Author name code: kobelski ADS astronomy entries on 2022-09-14 author:"Kobelski, Adam" ------------------------------------------------------------------------ Title: Quiet Sun Center to Limb Variation of the Linear Polarization Observed by CLASP2 Across the Mg II h and k Lines Authors: Rachmeler, L. A.; Bueno, J. Trujillo; McKenzie, D. E.; Ishikawa, R.; Auchère, F.; Kobayashi, K.; Kano, R.; Okamoto, T. J.; Bethge, C. W.; Song, D.; Ballester, E. Alsina; Belluzzi, L.; Pino Alemán, T. del; Ramos, A. Asensio; Yoshida, M.; Shimizu, T.; Winebarger, A.; Kobelski, A. R.; Vigil, G. D.; Pontieu, B. De; Narukage, N.; Kubo, M.; Sakao, T.; Hara, H.; Suematsu, Y.; Štěpán, J.; Carlsson, M.; Leenaarts, J. Bibcode: 2022ApJ...936...67R Altcode: 2022arXiv220701788R The CLASP2 (Chromospheric LAyer Spectro-Polarimeter 2) sounding rocket mission was launched on 2019 April 11. CLASP2 measured the four Stokes parameters of the Mg II h and k spectral region around 2800 Å along a 200″ slit at three locations on the solar disk, achieving the first spatially and spectrally resolved observations of the solar polarization in this near-ultraviolet region. The focus of the work presented here is the center-to-limb variation of the linear polarization across these resonance lines, which is produced by the scattering of anisotropic radiation in the solar atmosphere. The linear polarization signals of the Mg II h and k lines are sensitive to the magnetic field from the low to the upper chromosphere through the Hanle and magneto-optical effects. We compare the observations to theoretical predictions from radiative transfer calculations in unmagnetized semiempirical models, arguing that magnetic fields and horizontal inhomogeneities are needed to explain the observed polarization signals and spatial variations. This comparison is an important step in both validating and refining our understanding of the physical origin of these polarization signatures, and also in paving the way toward future space telescopes for probing the magnetic fields of the solar upper atmosphere via ultraviolet spectropolarimetry. 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: A Publicly Available Multiobservatory Data Set of an Enhanced Network Patch from the Photosphere to the Corona Authors: Kobelski, Adam R.; Tarr, Lucas A.; Jaeggli, Sarah A.; Luber, Nicholas; Warren, Harry P.; Savage, Sabrina Bibcode: 2022ApJS..261...15K Altcode: 2022arXiv220501766K New instruments sensitive to chromospheric radiation at X-ray, UV, visible, IR, and submillimeter wavelengths have become available that significantly enhance our ability to understand the bidirectional flow of energy through the chromosphere. We describe the calibration, coalignment, initial results, and public release of a new data set combining a large number of these instruments to obtain multiwavelength photospheric, chromospheric, and coronal observations capable of improving our understanding of the connectivity between the photosphere and the corona via transient brightenings and wave signatures. The observations center on a bipolar region of enhanced-network magnetic flux near disk center on SOL2017-03-17T14:00-17:00. The comprehensive data set provides one of the most complete views to date of chromospheric activity related to small-scale brightenings in the corona and chromosphere. Our initial analysis shows a strong spatial correspondence between the areas of broadest width of the hydrogen-α spectral line and the hottest temperatures observed in Atacama Large Millimeter/submillimeter Array (ALMA) Band 3 radio data, with a linear coefficient of 6.12 × 10-5Å/K. The correspondence persists for the duration of cotemporal observations (≍60 m). Numerous transient brightenings were observed in multiple data series. We highlight a single, well-observed transient brightening in a set of thin filamentary features with a duration of 20 minutes. The timing of the peak intensity transitions from the cooler (ALMA, 7000 K) to the hotter (XRT, 3 MK) data series. Title: Radar observations and characterization of (436724) 2011 UW158 Authors: Naidu, Shantanu; Benner, Lance; Brozovic, Marina; Giorgini, Jon; Busch, Michael; Taylor, Patrick; Richardson, James; Ghigo, Frank; Kobelski, Adam; Ford, Linda Bibcode: 2019EPSC...13..737N Altcode: Near-Earth asteroid (436724) 2011 UW158 made a close approach to the Earth on 2015 July 19 at a distance of 0.016 au (6.4 lunar distances), which provided an outstanding opportunity for ground-based radar imaging. We observed it using the Goldstone X-band (8560 MHz, 3.5 cm) radar, the Green Bank Telescope (GBT), and Arecibo S-band (2380 MHz, 12.6 cm) radar, between July 13-26. The radar dataset allowed us to estimate the shape, spin state, and other physical properties of the object. Title: Frequency Agile Solar Radiotelescope Authors: Bastian, Tim; Bain, H.; Bradley, R.; Chen, B.; Dahlin, J.; DeLuca, E.; Drake, J.; Fleishman, G.; Gary, D.; Glesener, L.; Guo, Fan; Hallinan, G.; Hurford, G.; Kasper, J.; Ji, Hantao; Klimchuk, J.; Kobelski, A.; Krucker, S.; Kuroda, N.; Loncope, D.; Lonsdale, C.; McTiernan, J.; Nita, G.; Qiu, J.; Reeves, K.; Saint-Hilaire, P.; Schonfeld, S.; Shen, Chengcai; Tun, S.; Wertheimer, D.; White, S. Bibcode: 2019astro2020U..56B Altcode: We describe the science objectives and technical requirements for a re-scoped Frequency Agile Solar Radiotelescope (FASR). FASR fulfills a long term community need for a ground-based, solar-dedicated, radio telescope - a next-generation radioheliograph - designed to perform ultra-broadband imaging spectropolarimetry. Title: Transient dynamics and energy transfer from the photosphere to the low corona: initial results from a coordinated ALMA, DST, Hinode, IRIS, and SDO observation campaign Authors: Kobelski, Adam; Tarr, Lucas A.; Jaeggli, Sarah A.; Savage, Sabrina Bibcode: 2019AAS...23430702K Altcode: We present initial results from a coordinated observation campaign to study transient dynamics and energy transfer in the low solar atmosphere. The observations ran from approximately 2017-03-21 from 13UT to 19UT, and include data from Hinode, IRIS, DST, and ALMA. The target, a small, magnetically bipolar active area associated with a coronal bright point, was chosen for showing reasonable dynamics in the chromosphere (as dictated by AIA 304 data from the day prior), and being near disk center to better facilitate magnetic field measurement. The campaign was designed to capture the dynamics of the target with as rapid a timescale as possible for each instrument. Photospheric dynamics are available from broadband IBIS data and the HMI. New to this dataset, the chromospheric dynamics were observed in radio frequencies using ALMA (Band 3: 92-108GHz) at a 2s cadence. Additional chromospheric data are spectral H-α from the IBIS instrument at the DST, spectropolarimetic HeI 10830 from the FIRS instrument at the DST, and the medium linelist from IRIS; coronal data includes imaging from XRT and spectral data from EIS. In this first set of results, we discuss the frequency of transient brightenings observed in each set of imaging data and how the spatial distribution relates across each data channel and to the regions magnetic topology. Title: Radio Propagation Diagnostics of the Inner Heliosphere in the Era of the Parker Solar Probe Authors: Kobelski, Adam; Bastian, Timothy S.; Vourlidas, Angelos Bibcode: 2019AAS...23410706K Altcode: The solar wind offers and extraordinary laboratory for studying turbulence, turbulent dissipation, and heating. The Parker Solar Probe (PSP) was launched in August 2018 to study these and other important processes in the inner heliosphere. One type of observation that will complement those of PSP are radio propagation measurements of solar wind turbulence in the outer corona and the inner heliosphere. This type of observation can provide measurements of the angular broadening of distant spatially coherent background sources that transilluminate the foreground solar wind plasma. This well-known technique can be used to measure the spatial spectrum of electron density inhomogeneities in the solar wind on scales of 100s of meters to 10s of kilometers inside of 10-15 solar radii over a wide range of position angles.

Here we report the results of a pilot study of background sources using the Jansky Very Large Array (JVLA) in summer 2015. Unlike previous studies of this kind, the JVLA's much greater sensitivity allows fainter and more numerous sources to be used as probes of the foreground medium. We observed 11 background sources in 16 sessions at apparent radial distances of 2-7 solar radii. We confirm previous findings: that the spectrum is flatter than Kolmogorov and that is highly anisotropic. Unlike previous studies we find breaks into steeper spectra for some sources on short spatial scales, suggestive of a transition to dissipation.

