Author name code: mckenzie ADS astronomy entries on 2022-09-14 author:"McKenzie, David Eugene" ------------------------------------------------------------------------ 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: 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: Realizing Comprehensive 3D Observations to Probe Magnetic Energy Storage and Release in the Corona Authors: Caspi, A.; Seaton, D. B.; Casini, R.; Downs, C.; Gibson, S.; Gilbert, H.; Glesener, L.; Guidoni, S.; Hughes, J. M.; McKenzie, D.; Reeves, K.; Saint-Hilaire, P.; Shih, A. Y.; West, M. Bibcode: 2022heli.conf.4058C Altcode: Understanding impulsive energy release in the solar corona requires knowledge of the 3D coronal magnetic field and 3D signatures of energy release through systematic multi-viewpoint observations, in many wavelengths, including coronal magnetometry. Title: Space-Based UV Spectropolarimetry for Chromospheric Magnetic Field Measurements Authors: McKenzie, D. E. Bibcode: 2022heli.conf.4051M Altcode: Quantitative measurements of the chromospheric magnetic field is essential for a predictive understanding of the energy budget of the upper solar atmosphere. UV spectropolarimetry provides a means for making these measurements. Title: New Approaches to Integrated Mission, Data, and Modeling Frameworks Authors: Seaton, D. B.; Caspi, A.; Casini, R.; Downs, C.; Gibson, S.; Gilbert, H.; Glesener, L.; Guidoni, S.; Hughes, J. M.; McKenzie, D.; Reeves, K.; Saint-Hilaire, P.; Shih, A.; West, M. Bibcode: 2022heli.conf.4057S Altcode: A new generation of heliophysics missions will require integration of data from multiple missions with analysis tools and physics-based models. We discuss strategies to develop a framework for systems-integrated data and analysis environments. Title: Extreme-ultraviolet Stellar Characterization for Atmospheric Physics and Evolution mission: motivation and overview Authors: France, Kevin; Fleming, Brian; Youngblood, Allison; Mason, James; Drake, Jeremy J.; Amerstorfer, Ute V.; Barstow, Martin; Bourrier, Vincent; Champey, Patrick; Fossati, Luca; Froning, Cynthia S.; Green, James C.; Grisé, Fabien; Gronoff, Guillaume; Hellickson, Timothy; Jin, Meng; Koskinen, Tommi T.; Kowalski, Adam F.; Kruczek, Nicholas; Linsky, Jeffrey L.; Lipscy, Sarah J.; McEntaffer, Randall L.; McKenzie, David E.; Miles, Drew M.; Patton, Tom; Savage, Sabrina; Siegmund, Oswald; Spittler, Constance; Unruh, Bryce W.; Volz, Máire Bibcode: 2022JATIS...8a4006F Altcode: 2022arXiv220113219F The Extreme-ultraviolet Stellar Characterization for Atmospheric Physics and Evolution (ESCAPE) mission is an astrophysics Small Explorer employing ultraviolet spectroscopy (EUV: 80 to 825 Å and FUV: 1280 to 1650 Å) to explore the high-energy radiation environment in the habitable zones around nearby stars. ESCAPE provides the first comprehensive study of the stellar EUV and coronal mass ejection environments that directly impact the habitability of rocky exoplanets. In a 20-month science mission, ESCAPE will provide the essential stellar characterization to identify exoplanetary systems most conducive to habitability and provide a roadmap for NASA's future life-finder missions. ESCAPE accomplishes this goal with roughly two-order-of-magnitude gains in EUV efficiency over previous missions. ESCAPE employs a grazing incidence telescope that feeds an EUV and FUV spectrograph. The ESCAPE science instrument builds on previous ultraviolet and x-ray instrumentation, grazing incidence optical systems, and photon-counting ultraviolet detectors used on NASA astrophysics, heliophysics, and planetary science missions. The ESCAPE spacecraft bus is the versatile and high-heritage Ball Aerospace BCP-Small spacecraft. Data archives will be housed at the Mikulski Archive for Space Telescopes. Title: Demonstration of Chromospheric Magnetic Mapping with CLASP2.1 Authors: McKenzie, David; Ishikawa, Ryohko; Trujillo Bueno, Javier; Auchere, F.; Kobayashi, Ken; Winebarger, Amy; Kano, Ryouhei; Song, Donguk; Okamoto, Joten; Rachmeler, Laurel; De Pontieu, Bart; Vigil, Genevieve; Belluzzi, Luca; Alsina Ballester, Ernest; del Pino Aleman, Tanausu; Bethge, Christian; Sakao, Taro; Stepan, Jiri Bibcode: 2021AGUFMSH52A..06M Altcode: Probing the magnetic nature of the Suns atmosphere requires measurement of the Stokes I, Q, U and V profiles of relevant spectral lines (of which Q, U and V encode the magnetic field information). Many of the magnetically sensitive lines formed in the chromosphere and transition region are in the ultraviolet spectrum, necessitating observations above the absorbing terrestrial atmosphere. The Chromospheric Layer Spectro-Polarimeter (CLASP2) sounding rocket was flown successfully in April 2019, as a follow-on to the successful flight in September 2015 of the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP). Both projects were funded by NASAs Heliophysics Technology and Instrument Development for Science (H-TIDeS) program to develop and test a technique for observing the Sun in ultraviolet light, and for quantifying the polarization of that light. By demonstrating successful measurement and interpretation of the polarization in hydrogen Lyman-alpha and the Mg II h and k spectral lines, the CLASP and CLASP2 missions are vital first steps towards routine quantitative characterization of the local thermal and magnetic conditions in the solar chromosphere. In October of 2021, we re-flew the CLASP2 payload with a modified observing program to further demonstrate the maturity of the UV spectropolarimetry techniques, and readiness for development into a satellite observatory. During the reflight, called CLASP2.1, the spectrograph slit was scanned across an active region plage to acquire a two-dimensional map of Stokes V/I, to demonstrate the ability of UV spectropolarimetry to yield chromospheric magnetic fields over a large area. This presentation will display preliminary results from the flight of CLASP2.1. 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: Opto-mechanical design of the ESCAPE Small Explorer: an EUV spectrograph for exoplanet host star irradiance and CME activity Authors: Fleming, Brian T.; France, Kevin; Hellickson, Timothy; Patton, Tom; Unruh, Bryce; Kruczek, Nicholas; McKenzie, David; Champey, Patrick; Cheimets, Peter; Hertz, Edward; Romaine, Suzanne; McEntaffer, Randall; Grisé, Fabien; Miles, Drew; Siegmund, Oswald; McPhate, Jason; Green, James; Beasley, Matthew Bibcode: 2021SPIE11821E..04F Altcode: The University of Colorado led Extreme-ultraviolet Stellar Characterization for Atmospheric Physics and Evolution (ESCAPE) small explorer mission concept is designed to measure the extreme- and far-ultraviolet (EUV; 80 - 560 A, 600 - 825 A, FUV; 1280 - 1650 A) irradiance and are activity of exoplanet host stars; essential measurements for assessing the stability of rocky planet atmospheres in the liquid-water habitable zone. The ESCAPE design consists of a fixed optical configuration with a grazing incidence Gregorian, or "Hetterick- Bowyer", telescope feeding grazing and normal incidence spectroscopic channels. The telescope is provided by a joint NASA Marshall Space Flight Center and Smithsonian Astrophysics Observatory team. The grazing incidence gratings have a radial profile and are ruled into single-crystal silicon using electron-beam lithography in the nanofabrication laboratory at Pennsylvania State University. Normal incidence gratings have aberration correcting holographic solutions and are supplied by Horiba Jobin Yvon. Spectra are imaged onto a curved microchannel plate detector supplied by the University of California, Berkeley. ESCAPE utilizes the Ball Aerospace BCP spacecraft. The simple, fixed configuration design of ESCAPE is projected to exceed the effective area of the last major EUV astrophysics spectrograph, EUV E-DS/S, by more than a factor of 50, providing unprecedented sensitivity in this essential bandpass for exoplanet host-star characterization. We report on the ESCAPE design, projected performance and mission implementation plan, as well as the trade studies carried out over Phase A to scope the first NASA EUV astrophysics mission in nearly 30 years. If selected, ESCAPE will launch in Fall 2025. Title: Thermodynamic Evolution of Solar Flare Supra-arcade Downflows Authors: Li, Z. F.; Cheng, X.; Ding, M. D.; Reeves, Katharine K.; Kittrell, DeOndre; Weber, Mark; McKenzie, David E. Bibcode: 2021ApJ...915..124L Altcode: 2021arXiv210709215L Solar flares are rapid energy release phenomena that appear as bright ribbons in the chromosphere and high temperature loops in the corona, respectively. Supra-arcade Downflows (SADs) are plasma voids that first come out above the flare loops and then move quickly toward the flare loop top during the decay phase of the flare. In our work, we study 20 SADs appearing in three flares. By differential emission measure (DEM) analysis, we calculate the DEM weighted average temperature and emission measure of the front region and the main body of SADs. It is found that the temperatures of the SAD front and body tend to increase during the course of SADs flowing downwards. The relationship between the pressure and temperature fits well with the adiabatic equation for both the SAD front and body, suggesting that the heating of SADs is mainly caused by adiabatic compression. Moreover, we also estimate the velocities of SADs via the Fourier Local Correlation Tracking method and find that increase of the temperature of the SAD front presents a correlation with the decrease of the SAD kinetic energy, while the SAD body does not, implying that the viscous process may also heat the SAD front in spite of a limited role. Title: Mapping of Solar Magnetic Fields from the Photosphere to the Top of the Chromosphere with CLASP2 Authors: McKenzie, D.; Ishikawa, R.; Trujillo Bueno, J.; Auchere, F.; del Pino Aleman, T.; Okamoto, T.; Kano, R.; Song, D.; Yoshida, M.; Rachmeler, L.; Kobayashi, K.; Narukage, N.; Kubo, M.; Ishikawa, S.; Hara, H.; Suematsu, Y.; Sakao, T.; Bethge, C.; De Pontieu, B.; Vigil, G.; Winebarger, A.; Alsina Ballester, E.; Belluzzi, L.; Stepan, J.; Asensio Ramos, A.; Carlsson, M.; Leenaarts, J. Bibcode: 2021AAS...23810603M Altcode: Coronal heating, chromospheric heating, and the heating & acceleration of the solar wind, are well-known problems in solar physics. Additionally, knowledge of the magnetic energy that powers solar flares and coronal mass ejections, important drivers of space weather, is handicapped by imperfect determination of the magnetic field in the sun's atmosphere. Extrapolation of photospheric magnetic measurements into the corona is fraught with difficulties and uncertainties, partly due to the vastly different plasma beta between the photosphere and the corona. Better results in understanding the coronal magnetic field should be derived from measurements of the magnetic field in the chromosphere. To that end, we are pursuing quantitative determination of the magnetic field in the chromosphere, where plasma beta transitions from greater than unity to less than unity, via ultraviolet spectropolarimetry. The CLASP2 mission, flown on a sounding rocket in April 2019, succeeded in measuring all four Stokes polarization parameters in UV spectral lines formed by singly ionized Magnesium and neutral Manganese. Because these ions produce spectral lines under different conditions, CLASP2 thus was able to quantify the magnetic field properties at multiple heights in the chromosphere simultaneously, as shown in the recent paper by Ishikawa et al. In this presentation we will report the findings of CLASP2, demonstrating the variation of magnetic fields along a track on the solar surface and as a function of height in the chromosphere; and we will illustrate what is next for the CLASP missions and the demonstration of UV spectropolarimetry in the solar chromosphere. Title: Critical Science Plan for the Daniel K. Inouye Solar Telescope (DKIST) Authors: Rast, Mark P.; Bello González, Nazaret; Bellot Rubio, Luis; Cao, Wenda; Cauzzi, Gianna; Deluca, Edward; de Pontieu, Bart; Fletcher, Lyndsay; Gibson, Sarah E.; Judge, Philip G.; Katsukawa, Yukio; Kazachenko, Maria D.; Khomenko, Elena; Landi, Enrico; Martínez Pillet, Valentín; Petrie, Gordon J. D.; Qiu, Jiong; Rachmeler, Laurel A.; Rempel, Matthias; Schmidt, Wolfgang; Scullion, Eamon; Sun, Xudong; Welsch, Brian T.; Andretta, Vincenzo; Antolin, Patrick; Ayres, Thomas R.; Balasubramaniam, K. S.; Ballai, Istvan; Berger, Thomas E.; Bradshaw, Stephen J.; Campbell, Ryan J.; Carlsson, Mats; Casini, Roberto; Centeno, Rebecca; Cranmer, Steven R.; Criscuoli, Serena; Deforest, Craig; Deng, Yuanyong; Erdélyi, Robertus; Fedun, Viktor; Fischer, Catherine E.; González Manrique, Sergio J.; Hahn, Michael; Harra, Louise; Henriques, Vasco M. J.; Hurlburt, Neal E.; Jaeggli, Sarah; Jafarzadeh, Shahin; Jain, Rekha; Jefferies, Stuart M.; Keys, Peter H.; Kowalski, Adam F.; Kuckein, Christoph; Kuhn, Jeffrey R.; Kuridze, David; Liu, Jiajia; Liu, Wei; Longcope, Dana; Mathioudakis, Mihalis; McAteer, R. T. James; McIntosh, Scott W.; McKenzie, David E.; Miralles, Mari Paz; Morton, Richard J.; Muglach, Karin; Nelson, Chris J.; Panesar, Navdeep K.; Parenti, Susanna; Parnell, Clare E.; Poduval, Bala; Reardon, Kevin P.; Reep, Jeffrey W.; Schad, Thomas A.; Schmit, Donald; Sharma, Rahul; Socas-Navarro, Hector; Srivastava, Abhishek K.; Sterling, Alphonse C.; Suematsu, Yoshinori; Tarr, Lucas A.; Tiwari, Sanjiv; Tritschler, Alexandra; Verth, Gary; Vourlidas, Angelos; Wang, Haimin; Wang, Yi-Ming; NSO and DKIST Project; DKIST Instrument Scientists; DKIST Science Working Group; DKIST Critical Science Plan Community Bibcode: 2021SoPh..296...70R Altcode: 2020arXiv200808203R The National Science Foundation's Daniel K. Inouye Solar Telescope (DKIST) will revolutionize our ability to measure, understand, and model the basic physical processes that control the structure and dynamics of the Sun and its atmosphere. The first-light DKIST images, released publicly on 29 January 2020, only hint at the extraordinary capabilities that will accompany full commissioning of the five facility instruments. With this Critical Science Plan (CSP) we attempt to anticipate some of what those capabilities will enable, providing a snapshot of some of the scientific pursuits that the DKIST hopes to engage as start-of-operations nears. The work builds on the combined contributions of the DKIST Science Working Group (SWG) and CSP Community members, who generously shared their experiences, plans, knowledge, and dreams. Discussion is primarily focused on those issues to which DKIST will uniquely contribute. Title: Mapping solar magnetic fields from the photosphere to the base of the corona Authors: Ishikawa, Ryohko; Bueno, Javier Trujillo; del Pino Alemán, Tanausú; Okamoto, Takenori J.; McKenzie, David E.; Auchère, Frédéric; Kano, Ryouhei; Song, Donguk; Yoshida, Masaki; Rachmeler, Laurel A.; Kobayashi, Ken; Hara, Hirohisa; Kubo, Masahito; Narukage, Noriyuki; Sakao, Taro; Shimizu, Toshifumi; Suematsu, Yoshinori; Bethge, Christian; De Pontieu, Bart; Dalda, Alberto Sainz; Vigil, Genevieve D.; Winebarger, Amy; Ballester, Ernest Alsina; Belluzzi, Luca; Štěpán, Jiří; Ramos, Andrés Asensio; Carlsson, Mats; Leenaarts, Jorrit Bibcode: 2021SciA....7.8406I Altcode: 2021arXiv210301583I Routine ultraviolet imaging of the Sun's upper atmosphere shows the spectacular manifestation of solar activity; yet we remain blind to its main driver, the magnetic field. Here we report unprecedented spectropolarimetric observations of an active region plage and its surrounding enhanced network, showing circular polarization in ultraviolet (Mg II $h$ & $k$ and Mn I) and visible (Fe I) lines. We infer the longitudinal magnetic field from the photosphere to the very upper chromosphere. At the top of the plage chromosphere the field strengths reach more than 300 gauss, strongly correlated with the Mg II $k$ line core intensity and the electron pressure. This unique mapping shows how the magnetic field couples the different atmospheric layers and reveals the magnetic origin of the heating in the plage chromosphere. Title: The Magnetic Skeleton of the Solar Corona Over Several Solar Rotations: Features, Analysis, and Community Availability Authors: Malanushenko, A. V.; Gibson, S. E.; Kucera, T. A.; McKenzie, D. E. Bibcode: 2020AGUFMSH041..02M Altcode: The magnetic field in the solar corona is thought to be the main driver for solar eruptive events, such as flares and coronal mass ejections. The coronal magnetic field is therefore important to study, but it is difficult to measure directly. Usually, it is studied through extrapolations based on photospheric magnetograms. As the corona is thought to be mostly in a state of equilibrium, equations of low-beta equilibria are often used in order to study the structure of the field, or to estimate the magnetic energy. One of the complications that arise from this approach is that the solar photosphere itself is not a low-beta equilibrium.

Images of the solar corona in extreme ultraviolet (EUV) do not directly measure the magnetic field; however, they do reveal structures from which information about magnetic field can be inferred. For example, coronal loops are thought to trace out magnetic field lines, coronal cavities are bounded by magnetic surfaces, coronal holes are areas of magnetic flux that is open to the heliosphere, and plasma flows are also thought to follow lines of magnetic field. In other wavelengths, coronal spectropolarimetry (SP) can provide us with proxies for magnetic field strength and reveal plasma flows along the line of sight, off the limb. The EUV images and SP data are frequently used to validate magnetic field models. Additionally, new models are emerging which can use these data directly as additional constraints.

We aggregate available relevant features seen in EUV and SP data for several solar rotations. We apply existing techniques to infer 3D constraints on the magnetic field from these data. The result is an interactive 3D model based on these constraints for a full rotation, or a "magnetic skeleton". It is modular, so individual constraints can be easily added, or only selected constraints can be used. The features could be exported in either graphical or numerical form. The possible uses of our approach include validation of magnetic models that are based on extrapolations alone. Some models allow for using additional coronal constraints directly. These 'skeletons' can also be used in non-magnetic-modeling applications, as a simple, interactive reference for features seen in a given rotation. We make the models available to the community and show how to obtain and use them. 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: The Solar Cruiser Solar Sail Technology Demonstration Mission: An ESPA-class Rideshare Enabling New Capabilities for Space Science Authors: Johnson, L.; Carr, J.; McKenzie, D. E.; Newmark, J. S.; Turse, D. Bibcode: 2020AGUFMSH040..11J Altcode: Selected by NASA as a candidate ESPA-class rideshare technology demonstration mission to launch with the Interstellar Mapping and Acceleration Probe (IMAP) mission in 2024, the NASA MSFC Solar Cruiser mission would mature solar sail technology for use in future Heliophysics missions, as well as missions of interest across a broad user community including NOAA, Earth, and Planetary Sciences. Solar sails, which use reflected sunlight to derive thrust, can be used to create artificial equilibria and near-indefinite station-keeping at locations sunward of L1 along the Sun Earth Line (SEL), or at any desired offset from the SEL leading or trailing the Earth in its orbit. They can change the heliocentric inclination of a spacecraft from the ecliptic to as high as solar polar, stopping and remaining at any intermediate inclination orbit in between or can be used around a range of solar system bodies.

The Solar Cruiser mission would fly a small spacecraft (~100 kg) with a large (>1600 square meter) solar sail containing embedded reflectivity control devices (RCDs) and photovoltaic cells, attaining a characteristic acceleration of >0.12 mm/s2. The mission concept includes successful deployment of the solar sail, validation of all sail subsystems, controlled station-keeping inside of the Sun-Earth L1 point, demonstration of pointing performance for science imaging, and finally an increase in heliocentric inclination (out of the ecliptic plane).

Solar Cruiser would serve as a pathfinder for missions that observe the solar environment from unique vantage points such sub-L1 and at high solar inclinations, opening a fundamentally new range of observational capabilities for the Heliophysics Program and for space weather science and monitoring. Observations away from the SEL present unique opportunities for answering outstanding science questions of Heliophysics, for improving space-weather monitoring and prediction, and for revealing new discoveries about our Sun and solar system. Title: Optical design of the Chromospheric LAyer Spectro-Polarimeter (CLASP2) Authors: Tsuzuki, Toshihiro; Ishikawa, Ryohko; Kano, Ryouhei; Narukage, Noriyuki; Song, Donguk; Yoshida, Masaki; Uraguchi, Fumihiro; Okamoto, Takenori J.; McKenzie, David; Kobayashi, Ken; Rachmeler, Laurel; Auchere, Frederic; Trujillo Bueno, Javier Bibcode: 2020SPIE11444E..6WT Altcode: Chromospheric LAyer Spectro-Polarimeter (CLASP2) was a sounding rocket experiment, which is a follow-up mission to the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP1) in 2015. To measure the magnetic fields in the upper solar atmosphere in a highly quantitative manner, CLASP2 changes the target wavelengths from the hydrogen Ly-α line (121.567 nm) to Mg II lines near 280 nm. We reused the main structure and most of the optical components in the CLASP1 instrument, which reduced the turnaround time and cost. We added a magnifying optical system to maintain the wavelength resolution, even at the longer wavelength of CLASP2. Here, we describe the optical design and performance of the CLASP2 instrument. Title: The High Inclination Solar Mission (HISM) Authors: Kobayashi, K.; Johnson, L.; Thomas, H. D.; McIntosh, S. W.; McKenzie, D. E.; Newmark, J. S.; Wright, K. H., Jr.; Bean, Q.; Fabisinski, L.; Capizzo, P. D.; Clements, K. R.; Carr, J.; Heaton, A.; Baysinger, M.; Sutherlin, S. G.; Garcia, J. C.; Medina, K.; Turse, D. Bibcode: 2020AGUFMSH0110004K Altcode: The High Inclination Solar Mission (HISM) is an out-of-the-ecliptic solar sail mission concept for observing the Sun and the heliosphere. The mission profile is based on the Solar Polar Imager concept: initially spiraling in to a 0.48 AU ecliptic orbit, then increasing the orbital inclination at a rate of up to 10° degrees per year, ultimately reaching a heliographic inclination of >75°. The orbital profile is achieved using solar sails based on the sail design for the Solar Cruiser mission, currently in Phase-A study at NASA Marshall Space Flight Center.

An initial instrument complement was assumed for the study, consisting of a combination of remote, in-situ, and plasma wave instruments with a total mass of 66 kg. These provide a comprehensive suite of instruments to study the solar polar regions and connections to the heliosphere.

