that individual peaks in the HXR bursts are associated with peaks in the EUV light curves of individual bright kernels, which suggests that the EUV kernels result from direct energy deposition of the energetic particles accelerated in the flare. EUV bright kernels within the flare ribbons are tracked and identified as conjugate footpoints using a manual method. The co-alignment of TRACE/EUV and Hα images from Big Bear Solar Observatory (BBSO) using EIT and MDI data from SOHO allows us to obtain information about the ribbon's underlying magnetic inversion line. We find that the EUV conjugate footpoints start (3 minutes before the hard X-ray onset) at a position close to, but with a large separation along, the magnetic inversion line and evolve into straight across and far from the inversion line during the impulsive phase. We also made a statistical investigation of the two-ribbon flares observed by TRACE. We find that this progressive decrease in shear of footpoints is a common feature, which appears to indicate that the pre-flare magnetic field configuration of this kind of flare is highly sheared close to, and less sheared far from the magnetic inversion line. Title: The Reconnection and Microscale (RAM) probe Authors: Golub, Leon; Bookbinder, Jay A.; DeLuca, Edward E.; Karpen, Judith T. Bibcode: 2005SPIE.5901..281G Altcode: Hot magnetized plasmas - typified by the solar corona - are ubiquitous throughout the universe. The physics governing the dynamics of such plasmas takes place on remarkably small spatial and temporal scales, while both the cause activity and the response occur on large spatial scales. Thus both high resolution and large fields of view are needed. Observations from SMM, Yohkoh, EIT and TRACE show that typical solar active region structures range in temperature from 0.5 to 10 MK, and up to 40MK in flares, implying the need for broad temperature coverage. The RAM S-T Probe consists of a set of imaging and spectroscopic instruments that will enable definitive studies of fundamental physical processes that govern not only the solar atmosphere but much of the plasma universe. Few problems in astrophysics have proved as resistant to solution as the microphysics that results in the production of high-energy particles in hot magnetized plasmas. Theoretical models have focused in recent years on the various ways in which energy may be transported to the corona, and there dissipated, through the reconnection of magnetic fields. Theory implies that the actual dissipation of energy in the corona occurs in spatially highly localized regions, and there is observational support for unresolved structures with filling factors 0.01 - 0.001 in dynamic coronal events. Title: Calibration of the Solar-B x-ray optics Authors: Cosmo, Mario L.; DeLuca, Edward E.; Golub, Leon; Austin, Gerald K.; Chappell, Jon H.; Barbera, Marco; Bookbinder, Jay A.; Cheimets, Peter N.; Cirtain, Jonathan; Podgorski, William A.; Davis, William; Varisco, Salvatore; Weber, Mark A. Bibcode: 2005SPIE.5900...99C Altcode: The Solar-B X-ray telescope (XRT) is a grazing-incidence modified Wolter I X-ray telescope, of 35 cm inner diameter and 2.7 m focal length. XRT, designed for full sun imaging over the wavelength 6-60 Angstroms, will be the highest resolution solar X-Ray telescope ever flown. Images will be recorded by a 2048 X 2048 back-illuminated CCD with 13.5 μm pixels (1 arc-sec/pixel ) with full sun field of view. XRT will have a wide temperature sensitivity in order to observe and discriminate both the high (5-10 MK) and low temperature (1-5 MK) phenomena in the coronal plasma. This paper presents preliminary results of the XRT mirror calibration performed at the X-ray Calibration Facility, NASA-MSFC, Huntsville, Alabama during January and February 2005. We discuss the methods and the most significant results of the XRT mirror performance, namely: characteristics of the point response function (PSF), the encircled energy and the effective area. The mirror FWHM is 0.8" when corrected for 1-g, finite source distance, and CCD pixelization. With the above corrections the encircled energy at 27 μm and 1keV is 52%. The effective area is greater than 2cm2 at 0.5keV and greater than 1.7cm2 at 1.0keV. Title: Development and testing of EUV multilayer coatings for the atmospheric imaging assembly instrument aboard the Solar Dynamics Observatory Authors: Soufli, Regina; Windt, David L.; Robinson, Jeff C.; Baker, Sherry L.; Spiller, Eberhard; Dollar, Franklin J.; Aquila, Andrew L.; Gullikson, Eric M.; Kjornrattanawanich, Benjawan; Seely, John F.; Golub, Leon Bibcode: 2005SPIE.5901..173S Altcode: We present experimental results on the development and testing of the extreme ultraviolet (EUV) reflective multilayer coatings that will be used in the Atmospheric Imaging Assembly (AIA) instrument. The AIA, comprising four normal incidence telescopes, is one of three instruments aboard the Solar Dynamics Observatory mission, part of NASA's Living with a Star program, currently scheduled for launch in 2008. Seven different multilayer coatings will be used, covering the wavelength region from 93.9 to 335.4 Å. Title: Spicules, mass transfer, oscillations, and the heating of the corona Authors: Pasachoff, J. M.; Kozarev, K. A.; Butts, D. L.; Gangestad, J. W.; Seaton, D. B.; de Pontieu, B.; Golub, L.; Deluca, E.; Wilhelm, K.; Dammasch, I. Bibcode: 2005AGUSMSH13C..02P Altcode: The mass moving in chromospheric spicules is enough to replace the corona in a brief time, so understanding the dynamics of spicules is important for understanding the support and heating of the solar corona. We have undertaken a program involving simultaneous high-resolution observations in various chromospheric visible lines (H-alpha, Ca II H, and G-band, as well as Dopplergrams) using the Swedish Solar Telescope on La Palma, ultraviolet chromospheric, transition-region, and coronal lines (Fe IX/X 171 A, Lyman-alpha 1216 A, and continuum/C I/C IV 1600 A) using NASA's TRACE, and ultraviolet chromospheric and transition-region lines (Si II 1533, C IV 1548, and Ne VIII 770) using SUMER on SOHO. Our first coordinated observing run, in May 2004, yielded a variety of images that are under study, especially for the morphological statistics and dynamics of spicules. The energy transfer through the chromosphere is relevant to the overlapping investigation of coronal heating through rapid (1Hz range) oscillations of coronal loops as observed at total eclipses by Williams College expeditions. This research is supported by NASA grant number NNG04GK44G to Williams College. TRACE analysis at SAO is supported by a contract from Lockheed Martin. SOHO is a project of international cooperation between ESA and NASA. Title: The Atmospheric Imaging Assembly (AIA) investigation for the NASA SDO mission Authors: Lemen, J. R.; Title, A. M.; Golub, L. Bibcode: 2005AGUSMSH43A..17L Altcode: The Atmospheric Imaging Assembly (AIA) is one of three science investigations selected for the NASA Solar Dynamics Observatory, the first mission in NASA's Living With a Star program that is designed to study the Sun's influence on the Earth and the nearby environment. AIA consists of four normal incidence telescopes with multilayer coated optics. It records solar EUV emission with high spatial resolution (0.6 arcsec pixels) at six wavelengths from iron ions in the solar atmosphere at temperatures between 6.3 × 105 K and 15 × 106 K: Fe IX (171Å); Fe XII,XXIV (193Å); Fe XIV (211 Å); Fe XVI (335Å); Fe XVIII (94Å); and Fe XX,XXIII (131Å). Other wavelength channels enable observations of the chromosphere (He II, 304Å; C IV) and the photosphere. Each telescope contains a 16-Mpixel CCD/camera system and has a 41 arcmin field of view. AIA will return 8 full solar-disk images every 10 s, producing 2.2 Tbytes/day of data. The AIA investigation is led by PI Alan Title (LMSAL) with major participation by the Harvard Smithsonian Astrophysical Observatory, Montana State University, and Stanford University. The SDO mission is scheduled for launch in 2008 and will have a nominal five year mission lifetime, but will carry resources for at least ten years of mission operations. Title: The Calibration of the Solar-B X-ray Telescope (XRT) Authors: Golub, L.; Barbera, M.; Bookbinder, J.; Cheimets, P.; Cirtain, J.; Cosmo, M.; Deluca, E.; Podgorski, W.; Sette, A.; Varisco, S.; Weber, M. Bibcode: 2005AGUSMSP43A..01G Altcode: The Solar-B X-ray telescope (XRT) is designed to have a wide temperature sensitivity in order to observe and analyze both the high (5-10 MK) and low temperature (1-5 MK) phenomena in the coronal plasma. It will be the telescope with the highest resolution ever flown for solar coronal studies. The telescope is designed for full Sun imaging over the wavelength range 6-60 Angstroms. The XRT is a grazing-incidence modified Wolter I X-ray telescope, of 35 cm inner diameter and 2.7 m focal length. The 2048 X 2048 back illuminated CCD has 13.5 µm pixels, corresponding to 1 arcsecond. The filter set used in the XRT, mounted at the telescope entrance and near the focal plane, will perform three functions: (1) to reduce the heat load inside the telescope, (2) to reduce the incoming visible light and (3) to provide spectral diagnostics to determine coronal plasma temperatures. This paper will present the results of the XRT calibration performed at the X-ray Calibration Facility, NASA-MSFC, Huntsville, Alabama in January 2005. We will discuss the methods and the most significant results of the XRT performance, namely: imaging properties, encircled energy, the point response function and the effective area in the 0.2-2 keV energy range. Title: EUV Observations of Active Region Dynamics Authors: Deluca, E. E.; Cirtain, J. W.; del Zanna, G.; Mason, H. E.; Martens, P. C.; Schmelz, J.; Golub, L. Bibcode: 2005AGUSMSP33A..03D Altcode: Data collected during SoHO JOP 146, in collaboration with TRACE, is used to investigate the physical characteristics of coronal active region loops as a function of time and position along and across loop structures. These data include TRACE images in all three EUV passbands, and simultaneous CDS spectroscopic observations. Preliminary measurements of the loop temperature both along the loop half-length and loop cross-section are presented as a function of time. We will show the temperature and density profiles of several structures as a function of position, show changes in temperature and density with time and characterize the coronal background emission. Questions raised by these results will be greatly advanced with the high resolution spectra available from the EIS on Solar-B. Title: The black-drop effect explained Authors: Pasachoff, Jay M.; Schneider, Glenn; Golub, Leon Bibcode: 2005tvnv.conf..242P Altcode: 2005IAUCo.196..242P The black-drop effect bedeviled attempts to determine the Astronomical Unit from the time of the transit of Venus of 1761, until dynamical determinations of the AU obviated the need for transit measurements. By studying the 1999 transit of Mercury, using observations taken from space with NASA's Transition Region and Coronal Explorer (TRACE), we have fully explained Mercury's black-drop effect, with contributions from not only the telescope's point-spread function but also the solar limb darkening. Since Mercury has no atmosphere, we have thus verified the previous understanding, often overlooked, that the black-drop effect does not necessarily correspond to the detection of an atmosphere. We continued our studies with observations of the 2004 transit of Venus with the TRACE spacecraft in orbit and with ground-based imagery from Thessaloniki, Greece. We report on preliminary reduction of those data; see http://www.transitofvenus.info for updated results. Such studies are expected to contribute to the understanding of transits of exoplanets. Though the determination of the Astronomical Unit from studies of transit of Venus has been undertaken only rarely, it was for centuries expected to be the best method. The recent 8 June 2004 transit of Venus provided an exceptionally rare opportunity to study such a transit and to determine how modern studies can explain the limitations of the historical observations. Title: Space Studies of the Black-Drop Effect at a Mercury Transit Authors: Schneider, Glenn; Pasachoff, Jay M.; Golub, Leon Bibcode: 2005HiA....13...70S Altcode: The accuracy with which the Astronomical Unit was known has been historically limited by the ""black drop"" effect observed during Venus's rare transits. It is often mistakenly attributed to Venus's atmosphere. We report on observations taken outside the Earth's atmosphere of the 1999 and 2003 transits of Mercury with the NASA solar satellite known as the Transition Region and Coronal Explorer (TRACE). Though there was no contribution from the atmosphere of Mercury or the Earth nevertheless a faint black-drop effect was detected. We discuss and model the images showing the sources of the black-drop effect. The techniques we discuss are applicable to ground-based and space-based observations of the 8 June 2004 and 5-6 June 2012 transits of Venus. Title: Science of the X-ray Sun: The X-ray telescope on Solar-B Authors: DeLuca, E. E.; Weber, M. A.; Sette, A. L.; Golub, L.; Shibasaki, K.; Sakao, T.; Kano, R. Bibcode: 2005AdSpR..36.1489D Altcode: The X-Ray Telescope (XRT) on Solar-B is designed to provide high resolution, high cadence observations of the X-ray corona through a wide range of filters. The XRT science team has identified four general problems in coronal physics as the primary science goals for our instrument. Each of these goals will require collaborative observations from the other Solar-B instruments: EUV Imaging Spectrograph (EIS) and Solar Optical Telescope Focal Plane Package (SOT). We will discuss the science goals and observations needed to address those goals. Title: Differential Emission Measure Reconstruction with the SolarB X-Ray Telescope Authors: Golub, L.; Deluca, E. E.; Sette, A.; Weber, M. Bibcode: 2004ASPC..325..217G Altcode: Two of the main considerations in the design of the SolarB X-Ray Telescope are temperature coverage and discrimination. We describe how these factors enter into the design of XRT, as well as the methods we have developed for producing estimates of emission measures. We analyze model DEMs to evaluate our ability to reconstruct DEMs. Title: SolarB X-Ray Telescope (XRT) Authors: Kano, R.; Hara, H.; Shimojo, M.; Tsuneta, S.; Sakao, T.; Matsuzaki, K.; Kosugi, T.; Golub, L.; Deluca, E. E.; Bookbinder, J. A.; Cheimets, P.; Owens, J. K.; Hill, L. D. Bibcode: 2004ASPC..325...15K Altcode: The Soft X-ray Telescope (XRT) aboard SolarB is a grazing incidence X-ray telescope equipped with 2k × 2k CCD. XRT has 1 arcsec resolution with wide field-of-view of 34 × 34 arcmin. It is sensitive to <1 MK to 30 MK, allowing us to obtain TRACE-like low temperature images as well. Co-alignment with SOT and EIS is realized through the XRT visible light telescope and with temperature overlap with EIS. Spacecraft mission data processor (MDP) controls XRT through the sequence tables with versatile autonomous functions such as exposure control, region-of-interest tracking, flare detection and flare location identification. Data are compressed either with DPCM or JPEG, depending on the purpose. This results in higher cadence and/or wider field-of-view for given telemetry bandwidth. With focus adjust mechanism, higher resolution of Gaussian focus may be available on-axis. Title: Focal plane CCD camera for the X-Ray Telescope (XRT) aboard SOLAR-B Authors: Sakao, Taro; Kano, Ryouhei; Hara, Hirohisa; Matsuzaki, Keiichi; Shimojo, Masumi; Tsuneta, Saku; Kosugi, Takeo; Shibasaki, Kiyoto; Kumagai, Kazuyoshi; Sawa, Masaki; Tamura, Tomonori; Iwamura, Satoru; Nakano, Mitsuhiko; Du, Zhangong; Hiyoshi, Kenji; Horii, Michihiro; Golub, Leon; Bookbinder, Jay A.; Cheimets, Peter C.; Hill, Lawrence D.; Owens, Jerry K. Bibcode: 2004SPIE.5487.1189S Altcode: We present scientific as well as engineering overview of the X-Ray Telescope (XRT) aboard the Japanese Solar-B mission to be launched in 2006, with emphasis on the focal plane CCD camera that employs a 2k x 2k back-thinned CCD. Characterization activities for the flight CCD camera made at the National Astronomical Observatory of Japan (NAOJ) are discussed in detail with some of the results presented. Title: Calibration of the XRT-SOLARB flight filters at the XACT facility of INAF-OAPA Authors: Barbera, Marco; Artale, Maria Antonella; Candia, Roberto; Collura, Alfonso; Lullo, Giuseppe; Peres, Giovanni; Perinati, Emanuele; Varisco, Salvatore; Bookbinder, J. A.; Cheimets, Peter N.; Cosmo, Mario L.; DeLuca, Edward E.; Golub, Leon; Weber, Mark A. Bibcode: 2004SPIE.5488..423B Altcode: The X-Ray Telescope (XRT) experiment on-board the Japanese satellite SOLAR-B (launch in 2006) aimed at providing full Sun field of view at ~ 1.5" angular resolution, will be equipped with two wheels of focal-plane filters to select spectral features of X-ray emission from the Solar corona, and a front-end filter to significantly reduce the visible light contamination. We present the results of the X-ray calibrations of the XRT flight filters performed at the X-ray Astronomy Calibration and Testing (XACT) facility of INAF-OAPA. We describe the instrumental set-up, the adopted measurement technique, and present the transmission vs. energy and position measurements. Title: Calibration of the XRT-SOLARB flat mirror samples at the XACT Facility of INAF-OAPA Authors: Artale, Maria Antonella; Barbera, Marco; Collura, Alfonso; Di Cicca, Gaspare; Peres, Giovanni; Varisco, Salvatore; Bookbinder, J. A.; Cheimets, Peter N.; Cosmo, Mario L.; DeLuca, Edward E.; Golub, Leon; Weber, Mark A. Bibcode: 2004SPIE.5488..440A Altcode: The X-Ray Telescope (XRT) experiment on-board the Japanese satellite SOLAR-B (launch in 2006) is equipped with a modified Wolter I grazing incidence X-ray telescope (focal length 2700 mm) to image the full Sun at ~ 1.5" angular resolution onto a 2048 x 2048 back illuminated CCD focal plane detector. The X-ray telescope consisting of one single reflecting shell is coated with ion beam sputtered Iridium over a binding layer of Chromium to provide nearly 5 square centimetres effective area at 60 Å. We present preliminary results of X-ray calibrations of the XRT flat mirror samples performed at the X-ray Astronomy Calibration and Testing (XACT) facility of INAF-OAPA. We describe the instrumental set-up, the adopted measurement technique, and present the measured reflectivity vs. angle of incidence at few energies. Title: The August 11th, 1999 CME Authors: Koutchmy, S.; Baudin, F.; Bocchialini, K.; Daniel, J. -Y.; Delaboudinière, J. -P.; Golub, L.; Lamy, P.; Adjabshirizadeh, A. Bibcode: 2004A&A...420..709K Altcode: We present here a set of observations, space borne and ground based, at different wavelengths, of the solar corona at and after the time of the total solar eclipse of August 11{th}. It is used to consider some unusual features of the coronal dynamics related to a limb Coronal Mass Ejection (CME) observed after the total eclipse. The complementary aspect of simultaneous ground-based and space-borne observations of the corona is used to produce an accurate composite image of the White Light (W-L) corona before the CME. A high arch system (possibly a dome-like structure, with large cavities inside but without a cusp further out) which appeared on the eclipse W-L images, is suggested to be a large-scale precursor of the CME, well preceding the eruption of the top part of the brightest prominence recorded in W-L. This bright prominence is shown as a filament in absorption using the Transition Region And Corona Explorer (TRACE) images taken in different coronal lines. The analysis of the images of the Large Angle and Spectrometric Coronograph (LASCO) on board the Solar and Heliospheric Observatory (SoHO), showing the progression of the CME, is discussed in an attempt to make a connection with the surface event. A SoHO-EIT (Extreme UV Imager Telescope) image sequence details the prominence eruption and shows the sudden heating processes of the ejected parts. We found that there is no reason to assume that the huge cavity is significantly destabilised well before the eruption of the upper part of the low-lying bright twisted filament which coincides with the position of one of the legs of the high arch. Observations are still compatible with the assumption of both the break-out model and of the flux rope erupting model as a result of a shear or of an increasing poloıdal magnetic flux from below. We stress the possible role of buoyancy of the giant cavity as a destabilizing factor leading to the CME, noticing that some motion of coronal material back toward the surface can be seen during at least the first phase of the CME, from both EIT and LASCO observations. Title: Pre-Conditioning Optmization Methods and Display for Mega-Pixel DEM Reconstructions Authors: Sette, A. L.; DeLuca, E. E.; Weber, M. A.; Golub, L. Bibcode: 2004AAS...204.6904S Altcode: 2004BAAS...36R.794S The Atmospheric Imaging Assembly (AIA) for the Solar Dynamics Observatory will provide an unprecedented rate of mega-pixel solar corona data. This hastens the need for faster differential emission measure (DEM) reconstruction methods, as well as scientifically useful ways of displaying this information for mega-pixel datasets. We investigate pre-conditioning methods, which optimize DEM reconstruction by making an informed initial DEM guess that takes advantage of the sharing of DEM information among the pixels in an image. In addition, we evaluate the effectiveness of different DEM image display options, including single temperature emission maps and time-progression DEM movies.

This work is supported under contract SP02D4301R to the Lockheed Martin Corp. Title: The Atmospheric Imaging Assembly and Temperature Diagnostics Authors: Weber, M. A.; Caldwell, D.; Deluca, E. E.; Golub, L.; Sette, A. L. Bibcode: 2004AAS...204.6906W Altcode: 2004BAAS...36..795W The Atmospheric Imaging Assembly (AIA) will be one of the instruments on the Solar Dynamics Observatory (SDO). It will image the solar transition region and corona in multiple EUV and UV wavelengths simultaneously, using four aligned telescopes. Hence, AIA will be capable of high-cadence, spatially resolved temperature discrimination of solar plasmas. We discuss the design of AIA, with focus on its ability for temperature diagnostics. We consider different methods for reconstruction of differential emission measures, since this will be one of the more important data products.

This work is supported under contract SP02D4301R to the Lockheed Martin Corp. Title: Science with the Solar-B X-Ray Telescope Authors: Deluca, E. E.; Weber, M. A.; Golub, L. Bibcode: 2004AAS...204.6905D Altcode: 2004BAAS...36Q.795D The Solar-B mission will launch in 2006 with three telescopes: a high resolution visible light telescope feeding filtergraph and spectropolarimeter focal plane instruments, a grazing incidence X-Ray telescope and an EUV spectrograph. This combination of instruments will provide detailed information on Active Region evolution, heating, connectivity and dynamics. The X-Ray telescope on Solar-B will be sensitive to emission from 1-50MK. Focal plane filters will allow us to follow the evolution of the bulk of the coronal plasma. This poster will describe the core science that will be done by XRT together with EIS and SOT. Joint observing programs will also be discussed. Title: TRACE observations of the 15 November 1999 transit of Mercury and the Black Drop effect: considerations for the 2004 transit of Venus Authors: Schneider, Glenn; Pasachoff, Jay M.; Golub, Leon Bibcode: 2004Icar..168..249S Altcode: Historically, the visual manifestation of the "Black Drop effect," the appearance of a band linking the solar limb to the disk of a transiting planet near the point of internal tangency, had limited the accuracy of the determination of the Astronomical Unit and the scale of the Solar System in the 18th and 19th centuries. This problem was misunderstood in the case of Venus during its rare transits due to the presence of its atmosphere. We report on observations of the 15 November 1999 transit of Mercury obtained, without the degrading effects of the Earth's atmosphere, with the Transition Region and Coronal Explorer spacecraft. In spite of the telescope's location beyond the Earth's atmosphere, and the absence of a significant mercurian atmosphere, a faint Black Drop effect was detected. After calibration and removal of, or compensation for, both internal and external systematic effects, the only radially directed brightness anisotropies found resulted from the convolution of the instrumental point-spread function with the solar limb-darkened, back-lit, illumination function. We discuss these effects in light of earlier ground-based observations of transits of Mercury and of Venus (also including the effects of atmospheric "seeing") to explain the historical basis for the Black Drop effect. The methodologies we outline here for improving upon transit imagery are applicable to ground-based (adaptive optics augmented) and space-based observations of the 8 June 2004 and 5-6 June 2012 transits of Venus, providing a path to achieving high-precision measurements at and near the instants of internal limb tangencies. Title: EUV multilayers for solar physics Authors: Windt, David L.; Donguy, S.; Seely, John F.; Kjornrattanawanich, Benjawan; Gullikson, Eric M.; Walton, C. C.; Golub, L.; DeLuca, E. Bibcode: 2004SPIE.5168....1W Altcode: We present an overview of currently available EUV multilayer coatings that can be used for the construction of solar physics instrumentation utilizing normal-incidence optics. We describe the performance of a variety of Si-based multilayers, including Si/B4C and new Si/SiC films that provide improved performance in the wavelength range from 25 n 35 nm, as well as traditional Si/Mo multilayers, including broad-band coatings recently developed for the Solar-B/EIS instrument. We also outline prospects for operation at both longer and shorter EUV wavelengths, and also the potential of ultra-short-period multilayers that work near normal incidence in the soft X-ray region. Title: New dimensions in coronal studies from the XRT on Solar-B Authors: Golub, L. Bibcode: 2004cosp...35.4419G Altcode: 2004cosp.meet.4419G The X-ray Telescope (XRT) on Solar-B will be the highest resolution telescope ever flown in space for solar coronal observations. It will have full Sun coverage with 1.0 arcsec pixel resolution, and extended low and high temperature coverage. The onboard data storage and high telemetry rate will provide excellent image cadence and also the ability to observe in flare mode, so that high cadence pre-flare data can be retained when a flare occurs. The full range of coronal targets, from coronal holes and bright points, to active regions and flares up to X-level in brightness can be observed. The polar orbit will permit long periods of continuous coverage for the first time in a soft x-ray imaging instrument. Title: Temperature diagnostics with multichannel imaging telescopes Authors: Weber, M. A.; Deluca, E. E.; Golub, L.; Sette, A. L. Bibcode: 2004IAUS..223..321W Altcode: 2005IAUS..223..321W Modern solar telescope design in the EUV to x-ray range is now capable of producing large images in multiple channels at rapid cadences, with high spatial and temperature resolution. We discuss reconstruction of differential emission measures for solar coronal plasma using two state-of-the-art instruments: the X-Ray Telescope on Solar-B, and the Atmospheric Imaging Assembly on the Solar Dynamics Observatory. We discuss the relative merits of iteration and direct inversion methods for determining DEM(T). We also consider strategies for automating and visualizing DEM maps, given the high data rates that these instruments will produce. We touch on the scientific potential of high-cadence, spatially resolved DEM data products. Title: Explanation of the Black-Drop Effect at Transits of Mercury and the Forthcoming Transit of Venus Authors: Pasachoff, J. M.; Schneider, G.; Golub, L. Bibcode: 2003AAS...203.0104P Altcode: 2003BAAS...35.1202P We used the observations of the transits of Mercury of 1999 and 2003 taken with NASA's Transition Region and Coronal Explorer (TRACE) solar spacecraft. For the 1999 Mercury transit, for which data were acquired with the highest digital fidelity available for TRACE, we detected a black-drop effect, in spite of the facts that we were observing from outside the Earth's atmosphere and that Mercury has no significant atmosphere. We were able to show that the Mercury black-drop effect comes from a convolution of the instrument's point-spread function and the solar limb darkening. By implication, we should be able to explain Venus's black-drop effect in a similar way. It has long been known that Venus's black-drop effect is too large to come from Venus's atmosphere. Title: Solar observation from space Authors: Golub, Leon Bibcode: 2003RScI...74.4583G Altcode: Solar observations are carried out in space when necessary for technical reasons, such as detection of wavelengths that do not reach the ground, or to provide observing conditions that are difficult or impossible to achieve on the ground. Examples in the first category are observations at far ultraviolet or soft x-ray wavelengths and direct detection of solar wind particles; in the latter are precise measurements of variations in the solar luminosity and stereo observations of coronal mass ejections. This article samples the wide variety of techniques presently being used to study the Sun. We begin with an overview of the observational problem presented by the particular scientific questions involved in improving our understanding of the Sun, and of solar activity in particular. We then discuss the need for and advantages of observations from space, and give examples of scientific objectives which can only be met by such observations. We then describe in detail some representative examples of space missions and specific space-based experiments for solar studies. Title: Book review: The century of space science / Johan A. M. Bleeker, Johannes Geiss, Martin C. E. Huber (eds.), Kluwer Academic Publ., Dordrecht, The Netherlands, XIV + 1846 pp., 2001, ISBN 0-7923-7196-8. Authors: Golub, Leon Bibcode: 2003JHA....34..461G Altcode: No abstract at ADS Title: The Dynamical Morphologies of Flares Associated with the Two Types of Solar Coronal Mass Ejections Authors: Zhang, Mei; Golub, Leon Bibcode: 2003ApJ...595.1251Z Altcode: In this paper we study the high-cadence TRACE observations of a sample of 28 X- and M-class flares, with particular focus on the relation between flare morphology and the two types (fast and slow) of solar coronal mass ejections (CMEs). Among the 28 flares studied, 10 are associated with fast CMEs, 10 are associated with slow CMEs, and 8 are loosely associated with a CME. We find that flares associated with fast and slow CMEs show different morphologies as groups. While all flares associated with fast CMEs show clear footpoint-separating, two-ribbon brightenings during the flare, this feature is less often seen in flares associated with slow CMEs or flares without CMEs. Meanwhile, while flares associated with slow CMEs sometimes show tubular emission structures during the flare, this feature is not found in our sample of flares associated with fast CMEs. This observational result suggests that the morphologies of flares, and hence possibly the magnetic field topologies, are different for events associated with fast and with slow CMEs. Title: Space Studies of the Black-Drop Effect at a Mercury Transit Authors: Schneider, G.; Pasachoff, J. M.; Golub, L. Bibcode: 2003astro.ph.10379S Altcode: Transits of Mercury and Venus across the face of the Sun are rare. The 20th century had 15 transits of Mercury and the 21st century will have 14, the two most recent occuring on 15 November 1999 and 7 May 2003. We report on our observations and analyses of a black-drop effect at the 1999 and 2003 transits of Mercury seen in high spatial resolution optical imaging with NASA's Transition Region and Coronal Explorer (TRACE) spacecraft. We have separated the primary contributors to this effect, solar limb darkening and broadening due to the instrumental point spread function, for the 1999 event. The observations are important for understanding historical observations of transits of Venus, which in the 18th and 19th centuries were basic for the determination of the scale of the solar system. Our observations are in preparation for the 8 June 2004 transit of Venus, the first to occur since 1882. Only five transits of Venus have ever been seen -- in 1639, 1761, 1769, 1874, and 1882. These events occur in pairs, whose members are separated by 8 years, with an interval between pairs of 105 or 122 years. Nobody alive has ever seen a transit of Venus. Title: Constraints on Active Region Coronal Heating Authors: Antiochos, S. K.; Karpen, J. T.; DeLuca, E. E.; Golub, L.; Hamilton, P. Bibcode: 2003ApJ...590..547A Altcode: We derive constraints on the time variability of coronal heating from observations of the so-called active region moss by the Transition Region and Coronal Explorer (TRACE). The moss is believed to be due to million-degree emission from the transition regions at the footpoints of coronal loops whose maximum temperatures are several million degrees. The two key results from the TRACE observations discussed in this paper are that in the moss regions one generally sees only moss, not million-degree loops, and that the moss emission exhibits only weak intensity variations, ~10% over periods of hours. TRACE movies showing these results are presented. We demonstrate, using both analytic and numerical calculations, that the lack of observable million-degree loops in the moss regions places severe constraints on the possible time variability of coronal heating in the loops overlying the moss. In particular, the heating in the hot moss loops cannot be truly flarelike with a sharp cutoff, but instead must be quasi-steady to an excellent approximation. Furthermore, the lack of significant variations in the moss intensity implies that the heating magnitude is only weakly varying. The implications of these conclusions for coronal heating models will be discussed. Title: Propagating EUV disturbances in the Solar corona: Two-wavelength observations Authors: King, D. B.; Nakariakov, V. M.; Deluca, E. E.; Golub, L.; McClements, K. G. Bibcode: 2003A&A...404L...1K Altcode: Quasi-periodic EUV disturbances simultaneously observed in 171 Å and 195 Å TRACE bandpasses propagating outwardly in a fan-like magnetic structure of a coronal active region are analysed. Time series of disturbances observed in the different bandpasses have a relatively high correlation coefficient (up to about 0.7). The correlation has a tendency to decrease with distance along the structure: this is consistent with an interpretation of the disturbances in terms of parallel-propagating slow magnetoacoustic waves. The wavelet analysis does not show a significant difference between waves observed in different bandpasses. Periodic patterns of two distinct periods: 2-3 min and 5-8 min are detected in both bandpasses, existing simultaneously and at the same distance along the loop, suggesting the nonlinear generation of the second harmonics. Title: The High Resolution Imager on the Reconnection and Microscale (RAM) Mission Authors: Bookbinder, J. A.; DeLuca, E. E.; Golub, L.; Weber, M.; Karpen, J. T. Bibcode: 2003SPD....34.2404B Altcode: 2003BAAS...35..853B Hot, magnetized plasmas such as the solar corona have the property that much of the physics governing its activity takes place on remarkably small spatial and temporal scales, while the response to this activity occurs on large scales. Future progress on the challenging solar physics issues of eruptive flares, coronal heating and the initial of the solar wind requires observations on spatial and temporal scales relevant to the observable signatures of the underlying physical processes. These spatial and temporal domains - in the relevant temperature regimes - have been heretofore inaccessible to direct observations from Earth, with the result that theoretical efforts have relied heavily on extrapolations from more accessible regimes.