Looking forward, we describe observations planned in August 2019 in support of the third PSP perihelion passage (35.7 solar radii). The VLA will be used to observe the corona and inner heliosphere along 70 pierce points <10 solar radii. These observations will not only provide global context about the state of the inner heliosphere at time of perihelion passage, they will also baseline key solar wind parameters that can be compared directly with PSP measurements. These include turbulence level, spectral index, degree of anisotropy, and the orientation of the magnetic field. The PSP measurements will, in turn, provide measurements that will validate key assumptions made in interpreting the radio data. Title: High Frequency Solar Observing at the Green Bank Observatory Authors: Kobelski, Adam Bibcode: 2019BAAS...51c.533K Altcode: 2019astro2020T.533K Here we discuss the utility of performing high frequency observations of the solar chromosphere with the 100 m Green Bank Telescope at 100 GHz. Title: Radio Observational Constraints on Turbulent Astrophysical Plasmas Authors: Bastian, Tim; Cordes, James; Kasper, Justin; Kobelski, Adam; Korreck, Kelly; Howes, Gregory; Salem, Chadi; Spangler, Steve; Vourlidas, Angelos Bibcode: 2019astro2020T.307B Altcode: 2019arXiv190405807B Using radio observations of background sources, scattering phenomena may be used to characterize the properties of foreground turbulent plasma. We discuss the potential of such techniques to explore turbulence in the solar wind and interstellar medium. The Next Generation VLA will be an ideal instrument to exploit these techniques. Title: Observations of the solar chromosphere with ALMA and comparison with theoretical models Authors: Brajsa, Roman; Sudar, Davor; Skokic, Ivica; Benz, Arnold O.; Kuhar, Matej; Kobelski, Adam; Wedemeyer, Sven; White, Stephen M.; Ludwig, Hans-G.; Temmer, Manuela; Saar, Steven H.; Selhorst, Caius L. Bibcode: 2018csss.confE..37B Altcode: 2018arXiv181207293B In this work we use solar observations with the ALMA radio telescope at the wavelength of 1.21 mm. The aim of the analysisis to improve understanding of the solar chromosphere, a dynamic layer in the solar atmosphere between the photosphere andcorona. The study has an observational and a modeling part. In the observational part full-disc solar images are analyzed.Based on a modied FAL atmospheric model, radiation models for various observed solar structures are developed. Finally, theobservational and modeling results are compared and discussed. Title: Probing the Inner Heliosphere Using Radio Diagnostic Techniques Authors: Bastian, Tim; Kobelski, Adam Bibcode: 2018shin.confE..38B Altcode: A variety of radio propagation techniques - angular and spectral broadening, scintillation, and Faraday rotation - can be used to probe regions in the corona and solar wind that are otherwise inaccessible to direct observation. We present some recent pilot observations made by the Jansky Very Large Array to illustrate their potential for deducing key properties of solar wind turbulence in the inner heliosphere. We discuss prospects for exploiting these techniques in a more systematic way in the era of the Parker Solar Probe and the Solar Obiter. Title: Searching for Supra Arcade Downflows in the Earth's Magnetotail and Dipolarization Fronts in Solar Flares Authors: Kobelski, Adam; Savage, Sabrina L.; Malaspina, David Bibcode: 2018tess.conf10207K Altcode: Pinpointing the location of a single reconnection event in the corona is difficult due to observational constraints, although features directly resulting from this rapid reconfiguration of the field lines can be observed beyond the reconnection site. One set of such features are outflows in the form of post-reconnection loops, which have been linked to observations of supra-arcade downflows (SADs). SADs appear as sunward-traveling, density-depleted regions above flare arcades that develop during long duration eruptions. The limitations of remote sensing methods inherently results in ambiguities regarding the interpretation of SAD formation. Of particular interest is how these features are related to post-reconnection retracting magnetic field lines.

In planetary magnetospheres, similar events to solar flares occur in the form of substorms, where reconnection in the anti-sunward tail of the magnetosphere causes field lines to retract toward the planet. Using data from the Time History of Events and Macroscopic Interactions during Substorms (THEMIS), we compare one particular aspect of substorms, dipolarization fronts, to SADs. Dipolarization fronts are observed as rapid but temporary changes in the magnetic field of the magnetotail plasma sheet into a more potential-like, dipolar shape. These dipolarization fronts are believed to be retracting post-reconnection field lines. We combine data sets to show that the while the densities and magnetic fields involved vary greatly between the regimes, the plasma βs and Alfvén speeds are similar. These similarities allow direct comparison between the retracting field lines and their accompanying wakes of rarified plasma observed with THEMIS around the Earth to the observed morphological density depletions visible with XRT and AIA on the Sun. These results are an important source of feedback for models of coronal current sheets. Title: First analysis of solar structures in 1.21 mm full-disc ALMA image of the Sun Authors: Brajša, R.; Sudar, D.; Benz, A. O.; Skokić, I.; Bárta, M.; De Pontieu, B.; Kim, S.; Kobelski, A.; Kuhar, M.; Shimojo, M.; Wedemeyer, S.; White, S.; Yagoubov, P.; Yan, Y. Bibcode: 2018A&A...613A..17B Altcode: 2017arXiv171106130B Context. Various solar features can be seen in emission or absorption on maps of the Sun in the millimetre and submillimetre wavelength range. The recently installed Atacama Large Millimetre/submillimetre Array (ALMA) is capable of observing the Sun in that wavelength range with an unprecedented spatial, temporal and spectral resolution. To interpret solar observations with ALMA, the first important step is to compare solar ALMA maps with simultaneous images of the Sun recorded in other spectral ranges.
Aims: The first aim of the present work is to identify different structures in the solar atmosphere seen in the optical, infrared, and EUV parts of the spectrum (quiet Sun, active regions, prominences on the disc, magnetic inversion lines, coronal holes and coronal bright points) in a full-disc solar ALMA image. The second aim is to measure the intensities (brightness temperatures) of those structures and to compare them with the corresponding quiet Sun level.
Methods: A full-disc solar image at 1.21 mm obtained on December 18, 2015, during a CSV-EOC campaign with ALMA is calibrated and compared with full-disc solar images from the same day in Hα line, in He I 1083 nm line core, and with various SDO images (AIA at 170 nm, 30.4 nm, 21.1 nm, 19.3 nm, and 17.1 nm and HMI magnetogram). The brightness temperatures of various structures are determined by averaging over corresponding regions of interest in the calibrated ALMA image.
Results: Positions of the quiet Sun, active regions, prominences on the disc, magnetic inversion lines, coronal holes and coronal bright points are identified in the ALMA image. At the wavelength of 1.21 mm, active regions appear as bright areas (but sunspots are dark), while prominences on the disc and coronal holes are not discernible from the quiet Sun background, despite having slightly less intensity than surrounding quiet Sun regions. Magnetic inversion lines appear as large, elongated dark structures and coronal bright points correspond to ALMA bright points.