The 7,000 m2 sail used in the mission assessment is a direct extension of the 4-quadrant 1,666 m2 Solar Cruiser design and employs the same type of high strength composite boom, deployment mechanism, and membrane technology. The sail system modeled is spun (~1 rpm) to assure required boom characteristics with margin. The spacecraft bus features a fine-pointing 3-axis stabilized instrument platform that allows full science observations as soon as the spacecraft reaches a solar distance of 0.48 AU. The spacecraft provides 95W power to science instruments and 8 Gbit/day downlink capability. Title: The Solar Cruiser Mission Concept — Enabling New Vistas for Heliophysics Authors: Johnson, L.; McKenzie, D.; Newmark, J. Bibcode: 2020AAS...23610608J Altcode: Selected by NASA as a candidate technology demonstration mission for flight in 2024, the NASA MSFC Solar Cruiser mission will mature solar sail technology for use in future Heliophysics missions, as well as missions of interest across a broad user community including NOAA, Earth and Planetary Sciences, etc. Solar sails can be used to create artificial equilibria and near-indefinite station-keeping at locations sunward of L1 along the Sun Earth Line (SEL), or at any desired offset from the SEL leading or trailing the Earth in its orbit. They can change the heliocentric inclination of a spacecraft from the ecliptic to as high as solar polar, stopping and remaining at any intermediate inclination orbit in between or can be used around a range of solar system bodies. The Solar Cruiser mission would fly a small spacecraft with a large (>1500 square meter) solar sail containing embedded reflectivity control devices (RCDs) and photovoltaic cells. The mission concept includes successful deployment of the solar sail, validation of all sail subsystems, controlled station-keeping inside of the Sun-Earth L1 point, demonstration of pointing performance for science imaging, and finally an increase in heliocentric inclination (out of the ecliptic plane).Solar Cruiser would serve as a pathfinder for missions that observe the solar environment from unique vantage points such as a high inclination solar mission, opening a fundamentally new range of observational capabilities for the Heliophysics Program and for space weather monitoring. Observations away from the Sun-Earth line (SEL) present unique opportunities for answering the outstanding science questions of Heliophysics, for improving space-weather monitoring and prediction, and for revealing new discoveries about our Sun and solar system. High solar inclinations are particularly compelling. Investment in, and demonstration of, the technology needed to enable polar missions is essential to making this unique vantage point a reality in the next decade. Title: The High Inclination Solar Mission (HISM) mission concept Authors: Kobayashi, K.; McKenzie, D.; Johnson, L.; Rachmeler, L.; McIntosh, S.; Thomas, H. D.; Newmark, J.; Wright, K.; Curran, F. Bibcode: 2020AAS...23610609K Altcode: The High Inclination Solar Mission (HISM) is a concept for an out-of-the-ecliptic mission for observing the Sun and the heliosphere. The mission profile is largely based on the Solar Polar Imager concept; initially taking ~2.6 yrs to spiral in to a 0.48 AU equatorial orbit, then increasing the orbital inclination at a rate of 10 degrees per year, ultimately reaching an inclination of >75 degrees at the end of the mission. The orbital profile is achieved using solar sails derived from the technology currently being developed for the Solar Cruiser mission. HISM remote sensing instruments comprise an imaging spectropolarimeter (Doppler imager / magnetograph) and a visible light coronagraph. The in-situ instruments include a Faraday cup, an ion composition spectrometer, and magnetometers. Plasma wave measurements are made with electrical antennas and high speed magnetometers. The 7,000 m2 sail used in mission assessment is a direct extension of the 4-quadrant, 1,600 m2 Solar Cruiser Phase-A design and employs the same type of high strength composite boom, deployment mechanism, and membrane technology. The sail system modelled is spun (~1 rpm) to assure required boom characteristics with margin. The spacecraft bus features a fine-pointing 3-axis stabilized instrument 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: The High Inclination Solar Mission Authors: Kobayashi, K.; Johnson, L.; Thomas, H.; McIntosh, S.; McKenzie, D.; Newmark, J.; Heaton, A.; Carr, J.; Baysinger, M.; Bean, Q.; Fabisinski, L.; Capizzo, P.; Clements, K.; Sutherlin, S.; Garcia, J.; Medina, K.; Turse, D. Bibcode: 2020arXiv200603111K Altcode: The High Inclination Solar Mission (HISM) is a concept for an out-of-the-ecliptic mission for observing the Sun and the heliosphere. The mission profile is largely based on the Solar Polar Imager concept: initially spiraling in to a 0.48 AU ecliptic orbit, then increasing the orbital inclination at a rate of $\sim 10$ degrees per year, ultimately reaching a heliographic inclination of $>$75 degrees. The orbital profile is achieved using solar sails derived from the technology currently being developed for the Solar Cruiser mission, currently under development. HISM remote sensing instruments comprise an imaging spectropolarimeter (Doppler imager / magnetograph) and a visible light coronagraph. The in-situ instruments include a Faraday cup, an ion composition spectrometer, and magnetometers. Plasma wave measurements are made with electrical antennas and high speed magnetometers. The $7,000\,\mathrm{m}^2$ sail used in the mission assessment is a direct extension of the 4-quadrant $1,666\,\mathrm{m}^2$ Solar Cruiser design and employs the same type of high strength composite boom, deployment mechanism, and membrane technology. The sail system modelled is spun (~1 rpm) to assure required boom characteristics with margin. The spacecraft bus features a fine-pointing 3-axis stabilized instrument platform that allows full science observations as soon as the spacecraft reaches a solar distance of 0.48 AU. 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: 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: 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: 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: Measuring and Modeling the Rate of Separator Reconnection between an Emerging and an Existing Active Region Authors: McCarthy, Marika I.; Longcope, Dana W.; Malanushenko, Anna; McKenzie, David E. Bibcode: 2019ApJ...887..140M Altcode: 2019arXiv191106340M Magnetic reconnection occurs when new flux emerges into the corona and becomes incorporated into the existing coronal field. A new active region (AR) emerging in the vicinity of an existing AR provides a convenient laboratory in which reconnection of this kind can be quantified. We use high time-cadence 171 Å data from Solar Dynamics Observatory (SDO)/AIA, focused on new/old active region pair 11147/11149, to quantify reconnection. We identify new loops as brightenings within a strip of pixels between the regions. This strategy is premised on the assumption that the energy responsible for brightening a loop originates in magnetic reconnection. We catalog 301 loops observed in the 48 hr time period beginning with the emergence of AR 11149. The rate at which these loops appear between the two ARs is used to calculate the reconnection rate between them. We then fit these loops with magnetic field, solving for each loop’s field strength, geometry, and twist (via its proxy, coronal α). We find the rate of newly brightened flux overestimates the flux that could be undergoing reconnection. This excess can be explained by our finding that the interconnecting region is not at its lowest energy (constant-α) state; the extrapolations exhibit loop-to-loop variation in α. This flux overestimate may result from the slow emergence of AR 11149, which allows time for Taylor relaxation internal to the domain of the reconnected flux to bring the α distribution toward a single value, providing another mechanism for brightening loops after they are first created. Title: The Chromospheric Layer Spectro-Polarimeter (CLASP2) Sounding Rocket Mission: First Results Authors: McKenzie, D. E.; Ishikawa, R.; Trujillo Bueno, J.; Auchere, F.; Rachmeler, L.; Kano, R.; Song, D.; Okamoto, J.; Kobayashi, K.; Yoshida, M. Bibcode: 2019AGUFMSH44A..06M Altcode: A major challenge for heliophysics is to decipher the magnetic structure of the chromosphere, because of its vital role in the transport of energy into the corona and solar wind. Routine satellite measurements of the chromospheric magnetic field will dramatically improve our understanding of the chromosphere and its connection to the rest of the solar atmosphere. Before such a satellite can be considered for flight, we must refine the measurement techniques by exploring emission lines with a range of magnetic sensitivities. In 2015, CLASP achieved the first measurement of linear polarization produced by scattering processes in a far UV resonance line (hydrogen Lyman­-α), and the first exploration of the magnetic field (via the Hanle effect) and geometrical complexity in quiet regions of the chromosphere/­corona transition region. These measurements are a first step towards routine quantitative characterization of the local thermal and magnetic conditions in this key layer of the solar atmosphere.

Nonetheless, Lyman­-α is only one of the magnetically sensitive spectral lines in the UV spectrum. CLASP2 extends the capability of UV spectropolarimetry by acquiring ground­breaking measurements in the Mg II h and k spectral lines near 280 nm, whose cores form about 100 km below the Lyman-­α core. These lines are sensitive to a larger range of field strengths than Lyman­-α, through both the Hanle and Zeeman effects. CLASP2 captures measurements of linear and circular polarization to enable the first determination of all 4 Stokes parameters in chromospheric UV radiation. Coupled with numerical modeling of the observed spectral line polarization (anisotropic radiation pumping with Hanle, Zeeman and magneto-­optical effects), CLASP2 is a pathfinder for determination of the magnetic field's strength and direction, as well as of the geometry of the plasma in the upper solar chromosphere.

CLASP2 was launched from White Sands Missile Range in April 2019. In this presentation, we will summarize the characteristics of the CLASP2 flight, the performance of the UV telescope and spectropolarimeter, and our preliminary findings. Title: Center-to-Limb Variation of the polarization of Mg II h & k lines as measured by CLASP2 Authors: Rachmeler, L.; McKenzie, D. E.; Ishikawa, R.; Kano, R.; Trujillo Bueno, J.; Kobayashi, K.; Song, D.; Yoshida, M.; Auchere, F.; Okamoto, J. Bibcode: 2019AGUFMSH11D3380R Altcode: The Chromospheric LAyer SpectroPolarimeter 2 (CLASP2) is a sounding rocket that was launched from White Sands Missile Range in April 2019. CLASP2 is a reflight of the CLASP instrument, and has been modified to observe the polarization of the Magnesium II h & k lines in the solar chromosphere. The instrument contains a slit-jaw context imager at Lyman Alpha (~121.6nm) and two spectropolarimetric cameras that capture Mg II h & k near 280nm. A rotating polarization modulation unit allows us to capture the full polarization state of Mg II h & k; the measured polarization signals are sensitive to the Hanle and the Zeeman magnetic effects, and magneto-optical effects. The center-to-limb variations (CLV) of the intensity of these lines has been measured, but the CLV of the polarization signals has only been investigated theoretically. The first flight of CLASP, which measured the linear polarization of the Lyman alpha line, found a surprising lack of CLV in the line core (Kano et al. 2017), which has important implications for the magnetic strength and geometrical complexity of the chromosphere-corona transition region (Trujillo Bueno et al. 2018). We present here initial results on the CLV of the Mg II polarization signals. 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: Examination of Separator Reconnection Rates in a Series of Adjacent Emerging/Existing Active Region Pairs Authors: McCarthy, M.; Longcope, D. W.; Malanushenko, A. V.; McKenzie, D. E. Bibcode: 2019AGUFMSH11D3387M Altcode: Changes in magnetic field line topology must be occurring when new flux emerges in the solar corona in order for it to become incorporated in the existing coronal field. Magnetic reconnection is the process responsible for this incorporation. We have previously quantified this process using a system in which a new active region (AR) emerges in the vicinity of an existing one by cataloging the loops formed between them. We make a spatial/temporal stack plot of the region between the ARs by extracting the pixels along a virtual slit. A persistent, bright streak in such a plot indicates a coronal loop connecting the newly emerging flux to the existing AR. We assert that loops formed post-emergence between the ARs are initially the result of reconnection. This work presents an extension of our data set to include 12 new emergence events using high time-cadence data from SDO/AIA. Our data set includes several events in which no reconnected loops seem to form between the two ARs. We present an improved method of our loop cataloging procedure. Previous studies of such events have both under and over-sampled the expected reconnected flux formed between the two regions, and included a variety of delays between the emergence of the new AR and the onset of reconnection. To elucidate such discrepancies, we fit loops using a linear force-free field (LFFF) model which we then use to construct a full, non-linear force-free field (NLFFF) model of the system.

This work was supported by NASA's HGI program. 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: Heating Features of Interesting Supra-arcade Downflows Authors: Li, Z.; Kittrell, D.; Reeves, K.; Weber, M.; McKenzie, D. E.; Freed, M. Bibcode: 2019AGUFMSH11D3378L Altcode: Supra-arcade downflows (SADs) have been observed above flare loops during the decay phase of flare. They appear as tadpole-like dark plasma voids traveling towards the Sun. In areas surrounding where they appear, temperatures are often high. We aim to investigate temperature and heating mechanism of SADs. We apply our analysis to the M1.7 flare that occurred on 2012 July 12 and was observed by the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory. There are many obvious SADs above the arcade during this event in the AIA 131 Å channel. We calculate velocities of SADs using the Fourier Local Correlation Tracking (FLCT, Fisher & Welsch, 2008) method to derive velocities in the supra-arcade region. Using corks to track the calculated velocities, we find our velocity results are consistent with the SAD motions in the AIA 131 Å intensity movie. We use the velocities to derive the adiabatic heating caused by the compression of plasma. Preliminary results indicate that there is adiabatic heating in front of the SADs.

This work supported by the NSF-REU solar physics program at SAO, grant number AGS-1560313, the NSF SHINE program AGS-1723425, and NASA grant number 80NSSC18K0732. Title: The Chromospheric Layer Spectro-Polarimeter (CLASP2) Sounding Rocket Mission: First Results Authors: McKenzie, David Eugene; Ishikawa, Ryohko; Kano, Ryouhei; Rachmeler, Laurel; Trujillo Bueno, Javier; Kobayashi, Ken; Song, Donguk; Yoshida, Masaki; Auchere, Frederic; Okamoto, Takenori Bibcode: 2019AAS...23412601M Altcode: A major challenge for heliophysics is to decipher the magnetic structure of the chromosphere, because of its vital role in the transport of energy into the corona and solar wind. Routine satellite measurements of the chromospheric magnetic field will dramatically improve our understanding of the chromosphere and its connection to the rest of the solar atmosphere. Before such a satellite can be considered for flight, we must refine the measurement techniques by exploring emission lines with a range of magnetic sensitivities. In 2015, CLASP achieved the first measurement of linear polarization produced by scattering processes in a far UV resonance line (hydrogen Lyman-α), and the first exploration of the magnetic field (via the Hanle effect) and geometrical complexity in quiet regions of the chromosphere-corona transition region. These measurements are a first step towards routine quantitative characterization of the local thermal and magnetic conditions in this key layer of the solar atmosphere.

Nonetheless, Lyman-α is only one of the magnetically sensitive spectral lines in the UV spectrum. CLASP2 extends the capability of UV spectropolarimetry by acquiring ground-breaking measurements in the Mg II h and k spectral lines near 280 nm, whose cores form about 100 km below the Lyman-α core. These lines are sensitive to a larger range of field strengths than Lyman-α, through both the Hanle and Zeeman effects. CLASP2 will capture measurements of linear and circular polarization to enable the first determination of all 4 Stokes parameters in chromospheric UV radiation. Coupled with numerical modeling of the observed spectral line polarization (anisotropic radiation pumping with Hanle, Zeeman and magneto-optical effects), CLASP2 is a pathfinder for determination of the magnetic field's strength and direction, as well as of the geometry of the plasma in the upper solar chromosphere.