The RAM Solar-Terrestrial Probe consists of a set of carefully selected imaging and spectroscopic instruments that enable definitive studies of the dynamics and energetics of the solar corona. We present an overview of the synergism inherent in the RAM instrument suite, with emphasis on the rationale for, and the capability of, its high-resolution imager. Title: The Reconnection And Microscale (RAM) Solar-Terrestrial Probe Authors: Bookbinder, Jay A.; DeLuca, Edward; Cheimets, Peter; Golub, Leon; Hassler, Donald M.; Korendyke, Clarence M.; Glenn, Paul E.; Silver, Eric H. Bibcode: 2003SPIE.4853..436B Altcode: A hot, magnetized plasma such as the solar corona has the property that much of the physics governing its activity takes place on remarkably small spatial and temporal scales, while the response to this activity occurs on large scales. Observations from SMM, TRACE, SOHO and Yohkoh have shown that typical solar active regions have loops ranging in temperature from 0.5 to 10 MK, and flares up to 40MK. The spatial and temporal domains involved have been heretofore inaccessible to direct observations from Earth, so that theory has relied heavily on extrapolations from more accessible regimes, and on speculation. The RAM Solar-Terrestrial Probe consists of a set of carefully selected imaging and spectroscopic instruments that enable definitive studies of the dynamics and energetics of the solar corona. Title: Space Studies of the Black Drop Effect at a Mercury Transit Authors: Pasachoff, Jay M.; Schneider, Glenn; Golub, Leon Bibcode: 2003IAUJD...2E...5P Altcode: The accuracy with which the Astronomical Unit was known has been historically limited by the ""black drop"" effect observed during Venus's rare transits. It is often mistakenly attributed to Venus's atmosphere. We report on observations taken outside the Earth's atmosphere of the 1999 and 2003 transits of Mercury with the NASA solar satellite known as the Transition Region and Coronal Explorer (TRACE). Though there was no contribution from the atmosphere of Mercury or the Earth nevertheless a faint black-drop effect was detected. We discuss and model the images showing the sources of the black-drop effect. The techniques we discuss are applicable to ground-based and space-based observations of the 8 June 2004 and 5-6 June 2012 transits of Venus. Title: The Timing of Flares Associated with the Two Dynamical Types of Solar Coronal Mass Ejections Authors: Zhang, M.; Golub, L.; DeLuca, E.; Burkepile, J. Bibcode: 2002ApJ...574L..97Z Altcode: In this Letter, we consider a sample of Transition Region and Coronal Explorer flare-associated solar coronal mass ejections (CMEs) and study the timing behavior of the flares associated with fast or slow CMEs. We find that flares associated with fast CMEs tend to happen within half an hour of the CME onsets, while the timing of flares associated with slow CMEs is only loosely related to the CME onsets. This suggests that the occurrence of flares may be integral to the early development of fast CMEs but is not crucial for slow CMEs. This observational result supports a recent qualitative theory of the initiation and expulsion mechanism of the two dynamical types of CMEs. Title: Active Region Loop Heating Authors: Antiochos, S. K.; Karpen, J. T.; DeLuca, E. E.; Golub, L.; Hamilton, P. Bibcode: 2002AAS...200.1606A Altcode: 2002BAAS...34..668A A long-standing unresolved question in solar physics is whether the heating in coronal loops is steady or impulsive. X-ray observations of high-temperature loops (T > 2 x 106 K) tend to show quasi-steady structures, (evolution slow compared to cooling time scales), whereas theoretical models strongly favor impulsive heating. We present simulations of impulsively heated loops using our adaptive-mesh-refinement code ARGOS, and compare the results with TRACE observations of the transition regions of high-temperature active region loops. From this comparison, we deduce that the heating in the core of active regions is quasi-steady rather than impulsive. These results pose a formidable challenge to developing theoretical models for the heating. This work was supported in part by NASA and ONR. Title: The Reconnection and Microscale (RAM) Mission Authors: Bookbinder, J. A.; DeLuca, E. E.; Golub, L. Bibcode: 2002AAS...200.5609B Altcode: 2002BAAS...34Q.736B Hot magnetized plasmas - typified by the solar corona - are ubiquitous throughout the universe. The physics governing the dynamics of such plasmas takes place on remarkably small spatial and temporal scales, while both the cause activity and the response occur on large spatial scales. Thus both high resolution and large fields of view are needed. Observations show that typical solar active region structures range in temperature from 0.5 to 10 MK, and up to 40 MK in flares, implying the need for broad temperature coverage. The RAM mission is designed to meet the observational requirements of the next generation Solar observatory; we present an overview of the proposed ST-Probe class mission concept, instrument complement, and technology status. We emphasize the capabilities and status of the instrument suite that is proposed: a set of imaging and spectroscopic instruments that will enable definitive studies of fundamental physical processes that govern not only the solar atmosphere but much of the plasma universe. The imaging instruments on RAM combine extremely high spatial resolution in the corona ( ~10 km) with intermediate scale ( ~70 km) large FOV observations at several complementary passbands/temperatures. The spectroscopic instruments offer high resolution ( ~70 km spatial, ~5 km/s velocity) imaging EUV spectroscopy and a photon counting imaging X-ray micro-calorimeter array offers ( ~700 km, 2 eV energy, ~10 msec time) over a bandpass from 0.2 to >40 keV. Title: Science Objectives of the Reconnection and Micrcoscale (RAM) Solar-Terrestrial Probe Authors: DeLuca, E. E.; Bookbinder, J.; Golub, L. Bibcode: 2002AAS...200.8801D Altcode: 2002BAAS...34..789D The RAM mission is designed to address fundamental questions related to the origin and dynamics of hot magnetized plasmas throughout the universe. Observations of the solar corona demonstrate that the important physical processes take place on small spatial and temporal scales, while the energy driving these processes is stored on large scales, and the response can affect the global structure of the corona. In this talk we discuss the theoretical and observational evidence for the existence of small-scale coronal structures, and outline the observational requirements to answer the following fundamental questions that apply to all coronal plasmas: (1) What are the conditions that lead to magnetic reconnection? (2) What micro-scale instabilities lead to global effects? (3) Where are the regions of particle acceleration? (4) Where are the reconnection regions and what is their topology? A companion poster will present the baseline instrument complement that will achieve these observational requirements. Title: A photometric imaging solar telescope, tunable in the extreme ultraviolet, utilizing multilayer x-ray optics Authors: Golub, L.; Deluca, E.; Hamilton, P.; Nystrom, G.; Windt, D. L.; Schmidt, W. K. H.; Dannenberg, A. Bibcode: 2002RScI...73.1908G Altcode: We present a new instrument for space-based observational solar physics, recently flown successfully on a sounding rocket, designed to provide high spatial resolution, time-resolved images of the solar corona at specific wavelengths in the extreme ultraviolet (XUV). The primary instrument employs multilayer x-ray mirrors in a novel geometry that affords quasi-monochromatic imaging at wavelengths tunable continuously over the spectral range from 17.1 to 21.1 nm. The secondary instrument also uses multilayer x-ray mirrors to provide high-resolution imaging at three fixed XUV wavelength bands. Both instruments use charge coupled device detectors and thin A1 filters for rejection of unwanted wavelengths. We describe the design, construction, and performance of the instrument and discuss prospects for the future. Title: A New View of the Solar Corona from TRACE Authors: Golub, Leon Bibcode: 2002smra.progE...5G Altcode: No abstract at ADS Title: Steady Flows Detected in Extreme-Ultraviolet Loops Authors: Winebarger, Amy R.; Warren, Harry; van Ballegooijen, Adriaan; DeLuca, Edward E.; Golub, Leon Bibcode: 2002ApJ...567L..89W Altcode: Recent Transition Region and Coronal Explorer (TRACE) observations have detected a class of active region loops whose physical properties are inconsistent with previous hydrostatic loop models. In this Letter we present the first co-aligned TRACE and the Solar Ultraviolet Measurement of Emitted Radiation (SUMER) observations of these loops. Although these loops appear static in the TRACE images, SUMER detects line-of-sight flows along the loops of up to 40 km s-1. The presence of flows could imply an asymmetric heating function; such a heating function would be expected for heating that is proportional to (often asymmetric) footpoint field strength. We compare a steady flow solution resulting from an asymmetric heating function to a static solution resulting from a uniform heating function in a hypothetical coronal loop. We find that the characteristics associated with the asymmetrically heated loop better compare with the characteristics of the loops observed in the TRACE data. Title: Nearest star: The surprising science of our Sun Authors: Golub, Leon; Pasachoff, Jay M.; O'Connell, James Bibcode: 2002PhTea..40..127G Altcode: No abstract at ADS Title: Imaging solar coronal structures with TRACE Authors: Golub, L. Bibcode: 2002cosp...34E.131G Altcode: 2002cosp.meetE.131G The Transition Region and Coronal Explorer (TRACE) is revealing previously unknown structure and dynamics in the solar outer atmosphere. Extremely fine threads of emission are ubiquitous, and they are mostly inconsistent with the density and temperature structure predicted by standard hydrostatic models of closed loops. Unequal heating at the footpoints induces flows in the corona which in turn accounts for the observed properties of these structures. Detailed comparison of the footpoints with high resolution surface magnetic field observations indicates that the hot coronal plasma is not confined by the coronal magnetic field, although it is constrained by the field. Title: Magnetic structure and reconnection of x-ray bright points in the solar corona Authors: Brown, D. S.; Parnell, C. E.; DeLuca, E. E.; McMullen, R. A.; Golub, L.; Priest, E. R. Bibcode: 2002AdSpR..29.1093B Altcode: The three-dimensional magnetic topology of the solar corona is incredibly complex and its effect on the nature of 3D reconnection is profound. We study the supposedly simple topology of a small scale X-ray bright point observed by TRACE and SOHO/MDI, and how it is driven by reconnection when it forms and during the early stages of its lifetime. Title: High resolution coronal imaging with multilayers Authors: Golub, L.; Hassler, D. M. Bibcode: 2002AdSpR..29.1999G Altcode: Since the 1960s, when on-disk coronal imaging became possible, progress in the field has consisted largely in improving the spectral spatial and temporal resolution of the observations. With the development of normal-incidence, soft X-ray and XUV multilayer optics in the 1980s, a dramatic improvement in the first two of these occurred, and with the development of better detectors the temporal resolution (along with the sensitivity) also improved. In this paper we discuss recent results from The Transition Region and Coronal Explorer ( TRACE), which is providing observations of the solar outer atmosphere with unprecedented spatial and temporal resolution. The new views of coronal structure and dynamics being obtained indicate that: (i) the corona is filled with flows of both hot and cool material, (ii) instead of "loops," the basic coronal structures are threads, and (iii) threads of hot plasma appear to form as parallel bundles on surfaces, which may correspond to dissipation at quasi-separatrix layers. We conclude with a discussion of the possible next generation of high resolution missions. Title: On the Time Variability of Coronal Heating Authors: Antiochos, S. K.; Karpen, J. T.; DeLuca, E. E.; Golub, L.; Hamilton, P. Bibcode: 2001AGUFMSH11A0690A Altcode: We derive constraints on the time variability of coronal heating from observations of the so-called active-region moss by the Transition and Coronal Explorer (TRACE). The moss is believed to be due to million-degree emission from the transition regions at the footpoints of coronal loops whose maximum temperatures are several million degrees. The key point of the TRACE observations is that in the moss regions one generally sees only moss, and not million degree loops. TRACE movies showing this result will be presented. We will demonstrate using both analytic and numerical calculations, that the lack of observable million-degree loops in the moss regions places severe constraints on the possible time variability of coronal heating in the loops overlying the moss. In particular, the heating in the hot moss loops cannot be truly flare-like with a sharp cutoff, but instead, must be quasi-steady to an excellent approximation. The implications of this result for coronal heating models will be discussed. This work was supported in part by NASA and ONR Title: Impulsive Events and Coronal Loop Cooling Observed with TRACE Authors: Seaton, D. B.; DeLuca, E. E.; Golub, L.; Reeves, K. K.; Winebarger, A. R.; Gallagher, P. T. Bibcode: 2001AGUFMSH11A0705S Altcode: Nearly every active region imaged by TRACE contains sporadic brightenings in coronal loops. Many of these ubiquitous, short-lived events appear nearly simultaneously in the Fe IX/X (log T e≈ 6.0) and the C IV channel (log T≈ 5.0); hence, we interpret them as the rapid cooling of a multifilament loops. A particularly good example of such an event was observed on 21, June 2001, as part of an hour long active region observation; a total of 52 of the TRACE 171 Å and 68 TRACE 1600 Å images have been analyzed from that sequence, as well as 35 images provided by the MDI aboard SOHO. In this poster, we will discuss the analysis of the events and the implications of our cooling model. Title: Active Region Transient Events Observed with TRACE Authors: Seaton, Daniel B.; Winebarger, Amy R.; DeLuca, Edward E.; Golub, Leon; Reeves, Katharine K.; Gallagher, Peter T. Bibcode: 2001ApJ...563L.173S Altcode: Nearly all active region observations made by the Transition Region and Coronal Explorer (TRACE) contain seemingly spontaneous, short-lived brightenings in small-scale loops. In this paper, we present an analysis of these brightenings using high-cadence TRACE observations of Active Region 9506 on 2001 June 21 from 15:17:00 to 15:46:00 UT. During this time frame, several brightenings were observed over a neutral line in a region of emerging flux that had intensity signatures in both the 171 Å (logTe~6.0) and 1600 Å (logTe~4.0-5.0) channels. The events had a cross-sectional diameter of approximately 2" and a length of 25". We interpret these as reconnection events associated with flux emergence, possible EUV counterparts to active region transient brightenings. Title: TRACE Observations of the 15 November 1999 Transit of Mercury Authors: Schneider, G.; Pasachoff, J. M.; Golub, L. Bibcode: 2001DPS....33.1002S Altcode: 2001BAAS...33.1037S We present time-resolved (38s) high-resolution (500mas) imagery of the ingress phase of the 15 November 1999 transit of Mercury observed with the Transition Region Coronal Explorer (TRACE) spacecraft in its "white light" (1600 - 6000 Angstrom) channel. As part of our photometric and astrometic analyses of this data set we examined the images in and around the point of internal tangency for evidence of the historical "black drop effect". After calibration (including careful removal of image/instrumental artifacts and flat-fielding) the only radially directed brightness anisotropes found were due to the interacting effects the back-light solar limb-darkening, diffraction of photospheric light around the Mercurian disk, and the instrument's Point Spread Function. We discuss, and model, these effects as they would have applied to earlier ground-based observations of Mercurian transits (also including the effects of atmospheric "seeing") to explain the historical basis for the black drop effect. Title: Nearest Star: The Surprising Science of Our Sun Authors: Golub, Leon; Pasachoff, Jay M.; Lopez, Ramon E. Bibcode: 2001PhT....54k..59G Altcode: No abstract at ADS Title: The Magnetic Structure of a Coronal X-Ray Bright Point Authors: Brown, D. S.; Parnell, C. E.; Deluca, E. E.; Golub, L.; McMullen, R. A. Bibcode: 2001SoPh..201..305B Altcode: X-ray bright points are small dynamic loop structures that are observed all over the solar corona. The high spatial and temporal resolution of the TRACE instrument allows bright points to be studied in much greater detail than previously possible. This paper focuses on a specific bright point which occurred for about 20 hours on 13-14 June 1998 and examines its dynamic structure in detail. This example suggests that the mechanisms that cause bright points to form and evolve are more complex than previously thought. In this case, reconnection probably plays a major part during the formation and brightening of the loop structure. However, later on the foot points rotate injecting twist into the bright point which may cause an instability to occur with dynamic results. Title: Science Objectives of the Solar B X-Ray Telescope Authors: DeLuca, E. E.; Golub, L.; Bookbinder, J. Bibcode: 2001AGUSM..SH31D04D Altcode: The X-Ray Telescope (XRT) on the Solar B Mission will set a new standard for high resolution full disk imaging of hot solar coronal plasma. The optimized grazing incidence optic will have more than twice the resolution of Yohkoh's SXT, a wider temperature response and much less scatter. We will present the expected instrument performance, describe the science objectives, and review sample observing plans for the XRT. Title: Apparent Flows above an Active Region Observed with the Transition Region and Coronal Explorer Authors: Winebarger, Amy R.; DeLuca, Edward E.; Golub, Leon Bibcode: 2001ApJ...553L..81W Altcode: The Transition Region and Coronal Explorer (TRACE) observed Active Region 8395 on 1998 December 1 from 1:30:00 to 3:00:00 UT at high cadence in the Fe IX/Fe X channel (logTe~6.0). Throughout the observing time, brightness variations along a dense bundle of coronal field lines in the southwest corner of the active region were observed. Movies made of this region give the impression of continuous intermittent outflow in this bundle of coronal loops; such apparent outflow is often seen in the TRACE data. In this Letter, we present an analysis of four separate flow events occurring in three different loops. These events are used as tracers of the flow in order to characterize its physical properties, such as apparent velocity. The projected velocities of the intensity fronts of these flows (and hence lower limits of true velocities) are between 5 and 20 km s-1. Comparisons of the observed intensities with those predicted by a quasi-static model suggest that the events can be explained only by a mass flow from the chromosphere into the corona. The persistence of the flows, and their ubiquity in the TRACE observations, indicates that hydrostatic loops models are not applicable to this class of coronal structures. Title: Recent Results from TRACE (CD-ROM Directory: contribs/golub) Authors: Golub, L. Bibcode: 2001ASPC..223..325G Altcode: 2001csss...11..325G No abstract at ADS Title: Nearest star : the surprising science of our sun Authors: Golub, Leon; Pasachoff, Jay M. Bibcode: 2001nsss.book.....G Altcode: No abstract at ADS Title: High-resolution grazing incidence telescope for the Solar-B observatory Authors: Golub, Leon; DeLuca, Edward E.; Bookbinder, Jay A.; Cheimets, Peter; Shibasaki, Kiyoto; Sakao, Taro; Kano, Ryouhei Bibcode: 2000SPIE.4139..313G Altcode: The X-ray observations from the Yohkoh SXT provided the greatest step forward in our understanding of the solar corona in nearly two decades. We believe that the scientific objectives of the Solar-B mission can best be achieved with an X-ray telescope (XRT) similar to the SXT, but with significant improvements in spatial resolution and in temperature response that take into account the knowledge gained from Yohkoh. We present the scientific justification for this view, discuss the instrumental requirements that flow from the scientific objectives, and describe the instrumentation that will meet these requirements. XRT is a grazing-incidence (GI) modified Wolter I X-ray telescope, of 35 cm inner diameter and 2.7 m focal length. The 2048 X 2048 back-illuminated CCD has 13.5 (mu) pixels, corresponding to 1.0 arcsec and giving full Sun field of view. This will be the highest resolution GI X-ray telescope ever flown for Solar coronal studies, and it has been designed specifically to observe both the high and low temperature coronal plasma. Title: Solar Spectroscopy and Diagnostics: X-ray Emission Authors: Golub, L. Bibcode: 2000eaa..bookE2234G Altcode: X-ray emission from the Sun arises primarily from the solar outer atmosphere, particularly the hot corona. During transient events, such as flares and coronal mass ejections, there is also enhanced emission of both soft and hard x-rays from plasma above ten million kelvins (see SOLAR FLARES: RELATION TO CORONAL MASS EJECTIONS). Outside of flares, the bulk of the coronal plasma is at temperatures ... Title: Determination of Flare Heating and Cooling Using the Transition Region and Coronal Explorer Authors: Antiochos, S. K.; DeLuca, E. E.; Golub, L.; McMullen, R. A. Bibcode: 2000ApJ...542L.151A Altcode: We describe how the Transition Region and Coronal Explorer 171 Å observations can be used to determine the properties of flare-loop heating. The key point is that the evolution of a loop transition region (TR) is much easier to measure quantitatively than the bulk flare plasma because the TR emission originates from an unobscured source with simple geometry. We derive general analytic expressions for the evolution of a flare-loop TR that, in principle, permit a determination of the heating function from the observations. These results are compared with observations of the 1998 September 20 flare. We find that the observed evolution of the flare ribbons is in good agreement with our model for the evaporative cooling of flare loops and that the heating in these loops is incompatible with the assumption of spatial uniformity. Title: The Topology and Evolution of the Bastille Day Flare Authors: Aulanier, G.; DeLuca, E. E.; Antiochos, S. K.; McMullen, R. A.; Golub, L. Bibcode: 2000ApJ...540.1126A Altcode: On 1998 July 14, a class M3 flare occurred at 12:55 UT in AR 8270 near disk center. Kitt Peak line-of-sight magnetograms show that the flare occurred in a δ spot. Mees vector magnetograms show a strong shear localized near a portion of the closed neutral line around the parasitic polarity of the δ spot. Observations of the flare in 171, 195, and 1600 Å have been obtained by TRACE, with ~=40 s temporal and 0.5" spatial resolutions. They reveal that small-scale preflare loops above the sheared region expanded and disappeared for more than 1 hr before flare maximum. During the flare, bright loops anchored in bright ribbons form and grow. This occurs while large-scale dimmings, associated with large expanding loops, develop on both sides of the active region. This suggests that the flare was eruptive and was accompanied by a coronal mass ejection (CME). Magnetic field extrapolations reveal the presence of a null point in the corona, with its associated ``spine'' field line, and its ``fan'' surface surrounding the parasitic polarity. We show that while the whole event occurs, the intersections of the ``fan'' and the ``spine'' with the photosphere brighten and move continuously. The interpretation of the event shows that the magnetic evolution of the eruptive flare is strongly coupled with its surrounding complex topology. We discuss evidence supporting a ``magnetic breakout'' process for triggering this eruptive flare. We finally conclude that multipolar fields cannot be neglected in the study and modeling of the origin of CMEs in the corona. Title: Emergence of sheared magnetic flux tubes in an active region observed with the SVST and TRACE Authors: Deng, Y. Y.; Schmieder, B.; Engvold, O.; DeLuca, E.; Golub, L. Bibcode: 2000SoPh..195..347D Altcode: The active region NOAA AR 8331 was a target of an international ground-based observational campaign in the Canaries and coordinated with space instruments (TRACE and Yohkoh). We focus our study on observations obtained with the SVST at LaPalma, and with TRACE. On 10 September 1998, arch-filament systems were observed with high spatial and temporal resolution, from the lower to the upper atmosphere of the Sun, during five hours. Flux tubes emerged with increasing shear, which apparently led to energy release and heating in the overlying corona. A model for filament formation by the emergence of U-shaped loops from the subphotosphere, as proposed by Rust and Kumar (1994), is supported by the present observations. The coronal response to these events is visualized by rising, medium-scale loop brightenings. The low-lying X-ray loops show short-lived, bright knots which are thought to result from interaction between different loop systems. Title: A Brightening Coronal Loop Observed by TRACE. I. Morphology and Evolution Authors: Reale, F.; Peres, G.; Serio, S.; DeLuca, E. E.; Golub, L. Bibcode: 2000ApJ...535..412R Altcode: We analyze the transient brightening of a solar coronal loop observed, at high time cadence (30 s) and spatial resolution (0.5" pixel size), with the Transition Region and Coronal Explorer (TRACE) in the 171 Å band on 1998 June 26. The loop, located in AR 8253, is ~1010 cm long and inclined with respect to the vertical to the solar surface. Its geometry and shape do not change significantly during the brightening, which lasts for ~2 hr and is preceded by highly dynamic events in nearby and perhaps interacting loops. The loop footpoints brighten first; after ~10 minutes, moving brightness fronts rise initially from the northern footpoint, and after another ~7 minutes from the southern one, at an apparent speed ~100 km s-1, the whole loop becoming clearly visible afterward. During the rising phase the loop evolves coherently as a single magnetic tube. The brightness profile is asymmetric with respect to the loop apex at all times; the brightness contrast between the footpoints and the apex decreases with time from a ratio of ~10 to ~3. After the loop has become all visible, the several parallel filaments which form it follow an independent evolution. Assuming a plasma temperature of ~1 MK, we infer a plasma density of ~6×108 cm -3 and a pressure of ~0.2 dyn cm-2 close to the loop apex at the luminosity maximum. A companion paper is devoted to modeling the rising phase of this event. Title: A Brightening Coronal Loop Observed by TRACE. II. Loop Modeling and Constraints on Heating Authors: Reale, F.; Peres, G.; Serio, S.; Betta, R. M.; DeLuca, E. E.; Golub, L. Bibcode: 2000ApJ...535..423R Altcode: This is the second of two papers dedicated to the brightening of a coronal loop observed by the Transition Region and Coronal Explorer (TRACE) on 1998 June 26; it aims at hydrodynamic modeling of the brightening. Since the loop geometry is practically unchanged during the brightening, the evolution of the plasma confined in the loop is described with a one-dimensional hydrodynamic time-dependent numerical model, and from the results the emission along the loop in the TRACE 171 Å band is synthesized. The information from Paper I is used to derive the geometry and the initial configuration of the loop as well as for comparison with the results of the model. The modeling is focused to determine the amount, spatial distribution, and evolution of the heating deposited in the loop to make the modeled evolution close to that observed with TRACE. We find that, in order to match the observed evolution and distribution of the brightness along the loop, the heating has to be nonsymmetrical in the loop, in particular, deposited between the apex and one footpoint (3×109 cm from the southern footpoint). A reasonable match with observations is obtained by assuming that the heating is switched on abruptly and then kept constant for the whole rising phase. An even better match is obtained with the heating high and constant for 100 s and then decaying exponentially with an e-folding time of 300 s. We discuss the resulting physical scenario; a bright irregular structure close to the loop in the TRACE images may be a tracer of the heating release. Title: The X-ray telescope on Solar B. Authors: Deluca, E. E.; Golub, L.; Bookbinder, J.; Cheimets, P.; Shibasaki, K.; Sakao, T.; Kano, R. Bibcode: 2000BAAS...32..827D Altcode: No abstract at ADS Title: The X-Ray Telescope on Solar B Authors: DeLuca, E. E.; Golub, L.; Bookbinder, J.; Cheimets, P.; Shibasaki, K.; Sakao, T.; Kano, R. Bibcode: 2000SPD....31Q0293D Altcode: The X-ray observations from the Yohkoh SXT provided the greatest step forward in our understanding of the solar corona in nearly two decades. We believe that the scientific objectives of the Solar-B mission can best be achieved with an X-ray telescope (XRT) similar to the SXT, but with significant improvements in spatial resolution and in temperature response that take into account the knowledge gained from Yohkoh. We present the scientific justification for this view, discuss the instrumental requirements that flow from the scientific objectives, and describe the instrumentation to meet these requirements. XRT is a grazing-incidence (GI) modified Wolter I X-ray telescope, of 35cm inner diameter and 2.7m focal length. The 2048x2048 back-illuminated CCD has 13.5&mu pixels, corresponding to 1.0 arcsec and giving full Sun field of view. This will be the highest resolution GI X-ray telescope ever flown for Solar coronal studies, and it has been designed specifically to observe both the high and low temperature coronal plasma. A small optical telescope provide