Conclusions: These observational results are in general agreement with sparse earlier measurements at similar wavelengths. The identification of coronal bright points represents the most important new result. By comparing ALMA and other maps, it was found that the ALMA image was oriented properly and that the procedure of overlaying the ALMA image with other images is accurate at the 5 arcsec level. The potential of ALMA for physics of the solar chromosphere is emphasised. Title: Exploring the Sun with ALMA Authors: Bastian, T. S.; Bárta, M.; Brajša, R.; Chen, B.; Pontieu, B. D.; Gary, D. E.; Fleishman, G. D.; Hales, A. S.; Iwai, K.; Hudson, H.; Kim, S.; Kobelski, A.; Loukitcheva, M.; Shimojo, M.; Skokić, I.; Wedemeyer, S.; White, S. M.; Yan, Y. Bibcode: 2018Msngr.171...25B Altcode: The Atacama Large Millimeter/submillimeter Array (ALMA) Observatory opens a new window onto the Universe. The ability to perform continuum imaging and spectroscopy of astrophysical phenomena at millimetre and submillimetre wavelengths with unprecedented sensitivity opens up new avenues for the study of cosmology and the evolution of galaxies, the formation of stars and planets, and astrochemistry. ALMA also allows fundamentally new observations to be made of objects much closer to home, including the Sun. The Sun has long served as a touchstone for our understanding of astrophysical processes, from the nature of stellar interiors, to magnetic dynamos, non-radiative heating, stellar mass loss, and energetic phenomena such as solar flares. ALMA offers new insights into all of these processes. Title: A comparison of solar ALMA observations and model based predictions of the brightness temperature Authors: Brajša, R.; Kuhar, M.; Benz, A. O.; Skokić, I.; Sudar, D.; Wedemeyer, S.; Báarta, M.; De Pontieu, B.; Kim, S.; Kobelski, A.; Shimojo, M.; White, S.; Yagoubov, P.; Yan, Y.; Ludwig, H. G.; Temmer, M.; Saar, S. H.; Selhorst, C. L.; Beuc, R. Bibcode: 2018CEAB...42....1B Altcode: The new facility Atacama Large Millimeter/submillimeter Array (ALMA) is capable of observing the Sun in the wavelength range from 0.3 mm to 10 mm with an unprecedented spatial, temporal and spectral resolution. The first aim of the present work is to identify different structures in the solar atmosphere (quiet Sun, active regions, filaments on the disc, and coronal holes) in a full disc solar ALMA image at 1.21 mm obtained on December 18, 2015 during a CSV-EOC campaign. It is compared with full disc solar images from the same day in the Hα line (Cerro Tololo Observatory, NISP), and at three EUV wavelengths (30.4 nm, 21.1 nm, 17.1 nm; a composite SDO image). Positions of the quiet Sun areas, active regions, filaments on the disc, and coronal holes are identified in the ALMA image. To interpret solar observations with ALMA it is important to compare the measured and calculated intensities of various solar structures. So, the second aim of this work is to calculate the intensity (brightness temperature) for those structures (quiet Sun, active regions, filaments on the disc, and coronal holes) for a broad wavelength range (from 0.3 mm to 10 mm), closely related to that of the ALMA, and to compare the results with available ALMA observations. Thermal bremsstrahlung is the dominant radiation mechanism for explanation of the observed phenomena. A procedure for calculating the brightness temperature for a given wavelength and model atmosphere, which integrates the radiative transfer equation for thermal bremsstrahlung, is used. At the wavelength of 1.21 mm active regions appear as bright areas, while filaments on the disc and coronal holes are not discernible from the quiet Sun background. The models generally agree with the observed results: Active regions are bright primarily due to higher densities, filaments can appear bright, dark or not at all and coronal holes cannot be easily identified. Title: Supra Arcade Downflows in the Earth's Magnetotail Authors: Kobelski, A.; Savage, S. L.; Malaspina, D. Bibcode: 2017AGUFMSH41A2752K Altcode: Pinpointing the location of a single reconnection event in the corona is difficult due to observational constraints, although features directly resulting from this rapid reconfiguration of the field lines can be observed beyond the reconnection site. One set of such features are outflows in the form of post-reconnection loops, which have been linked to observations of supra-arcade downflows (SADs). SADs appear as sunward-traveling, density-depleted regions above flare arcades that develop during long duration eruptions. The limitations of remote sensing methods inherently results in ambiguities regarding the interpretation of SAD formation. Of particular interest is how these features are related to post-reconnection retracting magnetic field lines. In planetary magnetospheres, similar events to solar flares occur in the form of substorms, where reconnection in the anti-sunward tail of the magnetosphere causes field lines to retract toward the planet. Using data from the Time History of Events and Macroscopic Interactions during Substorms (THEMIS), we compare one particular aspect of substorms, dipolarization fronts, to SADs. Dipolarization fronts are observed as rapid but temporary changes in the magnetic field of the magnetotail plasma sheet into a more potential-like dipolar shape. These dipolarization fronts are believed to be retracting post-reconnection field lines. We combine data sets to show that the while the densities and magnetic fields involved vary greatly between the regimes, the plasma βs and Alfvén speeds are similar. These similarities allow direct comparison between the retracting field lines and their accompanying wakes of rarified plasma observed with THEMIS around the Earth to the observed morphological density depletions visible with XRT and AIA on the Sun. These results are an important source of feedback for models of coronal current sheets. Title: Large Scale Coordination of Small Scale Structures Authors: Kobelski, Adam; Tarr, Lucas A.; Jaeggli, Sarah A.; Savage, Sabrina Bibcode: 2017SPD....4820005K Altcode: Transient brightenings are ubiquitous features of the solar atmosphere across many length and energy scales, the most energetic of which manifest as large-class solar flares. Often, transient brightenings originate in regions of strong magnetic activity and create strong observable enhancements across wavelengths from X-ray to radio, with notable dynamics on timescales of seconds to hours.The coronal aspects of these brightenings have often been studied by way of EUV and X-ray imaging and spectra. These events are likely driven by photospheric activity (such as flux emergence) with the coronal brightenings originating largely from chromospheric ablation (evaporation). Until recently, chromospheric and transition region observations of these events have been limited. However, new observational capabilities have become available which significantly enhance our ability to understand the bi-directional flow of energy through the chromosphere between the photosphere and the corona.We have recently obtained a unique data set with which to study this flow of energy through the chromosphere via the Interface Region Imaging Spectrograph (IRIS), Hinode EUV Imaging Spectrometer (EIS), Hinode X-Ray Telescope (XRT), Hinode Solar Optical Telescope (SOT), Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA), SDO Helioseismic and Magnetic Imager (HMI), Nuclear Spectroscopic Telescope Array (NuStar), Atacama Large Millimeter Array (ALMA), and Interferometric BIdimensional Spectropolarimeter (IBIS) at the Dunn Solar Telescope (DST). This data set targets a small active area near disk center which was tracked simultaneously for approximately four hours. Within this region, many transient brightenings detected through multiple layers of the solar atmosphere. In this study, we combine the imaging data and use the spectra from EIS and IRIS to track flows from the photosphere (HMI, SOT) through the chromosphere and transition region (AIA, IBIS, IRIS, ALMA) into the corona (EIS, XRT, AIA). Title: High-cadence Hinode/XRT observations for studying coronal events with very short timescales Authors: McKenzie, David Eugene; Kobelski, Adam; Savage, Sabrina Bibcode: 2017SPD....4830406M Altcode: The Hinode X-Ray Telescope’s capability for high time cadence observations makes it an excellent tool for probing highly variable conditions in the corona, including wave-like activity, dynamic plasma motions, and short-duration transient events. XRT is capable of producing images at cadences faster than one image per 10 seconds, which is comparable to the energy release timescales, and/or ionization evolution timescales, predicted by a range of models of coronal activity. In the present work, we demonstrate XRT’s high-cadence capability through observations of active region AR 10923 (2006 November), with cadences of 6-20 seconds. The image sequences, made sequentially with multiple analysis filters, reveal many transient brightenings (i.e., microflares), for which we derive heating and cooling timescales. We also forward model the observed light curves to estimate the temperature, density, filling factors, and lengths of the observed loops. These estimates allow us to prioritize different heating mechanisms, and to better understand the unresolved structures within the observations. This study provides a test of capabilities, which have still not yet been fully utilized by the ten-year-old Hinode X-Ray Telescope, and thus provides a starting point for future investigations of short-timescale/high-frequency variations in coronal X-ray intensity. Title: Reconnection Outflows in the Extended Corona and Magnetotail Authors: Savage, Sabrina; Kobelski, Adam Bibcode: 2017SPD....4830303S Altcode: Observational signatures of reconnection have been studied extensively in the lower corona for