CLASP2 will launch from White Sands Missile Range in April 2019. In this presentation, we will summarize the characteristics of the CLASP2 flight, the performance of the UV telescope and spectropolarimeter, and our preliminary findings. Title: Lyman-α imaging polarimetry with the CLASP2 sounding rocket mission Authors: Kano, Ryouhei; Ishikawa, Ryohko; McKenzie, David Eugene; Trujillo Bueno, Javier; Song, Donguk; Yoshida, Masaki; Okamoto, Takenori; Rachmeler, Laurel; Kobayashi, Ken; Auchere, Frederic Bibcode: 2019AAS...23430216K Altcode: Ultraviolet polarimetry offers a unique opportunity to explore the upper solar chromosphere and the transition region (TR) to the million-degree corona. These outer atmospheric regions play a key role in the transfer of mass and energy from the solar photosphere to the corona. With a sounding rocket experiment called the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP), in September 2015 we succeeded in obtaining the first measurement of the linear polarization produced by scattering processes in the hydrogen Lyman-α line of the solar disk radiation. The analysis and interpretation of such spectro-polarimetric observation allowed us to obtain information on the geometrical complexity of the corrugated surface that delineates the TR, as well as on the magnetic field strength via the Hanle effect. At the same time, the CLASP slit-jaw (SJ) optics system, which is a Lyman-α filter imager characterized by a FWHM= 7 nm, allowed us to obtain broad-band Stokes-I and Q/I images over a large field of view. The obtained broad-band Q/I images are dominated by the scattering polarization signals of the Lyman-α wings, and not by the much weaker line-center signals where the Hanle effect operates. Recently, Alsina Ballester et al. (2019, ApJ, in press) showed that the scattering polarization signals of the Lyman-α wings are sensitive to chromospheric magnetic fields via the magneto-optical effects. Therefore, Lyman-α imaging polarimetry is of scientific interest also for magnetic-field investigations. On April 11, 2019, we performed another sounding rocket experiment, called the Chromospheric LAyer Spectro-Polarimeter (CLASP2). We used the same instrument after significant modifications in order to obtain spectro-polarimetric observations of a plage and a quiet region in the ionized magnesium lines around 280 nm (i.e., the Mg II h & k lines). At the same time, the CLASP2 SJ optics system allowed us to obtain broad-band Q/I and U/I images at the Lyman-α wavelength, in addition to the well-known SJ intensity images. In this presentation, we provide a first overview of the CLASP2 SJ data. Title: Measuring and modeling the rate of separator reconnection between an emerging and existing active region Authors: McCarthy, Marika; Longcope, Dana; Malanushenko, Anna; McKenzie, David Eugene Bibcode: 2019AAS...23411705M Altcode: Magnetic reconnection must occur when new flux emerges into the corona and becomes incorporated into the existing coronal field. A new active region (AR) emerging in the vicinity of an existing AR provides a convenient laboratory in which reconnection of this kind can be quantified. We perform such a measurement using high time-cadence 171 Å data from SDO/AIA of active region NOAA AR11149 which emerged in the vicinity of AR11147 beginning on 20 January 2011. We make a spatial/temporal stack plot of the region between the ARs by extracting the pixels along a virtual slit. A persistent, bright streak in such a plot indicates a bright coronal loop connecting the newly emerging flux to the existing AR. This loop must have been formed through a process of coronal reconnection across the separator separating the four topologically distinct flux systems. We assume further that energy released during that reconnection is responsible for its brightening. We catalog 205 loops observed in the a 48-hour time period beginning with the emergence of AR 11149. The rate at which new magnetic flux appears is used to calculate the rate of separator reconnection. We can further fit these cataloged field lines using a linear force-free field (LFFF) extrapolation, solving for an individual loop's field strength and twist. Ultimately, we find the rate of newly-brightened flux overestimates the flux which could be undergoing reconnection. This excess can be explained by our finding that the interconnecting region is not at its lowest energy (constant-α) state; the LFFF modeling shows a variation in values of α. This overestimate might be the result of the region's unusually slow emergence, providing time for internal Taylor-relaxation reconnection of the interconnecting flux following its initial formation by reconnection. We support this hypothesis by computing the rates of brightening within the plane of the virtual slit. This work was supported by NASA's HGI program. Title: CLASP2: The Chromospheric LAyer Spectro-Polarimeter Authors: McKenzie, D. E.; Ishikawa, R.; Trujillo Bueno, J.; Auchére, F.; Rachmeler, L. A.; Kubo, M.; Kobayashi, K.; Winebarger, A. R.; Bethge, C. W.; Narukage, N.; Kano, R.; Ishikawa, S.; de Pontieu, B.; Carlsson, M.; Yoshida, M.; Belluzzi, L.; Štěpán, J.; del Pino Alemán, T.; Alsina Ballester, E.; Asensio Ramos, A. Bibcode: 2019ASPC..526..361M Altcode: The hydrogen Lyman-α line at 121.6 nm and the Mg k line at 279.5 nm are especially relevant for deciphering the magnetic structure of the chromosphere since their line-center signals are formed in the chromosphere and transition region, with unique sensitivities to magnetic fields. We propose the Chromospheric LAyer Spectro-Polarimeter (CLASP2), to build upon the success of the first CLASP flight, which measured the linear polarization in H I Lyman-α. The existing CLASP instrument will be refitted to measure all four Stokes parameters in the 280 nm range, including variations due to the anisotropic radiation pumping, the Hanle effect, and the Zeeman effect. Title: Quantifying Turbulent Dynamics Found within the Plasma Sheets of Multiple Solar Flares Authors: Freed, Michael S.; McKenzie, David E. Bibcode: 2018ApJ...866...29F Altcode: It is vital to our understanding of solar flares that we discern how turbulent motion can affect the magnetic reconnection process. The objective of this study is to quantify the velocity and vorticity structures inherent in the observed motions found in a plasma sheet above arcades during a solar flare. The most noticeable features in these plasma sheets are the supra-arcade downflows (SADs) that sporadically enter the field of view. This work is also attempting to ascertain what effect these SADs have on the flow of plasma at different length scales. Contrast-enhanced images from five flares observed with the Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) and Transition Region and Coronal Explorer (TRACE) were used to construct velocity maps—in the plane of the sky—via a Fourier local correlation tracking program. Power-law indices (α) were calculated from the power spectral densities (PSDs) associated with the intensity, kinetic energy, and enstrophy structures of these plasma sheets. Velocity oscillations are observed to be approximately three times stronger for velocities that are perpendicular (V ϕ ) instead of parallel (V ρ ) to the magnetic field’s direction. Four of the flares observed were used for producing the following plasma sheet properties: kinetic energy PSD indices with only V ρ were -0.15 ≤ α ρ ≤ 0.08, kinetic energy PSD indices with only V ϕ were -1.59 ≤ α ϕ ≤ -1.46, kinetic energy PSD indices with both velocities were -0.89 ≤ α ≤ -0.83, enstrophy PSD indices were 0.87 ≤ α ≤ 0.97, kinetic energy density was 16.6 km2 s-2 ≤ ɛ ≤ 60.0 km2 s-2, and enstrophy density was 1.2 × 10-6 s-2 ≤ ω ≤ 2.8 × 10-6 s-2. Title: "Building a Magnetic Skeleton of the Solar Corona: Towards Better 3-D Constraints on the Coronal Magnetic Field Authors: Malanushenko, Anna; Gibson, Sarah; Kucera, Therese; McKenzie, David Bibcode: 2018cosp...42E2139M Altcode: The energy stored in the solar magnetic field is what is powering many violent explosive events in the solar atmosphere, or the corona. Some of these events result in the coronal mass ejections (CME's) released into the interplanetary space. The magnetic field in the solar corona is therefore very important to know, yet it is very difficult to measure. Most of the time it is modeled with the magnetic maps at the solar surface used as boundary conditions. The magnetic maps on the surface are therefore also important to know, yet the full vector of the field on the surface is also difficult to measure. Once such measurements are made, constructing a model capable of predicting eruptive potential of a given region is on its own a complicated task. One of the problems arising is that that the equations for low-beta equilibria, which are often used to describe the coronal field, do not, strictly speaking, work for the solar surface. In short, we need better inputs to model the solar corona. The use of non-magnetic and non-surface constraints on the magnetic field becomes increasingly popular. For example, the paths of filaments can be used to guide flux rope trajectories; the loops of active regions, seen in extreme ultraviolet (EUV) can be used to obtain 3-D trajectories of magnetic field lines and estimate electric currents flowing along them. We are currently exploring ways to use other sources of data, such as flows in prominences and coronal spectropolarimetric data, in a similar fashion. I will talk about this work, and about our project of aggregating many different sources of non-magnetic 3-D constraints on the magnetic field. The resulting 'skeleton' can be used to constraint global field models, or to validate models obtained in traditional ways. We intend to develop a pipeline and assemble several skeletons for several instances in time of the Sun, which we will then release to community. Title: Current State of UV Spectro-Polarimetry and its Future Direction Authors: Ishikawa, Ryohko; Sakao, Taro; Katsukawa, Yukio; Hara, Hirohisa; Ichimoto, Kiyoshi; Shimizu, Toshifumi; Kubo, Masahito; Auchere, Frederic; De Pontieu, Bart; Winebarger, Amy; Kobayashi, . Ken; Kano, Ryouhei; Narukage, Noriyuki; Trujillo Bueno, Javier; Song, Dong-uk; Manso Sainz, Rafael; Asensio Ramos, Andres; Leenaarts, Jorritt; Carlsson, Mats; Bando, Takamasa; Ishikawa, Shin-nosuke; Tsuneta, Saku; Belluzzi, Luca; Suematsu, Yoshinori; Giono, Gabriel; Yoshida, Masaki; Goto, Motoshi; Del Pino Aleman, Tanausu; Stepan, Jiri; Okamoto, Joten; Tsuzuki, Toshihiro; Uraguchi, Fumihiro; Champey, Patrick; Alsina Ballester, Ernest; Casini, Roberto; McKenzie, David; Rachmeler, Laurel; Bethge, Christian Bibcode: 2018cosp...42E1564I Altcode: To obtain quantitative information on the magnetic field in low beta regions (i.e., upper chromosphere and above) has been increasingly important to understand the energetic phenomena of the outer solar atmosphere such as flare, coronal heating, and the solar wind acceleration. In the UV range, there are abundant spectral lines that originate in the upper chromosphere and transition region. However, the Zeeman effect in these spectral lines does not give rise to easily measurable polarization signals because of the weak magnetic field strength and the larger Doppler broadening compared with the Zeeman effect. Instead, the Hanle effect in UV lines is expected to be a suitable diagnostic tool of the magnetic field in the upper atmospheric layers. To investigate the validity of UV spectro-polarimetry and the Hanle effect, the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP), which is a NASA sounding- rocket experiment, was launched at White Sands in US on September 3, 2015. During its 5 minutes ballistic flight, it successfully performed spectro-polarimetric observations of the hydrogen Lyman-alpha line (121.57 nm) with an unprecedentedly high polarization sensitivity of 0.1% in this wavelength range. CLASP observed the linear polarization produced by scattering process in VUV lines for the first time and detected the polarization signals which indicate the operation of the Hanle effect. Following the success of CLASP, we are confident that UV spectro-polarimetry is the way to proceed, and we are planning the second flight of CLASP (CLASP2: Chromospheric LAyer SpectroPolarimeter 2). For this second flight we will carry out spectro-polarimetry in the Mg II h and k lines around 280 nm, with minimum modifications of the CLASP1 instrument. The linear polarization in the Mg II k line is induced by scattering processes and the Hanle effect, being sensitive to magnetic field strengths of 5 to 50 G. In addition, the circular polarizations in the Mg II h and k lines induced by the Zeeman effect can be measurable in at least plage and active regions. The combination of the Hanle and Zeeman effects could help us to more reliably infer the magnetic fields of the upper solar chromosphere. CLASP2 was selected for flight and is being developed for launch in the spring of 2019.Based on these sounding rocket experiments (CLASP1 and 2), we aim at establishing the strategy and refining the instrument concept for future space missions to explore the enigmatic atmospheric layers via UV spectro-polarimetry. Title: Wavefront error measurements and alignment of CLASP2 telescope with a dual-band pass cold mirror coated primary mirror Authors: Yoshida, Masaki; Song, Donguk; Ishikawa, Ryoko; Kano, Ryouhei; Katsukawa, Yukio; Suematsu, Yoshinori; Narukage, Noriyuki; Kubo, Masahito; Shinoda, Kazuya; Okamoto, Takenori J.; McKenzie, David E.; Rachmeler, Laurel A.; Auchère, Frédéric; Trujillo Bueno, Javier Bibcode: 2018SPIE10699E..30Y Altcode: "Chromospheric LAyer Spectro-Polarimeter (CLASP2)" is the next sounding rocket experiment of the "Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP)" that succeeded in observing for the first time the linear polarization spectra in the hydrogen Lyman-α line (121.6 nm) and is scheduled to be launched in 2019. In CLASP2, we will carry out full Stokes-vector spectropolarimetric observations in the Mg ii h and k lines near 280 nm with the spectro-polarimeter (SP), while imaging observations in the Lyman-α line will be conducted with the slitjaw optics (SJ). For the wavelength selection of CLASP2, the primary mirror of the telescope uses a new dual-band pass cold mirror coating targeting both at 121.6 nm and 280 nm. Therefore, we have to perform again the alignment of the telescope after the installation of the recoated primary mirror. Before unmounting the primary mirror from the telescope structure, we measured the wave-front error (WFE) of the telescope. The measured WFE map was consistent with what we had before the CLASP flight, clearly indicating that the telescope alignment has been maintained even after the flight. After the re-coated primary mirror was installed the WFE was measured, and coma aberration was found to be larger. Finally, the secondary mirror shim adjustments were carried out based on the WFE measurements. In CLASP2 telescope, we improved a fitting method of WFE map (applying 8th terms circular Zernike polynomial fitting instead of 37th terms circular Zernike fitting) and the improved method enables to achieve better performance than CLASP telescope. Indeed, WFE map obtained after the final shim adjustment indicated that the required specification (< 5.5 μm RMS spot radius) that is more stringent than CLASP telescope was met. Title: Optical alignment of the high-precision UV spectro-polarimeter (CLASP2) Authors: Song, Donguk; Ishikawa, Ryohko; Kano, Ryouhei; Yoshida, Masaki; Tsuzuki, Toshihiro; Uraguchi, Fumihiro; Shinoda, Kazuya; Hara, Hirohisa; Okamoto, Takenori J.; Auchère, Frédéric; McKenzie, David E.; Rachmeler, Laurel A.; Trujillo Bueno, Javier Bibcode: 2018SPIE10699E..2WS Altcode: Chromospheric LAyer Spectro-Polarimeter (CLASP2) is our next sounding rocket experiment after the success of Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP1). CLASP2 is scheduled to launch in 2019, and aims to achieve high precision measurements (< 0.1 %) of the linear and circular polarizations in the Mg ii h and k lines near the 280 nm, whose line cores originate in the upper solar chromosphere. The CLASP2 spectro-polarimeter follows very successful design concept of the CLASP1 instrument with the minimal modification. A new grating was fabricated with the same radius of curvature as the CLASP1 grating, but with a different ruling density. This allows us to essentially reuse the CLASP1 mechanical structures and layout of the optics. However, because the observing wavelength of CLASP2 is twice longer than that of CLASP1, a magnifier optical system was newly added in front of the cameras to double the focal length of CLASP2 and to maintain the same wavelength resolution as CLASP1 (0.01 nm). Meanwhile, a careful optical alignment of the spectro-polarimeter is required to reach the 0.01 nm wavelength resolution. Therefore, we established an efficient alignment procedure for the CLASP2 spectro-polarimeter based on an experience of CLASP1. Here, we explain in detail the methods for achieving the optical alignment of the CLASP2 spectro-polarimeter and discuss our results by comparing with the performance requirements. 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: Measuring separator reconnection between emerging and existing active regions using extreme ultraviolet imaging observations Authors: McCarthy, Marika; Longcope, Dana; McKenzie, David E.; Malanushenko, Anna V. Bibcode: 2018tess.conf20545M Altcode: Magnetic reconnection must be occurring when new flux emerges into the corona, in order that the flux become incorporated into the existing corona. The most evident, and easily quantified, example of this occurs when a new active region (AR) emerges in the vicinity of an existing AR. In a study of such emergence observed by TRACE, Longcope et al. (2005) found a delay of approximately 24 hours between the new AR emerging and its reconnection with the field of the existing AR. This turned out to be the only suitable event in the TRACE archive. Here we apply the same method to events observed by SDO/AIA. Using high time-cadence images in one EUV wavelength, such as 171 A, we make a spatial/temporal stack plot of the region between the ARs by extracting the pixel in a virtual slit. A persistent, bright streak indicates a bright coronal loop connecting the newly emerging flux to the existing AR. This loop must have been formed through a process of coronal reconnection across the separator separating the two flux systems. The rate at which new loops appear is used to compute the rate of separator reconnection. The continuous, high-cadence data from AIA permits flux transfer to be quantified for intervals exceeding 48 hours.