visibles light images for coalignment with the Solar-B optical and EUV instruments. The US XRT team is support by a NASA Contract from MSFC. Title: The Topology and Evolution of the Bastille Day Flare Observed by TRACE Authors: Aulanier, G.; Antiochos, S. K.; DeLuca, E. E.; McMullen, R. A.; Golub, L. Bibcode: 2000SPD....31.1402A Altcode: 2000BAAS...32..846A On July 14, 1998, a class M3 flare occurred at 12:55 UT in AR 8270 near disc center. Kitt Peak line-of-sight magnetograms show that the flare occurred in a δ -spot. Mees vector magnetograms show a strong shear localized near a portion of the closed neutral line around the parasitic polarity of the δ -spot. Observations of the flare in 171 Angstroms, 195 Angstroms and 1600 Angstroms have been obtained by TRACE, with ~= 40 s temporal and 0.5 arcsec spatial resolutions. They reveal that small-scale pre-flare loops above the sheared region expanded and disappeared for more than one hour before flare maximum. During the flare, bright loops anchored in bright ribbons form and grow. This occurs while large-scale dimmings, associated with large expanding loops, develop on both sides of the AR. This suggests that the flare was eruptive, and was accompanied by a coronal mass ejection (CME). Magnetic field extrapolations reveal the presence of a null point in the corona, with its associated ``spine'' field line, and its ``fan'' surface surrounding the parasitic polarity. We show that while the whole event occurs, the intersections of the ``fan'' and the ``spine'' with the photosphere brighten and move continuously. The interpretation of the event shows that the magnetic evolution of the eruptive flare is strongly coupled with its surrounding complex topology. We discuss evidence supporting a ``magnetic breakout'' process for triggering this eruptive flare. We finally conclude that multipolar fields cannot be neglected in the study and modeling of the origin of CMEs in the corona. This work is supported, at SAO by a NASA contract to Lockheed-Martin, and at NRL by NASA and ONR. Title: TRACE and Yohkoh Observations of High-Temperature Plasma in a Two-Ribbon Limb Flare Authors: Warren, H. P.; Bookbinder, J. A.; Forbes, T. G.; Golub, L.; Hudson, H. S.; Reeves, K.; Warshall, A. Bibcode: 1999ApJ...527L.121W Altcode: The ability of the Transition Region and Coronal Explorer (TRACE) to image solar plasma over a wide range of temperatures (Te~104-107 K) at high spatial resolution (0.5" pixels) makes it a unique instrument for observing solar flares. We present TRACE and Yohkoh observations of an M2.4 two-ribbon flare that began on 1999 July 25 at about 13:08 UT. We observe impulsive footpoint brightenings that are followed by the formation of high-temperature plasma (Te>~10 MK) in the corona. After an interval of about 1300 s, cooler loops (Te<2 MK) form below the hot plasma. Thus, the evolution of the event supports the qualitative aspects of the standard reconnection model of solar flares. The TRACE and Yohkoh data show that the bulk of the flare emission is at or below 10 MK. The TRACE data are also consistent with the Yohkoh observations of hotter plasma (Te~15-20 MK) existing at the top of the arcade. The cooling time inferred from these observations is consistent with a hybrid cooling time based on thermal conduction and radiative cooling. Title: Long-lived Coronal Loop Profiles from TRACE Authors: Lenz, Dawn D.; DeLuca, Edward E.; Golub, Leon; Rosner, Robert; Bookbinder, Jay A.; Litwin, Christof; Reale, Fabio; Peres, Giovanni Bibcode: 1999SoPh..190..131L Altcode: An initial study of long-lived loops observed with TRACE (Lenz et al., 1999) shows that they have no significant temperature stratification and that they are denser than the classic loop model predicts. Models that agree better with the observations include a loop consisting of a bundle of filaments at different temperatures and a loop with momentum input by MHD waves. Some implications for coronal heating models and mechanisms are discussed. Title: An Eruptive Flare Observed by TRACE as a Test for the Magnetic Authors: Aulaneir, G.; Deluca, E. E.; Golub, L.; Artzner, Guy; Sabine Coquillart; Hochedez, Jean-Francois; Delaboudinier, Jean-Pierre Bibcode: 1999ESASP.446..131A Altcode: 1999soho....8..131A No abstract at ADS Title: Solar-B X-ray Telescope (XRT) Concept Study Report Authors: Golub, Leon Bibcode: 1999STIN...9913119G Altcode: The X-ray observations from the Yohkoh SXT provided the greatest step forward in our understanding of the solar corona in nearly two decades. Expanding on the accomplishments of Yohkoh, we believe that the scientific objectives of the Solar-B mission are achieved with a significantly improved X-ray telescope (XRT) similar to the SXT. The Solar-B XRT will have twice the spatial resolution and a broader temperature response, while building on the knowledge gained from the successful Yohkoh mission. We present the scientific justification for this view, discuss the instrumental requirements that flow from the scientific objectives, and describe the instrumentation to meet these requirements. We then provide a detailed discussion of the design activities carried out during Phase A, noting the conclusions that were reached in terms of their implications for the detailed design activities which are now commencing. Details of the instrument that have changed as a result of the Phase A studied are specifically noted, and areas of concern going into Phase B are highlighted. XRT is a grazing-incidence (GI) modified Wolter I X-ray telescope, of 35cm inner diameter and 2.7m focal length. The 2048x2048 back-illuminated CCD (now an ISAS responsibility) has 13.5 micron pixels, corresponding to 1.0 arcsec and giving full Sun field of view. This will be the highest resolution GI X-ray telescope ever flown for Solar coronal studies, and it has been designed specifically to observe both the high and low temperature coronal plasma. A small optical telescope provides visible light images for co-alignment with the Solar-B optical and EUV instruments. The XRT science team is working in close cooperation with our Japanese colleagues in the design and construction of this instrument. All of the expertise and resources of the High Energy and Solar/Stellar Divisions of the Center for Astrophysics are being made available to this program, and our team will carry its full share of responsibility for mission operations, data reduction and education and public outreach. All aspects of the XRT design were reviewed during Phase A. The study focussed particularly on those aspects that have the greatest affect on instrument performance and extended lifetime, on the image quality error budget, and on the camera (mechanical and electrical) interface and the instrument mounting interfaces. The present instrument design differs in some details from that originally proposed. Selection of the XRT for Phase A study was contingent upon the removal of the camera and its associated electronics, and the acceptance of a stringent cost cap. The removal of the electronics left the XRT without control electronics for the instrument mechanisms. A mechanism controller was therefore added. The removal of the camera resulted in major complications to the integration and test plan. After many discussions, it was decided that the system would be less expensive, and the risk of unacceptable performance lower, if we include a focus mechanism. The remainder of the XRT design baseline matches the proposed configuration. Data requirements for the XRT are driven by the science plans, which are based on the physical processes in the solar outer atmosphere. Discussions to date of the XRT observing plan, both alone and in conjunction with the other Solar-B instruments, shows that the XRT needs 2 Gbits of on-board storage, at least one circulating buffer of 640 Mbits, and twelve 10- minute downlinks per day in order to carry out its required programs. Title: An Eruptive Flare Observed by TRACE as a Test for the Magnetic Authors: Aulaneir, G.; Deluca, E. E.; Golub, L.; McMullen, R. A.; Karpen, J. T.; Antiochos, S. K. Bibcode: 1999ESASP.446..135A Altcode: 1999soho....8..135A No abstract at ADS Title: Observed Magnetic Structure of X-Ray Bright Points from TRACE and MDI Authors: Brown, D. S.; Parnell, C.; Deluca, E.; McMullen, R.; Golub, L. Bibcode: 1999ASPC..184...81B Altcode: From 13th-17th June 1998, TRACE and MDI simultaneously observed the same quiet region of the Sun. From these observations the fascinating and complex structure of x-ray bright points, intense small scale brightenings that occur throughout the solar corona, can be seen in great detail. For the first time, it has been possible to study bright points for their entire lifetime with a cadence of 2 minutes and a temporal resolution of 0.5 arcsecs. One particular bright point which lasted two days exhibited dynamic structural behaviour which became increasingly complex and lead to its sudden eruptive demise. With the use of MDI magnetograms, it is possible to extrapolate the magnetic structure using an analytical constant α force-free approximation. This has been used to help us to explain the topology and behaviour of the bright point. By comparing two of TRACE's Fe lines (FeIX and FeXII) the spatial and temporal temperature and density structure of the bright point has been investigated. This analysis indicates that this bright point is made up of a complex system of dense loops. By understanding the magnetic, temperature and density structure of the bright point, it is hoped that the mechanism by which it is heated can be gained. Title: A new view of the solar outer atmosphere by the Transition Region and Coronal Explorer Authors: Schrijver, C. J.; Title, A. M.; Berger, T. E.; Fletcher, L.; Hurlburt, N. E.; Nightingale, R. W.; Shine, R. A.; Tarbell, T. D.; Wolfson, J.; Golub, L.; Bookbinder, J. A.; DeLuca, E. E.; McMullen, R. A.; Warren, H. P.; Kankelborg, C. C.; Handy, B. N.; De Pontieu, B. Bibcode: 1999SoPh..187..261S Altcode: The Transition Region and Coronal Explorer (TRACE) - described in the companion paper by Handy et al. (1999) - provides an unprecedented view of the solar outer atmosphere. In this overview, we discuss the initial impressions gained from, and interpretations of, the first million images taken with TRACE. We address, among other topics, the fine structure of the corona, the larger-scale thermal trends, the evolution of the corona over quiet and active regions, the high incidence of chromospheric material dynamically embedded in the coronal environment, the dynamics and structure of the conductively dominated transition region between chromosphere and corona, loop oscillations and flows, and sunspot coronal loops. With TRACE we observe a corona that is extremely dynamic and full of flows and wave phenomena, in which loops evolve rapidly in temperature, with associated changes in density. This dynamic nature points to a high degree of spatio-temporal variability even under conditions that traditionally have been referred to as quiescent. This variability requires that coronal heating can turn on and off on a time scale of minutes or less along field-line bundles with cross sections at or below the instrumental resolution of 700 km. Loops seen at 171 Å (∼1 MK) appear to meander through the coronal volume, but it is unclear whether this is caused by the evolution of the field or by the weaving of the heating through the coronal volume, shifting around for periods of up to a few tens of minutes and lighting up subsequent field lines. We discuss evidence that the heating occurs predominantly within the first 10 to 20 Mm from the loop footpoints. This causes the inner parts of active-region coronae to have a higher average temperature than the outer domains. Title: The transition region and coronal explorer Authors: Handy, B. N.; Acton, L. W.; Kankelborg, C. C.; Wolfson, C. J.; Akin, D. J.; Bruner, M. E.; Caravalho, R.; Catura, R. C.; Chevalier, R.; Duncan, D. W.; Edwards, C. G.; Feinstein, C. N.; Freeland, S. L.; Friedlaender, F. M.; Hoffmann, C. H.; Hurlburt, N. E.; Jurcevich, B. K.; Katz, N. L.; Kelly, G. A.; Lemen, J. R.; Levay, M.; Lindgren, R. W.; Mathur, D. P.; Meyer, S. B.; Morrison, S. J.; Morrison, M. D.; Nightingale, R. W.; Pope, T. P.; Rehse, R. A.; Schrijver, C. J.; Shine, R. A.; Shing, L.; Strong, K. T.; Tarbell, T. D.; Title, A. M.; Torgerson, D. D.; Golub, L.; Bookbinder, J. A.; Caldwell, D.; Cheimets, P. N.; Davis, W. N.; Deluca, E. E.; McMullen, R. A.; Warren, H. P.; Amato, D.; Fisher, R.; Maldonado, H.; Parkinson, C. Bibcode: 1999SoPh..187..229H Altcode: The Transition Region and Coronal Explorer (TRACE) satellite, launched 2 April 1998, is a NASA Small Explorer (SMEX) that images the solar photosphere, transition region and corona with unprecedented spatial resolution and temporal continuity. To provide continuous coverage of solar phenomena, TRACE is located in a sun-synchronous polar orbit. The ∼700 Mbytes of data which are collected daily are made available for unrestricted use within a few days of observation. The instrument features a 30-cm Cassegrain telescope with a field of view of 8.5×.5 arc min and a spatial resolution of 1 arc sec (0.5 arc sec pixels). TRACE contains multilayer optics and a lumogen-coated CCD detector to record three EUV wavelengths and several UV wavelengths. It observes plasmas at selected temperatures from 6000 K to 10 MK with a typical temporal resolution of less than 1 min. Title: Temperature and Emission-Measure Profiles along Long-lived Solar Coronal Loops Observed with the Transition Region and Coronal Explorer Authors: Lenz, Dawn D.; DeLuca, Edward E.; Golub, Leon; Rosner, Robert; Bookbinder, Jay A. Bibcode: 1999ApJ...517L.155L Altcode: 1999astro.ph..3491L We report an initial study of temperature and emission-measure distributions along four steady loops observed with the Transition Region and Coronal Explorer at the limb of the Sun. The temperature diagnostic is the filter ratio of the extreme-ultraviolet 171 and 195 Å passbands. The emission-measure diagnostic is the count rate in the 171 Å passband. We find essentially no temperature variation along the loops. We compare the observed loop structure with theoretical isothermal and nonisothermal static loop structure. Title: A new view of the solar corona from the transition region and coronal explorer (TRACE) Authors: Golub, L.; Bookbinder, J.; Deluca, E.; Karovska, M.; Warren, H.; Schrijver, C. J.; Shine, R.; Tarbell, T.; Title, A.; Wolfson, J.; Handy, B.; Kankelborg, C. Bibcode: 1999PhPl....6.2205G Altcode: The TRACE Observatory is the first solar-observing satellite in the National Aeronautics and Space Administration's (NASA) Small Explorer series. Launched April 2, 1998, it is providing views of the solar transition region and low corona with unprecedented spatial and temporal resolution. The corona is now seen to be highly filamented, and filled with flows and other dynamic processes. Structure is seen down to the resolution limit of the instrument, while variability and motions are observed at all spatial locations in the solar atmosphere, and on very short time scales. Flares and shock waves are observed, and the formation of long-lived coronal structures, with consequent implications for coronal heating models, has been seen. This overview describes the instrument and presents some preliminary results from the first six months of operation. Title: The Advanced Solar Coronal Explorer Mission (ASCE) Authors: Kohl, J.; Cranmer, S.; Gardner, L.; Golub, L.; Raymond, J.; Smith, P. L.; Strachan, L.; Howard, R.; Moses, D.; Socker, D.; Wang, D.; Fisher, R. R.; Davila, J.; St. Cyr, C.; Noci, G.; Tondello, G. Bibcode: 1999AAS...194.6506K Altcode: 1999BAAS...31Q.928K The Advanced Solar Coronal Explorer (ASCE) mission was selected for a Phase A Concept Study in the current round of proposed MIDEX missions. It addresses three fundamental problems: 1) What physical processes heat coronal holes and drive the fast solar wind? 2) What physical processes heat streamers and drive the slow solar wind? and 3) How are coronal mass ejections (CMEs) heated and accelerated, and what role to they play in the evolution of the solar magnetic field. ASCE has two instruments, the Spectroscopic and Polarimetric Coronagraph (SPC) and the Extreme Ultraviolet Imager (EUVI). A deployable boom supports a distant external occulter that allows large aperture optics for the SPC coronagraphic channels. SPC's EUV channels will provide spectroscopy of the extended solar corona with 30 - 200 times the sensitivity of UVCS/SOHO and the first He II 30.4 nm spectroscopy of the extended corona. SPC's Large Aperture Spectroscopic Coronagraph channel will provide two orders of magnitude improvement in stray light suppression for wide field visible spectroscopy and 2 arcsec resolution elements for imaging and polarimetry. EUVI provides full disk imaging with 0.9 arcsec resolution elements and extremely high cadence. ASCE is designed to determine the thermal, kinetic, and wave energy densities in coronal structures, determine the rates of transformation among these forms of energy, their flow in space, and their loss to radiation, and determine the composition and ionization state of the corona in static and transient conditions. Title: Future EUV/Soft X-ray Observations Authors: Golub, L. Bibcode: 1999AAS...194.6504G Altcode: 1999BAAS...31..927G The SEC Roadmap identifies Quests and Science Themes which form the organizational structure for the present and planned missions within the Office of Space Science at NASA. In order to carry out the scientific program defined by the Roadmap, a crucial component involves understanding of the causes of solar phenomena, such as the solar wind, the high-temperature corona, solar flares and coronal mass ejections. Furthering our understanding often involves direct observation of the million-degree coronal plasma, which is best seen at X-ray wavelengths. We will review the present status of such observations, and discuss what appear at this time to be the most promising directions for future observations. These include currently planned missions, such as HESSI, Solar-B and STEREO, as well as the exciting new possibilities opened up by recent advances in theory and in instrumental techniques. Title: The Solar Corona Authors: Golub, Leon; Pasachoff, Jay M.; Smartt, Raymond N. Bibcode: 1999AmJPh..67..263G Altcode: No abstract at ADS Title: Analysis and comparison of loop structures imaged with NIXT and Yohkoh/SXT Authors: Di Matteo, V.; Reale, F.; Peres, G.; Golub, L. Bibcode: 1999A&A...342..563D Altcode: We analyze and compare five coronal regions simultaneously observed by NIXT and Yohkoh/SXT on April 12, 1993. The compact loop structures (length ~ 10(9) cm) imaged in three regions with NIXT and with SXT have a good general morphological correspondence. A large scale (~ 1.7 x 10(10) cm) and an intermediate scale (~ 5 x 10(9) cm) structure observed in the NIXT image have no obvious counterpart in the SXT image. The pressure of the loop plasma detected by NIXT is derived from the brightness profile along the loops by applying a method based on loop models. The pressure of the loop plasma in the SXT band has also been derived from loop models on the basis of the temperature obtained from the standard Yohkoh data analysis. NIXT pressures are systematically lower than those found with SXT. By comparing the measured total loop luminosity to that expected on the basis of loop models, we constrain quantitatively the volume filling factor of the plasma emitting respectively in the NIXT and SXT bands. The filling factors obtained in the NIXT band for the compact and intermediate loops are very low (10(-3) - 10(-2) ), but they are of the order of unity for the large structure. The low filling factors suggest a strong loop filamentation. The filling factors for the compact structures are instead of the order of unity in the SXT band. We discuss our results and propose a scenario for their interpretation. Title: On the Ability of an Extreme-Ultraviolet Multilayer Normal-Incidence Telescope to Provide Temperature Information for Solar Plasmas Authors: Feldman, U.; Laming, J. M.; Doschek, G. A.; Warren, H. P.; Golub, L. Bibcode: 1999ApJ...511L..61F Altcode: In recent years, multilayer-coated optics have been used in solar-soft X-ray and extreme-ultraviolet telescopes to record high-resolution, full Sun images. The multilayer coatings reflect efficiently over rather narrow wavelength bands that are selected to contain spectral emission lines considered to have plasma diagnostic importance for determining approximate electron temperatures. The purpose of this Letter is to discuss the effect of continuum emission on the response of multilayer passbands and the effect of this response on temperature determinations in the 4×106-2×107 K range. Significant effects are largely confined to continuum emission from flare plasma. The flare free-free continuum in the EUV range is nearly temperature and wavelength insensitive and dominates the emission in passbands that are centered on quiet- to active-Sun coronal lines emitted by ions such as Fe IX-Fe XV. Title: Observations of High-Temperature Flare Plasma with Transition Region and Coronal Explorer (TRACE) Authors: Reeves, K. K.; Golub, L.; Warren, H. P. Bibcode: 1999agu..meet..234R Altcode: The so-called standard model of solar flares makes specific predictions concerning the amount, location, and timing of both hot (Te>10 MK) and cool (Te<2 MK) plasma in solar flares. The ability of the Transition Region and Coronal Explorer (TRACE) to image solar plasma over a wide range of temperatures (Te~104-107 K) at high spatial resolution (0.5″ pixels) make it a unique instrument for observing solar flares and testing the model predictions. We present TRACE and Yohkoh observations of an M2.4 two-ribbon flare that began on 1999 July 25 at about 13:08 UT. These observations are in qualitative agreement with the essential elements of the reconnection model. We observe impulsive footpoint brightenings that are quickly followed by the formation of high-temperature plasma in the corona. After an interval of about 1300 s cooler loops form below the hot plasma. The cooling time inferred from the observations suggests large densities (ne~1011 cm-3) for the high temperature plasma so that radiative losses dominate the cooling process. The TRACE data are consistent with the Yohkoh observations of a ``hot'' (Te~15-20 MK) plasma existing at the top of the arcade. Title: The TRACE Mission: Initial Scientific Results Authors: Title, A. M.; Tarbell, T. D.; Wolfson, J.; Schrijver, K.; Fisher, R. R.; Gang, Th.; Golub, L.; McMullen, R. A.; Kankelborg, C.; TRACE Collaboration Bibcode: 1998AAS...19310008T Altcode: 1998BAAS...30R1398T TRACE (Transition Region and Coronal Explorer) is a Small Explorer Mission (SMEX) devoted to studying the evolution and propagation of fine-scale magnetic fields and plasma structures throughout the solar atmosphere. The instrument consists of a telescope with a 30 cm primary mirror, normal incidence coatings for three EUV bands (171, 195 and 284 Angstroms), and interference filters for UV bands (1216 to 1700 Angstroms) as well as white light (allowing the selection of temperature ranges from ~ 6 000 to ~ 2 500 000 degrees K). The 1024 x 1024 CCD camera has a field of view of 8.5 arcmin with a spatial resolution of 1 arcsec and exposure times of 0.002 to 260 sec with a cadence as short as two seconds. The spacecraft was launched on April 1, 1998, and first light for the telescope occurred on April 20. Observations have been collected nearly 24 hours per day since then, with no significant problems in any segment of the spacecraft, instrument, or mission operations. TRACE transmits about 3--4 GB of data per week which gets automatically reformatted and becomes available for the scientific community within approx. 24 hours. It is accessible without restrictions (only guidelines) together with other informations (technical details, educational material, movies, images,...) at: http://vestige.lmsal.com/TRACE. The images reveal activity in the solar atmosphere in stunning detail and include the first detailed observations of a magnetic energy release. This magnetic reconnection was observed on May 8, 1998, in a region of the solar atmosphere where two sets of perpendicular magnetic loops expanded into each other (see NASA Press Release 98-92). The TRACE mission has been developed and operated by NASA's Goddard Space Flight Center, Lockheed Martin Solar & Astrophysics Laboratory, Smithsonian Astrophysical Observatory, and Montana State University. Title: Book Review: The solar corona / Cambridge U Press, 1997 Authors: Golub, L.; Pasachoff, J. M. Bibcode: 1998SoPh..183..227G Altcode: No abstract at ADS Title: HIREX: results of the mission concept study Authors: Bookbinder, Jay A.; Cheimets, Peter; Davis, William R.; Caldwell, David; Golub, Leon; Deluca, Edward Bibcode: 1998SPIE.3442...22B Altcode: HIREX is a suite of three complementary solar-pointed instruments that is being proposed to NASA under the NASA MIDEX announcement of opportunity. The main instrument is a 0.6m clear aperture, 240m effective focal length normal incidence XUV telescope operated at 171 angstrom, with a spatial resolution of 0.01 inch. This main telescope is complemented by two other instruments: 1) a 0.3 m context telescope that images in a wavelength range that covers the UV and XUV spectral regime, based on the TRACE design. This context telescope places the high magnification, limited field of view images created by the high resolution telescope in both spatial and temperature context. 2) A spectrometer covering the spectral range from 170-220 angstrom, based on the SERTS design. Title: A New View of the Solar Corona from TRACE. Authors: Golub, Leon Bibcode: 1998APS..DPPH4I204G Altcode: The TRACE Observatory is a small solar satellite in NASA's Small Explorer series. Launched April 2, 1998, it is providing views of the solar transition region and low corona with unprecedented spatial and temporal resolution. The corona is now seen to be highly filamented, and filled with flows and with dynamic processes. Structure is seen down to the resolution limit of the instruments, while variability and motions are observed at all spatial locations in the solar atmosphere, and on very short timescales. Falres and shock waves are observed, and the formation of long-lived coronal structures, with consequent implications for coronal heating models, has been seen. In this overview, we will describe the satellite and show some preliminary results from the first six months of operation. Title: Super-X: a soft x-ray telescope for Solar-B Authors: Acton, Loren W.; Bookbinder, Jay A.; Bruner, Marilyn E.; Golub, Leon; Lemen, James R. Bibcode: 1998SPIE.3442..140A Altcode: This paper describes the conceptual design of a soft x-ray telescope, super-x, which we will propose for the Japan/US/UK Solar-B mission. Super-X will break new ground in both angular resolution and solar coronal temperature discrimination. The telescope design is based upon the successful transition region and coronal explorer instrument. It features four XUV spectral channels spanning the 0.3 to 20 MK temperature range with an angular resolution of approximately 0.27 seconds of arc. We will describe considerations affecting spectral line selection and some details of the characteristics of the instrument. Title: Novel mirror mount design: TRACE primary mirror Authors: Cheimets, Peter; Bookbinder, Jay A.; Davis, William R.; Golub, Leon Bibcode: 1998SPIE.3445...28C Altcode: Orbiting x-ray and XUV observatories are pushing the achievable image resolution and with it, the requirements on mounted mirror performance. The transitional region and coronal explorer (TRACE) observatory uses a center mounted primary mirror that must maintain its orientation in roll as well as pitch and way. A conformable bedding was used to support the mirror against the expected launch loads in a re-assembled mount, without inducing unacceptable mirror distortion. The novel mirror mount design is discussed, and its resulting performance described. This paper outlines the TRACE primary mirror assembly design. The evolution of the design from the Space Weather and Terrestrial Hazards assembly to the TRACE baseline design is presented. Title: Large-area thin aluminum filter design, handling, and testing Authors: Cheimets, Peter; Bookbinder, Jay A.; Deluca, Edward; Caldwell, David; Davis, William R.; Golub, Leon Bibcode: 1998SPIE.3445...96C Altcode: The process of observing the Sun in the x-ray and extreme UV (XUV), as we are now doing with the TRACE telescope, requires blocking the tremendous amount of visible and RI light that dominates the flux from the sun. If it is not blocked, the energy will swamp the desired spectrum and cause thermal problems inside the telescope. The most effective approach removing the energy is by filtering the incoming light. One of the best materials for eliminating the undesirable wavelengths is aluminum, which is semi- transparent to x-ray and XUV, but blocks most light with wavelength redward of 850 angstrom. Unfortunately the aluminum must be extremely must be extremely thin, < 1600 angstrom thick, to provide the necessary XUV transparency. To overcome the structural problem of supporting large areas of extremely thin aluminum, the aluminum film is bonded on a nickel mesh. Title: Structure and Dynamics of Coronal Plasma Authors: Golub, Leon Bibcode: 1998STIN...9917617G Altcode: Brief summaries of the four published papers produced within the present performance period of NASA Grant NAGW-4081 are presented. The full text of the papers are appended to the report. The first paper titled "Coronal Structures Observed in X-rays and H-alpa Structures" was published in the Kofu Symposium proceedings. The study analyzes cool and hot behavior of two x-ray events, a small flare and a surge. It was found that a large H-alpha surge appears in x-rays as a very weak event, while a weak H-alpha feature corresponds to the brightest x-ray emission on the disk at the time of the observation. Calculations of the heating necessary to produce these signatures, and implications for the driving and heating mechanisms of flares vs. surges are presented. The second paper "Differential Magnetic Field Shear in an Active Region" has been published in The Astrophysical Journal. The study compared the three dimensional extrapolation of magnetic fields with the observed coronal structure in an active region. Based on the fit between observed coronal structure throughout the volume of the region and the calculated magnetic field configurations, the authors propose a differential magnetic field shear model for this active region. The decreasing field shear in the outer portions of the AR may indicate a continual relaxation of the magnetic field with time, corresponding to a net transport of helicity outward. The third paper "Difficulties in Observing Coronal Structure" has been published in the journal Solar Physics. This paper discusses the evidence that the temperature and density structure of the corona are far more complicated than had previously been thought. The discussion is based on five studies carried out by the group on coronal plasma properties, showing that any one x-ray instrument does see all of the plasma present in the corona, that hot and cool material may appear to be co-spatial at a given location in the corona, and that simple magnetic field extrapolations provide only a poor fit to the observed structure. The fourth paper "Analysis and Comparison of Loop Structures Imaged with NIXT and Yohkoh/SXT" has been published in Astronomy and Astrophysics. This paper analyzes and compares a variety of coronal loops, deriving loop pressure and emission measure from loop models. They are able to determine the volume filling factor in the corona, which is found to be in the range 0.001 to 0.01 for compact loops, and of order 1 for large structures. The small values suggest highly filamented structures, especially at lower temperatures. Title: First Results from the TRACE Mission Authors: Title, A.; Tarbell, T.; Schrijver, C.; Wolfson, J.; Shine, R.; Hurlburt, N.; Golub, L.; Deluca, E.; Bookbinder, J.; Handy, B.; Acton, L.; Harrison, R.; Delaboudinere, J. -P. Bibcode: 1998AAS...192.1507T Altcode: 1998BAAS...30..841T The TRACE spacecraft was launched on 1 April and all systems are functioning as designed. The initial outgassing period will conclude on 20 April and the science program will then begin. TRACE is a UV-EUV imager with one arc second spatial resolution and is capable of taking images with a cadence as high as two seconds. We will present images and image sequences. We hope to present initial comparisons of magnetic evolution and transition region and coronal brightenings. Title: Dynamic Responses to Magnetic Reconnection in Solar Arcades Authors: Karpen, Judith T.; Antiochos, Spiro K.; Richard DeVore, C.; Golub, Leon Bibcode: 1998ApJ...495..491K Altcode: We present a numerical simulation of the interaction between two line dipoles through magnetic reconnection in the lower solar atmosphere, a process believed to be the origin of many manifestations of solar activity. This work differs from previous studies in that the field is sheared asymmetrically and that the dipoles have markedly unequal field strengths. This calculation already yielded one key discovery, denoted reconnection driven current filamentation, as described in a previous Astrophysical Journal letter. In this paper we focus on the chromospheric and coronal dynamics resulting from the shear-driven reconnection of unequal dipoles, discuss the important implications for chromospheric eruptions, compare our calculation with high-resolution Normal Incidence X-Ray Telescope observations of a surge, and contrast our results with the predictions of ``fast reconnection'' models. Title: The Global Coronal Structure Investigation Authors: Golub, Leon Bibcode: 1998sao..reptS....G Altcode: During the past year we have completed the changeover from the NIXT program to the new TXI sounding rocket program. The NIXT effort, aimed at evaluating the viability of the remaining portions of the NIXT hardware and design, has been finished and the portions of the NIXT which are viable and flightworthy, such as filters, mirror mounting hardware, electronics and telemetry interface systems, are now part of the new rocket payload. The backup NIXT multilayer-coated x-ray telescope and its mounting hardware have been completely fabricated and are being stored for possible future use in the TXI rocket. The H-alpha camera design is being utilized in the TXI program for real-time pointing verification and control via telemetry. A new H-alpha camera has been built, with a high-resolution RS170 CCD camera output. Two papers, summarizing scientific results from the NIXT rocket program, have been written and published this year: 1. "The Solar X-ray Corona," by L. Golub, Astrophysics and Space Science, 237, 33 (1996). 2. "Difficulties in Observing Coronal Structure," Keynote Paper, Proceedings STEPWG1 Workshop on Measurements and Analyses of the Solar 3D Magnetic Field, Solar Physics, 174, 99 (1997). Title: A Multiwavelength Study of Coronal Structure: A Simultaneous Observation from NIXT and YOHKOH Authors: Golub, Leon Bibcode: 1998sao..reptR....G Altcode: Solar soft X-ray images taken simultaneously by the Yohkoh and the Normal Incidence X-ray Telescope (NIXT) reveal significantly different coronal structures. Coronal loops are more clearly seen in the Yohkoh images, and the isolated island-like structures seen in the NIXT image have been found to correspond to the footpoints of the Yohkoh loops. The difference is due to the difference in the temperature response of the telescopes: NIXT is sensitive to temperatures ranging from 0.9 to 3 MK, while Yohkoh is more sensitive to temperatures above 2.5 MK. The morphological differences reflect the multi-temperature (1-5 MK) nature of the solar coronal plasmas. Title: The HIREX Mission Authors: Golub, L. Bibcode: 1998ESASP.417..157G Altcode: 1998cesh.conf..157G No abstract at ADS Title: The Solar Corona Authors: Golub, Leon; Pasachoff, Jay M. Bibcode: 1997soco.book.....G Altcode: Observations from the ground and space have advanced our knowledge of the solar corona dramatically over the past three decades. This timely volume presents a lucid and synthesized review of the latest observations of the solar corona and discusses how these observations have advanced and shaped our understanding of coronal physics. In the process, the authors introduce a wide variety of exciting physics, including dynamo theory and radiative transfer. They also demonstrate how the transient effects of the solar cycle effect "space weather." This book provides a much-needed introduction to coronal physics for advanced students and researchers. Title: Difficulties in Observing Coronal Structure Authors: Golub, L. Bibcode: 1997SoPh..174...99G Altcode: There has developed in recent years a substantial body of evidence to indicate that the temperature and density structure of the corona are far more complicated than had previously been thought. We review some of the evidence and discuss some specific examples: observations of a limb flare, showing that the cool Hα material is cospatial with the hot X-ray emitting material; simultaneous NIXT and Yohkoh SXT observations of an active region, showing that loops seen in one instrument are not seen in the other, and that the effect works in both directions; comparisons of extrapolated magnetic field measurements to the observed coronal structure, indicating that neither potential nor constant-α force-free fits are adequate. We conclude with a description of two new instruments, the TRACE and the TXI, which will help to resolve some of these difficulties. 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: Detecting Siphon Flows in Coronal Loops Authors: McMullen, Rebecca A.; Deluca, Edward E.; Golub, Leon Bibcode: 1997SPD....28.0148M Altcode: 1997BAAS...29..888M While siphon flows are thought to be common in coronal loops, detection in coronal emission has remained elusive. The Tuneable X-Ray Imager (TXI) sounding rocket will produce images of the corona in 4 Angstroms \ passbands around prominent emission lines between 170-200 Angstroms. This new instrument can also produce velocity maps from difference images taken on either side of an emission line. We present a study of the response of the TXI to siphon flows in coronal loop models. The models show that loops with flows are significantly fainter than the equivalent static loops. In addition, contamination from nearby lines tends to mask the Doppler shift, even with an instrument of excellent imaging capacity. We will outline more detailed analysis methods that may reveal the siphon flows more clearly. Title: Difficulties in Observing Coronal Structure Authors: Golub, Leon Bibcode: 1997nixt.reptR....G Altcode: There has developed in recent years a substantial body of evidence to indicate that the temperature and density structure of the corona are far more complicated than had previously been thought. We review some of the evidence and discuss some specific examples: observations of a limb flare, showing that the cool H alphas material is cospatial with the hot x-ray emitting material; simultaneous NIXT and Yohkoh SXT observations of an active region, showing that loops seen in one instrument are not seen in the other and that the effect works in both directions; comparisons of extrapolated magnetic field measurements to the observed coronal structure, indicating that neither potential nor constant-alpha force-free fits are adequate. We conclude with a description of two new instruments, the TRACE and the TXI, which will help to resolve some of these difficulties. Title: Study of a Solar X-Ray Telescope Authors: Golub, Leon Bibcode: 1997sao..rept.....G Altcode: The highly structured nature of the outer solar atmosphere seems to be intimately linked to the presence, at the solar surface, of magnetic fields that have been generated inside the Sun and have emerged to the surface. The corona is brightest (and also hottest) at just those locations where the magnetic field has emerged from inside the Sun. Dynamo theory predicts that strong magnetic fields will be generated deep in the solar interior and that bundles or 'ropes' of magnetic flux will float to the surface. When this happens, a magnetically bipolar region will become visible, extending above the surface in a three-dimensional structure. The field lines penetrate through the surface, showing two magnetic poles, and also exhibit a three-dimensional structure above the surface. The structure created by the field emergence is rooted in the (relatively) cool photosphere and extends through the chromosphere and transition region to the corona. Thus, the magnetic field creates a region, called an active region, which contains portions at temperatures from less than 104 K to greater than 106 K, and is therefore visible at wavelengths from the infrared through x-rays. The locations where the magnetic field leaves and reenters the visible surface are called the 'footpoints' of the coronal structures associated with the magnetic field. The magnetic fields themselves are not directly visible. However, the hot coronal plasma is, for the most part, constrained to follow the direction of the magnetic field lines in the atmosphere. Now, 100 years after the discovery of x-rays by Wilhelm Roentgen in 1896, we can routinely make observations of the solar corona from outside the Earth's atmosphere in this region of the electromagnetic spectrum. As shown by comparing x-ray images with magnetograms, the bright corona over these bipolar magnetic regions consists of closed structures that seem to follow the orientation of the magnetic field. Although we can see down to the photosphere at x-ray wavelengths when observing the disk of the Sun, this part of the solar atmosphere emits so little that far from the peak of its Planck curve it appears dark in x-ray images. This impression of hot plasma following the magnetic field direction is further strengthened by quantitative studies that calculate coronal magnetic field strength and direction based on photospheric measurements and compare them with the observed brightness and location of the x-ray emitting structures. Such comparisons make it clear that, for the most part, the hot plasma conforms to the geometry of the magnetic field and that the coronal brightness is strongly linked to the strength of the magnetic fields which have erupted to the solar surface from the interior. It is also the case that the larger-scale, fainter corona, as well as coronal holes, are strongly influenced by the large-scale solar magnetic field. We may get a small hint of the reason that the coronal plasma outlines the direction of B by examining the thermal conductivity of a hot plasma in the presence of a magnetic field. This quantity has enormously different values in the directions parallel and perpendicular to the field for a coronal temperature of 106 K, a particle density of 109/cu cm and a magnetic field strength of 100 G, the conductivity along the field is approximately 13 orders of magnitude greater than that perpendicular to the field. It is therefore not surprising that a parcel of plasma which is locally heated would conduct that heat preferentially in the direction of the field. We also note that the thermal conductivity parallel to the magnetic field increases with temperature T, while the perpendicular conductivity decreases. To the extent that the loop aspect ratio, i.e., the ratio of loop length to loop width, is determined by the thermal conductivity, we would expect that higher temperature loops are longer and thinner than cooler ones. However, if the loop width becomes smaller than the spatial resolution of the observing instrument, this effect will not be directly observable. For organizational purposes, we provide a listing of some scientific objectives for a Solar-B x-ray telescope, arranged in terms of identifiable features in the corona. Title: The TRACE Mission Authors: Wolfson, J.; Bruner, M.; Jurcevich, B.; Lemen, J.; Schrijver, K.; Shine, R.; Strong, K.; Tarbell, T.; Title, A.; Golub, L.; Bookbinder, J.; Deluca, E.; Acton, L.; Handy, B.; Kankelborg, C.; Fisher, R. Bibcode: 1997SPD....28.0143W Altcode: 1997BAAS...29..887W The TRACE (Transition Region and Coronal Explorer) mission will explore the connections between fine-scale magnetic fields and plasma structures in the coronal, transition zone and temperature minimum regions of the sun. TRACE will collect images of solar plasmas at temperatures from 10(4) to 10(7) K, with one arc second spatial resolution and excellent temporal resolution and continuity. With a scheduled launch date of 15 December 1997, the mission will emphasize collaborative observations with SoHO, enabling simultaneous observations of high-resolution images, spectra, and magnetograms. The 30 cm aperture TRACE telescope uses four normal-incidence coatings for the EUV and UV on quadrants of the primary and secondary mirrors. Interference filters further isolate 5 different UV bands. The images are co-aligned and internally stabilized against spacecraft jitter. A 1024 x 1024 lumigen-coated CCD detector collects images over an 8.5 x 8.5 arc minute field-of-view. LMATC, SAO, and GSFC built the TRACE instrument, which was integrated with the GSFC-produced SMEX spacecraft on 28 February (just over two years from the start of its development). It will be put into a Sun-synchronous orbit and operated in coordination with the SoHO Experiment Operations Facility at GSFC. We are committed to maintaining a publicly accessible data base for TRACE data. Browsing and data set requesting capabilities will be provided at Web site www.space.lockheed.com/TRACE/TRACElinks.html. This site already contains a large volume of information on the mission including preliminary scientific observing programs and directions as to how to participate in the mission now and in the future. This project is supported by NASA contract NAS5-38099. Title: Structure and Dynamics of Coronal Plasmas Authors: Golub, Leon Bibcode: 1997stcp.conf.....G Altcode: During the past year this grant has funded research in the interaction between magnetic fields and the hot plasma in the solar outer atmosphere. The following is a brief summary of the published papers, abstracts and talks which have been supported. The paper 'Coronal Structures Observed in X-rays and H-alpha Structures' was published in the Kofu Symposium proceedings. The study analyzes cool and hot behavior of two x-ray events, a small flare and a surge. We find that a large H-alpha surge appears in x-rays as a very weak event, while a weak H-alpha feature corresponds to the brightest x-ray emission on the disk at the time of the observation. Calculations of the heating necessary to produce these signatures, and implications for the driving and heating mechanisms of flares vs. surges are presented. A copy of the paper is appended to this report. The paper 'Differential Magnetic Field Shear in an Active Region' has been published in The Astrophysical Journal. We have compared the 3D extrapolation of magnetic fields with the observed coronal structure in an active region. Based on the fit between observed coronal structure throughout the volume of the region and the calculated magnetic field configurations, we propose a differential magnetic field shear model for this active region. The decreasing field shear in the outer portions of the AR may indicate a continual relaxation of the magnetic field with time, corresponding to a net transport of helicity outward. The paper 'Difficulties in Observing Coronal Structure' has been accepted for publication in the journal Solar Physics. In this paper we discuss the evidence that the temperature and density structure of the corona are far more complicated than had previously been thought. The discussion is based on five studies carried out by our group on coronal plasma properties, showing that any one x-ray instrument does see all of the plasma present in the corona, that hot and cool material may appear to be co-spatial at a given location in the corona, and that simple magnetic field extrapolations provide only a poor fit to the observed structure. A copy of the paper is appended to this report. 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: Differential Magnetic Field Shear in an Active Region Authors: Schmieder, B.; Demoulin, P.; Aulanier, G.; Golub, L. Bibcode: 1996ApJ...467..881S Altcode: The three-dimensional extrapolation of magnetic field lines from a magneto gram obtained at Kitt Peak allows us to understand the global structure of the NOAA active region 6718, as observed in X-rays with the Normal Incidence X-ray Telescope (NIXT) and in Hα with the Multichannel Subtractive Double Pass spectrograph (MSDP) in Meudon on 1991 July 11. This active region was in a quiet stage. Bright X-ray loops connect plages having field strengths of ∼300 G, while Hα fibriles connect penumbrae having strong spot fields to the surrounding network. Small, intense X-ray features in the moat region around a large spot, which could be called X-ray-bright points, are due mainly to the emergence of magnetic flux and merging of these fields with surrounding ones. A set of large-scale, sheared X-ray loops is observed in the central part of the active region. Based on the fit between the observed coronal structure and the field configurations (and assuming a linear force-free field), we propose a differential magnetic field shear model for this active region. The decreasing shear in outer portions of the active region may indicate a continual relaxation of the magnetic field to a lower energy state in the progressively older portions of the AR. Title: Structure and dynamics of coronal plasmas Authors: Golub, Leon Bibcode: 1996sao..reptQ....G Altcode: Progress for the period July 1995 - June 1996 included work on the differential magnetic field shear in an active region; observations and modeling of the solar chromosphere seen in soft X-ray absorption by NIXT; and modeling magnetic flux emergence. These were the subjects of three papers. The plans for the current year include projects on a converging flux model for point-like brightenings around sunspots, and difficulties in observing coronal structure. Title: TRACE: the Transition Region and Coronal Explorer Authors: Schrijver, C.; Title, A.; Acton, L.; Bruner, M.; Fischer, R.; Golub, L.; Harrison, R.; Lemen, J.; Rosner, R.; Scharmer, G.; Scherrer, P.; Strong, K.; Tarbell, T.; Wolfson, J. Bibcode: 1996AAS...188.6704S Altcode: 1996BAAS...28..934S The TRACE mission is designed to obtain images of the solar transition region and corona of unprecedented quality. With these images we will be able to explore quantitatively the connections between the photospheric magnetic field and the associated hot and tenuous structures in the outer atmosphere. The TRACE telescope has an aperture of 30 cm, and will observe an 8.5 x 8.5 arcminute field of view with a resolution of one arcsecond. Finely tuned coatings on four quadrants on the primary and secondary normal--incidence mirrors will allow observations in narrow EUV and UV spectral bands. The passbands are set to Fe IX, XII, and XV lines in the EUV band, while filters allow observations in C IV, Ly alpha , and the UV continuum using the UV mirror quadrant. The data thus cover temperatures from 10(4) K up to 10(7) K. The Sun--synchronous orbit allows long intervals of uninterrupted viewing. Observations at different wavelengths can be made in rapid succession with an alignment of 0.1 arcsec. Coordinated observing with TRACE, SoHO and YOHKOH will give us the first opportunity to observe all temperature regimes in the solar atmosphere, including magnetograms, simultaneously from space. TRACE is currently scheduled to be launched in October 1997. More information can be found on the web at ``http://pore1.space.lockheed.com/TRACE/welcome.html''. Title: The Solar X-Ray Corona Authors: Golub, L. Bibcode: 1996Ap&SS.237...33G Altcode: The solar corona, and the coronae of solar-type stars, consist of a low-density magnetized plasma at temperatures exceeding 106 K. The primary coronal emission is therefore in the UV and soft x-ray range. The observed close connection between solar magnetic fields and the physical parameters of the corona implies a fundamental role for the magnetic field in coronal structuring and dynamics. Variability of the corona occurs on all temporal and spatial scales—at one extreme, as the result of plasma instabilities, and at the other extreme driven by the global magnetic flux emergence patterns of the solar cycle. Title: White-Light Reflecting Corona graph for the SWATH Mission Authors: Smartt, Raymond N.; Dunn, Richard B.; Carmichael, Roger B.; Gregory, B. Scott; Plum, Douglas W.; Neidig, Donald F.; Golub, Leon; Bookbinder, Jay A.; Koutchmy, George U.; Nystrom, Serge L.; Zimmermann, Jean-Paul Bibcode: 1996ASPC...95..531S Altcode: 1996sdit.conf..531S No abstract at ADS Title: Observations of a Quiescent Prominence Straddling the Solar Limb during the Total Eclipse of 11 July 1991 Authors: Gaizauskas, V.; Deluca, E.; Golub, L.; Jones, H. P.; November, L. Bibcode: 1996mpsa.conf..491G Altcode: 1996IAUCo.153..491G No abstract at ADS Title: Comparison of High Resolution Optical and Soft X-ray Images of Solar Corona Authors: Takeda, A.; Kurokawa, H.; Kitai, R.; Ishiura, K.; Golub, L. Bibcode: 1996mpsa.conf..483T Altcode: 1996IAUCo.153..483T No abstract at ADS Title: The TRACE Mission Authors: Title, A.; Bruner, M.; Jurcevich, B.; Lemen, J.; Strong, K.; Tarbell, T.; Wolfson, J.; Golub, L.; Fisher, R. Bibcode: 1995AAS...18710107T Altcode: 1995BAAS...27.1427T We have seen significant progress in the flight preparation of the TRACE (Transition Region and Coronal Explorer) instrument during the last few months. TRACE, approved for 1997 launch, will collect images of solar plasmas at temperatures from 10(4) to 10(7) K, with one arc second spatial resolution and excellent temporal resolution and continuity. TRACE will explore the connections between fine-scale magnetic fields and plasma structures in the coronal, transition zone and temperature minimum regions of the sun. The 1997 launch opportunity allows for collaborative observations from Earth orbit with the SoHO instruments stationed at L1. Simultaneous observations including high-resolution images, spectra, and magnetograms are possible. The 30 cm aperture TRACE telescope uses four normal-incidence coatings for the EUV and UV on quadrants of the primary and secondary mirrors. Interference filters further isolate 5 different UV bands. The images are coaligned and internally stabilized against spacecraft jitter. A 1024 x 1024 CCD detector collects images over an 8.5 x 8.5 arc minute field-of-view. TRACE is launched on a GSFC SMEX spacecraft into a Sun-synchronous orbit. It will operate in coordination with the SoHO Experiment Operations Facility at GSFC. We are committed to maintaining an publicly accessible data base for TRACE data. Browsing and data set requesting capabilities will be included at our World Wide Web site (see http://www.space.lockheed.com/TRACE/welcome.html). Title: Observations and Interpretation of Soft X-Ray Limb Absorption Seen by the Normal Incidence X-Ray Telescope Authors: Daw, A.; Deluca, E. E.; Golub, L. Bibcode: 1995ApJ...453..929D Altcode: The Normal Incidence X-Ray Telescope (NIXT) obtained a unique set of high-resolution full-disk solar images which were exposed simultaneously by X-rays in a passband at 63.5 Å and by visible light. The perfect alignment of a photospheric visible-light image with a coronal X-ray image enables us to present observations of X-ray intensity as a function of an accurately determined height above the visible limb. The height at which the observed X-ray intensity peaks varies from 4000 km in active regions to 9000 km in quiet regions of the Sun. The interpretation of the observations stems from the previously established fact that, for the coronal loops, emission in the NIXT bandpass peaks sharply just above the footpoints. Because there is not a sharp peak in the observed X-ray intensity as a function of off-limb height, we conclude that the loop footpoints, when viewed at the limb, are obscured by absorption in chromospheric material along the line of sight. We calculate the X-ray intensity as a function of height predicted by a number of different idealizations of the solar atmosphere, and we compare these calculations with the observed X-ray intensity as a function of height. The calculations use existing coronal and chromospheric models. In order for the calculations to reproduce the observed off-limb X-ray intensities, we are forced to assume an atmosphere in which the footpoints of coronal loops are interspersed along the line of sight with cooler chromospheric material extending to heights well above the loop footpoints. We argue that the absorption coefficient for NIXT X-rays by chromospheric material is roughly proportional to the neutral hydrogen density, and we estimate an average neutral hydrogen density and scale height implied by the data. Title: Structure and dynamics of coronal plasmas Authors: Golub, Leon Bibcode: 1995sao..reptQ....G Altcode: The Normal Incidence X-ray Telescope (NIXT) obtained a unique set of high resolution full disk solar images which were exposed simultaneously by X-rays in a passband at 63.5 A and by visible light. The perfect alignment of a photospheric visible light image with a coronal X-ray image enables us to present observations of X-ray intensity vs an accurately determined height above the visible limb. The height at which the observed X-ray intensity peak varies from 4000 km in active regions to 9000 km in quiet regions of the sun. The interpretation of the observations stems from the previously established fact that, for the coronal loops, emission in the NIXT bandpass peaks sharply just above the footpoints. Because there is not a sharp peak in the observed X-ray intensity vs off limb height, we conclude that the loop footpoints, when viewed at the limb, are obscured by absorption in chromospheric material along the line of sight. We calculate the X-ray intensity vs height predicted by a number of different idealizations of the solar atmosphere, and we compare these calculations with the observed X-ray intensity vs height. The calculations use existing coronal and chromospheric models. In order for the calculations to reproduce the observed off limb X-ray intensities, we are forced to assume an atmosphere in which the footpoints of coronal loops are interspersed along the line of sight with cooler chromospheric material extending to heights well above the loop footpoints. We argue that the absorption coefficient for NIXT X-rays by chromospheric material is roughly proportional to the neutral hydrogen density, and we estimate an average neutral hydrogen density and scale height implied by the data. Title: The Transition Region and Coronal Explorer (trace) Authors: Title, A.; Bruner, M.; Jurcevich, B.; Lemen, J.; Strong, K.; Tarbell, T.; Wolfson, J.; Golub, L.; Bookbinder, J.; Fisher, R. Bibcode: 1995ESASP.376b.505T Altcode: 1995help.confP.505T; 1995soho....2..505T No abstract at ADS Title: Normal incidence optics for solar coronal imaging Authors: Spiller, Eberhard; Wilczynski, Janusz S.; Golub, Leon; Nystrom, George U.; Gullikson, Eric M.; Tarrio, Charles Bibcode: 1995SPIE.2515..136S Altcode: We have produced two new normal incidence soft x-ray telescope mirrors coated for lambda equals 63.5 angstrom wavelength: the first with a focal length f equals 1.5 m and a diameter of 25 cm for the Space Weather and Terrestrial Hazards (SWATH) satellite and the second (f equals 2 m, diameter 27.5 cm) for launch by sounding rocket (NIXT). We describe figuring and polishing of the mirror surfaces and deposition and testing of the multilayer coatings. Optimization of the mirror fabrication included grazing incidence x-ray reflectivity for quality control during polishing. In addition, the substrate and each metal layer of the Co-C multilayer coating were polished by an ion beam with in-situ roughness estimation. We explored the possibilities and limitations of telescopes for shorter wavelengths by coating several small mirrors covering the lambda equals 45 to 60 angstrom region at normal incidence and report on their performance. Title: Temperature Structure of