decades, successfully providing insight into energy release mechanisms in the region above post-flare arcade loops and below 1.5 solar radii. During large eruptive events, however, energy release continues to occur well beyond the presence of reconnection signatures at these low heights. Supra-arcade downflows (SADs) and downflowing loops (SADLs) are particularly useful measures of continual reconnection in the corona as they may indicate the presence and path of retracting post-reconnection loops. SADs and SADLs have been observed for days beyond the passage of corona mass ejections through the SOHO/LASCO field of view and for nearly a week after an eruption on 14 October 2014. The association of these features with magnetic reconnection increases the significance of understanding their genesis. SADs have been interpreted as wakes behind newly reconnected and outflowing loops (SADLs). Models have shown the plausibility of this interpretation, though this interpretation has not yet been fully accepted. We will present a preliminary study of complementary observations of magnetic reconnection detected via in situ instruments in the magnetosphere. These observations, provided by five THEMIS spacecraft, reveal similar structures and conditions to those related to SADs. We compare data from multiple SADs and dipolarization fronts to test the similarity between these plasma regimes, strongly favoring the interpretation of SADs as instabilities trailing retracting loops. We will also use these observations to strengthen the case for the development of an EUV wide-field coronal imager. Title: Observational Signatures of Magnetic Reconnection in the Extended Corona Authors: Savage, Sabrina L.; West, Matthew; Seaton, Daniel; Kobelski, Adam Bibcode: 2017shin.confE..40S Altcode: Observational signatures of reconnection have been studied extensively in the lower corona for decades, successfully providing insight into energy release mechanisms in the region above post-flare arcade loops and below 1.5 solar radii. During large eruptive events, however, energy release continues to occur well beyond the presence of reconnection signatures at these low heights. Supra-arcade downflows (SADs) and downflowing loops (SADLs) are particularly useful measures of continual reconnection in the corona as they may indicate the presence and path of retracting post-reconnection loops. SADs and SADLs have been faintly observed up to 18 hours beyond the passage of corona mass ejections through the SOHO/LASCO field of view, but a recent event from 2014 October 14 associated with giant arches provides very clear observations of these downflows for days after the initial eruption. We report on this unique event and compare these findings with observational signatures of magnetic reconnection in the extended corona for more typical eruptions. Title: Observing the Sun with the Atacama Large Millimeter/submillimeter Array (ALMA): High-Resolution Interferometric Imaging Authors: Shimojo, M.; Bastian, T. S.; Hales, A. S.; White, S. M.; Iwai, K.; Hills, R. E.; Hirota, A.; Phillips, N. M.; Sawada, T.; Yagoubov, P.; Siringo, G.; Asayama, S.; Sugimoto, M.; Brajša, R.; Skokić, I.; Bárta, M.; Kim, S.; de Gregorio-Monsalvo, I.; Corder, S. A.; Hudson, H. S.; Wedemeyer, S.; Gary, D. E.; De Pontieu, B.; Loukitcheva, M.; Fleishman, G. D.; Chen, B.; Kobelski, A.; Yan, Y. Bibcode: 2017SoPh..292...87S Altcode: 2017arXiv170403236S Observations of the Sun at millimeter and submillimeter wavelengths offer a unique probe into the structure, dynamics, and heating of the chromosphere; the structure of sunspots; the formation and eruption of prominences and filaments; and energetic phenomena such as jets and flares. High-resolution observations of the Sun at millimeter and submillimeter wavelengths are challenging due to the intense, extended, low-contrast, and dynamic nature of emission from the quiet Sun, and the extremely intense and variable nature of emissions associated with energetic phenomena. The Atacama Large Millimeter/submillimeter Array (ALMA) was designed with solar observations in mind. The requirements for solar observations are significantly different from observations of sidereal sources and special measures are necessary to successfully carry out this type of observations. We describe the commissioning efforts that enable the use of two frequency bands, the 3-mm band (Band 3) and the 1.25-mm band (Band 6), for continuum interferometric-imaging observations of the Sun with ALMA. Examples of high-resolution synthesized images obtained using the newly commissioned modes during the solar-commissioning campaign held in December 2015 are presented. Although only 30 of the eventual 66 ALMA antennas were used for the campaign, the solar images synthesized from the ALMA commissioning data reveal new features of the solar atmosphere that demonstrate the potential power of ALMA solar observations. The ongoing expansion of ALMA and solar-commissioning efforts will continue to enable new and unique solar observing capabilities. Title: Observing the Sun with the Atacama Large Millimeter/submillimeter Array (ALMA): Fast-Scan Single-Dish Mapping Authors: White, S. M.; Iwai, K.; Phillips, N. M.; Hills, R. E.; Hirota, A.; Yagoubov, P.; Siringo, G.; Shimojo, M.; Bastian, T. S.; Hales, A. S.; Sawada, T.; Asayama, S.; Sugimoto, M.; Marson, R. G.; Kawasaki, W.; Muller, E.; Nakazato, T.; Sugimoto, K.; Brajša, R.; Skokić, I.; Bárta, M.; Kim, S.; Remijan, A. J.; de Gregorio, I.; Corder, S. A.; Hudson, H. S.; Loukitcheva, M.; Chen, B.; De Pontieu, B.; Fleishmann, G. D.; Gary, D. E.; Kobelski, A.; Wedemeyer, S.; Yan, Y. Bibcode: 2017SoPh..292...88W Altcode: 2017arXiv170504766W The Atacama Large Millimeter/submillimeter Array (ALMA) radio telescope has commenced science observations of the Sun starting in late 2016. Since the Sun is much larger than the field of view of individual ALMA dishes, the ALMA interferometer is unable to measure the background level of solar emission when observing the solar disk. The absolute temperature scale is a critical measurement for much of ALMA solar science, including the understanding of energy transfer through the solar atmosphere, the properties of prominences, and the study of shock heating in the chromosphere. In order to provide an absolute temperature scale, ALMA solar observing will take advantage of the remarkable fast-scanning capabilities of the ALMA 12 m dishes to make single-dish maps of the full Sun. This article reports on the results of an extensive commissioning effort to optimize the mapping procedure, and it describes the nature of the resulting data. Amplitude calibration is discussed in detail: a path that uses the two loads in the ALMA calibration system as well as sky measurements is described and applied to commissioning data. Inspection of a large number of single-dish datasets shows significant variation in the resulting temperatures, and based on the temperature distributions, we derive quiet-Sun values at disk center of 7300 K at λ =3 mm and 5900 K at λ =1.3 mm. These values have statistical uncertainties of about 100 K, but systematic uncertainties in the temperature scale that may be significantly larger. Example images are presented from two periods with very different levels of solar activity. At a resolution of about 25″, the 1.3 mm wavelength images show temperatures on the disk that vary over about a 2000 K range. Active regions and plages are among the hotter features, while a large sunspot umbra shows up as a depression, and filament channels are relatively cool. Prominences above the solar limb are a common feature of the single-dish images. Title: Supra Arcade Downflows in the Corona Informed by Magnetospheric Dipolarization Fronts with THEMIS Authors: Kobelski, A.; Savage, S. L.; Malaspina, D. Bibcode: 2016AGUFMSM33A2500K Altcode: Magnetic reconnection rapidly reconfigures the magnetic field of the corona, accelerating plasma through the site of reconnection. Ambiguities (such as line-of-sight effects) due to the nature of the remote sensing instruments available to study the corona complicate the interpretation of observations of the inflowing and outflowing plasma in reconnecting regions. In particular, the interpretation of sunward moving density depletions above flare arcades (known as Supra Arcade Downflows — SADs) is still debated. SADs have been interpreted as wakes behind newly reconnected and outflowing loops (Supra Arcade Downflowing Loops — SADLs). Hinode/XRT and SDO/AIA have provided a wealth of observations for SADs and helped inform our current understanding of these structures. Models have shown the plausibility of the interpretation of SADs as wakes behind loops, though this interpretation has not yet been fully accepted. We present here observations of newly reconnected outflowing loops observed via in situ instruments in the magnetosphere. These observations, provided by up to five THEMIS spacecraft, show that around retracting loops (dipolarization fronts in this context), similar temperature and density structures as seen in SADs. We compare data from multiple SADs and dipolarization fronts to show that the observational signatures implied in the corona can be directly observed in similar plasma regimes in the magnetosphere, strongly favoring the interpretation of SADs as wakes behind retracting loops. Title: Observational Signatures of Magnetic Reconnection in the Corona Authors: Savage, S. L.; West, M. J.; Seaton, D. B.; Kobelski, A. Bibcode: 2016AGUFMSM33A2501S Altcode: Observational signatures of reconnection have been studied extensively in the lower corona for decades, successfully providing insight into energy release mechanisms in the region above post-flare arcade loops and below 1.5 solar radii. During large eruptive events, however, energy release continues to occur well beyond the presence of reconnection