This work was supported by NASA's HGI program. 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: 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: 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: CLASP2: The Chromospheric LAyer Spectro-Polarimeter Authors: Rachmeler, Laurel A.; McKenzie, D. E.; Ishikawa, R.; Trujillo-Bueno, J.; Auchere, F.; Kobayashi, K.; Winebarger, A.; Bethge, C.; Kano, R.; Kubo, M.; Song, D.; Narukage, N.; Ishikawa, S.; De Pontieu, B.; Carlsson, M.; Yoshida, M.; Belluzzi, L.; Stepan, J.; del Pino Alemán, T.; Alsina Ballester, E.; Asensio Ramos, A. Bibcode: 2017shin.confE..79R Altcode: We present the instrument, science case, and timeline of the CLASP2 sounding rocket mission. The successful CLASP (Chromospheric Lyman-Alpha Spectro-Polarimeter) sounding rocket flight in 2015 resulted in the first-ever linear polarization measurements of solar hydrogen Lyman-alpha line, which is sensitive to the Hanle effect and can be used to constrain the magnetic field and geometric complexity of the upper chromosphere. Ly-alpha is one of several upper chromospheric lines that contain magnetic information. In the spring of 2019, we will re-fly the modified CLASP telescope to measure the full Stokes profile of Mg II h & k near 280 nm. This set of lines is sensitive to the upper chromospheric magnetic field via both the Hanle and the Zeeman effects. Title: A Bayesian Approach to Period Searching in Solar Coronal Loops Authors: Scherrer, Bryan; McKenzie, David Bibcode: 2017ApJ...837...24S Altcode: We have applied a Bayesian generalized Lomb-Scargle period searching algorithm to movies of coronal loop images obtained with the Hinode X-ray Telescope (XRT) to search for evidence of periodicities that would indicate resonant heating of the loops. The algorithm makes as its only assumption that there is a single sinusoidal signal within each light curve of the data. Both the amplitudes and noise are taken as free parameters. It is argued that this procedure should be used alongside Fourier and wavelet analyses to more accurately extract periodic intensity modulations in coronal loops. The data analyzed are from XRT Observation Program #129C: “MHD Wave Heating (Thin Filters),” which occurred during 2006 November 13 and focused on active region 10293, which included coronal loops. The first data set spans approximately 10 min with an average cadence of 2 s, 2″ per pixel resolution, and used the Al-mesh analysis filter. The second data set spans approximately 4 min with a 3 s average cadence, 1″ per pixel resolution, and used the Al-poly analysis filter. The final data set spans approximately 22 min at a 6 s average cadence, and used the Al-poly analysis filter. In total, 55 periods of sinusoidal coronal loop oscillations between 5.5 and 59.6 s are discussed, supporting proposals in the literature that resonant absorption of magnetic waves is a viable mechanism for depositing energy in the corona. Title: An Exploration of Heating Mechanisms in a Supra-arcade Plasma Sheet Formed after a Coronal Mass Ejection Authors: Reeves, Katharine K.; Freed, Michael S.; McKenzie, David E.; Savage, Sabrina L. Bibcode: 2017ApJ...836...55R Altcode: 2017arXiv170103497R We perform a detailed analysis of the thermal structure of the region above the post-eruption arcade for a flare that occurred on 2011 October 22. During this event, a sheet of hot plasma is visible above the flare loops in the 131 Å bandpass of the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory. Supra-arcade downflows (SADs) are observed traveling sunward through the post-eruption plasma sheet. We calculate differential emission measures using the AIA data and derive an emission measure weighted average temperature in the supra-arcade region. In areas where many SADs occur, the temperature of the supra-arcade plasma tends to increase, while in areas where no SADs are observed, the temperature tends to decrease. We calculate the plane-of-sky velocities in the supra-arcade plasma and use them to determine the potential heating due to adiabatic compression and viscous heating. Of the 13 SADs studied, 10 have noticeable signatures in both the adiabatic and the viscous terms. The adiabatic heating due to compression of plasma in front of the SADs is on the order of 0.1-0.2 MK/s, which is similar in magnitude to the estimated conductive cooling rate. This result supports the notion that SADs contribute locally to the heating of plasma in the supra-arcade region. We also find that in the region without SADs, the plasma cools at a rate that is slower than the estimated conductive cooling, indicating that additional heating mechanisms may act globally to keep the plasma temperature high. Title: Numerical Simulations of Plasma Dynamics in the Vicinity of a Retracting Flux Tube Authors: Scott, Roger B.; Longcope, Dana W.; McKenzie, David E. Bibcode: 2016ApJ...831...94S Altcode: In a previous paper, we presented an analytical, zero-β model for supra-arcade downflows in which a retracting flux tube deforms the surrounding magnetic field, constricting the flow of plasma along affected field lines and, in some cases, forcing the plasma to exhibit collimated shocks. Here we present a numerical simulation based on the same model construction—a retracting flux tube is treated as a rigid boundary around which the plasma is forced to flow and the magnetic field and plasma evolve according to the governing equations of magnetohydrodynamics. We find that the collimated shocks described in our previous study are recovered for plasma β in the range of 0 ≤ β ≲ 1, while for 1 ≲ β the behavior is similar to the simpler hydrodynamic case, with classical bow shocks forming when the acoustic Mach number approaches or exceeds unity. Furthermore, we find that while the plasma β is important for identifying the various types of behaviors, more important still is the Alfvén Mach number, which, if large, implies that the bulk kinetic energy of the fluid exceeds the internal energy of the magnetic field, thereby leading to the formation of unconfined, fast-mode magnetosonic shocks, even in the limit of small β. Title: Chromospheric LAyer SpectroPolarimeter (CLASP2) Authors: Narukage, Noriyuki; McKenzie, David E.; Ishikawa, Ryoko; Trujillo-Bueno, Javier; De Pontieu, Bart; Kubo, Masahito; Ishikawa, Shin-nosuke; Kano, Ryouhei; Suematsu, Yoshinori; Yoshida, Masaki; Rachmeler, Laurel A.; Kobayashi, Ken; Cirtain, Jonathan W.; Winebarger, Amy R.; Asensio Ramos, Andres; del Pino Aleman, Tanausu; Štępán, Jiri; Belluzzi, Luca; Larruquert, Juan Ignacio; Auchère, Frédéric; Leenaarts, Jorrit; Carlsson, Mattias J. L. Bibcode: 2016SPIE.9905E..08N Altcode: The sounding rocket Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP) was launched on September 3rd, 2015, and successfully detected (with a polarization accuracy of 0.1 %) the linear polarization signals (Stokes Q and U) that scattering processes were predicted to produce in the hydrogen Lyman-alpha line (Lyα 121.567 nm). Via the Hanle effect, this unique data set may provide novel information about the magnetic structure and energetics in the upper solar chromosphere. The CLASP instrument was safely recovered without any damage and we have recently proposed to dedicate its second flight to observe the four Stokes profiles in the spectral region of the Mg II h and k lines around 280 nm; in these lines the polarization signals result from scattering processes and the Hanle and Zeeman effects. Here we describe the modifications needed to develop this new instrument called the "Chromospheric LAyer SpectroPolarimeter" (CLASP2). Title: An Evaluation of Motions Found in Multiple Supra-Arcade Plasma Sheets with Local Correlation Tracking Authors: Freed, Michael; McKenzie, David Eugene Bibcode: 2016SPD....4730501F Altcode: Plasma sheets can be seen in the corona above arcade loops that form shortly after the eruption phase of a solar flare. These structures are considered to be the location where current sheets can form, which are a key component for magnetic reconnection to take place. The objective of this study is to quantify the motion seen in these plasma sheets and to determine how these characteristics might vary over multiple length scales. We use contrast-enhanced EUV observations of five different plasma sheets to construct velocity maps of plasma motion — in the plane of the sky — via a Fourier local correlation tracking program. These derived velocities were then used to calculate angle-integrated power spectral density of intensity, kinetic energy, and enstrophy to determine if any self-similarity exists. The derived velocity fields also allowed for measurements of the kinetic energy density, enstrophy density, and magnetic diffusivity. We will also present the first reported observational evidence of Kelvin-Helmholtz instabilities forming at the interface of supra-arcade downflows (SADs) and the surrounding supra-arcade plasma. Title: Inferring the Magnetohydrodynamic Structure of Solar Flare Supra-Arcade Plasmas from a Data-assimilated Field Transport Model Authors: Scott, Roger B.; McKenzie, David E.; Longcope, Dana W. Bibcode: 2016ApJ...819...56S Altcode: Supra-arcade fans are highly dynamic structures that form in the region above post-reconnection flare arcades. In these features the plasma density and temperature evolve on the scale of a few seconds, despite the much slower dynamics of the underlying arcade. Further, the motion of supra-arcade plasma plumes appears to be inconsistent with the low-beta conditions that are often assumed to exist in the solar corona. In order to understand the nature of these highly debated structures, it is, therefore, important to investigate the interplay of the magnetic field with the plasma. Here we present a technique for inferring the underlying magnetohydrodynamic processes that might lead to the types of motions seen in supra-arcade structures. Taking as a case study the 2011 October 22 event, we begin with extreme-ultraviolet observations and develop a time-dependent velocity field that is consistent with both continuity and local correlation tracking. We then assimilate this velocity field into a simplified magnetohydrodynamic simulation, which deals simultaneously with regions of high and low signal-to-noise ratio, thereby allowing the magnetic field to evolve self-consistently with the fluid. Ultimately, we extract the missing contributions from the momentum equation in order to estimate the relative strength of the various forcing terms. In this way we are able to make estimates of the plasma beta, as well as predict the spectral character and total power of Alfvén waves radiated from the supra-arcade region. Title: Analysis of Flows inside Quiescent Prominences as Captured by Hinode/Solar Optical Telescope Authors: Freed, M. S.; McKenzie, D. E.; Longcope, D. W.; Wilburn, M. Bibcode: 2016ApJ...818...57F Altcode: 2016arXiv160203821F Developing an understanding of how magnetic fields can become entangled in a prominence is important for predicting a possible eruption. This work investigates the kinetic energy and vorticity associated with plasma motion residing inside quiescent prominences (QPs). These plasma flow characteristics can be utilized to improve our understanding of how the prominence maintains a stable magnetic field configuration. Three different contrast-enhanced solar prominence observations from Hinode/Solar Optical Telescope were used to construct velocity maps—in the plane of the sky—via a Fourier local correlation tracking program. The resulting velocities were then used to perform the first-ever analysis of the two-dimensional kinetic energy and enstrophy spectra of a prominence. Enstrophy is introduced here as a means of quantifying the vorticity that has been observed in many QPs. The kinetic energy power spectral density (PSD) produced indices ranging from -1.00 to -1.60. There was a consistent anisotropy in the kinetic energy spectrum of all three prominences examined. Examination of the intensity PSD reveals that a different scaling relationship exists between the observed prominence structure and velocity maps. All of the prominences exhibited an inertial range of at least 0.8≤slant k≤slant 2.0 {rads} {{Mm}}-1. Quasi-periodic oscillations were also detected in the centroid of the velocity distributions for one prominence. Additionally, a lower limit was placed on the kinetic energy density (ɛ ∼ 0.22-7.04 {{km}}2 {{{s}}}-2) and enstrophy density (ω ∼ 1.43-13.69 × \quad {10}-16 {{{s}}}-2) associated with each prominence. Title: Calibration of Hinode/XRT for Coalignment Authors: Yoshimura, Keiji; McKenzie, David E. Bibcode: 2015SoPh..290.2355Y Altcode: 2015SoPh..tmp..106Y We present coalignment calibration procedures for the X-ray Telescope (XRT) onboard the Hinode satellite. We performed not only an XRT stand-alone calibration, but also cross calibration using data from the Helioseismic and Magnetic Imager (HMI) and the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). Several new methods we describe here may also be useful for the coalignment calibration of other instruments. We have developed a database of coalignment coefficients and software to access it, so that all XRT images can be easily and accurately overlaid onto the images from other instruments, especially AIA and HMI. Title: How Can We Recognize Tearing Mode Signatures When They Occur? Authors: McKenzie, David E. Bibcode: 2015shin.confE..10M Altcode: The tearing mode instability offers a route to accelerated reconnection in sheared magnetic fields, including in current sheets. Many 2D treatments of tearing-unstable current sheets reveal populations of magnetic islands, and suggest that the evolutions/distributions of these 2D islands should tell us something about how reconnection is progressing. But how will we recognize the islands in 3D? In recent years observational studies-both in situ and remote sensing-claim to have detected islands; some of these reports are promising. In this 'scene-setting' talk, I will review the observations, including some very recent observations from IRIS, with the objective of sparking a discussion about observable features of the tearing mode, logical tests for the presence of the tearing mode, and ultimately empirical studies of the conditions controlling reconnection within the current sheet. Title: Hinode/XRT Measurements of Turbulent Velocities in Flare Plasma Sheets Authors: McKenzie, David; Freed, Michael Bibcode: 2015TESS....120310M Altcode: The turbulent, dynamic motions that we observe in the hot plasma surrounding current sheets very likely distort the embedded magnetic fields, resulting in reduced length scales and locally augmented resistivities. These conditions may help to accelerate and/or prolong the reconnection in solar flares. Although we cannot as yet measure directly the magnetic fields in the corona, the velocity fields within the flare plasma sheets provide a means to study the conditions that control the spatial and temporal scales of reconnection, in the locations and at the times that are relevant to structuring the magnetic fields.The plasma sheets are observable in many flares in soft X-ray and EUV wavelengths, due to their high temperatures. For two recent flares observed with the Hinode X-Ray Telescope (XRT), we have analyzed the velocity fields with a local correlation tracking technique, and compared to measurements from the Solar Dynamics Observatory Atmospheric Imaging Assembly (SDO/AIA).This work is supported by NASA under contract NNM07AB07C with the Smithsonian Astrophysical Observatory, and by grant NNX14AD43G. Title: Spectral Analysis of Velocities in Quiescent Prominences Observed with Hinode Authors: McKenzie, David; Freed, Michael Bibcode: 2015TESS....130305M Altcode: High-resolution observations of solar prominences, especially with the Solar Optical Telescope (SOT) on Hinode, reveal the presence of upward and downward flows consistent with convection, at length scales that were not accessible with previous telescopes. Since prominences are magnetic structures, the strength and arrangement of their magnetic fields are crucial for determining whether a given prominence will erupt into a coronal mass ejection. Convective flows can twist and tangle those magnetic fields. However, the magnetic fields within the prominences are extremely difficult to measure; therefore measurements of the dynamics of the magnetized plasma in prominences, and the balance between magnetic and gas-pressure forces, are valuable for understanding how these apparently stable structures can evolve to become suddenly eruptive. We will show our findings from analysis of the dynamics in a few solar prominences using local correlation tracking, and make estimates of the kinetic energy, diffusivity, and vorticity.This work is supported by NASA under contract NNM07AB07C with the Smithsonian Astrophysical Observatory. Title: On the Magnetohydrodynamics of Supra-Arcade Fan Structures Authors: Scott, Roger B.; McKenzie, David; Longcope, Dana Bibcode: 2015TESS....140705S Altcode: Supra-Arcade Fan Structures are highly dynamic regions that form above post-reconnection arcades. In these regions, the plasma density and thermal structure evolve on the scale of a few seconds, despite the much slower dynamics of the underlying arcade. Further, the motion of supra-arcade plasma plumes appears to be inconsistent with the low-beta conditions that many authors assume to exist in the solar corona. In order to understand the nature of these highly debated structures it is, therefore, important to investigate the interplay of the magnetic field with the plasma. Here we present a technique for inferring the underlying MagnetoHydroDynamic processes that might lead to the types of motions seen in supra-arcade structures. We begin with EUV observations and develop a time dependent velocity field that is consistent with both mass conservation and local correlation tracking. We then assimilate this velocity field into a simplified MHD code, which deals simultaneously with regions of high and low SNR, thereby allowing the magnetic field to evolve self-consistently with the fluid. Ultimately, we extract the missing contributions from the underlying momentum equation in order to estimate the relative strength of forcing terms. In this way we are able to make estimates of the plasma beta as well as predicting the spectral character of radiated Alfvén waves. It is our hope that this work will help to improve our understanding of the energy balance in these complex regions and, thereby, contribute to our knowledge of the solar corona as a whole. This work is supported by NASA under contract NNM07AB07C with the Smithsonian Astrophysical Observatory, and by grant NNX14AD43G. Title: Three-Year Global Survey of Coronal Null Points from Potential-Field-Source-Surface (PFSS) Modeling and Solar Dynamics Observatory (SDO) Observations Authors: Freed, M. S.; Longcope, D. W.; McKenzie, D. E. Bibcode: 2015SoPh..290..467F Altcode: 2014SoPh..tmp..136F; 2014arXiv1410.4493F This article compiles and examines a comprehensive coronal magnetic-null-point survey created by potential-field-source-surface (PFSS) modeling and Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) observations. The locations of 582 potential magnetic null points in the corona were predicted from the PFSS model between Carrington Rotations (CR) 2098 (June 2010) and 2139 (July 2013). These locations were manually inspected, using contrast-enhanced SDO/AIA images in 171 Å at the East and West solar limb, for structures associated with nulls. A Kolmogorov-Smirnov (K-S) test showed a statistically significant difference between observed and predicted latitudinal distributions of null points. This finding is explored further to show that the observability of null points could be affected by the Sun's asymmetric hemisphere activity. Additional K-S tests show no effect on observability related to eigenvalues associated with the fan and spine structure surrounding null points or to the orientation of the spine. We find that approximately 31 % of nulls obtained from the PFSS model were observed in SDO/AIA images at one of the solar limbs. An observed null on the East solar limb had a 51.6 % chance of being observed on the West solar limb. Predicted null points going back to CR 1893 (March 1995) were also used for comparing radial and latitudinal distributions of nulls to previous work and to test for correlation of solar activity to the number of predicted nulls. Title: Temperature and Electron Density Diagnostics of a Candle-flame-shaped Flare Authors: Guidoni, S. E.; McKenzie, D. E.; Longcope, D. W.; Plowman, J. E.; Yoshimura, K. Bibcode: 2015ApJ...800...54G Altcode: Candle-flame-shaped flares are archetypical structures that provide indirect evidence of magnetic reconnection. A flare resembling Tsuneta's famous 1992 candle-flame flare occurred on 2011 January 28; we present its temperature and electron density diagnostics. This flare was observed with Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA), Hinode/X-Ray Telescope (XRT), and Solar Terrestrial Relations Observatory Ahead (STEREO-A)/Extreme Ultraviolet Imager, resulting in high-resolution, broad temperature coverage, and stereoscopic views of this iconic structure. The high-temperature images reveal a brightening that grows in size to form a tower-like structure at the top of the posteruption flare arcade, a feature that has been observed in other long-duration events. Despite the extensive work on the standard reconnection scenario, there is no complete agreement among models regarding the nature of this high-intensity elongated structure. Electron density maps reveal that reconnected loops that are successively connected at their tops to the tower develop a density asymmetry of about a factor of two between the two legs, giving the appearance of "half-loops." We calculate average temperatures with a new fast differential emission measure (DEM) method that uses SDO/AIA data and analyze the heating and cooling of salient features of the flare. Using STEREO observations, we show that the tower and the half-loop brightenings are not a line-of-sight projection effect of the type studied by Forbes & Acton. This conclusion opens the door for physics-based explanations of these puzzling, recurrent solar flare features, previously attributed to projection effects. We corroborate the results of our DEM analysis by comparing them with temperature analyses from Hinode/XRT. Title: The Space Public Outreach Team (SPOT): Adapting a successful outreach programme to a new region Authors: Williamson, K.; Jardins, A. D.; Grimberg, I.; Larson, S. L.; Key, J.; Larson, M. B.; Heatherly, S. A.; McKenzie, D.; Littenberg, T. B. Bibcode: 2014CAPJ...16....8W Altcode: The Space Public Outreach Team (SPOT) recruits and trains undergraduate ambassadors from all disciplines to deliver astronomy and space-science-themed interactive presentations. They deliver these presentations to primary and secondary schools and organisations across the state of Montana, USA. SPOT was started in 1996 by physics graduate students at Montana State University, USA, and it has grown to reach an average of 10 000 students per year for a low institutional cost of less than five dollars (four euros) per student. In the last year, the Montana SPOT model has been adopted in the state of West Virginia. The West Virginia SPOT programme also shows great potential, with eleven ambassadors trained to give two new feature presentations, reaching over 2600 students. In this paper, we describe how the Montana SPOT model works in practice and discuss how this model was adapted with new resources, and for a new audience, such that others may also adapt the programme to inspire space science interest for their own particular setting. We invite these groups to plug into the SPOT brand to broaden the impact of astronomy and space programmes and applications in their own region. Title: Characterizing Turbulent Flow in Quiescent Prominences Authors: Freed, M.; Wilburn, M.; McKenzie, D. E. Bibcode: 2014AGUFMSH11D..01F Altcode: Understanding the motion of plasma in quiescent prominences is important in determining how the magnetic field structure can become entangled to trigger eruptions. Hinode/Solar Optical Telescope (SOT) observations have already demonstrated the existence of convective flows and Kelvin-Helmholtz instabilities around the plume component inside these prominences. Our research uses the same observations to make quantitative measurements of the turbulent diffusive flows in these coronal structures. Fourier local correlation tracking (FLCT) is used to derive velocity fields from SOT observations of prominence plasma sheets. Analysis of these velocity fields in turn provides a measurement of the temporal and/or spatial length scales associated with the energy dissipation and diffusivity. Title: Thermal Structure and Dynamics in Supra-arcade Downflows and Flare Plasma Sheets Authors: Reeves, K.; Hanneman, W.; Freed, M.; McKenzie, D. E. Bibcode: 2014AGUFMSM44B..01R Altcode: During a long duration solar flare, a hot plasma sheet is commonly formed above the flare loops. Often produced within this sheet are down-flowing voids referred to as supra-arcade downflows, thought to be the products of a patchy reconnection process. Models differ on the question of whether the downflows should be hotter than the surrounding plasma or not. We use imaging data from Hinode/XRT and SDO/AIA to determine the thermal structure of the plasma sheet and downflows. We find that the temperatures of the plasma within the downflows are either roughly the same as or lower than the surrounding fan plasma. This result implies that a mechanism for forming the voids that involves a sunward directed hydrodynamic shock pattern combined with perpendicular magnetic shock is unlikely. Additionally, we use the high cadence AIA data to trace the velocity fields in these regions through the use of a local correlation tracking algorithm. Through these measurements, we can determine areas of diverging velocity fields, as well as velocity shear fields and correlate them with temperature changes in order to understand the heating mechanisms in the plasma sheet. This work is supported by under contract SP02H1701R from Lockheed-Martin to SAO, contract NNM07AB07C from NASA to SAO and NASA grant numbers NNX13AG54G and NNX14AD43G 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: Quiescent Reconnection Rate Between Emerging Active Regions and Preexisting Field, with Associated Heating: NOAA AR 11112 Authors: Tarr, Lucas A.; Longcope, Dana W.; McKenzie, David E.; Yoshimura, Keiji Bibcode: 2014SoPh..289.3331T Altcode: 2013arXiv1311.3705T; 2014SoPh..tmp....1T When magnetic flux emerges from beneath the photosphere, it displaces the preexisting field in the corona, and a current sheet generally forms at the boundary between the old and new magnetic domains. Reconnection in the current sheet relaxes this highly stressed configuration to a lower energy state. This scenario is most familiar and most often studied in flares, where the flux transfer is rapid. We present here a study of steady, quiescent flux transfer occurring at a rate three orders of magnitude lower than that in a large flare. In particular, we quantify the reconnection rate and the related energy release that occurred as the new polarity emerged to form NOAA Active Region 11112 (SOL16 October 2010T00:00:00L205C117) within a region of preexisting flux. A bright, low-lying kernel of coronal loops above the emerging polarity, observed with the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory and the X-ray Telescope onboard Hinode, originally showed magnetic connectivity only between regions of newly emerged flux when overlaid on magnetograms from the Helioseismic and Magnetic Imager. Over the course of several days, this bright kernel advanced into the preexisting flux. The advancement of an easily visible boundary into the old flux regions allows measuring the rate of reconnection between old and new magnetic domains. We compare the reconnection rate with the inferred heating of the coronal plasma. To our knowledge, this is the first measurement of steady, quiescent heating related to reconnection. We determined that the newly emerged flux reconnects at a fairly steady rate of 0.38×1016 Mx s−1 over two days, while the radiated power varies between (2 - 8)×1025 erg s−1 over the same time. We found that as much as 40 % of the total emerged flux at any given time may have reconnected. The total amounts of transferred flux (∼ 1×1021 Mx) and radiated energy (∼ 7.2×1030 ergs) are comparable to that of a large M- or small X-class flare, but are stretched out over 45 hours. 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: Advection of Magnetic Field Lines in Supra-Arcade Fan Structures Authors: Scott, Roger B.; Freed, Michael; McKenzie, David Eugene; Longcope, Dana Bibcode: 2014AAS...22432344S Altcode: Recent attempts to characterize the apparent motion of supra-arcade fan structures have revealed bulk velocity and displacement spectra that may give insights into the energy distribution in supra-arcade plasma sheets. In order to form a more complete picture of the energy balance in these structures it is important to understand the magnetic field on a similar scale. In this work we used velocity maps found through local correlation tracking (LCT) as source functions for a 2D, time-dependent, ideal induction equation. We began with an assumed initial configuration and then evolved the magnetic field in order to maintain the frozen-in condition. We then characterized the energy deposition into the field as well as the field strength spectrum and several other quantities of interest. It is our hope that this study will serve to improve our understanding of the interplay between the plasma and the magnetic field in the supra-arcade region. 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: Plasma Dynamics Above Solar Flare Soft X-Ray Loop Tops Authors: Doschek, G. A.; McKenzie, D. E.; Warren, H. P. Bibcode: 2014ApJ...788...26D Altcode: We measure non-thermal motions in flare loop tops and above the loop tops using profiles of highly ionized spectral lines of Fe XXIV and Fe XXIII formed at multimillion-degree temperatures. Non-thermal motions that may be due to turbulence or multiple flow regions along the line of sight are extracted from the line profiles. The non-thermal motions are measured for four flares seen at or close to the solar limb. The profile data are obtained using the Extreme-ultraviolet Imaging Spectrometer on the Hinode spacecraft. The multimillion-degree non-thermal motions are between 20 and 60 km s-1 and appear to increase with height above the loop tops. Motions determined from coronal lines (i.e., lines formed at about 1.5 MK) tend to be smaller. The multimillion-degree temperatures in the loop tops and above range from about 11 MK to 15 MK and also tend to increase with height above the bright X-ray-emitting loop tops. The non-thermal motions measured along the line of sight, as well as their apparent increase with height, are supported by Solar Dynamics Observatory Atmospheric Imaging Assembly measurements of turbulent velocities in the plane of the sky. Title: Empirical Study of Turbulent Diffusion in Flare Plasma Sheets Authors: McKenzie, David Eugene; Freed, Michael Bibcode: 2014AAS...22410401M Altcode: Velocity fields in the hot (>10 MK) plasma sheets above post-eruption flare arcades have the hallmarks of turbulent flow. Tracking and measuring these velocity fields enables empirical estimation of transport parameters, e.g. turbulent diffusivity, that are important for determining the spectrum of length scales present in the plasma sheet. These transport parameters thus help to set the rate of magnetic reconnection, and may help us to understand how reconnection can be triggered, accelerated, and prolonged in eruptive flares. In this work we show measurements, for the first time, of transport parameters in flare plasma sheets, enabled by high-resolution observations from SDO and local correlation tracking. Title: Findings from a Three Year Survey of Coronal Null Points Authors: Freed, Michael; Longcope, Dana; McKenzie, David Eugene Bibcode: 2014AAS...22432329F Altcode: We report the findings from a comprehensive coronal magnetic null point survey created by Potential Field Source Surface (PFSS) modeling & Solar Dynamic Observatory/Atmospheric Imaging Assembly (SDO/AIA) observations. Locations of magnetic null points in the corona were predicted from the PFSS model from Carrington Rotation 2098 to 2139 and manually compared to contrast enhanced SDO/AIA images in 171 angstroms. Statistical results will be presented that illustrate the characteristics associated with the observed and predicted null points. These characteristics include the radial & latitudinal distribution; eigenvalues associated with null point structure; and the effect spine orientation has on observability. Title: Non-thermal Motions in and Above Flare Loop Tops Measured by the Extreme-ultraviolet Imaging Spectrometer (EIS) on Hinode Authors: Doschek, George A.; McKenzie, David Eugene; Warren, Harry P Bibcode: 2014AAS...22411105D Altcode: The plasma volume above the soft X-ray emitting loop tops is of particular interest for studying the formation of flare loops. We present EIS observations of non-thermal motions (turbulence) determined from spectral line profiles of Fe XXIII and Fe XXIV ions for three well-observed flares near the solar limb. We compare the non-thermal motions at temperatures near 10 MK with the motions along the same lines-of-sight determined from lines of coronal ions such as Fe XII, Fe XIV, and Fe XV formed at 1-2 MK. The take-away is that the non-thermal motions obtained from Fe XXIII and Fe XXIV lines increase with height towards the reconnection region, up to speeds of about 50-60 km/s for the largest heights that we can observe. The implication is that considerable plasma heating occurs outside the reconnection region. In addition, we discuss the implications of results obtained for flares from earlier X-ray Yohkoh observations of line profiles of Fe XXV and Ca XIX on the current results from EIS and AIA. Fe XXV is formed at significantly higher temperatures than any strong flare EUV spectral line observed by EIS or by imaging telescopes such as AIA or TRACE. This work is supported by NASA grants. 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: Peristaltic Pumping near Post-coronal Mass Ejection Supra-arcade Current Sheets Authors: Scott, Roger B.; Longcope, Dana W.; McKenzie, David E. Bibcode: 2013ApJ...776...54S Altcode: 2013arXiv1308.5026S Temperature and density measurements near supra-arcade current sheets suggest that plasma on unreconnected field lines may experience some degree of "pre-heating" and "pre-densification" prior to reconnection. Models of patchy reconnection allow for heating and acceleration of plasma along reconnected field lines but do not offer a mechanism for transport of thermal energy across field lines. Here, we present a model in which a reconnected flux tube retracts, deforming the surrounding layer of unreconnected field. The deformation creates constrictions that act as peristaltic pumps, driving plasma flow along affected field lines. Under certain circumstances, these flows lead to shocks that can extend far out into the unreconnected field, altering the plasma properties in the affected region. These findings have direct implications for observations in the solar corona, particularly in regard to such phenomena as high temperatures near current sheets in eruptive solar flares and wakes seen in the form of descending regions of density depletion or supra-arcade downflows. Title: On the Chromospheric Evaporation Observed during an X1.4 Flare of 12-July, 2012 Authors: Takeda, Aki; Yoshimura, K.; McKenzie, D. E. Bibcode: 2013SPD....44...87T Altcode: A GOES-class X1.4 flare from the NOAA active region 11520 was observed with Hinode/XRT on 12-July, 2012. This region showed sigmoidal structure, which was developed between a group of two major positive-polarity sunspots and an area of small scattered sunspots with negative-polarity. In the course of this flare, a long flare ribbon (typically observed in the light of 304A or H-alpha) was formed on the negative side of the polarity inversion line, while its positive counter part appeared to be concentrated in a brightening around one of the major sunspots. Two notable phenomena were observed associated with this event: (1) Soft X-ray brightening was observed at the foot points of the post flare loops which started to grow ~30 minutes later. (2) Strong and narrow extension of dark lanes (or ejections of low-density plasma) were observed from the both ends of the sigmoid loops at the maximum phase of the flare. As neither of these phenomena are previously reported, proper description and explanation need to be given.Abstract (2,250 Maximum Characters): A GOES-class X1.4 flare from the NOAA active region 11520 was observed with Hinode/XRT on 12-July, 2012. This region showed sigmoidal structure, which was developed between a group of two major positive-polarity sunspots and an area of small scattered sunspots with negative-polarity. In the course of this flare, a long flare ribbon (typically observed in the light of 304A or H-alpha) was formed on the negative side of the polarity inversion line, while its positive counter part appeared to be concentrated in a brightening around one of the major sunspots. Two notable phenomena were observed associated with this event: (1) Soft X-ray brightening was observed at the foot points of the post flare loops which started to grow ~30 minutes later. (2) Strong and narrow extension of dark lanes (or ejections of low-density plasma) were observed from the both ends of the sigmoid loops at the maximum phase of the flare. As neither of these phenomena are previously reported, proper description and explanation need to be given. Title: Multi--Instrument Estimation Of The Non--Flaring Heating And Reconnection Rates Of Emerging Active Region NOAA AR11112 Authors: Tarr, Lucas; Longcope, D.; McKenzie, D. E.; Yoshimura, K. Bibcode: 2013SPD....4430202T Altcode: In NOAA Active Region 11112, a small bipole emerges into an area of preexisting, unipolar flux. The bright, low lying kernel of coronal loops above the emerging field, observed with AIA and XRT, originally show magnetic connectivity only between regions of newly emerged flux when overlaid on HMI magnetograms. Over the course of several days, this bright kernel advances into the preexisting flux. The advancement of this easily visible boundary into the old flux regions over time provides a quantifiable rate of reconnection between old and new magnetic domains. We compare the reconnection rate to the inferred heating of the coronal plasma. To our knowledge, this is the first measurement of steady, quiescent heating related to reconnection. While AR11112 does produce an M3.0 flare on Oct 16th, 2010, the implied reconnection we focus on here predates the flare by several days, and does not result in any observable flaring active of its own, such as increases in the GOES light curve, chromospheric flare ribbons, or post--flare loops. We determine that the newly emerged flux reconnects at a fairly steady average rate of 3.5e16 Mx/s over two days, while the radiated power varies between 2-8e25erg/s over the same time. Title: Turbulence in the Flare Reconnection Region Authors: Doschek, George A.; McKenzie, D. E.; Warren, H. Bibcode: 2013SPD....4430401D Altcode: The physical conditions such as temperature, density, and dynamical properties in the flare reconnection region, located above the bright soft X-ray loops, are basically not known although there have been measurements of non-thermal hard X-ray emission properties by RHESSI and earlier by HXT on Yohkoh. The advent of Hinode and the Solar Dynamics Observatory (SDO) spatially resolved observations, however, has changed this and it is now possible to measure in more detail some of the properties of the reconnection region. AIA imagery on SDO and the Extreme-ultraviolet Imaging Spectrometer (EIS) and X-ray Telescope (XRT) on Hinode allow values of non-thermal motions or turbulence in the reconnection region to be determined. Turbulence is predicted by theoretical models of magnetic reconnection in flares (e.g., see Liu et al. 2008, ApJ, 676, 704) and has long been inferred spectroscopically from non-thermal broadening of flare emission lines. Studies with Hinode/XRT and SDO/AIA demonstrate that two-dimensional investigations of flare velocity fields can be made, by imaging the plasma sheets above post-CME flare arcades. These measurements are made possible through the use of local correlation tracking (LCT), as shown by McKenzie (2013), ApJ, 766, 39, and reveal signatures of turbulence, including temporally and spatially varying vorticity. For some flares the AIA and XRT results can be combined with Doppler measurements of turbulence obtained with EIS. EIS data consist of raster scans that include the reconnection region for flares on the limb or near the limb. A set of spectral lines are observed that cover temperatures from 0.25 MK up to ~20 MK. A temperature in the reconnection region is calculated from the Fe XXIII/Fe XXIV line ratio and the thermal Doppler and instrumental widths are subtracted from the total line widths. The remainder is non-thermal motions or turbulence. We will present coordinated analyses of EIS and AIA observations of plasma sheets in post-CME flares, and demonstrate that the turbulent speeds found by LCT are about the same magnitude as those derived from EIS spectral line profiles obtained in the same or nearby locations. Title: Thermal Structure of Supra-arcade Downflows and Flare Plasma Sheets Authors: Reeves, Kathy; Hanneman, W.; McKenzie, D. E. Bibcode: 2013SPD....4430404R Altcode: We use Hinode/XRT and SDO/AIA data to determine the thermal structure of supra arcade downflows as well as the surrounding plasma sheet. Using the multiple filters and broad temperature coverage provided by the combination of these two telescopes, we construct DEMs in the fan plasma and the supra-arcade downflows. Several models have indicated that the plasma inside the supra-arcade downflows should be significantly hotter than the surrounding plasma, but about an order of magnitude less dense. However, we find that the temperatures of the plasma within the downflows are either roughly the same as or lower than the surrounding fan plasma, with only one exception. We also compare the thermal structure of the supra-arcade plasma with calculations of the divergence of the velocity of the plasma in the sheet in order to locate evidence of adiabatic cooling and heating. The velocity fields are calculated using local correlation tracking applied to high-resolution sequences of AIA images. We find preliminary evidence that diverging velocity fields are cooler and less dense than the surrounding plasma. Title: Calibration of Hinode/XRT for Coalignment II: Comparison of Three Different Methods Authors: Yoshimura, Keiji; McKenzie, D. E. Bibcode: 2013SPD....44...98Y Altcode: The coalignment of solar images from various observational instruments is an important step to study solar features/phenomena when using data acquired from multiple telescopes or wavelengths. We have been working on the calibration of XRT/Hinode to get coalignment parameters, i.e., plate scale, roll angle in the plane of the sky, and pointing information. We are developing a table of the parameters for every single XRT image, so that all users of XRT data can easily utilize our results for their coalignment. There are three different approaches to get the XRT pointing information: (1) applying the cross correlation technique to the X-ray images from XRT and the EUV images from AIA/SDO (2) combination of solar limb fitting and cross correlation between XRT full and partial disk images (3) using outputs from the sun sensor (Ultra Fine Sun Sensor, UFSS) on-board Hinode We discuss the advantages and disadvantages of each method and estimate the errors through the cross comparison. In preparing our table of coalignment coefficients we combine the strengths of each of these methods to provide the most reliable resource. We also discuss the accuracy of the plate scale of X-ray data from XRT, which can be derived from the comparison between XRT and AIA images.Abstract (2,250 Maximum Characters): The coalignment of solar images from various observational instruments is an important step to study solar features/phenomena when using data acquired from multiple telescopes or wavelengths. We have been working on the calibration of XRT/Hinode to get coalignment parameters, i.e., plate scale, roll angle in the plane of the sky, and pointing information. We are developing a table of the parameters for every single XRT image, so that all users of XRT data can easily utilize our results for their coalignment. There are three different approaches to get the XRT pointing information: (1) applying the cross correlation technique to the X-ray images from XRT and the EUV images from AIA/SDO (2) combination of solar limb fitting and cross correlation between XRT full and partial disk images (3) using outputs from the sun sensor (Ultra Fine Sun Sensor, UFSS) on-board Hinode We discuss the advantages and disadvantages of each method and estimate the errors through the cross comparison. In preparing our table of coalignment coefficients we combine the strengths of each of these methods to provide the most reliable resource. We also discuss the accuracy of the plate scale of X-ray data from XRT, which can be derived from the comparison between XRT and AIA images. Title: Peristaltic Pumping near Post-CME Supra-Arcade Current Sheets Authors: Scott, Roger B.; Longcope, D.; McKenzie, D. E. Bibcode: 2013SPD....4430402S Altcode: Measurements of temperature and density near supra-arcade current sheets suggest that plasma on unreconnected field lines may experience some degree of “pre-heating” and “pre-densification” prior to their reconnection. Models of patchy reconnection allow for heating and acceleration of plasma along reconnected field lines but do not offer a mechanism for transport of energy and momentum across field lines. Here we present a model in which a reconnected flux tube retracts, deforming the surrounding layer of unreconnected field. The deformation creates constrictions that act as peristaltic pumps, driving plasma flow along affected field lines. Under certain circumstances these flows lead to shocks that can extend far out into the unreconnected field, altering the plasma properties in the affected region. These findings have direct implications for observations in the solar corona, particularly in regard to such phenomena as wakes seen behind supra-arcade downflows and high temperatures near current sheets in eruptive solar flares. This work was supported by NASA, the NSF and the DOE. Title: Survey of Coronal Null Points with SDO/AIA & WSO Authors: Freed, Michael; McKenzie, D. E.; Longcope, D. Bibcode: 2013SPD....44...21F Altcode: Magnetic fields in the corona can be approximated by using PFSS (Potential Field Source Surface) model in conjunction with magnetogram measurements of the photosphere. This approach is incorporated here to find locations of magnetic null points in the solar corona. Observations from WSO (Wilcox Solar Observatory) provide the necessary harmonic coefficients for a PFSS model. We located all magnetic null points in the PFSS model going back to Carrington Rotation 2098. The time and location where they cross the West limb is compared to high resolution observations made by SDO/AIA. Variations in predicted and observed null point locations, and estimates of the duration of each null, will be examined. This work will provide a catalog of coronal nulls observed by SDO that can be examined further for interesting dynamical behavior or variations in neighboring plasma. 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: Turbulent Dynamics in Solar Flare Sheet Structures Measured with Local Correlation Tracking Authors: McKenzie, D. E. Bibcode: 2013ApJ...766...39M Altcode: High-resolution observations of the Sun's corona in extreme ultraviolet and soft X-rays have revealed a new world of complexity in the sheet-like structures connecting coronal mass ejections (CMEs) to the post-eruption flare arcades. This article presents initial findings from an exploration of dynamic flows in two flares observed with Hinode/XRT and SDO/AIA. The flows are observed in the hot (gsim 10 MK) plasma above the post-eruption arcades and measured with local correlation tracking. The observations demonstrate significant shears in velocity, giving the appearance of vortices and stagnations. Plasma diagnostics indicate that the plasma β exceeds unity in at least one of the studied events, suggesting that the coronal magnetic fields may be significantly affected by the turbulent flows. Although reconnection models of eruptive flares tend to predict a macroscopic current sheet in the region between the CME and the flare arcade, it is not yet clear whether the observed sheet-like structures are identifiable as the current sheets or "thermal halos" surrounding the current sheets. Regardless, the relationship between the turbulent motions and the embedded magnetic field is likely to be complicated, involving dynamic fluid processes that produce small length scales in the current sheet. Such processes may be crucial for triggering, accelerating, and/or prolonging reconnection in the corona. Title: Imaging Turbulent Dynamics in Post-CME Current Sheet Structures Authors: McKenzie, David E. Bibcode: 2013enss.confE..38M Altcode: Turbulence in current sheets is hypothesized to produce cascades from large to small length scales, both in terms of tangled or "stochastic" magnetic fields and in the creation of "micro-current sheets". The resulting conditions are likely to have profound effects on the rate of magnetic reconnection. Whereas current sheet turbulence has historically been inferred from spectroscopic measurements of, say, nonthermal broadening, recent developments in high-resolution EUV and X-ray imaging have brought turbulence into a new light, revealing a new world of complex dynamics in the sheet-like structures connecting CMEs to post-eruption flare arcades. The image sequences demonstrate significant shears in velocity, giving the appearance of vortices and stagnations; and plasma diagnostics indicate that the plasma beta can exceed unity, suggesting that the coronal magnetic fields are significantly affected by turbulent fluid processes which produce small length scales in the current sheet. Observational characterization of the turbulent conditions will help to guide modeling efforts of post-CME current sheets, particularly in regards to cascades from CME length scales to much smaller sizes. I will present findings from an exploration of the velocity fields in the supra-arcade sheet structures, as imaged by SDO/AIA and measured with local correlation tracking. Title: Success of Solar Dynamics Observatory (SDO) Education & Public Outreach (E/PO) in Montana Authors: Freed, M. S.; Lowder, S. C.; McKenzie, D. E. Bibcode: 2013enss.confE..66F Altcode: The Space Public Outreach Team (SPOT) program at Montana State University (MSU) is the main component of SDO E/PO efforts in Montana. SPOT brings energetic presentations of recent science & NASA missions to students in primary & secondary schools. Presenters are university undergraduates that visit a diverse group of K-12 students from both rural & urban areas of Montana. This program is extremely cost effective, a valuable service-learning experience for undergraduates at MSU and has repeatedly received praise from both teachers and students. A complementary effort for training schoolteachers entitled NASA Education Activity Training (NEAT) is also employed. NEAT illustrates to teachers inexpensive and highly effective methods for demonstrating difficult science concepts to their students. We will highlight the successes and lessons learned from SPOT & NEAT, so that other E/PO programs can use it as a template to further science literacy in our nation's schools. Title: Temperature and Electron Density Diagnostics of a Candle-Flame Shaped Flare. Asymmetric Reconnection Evidence Authors: Guidoni, Silvina E.; McKenzie, David E.; Longcope, Dana W.; Plowman, Joseph E.; Yoshimura, Keiji Bibcode: 2013enss.confE..62G Altcode: Candle-flame shaped flares are archetypical structures that represent indirect evidence of magnetic reconnection. For long-lived events, most of their observed features can be explained with the classic magnetic reconnection model of solar flares, the CSHKP model. A flare resembling 1992 Tsuneta's famous candle-flame flare occurred on January 28 2011; we present its temperature and electron density diagnostics. This flare was observed with Hinode/XRT, SDO/AIA, and STEREO (A)/EUVI, resulting in high resolution, broad temperature coverage, and stereoscopic views of this iconic structure. Our XRT filter-ratio temperature and density maps corroborate the general reconnection scenario. The high temperature images reveal a brightening that grows in size to form a tower-like structure at the top of the post-flare arcade, a feature that has been observed in other long duration events. This tower is a localized density increase, as shown by our XRT electron density maps. Despite the extensive work on the standard reconnection scenario, there is no complete agreement among models regarding the nature of this tower-like structure. The XRT maps also reveal that reconnected loops that are successively connected at their tops to this tower develop a density increase in one of their legs that can reach over 2 times the density value of the other leg, giving the appearance of ``half-loops''. Their density is nevertheless still lower than at the tower. These jumps in density last longer than several acoustic transit times along the loops. We use STEREO images to show that the half-loop brightening is not a line-of- sight projection effect of the type suggested by Forbes and Acton (1996). This would indicate that asymmetric reconnection took place between loops originally belonging to systems with different magnetic field strengths, densities, and temperatures. We hypothesize that the heat generated by reconnection's slow shocks is then transferred to each leg of the loop at different rates. Therefore, the increase in electron density due to chromospheric evaporation is different in each leg. Thermal pressure balance between the legs is prevented by shocked plasma at the top of the loops. We also present preliminary results comparing a new fast DEM method that uses SDO/AIA data with the XRT filter ratio method. Both methods complement each other, they agree at the overlap between their instruments' temperature response functions (3-12 MK) while the SDO/AIA method works well at lower temperatures and the XRT one at higher temperatures. Title: Shrinking Loops Observations for the 2008 April 9 Flare Authors: Savage, S. L.; McKenzie, D. E.; Reeves, K. K.; Forbes, T. G. Bibcode: 2012ASPC..454..295S Altcode: Supra-arcade downflows (SADs) have been observed with Yohkoh/SXT (soft X-rays (SXR)), TRACE (extreme ultra-violet (EUV)), SoHO/LASCO (white light), SoHO/SUMER (EUV spectra), and Hinode/XRT (SXR). Characteristics such as low emissivity and trajectories which slow as they reach the top of the arcade are consistent with post-reconnection magnetic flux tubes. The magnetic flux within the tubes provides pressure against filling with plasma. As with the standard model of reconnection, the tubes retract from a reconnection site high in the corona until they reach a more potential magnetic configuration. Viewed from a perpendicular angle, SADs should appear as shrinking loops rather than downflowing voids. We will present observations of supra-arcade downflowing loops (SADLs) and show that their speeds and decelerations are consistent with those determined for SADs. 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: Experimental Flat-Field for Correction of XRT Contamination Spots Authors: McKenzie, D. E.; Fox, J. L.; Kankelborg, C. Bibcode: 2012ASPC..454..453M Altcode: Beginning in mid-2007, the XRT images are marred by dark spots due to beads of congealed contaminant. While programs are available for improving the cosmetic appearance of the images, no method has yet been demonstrated for a quantitative correction. We have employed a flatfielding method developed for MSU's MOSES sounding rocket payload, in an attempt to restore capabilities for quantitative photometry in the affected pixels. Initial results are encouraging; characterization of the uncertainties in the photometric correction are ongoing. We report on the degree to which this flatfielding attempt has been successful. Title: Low-altitude Reconnection Inflow-Outflow Observations during a 2010 November 3 Solar Eruption Authors: Savage, Sabrina L.; Holman, Gordon; Reeves, Katharine K.; Seaton, Daniel B.; McKenzie, David E.; Su, Yang Bibcode: 2012ApJ...754...13S Altcode: 2011arXiv1111.1945S For a solar flare occurring on 2010 November 3, we present observations using several SDO/AIA extreme-ultraviolet (EUV) passbands of an erupting flux rope followed by inflows sweeping into a current sheet region. The inflows are soon followed by outflows appearing to originate from near the termination point of the inflowing motion—an observation in line with standard magnetic reconnection models. We measure average inflow plane-of-sky speeds to range from ~150 to 690 km s-1 with the initial, high-temperature inflows being the fastest. Using the inflow speeds and a range of Alfvén speeds, we estimate the Alfvénic Mach number which appears to decrease with time. We also provide inflow and outflow times with respect to RHESSI count rates and find that the fast, high-temperature inflows occur simultaneously with a peak in the RHESSI thermal light curve. Five candidate inflow-outflow pairs are identified with no more than a minute delay between detections. The inflow speeds of these pairs are measured to be ~102 km s-1 with outflow speeds ranging from ~102 to 103 km s-1—indicating acceleration during the reconnection process. The fastest of these outflows are in the form of apparently traveling density enhancements along the legs of the loops rather than the loop apexes themselves. These flows could possibly either be accelerated plasma, shocks, or waves prompted by reconnection. The measurements presented here show an order of magnitude difference between the retraction speeds of the loops and the speed of the density enhancements within the loops—presumably exiting the reconnection site. Title: Dynamic Fluid Flows in Supra-Arcade Current Sheets/Thermal Halos Authors: McKenzie, David E. Bibcode: 2012shin.confE..65M Altcode: High-resolution observations in EUV and X-rays have revealed a new world of complexity in the sheet-like structures connecting CMEs to the post-eruption flare arcades. The observations demonstrate vortices, shears in velocity, and -- for perhaps the first time -- fragmentation of supra-arcade downflows. Although it is not yet clear whether the emission is produced in the current sheet itself or in a 'thermal halo' surrounding the current sheet, the relationship between the motions and the magnetic field associated with the current sheet is, perforce, complicated. In particular, the vortical motions must significantly contort the embedded magnetic field; and the fragmentation of supra-arcade downflows suggests the presence of fluid processes that contribute to the reduction of spatial scales in the current sheet/thermal halo. Such processes may be crucial for triggering, accelerating, and/or prolonging reconnection.Given that the plasma conditions in the supra-arcade region are still imperfectly known, such that low densities and long mean free paths complicate our understanding of the fluidity of the flows, it is imperative that we make the most of the opportunity provided by SDO and Hinode to chart this dynamic regime. I will present findings from an exploration of the velocity fields in the supra-arcade current sheet/thermal halo, as imaged by SDO/AIA and Hinode/XRT. Title: Nozzle Driven Shocks in Post-CME Plasma Authors: Scott, Roger B.; Longcope, D. W.; McKenzie, D. E. Bibcode: 2012AAS...22020407S Altcode: Models of patchy reconnection allow for heating and acceleration of plasma along reconnected field lines but do not offer a mechanism for transport of energy and momentum across field lines. Here we present a simple 2D model in which a localized region of reconnected flux creates an apparent constriction in the surrounding layer of unreconnected field. The moving constriction acts as a de Laval nozzle and ultimately leads to shocks which can extend out to several times the diameter of the flux tube, altering the density and temperature of the plasma in that region. These findings have direct implications for observations in the solar corona, particularly in regard to such phenomena as wakes seen behind supra-arcade downflows and high temperatures in post-CME current sheets. This work was supported by a joint grant from the NSF and DOE. Title: Complex Dynamic Flows in Solar Flare Sheet Structures Authors: McKenzie, David Eugene; Reeves, K. K.; Savage, S. L. Bibcode: 2012AAS...22020422M Altcode: Observations of high-energy emission from solar flares often reveal the presence of large sheet-like structures, sometimes extending over a space comparable to the Sun's radius. Given that these structures are found between a departing coronal mass ejection and the post-eruption flare arcade, it is natural to associate the structure with a current sheet; though the relationship is unclear. Moreover, recent high-resolution observations have begun to reveal that the motions in this region are highly complex, including reconnection outflows, oscillations, and apparent wakes and eddies. We present a detailed first look at the complicated dynamics within this supra-arcade plasma, and consider implications for the interrelationship between the plasma and its embedded magnetic field.