the Solar Corona: Comparison of the NIXT and YOHKOH X-Ray Images Authors: Yoshida, Tsuyoshi; Tsuneta, Saku; Golub, Leon; Strong, Keith; Ogawara, Yoshiaki Bibcode: 1995PASJ...47L..15Y Altcode: Solar soft X-ray images taken simultaneously by the Yohkoh and the Normal Incidence X-ray Telescope (NIXT) reveal significantly different coronal structures. Coronal loops are more clearly seen in the Yohkoh images, and the isolated island-like structures seen in the NIXT image have been found to correspond to the footpoints of the Yohkoh loops. The difference is due to the difference in the temperature response of the telescopes: NIXT is sensitive to temperatures ranging from 0.9 to 3 MK, while Yohkoh is more sensitive to temperatures above 2.5 MK. The morphological differences reflect the multi-temperature (1--5 MK) nature of the solar coronal plasmas. Title: NIXT X-ray Bright Point Survey: Building a Better Bright Point Authors: Wills, M. J.; Hartl, M. D.; Deluca, E. E.; Golub, L. Bibcode: 1995SPD....26..707W Altcode: 1995BAAS...27..966W No abstract at ADS Title: Recovering the fine structures in solar images Authors: Karovska, M.; Habbal, S. R.; Golub, L.; DeLuca, E.; Hudson, H. Bibcode: 1994ESASP.373..183K Altcode: 1994soho....3..183K No abstract at ADS Title: Bright Rims Adjacent to a Quiescent Hα Filament Authors: Gaizauskas, V.; de Luca, E.; Golub, L.; Jones, H. P. Bibcode: 1994AAS...18512304G Altcode: 1994BAAS...26.1522G Recent models of filament-formation invoke reconnection between small-scale magnetic elements adjacent to the polarity inversion line separating large areas of unipolar magnetic fields. In an attempt to confirm this process, we examine joint observations of a quiescent filament straddling the SW limb of the Sun during the total solar eclipse of 1991 July 11. We test a hypothesis that a signature of the reconnection process might be carried by the prominent bright rims beside or enclosed between curved feet, or 'barbs', which connect the body of the Hα filament to structures near the base of the atmosphere. We spatially register digitized Hα (ORSO) images of the filament with coronal (NIXT) images and with photospheric magnetograms (NSO/KP) to a precision of +/- 2". Our findings relate to five rims, elongated bright patches in Hα with a maximum length of 20". We find a better spatial association of the rims with bipolar magnetic elements (4/5) than with small patches of weakly enhanced soft X-rays (2/4). We point out that projection effects at these extreme limb positions could alter these associations. We conclude from these limited 'snapshot' observations that we are not yet able to decide whether or not bright rims on quiescent prominences are locations of magnetic reconnection on a small scale. Because reconnection is highly dynamic, compelling evidence for or against this process will have to await prolonged observations at multiple wavelengths in X-rays of a single filament at high spatial and temporal resolution, such as those envisaged for the Transition Region and Coronal Explorer (TRACE). Title: Simultaneous High Resolution Coronal and Photospheric Observations From NIXT and BBSO Authors: Winebarger, A.; Deluca, E. E.; Golub, L. Bibcode: 1994AAS...185.8605W Altcode: 1994BAAS...26.1464W High resolution coronal images from the 11 September 1989 flight of the NIXT (Normal Incidence X-ray Telescope) and a series of simultaneous high resolution Big Bear Magnetograms are discussed as part of an on going investigation of X-ray bright points. The NIXT and BBSO images are aligned and the evolution of the magnetic fields associated with coronal features were monitored over the experimental time frame. An analysis of the relationship between the X-ray bright points and the time resolved BBSO magnetograms is presented. Bright points are associated with both converging and diverging magnetic bi-poles. Title: The Roots of Coronal Structure in the Sun's Surface Authors: Golub, Leon; Zirin, Harold; Wang, Haimin Bibcode: 1994SoPh..153..179G Altcode: We have compared the structures seen on X-ray images obtained by a flight of the NIXT sounding rocket payload on July 11, 1991 with near-simultaneous photospheric and chromospheric structures and magnetic fields observed at Big Bear. The X-ray images reflect emission of both MgX and FeXVI, formed at 1 × 106 K and 3 × 106 K, respectively. The brightest Hα sources correspond to a dying sub-flare and other active region components, all of which reveal coronal enhancements situated spatially well above the Hα emission. The largest set of X-ray arches connected plages of opposite polarity in a large bipolar active region. The arches appear to lie in a small range of angle in the meridian plane connecting their footpoints. Sunspots are dark on the surface and in the corona. For the first time we see an emerging flux region in X-rays and find the emission extends twice as high as the Hα arches. Many features which we believe to correspond to `X-ray bright points' (XBPs) were observed. Whether by resolution or spectral band, the number detected greatly exceeds that from previous work. All of the brighter XBPs correspond to bipolar Hα features, while unipolar Hα bright points are the base of more diffuse comet-like coronal arches, generally vertical. These diverge from individual features by less than 30°, and give a good measure of what the `canopies' must do. The Hα data shows that all the Hα features were present the entire day, so they are not clearly disappearing or reappearing. We find a new class of XBPs which we call `satellite points', elements of opposite polarity linked to nearby umbrae by invisible field lines. The satellite points change rapidly in X-ray brightness during the flight. An M1.9 flare occurred four hours after the flight; examination of the pre-flare structures reveals nothing unusual. Title: Coronal Structures Observed in X-rays (NIXT) and H_alpha Surges Authors: Schmieder, B.; Mouradian, Z.; Golub, L.; Antiochos, S. Bibcode: 1994kofu.symp..317S Altcode: Ground-based coordinated observations with the Multichannel subtractive double pass spectrograph (MSDP) and the heliograph in Meudon allowed us to portray the chromospheric intensity and velocity fields below coronal structures observed with the Normal Incidence X-ray Telescope (NIXT). On July 11, 1991 (eclipse day) we have identified in AR 6713 (N38 W 42) the X-ray signatures of the network, subflares, filaments and surges. The largest H_alpha surge has only weak emission in X-ray, while a weak H_alpha feature corresponds to a very bright x-ray subflare. We calculate the emission measures of these events and give some constraints on the triggering mechanisms of surges. Title: The Three-Dimensional Structures of X-Ray Bright Points Authors: Parnell, C. E.; Priest, E. R.; Golub, L. Bibcode: 1994SoPh..151...57P Altcode: Recently, the Converging Flux Model has been proposed for X-ray bright points and cancelling magnetic features. The aim of this peice of work is to try and model theoretically specific X-ray bright points in the framework of the Converging Flux Model. The observational data used includes a magnetogram showing the normal component of the magnetic field at the photosphere and a high-resolution soft X-ray image from NIXT showing the brightenings in the lower solar corona. By approximating the flux concentrations in the magnetograms with poles of the appropriate sign and sense, the overlying three-dimensional potential field structure is calculated. Deduction of plausible motions of the flux sources are made which produce brightenings of the observed shape due to reconnection between neighbouring flux regions. Also the three-dimensional separarix and separator structure and the way the magnetic field lines reconnect in three dimensions is deduced. Title: Comparison between Cool and Hot Plasma Behaviors of Surges Authors: Schmieder, B.; Golub, L.; Antiochos, S. K. Bibcode: 1994ApJ...425..326S Altcode: Ground-based coordinated observations with the Multichannel Subtractive Double Pass spectrograph (MSDP) allowed us to obtain chromospheric intensity and velocity field maps below coronal structures during the launch of the NIXT payload on 1991 July 11 (eclipse day). A large H-alpha ejection in AR 6713 (N38 W40) was detected during the NIXT flight. However, only a low level of X-ray emission was associated with this event. In contrast, bright X-ray emission associated with a subflare was observed in a nearby active region, but with only a weak associated ejection in H-alpha. A discussion of both of these events gives strong constraints on the triggering mechanisms of surges. Title: Loop Models of Low Coronal Structures Observed by the Normal Incidence X-Ray Telescope (NIXT) Authors: Peres, G.; Reale, F.; Golub, L. Bibcode: 1994ApJ...422..412P Altcode: The X-ray pictures obtained with the Normal Incidence X-Ray Telescope (NIXT), apart from the ubiquitous coronal loops well known from previous X-ray observations, show a new and peculiar morphology: in many active regions there are wide and apparently low-lying areas of intense emission which resemble H alpha plages. By means of hydrostatic models of coronal arches, we analyze the distribution of temperature, density, emission measure, and plasma emissivity in the spectral band to which NIXT is sensitive, and we show that the above morphology can be explained by the characteristics of high pressure loops having a thin region of high surface brightness at the base. We therefore propose that this finding might help to identify high-pressure X-ray emitting coronal regions in NIXT images, and it is in principle applicable to any imaging instrument which has high sensitivity to 104 - 106 K plasma within a narrow coronal-temperature passband. As a more general result of this study, we propose that the comparison of NIXT observations with models of stationary loops might provide a new diagnostic: the determination of the loop plasma pressure from measurements of brightness distribution along the loop. Title: Results from the recent flights of the IBM/SAO x-ray telescopes Authors: Spiller, Eberhard; Barbee, Troy W.; Golub, Leon; Kalata, Kenneth; Nystrom, George U.; Viola, A. Bibcode: 1994SPIE.2011..391S Altcode: The instruments on board our Normal Incidence X-ray Telescopes payload and the results obtained during the most recent flights will be described. The payload was launched three times during the 1991 - 1993 period, the last time on April 12, 1993. It contained a main telescope with an 11 inch diameter multilayer coated mirror for (lambda) equals 63.5 angstroms and photographic film as detector. Smaller telescopes for either (lambda) equals 304 angstroms or (lambda) equals 193 angstroms used electronic detection and direct transmission of analog or digital data to the ground station. The flight on the day of the solar eclipse in July 1991 gave us an opportunity to perform a soft-ray knife edge test with the limb of the moon. From the experiment we derive upper limits for the figure errors of the telescope mirror, and we conclude that large mirrors with diffraction limited resolution better than 0.01 arcsec can now be fabricated. Title: The NIXT and SWATH Experiments Authors: Golub, Leon Bibcode: 1994ASPC...68..329G Altcode: 1994sare.conf..329G No abstract at ADS Title: Investigation relative to the Roentgen Satellite (ROSAT) Authors: Elvis, Martin S.; Primini, Francis A.; Fabbiano, Guiseppina; Harris, Daniel E.; Jones-Forman, Christine; Trinchieri, Ginevra; Golub, Leon; Bookbinder, Jay; Seward, Frederick D.; Zombeck, Martin V. Bibcode: 1994sao..rept.....E Altcode: Reports include: High Resolution Observations of the Central Region of M31; The X-ray Emission of Low-X-ray-Luminosity Early-Type Galaxies: Gas Versus Compact Sources; Interaction Between Cluster Gas and Radio Features of Cygnus A; Hot Gas and Dark Halos in Early-Type Galaxies; A Gravitational Lens in X-rays - 0957+461; How Massive are Early-Type Galaxies?; Three Crab-Like SNR in the Large Magellanic Cloud; and Soft X-ray Emission from Boundary Layers in Cataclysmic Variables. Papers submitted to the Astrophysical Journal are attached. Title: Pressure diagnostics of coronal loops observed by NIXT Authors: Peres, G.; Reale, F.; Golub, L. Bibcode: 1994LNP...432..179P Altcode: 1994LNPM...11..179P The Normal Incidence X-ray Telescope (NIXT sounding rocket payload — a set of multilayer telescopes of novel design — provides images of the corona at sub-arcsec angular resolution in narrow X-ray spectral bands centered at the wavelengths of particular coronal emission lines. The NIXT 63.5 angstrom coronal images show the well-known and ubiquitous coronal loops but also, mostly in active regions, shallow and bright areas of intense emission not resembling loops. We have explained such areas within the traditional physics of coronal loop models as intense emission in the NIXT band coming from a narrow region at the base of high pressure loops; the particular nature of the NIXT temperature sensitivity, with its bimodal temperature response, is the key to detecting such a feature. We discuss the implications of this finding and, in particular, we show the possibility of new diagnostics of plasma pressure independent of the traditional one based on the determination of emission measure. In addition, we show that there is very little dependence of the spatial distribution of the X-ray emissivity in the NIXT passband on the details of the spatial distribution of the heating function. Title: Coronal Structures Observed in X-Rays (NIXT) and Hα Surges Authors: Schmieder, B.; Mouradian, Z.; Golub, L.; Antiochos, S. Bibcode: 1994emsp.conf..159S Altcode: No abstract at ADS Title: The SWATH Satellite Program Authors: Bookbinder, J.; Golub, L.; Deluca, E.; Smartt, R. Bibcode: 1993AAS...183.0810B Altcode: 1993BAAS...25R1302B No abstract at ADS Title: The Coronal Structure above Sunspots and Pores Authors: Harmon, R.; Rosner, R.; Zirin, H.; Spiller, E.; Golub, L. Bibcode: 1993ApJ...417L..83H Altcode: No abstract at ADS Title: The Magnetic Field in the Corona above Sunspots at the Eclipse of 1991 July 11 Authors: Gary, D. E.; Leblanc, Y.; Dulk, G. A.; Golub, L. Bibcode: 1993ApJ...412..421G Altcode: A partial solar eclipse and an X-ray image are used to study the magnetic field as a function of height in the corona above an active region during the solar eclipse of July 11, 1991. The dominant features of AR 6718 are two leading spots of positive polarity followed by two spots of negative polarity about 3 arcmin to the east. Bright radio emission coincides with the positions of the sunspots, attributable to a gyroresonance radiation from ambient electrons above the spots. A simplified model of the source as a function of frequency based on the interferometer fringe amplitudes is used to obtain brightness temperature spectra for the emission associated with the sunspots. It is deduced that the magnetic field strength at the base of the corona above the leading spots was 1200 G, and about 1100 G above the following spots. The soft X-ray brightness above the sunspots was very low, about 30 times lower than that of the adjacent plage-associated emission. Title: Heating the Sun's million degree corona. Authors: Golub, L. Bibcode: 1993Ast....21....4G Altcode: For decades astronomers have struggled to explain why the Sun's corona is so much hotter than its surface. Now X-ray observations reveal new clues about what heats the corona. Title: Normal Incidence X-Ray Telescope Power Spectra of X-Ray Emission from Solar Active Regions. I. Observations Authors: Gomez, Daniel O.; Martens, Petrus C. H.; Golub, Leon Bibcode: 1993ApJ...405..767G Altcode: Fourier analysis is applied to very high resolution image of coronal active regions obtained by the Normal Incidence X-Ray Telescope is used to find a broad isotropic power-law spectrum of the spatial distribution of soft X-ray intensities. Magnetic structures of all sizes are present down to the resolution limit of the instrument. Power spectra for the X-ray intensities of a sample of topologically different active regions are found which fall off with increasing wavenumber as 1/k-cubed. A model is presented that relates the basic features of coronal magnetic fluctuations to the subphotospheric hydrodynamic turbulence that generates them. The model is used to find a theoretical power spectrum for the X-ray intensity which falls off with increasing wavenumber as 1/k-cubed. The implications of a turbulent regime in active regions are discussed. Title: Normal Incidence X-Ray Telescope Power Spectra of X-Ray Emission from Solar Active Regions. II. Theory Authors: Gomez, Daniel O.; Martens, Petrus C. H.; Golub, Leon Bibcode: 1993ApJ...405..773G Altcode: In a previous paper, we used the very high resolution images of coronal active regions obtained by the Normal Incidence X-Ray Telescope to study the size distribution of X-ray-emitting structures. A Fourier analysis of these images showed a broad-band, isotropic, power-law spectrum for the spatial distribution of soft X-ray intensities. The presence of a broad-band spectrum indicates that magnetic structures of all sizes are 3" present, at least down to the resolution limit of the instrument, which is about ¾".

In the present paper, we present a model that relates the basic features of coronal magnetic fluctuations to the subphotospheric hydrodynamic turbulence that generates them. The main result of this paper is that from this model we obtain a theoretical power spectrum for the X-ray intensity, which falls off with increasing wavenumber as k-3, fitting remarkably well the observed spectra that we obtained from a sample of topologically different active regions.

We speculate that the nonlinear interactions of these externally driven fluctuations will contribute to establish a magnetohydrodynamic turbulent regime in the corona. We suggest that the bulk of the energy delivered to the corona from footpoint motions directly cascades down to very microscopic length scales, where it efficiently dissipates and heats the plasma. However, since the wavenumber range associated with the cascade and dissipation regions are still beyond present-day spatial resolution limits, the presence of a turbulent regime cannot be observationally confirmed. Title: NIXT High Resolution Observations Authors: Golub, L. Bibcode: 1993ASSL..183...71G Altcode: 1993pssc.symp...71G No abstract at ADS Title: X-Ray Observations of Sunspot Penumbral Structure Authors: Sams, B. J., III; Golub, L.; Weiss, N. O. Bibcode: 1992ApJ...399..313S Altcode: High-resolution coronal observations with the Normal Incidence X-ray Telescope (NIXT) reveal previously unobserved structure in the magnetic fields above a sunspot. The X-ray images are precisely aligned with a continuum photospheric image taken at the same time. The X-ray brightness traces magnetic field lines and shows: (1) that none of the bright loops originate in the spot umbra and (2) that some field lines emerging from the inner penumbra connect to regions far away from the spot. Such large-scale structures must remain distinct from the shallowly inclined fields in the outer penumbra. In particular, they cannot be involved in any interchange between the bright and dark filaments. This imposes constraints on models of penumbral convection. Title: Underneath coronal loops: MSDP observations coordinated with SERTS 4 and NIXT flights. Authors: Schmieder, B.; Mein, N.; Golub, L.; Davila, J. M.; Thomas, R.; Brosius, J. Bibcode: 1992ESASP.348..257S Altcode: 1992cscl.work..257S Ground-based coordinated observations with the multichannel subtractive double pass spectrograph (MSDP) allowed to portray the chromospheric intensity and velocity fields below coronal structures during recent launchs of sounding rockets. During SERTS 4 observations (May 7, 1991), two different active regions presenting flare and filament have been coaligned with UV structures. In July 11, 1991 (eclipse day) large Hα ejection material in AR 6713 was detected during the NIXT flight. Preliminary results are displayed. Title: Imaging performance of multilayer x-ray mirrors Authors: Spiller, Eberhard; Wilczynski, Janusz; Stearns, Daniel; Golub, Leon; Nystrom, George Bibcode: 1992ApPhL..61.1481S Altcode: We analyze soft X-ray images of the solar corona, obtained on the day of the solar eclipse in July 1991, and find that the deviations of our telescope mirror from the perfect surface are less than 1 A for spatial periods between 1 micron and 1 mm. Our thin film deposition technique allows us to reduce errors over larger periods to the 1 A level. Thus, we are able to produce larger (diameter over 20 cm) X-ray mirrors with diffraction limited resolution below 0.01 arcsec. Title: Coronal Loops: Current-based Heating Processes Authors: Beaufume, P.; Coppi, B.; Golub, L. Bibcode: 1992ApJ...393..396B Altcode: Based on new observations, a theoretical model of magnetic-field related heating processes in the solar corona is given. In this model, field-aligned currents are induced along coronal loops in thin current sheaths. Excitation of instabilities involving magnetic reconnection converts the energy associated with the current-related magnetic field directly into particle energy, where the heating process proceeds via short bursts corresponding to an intermittent disruption of the current sheath configuration. Because of the relatively low transverse thermal conduction, only a small fraction of the loop volume is heated to a much higher temperature than the average value. This is consistent with experimental observations of low filling factors of hot plasmas in coronal loops. Thus the model involves a repeated sequence of dynamic events taking into account the observed loop topology, the differential emission measure distribution in the 10 exp 6 - 10 exp 7 K range, the energy balance requirements in the loop, and the probable duty cycles involved in the heating processes. Title: How Coronal Loops Brighten: Observational Results from the Normal Incidence X-Ray Telescope Sounding Rocket Experiment Authors: Golub, L.; Harmon, R.; Rashid, R.; Spiller, E. Bibcode: 1992AAS...180.4008G Altcode: 1992BAAS...24..793G No abstract at ADS Title: Obtaining high resolution XUV coronal images. Authors: Golub, L.; Spiller, E. Bibcode: 1992ESASP.344..221G Altcode: 1992spai.rept..221G Photos obtained during three flights of our 11-inch diameter normal incident soft X-ray telescope are analyzed and the data are compared to the results expected from tests of the mirror surfaces. Multilayer coated X-ray telescopes have the potential for 0.01 arcsec resolution and the authors are optimistic that such high quality mirrors can be built. Some of the factors which enter into the performance actually achieved in practice are: quality of the mirror substrate, quality of the multilayer coating and number of photons collected. The authors' measurements of multilayer mirrors show that the actual performance achieved in the solar x-ray images demonstrates a reduction in the scattering compared to that calculated from the topography of the top surface of the multilayer. Title: Structure of the Solar X-ray Corona (Invited Review) Authors: Golub, L. Bibcode: 1992ASPC...26..193G Altcode: 1992csss....7..193G No abstract at ADS Title: The X-ray ultraviolet imager for the orbiting solar laboratory Authors: Antonucci, Ester; Malvezzi, Marco; Ciminiera, Luigi; Angrilli, Francesco; Bruner, Marilyn E.; Perona, Giovanni; Adele Dodero, Maria; Evans, Brian L.; Golub, Leon; Landini, Massimo; Noci, Giancarlo; McWhirter, Peter; Fossi, Brunella Monsignori; Poletto, Giannina; Neidig, Donald F.; Schmidt, Wolfgang K. H.; Thomas, Roger J.; Tondello, Giuseppe Bibcode: 1992AIPC..267..126A Altcode: 1992ecsa.work..126A A normal incidence multimirror telescope, the X-ray Ultraviolet Imager, for high resolution imaging of the solar atmosphere in the soft X-ray/XUV region, is being developed as part of the scientific payload of the NASA Orbiting Solar Laboratory. The X-ray Ultraviolet Imager is formed by two units: a high resolution telescope (0.25 arcsec pixel size and 8×8 arcmin2 field of view) and a wide field one (2.3 arcsec pixel size and 5×5 solar radii2 field of view). The two systems complement each other and allow a full coverage of solar features from the small scale (200 km on the sun) to the global phenomena. Each system consists of 8 channels with multilayer mirrors, imaging at different wavelengths. In each channel the mirror coating is optimized to select a narrow spectroscopic window corresponding to an intense line in the region 40-400 A˚. In order to provide imaging and temperature diagnostics from the chromosphere to the upper corona, 8 wavelengths are chosen to cover the broad temperature range from 105 to 107 K. Four images, two high resolution and two full disk ones, are simultaneously obtained by the X-ray Ultraviolet Imager, at a cadence which in flares can be of 0.4-1 s. Title: Hydrostatic models of X-ray coronal loops observed by NIXT Authors: Peres, G.; Reale, F.; Golub, Leon Bibcode: 1992AIPC..267..136P Altcode: 1992ecsa.work..136P Observations made with the Normal Incidence X-ray Telescope (NIXT) have shown that some X-ray emitting structures observed with NIXT resemble very closely the corresponding Hα plages. We have used hydrostatic models of coronal loops to explain such observations as strong emission from the lower section of high-presssure coronal arches. Title: Normal incidence soft x-ray lambda=63.5 A telescope of 1991 Authors: Spiller, Eberhard; Wilczynski, Janusz S.; Golub, Leon; Nystrom, George U. Bibcode: 1992SPIE.1546..168S Altcode: 1992SPIE.2011..168S Modifications to our multilayer coated normal incidence telescope for (lambda) equals 63.5 angstrom since its last flight in 1989 are described. The purpose of the changes was to increase the photon flux of the detector by increasing the mirror reflectivity, area, and uniformity and by the use of light blocking filters with higher x-ray transmission. First results from the 1991 launch of the telescope are described. Title: High resolution observations of the solar corona Authors: Gomez, D.; Golub, L. Bibcode: 1992HiA.....9..659G Altcode: No abstract at ADS Title: High resolution observations of the solar corona Authors: Gomez, D.; Golub, L. Bibcode: 1992MmSAI..63..591G Altcode: The Normal Incidence X-ray Telescope has recently obtained sub-arcsecond images of the solar corona in a series of successful rocket flights. Coronal loops are found to present a highly fibrilated internal structure, down to the spatial resolution of the instrument. The footpoints of coronal loops lie in areas of enhanced chromospheric emission, like network, plage or sunspot penumbrae. No hot loops have been found terminating in sunspot umbrae. Several flare events have also been detected during these flights, all of them showing a highly tangled topological structure at small scales. A Fourier analysis performed on a number of coronal active region images yields a broadband power spectrum for the spatial distribution of soft X-ray intensity, which can be interpreted by the presence of a turbulent regime inside coronal loops. Title: Flares Observed by the Normal Incidence X-Ray Telescope on 1989 September 11 Authors: Herant, M.; Pardo, F.; Spiller, E.; Golub, L. Bibcode: 1991ApJ...376..797H Altcode: Two solar flare events have been observed in soft X-rays during a sounding-rocket flight of the Normal-Incidence X-ray Telescope payload on September 11, 1989. The flare in X-rays involves a single bright loop crossing the neutral line, and having its footpoints at the southern ends of the ribbons; this loop accounts for more than 66 percent of the emission. Within the remainder of each of the flare ribbons, a complex coronal structure is also observed to be interacting with the main flare loop. A second event, in an active region at the limb, has a strong correlation with H-alpha images obtained at the same time. This indicates the coexistence, and indeed the close proximity, of coronal and chromospheric temperature material. Interpretations of this phenomenon are discussed. Title: Normal-incidence soft X-ray telescopes. Authors: Spiller, Eberhard; McCorkle, R. A.; Wilczynski, J. S.; Golub, Leon; Nystrom, G.; Takacs, P. Z.; Welch, C. Bibcode: 1991OptEn..30.1109S Altcode: Photos obtained during 5 min of observation time from the flight of a 25 cm-diam normal-incidence soft X-ray (λ = 63.5Å) telescope are analyzed and the data are compared to the results expected from tests of the mirror surfaces. These tests cover a range of spatial periods from 25 cm to 1Å. The photos demonstrate a resolution close to the photon shot noise limit and a reduction in the scattering of the multilayer mirror compared to a single surface for scattering angles above 1', corresponding to surface irregularities with spatial periods below 10 μm. The results are used to predict the possible performance of future telescopes. The authors conclude that sounding rocket observations might be able to reach a resolution around 0.1″ Title: A Dynamical Model for Heating of Coronal Loops Authors: Beaufumê, P.; Coppi, B.; Golub, L. Bibcode: 1991BAAS...23.1059B Altcode: No abstract at ADS Title: Imaging performance and tests of soft x-ray telescopes Authors: Spiller, Eberhard; McCorkle, R.; Wilczynski, Janusz S.; Golub, Leon; Nystrom, George U.; Takacs, Peter Z.; Welch, Charles W. Bibcode: 1991SPIE.1343..134S Altcode: No abstract at ADS Title: Spectra of MHD Turbulence in Coronal Active Regions (With 3 Figures) Authors: Gomez, D.; Martens, P.; Herant, M.; Pardo, F.; Golub, L. Bibcode: 1991mcch.conf..124G Altcode: No abstract at ADS Title: X-ray Observations of Global Solar Activity Authors: Golub, L. Bibcode: 1991LNP...387..271G Altcode: 1991fpsa.conf..271G High resolution observations of the Solar corona, mainly from the Skylab missions in 1973-74, have shown that the x-ray corona is variable on all observable temporal and spatial scales. Variability which has been observed ranges from x-ray bright point flares, with sizes of a few arcseconds and rise times of tens of seconds, to large scale structure evolution on time scales of months to years and size scales of a Solar radius. In this paper we present a sampling of the data, up to and including the most recent high resolution results from the NIXT rocket, in order to discuss