signatures at these low heights. Supra-arcade downflows (SADs) and downflowing loops (SADLs) are particularly useful measures of continual reconnection in the corona as they may indicate the presence and path of retracting post-reconnection loops. SADs and SADLs have been faintly observed up to 18 hours beyond the passage of corona mass ejections through the SOHO/LASCO field of view, but a recent event from 2014 October 14 associated with giant arches provides very clear observations of these downflows for days after the initial eruption. We report on this unique event and compare these findings with observational signatures of magnetic reconnection in the extended corona for more typical eruptions. Title: Observational Signatures of Magnetic Reconnection in the Extended Corona Authors: Savage, Sabrina; West, Matthew; Seaton, Daniel B.; Kobelski, Adam Bibcode: 2016SPD....4730703S Altcode: Observational signatures of reconnection have been studied extensively in the lower corona for decades, successfully providing insight into energy release mechanisms in the region above post-flare arcade loops and below 1.5 solar radii. During large eruptive events, however, energy release continues to occur well beyond the presence of reconnection signatures at these low heights. Supra-arcade downflows (SADs) and downflowing loops (SADLs) are particularly useful measures of continual reconnection in the corona as they may indicate the presence and path of retracting post-reconnection loops. SADs and SADLs have been faintly observed up to 18 hours beyond the passage of corona mass ejections through the SOHO/LASCO field of view, but a recent event from 2014 October 14 associated with giant arches provides very clear observations of these downflows for days after the initial eruption. We report on this unique event and compare these findings with observational signatures of magnetic reconnection in the extended corona for more typical eruptions. Title: Solar Observations with the Atacama Large Millimeter/submillimeter Array (ALMA) Authors: Kobelski, A.; Bastian, T. S.; Bárta, M.; Brajša, R.; Chen, B.; De Pontieu, B.; Fleishman, G.; Gary, D.; Hales, A.; Hills, R.; Hudson, H.; Hurford, G.; Loukitcheva, M.; Iwai, K.; Krucker, S.; Shimojo, M.; Skokić, I.; Wedemeyer, S.; White, S.; Yan, Y.; ALMA Solar Development Team Bibcode: 2016ASPC..504..327K Altcode: The Atacama Large Millimeter/Submillimeter Array (ALMA) is a joint North American, European, and East Asian project that opens the mm-sub mm wavelength part of the electromagnetic spectrum for general astrophysical exploration, providing high-resolution imaging in frequency bands currently ranging from 84 GHz to 950 GHz (300 microns to 3 mm). It is located in the Atacama desert in northern Chile at an elevation of 5000 m. Despite being a general purpose instrument, provisions have been made to enable solar observations with ALMA. Radiation emitted at ALMA wavelengths originates mostly from the chromosphere, which plays an important role in the transport of matter and energy, and the in heating the outer layers of the solar atmosphere. Despite decades of research, the solar chromosphere remains a significant challenge: both to observe, owing to the complicated formation mechanisms of currently available diagnostics; and to understand, as a result of the complex nature of the structure and dynamics of the chromosphere. ALMA has the potential to change the scene substantially as it serves as a nearly linear thermometer at high spatial and temporal resolution, enabling us to study the complex interaction of magnetic fields and shock waves and yet-to-be-discovered dynamical processes. Moreover, ALMA will play an important role in the study of energetic emissions associated with solar flares at sub-THz frequencies. Title: Measuring the Solar Magnetic Field with STEREO A Radio Transmissions: Faraday Rotation Observations using the 100m Green Bank Telescope Authors: Kobelski, A.; Jensen, E.; Wexler, D.; Heiles, C.; Kepley, A.; Kuiper, T.; Bisi, M. Bibcode: 2016ASPC..504...99K Altcode: The STEREO mission spacecraft recently passed through superior conjunction, providing an opportunity to probe the solar corona using radio transmissions. Strong magnetic field and dense plasma environment induce Faraday rotation of the linearly polarized fraction of the spacecraft radio carrier signal. Variations in the Faraday rotation signify changes in magnetic field components and plasma parameters, and thus can be used to gain understanding processes of the quiescent sun as well as active outbursts including coronal mass ejections. Our 2015 observing campaign resulted in a series of measurements over several months with the 100m Green Bank Telescope (GBT) to investigate the coronal Faraday rotation at various radial distances. These observations reveal notable fluctuations in the Faraday rotation of the signal in the deep corona, and should yield unique insights into coronal magnetohydrodynamics down to a 1.5 solar radius line-of-sight solar elongation. Title: Probing Solar Wind Turbulence with the Jansky Very Large Array Authors: Kobelski, A.; Bastian, T. S.; Betti, S. Bibcode: 2016ASPC..504...97K Altcode: The solar wind offers an extraordinary laboratory for studying MHD turbulence, turbulent dissipation, and heating. Radio propagation phenomena can be exploited as probes of the solar wind in regions that are generally inaccessible to in situ spacecraft measurements. Here, we have undertaken a study with the Jansky Very Large Array (VLA) to observe point-like sources drawn from the JVAS catalog, and 3 VLA calibrator sources, to trans-illuminate the outer corona/inner solar wind. In doing so, we will exploit angular broadening and refractive scintillation to deduce properties of the solar wind along ≍23 lines of sight within 7 solar radii of the Sun and a wide range of position angles. By fitting the complex visibilities using well-known techniques we can deduce or constrain a number of key parameters. In particular, we fit the visibilities to a function of the known source flux, displacement of the source due to refraction, source broadening due to an elliptical structure function, spectral slope of the turbulence, and the coherence scale. Of particular interest is α, the spectral slope of the turbulence which we probe at both small (km to 10s of km) and large (thousands of km) scales. This will help us determine the presence and evolution of an inner scale, measure the degree of anisotropy, and constrain the topology of the global coronal magnetic field. The inner scale is of particular interest for constraining current theories of turbulence dissipation and heating. Initial analysis show the visibilities vary notably on timescales of individual integrations (2 seconds) and that the source is not uniformly broadened. All sources appear to preferentially broaden perpendicular to the magnetic field, consistent with theories of kinetic Alfvén waves. This type of observation will also help to interpret data from the upcoming Solar Probe Plus and Solar Orbiter missions. A full set of results and analysis is forthcoming. More details on previous results can be found in Bastian (1999), which used the previous generation VLA. Title: High-Resolution Bistatic Radar Imaging of Near-Earth Asteroids in 2015 using New Capabilities of Goldstone and Green Bank Telescopes Authors: Naidu, S.; Benner, L.; Brozovic, M.; Giorgini, J. D.; Jao, J. S.; Lee, C. G.; Busch, M.; Ghigo, F. D.; Ford, A.; Kobelski, A.; Marshall, S. Bibcode: 2015AGUFM.P53G..07N Altcode: We present new results from bistatic Goldstone to Green Bank Telescope (GBT) high-resolution radar imaging of near-Earth asteroids (NEAs). Previously, most radar observations used either the 305-m Arecibo radar or the 70-m DSS-14 radar at Goldstone. Following the installation of new data-taking equipment at the GBT in late 2014, the number of bistatic Goldstone/GBT observations has increased substantially. Receiving Goldstone radar echoes at the 100-m GBT improves the signal-to-noise ratios (SNRs) two- to three-fold relative to monostatic reception at DSS-14. The higher SNRs allow us to obtain higher resolution images than is possible with DSS-14 both transmitting and receiving. Thus far in 2015, we have used the GBT receiver in combination with the 450 kW DSS-14 antenna and a new low-power 80kW transmitter on the 34-m DSS-13 antenna at the Goldstone complex to image five and two NEAs respectively. Asteroids 2005 YQ96, 2004 BL86, and 1994 AW1 are binary systems. 2011 UW158 has a spin period of 36 minutes that is unusually fast among asteroids its size (~500 m). 1999 JD6 is a deeply bifurcated double-lobed object. 