This work is supported by NASA under contract SP02H3901R from Lockheed-Martin to MSU (DMcK), contract SP02H1701R from Lockheed-Martin to SAO (KKR), and contract NNM07AB07C with the Harvard-Smithsonian Astrophysical Observatory. SLS is supported via a NASA/GSFC NPP appointment administered by Oak Ridge Associated Universities and under the mentorship of G. Holman. Title: Current Sheet and Reconnection Inflow-Outflow Observations During Solar Eruptions Authors: Savage, S. L.; Holman, G.; Reeves, K. K.; Seaton, D. B.; McKenzie, D. E.; Su, Y. Bibcode: 2012ASPC..456..169S Altcode: Magnetic reconnection is widely accepted as being associated with energy release during solar flares; however, observations of it have been indirect and/or incomplete. Using the suite of instruments available spanning wavelength space, we provide observations and measurements of both the inputs and outputs predicted from reconnection in the form of inflows preceding outflows (i.e. supra-arcade downflows, supra-arcade downflowing loops, upflows, and disconnection events). We also present evidence for current sheets through which reconnection is expected to occur and discuss current sheet motion during flare progression. 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: A Multi-Wavelength Statistical Study of Supra-Arcade Downflows Authors: Savage, S. L.; McKenzie, D. E. Bibcode: 2012ASPC..455..305S Altcode: 2012arXiv1201.5246S Sunward-flowing voids above post-coronal mass ejection flare arcades, also known as supra-arcade downflows (SADs), have characteristics consistent with post-reconnection magnetic flux tube cross-sections. Applying semi-automatic detection and analysis software to a large sample of flares using several instruments (e.g., Hinode/XRT, Yohkoh/SXT, TRACE, and SOHO/LASCO), we have estimated parameters such as speeds, sizes, heights, magnetic flux, and relaxation energy associated with SADs, which we interpret as reconnection outflows. We also present speed and height measurements of shrinking loops in comparison to the SAD observations. We briefly discuss these measurements and what impact they have on reconnection models. 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: Calibration of Hinode/XRT for Coalignment Authors: Yoshimura, Keiji; McKenzie, D. E. Bibcode: 2012AAS...22020129Y Altcode: When someone tries to understand some phenomena on the Sun, a comparison between the data from different types of observation for the same target would be a good way. Fortunately various kinds of data, from satellite and ground-based telescopes, are available for us these days. While it is necessary to coalign the data from different instruments for the analysis, it is often difficult to achieve sufficient accuracy with a simple method. For the coalignment, we need to know the plate scales, rotation angle in the plane of the sky, and pointing information for the images, at least. To augment the information provided by the Hinode/XRT FITS headers, we are calibrating the XRT data as accurately as possible by means of limb fitting and cross correlation techniques, yielding a table of coalignment parameters for every single XRT image. The final goal of the project is to provide an easy and precise