the important new contributions which will be made by the Solar-A instruments. Title: Very High Resolution Solar X-ray Imaging (With 6 Figures) Authors: Golub, L. Bibcode: 1991mcch.conf..115G Altcode: No abstract at ADS Title: SXT Observations of MHD Turbulance in Active Regions Authors: Martens, P. C. H.; Gómez, D. O.; Slater, G.; Golub, L. Bibcode: 1991LNP...387..291M Altcode: 1991fpsa.conf..291M The recent discovery from NIXT images that the Fourier transform of the X-ray intensity in active regions is a power-law, is consistent with 2D MHD turbulence theory. We briefly discuss this theory and its application to the heating of the solar corona. Then we demonstrate that SXT will be capable of observing similar spectra, even in compressed data-transfer mode between flare observations. Finally we discuss observing plans for verification of the hypothesis of coronal heating through turbulent MHD cascades. Title: Long- and short-timescale variability of magnetic activity on the BY Dra star BD + 26°730 Authors: Saar, S. H.; Golub, L.; Bopp, B.; Herbst, W.; Huovelin, J. Bibcode: 1990ESASP.310..431S Altcode: 1990eaia.conf..431S No abstract at ADS Title: Filters for soft X-ray solar telescopes. Authors: Spiller, Eberhard; Grebe, Kurt; Golub, Leon Bibcode: 1990OptEn..29..625S Altcode: Soft X-ray telescopes require filters that block visible and infrared light and have good soft X-ray transmission. The optical properties of possible materials are discussed, and the fabrication and testing methods for the filters used in a 10-inch normal incidence telescope for λ = 63 Å are described. The best performances in the λ= 44 - 114 Å wavelength range are obtained with foils of carbon and rhodium. Title: Filters for soft x-ray solar telescopes Authors: Golub, Leon Bibcode: 1990OptEn..29..625G Altcode: No abstract at ADS Title: The XUV imager for the OSL. Authors: Landini, M.; Noci, G.; Antonucci, E.; Bruner, M. E.; Evans, B. L.; Golub, L.; Malvezzi, M.; McWhirter, R. W.; Monsignori Fossi, B. C.; Poletto, G.; Neidig, D.; Perona, G.; Thomas, R.; Tondello, G. Bibcode: 1990BAAS...22.1148L Altcode: No abstract at ADS Title: Sub-arcsecond observations of the solar X-ray corona Authors: Golub, L.; Herant, M.; Kalata, K.; Lovas, I.; Nystrom, G.; Pardo, F.; Spiller, E.; Wilczynski, J. Bibcode: 1990Natur.344..842G Altcode: SOFT X-ray observations are recognized as the best way to study the solar corona, as they are largely free of contaminating emission from other temperature regimes. They provide the only available method for seeing the corona on the disk, thereby avoiding the line-of-sight integration effects which are troublesome in limb observations. Here we present results from a high-resolution multilayer-coated X-ray imaging telescope, part of the Normal Incidence X-ray Telescope sounding rocket payload. From a flight at 16:35 UT on 11 September 1989 we obtained 40 images of the solar X-ray corona, with spatial resolution up to 0.75 arcsec. Images of the peak of a two-ribbon flare showed detailed structure within each ribbon, as well as the expected bright arches of emission connecting the ribbons. Active regions showed structure at a scale of 0.75 arcsec that was not visible in our 2-arcsec images taken during the same flight. The number of X-ray bright points1 is small, consistent with predictions based on the previous solar cycle2. The topology of the magnetic structure is complex and highly tangled, implying that the magnetic complexity of the photosphere is paralleled in the corona. Title: Observational Evidence for Heating through MHD Turbulence in Coronal Active Regions Authors: Gomez, D.; Martens, P. C. H.; Herant, M.; Golub, L. Bibcode: 1990BAAS...22Q.796G Altcode: No abstract at ADS Title: NIXT Observations of the June 23 1988 Flare and their Theoretical Interpretation Authors: Martens, P. C. H.; Golub, L.; Herant, M. Bibcode: 1990ppsa.conf..153M Altcode: No abstract at ADS Title: Sub-Arcsecond Observations of the Solar X-ray Corona Authors: Golub, L.; Spiller, E. Bibcode: 1989BAAS...21Q1150G Altcode: No abstract at ADS Title: Comments on the Observability of Coronal Variations Authors: Golub, L.; Hartquist, T. W.; Quillen, A. C. Bibcode: 1989SoPh..122..245G Altcode: We discuss the observable variability of spectral lines in the soft X-ray and XUV region. Rapid variability of coronal emission, both in flaring and non-flaring structures has been reported and is particularly prominent when high spatial resolution is available. Examination of the ionization and recombination time-scales for the formation and removal of ions with prominent solar emission lines shows that, even though ionization equilibrium generally prevails, the observable variability time-scales are often limited by these atomic processes, independent of the physical process which is causing the change in the solar atmosphere. Rapid heating can lead to an initial freezing-in of abundances of some ions; observations of at least one low- and one high-excitation line from such an ion would permit studies of the time evolution of the emission measure and temperature. In a very limited number of cases, rapid cooling leads to freezing-in of the abundance of an ion and observations of a low-excitation line of this ion will not yield accurate information about the thermal evolution. Thus, future observations of Mgx 609 Å should be augmented by simultaneous observation at another wavelength, such as 63 Å. In addition, with the ability to produce images in isolated spectral lines it becomes possible to select those for which rapid variability is observable, such asOVII, rather than lines which were selected on the basis of previous hardware constraints, such asOVII. Title: X-ray bright points and He i λ 10830 dark points Authors: Golub, L.; Harvey, K. L.; Herant, M.; Webb, D. F. Bibcode: 1989SoPh..124..211G Altcode: Using near-simultaneous full disk solar X-ray images and HeI λ10830 spectroheliograms from three rocket flights, we compare dark points identified on the HeI maps with X-ray bright points identified on the X-ray images. We find that for the largest and most obvious features there is a strong correlation: most HeI dark points correspond to X-ray bright points. However, about two-thirds of the X-ray bright points were not identified on the basis of the helium data alone. Once an X-ray feature is identified it is almost always possible to find an underlying dark patch of enhanced HeI absorption which, however, would not a priori have been selected as a dark point. Therefore, the HeI dark points, using current selection criteria, cannot be used as a one-to-one proxy for the X-ray data. HeI dark points do, however, identify the locations of the stronger X-ray bright points. Title: A Study of Dissipative Structures in the Solar Corona with High-Resolution NIXT Images Authors: Gomez, D.; Martens, P. C. H.; Golub, L. Bibcode: 1989BAAS...21R1150G Altcode: No abstract at ADS Title: X-ray bright points and He I lambda 10830 dark points Authors: Golub, L.; Harvey, K. L.; Herant, M.; Webb, D. F. Bibcode: 1989sxsr.rept.....G Altcode: Using near-simultaneous full disk Solar X-ray images and He I 10830 lambda, spectroheliograms from three recent rocket flights, dark points identified on the He I maps were compared with X-ray bright points identified on the X-ray images. It was found that for the largest and most obvious features there is a strong correlation: most He I dark points correspond to X-ray bright points. However, about 2/3 of the X-ray bright points were not identified on the basis of the helium data alone. Once an X-ray feature is identified it is almost always possible to find an underlying dark patch of enhanced He I absorption which, however, would not a priori have been selected as a dark point. Therefore, the He I dark points, using current selection criteria, cannot be used as a one-to-one proxy for the X-ray data. He I dark points do, however, identify the locations of the stronger X-ray bright points. Title: Fabrication and testing of large area multilayer coated x-ray optics Authors: Spiller, Eberhard; Golub, Leon Bibcode: 1989ApOpt..28.2969S Altcode: The procedures developed for the production and testing of multilayer X-ray mirrors on large figured optical surfaces are discussed. Methods which are generally useful for characterizing the performance of such optics are presented, as well as specific results from the production of a 25-cm-diameter Ritchey-Chretien telescope for a wavelength of 63.5 A. The latter is a two-mirror system, which places additional stringent requirements upon the accuracy and quality of the coatings. Title: Analysis of the 23 June 1988 flare using normal incidence x-ray telescope multilayer x-ray images Authors: Golub, Leon; Herant, Marc Bibcode: 1989SPIE.1160..629G Altcode: 1989xeoa.conf..629G Results obtained during the June 23, 1988 flight of the normal incidence X-ray telescope (NIXT) sounding rocket payload are reported. The telescope primary is 25 cm in diameter, in a 750 cm e.f.l. (f/30) Ritchey-Chretien configuration, with multilayer coatings on the optics designed to image the Fe XVI and Mg X coronal emission lines near 63.5 A. Images of the onset phase of a large (M8) Solar flare were recorded during the flight on a modified T-max 400 film manufactured by Kodak. Some of the results obtained by comparison of the NIXT data with ground-based observations of the sun obtained simultaneously to the flight are also reported. Title: Double crystal multilayer x-ray monochromator Authors: Golub, Leon; Quillen, Alice C.; Spiller, Eberhard Bibcode: 1989SPIE.1160..176G Altcode: No abstract at ADS Title: Filters for soft X-ray solar telescopes. Authors: Spiller, E.; Grebe, K.; Golub, L. Bibcode: 1989SPIE.1160...66S Altcode: 1989xeoa.conf...66S Soft X-ray telescopes require filters that block visible and infrared light and have good soft X-ray transmission. The optical properties of possible materials are discussed and the fabrication and testing methods for the filters used in a 10 inch normal incidence telescope for λ = 63 Å are described. The best performances in the λ = 44 - 114 Å wavelengths range is obtained with foils of carbon and rhodium. Title: A Normal Incidence X-ray Telescope (NIXT) sounding rocket payload Authors: Golub, Leon Bibcode: 1989sao..reptQ....G Altcode: Work on the High Resolution X-ray (HRX) Detector Program is described. In the laboratory and flight programs, multiple copies of a general purpose set of electronics which control the camera, signal processing and data acquisition, were constructed. A typical system consists of a phosphor convertor, image intensifier, a fiber optics coupler, a charge coupled device (CCD) readout, and a set of camera, signal processing and memory electronics. An initial rocket detector prototype camera was tested in flight and performed perfectly. An advanced prototype detector system was incorporated on another rocket flight, in which a high resolution heterojunction vidicon tube was used as the readout device for the H(alpha) telescope. The camera electronics for this tube were built in-house and included in the flight electronics. Performance of this detector system was 100 percent satisfactory. The laboratory X-ray system for operation on the ground is also described. Title: Solar and stellar coronal plasmas Authors: Golub, Leon Bibcode: 1989sao..reptR....G Altcode: Progress in observational, theoretical, and radio studies of coronal plasmas is summarized. Specifically work completed in the area of solar and stellar magnetic fields, related photospheric phenomena and the relationships between magnetism, rotation, coronal and chromospheric emission in solar-like stars is described. Also outlined are theoretical studies carried out in the following areas, among others: (1) neutral beams as the dominant energy transport mechanism in two ribbon-flares; (2) magneto hydrodynamic and circuit models for filament eruptions; and (3) studies of radio emission mechanisms in transient events. Finally, radio observations designed for coronal activity studies of the sun and of solar-type coronae are described. A bibliography of publications and talks is provided along with reprints of selected articles. Title: High-resolution imaging of the solar corona. Authors: Golub, L. Bibcode: 1989BAAS...21..848G Altcode: No abstract at ADS Title: The M8.1 Flare of 1988JUN23 - Part One Authors: Herant, M.; Golub, L.; Neidig, D. F. Bibcode: 1989SoPh..124..145H Altcode: Hα observations of two-ribbon flares often show secondary brightenings which are not directly spatially connected with the main center of activity but which are correlated in time with the primary impulsive flare. We present here a mechanism which explains these secondary brightenings via the reconnection of magnetic loops which are tied to only one of the two ribbons, in contrast with the loops responsible for the main flare which are tied to both ribbons. The distant footpoint is then interpreted as the site of the secondary brightening. We apply our model to the two-ribbon flare of 17:52 UT, 23 June, 1988, which started during the rocket flight of the Normal Incidence X-ray Telescope. Title: High-Resolution Imaging of the Solar Corona Authors: Golub, L. Bibcode: 1989BAAS...21R.848G Altcode: No abstract at ADS Title: An Intensified CCD EUV Camera for the SOHO/CDS Experiment Authors: Golub, L.; Kalata, K.; Poland, A. I.; Thomas, R. J. Bibcode: 1988BAAS...20..980G Altcode: No abstract at ADS Title: Multi-Wavelength Observations of the 23 June 1745UT M8 Flare Authors: Herant, M.; Golub, L.; Mickey, D.; Neidig, D.; Slater, G. Bibcode: 1988BAAS...20R.977H Altcode: No abstract at ADS Title: A high resolution phosphor screen for XUV detectors Authors: Sams, B. J., III; Golub, L.; Kalata, K. Bibcode: 1988JPhE...21..302S Altcode: The paper presents an XUV detector with a spatial resolution of about 6 microns designed to fly on the normal incidence X-ray telescope (NIXT) rocket package. The telescope is a 254 mm diameter Ritchey-Chretien system which relies on unusually high accuracy multilayer coatings to image active regions on the sun. The coatings are reflective in a narrow band centered on a wavelength near 6.3 nm; thus the detector's job is to convert the XUV image into an electronic format which can be stored on tape or relayed to the ground via telemetry. This paper is primarily concerned with how the X-rays are converted into a very high resolution visible light image which can be sensed and read out by the image processing electronics. Title: Conference on X-Ray Instrumentation in Astronomy, II. Proceedings of the Meeting, San Diego, CA, Aug. 15-17, 1988. Authors: Golub, Leon Bibcode: 1988SPIE..982.....G Altcode: Various papers on X-ray instrumentation in astronomy are presented. Individual topics addressed include: concentrating hard X-ray collector, advanced X-ray Astrophysics Facility high resolution camera, Fano-noise-limited CCDs, linear CCD with enhanced X-ray quantum efficiency, advances in microchannel plate detectors, X-ray imaging spectroscopy with EEV CCDs, large aperture imaging gas scintillation proportional counter, all-sky monitor for the X-ray Timing Explorer, and miniature satellite technology capabilities for space astronomy. Also discussed are: high-resolution X-ray spectroscopy using microcalorimeters, high-throughput X-ray astrophysics cornerstone, gas mixtures for X-ray proportional counters, transmission grating spectrometer for SPEKTROSAT, efficiency of X-ray reflection gratings, soft X-ray spectrographs for solar observations, observability of coronal variations, Berkeley extreme-UV calibration facility, SURF-II radiometric instrumentation calibration facility, and evaluation of toroidal gratings in the EUV. Title: Comments on the observability of coronal variations. Authors: Golub, Leon; Quillen, Alice C.; Hartquist, Thomas W. Bibcode: 1988SPIE..982..311G Altcode: 1988xia..conf..311G The authors discuss the possibilities opened up by the newly-available soft X-ray and XUV multilayer coated optics for observations of the solar outer atmosphere and corona. Presently available material combinations and the achievable quality of coatings provide basic limitations to the possible spectral bands which can be observed. The spectral regions within which solar emission lines are formed are compared with the available multilayer passbands in a discussion of the types of instruments which one can consider building. In addition, the authors discuss briefly the possible spectral lines which are of interest for studying the various temperature regimes and variability time constants which are known to be present in the solar atmosphere. Title: Design considerations for soft X-ray television imaging detectors. Authors: Kalata, Kenneth; Golub, Leon Bibcode: 1988SPIE..982...64K Altcode: 1988xia..conf...64K Television sensors such as CCD's and vidicons can be coupled to convertors and (typically) image intensifiers to obtain active areas, high flux capabilities, quantum efficiency, high time resolution, or ease of construction, and operation that may not be obtained with a directly illuminated sensor in the X-ray and XUV range. A general purpose system which makes use of these capabilities for a number of applications is described. Some of the capabilities and properties of this type of system are discussed, as are some of the considerations that should be kept in mind when configuring a system of this type. Title: Rapid, Low-Level X-Ray Variability in Active Late-Type Dwarfs Authors: Ambruster, Carol W.; Sciortino, Salvatore; Golub, L. Bibcode: 1987ApJS...65..273A Altcode: The authors report the detection of rapid (a few hundred to >1000 s) quiescent variability, at ≥99% significance, in 24 of 34 Einstein IPC observations of 19 active K and M dwarfs. The IPC light curve and a plot of the variability analysis (using a new, statistically rigorous form of χ2 analysis) are given for each observation. The quiescent fluctuations appear not to fall on an extension of the N(S) curve for stellar X-ray flares. The authors discuss solar analogs and the recent suggestions that low-level flaring heats quiescent X-ray coronae. Title: High Resolution Imaging X-ray Detector Authors: Golub, L.; Kalata, K. Bibcode: 1987BAAS...19.1136G Altcode: No abstract at ADS Title: Comparison of Predicted vs. Measured Stellar Magnetic Fields Authors: Quillen, A.; Golub, L.; Harnden, F. R., Jr.; Saar, S. Bibcode: 1987BAAS...19.1027Q Altcode: No abstract at ADS Title: A normal incidence high resolution X-ray telescope for solar coronal observations Authors: Golub, Leon Bibcode: 1987sao..reptS....G Altcode: The preflight preparation of the multilayer mirror fabrication and testing, integration and testing, and WSMR activities are described. Post-flight analysis shows that all payload systems and subsystems performed well within acceptable limits, with the sole exception of the light-blocking prefilters. Suggested corrective actions were discussed. Refurbishment and reflight are then described. Title: Einstein Observatory Survey of X-Ray Emission from Solar-Type Stars: The Late F and G Dwarf Stars Authors: Maggio, A.; Sciortino, S.; Vaiana, G. S.; Majer, P.; Bookbinder, J.; Golub, L.; Harnden, F. R., Jr.; Rosner, R. Bibcode: 1987ApJ...315..687M Altcode: Results of a volume-limited X-ray survey of stars of luminosity classes IV and V in the spectral range F7-G9 observed with the Einstein Observatory are presented. Using survival analysis techniques, the stellar X-ray luminosity function in the 0.15-4.0 keV energy band for both single and multiple sources. It is shown that the difference in X-ray luminosity between these two classes of sources is consistent with the superposition of individual components in multiple-component systems, whose X-ray properties are similar to those of the single-component sources. The X-ray emission of the stars in our sample is well correlated with their chromospheric CA II H-K line emission and with their projected equatorial rotational velocity. Comparison of the X-ray luminosity function constructed for the sample of the dG stars of the local population with the corresponding functions derived elsewhere for the Hyades, the Pleiades, and the Orion Ic open cluster confirms that the level of X-ray emission decreases with stellar age. Title: High resolution imaging detector for use with a soft X-ray telescope. Authors: Golub, Leon; Kalata, Kenneth Bibcode: 1987SPIE..733..533G Altcode: An advanced extremely high-resolution telescope utilizing multilayer coated optics for imaging in the soft X-ray regime is being developed as well as a high-efficiency electronic detector system capable of meeting all of the stringent requirements of coronal studies. The construction of a 2048 x 2048 system with a pixel size of 5 microns, capable of handling count rates up to a few x 100,000 cts/s in the photon counting mode, and substantially higher rates in the A/D mode is discussed. The current status of the development program is discussed and results are presented. Title: A normal incidence X-ray telescope Authors: Golub, Leon Bibcode: 1987sao..reptR....G Altcode: The postflight performance evaluation of the X-ray telescope was summarized. All payload systems and subsystems performed well within acceptable limits, with the sole exception of the light-blocking prefilters. Launch, flight and recovery were performed in a fully satisfactory manner. The payload was recovered in a timely manner and in excellent condition. The prefilter performance analysis showed that no X-ray images were detected on the processed flight film. Recommendations for improved performance are listed. Title: Magnetogram and soft X-ray comparisons of XBP and ER. Authors: Golub, Leon; Harvey, Karen L.; Webb, David F. Bibcode: 1986NASCP2442..365G Altcode: 1986copp.nasa..365G The potential importance of the smallest emerging flux regions on the sun was discussed in numerous publications. The association between the objects seen in ground-based data, such as high resolution magnetrons or H alpha and soft X-ray data has produced results which are often contradictory. In the hope of resolving the present impasse, as much simultaneous soft X-ray and magnetogram data as possible were assembled in order to clarify the situation. It was found that separation of magnetic features into chance encounters and emerging flux makes some difference in overlapp with X-ray bright points (XBPs), although the effect is not overwhelming. The difference in solar cycle dependence between XBP and ephemeral regions is not explainable in terms of the results. Title: Rapid X-ray Variability of Quiescent Late-Type Dwarfs: Implications for Coronal Heating Authors: Ambruster, C. W.; Sciortino, S.; Golub, L. Bibcode: 1986BAAS...18..985A Altcode: No abstract at ADS Title: Rapid X-Ray Variability in Einstein Observations of K and M Dwarfs Authors: Ambruster, C.; Sciortino, S.; Golub, L. Bibcode: 1986LNP...254..219A Altcode: 1986csss....4..219A No abstract at ADS Title: X-Ray Spectra and the Rotation-Activity Connection of RS Canum Venaticorum Binaries Authors: Majer, P.; Schmitt, J. H. M. M.; Golub, L.; Harnden, F. R., Jr.; Rosner, R. Bibcode: 1986ApJ...300..360M Altcode: Results are presented from a survey of RS CVn binaries which were observed with the imaging proportional counter (IPC) on board the Einstein Observatory. Spectral analyses of the IPC pulse height spectra show that the coronae of RS CVn binaries always contain hot gas with temperatures in excess of 10 to the 7th K, similar to active late-type main-sequence stars, and that at least two temperature components are necessary to account for the higher quality IPC spectra (when absorption is unimportant). It is argued that these bimodal temperature distributions found by the IPC are indicative of true distributions of emission measure versus temperature that are continuous (just as is the case of magnetically confined coronal plasma loops observed on the sun). It is further shown that none of the derivable X-ray characteristics of RS CVn binaries depend on rotation period, implying that previous claims of period-activity relationships in RS CVn binaries were unfounded. Title: Highlights of the Einstein Survey of Cool Stars Authors: Bookbinder, J.; Golub, L.; Rosner, R. Bibcode: 1986LNP...254...97B Altcode: 1986csss....4...97B No abstract at ADS Title: A normal incidence X-ray telescope sounding rocket payload Authors: Golub, L. Bibcode: 1985sao..reptT....G Altcode: Progress is reported on the following major activities on the X-ray telescope: (1) complete design of the entire telescope assembly and fabrication of all front-end components was completed; (2) all rocket skin sections, including bulkheads, feedthroughs and access door, were specified; (3) fabrication, curing and delivery of the large graphite-epoxy telescope tube were completed; (4) an engineering analysis of the primary mirror vibration test was completed and a decision made to redesign the mirror attachment system to a kinematic three-point mount; (5) detail design of the camera control, payload and housekeeping electronics were completed; and (6) multilayer mirror plates with 2d spacings of 50 A and 60 A were produced. Title: X-ray spectra and the rotation-activity connection of RS CVn binaries. Authors: Majer, P.; Schmitt, J. H. M. M.; Golub, L.; Harnden, F. R.; Rosner, R. Bibcode: 1985ESASP.239..141M Altcode: 1985cxrs.work..141M Results from a survey of RS CVn binaries which were observed with the Imaging Proportional Counter (IPC) on board the Einstein Observatory are presented. Spectral analyses of the IPC pulse height spectra show that the coronae of RS CVn binaries always contain hot gas with temperatures 10 million K, similar to active late-type main sequence stars, and that at least 2 temperature components are necessary to account for the higher quality IPC spectra (when absorption is unimportant). It is argued that these bimodal temperature distributions indicate true distributions of emission measure vs temperature that are continuous (just as is the case for magnetically-confined coronal plasma loops observed on the Sun). It is shown that none of the derivable X-ray characteristics of RS CVn binaries depend on rotation period, implying that claims of period-activity relationships in RS CVn binaries are unfounded. Title: Implications of the 1400 MHz Flare Emission from AD Leo for the Emission Mechanism and Flare Environment Authors: Holman, G. D.; Bookbinder, J.; Golub, L. Bibcode: 1985ASSL..116...35H Altcode: 1985rst..conf...35H High brightness temperature spikes have been observed during a radio flare on the M-dwarf flare star AD Leo (Lang et al., 1983). Their high brightness temperature (greater than 10 to the 13th K) and circular polarization indicate that a coherent radiation mechanism must be responsible for the spike emission. The underlying flare emission, which is identified with a low polarization, gradual component, was found not to be spiky to within the 200 ms time resolution of the observations. This note is concerned primarily with this nonspiky emission. Title: Einstein X-ray survey of the Pleiades : the dependence of X-ray emission on stellar age. Authors: Micela, G.; Sciortino, S.; Serio, S.; Vaiana, G. S.; Bookbinder, J.; Golub, L.; Harnden, F. R., Jr.; Rosner, R. Bibcode: 1985ApJ...292..172M Altcode: The data obtained with two pointed observations of 1 deg by 1 deg fields of the Pleiades region have been analyzed, and the results are presented. The maximum-likelihood X-ray luminosity functions for the Pleiades G and K stars in the cluster are derived, and it is shown that, for the G stars, the Pleiades X-ray luminosity function is significantly brighter than the corresponding function for Hyades G dwarf stars. This finding indicates a dependence of X-ray luminosity on stellar age, which is confirmed by comparison of the same data with median X-ray luminosities of pre-main sequence and local disk population dwarf G stars. It is suggested that the significantly larger number of bright X-ray sources associated with G stars than with K stars, the lack of detection of M stars, and the relatively rapid rotation of the Pleiades K stars can be explained in terms of the onset of internal differential rotation near the convective envelope-radidative core interface after the spin-up phase during evolution to the main sequence. Title: Solar and stellar coronal plasmas Authors: Golub, L. Bibcode: 1985sao..reptR....G Altcode: Progress made in describing and interpreting coronal plasma processes and the relationship between the solar corona and its stellar counterparts is reported. Topics covered include: stellar X-ray emission, HEAO 2 X-ray survey of the Pleiades, closed coronal structures, X-ray survey of main-sequence stars with shallow convection zones, implications of the 1400 MHz flare emission, and magnetic field stochasticity. Title: A normal incidence, high resolution X-ray telescope for solar coronal observations Authors: Golub, L. Bibcode: 1985sao..reptQ....G Altcode: The following major activities were advanced or completed: complete design of the entire telescope assembly and fabrication of all front-end components; specification of all rocket skin sections including bulkheads, feedthroughs and access door; fabrication, curing, and delivery of the large graphite-epoxy telescope tube; engineering analysis of the primary mirror vibration test was completed and a decision made to redesign the mirror attachment to a kinematic three-point mount; detail design of the camera control, payload and housekeeping electronics; and multilayer mirror flats with 2d spacings of 50 A and 60 A. Title: X-Ray Variability in K and M Dwarfs Observed by Einstein Authors: Ambruster, C.; Sciortino, S.; Golub, L. Bibcode: 1985BAAS...17..598A Altcode: No abstract at ADS Title: An Einstein Observatory X-ray survey of main-sequence stars with shallow convection zones. Authors: Schmitt, J. H. M. M.; Golub, L.; Harnden, F. R., Jr.; Maxson, C. W.; Rosner, R.; Vaiana, G. S. Bibcode: 1985ApJ...290..307S Altcode: The results of an X-ray survey of bright late A and early F stars on the main B-V sequence between 0.1 and 0.5 are presented. All the stars were observed with the Einstein Observatory for a period of at least 500 seconds. The survey results show significantly larger X-ray luminosities for the sample binaries