2015 HM10 is an elongated 80 m asteroid with a spin period of 22 minutes. Our best images of these objects resolve the surface with resolutions of 3.75 m and reveal numerous features. Such images are useful to estimate the 3D shape, spin state, and other physical and dynamical properties of the objects. This knowledge is of particular interest for spacecraft mission planning, impact threat assessment, and resource utilization. Over the long term, such observations will help answer fundamental questions regarding the origin of the diversity in asteroid morphologies, the importance of spin-up mechanisms and collisional influences, the interior structure and thermal properties of asteroids, and the variety of dynamical states. Title: Arecibo and Goldstone Radar Observations of the First-Recognized Binary Near-Earth Asteroid: (385186) 1994 AW1 Authors: Richardson, James E.; Taylor, Patrick A.; Rivera-Valentin, Edgard G.; Rodriguez-Ford, Linda A.; Benner, Lance A. M.; Naidu, Shantanu P.; Giorgini, Jon D.; Busch, Michael W.; Ghigo, Frank d.; Kobelski, Adam; Warner, Brian D.; Springmann, Alessondra; Marshall, Sean E.; Steckloff, Jordan K.; Sharkey, Benjamin Bibcode: 2015DPS....4730808R Altcode: Near-Earth asteroid (385186) 1994 AW1 was discovered at Palomar Observatory on 11 January 1994. Subsequent observations of this Amor family, Sa-class asteroid also identified it as the first candidate binary NEA, as indicated by multiple periodicities and possible mutual eclipsing/occulting events in the object’s lightcurve. On 15 July 2015 this asteroid made its closest approach to Earth since its discovery, coming within 0.065 AU (25 lunar distances), and prompting an extended observation campaign using both the JPL-Goldstone and Arecibo Observatory planetary radars. Goldstone observations covered the 14-19 July period of closest approach (0.066-0.070 AU) while the object remained below Arecibo’s observing horizon, with Arecibo picking up the observations between 20-30 July, as the object moved from 0.075 to 0.126 AU distance. At Goldstone, we were able to observe this object with range resolutions of 150 m using a Goldstone (DSS-14) to Green Bank Telescope (GBT) bistatic configuration, while at Arecibo, we conducted monostatic observations of 1994 AW1 using the 2380 MHz (12.6 cm) radar at resolutions of 30 m and 75 m.As a result, and twenty years after its discovery, these observations have confirmed the binary nature of 1994 AW1, showing the primary body to be about 600 m in diameter, the secondary body to be about half the diameter of the primary, with the two orbiting a common center of mass at a distance of about 1.2 km apart. Delay-Doppler image comparisons of the primary over the course of six nights (at 30 m resolution) confirm a lightcurve-derived rotation period of 2.518 +/- 0.002 hr, as >90% longitude coverage was achieved, revealing a slightly elongated, irregular surface morphology. Delay-Doppler images of the secondary reveal an elongated, irregular body which appears to be tidally locked, with its long axis pointed towards the primary as it orbits with a period of about 22 hr (also consistent with the lightcurve analysis). These very early results point to a total system mass of (1.6 +/- 0.5) x 10^11 kg and a crude, mean system density estimate of 1400 +/- 500 kg/m^3. Additional analysis and shape-modeling will be presented. Title: Potentially Hazardous Asteroid (85989) 1999 JD6: Radar, Infrared, and Lightcurve Observations and a Preliminary Shape Model Authors: Marshall, Sean E.; Howell, Ellen S.; Brozović, Marina; Taylor, Patrick A.; Campbell, Donald B.; Benner, Lance A. M.; Naidu, Shantanu P.; Giorgini, Jon D.; Jao, Joseph S.; Lee, Clement G.; Richardson, James E.; Rodriguez-Ford, Linda A.; Rivera-Valentin, Edgard G.; Ghigo, Frank; Kobelski, Adam; Busch, Michael W.; Pravec, Petr; Warner, Brian D.; Reddy, Vishnu; Hicks, Michael D.; Crowell, Jenna L.; Fernandez, Yanga R.; Vervack, Ronald J.; Nolan, Michael C.; Magri, Christopher; Sharkey, Benjamin; Bozek, Brandon Bibcode: 2015DPS....4720409M Altcode: We report observations of potentially hazardous asteroid (85989) 1999 JD6, which passed 0.048 AU from Earth (19 lunar distances) during its close approach on July 25, 2015. During eleven days between July 15 and August 4, 2015, we observed 1999 JD6 with the Goldstone Solar System Radar and with Arecibo Observatory's planetary radar, including bistatic reception of some Goldstone echoes at Green Bank. We obtained delay-Doppler radar images at a wide range of latitudes, with range resolutions varying from 7.5 to 150 meters per pixel, depending on the observing conditions. We acquired near-infrared spectra from the NASA InfraRed Telescope Facility (IRTF) on two nights in July 2015, at wavelengths from 0.75 to 5.0 microns, showing JD6's thermal emission. We also obtained optical lightcurves from Ondrejov Observatory (in 1999), Table Mountain Observatory (in 2000), and Palmer Divide Station (in 2015). Previous observers had suggested that 1999 JD6 was most likely an elongated object, based on its large lightcurve amplitude of 1.2 magnitudes (Szabo et al. 2001; Polishook and Brosch 2008; Warner 2014). The radar images reveal an elongated peanut-shaped object, with two lobes separated by a sharp concavity. JD6's maximum diameter is about two kilometers, and its larger lobe is approximately 50% longer than its smaller lobe. The larger lobe has a concavity on its end. We will present more details on the shape and rotation state of 1999 JD6, as well as its surface properties from optical and infrared data and thermal modeling. Title: Radar observations of near-Earth asteroid (436724) 2011 UW158 using the Arecibo, Goldstone, and Green Bank Telescopes Authors: Naidu, Shantanu P.; Benner, Lance A. M.; Brozovic, Marina; Giorgini, Jon D.; Jao, Joseph S.; Busch, Michael W.; Taylor, Patrick A.; Richardson, James E.; Rivera-Valentin, Edgard G.; Ford, Linda A.; Ghigo, Frank D.; Kobelski, Adam Bibcode: 2015DPS....4720408N Altcode: Near-Earth asteroid (436724) 2011 UW158 made a close approach to the Earth on 2015 July 19 at a distance of 0.016 au (6.4 lunar distances). We observed it between July 13-26 using the Arecibo S-band (2380 MHz, 12.5 cm) radar, the Goldstone X-band (8560 MHz, 3.5 cm) radar, and the Green Bank Telescope (GBT). Arecibo delay-Doppler observations achieved range resolutions as fine as 7.5 m. At the GBT, we used a newly installed radar backend to record the radar echoes, which improved signal-to-noise ratios (SNRs) two-fold relative to monostatic reception at the 70-m DSS-14 antenna at Goldstone. The higher SNRs allowed us to obtain images with range resolutions comparable to those at Arecibo that reveal the asteroid’s surface topography with great detail. The visible extents of the asteroid in the radar images suggest an elongated object with dimensions of about 600 x 300 m. The shape of the object is angular with a facet on one side that spans the entire length of the asteroid. Three parallel radar-bright features are visible when the asteroid is oriented broadside and may represent ridges. These features cause unusually large brightness variations in the echo as the asteroid rotates. There are other radar-bright regions that suggest small-scale (tens of meters) topography. Repetition of the leading edge profiles in the images indicates a spin period of ~37 minutes, which is consistent with the period that was previously reported using lightcurves (B. Gary, T. Lister, H. K. Moon, P. Pravec, and B. D. Warner, pers. comm.). This spin period is unusually fast among asteroids its size and suggests that the object has relatively high cohesive strength. 2011 UW158 has a relatively low delta-V for spacecraft missions and is on NASA’s Near-Earth Object Human Accessible Targets Study list. Title: The versatile GBT astronomical spectrometer (VEGAS): Current status and future plans Authors: Prestage, Richard M.; Bloss, Marty; Brandt, Joe; Chen, Hong; Creager, Ray; Demorest, Paul; Ford, John; Jones, Glenn; Kepley, Amanda; Kobelski, Adam; Marganian, Paul; Mello, Melinda; McMahon, David; McCullough, Randy; Ray, Jason; Roshi, D. Anish; Werthimer, Dan; Whitehead, Mark Bibcode: 2015ursi.confE...4P Altcode: The VEGAS multi-beam spectrometer (VEGAS) was built for the Green Bank Telescope (GBT) through a partnership between the National Radio Astronomy Observatory (NRAO) and the University of California at Berkeley. VEGAS is based on a Field Programmable Gate Array (FPGA) frontend and a heterogeneous computing backend comprised of Graphical Processing Units (GPUs) and CPUs. This system provides processing power to analyze up to 8 dual-polarization or 16 single-polarization inputs at bandwidths of up to 1.25 GHz per input. VEGAS was released for "shared-risk" observing in March 2014 and it became the default GBT spectral line backend in August 2014. Some of the early VEGAS observations include the Radio Ammonia Mid-Plane Survey, mapping of HCN/HCO+ in nearby galaxies, and a variety of radio-recombination line and pulsar projects. We will present some of the latest VEGAS science highlights. Title: Forward Modeling Transient Brightenings and Microflares around an Active Region Observed with Hi-C Authors: Kobelski, Adam R.; McKenzie, David E. Bibcode: 2014ApJ...794..119K Altcode: 2014arXiv1408.5440K Small-scale flare-like brightenings around active regions are among the smallest and most fundamental of energetic transient events in the corona, providing a testbed for models of heating and active region dynamics. In a previous study, we modeled a large collection of these microflares observed with Hinode/X-Ray Telescope (XRT) using EBTEL and found that they required multiple heating events, but could not distinguish between multiple heating events on a single strand, or multiple strands each experiencing a single heating event. We present here a similar study, but with extreme-ultraviolet data of Active Region 11520 from the High Resolution Coronal Imager (Hi-C) sounding rocket. Hi-C provides an order of magnitude improvement to the spatial resolution of XRT, and a cooler temperature sensitivity, which combine to provide significant improvements to our ability to detect and model microflare activity around active regions. We have found that at the spatial resolution of Hi-C (≈0.''3), the events occur much more frequently than expected (57 events detected, only 1 or 2 expected), and are most likely made from strands of the order of 100 km wide, each of which is impulsively heated with multiple heating events. These findings tend to support bursty reconnection as the cause of the energy release responsible for the brightenings. Title: Calibrating Data from the Hinode/X-Ray Telescope and Associated Uncertainties Authors: Kobelski, Adam R.; Saar, Steven H.; Weber, Mark A.; McKenzie, David E.; Reeves, Katharine K. Bibcode: 2014SoPh..289.2781K Altcode: 2013arXiv1312.4850K; 2014SoPh..tmp...27K The X-Ray Telescope (XRT) onboard the Hinode satellite, launched 23 September 2006 by the Japan Aerospace Exploration Agency (JAXA), is a joint mission of Japan, the United States, and