coalignment method to users of the XRT data. We also do a cross calibration between XRT and AIA on-board SDO. Since we can find many similar structures in some of the images from both of the instruments, a cross correlation technique is useful for improving the accuracy of the coalignment. Our parameter tables will include the results from the cross calibration too. Title: Flare Half-Loops: What Are They? Authors: McKenzie, David Eugene; Guidoni, S. E.; Longcope, D. W.; Yoshimura, K. Bibcode: 2012AAS...22032201M Altcode: The M1.4 flare of 28 January 2011 has a remarkable resemblance to the famous "Tsuneta candle-flame" flare of 1992. It was observed with Hinode/XRT, SDO/AIA, and STEREO (A)/EUVI, resulting in higher resolution, greater temperature coverage, and stereoscopic views of this iconic structure. The high temperature images reveal a brightening that grows in size to form a tower-like structure at the top of the arcade. They also show that loops which are successively connected to this tower develop a density increase in one of their legs that can exceed twice the density of the other leg, giving the appearance of "half loops". These jumps in density last for an extended period of time. On the other hand, XRT filter ratios suggest that temperature is approximately uniform along the entire loop. XRT filter-ratio density maps corroborate that the brighter legs have higher density than the fainter halves. The tower is associated with a localized density increase, with even higher densities than either leg of the loop. This spatial variation of density may correspond to a shock at the top of the loops. We use STEREO images to show that the half loop brightening is not a line-of-sight projection effect of the type suggested by Forbes & Acton. This work is supported under contract SP02H3901R from Lockheed-Martin to MSU, and under contract NNM07AB07C with the Harvard-Smithsonian Astrophysical Observatory. Title: NASA Education Activity Training (NEAT): Professional Development for Montana K-12 Teachers Authors: Williamson, Kathryn; McKenzie, D.; Des Jardins, A.; Key, J.; Kanode, C.; Willoughby, S. Bibcode: 2012AAS...22010805W Altcode: Piloted during the 2011-2012 academic year, the NASA Education Activity Training (NEAT) teacher workshop program has introduced five solar astronomy and space weather activities to over forty Montana K-12 teachers. Because many Montana schools are geographically isolated (40% of Montana students live more than 50 miles from a city) and/or serve traditionally underrepresented groups (primarily Native Americans), professional development for teachers can be costly and time consuming. However, with funding shared by the Atmospheric Imaging Assembly EPO team and the Montana Space Grant Consortium, graduate student specialists are able to host the two-hour NEAT workshops on-site at the schools free of charge, and participating teachers earn two continuing education credits. Leveraging the existing catalogue of research-based NASA activities, the featured NEAT activities were chosen for their ease-of-use and applicability to Montana science standards. These include three advanced activities for older students, such as a paper plate activity for the June 5th, 2012 Transit of Venus, Kinesthetic Astronomy, and the Herschel Infrared experiment, along with two simpler activities for the younger students, such as Solar Cookies and the Electromagnetic War card game. Feedback surveys show that NEAT workshop participants were interested and engaged in the activities and planned on using the activities in their classrooms. With such positive responses, the NEAT program has been a huge success and can serve as a model for other institutions looking to increase their space public outreach and education. 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: Thermal Structure of Supra-Arcade Plasma in Two Solar Flares Authors: Reeves, Kathy; Savage, S. L.; McKenzie, D. E.; Weber, M. A. Bibcode: 2012AAS...22020405R Altcode: In this work, we use Hinode/XRT and SDO/AIA data to determine the thermal structure of supra-arcade plasma in two solar flares. The first flare is a M1.2 flare that occurred on November 5, 2010 on the east limb. This flare was one of a series of flares from AR 11121, published in Reeves & Golub (2011). The second flare is an X1.7 flare that occurred on January 27, 2012 on the west limb. This flare exhibits visible supra-arcade downflows (SADs), where the November 2010 flare does not. For these two flares we combine XRT and AIA data to calculate DEMs of each pixel in the supra-arcade plasma, giving insight into the temperature and density structures in the fan of plasma above the post-flare arcade. We find in each case that the supra-arcade plasma is around 10 MK, and there is a marked decrease in the emission measure in the SADs. We also compare the DEMs calculated with the combined AIA/XRT dataset to those calculated using AIA alone. Title: Re-interpretation Of Supra-arcade Downflows In Solar Flares Authors: Savage, Sabrina; McKenzie, D. E.; Reeves, K. K. Bibcode: 2012AAS...22051602S Altcode: Following the eruption of a filament from a flaring active region, sunward-flowing voids are often seen above developing post-eruption arcades. First discovered using the soft X-ray telescope aboard Yohkoh, these supra-arcade downflows (SADs) are now an expected observation of extreme ultra-violet and soft X-ray coronal imagers and spectrographs (e.g, TRACE, SOHO/SUMER, Hinode/XRT, SDO/AIA). Observations made prior to the operation of AIA suggested that these plasma voids (which are seen in contrast to bright, high-temperature plasma associated with current sheets) are the cross-sections of evacuated flux tubes retracting from reconnection sites high in the corona. The high temperature imaging afforded by AIA's 131, 94, and 193 Angstrom channels coupled with the fast temporal cadence allows for unprecedented scrutiny of the voids. For a flare occurring on 2011 October 22, we provide evidence suggesting that SADs, instead of being the cross-sections of relatively large, evacuated flux tubes, are actually wakes (i.e., trailing regions of low density) created by the retraction of much thinner tubes. This re-interpretation is a significant shift in the fundamental understanding of SADs, as the features once thought to be identifiable as the shrinking loops themselves now appear to be "side effects" of the passage of the loops through the supra-arcade plasma. In light of the fact that previous measurements have attributed to the shrinking loops characteristics that may instead belong to their wakes, we discuss the implications of this new interpretation on previous parameter estimations and on reconnection theory. 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: Post-Flare Half-Loops: What are They? Authors: Guidoni, Silvina E.; McKenzie, David E.; Longcope, Dana W. Bibcode: 2012decs.confE..12G Altcode: The M1.4 flare of Jan 28, 2011 has a remarkable resemblance to the famous Tsuneta flare of 1992. It was observed with Hinode/XRT, SDO/AIA, and STEREO (A)/EUVI, giving us higher resolution, greater temperature coverage, and stereoscopic views of this iconic structure. The high temperature images reveal a brightening that grows in size to form a tower-like structure at the top of the post-flare arcade. They also show that loops that are successively connected to this tower develop a density increase in one of their legs that can reach 4 times the density value of the other leg, giving the appearance of "half loops". These jumps in density last for an extended period of time. On the other hand, XRT filter ratios suggest that temperature is approximately uniform along the entire loop. XRT filter-ratio density maps corroborate that the brighter legs have higher density than the rest of the loop. The tower is a localized density increase at even higher densities than the brighter side of the loop. This may correspond to a shock at the top of the loops. We use STEREO images to show that the half loop brightening is not a line-of-sight projection effect of the type suggested by Forbes & Acton. Title: Re-interpretation of Supra-arcade Downflows in Solar Flares Authors: Savage, Sabrina L.; McKenzie, David E.; Reeves, Katharine K. Bibcode: 2012ApJ...747L..40S Altcode: 2011arXiv1112.3088S Following the eruption of a filament from a flaring active region, sunward-flowing voids are often seen above developing post-eruption arcades. First discovered using the soft X-ray telescope aboard Yohkoh, these supra-arcade downflows (SADs) are now an expected observation of extreme ultra-violet and soft X-ray coronal imagers and spectrographs (e.g, TRACE, SOHO/SUMER, Hinode/XRT, SDO/AIA). Observations made prior to the operation of AIA suggested that these plasma voids (which are seen in contrast to bright, high-temperature plasma associated with current sheets) are the cross-sections of evacuated flux tubes retracting from reconnection sites high in the corona. The high temperature imaging afforded by AIA's 131, 94, and 193 Å channels coupled with the fast temporal cadence allows for unprecedented scrutiny of the voids. For a flare occurring on 2011 October 22, we provide evidence suggesting that SADs, instead of being the cross-sections of relatively large, evacuated flux tubes, are actually wakes (i.e., trailing regions of low density) created by the retraction of much thinner tubes. This re-interpretation is a significant shift in the fundamental understanding of SADs, as the features once thought to be identifiable as the shrinking loops themselves now appear to be "side effects" of the passage of the loops through the supra-arcade plasma. In light of the fact that previous measurements have attributed to the shrinking loops characteristics that may instead belong to their wakes, we discuss the implications of this new interpretation on previous parameter estimations and on reconnection theory. Title: SDO Education and Public Outreach Authors: Wawro, M.; Scherrer, D.; McKenzie, D.; Kellagher, E.; Van Norden, W.; Durscher, R.; Winter, H.; Myers, D. Bibcode: 2012decs.confE..70W Altcode: With the huge inflow of SDO data, the SDO E/PO team has focused its efforts on finding solutions that put SDO data into the hands of the public including classrooms and informal education programs. After summarizing the highlights of our post-launch activities, we will reintroduce the SDO E/PO team, describe current efforts aimed at increasing the number of people exposed to SDO data, and and the quality of programs using data, as well as start a dialog around how we as a community would like to move forward. Title: EUV Analysis of a Quasi-static Coronal Loop Structure Authors: Scott, J. T.; Martens, P. C. H.; McKenzie, D. E. Bibcode: 2012SoPh..276..113S Altcode: 2011arXiv1110.5560S Decaying active region 10942 is investigated from 4:00 - 16:00 UT on 24 February 2007 using a suite of EUV observing instruments. Results from Hinode/EIS, STEREO and TRACE show that, although the active region has decayed and no sunspot is present, the physical mechanisms that produce distinguishable loop structures, spectral line broadening, and plasma flows still occur. A coronal loop that appears as a blue-shifted structure in Doppler maps is apparent in intensity images of log(T)=6.0 - 6.3 ions. The loop structure is found to be anti-correlated with spectral line broadening generally attributed to non-thermal velocities. This coronal loop structure is investigated physically (temperature, density, geometry) and temporally. Light curves created from imaging instruments show brightening and dimming of the loop structure on two different time scales; short pulses of 10 - 20 min and long duration dimming of two - four hours until its disappearance. The coronal loop structure, formed from relatively blue-shifted material that is anti-correlated with spectral line broadening, shows a density of 1010 to 109.3 cm−3 and is visible for longer than characteristic cooling times. The maximum non-thermal spectral line broadenings are found to be adjacent to the footpoint of the coronal loop structure. 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: The Solar Dynamics Observatory (SDO) Education and Outreach (E/PO) Program: Changing Perceptions One Program at a Time Authors: Drobnes, E.; Littleton, A.; Pesnell, W. D.; Beck, K.; Buhr, S.; Durscher, R.; Hill, S.; McCaffrey, M.; McKenzie, D. E.; Myers, D.; Scherrer, D.; Wawro, M.; Wolt, A. Bibcode: 2012SoPh..275..391D Altcode: 2011SoPh..tmp..420D; 2011SoPh..tmp..424D; 2011SoPh..tmp..367P We outline the context and overall philosophy for the combined Solar Dynamics Observatory (SDO) Education and Public Outreach (E/PO) program, present a brief overview of all SDO E/PO programs along with more detailed highlights of a few key programs, followed by a review of our results to date, conclude a summary of the successes, failures, and lessons learned, which future missions can use as a guide, while incorporating their own content to enhance the public's knowledge and appreciation of science and technology as well as its benefit to society. Title: Observational studies of reconnection in the solar corona Authors: McKenzie, David E. Bibcode: 2011PhPl...18k1205M Altcode: In recent years, observational studies of the corona have shifted focus. Where they were once purely qualitative morphological explorations seeking to support the presence of reconnection, more investigations are providing empirical estimates of the physical conditions in the reconnecting corona. These studies are enabled and enhanced by orbiting telescopes with high angular and temporal resolution. In this article, some recent findings about the empirical quantities are reviewed, including recent estimates of the flux transferred in individual patchy reconnection episodes, the size distribution of post-reconnection flux tubes, and the energy released by the flux tubes as they shrink. Title: Distribution Functions of Sizes and Fluxes Determined from Supra-arcade Downflows Authors: McKenzie, D. E.; Savage, S. L. Bibcode: 2011ApJ...735L...6M Altcode: 2011arXiv1106.4567M The frequency distributions of sizes and fluxes of supra-arcade downflows (SADs) provide information about the process of their creation. For example, a fractal creation process may be expected to yield a power-law distribution of sizes and/or fluxes. We examine 120 cross-sectional areas and magnetic flux estimates found by Savage & McKenzie for SADs, and find that (1) the areas are consistent with a log-normal distribution and (2) the fluxes are consistent with both a log-normal and an exponential distribution. Neither set of measurements is compatible with a power-law distribution nor a normal distribution. As a demonstration of the applicability of these findings to improved understanding of reconnection, we consider a simple SAD growth scenario with minimal assumptions, capable of producing a log-normal distribution. 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: The Distributions of Post-Reconnection Flux Tube Sizes and Fluxes Determined from Supra-Arcade Downflows Authors: McKenzie, David Eugene; Savage, S. L. Bibcode: 2011SPD....42.2210M Altcode: 2011BAAS..43S.2210M Supra-arcade downflows (SADs) are downward-moving features observed in the hot, low-density region above posteruption flare arcades. They are believed to be created by patchy reconnection in the post-CME current sheet. The sizes and fluxes of SADs provide information about the process of their creation. For example, the "fractal current sheet" scenario proposed in the literature may be expected to yield a power-law distribution of sizes and/or fluxes. We examine 120 cross-sectional areas and magnetic flux estimates from observations of SADs, and find that (1) the areas are consistent with a log-normal distribution, and (2) the fluxes are consistent with both a log-normal and an exponential distribution. Neither set of measurements is compatible with a power-law distribution, and so the data do not appear to support a fractal process for SAD creation. As an alternative, we consider a simple SAD growth scenario with minimal assumptions, capable of producing a log-normal distribution. Title: Quantitative Examination of a Large Sample of Supra-arcade Downflows in Eruptive Solar Flares Authors: Savage, Sabrina L.; McKenzie, David E. Bibcode: 2011ApJ...730...98S Altcode: 2011arXiv1101.1540S Sunward-flowing voids above post-coronal mass ejection flare arcades were first discovered using the soft X-ray telescope aboard Yohkoh and have since been observed with TRACE (extreme ultraviolet (EUV)), SOHO/LASCO (white light), SOHO/SUMER (EUV spectra), and Hinode/XRT (soft X-rays). Supra-arcade downflow (SAD) observations suggest that they are the cross-sections of thin flux tubes retracting from a reconnection site high in the corona. Supra-arcade downflowing loops (SADLs) have also been observed under similar circumstances and are theorized to be SADs viewed from a perpendicular angle. Although previous studies have focused on dark flows because they are easier to detect and complementary spectral data analysis reveals their magnetic nature, the signal intensity of the flows actually ranges from dark to bright. This implies that newly reconnected coronal loops can contain a range of hot plasma density. Previous studies have presented detailed SAD observations for a small number of flares. In this paper, we present a substantial SADs and SADLs flare catalog. We have applied semi-automatic detection software to several of these events to detect and track individual downflows thereby providing statistically significant samples of parameters such as velocity, acceleration, area, magnetic flux, shrinkage energy, and reconnection rate. We discuss these measurements (particularly the unexpected result of the speeds being an order of magnitude slower than the assumed Alfvén speed), how they were obtained, and potential impact on reconnection models. Title: Earthquake distribution patterns in Africa: their relationship to variations in lithospheric and geological structure, and their rheological implications Authors: Craig, T. J.; Jackson, J. A.; Priestley, K.; McKenzie, D. Bibcode: 2011GeoJI.185..403C Altcode: 2011GeoJI.tmp...74C We use teleseismic waveform inversion, along with depth phase analysis, to constrain the centroid depths and source parameters of large African earthquakes. The majority of seismic activity is concentrated along the East African Rift System, with additional active regions along stretches of the continental margins in north and east Africa, and in the Congo Basin. We examine variations in the seismogenic thickness across Africa, based on a total of 227 well-determined earthquake depths, 112 of which are new to this study. Seismogenic thickness varies in correspondence with lithospheric thickness, as determined from surface wave tomography, with regions of thick lithosphere being associated with seismogenic thicknesses of up to 40 km. In regions of thin lithosphere, the seismogenic thickness is typically limited to ≤20 km. Larger seismogenic thicknesses also correlate with regions that have dominant tectonothermal ages of ≥1500 Ma, where the East African Rift passes around the Archean cratons of Africa, through the older Proterozoic mobile belts. These correlations are likely to be related to the production, affected by method and age of basement formation, and preservation, affected by lithospheric thickness, of a strong, anhydrous lower crust. The Congo Basin contains the only compressional earthquakes in the continental interior. Simple modelling of the forces induced by convective support of the African plate, based on long-wavelength free-air gravity anomalies, indicates that epeirogenic effects are sufficient to account for the localization and occurrence of both extensional and compressional deformation in Africa. Seismicity along the margins of Africa reflects a mixture between oceanic and continental seismogenic characteristics, with earthquakes in places extending to 40 km depth. Title: Earthquake depth distributions in central Asia, and their relations with lithosphere thickness, shortening and extension Authors: Sloan, R. A.; Jackson, J. A.; McKenzie, D.; Priestley, K. Bibcode: 2011GeoJI.185....1S Altcode: 2011GeoJI.tmp...44S This paper examines the relationship between seismogenic thickness, lithosphere structure and rheology in central and northeastern Asia. We accurately determine earthquake depth distributions which reveal important rheological variations in the lower crust. These variations exert a fundamental control on the active tectonics and the morphological evolution of the continents. We consider 323 earthquakes across the Tibetan Plateau, the Tien Shan and their forelands as well as the Baikal Rift, NE Siberia and the Laptev Sea and present the source parameters of 94 of these here for the first time. These parameters have been determined through body wave inversion, the identification of depth phases or the modelling of regional waveforms. Lower crustal earthquakes are found to be restricted to the forelands in areas undergoing shortening, and to locations where rifting coincides with abrupt changes in lithosphere thickness, such as the NE Baikal Rift and W Laptev Sea. The lower crust in these areas is seismogenic at temperatures that may be as high as 600°C, suggesting that it is anhydrous, and is likely to have great long-term strength. Lower crustal earthquakes are therefore a useful proxy indicating strong lithosphere in places that are too small in areal extent for this to be confirmed independently by estimating effective elastic thickness from gravity-topography relations. The variation in crustal rheology indicated by the distribution of lower-crustal earthquakes has many implications ranging from the support of mountain belts and the formation of steep mountain fronts, to the localization and orientation of rifting. In combination, these processes can also be responsible for the separation of the front of the thin-skinned mountain belts from their hinterlands when continents separate. Title: An Invitation to the Improved Yohkoh Legacy data Archive Authors: Takeda, A.; Acton, L. W.; McKenzie, D.; Yoshimura, K.; Freeland, S. L. Bibcode: 2010AGUFMSH11B1645T Altcode: The Yohkoh Legacy data Archive (YLA) is a unique source of solar X-ray images and spectra obtained with the Yohkoh satellite(1991-2001). The archive consists of four levels of data products from raw to highly value added, with ample amount of documentation and user-friendly web interface (http://solar.physics.montana.edu/ylegacy). The YLA is also unique in that quality and variety of the products and services have been constantly improved through these nine years after the completion of the satellite mission. Our recent improvements are: (1) Completion of the stray light correction, applied to the data after the SXT entrance filter failure in 1992. (2) Completion of the satellite attitude data correction. (3) E-mail based individual user support (E-consultant service). (4) New FITS header definition with World Coordinate System compliance. (5) Update of SXT response function based on the latest atomic data and models (Chianti 6.0.1). (6) Introduction of a new data category, Level 3, for co-aligned composite images suitable for browsing in movie mode. The main body of our archive (data from the Soft X-ray Telescope) are provided in both Yohkoh-specific (XDA) and FITS formats. The XDA format is convenient for analysis with existing SSW/Yohkoh software that runs under IDL. The more general FITS format enables use of advanced SSW applications developed in the various missions after Yohkoh. FITS products do not specifically require IDL to read and view images, which allows our products to be accessed from a wide range of communities. Our products can be accessed through our quick-look and data-search web services, and also through the Virtual Solar Observatory data search. Since 2009, YLA is funded as one of NASA's Resident Archives in Virtual Observatories for Heliophysics Data program. Through the funds, we take responsibility for maintaining the best corrected data sets, and providing the easy access and user support. The top page of the YLA web interface Title: Science Objectives for an X-Ray Microcalorimeter Observing the Sun Authors: Laming, J. Martin; Adams, J.; Alexander, D.; Aschwanden, M; Bailey, C.; Bandler, S.; Bookbinder, J.; Bradshaw, S.; Brickhouse, N.; Chervenak, J.; Christe, S.; Cirtain, J.; Cranmer, S.; Deiker, S.; DeLuca, E.; Del Zanna, G.; Dennis, B.; Doschek, G.; Eckart, M.; Fludra, A.; Finkbeiner, F.; Grigis, P.; Harrison, R.; Ji, L.; Kankelborg, C.; Kashyap, V.; Kelly, D.; Kelley, R.; Kilbourne, C.; Klimchuk, J.; Ko, Y. -K.; Landi, E.; Linton, M.; Longcope, D.; Lukin, V.; Mariska, J.; Martinez-Galarce, D.; Mason, H.; McKenzie, D.; Osten, R.; Peres, G.; Pevtsov, A.; Porter, K. Phillips F. S.; Rabin, D.; Rakowski, C.; Raymond, J.; Reale, F.; Reeves, K.; Sadleir, J.; Savin, D.; Schmelz, J.; Smith, R. K.; Smith, S.; Stern, R.; Sylwester, J.; Tripathi, D.; Ugarte-Urra, I.; Young, P.; Warren, H.; Wood, B. Bibcode: 2010arXiv1011.4052L Altcode: We present the science case for a broadband X-ray imager with high-resolution spectroscopy, including simulations of X-ray spectral diagnostics of both active regions and solar flares. This is part of a trilogy of white papers discussing science, instrument (Bandler et al. 2010), and missions (Bookbinder et al. 2010) to exploit major advances recently made in transition-edge sensor (TES) detector technology that enable resolution better than 2 eV in an array that can handle high count rates. Combined with a modest X-ray mirror, this instrument would combine arcsecondscale imaging with high-resolution spectra over a field of view sufficiently large for the study of active regions and flares, enabling a wide range of studies such as the detection of microheating in active regions, ion-resolved velocity flows, and the presence of non-thermal electrons in hot plasmas. It would also enable more direct comparisons between solar and stellar soft X-ray spectra, a waveband in which (unusually) we currently have much better stellar data than we do of the Sun. Title: Reconnection Outflows and Current Sheet Observed with Hinode/XRT in the 2008 April 9 "Cartwheel CME" Flare Authors: Savage, Sabrina L.; McKenzie, David E.; Reeves, Katharine K.; Forbes, Terry G.; Longcope, Dana W. Bibcode: 2010ApJ...722..329S Altcode: 2010arXiv1003.4758S Supra-arcade downflows (SADs) have been observed with Yohkoh/SXT (soft X-rays (SXR)), TRACE (extreme ultraviolet (EUV)), SOHO/LASCO (white light), SOHO/SUMER (EUV spectra), and Hinode/XRT (SXR). Characteristics such as low emissivity and trajectories, which slow as they reach the top of the arcade, are consistent with post-reconnection magnetic flux tubes retracting from a reconnection site high in the corona until they reach a lower-energy magnetic configuration. Viewed from a perpendicular angle, SADs should appear as shrinking loops rather than downflowing voids. We present X-ray Telescope (XRT) observations of supra-arcade downflowing loops (SADLs) following a coronal mass ejection (CME) on 2008 April 9 and show that their speeds and decelerations are consistent with those determined for SADs. We also present evidence for a possible current sheet observed during this flare that extends between the flare arcade and the CME. Additionally, we show a correlation between reconnection outflows observed with XRT and outgoing flows observed with LASCO. 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: Reconnection Outflows and Current Sheet Observed with Hinode/XRT in the April 9 2008 "Cartwheel CME" Flare Authors: Savage, Sabrina; McKenzie, D. E.; Reeves, K. K.; Forbes, T. G.; Longcope, D. W. Bibcode: 2010AAS...21640423S Altcode: 2010BAAS...41R.903S Supra-arcade downflows (SADs) have been observed with Yohkoh/SXT (soft X-rays (SXR)), TRACE (extreme ultra-violet (EUV)), SoHO/LASCO (white light), SoHO/SUMER (EUV spectra), and Hinode/XRT (SXR). Characteristics such as low emissivity and trajectories which slow as they reach the top of the arcade are consistent with post-reconnection magnetic flux tubes. The magnetic flux within the tubes provides pressure against filling with plasma. As with the standard model of reconnection, the tubes then retract from a reconnection site high in the corona until they reach a more potential magnetic configuration. Viewed from a perpendicular angle, SADs should appear as shrinking loops rather than downflowing voids. We will present observations of supra-arcade downflowing loops (SADLs) following a CME on April 9, 2008 with XRT and show that their speeds and decelerations are consistent with those determined for SADs. We will also present evidence for a possible current sheet observed during this flare that extends between the CME and the flare arcade. Additionally, we will show a correlation between reconnection outflows observed with XRT and outgoing flows observed with LASCO. Title: Quantifying Separator Reconnection Between Emerging and Existing Active Regions Authors: Malanushenko, Anna; Longcope, D. W.; McKenzie, D. E.; Yusuf, M. H. Bibcode: 2010AAS...21640507M Altcode: 2010BAAS...41..890M When one active region emerges close to an older active region, coronal loops connecting the two regions are often observed in extreme ultraviolet (EUV). This signifies the occurrence of magnetic reconnection, an important mechanism in other contexts, such as solar flares and coronal mass ejections. We measure the rate of the magnetic reconnection by identifying each coronal loop observed in EUV that connects the existing and the emerging active regions. For each loop we estimate amount of magnetic flux it carries by measuring its apparent width in EUV and the magnetic field strength in the same location using (non)-linear force-free field reconstruction (Malanushenko et. al., 2009). We find that the amount of reconnected flux apparent on EUV is smaller than the flux through the separator surface in the point charge magnetic model (Longcope, 2005). This discrepancy provides a means to estimate the fraction of reconnecting loops that would appear in the EUV bandpass. We measure the delay time between the noticeable beginning of the emergence and the reconnection apparent in EUV. We apply this analysis to five emergence events. This work expands and improves the method described by Longcope et. al. (2005). Title: Reconnection outflows and current sheet observed with Hinode/XRT in the April 9 2008 "Cartwheel CME" flare Authors: McKenzie, David; Savage, Sabrina; Reeves, Kathy; Forbes, Terry; Longcope, Dana Bibcode: 2010cosp...38.1952M Altcode: 2010cosp.meet.1952M The "Cartwheel CME" event of April 9, 2008, presents an exemplary view of motions and structures consistent with the commonly held view of magnetic reconnection. Following the eruption of the coronal mass ejection from the southwest limb of the Sun, an X-ray-bright arcade was observed to form. Hinode/XRT observed coronal loops shrinking into the top of the arcade, consistent with the reconnection picture. We present measurements of the speeds and decelerations of these shrinking loops, and demonstrate that the measurements are consistent with those determined for supra-arcade downflows in other eruptive flares. Moreover, we present evidence for a possible current sheet observed during this flare, extending between the CME and the flare arcade. The shrinking loops, and also outflows moving radially away from the Sun, were observed to move along this current sheet. Finally, we show a correlation between the anti-Sunward reconnection outflows observed with XRT and identifiable features in the CME observed with LASCO. This work is supported by NASA contracts NNM07AB07C and NNX08AG44G, and NSF con-tract ATM-0837841. Title: Flare Physics in the Hinode Era (Keynote) Authors: McKenzie, D. E. Bibcode: 2009ASPC..415..427M Altcode: Hinode's manifest of instrumentation was conceived to investigate the magnetic connections through the photosphere, lower atmosphere, and corona. The complementarity of the instruments is indeed useful, as demonstrated in numerous flares and eruptions in just the first two years of operation. I will review some of the findings from Hinode's observations of flares to date.