than for the single stars. It is suggested that the difference is due to the presence of multiple X-ray sources in binaries. It is shown that the X-ray luminosities for single stars increase rapidly with increasing color, and that the relation Lx/Lbol is equal to about 10 to the -7th does not hold for A stars. No correlation was found between X-ray luminosity and projected equatorial rotation velocity. It is argued on the basis of the observations that X-ray emission in the sample stars originated from coronae. The available observational evidence supporting this view is discussed. Title: Closed coronal structures. VI. Far-ultraviolet and X-ray emission from active late-type stars and the applicability of coronal loop models. Authors: Giampapa, M. S.; Golub, L.; Peres, G.; Serio, S.; Vaiana, G. S. Bibcode: 1985ApJ...289..203G Altcode: We present far-ultraviolet line fluxes of prominent transition region emission lines, as obtained with the International Ultraviolet Explorer satellite, for a sample of solar-type stars. We combine the ultraviolet observations with existing soft X-ray measurements obtained by the Einstein Observatory (HEAO 2). We utilize the resulting data set and a new coronal loop model numerical code developed at the Harvard-Smithsonian Center for Astrophysics to perform a preliminary investigation of the applicability of coronal loop models to solar-type stars. In a few cases, reasonable agreement between the predictions of single-component, coronal loop model atmospheres and the observational data is achieved for a relatively well-defined, plausible range of values in the pressure-filling factor (p, f) plane. In general, however, we find that the addition of non- simultaneous ultraviolet observations to a previously acquired soft X-ray data set does not provide a sufficient constraint on the range of possible loop filling factors and pressures for loop model atmospheres that may be producing the observed X-ray and transition region emissions. We discuss the origins of the discrepancies between the model results and the observations within the context of (1) stellar variability, (2) multiple coronal components, and (3) the presence of relatively low temperature loops that give rise to far-ultraviolet emission but not to coronal X-ray emission. We suggest on the basis of the results presented in this investigation that in order to verify the applicability of coronal loop models to solar-type stars, simultaneous far-ultraviolet and moderate spectral resolution X-ray observations will eventually have to be obtained. Title: On stellar X-ray emission. Authors: Rosner, R.; Golub, L.; Vaiana, G. S. Bibcode: 1985ARA&A..23..413R Altcode: Stellar X-ray astronomy represents an entirely new astronomical discipline which has emerged during the past five years. It lies at the crossroads of solar physics, stellar physics, and general astrophysics. The present review is concerned with the main physical problems which arise in connection with a study of the stellar X-ray data. A central issue is the extent to which the extrapolation from solar physics is justified and the definition (if possible) of the limits to such extrapolation. The observational properties of X-ray emission from stars are considered along with the solar analogy and the modeling of X-ray emission from late-type stars, the modeling of X-ray emission from early-type stars, the physics of stellar X-ray emission, stellar X-ray emission in the more general astrophysical context, and future prospects. Title: X-ray emission from solar-type stars: X-ray luminosity function of late F and G stars. Authors: Maggio, A.; Bookbinder, J.; Harnden, F. R., Jr.; Golub, L.; Majer, P.; Rosner, R.; Vaiana, G. S. Bibcode: 1985xra..conf...39M Altcode: 1984xra..conf...39M The authors present preliminary results from a volume-limited survey of X-ray emission from late F and G dwarf stars. They have obtained count rates or upper limits at the locations of catalogued stars within 25 parsecs for which an observation of the Einstein Imaging Proportional Counter was available. They have constructed X-ray luminosity functions for the whole sample and for selected subsamples of binary and non-binary sources. Title: Theory tested by means of the stars. Authors: Golub, L. Bibcode: 1985NASCP2358..106G Altcode: 1985onhm.rept..106G Recent X-ray observations of M dwarfs and Pleiades stars are used to discuss the relation between surface magnetic fields and the heating of stellar coronae. The viability of the α-ω dynamo model for stellar magnetic fields is then examined. Title: Construction of a multilayered X-ray telescope for solar coronal studies from space. Authors: Golub, L.; Nystrom, G.; Spiller, E.; Wilczynski, J. Bibcode: 1985SPIE..563..266G Altcode: The construction and testing of soft x-ray Ritchey-Chretien aplanatic telescope which is to be flown on a NASA sounding rocket in 1986 for very high resolution studies of the solar corona are discussed. Goals include figuring, polishing and measuring the mirror surfaces to tolerances exceding the 5000 A wavelength diffraction limit while achieving a superpolished surface finish, and the development of a structural design to withstand the rigors of the launch. Multilayer coatings are used to achieve usable reflectivity in the soft X-ray regime, and the design goal is for spatial resolution of 1/4 sec. Future applications are discussed. Title: Active late-type stars and the applicability of coronal loop models. Authors: Giampapa, M. S.; Golub, L.; Peres, G.; Serio, S.; Vaiana, G. S. Bibcode: 1984NASCP2349..454G Altcode: 1984fiue.rept..454G; 1984IUE84......454G Far ultraviolet IUE observations of a sample of solar type stars were combined with existing soft X-ray measurements obtained by HEAO B. The resulting data set was utilized and a new coronal loop model numerical code was developed to perform a preliminary investigation of the applicability of coronal loop models to solar-type stars. Reasonable agreement was found to exist between the predictions of single-component coronal loop model atmospheres. It was demonstrated that semi-empirical, coronal loop models can be applied to account for observed stellar transition region and coronal emission. This result is corroborative evidence for the presence of magnetic field structures analogous to solar coronal loops on the surfaces of solar-type stars. It is suggested that stellar transition region emission arises predominantly from the base of quiescent coronal loop configurations. Title: A normal incidence, high resolution X-ray telescope for solar coronal observations Authors: Golub, L. Bibcode: 1984sao..reptT....G Altcode: Efforts directed toward the completion of an X-ray telescope assembly design, the procurement of major components, and the coordination of optical fabrication and X-ray multilayer testing are reported. Title: An X-ray Survey of Solar-Type Stars Authors: Bookbinder, J. A.; Majer, P.; Golub, L.; Rosner, R. Bibcode: 1984BAAS...16Q.940B Altcode: No abstract at ADS Title: Stellar chromospheres and coronae in the Ursa Major cluster stars. Authors: Walter, F. M.; Linsky, J. L.; Simon, T.; Golub, L.; Vaiana, G. S. Bibcode: 1984ApJ...281..815W Altcode: IUE spectra of 18 proposed members of the Ursa Major Cluster and Einstein X-ray images of 11 of these stars are discussed. Thirteen stars, six in the nucleus and seven in the extended comoving stream, are probably true members of the UMa Cluster in that their bright ultraviolet and X-ray surface fluxes indicate youth. Four stars, one in the nucleus and three in the stream, exhibit weak ultraviolet and/or X-ray emission suggesting that they are old field stars that have the same space motion as the UMa Cluster. The X-ray surface fluxes of the UMa Cluster stars appear to be brighter than those of the Hyades Cluster stars, consistent with their relative ages. It is argued that chromospheres and transition regions could be present in dwarf stars hotter than B-V of about 0.30, but are unobservable in IUE spectra due to the rapid increase in photospheric flux in hotter stars. Title: A normal incidence, high resolution X-ray telescope for solar coronal observations Authors: Golub, L. Bibcode: 1984sao..reptQ....G Altcode: A Normal Incidence high resolution X-ray Telescope is reported. The design of a telescope assembly which, after fabrication, will be integrated with the mirror fabrication process is described. The assembly is engineered to fit into the Black Brant rocket skin to survive sounding rocket launch conditions. A flight ready camera is modified and tested. Title: Erratum - Einstein Observations of X-Ray Emission from A-Stars Authors: Golub, L.; Harnden, F. R.; Maxson, C. W.; Rosner, R.; Vaiana, G. S.; Cash, W., Jr.; Snow, T. P., Jr. Bibcode: 1984ApJ...278..456G Altcode: No abstract at ADS Title: X-ray Spectra of RS CVn Binaries Authors: Majer, P.; Schmitt, J. H. M.; Golub, L.; Harnden, F. R., Jr.; Rosner, R. Bibcode: 1984BAAS...16..514M Altcode: No abstract at ADS Title: An X-ray Survey of Late-Type Dwarf Stars Authors: Bookbinder, J. A.; Schmitt, J. H. M.; Golub, L.; Rosner, R. Bibcode: 1984BAAS...16..515B Altcode: No abstract at ADS Title: Measurements of Rotational Velocities of F and G Stars Authors: Noci, Giancarlo; Ortolani, Sergio; Rossi, Pierluigi; Golub, Leon Bibcode: 1984LNP...193..105N Altcode: 1984csss....3..105N No abstract at ADS Title: Evolution of solar magnetic flux. Authors: Boris, J. P.; DeVore, C. R.; Golub, L.; Howard, R. F.; Low, B. C.; Sheeley, N. R., Jr.; Simon, G. W.; Tsinganos, K. C. Bibcode: 1984NASRP1120....3B Altcode: Contents: Introduction. Appearance of magnetic flux: models for flux emergence, unexplained observations. Dynamics of surface magnetic flux: magnetic flux transport, magnetic flux structure. Disappearance of magnetic flux: theoretical considerations, observations of flux disappearance. Summary. Title: X-Ray Survey of the Pleiades - Dependence of X-Ray Luminosity on Stellar Age Authors: Micela, G.; Sciortino, S.; Serio, S.; Vaiana, G. S.; Golub, L.; Harnden, F. R.; Rosner, R. Bibcode: 1984IAUS..105..101M Altcode: The authors report preliminary results from an Einstein X-ray survey of the Pleiades. They have analysed a 1°×1° exposure centered over one of the more luminous stars of the cluster (20 Tau, [B7 III]). This field contains ≡62 cluster members out of a total of ≡270 stars with magnitude lower than 14m. (Hertzsprung, 1947). The authors have detected 17 distinct X-ray sources; 16 sources are identified with cluster stars within a distance less than 1arcmin. Title: Solar coronal studies using normal-incidence X-ray optics Authors: Golub, L. Bibcode: 1984AdSpR...4h..75G Altcode: 1984AdSpR...4...75G We describe the progress which has been made in constructing a new type of X-ray telescope, which operates at normal incidence in the soft X-ray region by the use of multilayer coatings. The principles involved in state-of-the-art multilayer technology and some recent high-resolution imaging results are discussed. A rocket payload incorporating a multilayer X-ray mirror is presently being constructed. It is of Ritchey-Chretien design and the expected spatial resolution is 1/4 arcsec. The scientific program for solar coronal studies and future instrumental developments are also discussed. Title: X-Ray Variable Stars in the Pleiades Authors: Sciortino, S.; Micela, G.; Serio, S.; Vaiana, G. S.; Golub, L.; Harnden, F. R., Jr.; Rosner, R. Bibcode: 1983IBVS.2449....1S Altcode: No abstract at ADS Title: X-ray observations of the solar corona. Authors: Golub, L. Bibcode: 1983NASCP2280...45G Altcode: No abstract at ADS Title: X-ray Emission from A and F Stars - What Do We Learn About Convection and Dynamos? Authors: Schmitt, J. H. M.; Golub, L.; Harnden, F. R., Jr.; Maxson, C. W.; Rosner, R. Bibcode: 1983BAAS...15Q.948S Altcode: No abstract at ADS Title: Bright, rapid, highly circularly polarized radio spikes from the M dwarf AD Leonis. Authors: Lang, K. R.; Bookbinder, J.; Golub, L.; Davis, M. M. Bibcode: 1983ApJ...272L..15L Altcode: A rapid sequence of highly polarized spikes was observed during the gradual rise of a longer lasting event in an Arecibo Observatory study of a radio burst at 1400 MHz from the main sequence radio star AD Leo. The maximum flux density of the spikes was 130 mJy, and they had rise times of less than about 200 msec. The rise times provide an upper limit to the linear size of the emitter of 6 billion cm, and an area of less than 0.03 of the star's surface area is inferred, for a spike brightness temperature of more than about 10 to the 13th K. The high brightness temperatures and high degrees of circular polarization are explained in terms of electron-cyclotron maser emission at the second harmonic of the gyrofrequency, in longitudinal magnetic fields of about 250 G. Title: Einstein observations of X-ray emission from A stars. Authors: Golub, L.; Harnden, F. R., Jr.; Maxson, C. W.; Rosner, R.; Vaiana, G. S.; Cash, W., Jr.; Snow, T. P., Jr. Bibcode: 1983ApJ...271..264G Altcode: Results are reported from the combined CfA Stellar Survey of selected bright A stars and an Einstein Guest Observer program for Ap and Am stars. In an initial report of results from the CfA Stellar Surveys by Vaiana et al. (1981) it was noted that the spread in observed X-ray luminosities among the few A stars observed was quite large. The reasons for this large spread was studied by Pallavicini et al. (1981). It was found that the X-ray emission from normal stars is related very strongly to bolometric luminosity for early-type stars and to rotation rate for late-type stars. However, an exception to this rule has been the apparently anomalous behavior of A star X-ray emission, for which the large spread in luminosity showed no apparent correlation with either bolometric luminosity or stellar rotation rate. In the present study, it is shown that the level of emission from normal A stars agrees with the correlation observed for O and B stars. Title: The magnetic field on the RS Canum Venaticorum star lambda Andromeda. Authors: Giampapa, M. S.; Golub, L.; Worden, S. P. Bibcode: 1983ApJ...268L.121G Altcode: A program to detect and measure magnetic flux on the surfaces of late-type stars is discussed. A technique is adopted to deconvolve magnetically insensitive lines from similar, magnetically sensitive lines to infer the degree of Zeeman splitting in the latter lines. These measurements yield values for the magnetic field strength and filling factor (flux). To illustrate the approach, observations of the RS CVn star Lambda And are presented. At the epoch of observation, 1981 April 26, a field strength of 1290 + or - 320 gauss covering 48 + or - 7 percent of this star's surface is found. This measurement compares with an estimate of coronal magnetic flux in the cooler component of the stellar corona of 1110 gauss with a coronal volume filling factor of 75 percent, based on X-ray data for Lambda And. Title: Bright, rapid, highly polarized radio spikes from the M dwarf AD Leo Authors: Lang, K. R.; Bookbinder, J.; Golub, L. Bibcode: 1983tuft.reptS....L Altcode: We have observed a radio burst from the main sequence (dM4.5e) star AD Leo at 1400 MHz from 0536 to 0556 UT on 1983 February 1 at the Arecibo Observatory. A rapid sequence of highly polarized spikes was observed during the gradual rise of a longer lasting, unpolarized event. The maximum flux density of the spikes was S(max) = 130 mJy, and they had rise times less than or approx. 200 ms. The spikes were all 100% left hand circularly polarized with an instrumental uncertainty of 5%. The rise times provide an upper limit to the linear size L less than or approx. 6 x 10 to the 9th power cm for the emitter. Provided that the source is symmetric, it has an area that is less than three hundredths of the star's surface area. In this case, the lower limit to the brightness temperature of the spikes is TB greater than or approx. 10 to the 13th power K. The high brightness temperatures and high degrees of circular polarization are explained in terms of electron-cyclotron maser emission at the second harmonic of the gyrofrequency in longitudinal magnetic fields of strength Hl approx. 250 gauss. The unpolarized gradual component did not exhibit any rapid fluctuations, and it was entirely analogous to the thermal emission of solar bursts. Title: Coordinated Einstein and IUE observations of a disparitions brusques type flare event and quiescent emission from Proxima Centauri. Authors: Haisch, B. M.; Linsky, J. L.; Bornmann, P. L.; Stencel, R. E.; Antiochos, S. K.; Golub, L.; Vaiana, G. S. Bibcode: 1983ApJ...267..280H Altcode: The Einstein Imaging Particle Counter observed a major X-ray flare in its entirety during a 5-hr period of simultaneous observations, with the IUE, of the dM5e flare star Proxima Centauri in August, 1980. The detailed X-ray light curve, temperature determinations during various intervals, and UV line fluxes obtained before, during, and after the flare indirectly indicate a 'two-ribbon flare' prominence eruption. The calculated ratio of coronal to bolometric luminosity for the event is about 100 times the solar ratio. The Proxima Cen corona is analyzed in the context of static loop models, in light of which it is concluded that less than 6% of the stellar surface seems to be covered by X-ray emitting active regions. Title: An X-ray Survey of Main Sequence Stars with Shallow Convection Zones Authors: Schmitt, J. H. M.; Golub, L.; Harnden, F. R., Jr.; Maxson, C. W.; Vaiana, G. S. Bibcode: 1983BAAS...15..673S Altcode: No abstract at ADS Title: X-rays from stars. Authors: Golub, L. Bibcode: 1983Ast....11...66G Altcode: No abstract at ADS Title: Quiescent coronae of active chromosphere stars Authors: Golub, L. Bibcode: 1983ASSL..102...83G Altcode: 1983ards.proc...83G; 1983IAUCo..71...83G Quiescient X-ray emission from M dwarfs and the changes in quiescent levels on time scales from hours to about one year are discussed based on Einstein Observatory data. The coronal temperatures for many of these stars are determined; they are generally hotter than the solar corona and some of the more active dM stars have coronal temperatures of about 10 million K. Arguments in support of the hypothesis that M-dwarf coronae are magnetically dominated are presented. The usefulness of loop model atmosphere calculations in elucidating the coronal heating mechanism and the ways in which observations may be used to test competing theories are examined. The X-ray measuremnts can be used to predict magnetic field strengths on these stars, with testable implications. Title: Empirical scaling laws for coronal heating Authors: Golub, L. Bibcode: 1983IAUS..102..345G Altcode: The origins and uses of scaling laws in studies of stellar outer atmospheres are reviewed with particular emphasis on the properties of coronal loops. Some evidence is presented for a fundamental structuring of the solar corona and the thermodynamics of scaling laws are discussed. It is found that magnetic field-related scaling laws can be obtained by relating coronal pressure, temperature, and magnetic field strength. Available data validate this method. Some parameters of the theory, however, must be treated as adjustable, and it is considered necessary to examine data from other stars in order to determine the validity of the parameters. Using detailed observational data, the applicability of single loop models is examined. Title: The Temperature-Luminosity Dependence of Stellar X-ray Sources Authors: Vaiana, G. S.; Serio, S.; Sciortino, S.; Golub, L.; Maxson, C.; Rosner, R. Bibcode: 1982BAAS...14..945V Altcode: No abstract at ADS Title: X-ray Sources in the Pleiades Authors: Micela, G.; Serio, S.; Vaiana, G. S.; Golub, L. Bibcode: 1982BAAS...14..891M Altcode: No abstract at ADS Title: A Normal Incidence X-ray Telescope for Solar Studies Authors: Golub, L.; Rosner, R.; Vaiana, G. S.; Zombeck, M. V.; Spiller, E.; Wilczynski, J. Bibcode: 1982BAAS...14..976G Altcode: No abstract at ADS Title: X-ray Variability of Late-type Stars Authors: Maggio, A.; Serio, S.; Vaiana, G. S.; Golub, L. Bibcode: 1982BAAS...14R.945M Altcode: No abstract at ADS Title: Active region coronal evolution Authors: Golub, L.; Noci, G.; Poletto, G.; Vaiana, G. S. Bibcode: 1982ApJ...259..359G Altcode: Scaling relations between coronal base pressure and longitudinal photospheric magnetic field strength are tested for the case of a single active region observed for five solar rotations from Skylab. The evolution of measureable quantities, such as coronal thermal energy content, total longitudinal photospheric magnetic flux, region scale size, and peak energy density, is traced throughout the five rotations observed. The theoretically derived scaling law of Golub et al. (1980) is found to provide an acceptable fit to the data throughout the entire evolutionary history of the region from an age of about 3 days to the fully evolved state in which the mature active region merges into the general large-scale structure of the quiet corona. An alternative scaling law obtained by including the results of Galeev et al. (1981), however, is found to provide a somewhat better fit to the data. The study is seen as providing additional justification for the belief that magnetic field-related heating is the operative mechanism in the solar corona. Title: A magnitude limited stellar X-ray survey and the F star X-ray luminosity function. Authors: Topka, K.; Golub, L.; Gorenstein, P.; Harnden, F. R., Jr.; Vaiana, G. S.; Avni, Y.; Rosner, R. Bibcode: 1982ApJ...259..677T Altcode: An X-ray survey has been conducted of stars brighter than visual magnitude 8.5 that have serendipitously fallen into the fields of view of the Imaging Proportional Counter of the Einstein Observatory. The survey includes 227 separate 1 x 1 deg fields, containing 274 stars with a visual magnitude of no more than 8.5 and covering a wide range of spectral types and luminosity classes. X-ray emission was detected from 33 stars, and upper limits have been determined for the remainder of the sample. F type stars dominate the detected sample, and most of these are shown to be dwarfs. An X-ray luminosity function for dF stars has been deduced, and reveals that the average 0.2-4.0 keV luminosity of these stars is around 10 to the 29th erg/sec. Constraints have been placed on the high luminosity tails and medians of the X-ray luminosity functions for other types of stars. Title: STCOEX: The stellar X-ray coronal Explorer. Authors: Vaiana, G. S.; Golub, L.; Maxson, C. W.; Rosner, R.; Zombeck, M. V. Bibcode: 1982SAOSR.392B.253V Altcode: 1982csss....2..253V No abstract at ADS Title: A heating mechanism for the chromospheres of M dwarf stars. Authors: Giampapa, M. S.; Golub, L.; Rosner, R.; Vaiana, G. S.; Linsky, J. L.; Worden, S. P. Bibcode: 1982SAOSR.392A..73G Altcode: 1982csss....2...73G The atmospheric structure of the dwarf M-stars which is especially important to the general field of stellar chromospheres and coronae was investigated. The M-dwarf stars constitute a class of objects for which the discrepancy between the predictions of the acoustic wave chromospheric/coronal heating hypothesis and the observations is most vivid. It is assumed that they represent a class of stars where alternative atmospheric heating mechanisms, presumably magnetically related, are most clearly manifested. Ascertainment of the validity of a hypothesis to account for the origin of the chromospheric and transition region line emission in M-dwarf stars is proposed. Title: Second Cambridge workshop on cool stars, stellar systems, and the sun. Vol. 1. Proceedings of a workshop held at the Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, October 21 - 23, 1981. Authors: Giampapa, M. S.; Golub, L. Bibcode: 1982SAOSR.392A....G Altcode: 1982csss....2A....G No abstract at ADS Title: Chromospheric emission, stellar rotation and X-ray coronae. Authors: Pallavicini, R.; Golub, L.; Rosner, R.; Vaiana, G. Bibcode: 1982SAOSR.392B..77P Altcode: 1982csss....2...77P No abstract at ADS Title: Einstein detection of X-rays from the alf CEN system. Authors: Golub, L.; Harnden, F. R., Jr.; Pallavicini, R.; Rosner, R.; Vaiana, G. S. Bibcode: 1982ApJ...253..242G Altcode: Detection of quiescent X-ray emission from the stellar components of the Alpha Cen system: Alpha Cen A (G2 V) and Alpha Cen B (K1 V) is reported. Contrary to previous theoretical expectations, both stars are found to be X-ray emitters and at about the same level: Lx = 1.2 x 10 to the 27th and 2.8 x 10 to the 27th ergs/s for A and B, respectively; the sum of these values is in agreement with the emission level previously reported for Alpha Cen by Nugent and Garmire (1978). Comparison with previous chromospheric and transition region measurements suggests that Alpha Cen A and B may have changed in relative strength in recent years. The coronal temperature of the combined Cen AB source, which is dominated (approximately 2/3 of the total) by the K star is (2.1 + or - 0.4) x 10 to the 6th K, similar to that of the average solar corona; it is noted that this value is not consistent with the estimate of 5 x 10 to the 5th K quoted by Nugent and Garmire. Title: Preface Authors: Giampapa, Mark; Golub, Leon Bibcode: 1982SAOSR.392D...9G Altcode: 1982csss....2D...9G No abstract at ADS Title: Solar activity - the sun as an X-ray star. Authors: Golub, L. Bibcode: 1982SAOSR.392A..39G Altcode: 1982csss....2...39G The existence and constant activity of the Sun's outer atmosphere are thought to be due to the continual emergence of magnetic fields from the Solar interior and the stressing of these fields at or near the surface layers of the Sun. The structure and activity of the corona are thus symptomatic of the underlying magnetic dynamo and the existence of an outer turbulent convective zone on the Sun. A sufficient condition for the existence of coronal activity on other stars would be the existence of a magnetic dynamo and an outer convective zone. The theoretical relationship between magnetic fields and coronal activity can be tested by Solar observations, for which the individual loop structures can be resolved. A number of parameters however, which enter into the alternative theoretical formulations remain fixed in all Solar observations. To determine whether these are truly parameters of the theory observations need to be extended to nearby stars on which suitable conditions may occur. Title: Stellar contribution to the diffuse soft X-ray background. Authors: Bookbinder, J.; Avni, Y.; Golub, L.; Rosner, R.; Vaiana, G. Bibcode: 1982SAOSR.392A.201B Altcode: 1982csss....2..201B One of the results of the EINSTEIN/C.f.A. X-ray stellar survey was a determination of the contribution of the disk stellar population to the galactic component of the diffuse soft (0.28 - 1.0 keV) X-ray background. This analysis employed both binned and unbinned nonparametric statistical methods that have been developed by Avni, et al. (1980). These methods permitted the use of the information contained in both the 22 detections and 4 upper bounds on the luminosities of 26 dM stars in order to derive their luminosity function. Luminosity functions for earlier stellar types are not yet developed. For these earlier stellar types, the median luminosities as determined by Vaiana, et al., are used (1981), which underestimates their contribution to the background. We find that it is the M dwarfs that dominate the disk population stellar contribution to this background. To calculate the contribution of the stellar sources to the background, simple models both for the spatial distribution of the stars and for the properties of the intervening interstellar medium are used. A model is chosen in which all stellar classes have the same functional form for their spatial distribution: an exponentially decreasing distribution above the galactic equatorial plane, and a uniform distribution within the galactic plane for a region of several kiloparsecs centered on the Sun. Title: Coordinated X-ray, optical and radio observations of flaring activityon YZ Canis Minoris. Authors: Kahler, S.; Golub, L.; Harnden, F. R.; Liller, W.; Seward, F.; Vaiana, G.; Lovell, B.; Davis, R. J.; Spencer, R. E.; Whitehouse, D. R.; Feldman, P. A.; Viner, M. R.; Leslie, B.; Kahn, S. M.; Mason, K. O.; Davis, M. M.; Crannell, C. J.; Hobbs, R. W.; Schneeberger, T. J.; Worden, S. P.; Schommer, R. A.; Vogt, S. S.; Pettersen, B. R.; Coleman, G. D.; Karpen, J. T.; Giampapa, M. S.; Hege, E. K.; Pazzani, V.; Rodono, M.; Romeo, G.; Chugainov, P. F. Bibcode: 1982ApJ...252..239K Altcode: The YZ Canis Minoris (Gliese 285), a late-type dwarf star with Balmer emission (dM4.5e), is a member of the UV Ceti class of flare stars. Obtaining good X-ray observations of a dMe star flare is important not only for understanding the physics of flares but also for testing current ideas regarding the similarity between stellar and solar flares. The Einstein X-ray Observatory has made it possible to conduct X-ray observations of dMe stars with unprecedented sensitivity. A description is presented of the results of a program of ground-based optical and radio observations of YZ CMi coordinated with those of the Einstein Observatory. The observations were carried out as part of a coordinated program on October 25, 26, and 27, 1979, when YZ CMi was on the dawn side of the earth. Comprehensive observational data were obtained of an event detected in all three wavelength regions on October 25, 1979. Title: What heats the solar corona? Authors: Golub, L. Bibcode: 1982Ast....10i..74G Altcode: No abstract at ADS Title: Solar and late-type dwarfs Authors: Golub, L. Bibcode: 1982AdSpR...2i.215G Altcode: 1982AdSpR...2..215G The Einstein Observatory and the IUE satellite have provided the observational basis for a major restructuring in theories of coronal formation for late-type stars. For the first time, coronal and transition region emission from a large sample of low mass (1 Mo) dwarf stars has been directly observed, with the unexpected result that essentially all such stars are x-ray emitters. The Sun, which was previously assumed to be typical, is now known to be at the low end of the x-ray luminosity function for solar-type stars. K- and M-dwarfs are observed to have nearly the same luminosity distributions as G-dwarfs and all of these spectral types have a large spread in x-ray luminosity.