the United Kingdom to study the solar corona. In particular, XRT was designed to study solar plasmas with temperatures between 1 and 10 MK with ≈ 1″ pixels (≈ 2″ resolution). Prior to analysis, the data product from this instrument must be properly calibrated and data values quantified to accurately assess the information contained within. We present here the standard methods of calibration for these data. The calibration was performed on an empirical basis that uses the least complicated correction that accurately describes the data while suppressing spurious features. By analyzing the uncertainties remaining in the data after calibration, we conclude that the procedure is successful, because the remaining uncertainty after calibration is dominated by photon noise. This calibration software is available in the SolarSoft software library. Title: The Heating of Active Regions Using Active Region Transient Brightenings Observed with XRT and Hi-C Authors: Kobelski, Adam; McKenzie, David Eugene Bibcode: 2014AAS...22431201K Altcode: Active region transient brightentings (ARTBs) are among the smallest and most fundamental of energetic transient events in the corona; as such, they provide a testbed for models of heating and active region dynamics. We have modeled a large collection of ARTBs observed with Hinode/XRT and with Hi-C as both (a) multi-stranded loops and (b) monolithic loops which experience multiple heating events, to explore the energetic ramifications and characteristics in active region dynamics. Even for these small, short-lived transients, our modeling indicates that multiple heating events are required for each ARTB. We compare the quality of model fits for two different temporal envelopes of the heating function, and discuss whether the results more strongly favor nanoflare or wave-absorption heating. Title: Modeling Active Region Transient Brightenings Observed with X-Ray Telescope as Multi-stranded Loops Authors: Kobelski, Adam R.; McKenzie, David E.; Donachie, Martin Bibcode: 2014ApJ...786...82K Altcode: 2014arXiv1403.7834K Strong evidence exists that coronal loops as observed in extreme ultraviolet and soft X-rays may not be monolithic isotropic structures, but can often be more accurately modeled as bundles of independent strands. Modeling the observed active region transient brightenings (ARTBs) within this framework allows for the exploration of the energetic ramifications and characteristics of these stratified structures. Here we present a simple method of detecting and modeling ARTBs observed with the Hinode X-Ray Telescope (XRT) as groups of zero-dimensional strands, which allows us to probe parameter space to better understand the spatial and temporal dependence of strand heating in impulsively heated loops. This partially automated method can be used to analyze a large number of observations to gain a statistical insight into the parameters of coronal structures, including the number of heating events required in a given model to fit the observations. In this article, we present the methodology and demonstrate its use in detecting and modeling ARTBs in a sample data set from Hinode/XRT. These initial results show that, in general, multiple heating events are necessary to reproduce observed ARTBs, but the spatial dependence of these heating events cannot yet be established. Title: Empirical studies on the initiation of impulsive heating in coronal loops Authors: Kobelski, Adam Robert Bibcode: 2014PhDT........78K Altcode: 2014PhDT.......546K The heating of the solar corona is an important topic both for scientists and modern society. One of the most fundamental of structures in the corona are bundles of plasma confined to the magnetic field, loops. Here we perform empirical studies to better understand the mechanisms responsible for heating loops. We observe loops in X-rays with XRT and model the observations as bundles of independent strands, showing that the mechanisms instigating the heating of loops is likely impulsive, yet requires multiple heating events to match observations. We also observe and model very small loops with Hi-C, exploiting the high resolution to show that the frequency with which small loops are heated is larger than expected. This study also puts constraints on the size of the heating events. We also perform a study on the initiation of magnetic reconnection between neighboring active regions, in hopes of understanding how magnetic fields interact, evolve and heat coronal loops. We close with a discussion on calibrating the data from a solar X-ray telescope and interpret the uncertainties within. Title: Fixing the Leak: Empirical Corrections for the Small Light Leak in Hinode XRT Authors: Saar, Steven H.; DeLuca, E. E.; McCauley, P.; Kobelski, A. Bibcode: 2013SPD....44...93S Altcode: On May 9, 2012, the the straylight level of XRT on Hinode suddenly increased, consistent with the appearance of a pinhole in the entrance filter (possibly a micrometeorite breach). The effect of this event is most noticeable in the optical G band data, which shows an average light excess of ~30%. However, data in several of the X-ray filters is also affected, due to low sensitivity "tails" of their filter responses into the visible. Observations taken with the G band filter but with the visible light shutter (VLS) closed show a weak, slightly shifted, out-of-focus image, revealing the leaked light. The intensity of the leak depends on telescope pointing, dropping strongly for images taken off-disk. By monitoring light levels in the corners of full-Sun Ti-poly filter images, we determine the approximate time of the event: ~13:30 UT. We use pairs of images taken just-before and after the filter breach to directly measure the leakage in two affected X-ray filters. We then develop a model using a scaled, shifted, and smoothed versions of the VLS closed images to remove the contamination. We estimate the uncertainties involved in our proposed correction procedure. This research was supported under NASA contract NNM07AB07C for Hinode XRT. Title: Modeling Active Region Transient Brightenings Observed with XRT as Multistranded Loops Authors: Kobelski, Adam; McKenzie, D. E. Bibcode: 2013SPD....44...77K Altcode: Strong evidence exists that coronal loops as observed in EUV and soft X-rays are not monolithic isotropic structures, but are more accurately modeled as bundles of independent strands. Modeling the observed active region transient brightenings (ARTBs) within this framework allows exploration of the energetic ramifications and characteristics of these stratified structures. Here we present a simple method of detecting and modeling ARTBs observed with the Hinode X-Ray Telescope (XRT) as groups of simple 0-dimensional strands. We probe parameter space to understand better the spatial and temporal dependence of strand heating in impulsively heated loops. We present results from using this partially automated method to analyze observations and gain a statistical insight into the heating of these structures. Title: Inferring Nonthermal Particle Characteristics from Thermal Emission Signatures Authors: Kobelski, A. R.; McKenzie, D. E.; Winter, H. D. Bibcode: 2012ASPC..454..333K Altcode: Much work has been done in characterizing the nonthermal particle beams found in flares. Most of this work has concentrated on the interpretation of hard X-ray (HXR) emission. While HXR emission does have a direct connection to the nonthermal particle beam, there are other emission mechanisms that can also provide insight into the nature of the nonthermal beam. In the impulsive phase of solar flares the primary source of plasma heating is collisions between the nonthermal particles and the ambient, thermal plasma in the flare loop. The properties of the nonthermal particle beam directly affect the heating of the thermal plasma. Thus the thermal emission (e.g., soft X-rays) can also yield clues to the properties of the nonthermal beam. Recent flare modeling in the dissertation of Winter (2009) makes specific predictions about the behavior of the soft X-ray (SXR) emission from the flaring loop, depending on the properties of the nonthermal particle beam. As an initial test of the applicability of these predictions to real flares, we have undertaken a comparison to HXR and SXR observations from the Yohkoh mission. We present preliminary results from the analysis of Yohkoh-observed solar flares, which show consistent temporal profiles in the apex to footpoint ratio. Title: Elemental Abundances as a New Source of Uncertainty of the Hinode/XRT Filter-ratio T and EM Analysis Authors: Takeda, A.; Kobelski, A.; McKenzie, D. E.; Yoshimura, K. Bibcode: 2012ASPC..456..133T Altcode: We calculated the Hinode/XRT temperature response functions with different assumptions of elemental abundances. The enhancement of the low FIP elements significantly affects the amplitude of the XRT response curves. This yields a significant difference in the emission measures calculated from the filter ratio method, while the effect on derived temperatures is relatively small. Title: Photometric Uncertainties within Hinode XRT Authors: Kobelski, Adam; Saar, S. H.; Weber, M. A.; McKenzie, D. E.; Reeves, K. K. Bibcode: 2012AAS...22020126K Altcode: We have developed estimates of the systematic uncertainties for the X-Ray Telescope (XRT) on Hinode. These estimates are included as optional returns from the standard XRT data reduction software, xrt_prep.pro. Included in these software estimates are uncertainties from instrument vignetting, dark current subtraction, split bias leveling, Fourier filtering and JPEG compression. Sources of uncertainty that rely heavily on models of plasma radiation or assumptions of elemental abundances, such as photon noise, are discussed, but not included in the software. It will be shown that the photon noise is much larger than the systematic uncertainty.