It is true, of course, that Hinode's capabilities have evolved since launch. These changes cause the planning of observations to be more complex, and the analysis to be less straightforward; but they do not diminish Hinode's ability to produce important observations of solar flares. On the contrary, Hinode is poised to make truly surprising discoveries. I will explain why this is so, and why we should look forward to the challenge of the coming activity cycle. Title: Reconstructing the Local Twist of Coronal Magnetic Fields and the Three-Dimensional Shape of the Field Lines from Coronal Loops in Extreme-Ultraviolet and X-Ray Images Authors: Malanushenko, A.; Longcope, D. W.; McKenzie, D. E. Bibcode: 2009ApJ...707.1044M Altcode: 2009arXiv0909.5141M Nonlinear force-free fields are the most general case of force-free fields, but the hardest to model as well. There are numerous methods of computing such fields by extrapolating vector magnetograms from the photosphere, but very few attempts have so far made quantitative use of coronal morphology. We present a method to make such quantitative use of X-ray and EUV images of coronal loops. Each individual loop is fit to a field line of a linear force-free field, allowing the estimation of the field line's twist, three-dimensional geometry, and the field strength along it. We assess the validity of such a reconstruction since the actual corona is probably not a linear force-free field, and that the superposition of linear force-free fields is generally not itself a force-free field. To do so, we perform a series of tests on nonlinear force-free fields, described in Low & Lou. For model loops we project field lines onto the photosphere. We compare several results of the method with the original field, in particular the three-dimensional loop shapes, local twist (coronal α), distribution of twist in the model photosphere, and strength of the magnetic field. We find that (1) for these trial fields, the method reconstructs twist with a mean absolute deviation of at most 15% of the range of photospheric twist, (2) heights of the loops are reconstructed with a mean absolute deviation of at most 5% of the range of trial heights, and (3) the magnitude of non-potential contribution to a photospheric field is reconstructed with a mean absolute deviation of at most 10% of the maximal value. Title: Detecting and Measuring Reconnection Outflows in the Hinode Era Authors: Savage, S. L.; McKenzie, D. E. Bibcode: 2009ASPC..415..455S Altcode: Our aim has been to provide direct quantitative measurements of reconnection signatures during solar flaring events in order to constrain the properties of flare energetics. Reconnection outflows are observed as sunward-flowing voids during long-duration flares, consistent with 3D reconnection models. Through the use of our automatic detection software, we have obtained trajectories, velocities, sizes, and magnetic flux information for outflows in several flares from various instruments. Several limitations have been encountered with instruments prior to the availability of Hinode, and it is the purpose of this work to show the progress we have made in detecting reconnection signatures in the form of supra-arcade downflows (SADs) and to emphasize the potential of making better detections and measurements with Hinode's X-ray Telescope (XRT). 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: An analysis of young ocean depth, gravity and global residual topography Authors: Crosby, A. G.; McKenzie, D. Bibcode: 2009GeoJI.178.1198C Altcode: The variation of ocean depth with age in the absence of crustal thickening and dynamic support places valuable constraints on the thermal and rheological properties of the lithosphere and asthenosphere. We have attempted to estimate this variation using a global data set of shiptracks, with particular emphasis on young ocean floor. In this respect, this paper extends a previous study published in this journal by the same authors, which concentrated on the older parts of the ocean basins. We find that, prior to 80 Ma, subsidence patterns are reasonably consistent, with gradients of 325 +/- 20 m Ma -1/2 and zero-age depths of 2600 +/- 200 m. There is a strong inverse correlation between zero-age depth and the gradient of depth with the square root of age which is unrelated to local variations in dynamic support. Global depth-age trends to 160 Ma are not significantly different to those for the individual ocean basins. Within corridors of similar basement age, gravity-topography correlations are consistently 30 +/- 5 mGal km-1. Simple isostatic theory and numerical modelling of mantle plumes suggests that, if the minimum depth of convection is defined by the base of the mechanical boundary layer, the admittance should be a function of plate age. The observation that it is not implies that the active convective upwelling beneath young lithosphere ceases at the same depth as it does beneath old oceanic plates. This result is consistent with geochemical modelling of melts near mid-ocean ridges. We have examined the relationship between residual topography and gravity worldwide, and have found that good spatial correlations are restricted to the Atlantic, North Pacific and youngest Indian ocean basins. By contrast, residual topography and gravity are poorly or negatively correlated in the South and young North Pacific Ocean and in the older Indian Ocean. Away from regions of thick crust and flexure, histograms of residual topography and gravity have symmetric distributions about zero. We then use this residual topography to estimate the volume and buoyancy flux of seven major plume swells. In Hawaii, the clear correlation between melt and swell volumes in discrete age corridors is evidence that the horizontal velocity of the hot plume material far downstream from the plume is similar to the plate spreading velocity and that the plume pulses over time. Finally, comparison with seismic tomographic models suggests that the long-wavelength (>2000 km) residual topographic and gravity anomalies have an origin deeper than 250 km. This result is consistent with observations that the admittance is approximately constant at wavelengths longer than 800 km. Title: Detecting and Measuring Reconnection Outflows in the Hinode Era Authors: Savage, Sabrina Leah; McKenzie, David E. Bibcode: 2009shin.confE.192S Altcode: Our aim has been to provide direct quantitative measurements of reconnection signatures during solar flaring events in order to constrain the properties of flare energetics. Reconnection outflows are observed as voids flowing towards the sun during long-duration flares which is consistent with 3D reconnection models. Through the use of our semi-automatic detection software, we have obtained trajectories, velocities, sizes, magnetic fluxes, and loop shrinkage energies for outflows in several flares from various instruments including SXT, TRACE, and LASCO. Several limitations, such as poor spatial resolution for high energy wavelengths and slow cadence compared to the flow speed, have been encountered with instruments prior to the availability of Hinode, and it is the purpose of this work to show the progress we have made in detecting reconnection signatures in the form of supra-arcade downflows (SADs) and to emphasize the potential of making better detections and measurements with Hinode's X-ray telescope (XRT). Title: Quantitative Examination of Supra-arcade Downflows in Eruptive Solar Flares Authors: McKenzie, D. E.; Savage, Sabrina L. Bibcode: 2009ApJ...697.1569M Altcode: Downward motions above post-coronal mass ejection flare arcades are an unanticipated discovery of the Yohkoh mission, and have subsequently been detected with TRACE, SOHO/LASCO, SOHO/SUMER, and Hinode/XRT. These supra-arcade downflows are interpreted as outflows from magnetic reconnection, consistent with a three-dimensional generalization of the standard reconnection model of solar flares. We present results from our observational analyses of downflows, which include a semiautomated scheme for detection and measurement of speeds, sizes, and—for the first time—estimates of the magnetic flux associated with each shrinking flux tube. Though model dependent, these findings provide an empirical estimate of the magnetic flux participating in individual episodes of patchy magnetic reconnection, and the energy associated with the shrinkage of magnetic flux tubes. Title: Inferring Local Twist of the Coronal Magnetic Field from Coronal Loops in EUV and X-ray Images Authors: Malanushenko, Anna; Longcope, D. W.; McKenzie, D. E. Bibcode: 2009SPD....40.2902M Altcode: Non-linear force-free fields are the most general case of force-free fields, but the hardest to model as well. There are numerous methods of computing such fields by extrapolating vector magnetograms from the photosphere, but very few attempts have so far made quantitative use of coronal morphology. We present an improved method which infers properties of the force-free field from X-Ray and EUV images of active region coronal loops. Each loop evident in an image is fit to field lines from constant-alpha fields. Our algorithm thereby estimates the three-dimensional geometry of each loop as well its local twist (alpha) and the magnetic field strength over its length. We assess the performance of this method by applying it to known examples of 3D non-linear force free fields. We demonstrate that at least some features of the local twist distribution could be reconstructed using this method. Title: Pre-flight Calibration Of The AIA Instrument On SDO Authors: Wolfson, C. Jacob; Boerner, P.; Soufli, R.; Podgorski, W.; Title, A.; Lemen, J.; Rausch, A.; Shing, L.; Stern, R.; McKenzie, D.; Testa, P.; Weber, M. Bibcode: 2009SPD....40.1704W Altcode: The Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory (SDO) is a set of four reflecting telescopes designed to acquire high-resolution images of the solar atmosphere in a variety of extreme ultraviolet, ultraviolet and visible-light wavelength bands (see Lemen et al.). AIA takes images in ten wavelength channels, whose bandpasses are determined by the collecting area dedicated to each channel and the efficiency of the mirror coatings, filters, and detector. We describe the measurements of each of these components, and present the resulting effective area as functions of wavelength. The measured effective area functions will be cross-calibrated on orbit by comparing full-disk integrated fluxes from each of the AIA channels with the calibrated irradiance measurements from the EUV Variability Experiment (EVE) on SDO. The AIA effective areas are used to calculate temperature response functions and expected count rates in each channel for observations of various solar features. Title: Properties of a Coronal Loop Structure with EIS, TRACE, and STEREO Authors: Scott, Jason; Martens, P. C. H.; McKenzie, D. Bibcode: 2009SPD....40.1217S Altcode: The physical properties of a coronal loop structure are investigated using three EUV observing instruments. The density, thermal width, and lifetime of a loop structure are found. Spectral coverage from EIS provides density and thermal information. Observations from TRACE and STEREO show the structure's geometry and intensity as a function of time in multiple wavebands. The isolated loop is straightened and characterized by a Gaussian fit to perpendicular cross-cuts of the observed structure. This allows for the extraction of background subtracted intensities which is important when isolating the coronal structure for analysis. These background subtracted intensities are then used to determine the thermal characteristics (temperature, emission measure ), density, structure width, and lifetime. These results provide much needed measurements of coronal loop structure. Title: Modeling the Evolving Magnetic Field in a Coronal Sigmoid Authors: McKenzie, David Eugene; Malanushenko, A.; Longcope, D. Bibcode: 2009SPD....40.1203M Altcode: The importance of coronal sigmoids as progenitors of eruptions and mass ejections is well established. However, the storage of magnetic energy prior to a sigmoid's eruption is difficult to quantify. While the non-potentiality of the coronal force-free fields is clearly responsible for the free energy, models of the field are difficult to verify. We utilize a method, developed at Montana State University and described at this meeting by A. Malanushenko, to model the force-free field within a coronal sigmoid observed by TRACE and Hinode/XRT. By modeling the twist in the sigmoid's field over the span of a few days leading up to its eruption, it is hoped that such a model can yield insight to the buildup of energy. This work is supported by NASA contract NNX07AI01G, and by SAO contract SV7-77003. 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: The Yohkoh Legacy Archive Authors: Acton, L. W.; Takeda, A.; McKenzie, D. E. Bibcode: 2008AGUFMSA53A1563A Altcode: Yohkoh was a Japan/US/UK mission for the study of high energy processes on the sun. Scientific operation extended from September 1991 until 14 December 2001, nearly an entire solar activity cycle. Observations included full-disk soft and hard x-ray imaging, hard x-ray spectroscopy, and high resolution flare spectroscopy in S XV, Ca XIX, Fe XXV and Fe XXVI from the Bent Crystal Spectrometer (BCS). The Yohkoh Legacy Archive (YLA) brings together all Yohkoh observational data along with extensive documentation required for a full understanding of instrumentation, mission operations, and data reduction and correction. Extensive meta-data aid the user in efficiently accessing the data base. Creation of the YLA has been the work of 8 years; the top objective has been to present the extensive Yohkoh database in a form fully usable for scientists or students who are unfamiliar with Yohkoh instrumentation. The YLA may be accessed at http://solar.physics.montana.edu/ylegacy or through the Virtual Solar Observatory (VSO), although the VSO capability is still under development. Data from the Yohkoh hard x-ray instruments and BCS are presented in flare list formats. The Soft X-ray Telescope (SXT) images are available in quantitative and movie formats. This long, uniform, archive of SXT images is especially useful for solar cycle studies as well as high resolution soft x-ray flare studies. Examples of YLA data products and research enabled by the archive will be presented. Title: Topography associated with crustal flow in continental collisions, with application to Tibet Authors: Bendick, R.; McKenzie, D.; Etienne, J. Bibcode: 2008GeoJI.175..375B Altcode: 2008GeoJI.tmp..185B Collision between an undeformable indenter and a viscous region generates isostatically compensated topography by solid-state flow. We model this process numerically, using a finite element scheme. The slope, amplitude and symmetry of the topographic signal depend on the indenter size and the Argand number of the viscous region, a dimensionless ratio of gravitational body forces to viscous forces. When applied to convergent continental settings, these scaling rules provide estimates of the position of an indenter at depth and the mechanical properties of the viscous region, especially effective viscosity. In Tibet, forward modelling suggests that some elevated, low relief topography within the northern plateau may be attributed to lower crustal flow, stimulated by a crustal indenter, possibly Indian lithosphere. The best-fit model constrains the northernmost limit of this indenter to 33.7°N and the maximum effective viscosity of Eurasian middle and lower crust to 1 × 1020 +/- 0.3 × 1020 Pa s. Title: Hinode XRT observations of a long-lasting coronal sigmoid Authors: McKenzie, D. E.; Canfield, R. C. Bibcode: 2008A&A...481L..65M Altcode: Aims:Coronal sigmoids are important sources of eruptions into interplanetary space, and a handful of models have been proposed to explain their characteristic S shape. However, the coronal X-ray images available to date have generally not had sufficient resolution to distinguish between these models. The goal of the present investigation is to determine whether the new observations from Hinode can help us to make such a distinction.
Methods: We present the first observations of a persistent coronal sigmoid obtained with the Hinode X-Ray Telescope (XRT). The excellent angular resolution of XRT (1 arcsec per pixel) and the sigmoid's location near disk center combined to provide an unprecedented view of the formation and eruption of this phenomenon. We compared the observed morphology with expectations inferred from two popular models of sigmoid formation, the bald-patch separatrix surface model and the kinking flux rope model.
Results: The images during the pre-eruptive phase show that the overall S shape of the sigmoid comprises two separate J-shaped bundles of many loops. The straight sections of the two J patterns lie anti-parallel to one another in the middle of the S, on opposite sides of the magnetic polarity inversion line. The images during the eruptive phase reveal that, before any soft X-ray flaring begins, a diffuse linear structure almost as long as the sigmoid lifts off from the middle of the S. It shows slight clockwise rotation. The X-ray flare begins with the appearance of a sheared arcade of short loops, in the area centered between the two J-shaped patterns of the sigmoid.
Conclusions: Taken together, the observational findings provide strong support for the bald-patch separatrix surface model for this sigmoid. Title: Semi-Automatic Detection Software for Supra-Arcade Downflows Authors: Savage, S. L.; McKenzie, D. E.; McLaughlin, L. Bibcode: 2007AGUFMSH44A1730S Altcode: Detectable signatures of magnetic reconnection, a possible source of solar coronal heating, aid in constraining flare energetics. Supra-arcade downflows (SADs), first detected during the Yohkoh mission, are an example of an observable consequence of magnetic flux tube reconnection. These sunward-traveling voids above arcade loops are consistent with outflows resulting in standard 3D reconnection models of solar flares. We have developed semi-automated detection software to detect downflows and analyze their trajectories, speeds, sizes, and magnetic flux in order to constrain parameters for flare modeling. We will present these measurements as observed primarily by SXT and TRACE supplemented with new XRT observations and discuss their implications. Title: Supra-Arcade Downflows: Results from Observational Analysis Authors: McKenzie, D. E.; Savage, S.; Tolan, J. E. Bibcode: 2007ASPC..369..489M Altcode: Downward motions above post-CME flare arcades are an exciting discovery of the Yohkoh mission, and have subsequently been detected with TRACE, SOHO/LASCO, SOHO/SUMER, and GOES/SXI. These ``supra-arcade downflows" have been interpreted as outflows from flux tube reconnection, consistent with a 3D generalization of the standard reconnection model of solar flares. We will present results from our observational analyses of downflows, including measured speeds and other aspects related to 3D patchy reconnection. We will also indicate the limitations of present observations, and motivations for utilizing the Solar-B instruments for measurements of these reconnection signatures. Title: Temperature Structure of Active Region Coronal Loops as seen by Hinode Authors: Scott, Jason; Winter, H.; Cirtain, J.; Martens, P. C.; McKenzie, D. Bibcode: 2007AAS...210.9437S Altcode: 2007BAAS...39..327S We present preliminary results from Hinode of coronal loops. MSU's SEMAST code is used to perform differential emission measure analysis along active region coronal loops. The differential emission measures are then used to investigate the temperature and density structure of the loops. The results are then entered into the coronal loop database and compared to theoretical models for scaling laws and heating mechanisms.

This work is supported by NASA GSRP fellowship NNG05GK64H Title: Erratum Authors: Emmerson, B.; Jackson, J.; McKenzie, D.; Priestley, K. Bibcode: 2007GeoJI.169.1300. Altcode: No abstract at ADS Title: EIS/Hinode Look At Active Region Dynamics Authors: Ugarte-Urra, Ignacio; Warren, H. P.; Brooks, D. H.; Williams, D. R.; Cirtain, J. W.; McKenzie, D. E.; Weber, M.; Hara, H.; Harra, L. K. Bibcode: 2007AAS...210.9429U Altcode: 2007BAAS...39..222U We present some initial results from the Hinode EUV Imaging Spectrometer (EIS) on the heating and cooling of active region loops. The events we observe are part of the short term active region evolution within the span of 50 hours of sit-and-stare observations. We investigate the temporal evolution of the intensity and Doppler shift of spectral lines formed at different temperatures. We then determine time lags and cooling times at various temperature regimes and discuss the results in the context of previous results provided by earlier space missions. This effort is considered a first step into the hydrodynamic modeling of the loop structures. The morphology of the structures is obtained from X-Ray Telescope (XRT) and TRACE images. Title: Semi-Automatic Detection Software For Supra-Arcade Downflows Authors: Savage, Sabrina; McKenzie, D. E.; McLaughlin, L. Bibcode: 2007AAS...210.2518S Altcode: 2007BAAS...39..134S It is widely believed that magnetic reconnection is a key mechanism in coronal activity and flare energy release. Due to the spatial and temporal scales involved with observing structures in this extremely faint and dynamic regime, determining the physical characteristics of reconnection using appropriate observable signatures has proven to be challenging. Supra-arcade downflows (SADs), first detected during the Yohkoh mission, are just such an example of an observable consequence of magnetic flux tube reconnection. These sunward-traveling voids above post-eruption coronal arcades are consistent with outflows predicted by 3D reconnection models of solar flares. We have developed semi-automated software to detect downflows and analyze their trajectories, speeds, sizes, and magnetic flux in order to constrain parameters for flare modeling. We will present these measurements as observed primarily by SXT and TRACE and discuss their implications. Title: Hinode/XRT Observations of a Coronal Sigmoid Authors: McKenzie, David E.; Canfield, R. C. Bibcode: 2007AAS...210.7208M Altcode: 2007BAAS...39Q.180M We present the first observations of an X-ray sigmoid made with the Hinode X-Ray Telescope, co-aligned with those of TRACE and SoHO/MDI. XRT's extraordinary angular resolution (1 arcsec/pixel) and the sigmoid's location near disk center combined to provide an unprecedented view of the formation and eruption of this phenomenon. XRT observed the sigmoid over several days, with cadences as high as 1 image per 10--30 seconds. The first motions associated with eruption of the sigmoid started at 0600UT on 12-Feb-2007; the first brightening of the ensuing X-ray arcade was seen at 0740UT.