Observationally, there is a strong correlation between the strength of coronal emission in stars with outer convective zones and the rotation rates of these stars. At the present time we have only the beginnings of a satisfactory theoretical explanation for this correlation; although we are beginning to understand the connection between coronal emission strength and the magnetic field, we do not yet understand the stellar dynamo which generates the magnetic field. Studies of the coronal emission of stars may lead to a better understanding of stellar dynamos. Title: Solar corona at high resolution Authors: Golub, L.; Rosner, R.; Zombeck, M. V. Z.; Vaiana, G. S. Bibcode: 1982SPIE..316..149G Altcode: The earth's surface is shielded from solar X rays almost completely by the atmosphere. It is, therefore, necessary to place X-ray detectors on rockets or orbiting satellites. Solar rays were detected for the first time in the late 1940's, using V-2 rockets. In 1960, the first true X-ray images of the sun were obtained with the aid of a simple pinhole camera. The spatial resolution of the X-ray images could be considerably improved by making use of reflective optics, operating at grazing incidence. Aspects of X-ray mirror developments are discussed along with the results obtained in coronal studies utilizing the new devices for the observation of solar X-ray emission. It is pointed out that the major achievements of the Skylab missions were due primarily to the unique opportunity to obtain data over an extended period of time. Attention is given to normal incidence X-ray optics, achievements possible by making use of high spatial resolution optics, and details of improved mirror design. Title: The cool Half of the H-R diagram in soft X-rays. Authors: Ayres, T. R.; Linsky, J. L.; Vaiana, G. S.; Golub, L.; Rosner, R. Bibcode: 1981ApJ...250..293A Altcode: The results of an Einstein Observatory program to map the occurrence of hot coronae (T greater than 1 million K) in the cool half of the Hertzsprung-Russell diagram are reported. F-M dwarfs, and late F through early K star giants characterized by 10,000 K chromospheric and 20,000-200,000 K FUV emission lines were studied in one region, while a second region study included red giants later than K2 III and supergiants later than G5 Ib with weaker chromospheric emission and no high temperature species. Program goals comprised determination of the C IV division as seen in soft X-rays, and identification of stellar parameters which distinguish strong from weak coronal X-ray sources. A summary of target stars, X-ray fluxes, and UV emission profiles is provided, and coronal emissions, comparisons of C IV and wind boundaries, hybrid-spectrum supergiants, the energy balance of stellar outer atmospheres, stellar rotation and coronae, and evolutionary considerations are discussed, along with lines of future research. Title: The stellar contribution to the galactic soft X-ray background Authors: Rosner, R.; Avni, Y.; Bookbinder, J.; Giacconi, R.; Golub, L.; Harnden, F. R., Jr.; Maxson, C. W.; Topka, K.; Vaiana, G. S. Bibcode: 1981ApJ...249L...5R Altcode: Log N-log S relations for stars are constructed based on median X-ray luminosities for dF, dG, and dK stars previously reported for the Einstein Observatory/Center for Astrophysics stellar survey and on a detailed X-ray luminosity function derived here for dM stars, and the stellar contribution to the diffuse soft X-ray background is investigated. The principal results are that stars provide approximately 20% of the soft X-ray background in the 0.28-1.0 keV passband and therefore contribute significantly to the soft X-ray background in this energy range (with dM stars constituting the dominant contributing class), and that the stellar contribution to the diffuse X-ray background in the 0.15-0.28 keV passband is less than approximately 3%. Title: Relations among stellar X-ray emission observed from Einstein, stellar rotation and bolometric luminosity. Authors: Pallavicini, R.; Golub, L.; Rosner, R.; Vaiana, G. S.; Ayres, T.; Linsky, J. L. Bibcode: 1981ApJ...248..279P Altcode: The correlation between observed stellar X-ray luminosities, bolometric luminosities, and projected rotational velocities for stars of various spectral types and luminosity classes are determined. Early type stars (O3 to A5) have X-ray luminosities independent of rotational velocities, and correlating with bolometric luminosities. Late type stars of spectral type G to M have luminosities well correlated to equatorial rotational velocities, and are independent of luminosity class. The dependence of late type stars is found to be equivalent to a relation between the X-ray surface flux and the stellar angular velocity. F stars are intermediate with X-ray luminosities higher than would be predicted on the basis of the early type star relation, although lower than expected from the late type velocity dependence. The location of RS CVn stars as a class is also discussed, and it is found that the heating of late type stellar coronas does not result from direct conversion of ratational energy. Title: Closed coronal structures. III - Comparison of static models with X-ray, EUV, and radio observations Authors: Pallavicini, R.; Peres, G.; Serio, S.; Vaiana, G. S.; Golub, L.; Rosner, R. Bibcode: 1981ApJ...247..692P Altcode: Numerical models of static coronal loops in energy balance are compared with high spatial resolution observations of extreme ultraviolet lines, broad-band X-ray emission, and interferometric observations at 2.8 cm of a solar active region. Difficulties of using scaling laws to test static models of coronal loops are reviewed. The theoretical model used for the comparison is summarized; the detailed X-ray, EUV, and microwave observations of the selected active region are presented; and the comparison of the model with the observations is performed. It is shown that simple static models with conductive flux vanishing at the loop base reproduce satisfactorily the observed properties in the upper portion of loop structures from compact, high-pressure loops in the core of the region to more extended, fainter loops and to large-scale loops interconnecting different active regions. Effects of changing loop parameters are investigated, and it is argued, that in contrast to the present approach, scaling laws cannot be used to discriminate between different static energy balance models. Some discrepancy is found between model predictions and observations for the lower sections of loop structures. Possible causes of the discrepancy are discussed. Title: Results from an extensive Einstein stellar survey. Authors: Vaiana, G. S.; Cassinelli, J. P.; Fabbiano, G.; Giacconi, R.; Golub, L.; Gorenstein, P.; Haisch, B. M.; Harnden, F. R., Jr.; Johnson, H. M.; Linsky, J. L.; Maxson, C. W.; Mewe, R.; Rosner, R.; Seward, F.; Topka, K.; Zwaan, C. Bibcode: 1981ApJ...245..163V Altcode: The preliminary results of the Einstein Observatory stellar X-ray survey are presented. To date, 143 soft X-ray sources have been identified with stellar counterparts, leaving no doubt that stars in general constitute a pervasive class of low-luminosity galactic X-ray sources. Stars along the entire main sequence, of all luminosity classes, pre-main sequence stars as well as very evolved stars have been detected. Early type OB stars have X-ray luminosities in the range 10 to the 31st to 10 to the 34th ergs/s; late type stars show a somewhat lower range of X-ray emission levels, from 10 to the 26th to 10 to the 31st ergs/s. Late type main-sequence stars show little dependence of X-ray emission levels upon stellar effective temperature; similarly, the observations suggest weak, if any, dependence of X-ray luminosity upon effective gravity. Instead, the data show a broad range of emission levels (about three orders of magnitude) throughout the main sequence later than F0. Title: Solar corona at high resolution. Authors: Golub, L.; Rosner, R.; Vaiana, G. S.; Zombeck, M. V. Bibcode: 1981SPIE..316..149G Altcode: No abstract at ADS Title: Solar magnetic fields - The generation of emerging flux Authors: Golub, L.; Rosner, R.; Vaiana, G. S.; Weiss, N. O. Bibcode: 1981ApJ...243..309G Altcode: X-ray observations have provided information about magnetic fields on the sun, and the implications of these observations are discussed. The pattern of small-scale flux emergence is quite different from that of active regions. It is inferred that the small-scale fields originate fairly high in the convective zone, while the fields in active regions have a deeper origin. The small-scale turbulent fields are only loosely related to the fields that define the normal solar cycle. The way in which dynamo models must be modified in the light of these results is indicated. Title: Closed coronal structures. II - Generalized hydrostatic model Authors: Serio, S.; Peres, G.; Vaiana, G. S.; Golub, L.; Rosner, R. Bibcode: 1981ApJ...243..288S Altcode: Numerical computations of stationary solar coronal loop atmospheres are used to extend earlier analytical work. Two classes of loops are examined, namely symmetric loops with a temperature maximum at the top but now having a length greater than the pressure scale height and loops which have a local temperature minimum at the top. For the first class, new scaling laws are found which relate the base pressure and loop length to the base heating, the heating deposition scale height, and the pressure scale height. It is found that loops for which the length is greater than about two to three times the pressure scale height do not have stable solutions unless they have a temperature minimum at the top. Computed models with a temperature inversion at the top are permitted in a wider range of heating deposition scale height values than are loops with a temperature maximum at the top. These results are discussed in relation to observations showing a dependence of prominence formation and stability on the state of evolution of magnetic structures, and a general scenario is suggested for the understanding of loop evolution from emergence in active regions through the large-scale structure phase to opening in coronal holes. Title: Solar magnetism: a new look. Authors: Golub, L. Bibcode: 1981Ast.....9c..66G Altcode: No abstract at ADS Title: The Cool Half of the HR Diagram in Soft X-Rays Authors: Ayres, T. R.; Linsky, J. L.; Vaiana, G. S.; Golub, L.; Rosner, R. Bibcode: 1980BAAS...12..870A Altcode: No abstract at ADS Title: Hα Activity in X-Ray Bright Points and the Origin of Spicules Authors: Moore, R. L.; Golub, L. Bibcode: 1980BAAS...12..817M Altcode: No abstract at ADS Title: Einstein Observations of A-Stars Authors: Golub, L.; Vaiana, G. S.; Snow, T. P.; Cash, W. C. Bibcode: 1980BAAS...12..872G Altcode: No abstract at ADS Title: Transition Region and Corona in Solar Active Regions: Observations and Numerical Modeling Authors: Golub, L.; Pallavicini, R.; Peres, G.; Rosner, R.; Serio, S.; Vaiana, G. S. Bibcode: 1980BAAS...12..908G Altcode: No abstract at ADS Title: X-ray Bright Points and the Solar Cycle Authors: Golub, L. Bibcode: 1980RSPTA.297..595G Altcode: 1980RSLPT.297..595G Soft X-ray filtergrams show the presence on the Sun of large numbers of small, closed regions of coronal emission. These features, called 'X-ray bright points' correspond to small, short-lived regions of emerging magnetic flux. As a function of size or lifetime they form a broad spectrum of activity which is continuous with the active regions. The shape of the Sun's activity spectrum is such that most of all magnetic flux emerging at the surface comes in the form of bright points. From this viewpoint, active regions may be viewed as the long lifetime tail end of the bright point spectrum. Examination of soft X-ray data obtained from 1970 to 1978 shows that the number of bright points appears to be anticorrelated with traditional activity indices such as sunspot number; the anticorrelation persists after corrections are made for obscuration by active regions. Comparison of X-ray data with KPNO magnetograms shows that to within a factor of 2, the average total amount of magnetic flux emerging over the full Sun is constant through the entire period of observation. The solar cycle therefore appears to be more an oscillation in the wavenumber distribution of emerging flux than of the total quantity of magnetic flux produced. Title: Magnetic fields and coronal heating Authors: Golub, L.; Maxson, C.; Rosner, R.; Vaiana, G. S.; Serio, S. Bibcode: 1980ApJ...238..343G Altcode: General considerations concerning the scaling properties of magnetic-field-related coronal heating mechanisms are used to build a two-parameter model for the heating of closed coronal regions. The model predicts the way in which coronal temperature and electron density are related to photospheric magnetic field strength and the size of the region, using the additional constraint provided by the scaling law of Rosner, Tucker, and Vaiana. The model duplicates the observed scaling of total thermal energy content with total longitudinal flux; it also predicts a relation between the coronal energy density (or pressure) and the longitudinal field strength modified by the region scale size. Title: Coordinated X-Ray, Optical, and Radio Observations of Flares from the dMe Star YZ Canis Minoris Authors: Kahler, S. W.; Golub, L.; Harnden, F. R.; Seward, F. D.; Vaiana, G. S. Bibcode: 1980BAAS...12..526K Altcode: No abstract at ADS Title: Association of flaring X-ray bright points with type III bursts Authors: Kundu, M. R.; Gergely, T. E.; Golub, L. Bibcode: 1980ApJ...236L..87K Altcode: Using the swept-frequency radio observations obtained at the Clark Lake Radio Observatory and the X-ray photographs taken by the S-054 experiment aboard Skylab, a search has been made for type III bursts associated with X-ray bright point (XBP) flares. Using temporal as well as spatial criteria for the association, four such events are found over a period of 43 days. The time period was selected in such a way that the level of flare and radio activity was low in order to minimize the chance coincidences. The detection of type III bursts from the flaring XBPs is of great interest, since it identifies them with the flare process, of which XBP flares are thought to be the simplest form. Title: X-Ray Bright Points and the Solar Cycle Authors: Golub, L.; Vaiana, G. S. Bibcode: 1980NASCP2098...75G Altcode: 1980sscs.nasa...75G The shape of the Sun's activity spectrum is such that the majority of all magnetic flux emerging at the surface comes in the form of bright points, i.e., regions living less than two days. Examination of soft X-ray data obtained from 1970 to 1978 shows that the number of bright points appears to be anticorrelated with traditional activity indices, such as sunspot number; the anticorrelation persists after corrections are made for obscuration by active regions. Comparison of X-ray data with KPNO magnetograms shows that to within a factor of two, the average total amount of magnetic flux emerging over the full Sun is constant through the entire period of observation. The Solar cycle therefore appears to be more an oscillation in the wavenumber distribution of emerging flux than of the total quantity of magnetic flux produced. Title: Rotational Variations in the Nonflaring Optical and X-Ray Fluxes of Yz-Canis Authors: Pettersen, B. R.; Kahler, S.; Golub, L.; Vaiana, G. S. Bibcode: 1980SAOSR.389..113P Altcode: 1980csss....1..113P No abstract at ADS Title: Evidence for globally coherent variability in solar magnetic flux emergence Authors: Golub, L.; Vaiana, G. S. Bibcode: 1980ApJ...235L.119G Altcode: We examine the large-scale spatial and temporal variations in the emergence of X-ray bright points on the sun, in order to study the global properties of magnetic flux emergence. Major variations in the rate of flux emergence are observed at all solar latitudes, on a time scale of 3-5 months. The most economical explanation of the observations is that the full sun participated in a single large eruptive event during the available 8 month observing period from Skylab in 1973. The peak of this global event corresponds in time to the eruption of a major complex of activity. Moreover, it appears that the only portion of the solar surface which deviates from the above pattern of behavior is the low latitude region in the vicinity of the AR complex; this area shows a temporary depletion immediately following the AR outburst. The high-latitude regions in both hemispheres show the same variation and appear to lead the low-latitude emergence by approximately 1 month. Title: Decametric radio bursts associated with coronal loop structures Authors: Gergely, T. E.; Kundu, M. R.; Golub, L.; Webb, D. Bibcode: 1980IAUS...86..435G Altcode: The association of X-ray loop structures with type III bursts is examined using soft X-ray (2-54 A) pictures which were obtained from the Skylab S-054 experiment. The properties of meter-decameter wavelength radio bursts (type III) appear to be associated with two different kinds of loop structures: (1) short lived small scale loops, which are found to link magnetic fields of opposite polarity, called X-ray bright points (XBP); and (2) long lasting loop systems which connect opposite magnetic polarities of an active region as well as active region complexes. It is judged that the presence of active region loop complexes on the disk is a necessary yet insufficient condition for the occurrence of a decametric storm and that conditions concerning the geometry of the magnetic field must also be important in the process. Title: X-ray Observations of the α Cen System from EINSTEIN. Authors: Golub, L.; Harnden, F. R., Jr.; Rosner, R.; Topka, K.; Vaiana, G. S. Bibcode: 1979BAAS...11..775G Altcode: No abstract at ADS Title: X-ray Observations of Very Late-Type Dwarf Stars from the EINSTEIN Observatory. Authors: Rosner, R.; Giacconi, R.; Golub, L.; Harnden, F. R., Jr.; Topka, K.; Vaiana, G. S. Bibcode: 1979BAAS...11..776R Altcode: No abstract at ADS Title: On Stars and OB Associations Observed from EINSTEIN. Authors: Harnden, F. R., Jr.; Golub, L.; Rosner, R.; Seward, F.; Topka, K.; Vaiana, G. S. Bibcode: 1979BAAS...11..775H Altcode: No abstract at ADS Title: A Magnitude Limited Stellar Survey with EINSTEIN. Authors: Topka, K.; Golub, L.; Harnden, F. R., Jr.; Gorenstein, P.; Rosner, R.; Vaiana, G. S. Bibcode: 1979BAAS...11..781T Altcode: No abstract at ADS Title: Rapid changes in the fine structure of a coronal "Bright point" and a small coronal "active region". Authors: Sheeley, N. R., Jr.; Golub, L. Bibcode: 1979SoPh...63..119S Altcode: A coronal `bright point' is resolved into a pattern of emission which, at any given time, consists of 2 or 3 miniature loops (each ∼2500 km in diameter and ∼12 000 km long). During the half-day lifetime of the `bright point' individual loops evolved on a time scale ∼6 min. A small `ctive region' seemed to evolve in this way, but the occasional blurring together of several loops made it difficult to follow individual changes. Title: Anticorrelation of X-ray bright points with sunspot number, 1970 - 1978. Authors: Golub, L.; Davis, J. M.; Krieger, A. S. Bibcode: 1979ApJ...229L.145G Altcode: Soft X-ray observations of the solar corona over the period 1970-1978 show that the number of small short-lived bipolar magnetic features (X-ray bright points) varies inversely with the sunspot index. During the entire period from 1973 to 1978 most of the magnetic flux emerging at the solar surface appeared in the form of bright points. In 1970, near the peak of solar cycle 20, the contributions from bright points and from active regions appear to be approximately equal. These observations strongly support an earlier suggestion that the solar cycle may be characterized as an oscillator in wave-number space with relatively little variation in the average total rate of flux emergence. Title: Observational Tests of Magnetic Field-Related Coronal Heating Theories Authors: Golub, L.; Maxson, C.; Rosner, R.; Serio, S.; Vaiana, G. S. Bibcode: 1979BAAS...11R.408G Altcode: No abstract at ADS Title: The relationship between solar activity and coronal hole evolution. Authors: Nolte, J. T.; Davis, J. M.; Gerassimenko, M.; Krieger, A. S.; Solodyna, C. V.; Golub, L. Bibcode: 1978SoPh...60..143N Altcode: We examine the relationship between coronal hole evolution and solar active regions during the Skylab period. We find a tendency for holes to grow or remain stable when the activity nearby, seen as calcium plages and bright regions in X-rays, is predominantly large, long-lived regions. This is consistent with results of previous studies, using somewhat different methods. We also find that there is a significantly higher number of small, short-lived active regions, as indicated by X-ray bright points, in the vicinity of decaying holes than there is near other holes. We interpret this to mean that holes disappear at least in part because they become filled with many small scale, magnetically closed, X-ray emitting features. This interpretation, together with the previously reported observation that the number of X-ray bright points was much larger near solar minimum than it was during the Skylab period, provides a possible explanation for the disappearance of the large, near-equatorial coronal holes at the time of solar minimum. Title: Heating of coronal plasma by anomalous current dissipation. Authors: Rosner, R.; Golub, L.; Coppi, B.; Vaiana, G. S. Bibcode: 1978ApJ...222..317R Altcode: It is shown that there exist heating mechanisms which connect the observed radiative properties of the inner corona in a simple way to the underlying solar magnetic field. The mechanisms considered involve the generation and consequent dissipation of coronal currents. It is argued that the spatially and temporally inhomogeneous nature of the erupting solar magnetic field is an essential element of coronal heating. Unlike heating theories conceived in the context of the 'homogeneous' corona, this class of current heating models incorporates the observed stochastic coronal structuring at the onset, and does not view it as a complication of an otherwise straightforward model. Attention is given to the generation of coronal currents, the flux-tube emergence, the gradual growth and decay of active regions, the energetics of current dissipation, current sheath geometry and heat transport, and anomalous current dissipation. Title: Coronal Heating and Its Relation to Magnetic Field Evolution. Authors: Golub, L.; Rosner, R.; Vaiana, G. S. Bibcode: 1978BAAS...10..440G Altcode: No abstract at ADS Title: Differential rotation rates for short-lived regions of emerging magnetic flux. Authors: Golub, L.; Vaiana, G. S. Bibcode: 1978ApJ...219L..55G Altcode: We have measured the synodic rotation rates of a sample of compact X-ray emission features lasting from 1 day to 7 days, thus bridging the transition between X-ray bright points and active regions. The rotation rate is found to be a function of the lifetime, or size, of the feature; shorter-lived smaller features rotate more slowly than long-lived ones. The rotation rate for features lasting 2 days or less is consistent with that of the photospheric gas. The longest-lived features rotate at a rate about 5% higher, consistent with the sunspot rotation rate. Title: Halpha macrospicules: identification with EUV macrospicules and with flares in X-ray bright points. Authors: Moore, R. L.; Tang, F.; Bohlin, J. D.; Golub, L. Bibcode: 1977ApJ...218..286M Altcode: The paper presents observational evidence that two newly observed transient solar phenomena, EUV macrospicules and X-ray bright-point flares, are closely related. Time-lapse H-alpha filtergram observations of the limb in quiet regions show small surgelike eruptions called H-alpha macrospicules. From the similarity of H-alpha macrospicules and EUV macrospicules, and from comparison of simultaneous H-alpha and He II 304 A observations, we conclude that H-alpha macrospicules are EUV macrospicules viewed in H-alpha, although most EUV macrospicules are too faint in H-alpha to appear on H-alpha filtergrams of normal exposure. From comparison of simultaneous X-ray and H-alpha observations of flares in X-ray bright points situated on the limb, we show that flares in X-ray bright points often produce H-alpha macrospicules. Title: Magnetic properties of X-ray bright points. Authors: Golub, L.; Krieger, A. S.; Harvey, J. W.; Vaiana, G. S. Bibcode: 1977SoPh...53..111G Altcode: Using high resolution KPNO magnetograms and sequences of simultaneous S-054 soft X-ray solar images we have compared the properties of X-ray bright points (XBP) and ephemeral active regions (ER). All XBP appear on the magnetograms as bipolar features, except for very newly emerged or old and decayed XBP. We find that the separation of the magnetic bipoles increases with the age of the XBP, with an average emergence growth rate of 2.2 ± 0.4 km s−1. The total magnetic flux in a typical XBP living about 8 hr is found to be ≈ 2 x 1019 Mx. A proportionality is found between XBP lifetime and total magnetic flux, equivalent to ≈ 1020 Mx per day of lifetime. Title: Solar cycle variation of magnetic flux emergence. Authors: Davis, J. M.; Golub, L.; Krieger, A. S. Bibcode: 1977ApJ...214L.141D Altcode: The number of X-ray bright points (XBP) has been measured from solar X-ray images obtained during two rocket flights in 1976. When compared with the data obtained during the Skylab mission (1973), the number is found to be higher by a factor of 2. As the probability of obtaining the result by chance is less than 1 in 5 million, it is concluded that the number of XBP has increased in the three year interval. As all other indicators of activity have decreased between 1973 and 1976, the cyclical variation of the short-lifetime end of the magnetic-flux-emergence spectrum is out of phase with the solar cycle as defined by active regions or sunspots. Since XBP in 1973 contributed more to the emerging magnetic flux than did active regions, the possibility exists that the total amount of emerging magnetic flux may be maximized at a sunspot minimum. Title: Heating of Coronal Plasma by Anomalous Current Dissipation. Authors: Rosner, R.; Golub, L.; Vaiana, G. S.; Coppi, B. Bibcode: 1977BAAS....9..370R Altcode: No abstract at ADS Title: Observation of spatial and temporal variations in X-ray bright point emergence patterns Authors: Golub, L.; Krieger, A. S.; Vaiana, G. S. Bibcode: 1976SoPh...50..311G Altcode: Observations of X-ray bright points (XBP) over a six-month interval in 1973 show significant variations in both the number density of XBP as a function of heliographic longitude and in the full Sun average number of XBP from one rotation to the next. The observed increases in XBP emergence are estimated to be quivalent to several large active regions emerging per day for several months. The number of XBP emerging at high latitudes also varies, in phase with the low latitude variation and reaches a maximum approximately simultaneous with a major outbreak of active regions. The quantity of magnetic flux emerging in the form of XBP at high latitudes alone is estimated to be as large as the contribution from all active regions. Title: Distribution of lifetimes for coronal soft X-ray broght points. Authors: Golub, L.; Krieger, A. S.; Vaiana, G. S. Bibcode: 1976SoPh...49...79G Altcode: We have measured the lifetimes of all compact emission features visible on three sets of high time resolution soft X-ray images. The spectrum of lifetimes is found to be heavily weighted toward short lifetimes. The number of features present on the disk which live 2-48 hours is at least ten times as great as the number living more than 48 hours. The distribution of lifetimes can be fit in all three cases by a four-parameter function N(t) = Ns exp(-t/τs) + NL exp(-t/τL), with τs = 8.7±0.2, τL = 35±4 and Ns ≈ 10NL. Features living two days or less have a very broad latitude distribution (Golub et al., 1974, 1975) whereas nearly all longer-lived features are found within 30° of the equator. The growth rates of long-lived vs short-lived points are the same to within ≈ 20%, the major difference being that long-lived points continue to grow and generally reach larger sizes. Title: Emergence of Small-Scale Magnetic Fields on the Sun Authors: Golub, L.; Krieger, A. S.; Vaiana, G. S. Bibcode: 1976BAAS....8..333G Altcode: No abstract at ADS Title: Evolutionary Trends in the Development of Coronal Holes and Their Relationship to the Sub Photospheric Magnetic Field Authors: Davis, J. M.; Golub, L. Bibcode: 1976BAAS....8..326D Altcode: No abstract at ADS Title: Identification of Hα Macrospicules with EUV Macrospicules and with Flares in X-Ray Bright Points Authors: Moore, R. L.; Tang, F.; Bohlin, J. D.; Golub, L. Bibcode: 1976BAAS....8..333M Altcode: No abstract at ADS Title: Comment on lifetime determination of solar features. Authors: Golub, L. Bibcode: 1976SoPh...46..115G Altcode: We propose a modification to a commonly used technique for lifetime determination of solar features. Suggestions for practical implementation of the method are presented. In addition, a serious source of bias in lifetime determination from time-ordered data is discussed. Title: Coronal Bright Points Authors: Golub, L.; Krieger, A. S.; Vaiana, G. S. Bibcode: 1976IAUS...71..145G Altcode: No abstract at ADS Title: Observation of a Non-Uniform Component in the Distribution of Coronal Bright Points Authors: Golub, L.; Krieger, A. S.; Vaiana, G. S. Bibcode: 1975SoPh...42..131G Altcode: The longitude distribution of X-ray bright points shows very strong variations when plotted in a heliocentric (Carrington) coordinate system. In addition, the latitude distribution can be interpreted as having two components : a uniformly distributed component and one having a distribution similar to that of active regions, occurring mostly within ±30° of the equator. Title: Temperature and Density Measurements of Coronal Loops Authors: Chase, R. C.; Golub, L.; Krieger, A.; Silk, J. K.; Vaiana, G. S.; Zombeck, M.; Timothy, A. F. Bibcode: 1975BAAS....7..346C Altcode: No abstract at ADS Title: Temporal and Spatial Properties of Coronal Bright Points Authors: Golub, L.; Krieger, A.; Simon, R.; Vaiana, G.; Timothy, A. F. Bibcode: 1975BAAS....7Q.350G Altcode: No abstract at ADS Title: The long term development of the large scale corona and the evolution of coronal holes Authors: Timothy, A. F.; Gerassimenko, M.; Golub, L.; Krieger, A. S.; Petrasso, R.; Vaiana, G. S. Bibcode: 1975xtcg.work...93T Altcode: The evolution of coronal holes and the typical coronal configurations that result in the formation of a hole are investigated using results obtained by the X-ray telescope experiment on the Apollo Telescope Mount. The evolution of one particular hole is traced, the magnetic-field configuration associated with it is examined, and its rotational characteristics between 20 deg S and 50 deg N are analyzed. It is found that coronal holes form in bands of unipolar magnetic field bounded by areas of opposite polarity when patterns of emerging active-region flux produce the appropriate large-scale field pattern. The holes are shown to have lifetime in excess of five solar rotations and to die when the large-scale field pattern is distorted. It is suggested that the observed rigid rotation of a hole, which is in contrast to the differential rotation of the field associated with it, may be explained by the fact that the hole is a source of a recurrent high-velocity solar-wind stream. Title: Time Variations of Solar X-Ray Bright Points Authors: Golub, L.; Kriegher, A. S.; Silk, J. K.; Timothy, A. F.; Vaiana, G. S. Bibcode: 1975IAUS...68...23G Altcode: No abstract at ADS Title: Skylab and the ASE X-ray telescope experiment - A new view of the X-ray corona Authors: Vaiana, G. S.; Chase, R.; Davis, J.; Gerassimenko, M.; Golub, L.; Kahler, S.; Krieger, A. S.; Petrasso, R.; Silk, J. K.; Simon, R. Bibcode: 1975xtcg.work....3V Altcode: A broad description of the Skylab X-ray telescope experiment is given. The design and development of the S-054 X-ray telescope and the X-ray imaging system are reviewed, and the primary telescope is described along with its spectral characteristics, imaging optics, camera, and film. The technique for determining the temperature and emission integral of the coronal plasma from X-ray photographs is outlined. Data are presented on the long-term variation of large-scale coronal structures, the evolution of active regions, and observations of coronal holes and bright points. It is shown that active regions undergo short-term changes related to changes in the photospheric magnetic fields as well as long-term changes in large-scale structure, that the decay of active regions probably contributes to the formation of coronal holes, and that bright points are a distinct class of flaring active regions which seem to be distributed uniformly over the sun. Title: Skylab and the ASE X-ray telescope experiment: a new view of the X-ray corona. Authors: Vaiana, G. S.; Chase, R.; Davis, J.; Gerassimenko, M.; Golub, L.; Kahler, S.; Krieger, A. S.; Petrasso, R.; Silk, J. K.; Simon, R.; Timothy, A. F.; Zombeck, M.; Webb, D. Bibcode: 1975MmArc.104....3V Altcode: No abstract at ADS Title: The long term development of the large scale corona and the evolution of coronal holes. Authors: Timothy, A. F.; Gerassimenko, M.; Golub, L.; Krieger, A. S.; Petrasso, R.; Vaiana, G. S. Bibcode: 1975MmArc.104...93T Altcode: No abstract at ADS Title: Soft X-ray imaging on photographic film. Authors: Haggerty, R.; Simon, R.; Golub, L.; Silk, J. K.; Timothy, A. F.; Krieger, A. S.; Vaiana, G. S. Bibcode: 1975AASPB..10....8H Altcode: No abstract at ADS Title: Solar X-Ray Bright Points Authors: Golub, L.; Krieger, A. S.; Silk, J. K.; Timothy, A. F.; Vaiana, G. S. Bibcode: 1974ApJ...189L..93G Altcode: Preliminary analysis of photographs from the 8-054 X-ray telescope aboard Skylab has shown that bright points have a statistical distribution of lifetimes with a mean of eight hours. The lifetime of a bright point is approximately proportional to its maximum area, which is typically 2 X 108 km2. A small bright core generally develops during the middle part of the bright-point lifetime with area 10 km2. A small fraction of bright points are seen to increase their surface brightness by several orders of magnitude on a time scale of minutes. These "flares" occur at all latitudes from the equator to the poles. To first order, bright points are uniformly distributed across the solar surface. An estimated 1500 X-ray bright points emerge per day, possibly bringing more new magnetic flux to the surface than is contributed by the major active regions. Sukiect headings: X-rays, solar Title: Radon Emanation from the Moon, Spatial and Temporal Variability Authors: Gorenstein, Paul; Golub, Leon; Bjorkholm, Paul Bibcode: 1974Moon....9..129G Altcode: Observations of the lunar surface with the orbiting Apollo Alpha Particle Spectrometer during the Apollo 15 and Apollo 16 missions have shown spatial and temporal variations in radon emission. There are a number of well localized features in the spatial distribution of lunar222Rn and her daughter210Po which apparently correlate with sites of reported transient visual events. There are sources at Aristarchus, Grimaldi and possibly Tsiolkovsky. Activity of210Po shows enhancement at most maria edges at rates far in excess of222Rn activity. This demonstrates unequivocally the presence of time varying radon activity at the maria edges, taking place at the present time. The increased radon emission is probably caused by sporadic internal activity. In analogy to terrestial processes, radon may be merely a trace component accompanying the release of larger quantities of more common gases to the lunar surface. Title: Temporal Behavior of the Coronal Structure of Active Regions Authors: Krieger, A.; Golub, L.; Silk, J. K.; Timothy, A.; Vaiana, G.; Webb, D. Bibcode: 1974BAAS....6..290K Altcode: No abstract at ADS Title: Coronal Bright Points Authors: Golub, L.; Chase, R.; Krieger, A.; Silk, J. K.; Timothy, A.; Vaiana, G. Bibcode: 1974BAAS....6R.287G Altcode: No abstract at ADS Title: Solar X-ray bright points. Authors: Timothy, A.; Golub, L.; Krieger, A.; Silk, J. K.; Vaiana, G. Bibcode: 1974BAAS....6..265T Altcode: No abstract at ADS Title: Detection of Radon Emission at the Edges of Lunar Maria with the Apollo Alpha-Particle Spectrometer Authors: Gorenstein, Paul; Golub, Leon; Bjorkholm, Paul Bibcode: 1974Sci...183..411G Altcode: The distribution of radioactive polonium-210, a decay product of radon-222, shows enhanced concentrations at the edges of lunar maria. Enhancements are seen at the edges of Mare Fecunditatis, Mare Crisium, Mare Smythii, Mare Tranquillitatis, Mare Nubium, Mare Cognitum, and Oceanus Procellarum. The observation is indicative of the transient emission of radon gas from the perimeters of lunar maria. Title: Radon emanation from the moon: spatial and temporal variability. Authors: Gorenstein, P.; Golub, L.; Bjorkholm, P. Bibcode: 1974spre.conf..653G Altcode: No abstract at ADS Title: Dynamic Events in the X-Ray Corona (a Progress Report from the AS&E X-Ray Telescope on Skylab) Authors: Gerassimenko, M.; Golub, L.; Kahler, S.; Petrasso, R. Bibcode: 1974IAUS...57..501G Altcode: No abstract at ADS Title: Dynamic events in the X-ray corona. (A progress report from the AS&E X-ray telescope on Skylab). Authors: Vaiana, G. S.; Krieger, A. S.; Silk, J. K.; Timothy, A. F.; Chase, R. C.; Davis, J.; Gerassimenko, M.; Golub, L.; Kahler, S.; Petrasso, R. Bibcode: 1974IAUS...57..501V Altcode: No abstract at ADS Title: The Long Term Development of the Large Scale Corona and the Evolution of Coronal Holes Authors: Timothy, A. F.; Gerassimenko, M.; Golub, L.; Krieger, A. S.; Petrasso, R.; Vaiana, G. S. Bibcode: 1974OMOAA.104...93T Altcode: No abstract at ADS Title: Detection of a Nonuniform Distribution of Polonium-210 on the Moon with the Apollo 16 Alpha Particle Spectrometer Authors: Bjorkholm, Paul; Golub, Leon; Gorenstein, Paul Bibcode: 1973Sci...180..957B Altcode: The polonium-210 activity of the lunar surface is significantly larger than the activity of its progenitor radon-222. This result establishes unequivocally that radon emanation from the present-day moon varies considerably within the 21-year half-life of lead-210, the parent nuclide of polonium-210. There are large variations and well-localized enhancements in polonium-210 activity over much of the moon's surface. Title: Spatial Non-Homogeneity and Temporal Variability in the Emanation of Radon from the Lunar Surface: Interpretation Authors: Gorenstein, P.; Golub, L.; Bjorkholm, P. Bibcode: 1973LPI.....4..307G Altcode: No abstract at ADS Title: Distribution of 210PO Across the Apollo 16 Groundtrack and Correlation with Lunar Surface Features Authors: Golub, L.; Bjorkholm, P. J.; Gorenstein, P. Bibcode: 1973LPI.....4..302G Altcode: No abstract at ADS Title: Detection of Radon Emanation from the Lunar Regolith during Apollo 15 and 16 Authors: Bjorkholm, P.; Golub, L.; Gorenstein, P. Bibcode: 1973LPI.....4...78B Altcode: No abstract at ADS Title: Distribution of 222Rn and 210Po on the lunar surface as observed by the alpha particle spectrometer Authors: Bjorkholm, P. J.; Golub, L.; Gorenstein, P. Bibcode: 1973LPSC....4.2793B Altcode: 1973GeCAS...4.2793B No abstract at ADS Title: Spatial features and temporal variability in the emission of radon from the moon: An interpretation of results from the alpha particle spectrometer Authors: Gorenstein, P.; Golub, L.; Bjorkholm, P. J. Bibcode: 1973LPSC....4.2803G Altcode: 1973GeCAS...4.2803G No abstract at ADS Title: X-Ray Fluorescence Experiment Authors: Adler, I.; Trombka, J.; Gerard, J.; Lowman, P.; Schmadebeck, R.; Blodget, H.; Eller, E.; Yin, L.; Lamothe, R.; Osswald, G.; Gorenstein, P.; Bjorkholm, P.; Gursky, H.; Harris, B.; Golub, L.; Harnden, F. R., Jr. Bibcode: 1972NASSP.315..191A Altcode: No abstract at ADS