This work is supported by NASA under contract NNM07AB07C with the Harvard-Smithsonian Astrophysical Observatory Title: Multi-Stranded Coronal Loops - A Statistical Forward Model Authors: Kobelski, Adam; McKenzie, D. E. Bibcode: 2012AAS...22020431K Altcode: Strong evidence currently exists that coronal loops as observed in EUVs and soft X-rays are not monolithic structures, but actually exist as bundles of independent strands. It is of significant importance to determine the size and number density of these strands in order to better understand the spatial and temporal scales of magnetic reconnection in the corona. In order to empirically estimate these parameters, we have developed software to forward model the cooling of flaring loops as bundles of strands in order to estimate their observational signatures. By applying this forward model to a large database of flares observed by Yohkoh/SXT, we employ a statistical analysis to constrain the parameters in flaring coronal plasma. Results of this analysis will be presented. Title: Measuring Uncertainties in the Hinode X-Ray Telescope Authors: Kobelski, A.; Saar, S.; McKenzie, D. E.; Weber, M.; Reeves, K.; DeLuca, E. Bibcode: 2012ASPC..456..241K Altcode: We have developed estimates of the systematic photometric uncertainties the X-Ray Telescope (Kano et al. (2008)) on Hinode (Kosugi et al.(2007)). These estimates are included as optional returns from the standard XRT data reduction software, xrt_prep.pro. Included in the software estimates are uncertainties from instrument vignetting, dark current subtraction, split bias leveling, fourier filtering and JPEG compression. We show that these uncertainties are generally smaller than the photon counting uncertainty. However, due to the reliance on assumptions of plasma radiation models and elemental abundances, photon counting is not included in the software. Title: Forward Modeling for Unresolved Flaring Loops Authors: Kobelski, Adam; McKenzie, D. E. Bibcode: 2011SPD....42.1824K Altcode: 2011BAAS..43S.1824K The apparent width of observed coronal loops can have significant effects on the perceived evolution of flaring active regions. Frequently, comparing a model flare to observation requires an estimate of the filling factor of loops contributing to the signal. If the analysis assumes the loops are resolved, the cooling times derived from the observations are often much longer than predicted by models. We have developed software to forward model the cooling of flaring loops, and estimate their observational signatures. This allows exploration of the physical parameters necessary within a given model to reproduce the observations. We can then estimate the number of unresolved strands contained within the observed flare loop. We will present early results from this study using data from Yohkoh/SXT. The implementation of Hinode/XRT observations to improve our spatial resolution and thermal range will also discussed.

This work is supported by NASA under contract NNM07AB07C with the Harvard-Smithsonian Astrophysical Observatory. Yohkoh data are provided courtesy of the NASA-supported Yohkoh Legacy Archive at Montana State University. Title: Inferring Nonthermal Particle Characteristics from Thermal Emission Signatures: Temperature Evolution Authors: Kobelski, Adam; Winter, H.; McKenzie, D. E. Bibcode: 2010AAS...21640422K Altcode: 2010BAAS...41..903K In the impulsive phase of solar flares the primary source of plasma heating is collisions between the nonthermal particles and the ambient, thermal plasma in the flare loop. Thus the thermal emission (e.g., soft X-rays) can yield clues to the properties of the nonthermal beam. We have undertaken a study of the nonthermal particle signatures contained within the thermal emission of a flaring coronal loop to test predictions modeled in the dissertation of Winter (2009). Here we study loops as observed in thermal soft X-ray (SXR) emission by the Yohkoh satellite. We present the temperature evolution as viewed in SXR to that predicted by the model, and continue an analysis of the temporal profile of the SXR emission. Title: Inferring Nonthermal Particle Characteristics from Thermal Emission Signatures Authors: Kobelski, A.; Winter, H. D.; McKenzie, D. E. Bibcode: 2009AGUFMSH23A1528K Altcode: Much work has been done in characterizing the nonthermal particle beams found in flares. Most of this work has concentrated on the interpretation of hard X-ray (HXR) emission. While HXR emission does have a direct connection to the nonthermal particle beam, there are other emission mechanisms that can also provide insight into the nature of the nonthermal beam. In the impulsive phase of solar flares the primary source of plasma heating is collisions between the nonthermal particles and the ambient, thermal plasma in the flare loop. The properties of the nonthermal particle beam directly affect the heating of the thermal plasma. Thus the thermal emission (e.g., soft X-rays) can also yield clues to the properties of the nonthermal beam. Recent flare modeling in the dissertation of Winter (2009) makes specific predictions about the behavior of the soft X-ray (SXR) emission from the flaring loop, depending on the properties of the nonthermal particle beam. As an initial test of the applicability of these predictions to real flares, we have undertaken a comparison to HXR and SXR observations from the Yohkoh mission. We present preliminary results from the analysis of Yohkoh-observed solar flares, pursuant to the predictions of the model. Title: Thermal Evolution of Hyperon-Mixed Neutron Stars Authors: Tsuruta, S.; Sadino, J.; Kobelski, A.; Teter, M. A.; Liebmann, A. C.; Takatsuka, T.; Nomoto, K.; Umeda, H. Bibcode: 2009ApJ...691..621T Altcode: With the impressive amount of data that have poured out from Chandra and XMM/Newton X-ray space missions, as well as the lower energy band observations, we are now in the position where careful comparison of neutron star thermal evolution theories with observations will help us to distinguish among various competing theories. For instance, the latest theoretical and observational developments probably will contradict with the direct Urca cooling of neutron stars without some exotic particles. In this paper, we investigate one of the remaining possible fast cooling scenarios—direct Urca cooling of neutron stars in the hyperon-mixed phase. We conclude that this cooling scenario is a valid process if hyperon superfluidity is not too weak. Title: Sloan/Johnson-Cousins/2MASS Color Transformations for Cool Stars Authors: Davenport, James R. A.; West, Andrew A.; Matthiesen, Caleb K.; Schmieding, Michael; Kobelski, Adam Bibcode: 2006PASP..118.1679D Altcode: 2006astro.ph.11087D We present multicolor transformations and photometric parallaxes for a sample of 40 low-mass dwarfs selected from the Sloan Digital Sky Survey (SDSS) and the General Catalogue of Trigonometric Stellar Parallaxes. Our sample was reobserved at the Manastash Ridge Observatory (MRO) using both Sloan and Johnson-Cousin filters, and color transformations between the two photometric systems were derived. A subset of the sample had previously measured Johnson-Cousins photometry and parallaxes as well as 2MASS photometry. We observed these stars at MRO using Sloan filters and used these data to derive photometric parallax relations as well as SDSS/Johnson-Cousins/2MASS color transformations. We present the data and derived transformations for use in future low-mass-star studies.