The images during the pre-eruptive phase, which ends with the onset of large-scale motions, show:<ul><li>The overall S shape of the sigmoid is not defined by any single X-ray loop. Rather, many individual loops collectively comprise an S-shaped pattern.<li>The S shape is comprised of two separate J shapes, whose straight sections lie anti-parallel to one another in the middle of the S, on opposite sides of the magnetic polarity inversion line. <li>During the several-day span of the XRT observation, the S shape gradually becomes better defined.</ul>The images during the eruptive phase show:<ul><li>Approximately 100 minutes before any soft X-ray flaring begins, a diffuse linear structure, almost as long as the sigmoid, lifts off from the middle of the S. It shows slight clockwise rotation.<li>The X-ray flare begins with the appearance of a sheared arcade of short loops, in the area centered between the two J-shaped patterns of the sigmoid. <li>Within 16 hours of the start of the flare, no S shape remains.</ul>Taken together, these features provide strong support for the Bald-Patch Separatrix Surface model of sigmoids put forth by Titov & Demoulin (1999). Title: A Model for E/PO Success: The Space Public Outreach Team Authors: Littenberg, Tyson; Shapiro Key, J.; McKenzie, D. E. Bibcode: 2007AAS...21011601L Altcode: 2007BAAS...39..241L The Space Public Outreach Team (SPOT) program at Montana State University brings presentations about current and future NASA missions to Montana K-12 students at no cost to the schools. Formerly the Mars Public Outreach Program (MPOP), this Education and Public Outreach model of undergraduate presenters, graduate student managers, and faculty advisers has been field tested in Montana for over ten years and is now exportable to other institutions. The SPOT program is a proven success, garnering rave reviews from students and teachers alike, while reaching geographically isolated and underserved populations for the low institutional cost of approximately four dollars per participant. We will outline the SPOT model and highlight some of the program's successes. Title: The relationship between depth, age and gravity in the oceans Authors: Crosby, A. G.; McKenzie, D.; Sclater, J. G. Bibcode: 2006GeoJI.166..553C Altcode: 2006GeoJI.tmp..146C We reassess the applicability of the thermal plate cooling model to the subsidence of the North Pacific, Atlantic and North Indian Ocean Basins. We use a new numerical plate model in which the thermophysical parameters of the lithosphere vary with temperature according to the results of laboratory experiments, and the ridge temperature structure is consistent with the thickness of the oceanic crust. We first attempt to exclude thickened crust from our data set, and then to exclude swells and downwellings by masking regions of the data that remains that have significant gravity anomalies when there exists a clear regional correlation between intermediate-wavelength gravity and topography. We find that the average variation of depth with age is consistent with conventional half-space models until about 90 Myr. Thereafter, the departure from the half-space cooling curve is more rapid than predicted using simple conductive plate cooling models. The depth-age curves in the Pacific and Atlantic show ~250 m of temporary shallowing between the ages of 90-130 Myr, a result consistent with the outcome of experiments on the initiation of small-scale boundary layer convection. The results do not change significantly if the estimated component of the gravity arising from plate cooling is subtracted prior to calculation of the correlation between gravity and topography. A 90-km-thick conductive plate is nevertheless a reasonable model for the average temperature structure of the oldest part of the Pacific ocean lithosphere. In the Pacific, the broad topographic undulations associated with the Line Island Swell, the Hawaiian Swell and surrounding basins have correlated gravity anomalies and an admittance of approximately 30 mGal km-1 and are likely to result from convective circulation in the upper mantle. In the Northeast Atlantic, the intermediate-wavelength admittance over the Cape Verde swell is similar; in the Northwest Atlantic over the Bermuda Swell it is slightly larger but not as well constrained. Title: 3D Reconnection Simulations of Descending Coronal Voids Authors: Linton, Mark; Longcope, D.; Warren, H.; McKenzie, D. Bibcode: 2006SPD....37.0123L Altcode: 2006BAAS...38R.219L We will present simulations of a highly localized, finite durationburst of 3D reconnection in a post-CME current sheet. Suchreconnection forms a pair of 3D reconnected flux tubes piercing thecurrent sheet. These tubes retract from the reconnection region,pushing their way through the surrounding magnetic field to form apost-reconnection arcade below the reconnection region. We willdiscuss how the evolution of these reconnected flux tubes can formthe descending, post-eruption voids which have been seen in thehigh corona by the Yohkoh, TRACE and LASCO instruments. Wewill compare the velocities and deceleration profiles of theobserved voids with those of the simulated reconnected flux tubes.We will also show how the presence of multiple reconnectionregions in a single current sheet affects the dynamics of thereconnected tubes. Title: Quantitative Examination of Observed Reconnection Outflows Authors: McKenzie, David E.; Savage, S. Bibcode: 2006SPD....37.2403M Altcode: 2006BAAS...38..251M Downward motions above post-CME flare arcades--the supra-arcade downflows--are important signatures of magnetic reconnection in flares. As tracers of reconnection outflow, their characteristics are indicative of the parameters of 3D patchy reconnection, including the size of participating flux tubes, and, by extension, the characteristic size of the localized diffusion region. As we will show, application of automated feature-tracking programs to flare images from SXT and TRACE yields empirical estimates of important quantities for understanding patchy reconnection, including speeds, locations, size distributions, and even the amount of flux participating in a typical reconnection.This work is supported by NASA Grant NNG04GB74G. Title: Observations of Separator Reconnection to an Emerging Active Region Authors: Longcope, D. W.; McKenzie, D. E.; Cirtain, J.; Scott, J. Bibcode: 2005ApJ...630..596L Altcode: Extreme-ultraviolet (EUV) observations of an emerging active region are used to study separator reconnection in the corona. We identify each EUV loop connecting the emerging polarity to a nearby existing active region over the 41 hr period beginning at emergence onset. Their geometrical resemblance to post-reconnection field lines from a magnetic model of the active region pair implicates separator reconnection in their production. While some reconnection is evident within 7 hr of emergence onset, the most intense period occurs after a 1 day delay. The sum of cross sections of all observed loops accounts for only one-fifth of the transferred magnetic flux predicted by the model. We suggest that the remaining loops remain at temperatures too high, or at densities too low, to be detected in our EUV data. The most intense reconnection requires as much as 109 V along the coronal separator; however, the observed loops suggests that the flux is transferred as discrete bundles of ~4×1018 Mx each. The reconnection appears to directly dissipate only a small fraction of the energy released, while the rest is dissipated within the post-reconnection flux over the ensuing 6 or more hours the loops remain visible. The net energy released, and ultimately dissipated, is consistent with the amount that could be stored magnetically during the 24 hr delay between emergence and reconnection. Title: Education & Public Outreach in Montana, Supporting the Solar Dynamics Observatory Authors: Winter, H. D.; McKenzie, D. E. Bibcode: 2005AGUSMSH13D..03W Altcode: In the Space Public Outreach Team (SPOT) program at Montana State University (MSU), currently a major component of SDO Education and Public Outreach at MSU, the hallmark of the program has been the presentation of cutting-edge science regarding topics of current interest. The program, under the management of Montana Space Grant Consortium since 1996, is a proven way to bring the excitement of NASA space science investigations to primary and secondary schools, while simultaneously involving university students in E/PO. The program is remarkably cost-effective, useful as a service-learning device, and extremely popular. We will outline the mechanisms of the SPOT program, including the involvement of a diverse group of undergraduates, and its recent expansion to reach more of Montana's students. Title: Statistical Relationships in Characteristics of a Sample of Interplanetary Coronal Mass Ejections Detected Near Earth Authors: McKenzie, D. E.; Wilson, K. G.; Leamon, R. J. Bibcode: 2005AGUSMSH32A..02M Altcode: Using in situ measurements of solar wind conditions near Earth, we compared the signatures of a sample of transients, which we tentatively identify as magnetic clouds. Images from several solar observatories were utilized to identify the source eruptions which launched each ICME from the Sun. The plasma conditions within these structures were compared, and trends were sought that would correlate with the type of solar progenitor structure that spawned the eruptions. Additionally, a magnetic model was fitted to the measurements of each ICME detected near Earth. We present findings that suggest a systematic difference in cloud structure, depending on progenitor type; also, we present results indicating a relationship between the speed of transit from Sun to Earth and the magnetic field strength in the ICME. Title: Observations of Separator Reconnection to an Emerging Active Region Authors: Longcope, D. W.; Cirtain, J.; McKenzie, D.; Scott, J. Bibcode: 2004AGUFMSH13A1140L Altcode: Extreme ultraviolet (EUV) observations of an emerging active region are used to study separator reconnection in the corona. We follow each EUV loop connecting the emerging polarity to a nearby existing active region. Their geometrical resemblance to post-reconnection field lines from a magnetic model of the active region pair implicates separator reconnection in their production. While some reconnection is evident within 7 hours of emergence onset, the most intense period occurs after a one-day delay. The sum of cross sections of all observed loops accounts for only one-fifth of the magnetic flux whose transfer the model predicts. We suggest that the remaining loops remain at temperatures too high, or at densities too low, to be detected in our EUV data. The most intense reconnection requires as much as 260 MV along the coronal separator, however, the observed loops suggests that the flux is transfered as discrete bundles of 1.0e18 Mx each. The reconnection appears to directly dissipate only a small fraction of the energy released, while the rest is dissipated within the post-reconnection flux over the ensuing 6 or more hours, during which the flux remains visible. The net energy released, and ultimately disiipated, is consistent with the amount which could be stored during the 24-hour delay between emergence and reconnection. This work was supported by NASA grant NAG5-10489 Title: Periodic Variations in X-Ray Emission Intensity of Coronal Loops Authors: McKenzie, D. E.; Pollock, E.; Lane, C. Bibcode: 2004ESASP.575..422M Altcode: 2004soho...15..422M No abstract at ADS Title: Geoeffective CMEs, Filaments, and Sigmoids Authors: McKenzie, D. E.; Leamon, R. J. Bibcode: 2004AAS...204.3801M Altcode: 2004BAAS...36..712M Coronal mass ejections--particularly those with flux rope structures--have the potential to trigger geomagnetic storms, depending on the properties of the flux ropes. Eruptions of both filaments and coronal sigmoids have been indicated as important drivers of space weather, and both filaments and sigmoids have been modeled with flux rope structure. However, the analysis reported by Leamon et al. (2002) suggested that magnetic clouds associated with filament eruptions are different from magnetic clouds associated with erupting sigmoids. In this investigation, we are exploring the possibility of predicting the geoeffectiveness of CMEs through analysis of the pre-eruption magnetic structures. Title: SUMER spectral observations of post-flare supra-arcade inflows Authors: Innes, D. E.; McKenzie, D. E.; Wang, Tongjiang Bibcode: 2003SoPh..217..247I Altcode: On 21 April 2002 a large eruptive flare on the west limb of the Sun developed a bright, very dynamic, post-flare arcade. In TRACE 195 Å images, a series of dark, sunward moving flows were seen against the bright extreme ultraviolet (EUV) arcade. SUMER obtained a series of spectra of the dark EUV flows in the lines C ii, Fe xii, and Fe xxi at a fixed position above the limb. These spectra give spatially resolved line-of-sight velocities and emission measures for the arcade plasma over a temperature range 2×104 to 107 K. The flows are dark in all SUMER lines. The UV continuum longward (∼ 1350 Å) and shortward (∼ 675 Å) of the hydrogen Lyman limit is used to determine whether the dark 195 Å inflows are due to regions of low plasma density (plasma voids) or cold absorbing material. There is some evidence of absorption near the front of one of the inflows; however, along most of the dark channels there is no change in continuum ratio and we therefore conclude, as originally suggested by McKenzie and Hudson (1999), that they are plasma voids. Title: Observations of 1000 km s−1 Doppler shifts in 107 K solar flare supra-arcade Authors: Innes, D. E.; McKenzie, D. E.; Wang, Tongjiang Bibcode: 2003SoPh..217..267I Altcode: An X1.5 flare on the west limb of the Sun on 21 April 2002 developed a large supra-arcade about 30 min after flare onset. The growth of the supra-arcade can be followed in both TRACE 195 Å images and SUMER spectra. Its growth seems to be associated with dark (in TRACE images), sunward moving channels that descend onto the arcade from above. SUMER recorded Doppler shifts of 800-1000 km s−1 in Fe xxi 1354 Å from positions where this sunward flow interacts with the arcade tops. We describe the observations, focusing on the relationship of the high Fe xxi line shifts to the sunward moving dark flows. Title: Simultaneous SUMER and TRACE Observations of Supra-arcade Downflows and Oscillations Authors: McKenzie, D. E.; Innes, D. E.; Wang, T. Bibcode: 2003SPD....34.1510M Altcode: 2003BAAS...35..832M The 21 April 2002 X-class solar flare exhibited supra-arcade downflows of the type described by McKenzie and Hudson (1999). The flare was observed simultaneously by several observatories, and the downflows were clearly imaged by TRACE and SOHO/SUMER. We present a comparison of the TRACE and SUMER data concerning the supra-arcade downflows, and demonstrate that the dark downflow features are consistent with regions of locally depressed plasma density. Furthermore, the implications of the oscillatory behavior of the supra-arcade spikes for coronal seismology will be considered.

We gratefully acknowledge support from NASA, DARA, CNES, and ESA. Title: Five years of Yohkoh science nuggets Authors: Hudson, H. S.; McKenzie, D. E.; Nitta, N. V. Bibcode: 2002AGUFMSH52A0453H Altcode: The Yohkoh "science nuggets", weekly Web-based reports emphasizing current Yohkoh observations, began October 24, 1997. Many writers (the SXT "chief observers" in particular) contributed, and over the years a characteristic style developed: these were educational pieces rather than public-relations puffs, and they each attempted to describe a particular item for a technically savvy non-specialist. In this poster we summarize the nugget philosophy and point out some of our favorites, such as the remarkable "triple jet." This and many other interesting observations have not yet otherwise been published. Since December 2001 we have gradually broadened our science basis to include SOHO, TRACE, and now RHESSI input. The topic index lists more than 60 categories, and there is a general search facility. We present this poster partly to encourage discussion of the future development of the series. Title: The Point Spread Function of the Yohkoh Soft X-ray Telescope Authors: McKenzie, D. E.; Gburek, S.; Acton, L. W.; Martens, P. C. Bibcode: 2002AAS...200.5502M Altcode: 2002BAAS...34Q.732M The point spread function (PSF) of the Yohkoh solar observatory's Soft X-ray Telescope has two primary components, a sharply defined core and a diffuse wing due to photon scattering. Because the extent of the PSF is significantly wider than a single pixel, its characterization is useful for improvement of the quality of the SXT images. We will present results from analyses of the two PSF components, and demonstrate our best model of the core and scattering wing of the SXT point spread function. An example of PSF deconvolution to remove the effects of photon scattering will be given. Title: Signatures of Reconnection in Eruptive Flares [Invited] Authors: McKenzie, D. E. Bibcode: 2002mwoc.conf..155M Altcode: Solar flares are defined by magnetism. The energy that is stored up, transferred, and released is done so in and by the magnetic fields of the Sun; the structures in which the flares occur are wholly dependent on the configuration of magnetic connections; and it is the rearrangement of these connections that we believe plays such a large and important role in many of the processes observed in flares. Many of our theoretical pictures of flare mechanisms rely in some part on magnetic reconnection, and one by one the observable signatures of these models are being uncovered in chromospheric and coronal data. These data, in turn, introduce observational constraints that help to drive the models. I will summarize some key observations that have helped to support the case for reconnection, and that have helped us to peer more deeply into the behavior of coronal plasmas and magnetic fields. Title: Reconnection observed: 2d and 3d elements Authors: McKenzie, David Bibcode: 2002ocnd.confE..20M Altcode: No abstract at ADS Title: Modeling the coronal loop of an X-ray bright point Authors: McMullen, R.; Longcope, D.; McKenzie, D.; Kankelborg, C.; Klimchuk, J. Bibcode: 2002ocnd.confE..28M Altcode: No abstract at ADS Title: The Yohkoh Public Outreach Project Authors: Larson, M. B.; Slater, T.; McKenzie, D.; Acton, L.; Alexander, D.; Lemen, J.; Freeland, S.; Metcalf, T. Bibcode: 2002mwoc.conf..117L Altcode: The NASA funded Yohkoh Public Outreach Project (YPOP) began in 1995 with the goal of providing public access to high quality Yohkoh SXT data via the World Wide Web. The project utilizes the intrinsic excitement of the SXT data, and in particular the SXT movies, to develop science learning tools and classroom activities. The WWW site at URL: http://www.lmsal.com/YPOP/ uses a movie theater theme to highlight available Yohkoh movies in a format that is entertaining and inviting to non-scientists and well received by scientists. We will discuss the wide range of people YPOP has reached over the past six years, as well as lessons learned during the development of the project. Title: The Yohkoh Public Outreach Project: A Space Science Resource for Formal and Informal Education Authors: Lemen, J. R.; Alexander, D.; Metcalf, T. R.; Freeland, S. L.; Acton, L. W.; Larson, M.; McKenzie, D.; Slater, T. Bibcode: 2001AGUFMED12A0160L Altcode: The Yohkoh Public Outreach Project (YPOP) is a NASA-funded web site maintained by scientists and educators at Lockheed Martin Solar and Astrophysics Lab. and Montana State University. YPOP includes a range of activities for youngsters, parents, teachers and anyone interested in learning more about the Sun. YPOP utilizes a number of approaches to the dissemination of solar data which incorporates elements of both formaleducation, via a number of lesson plans and classroom activities, and informal education, via access to the latest solar images, a solar tour, and updated movies. This combination has proved extremely effective in providing quality access to scientific data for a broad audience with a wide range of interests. The Yohkoh Public Outreach Project can be found at http://www.LMSAL.com/YPOP. Title: Simulations of an X-Ray Bright Point's Evolution Authors: McMullen, R. A.; Longcope, D. W.; McKenzie, D. E.; Kankelborg, C. K. Bibcode: 2001AGUFMSH11C0726M Altcode: We study the spatial structure and temporal evolution of an X-ray bright point loop in order to understand the role of magnetic energy dissipation. We use a time-dependent gasdynamic model to simulate the corona and transition region in the x-ray bright point's coronal loop. For this work we model a bright point observed by TRACE, Yohkoh and SOHO on June 17, 1998, where the magnetic field geometry is derived from an extrapolation of magnetograms. We study the effects of various spatial and temporal distributions of heat deposition within the loop. The quantity of energy deposited and the location of the energy release is constrained by a model equilibrium magnetic field. We model the observed transient brightening of the bright point as a series of nanoflare events. Title: Hard X-rays from Slow Flares Authors: Hudson, H. S.; McKenzie, D. E. Bibcode: 2001EP&S...53..581H Altcode: "Slow LDEs" are those for which the rise phase is slow, as well as the decay phase. Such flares follow the Neupert effect, which implies that the non-thermal energy release has a similar relationship to heating as in a normal impulsive flare. Based on a sample of 53 slow LDEs during the first nine years of Yohkoh observations, we find 19 for which substantial overlap occurs with BATSE hard X-ray observations. These events tend strongly to have extended hard X-ray emission even though their hard X-ray emission does not tend to be "impulsive" in the sense of rapid variation. The hard X-ray fluences for these 19 events correlate with the soft X-ray peak fluxes, implying strong non-thermal particle acceleration even for these relatively slow energy-release rates. These events often correspond to the occurrence of "supra-arcade downflows," a phenomenon consistent with the classical reconnection model for gradual-phase flare energy release. This correspondence suggests a close relationship, not depending strongly upon time scale, between large-scale reconnection and the acceleration of non-thermal electrons. Title: Downflows and structure above LDE arcades: Possible signatures of reconnection? Authors: McKenzie, D. E.; Hudson, H. S. Bibcode: 2001EP&S...53..577M Altcode: We will introduce a set of observations made during the decay phase of long duration event (LDE) flares on the Sun. In a number of events, the soft X-ray images from Yohkoh SXT indicate a downward directed flow field in the region immediately above the flare arcade. These are tentatively identified as evidence of reconnection outflows. The prototypical event is the M5 flare of 20 January 1999, presented by McKenzie and Hudson (1999); since the time that paper was completed, sixteen more events have been found in the interval April 1998 to February 2000. As in the 20 January event, the speeds of downflow are 35-500 km s-1, lower than both the freefall speed and the typically assumed Alfvén speed. The motion is evidenced by both dark and bright (i.e., X-ray emitting) features, some of which may have a looplike morphology; no cool counterparts have been detected in Hα or EUV observations. Movies depicting some of the LDE downflows were presented at this meeting; these also appear in the journal Solar Physics (McKenzie, 2000), since they cannot be presented in these Proceedings. Title: Melt Generation and Movement Beneath Theistareykir, N.E. Iceland Authors: McKenzie, D.; Slater, L.; Gronvold, K.; Shimizu, N. N. Bibcode: 2001eag..conf.3605M Altcode: No abstract at ADS Title: Simultaneous Magnetographic and XUV Observations of a Coronal Jet Authors: McKenzie, D. E.; DeForest, C. Bibcode: 2001AGUSM..SH41A14M Altcode: On 03 November 2000, a jet of hot plasma appeared in the solar corona, and was observed by the Yohkoh Soft X-ray Telescope (SXT) and the TRACE coronal imager. The jet of magnetically channeled plasma, measuring over 280 megameters in length, serendipitously occurred within the high-resolution field of view of the SOHO Michelson Doppler Interferometer (MDI). We present the X-ray, extreme ultraviolet, and magnetographic observations, and attempt to draw conclusions about the evolution of the jet based upon the evolution of the magnetic field. Title: Active region transient brightenings. A simultaneous view by SXT, EIT and TRACE Authors: Berghmans, D.; McKenzie, D.; Clette, F. Bibcode: 2001A&A...369..291B Altcode: This paper reports on a qualitative study on the weakest flarelike brightenings in active region that can be observed with current coronal imagers. Specificallly, we investigate the correspondence of the ``active region transient brightenings'' (ARTB) first observed almost a decade ago with SXT with similar brightenings in the EUV that are now observed by EIT and TRACE. For this goal, exceptionally high cadence image sequences were acquired of a small but rapidly evolving active region (NOAA 8218), simultaneously by SXT, EIT, and TRACE. Within the timeframe of this coordinated campaign, we detected 41 soft X-ray brightenings and 373 EUV brightenings. We find that the strongest brightenings observed by EIT are indeed the EUV counterparts of the ARTBs seen by SXT. Weaker brightenings seen by EIT often do not have an X-ray counterpart. Among the brightenings detected with SXT we discover a new subpopulation, consisting of events that brighten in soft X-rays only, at a footpoint of a pre-existing SXT loop shortly after an ARTB occurred at the other footpoint. The propagation speed of the perturbation suggests an interpretation in terms of slow mode MHD waves. Title: Large Doppler Shifts in X-Ray Plasma: An Explosive Start to Coronal Mass Ejection Authors: Innes, D. E.; Curdt, W.; Schwenn, R.; Solanki, S.; Stenborg, G.; McKenzie, D. E. Bibcode: 2001ApJ...549L.249I Altcode: We report observations, taken with the Solar Ultraviolet Measurements of Emitted Radiation spectrometer, of spatially resolved high red and blue Doppler shifts (up to 650 km s-1) from X-ray-emitting plasma in the corona above a flare. The high Doppler shifts are seen minutes after a fast, faint optical front is seen racing through the same part of the corona in images taken with the Mirror Coronagraph for Argentina. The association of the large-scale fast optical emission front with soft X-ray emission and high Doppler shifts suggests plasma heating and acceleration in the wake of a shock. Title: Velocity Fields and Structure above LDE arcades: Possible Observational Signatures of Reconnection Authors: McKenzie, D. E. Bibcode: 2000SPD....31.0150M Altcode: 2000BAAS...32S1289M In a growing number of CME events, the X-ray images from Yohkoh SXT reveal velocity fields above the eruption site, directed downward into the top of the flare arcade. These motions, with plane-of-sky speeds typically between 50 -- 500 km s-1, are evidenced by both dark (in X-rays) and bright (i.e., X-ray emitting) features, some of which appear to have a looplike morphology. No counterparts have been detected in simultaneous Hα or EUV imagery. The ``supra-arcade downflows" are tentatively interpreted as resulting from magnetic field line shrinkage, a signature of outflow from reconnection sites above the post-eruption arcade. I will present a summary of the flare events in which these velocity fields have been detected (to date, 17 in the last two years), and movies showing the structure and motion above some of the flare arcades. This work was supported by NASA under Marshall Space Flight Center contract NAS8-40801 with the Lockheed Martin Advanced Technology Center. Title: Observations of solar wave/instability phenomena as imaged by EIT/SOHO, TRACE and Yohkoh/SXT Authors: Berghmans, D.; McKenzie, D. Bibcode: 2000AIPC..537..168B Altcode: 2000wdss.conf..168B On May 13 1998, active region NOAA 8218 was observed in the context of the SOHO/JOP80 campaign by an array of 8 different ground-based and space-born instruments. The emphasis was set on imaging of small-scale dynamics in this relatively small but rapidly evolving AR. In particular, SOHO/EIT (195 Å), TRACE (171 Å) and YOHKOH/SXT produced subfield image sequences at their respective highest possible rates. We searched for wave and instability phenomena by using an automated recognition scheme. This result in a wide inventory of propagating disturbances and localized transient brightenings. By comparing the soft X-ray signature as recorded by SXT with the EUV-signature as collected by EIT and TRACE, we are able to distinguish between various types of active region transients. As such we find that the strongest brightenings observed by EIT are indeed the EUV counterparts of the previously reported ARTBs seen by SXT. Weaker brightenings seen by EIT do often not have an X-ray counterpart. Moreover, in an extended system of faint quasi-open loops, we find propagating disturbances, with speeds of the order of 100 km/s, both in EIT and TRACE images. These are interpreted as sonic perturbations. The brightenings will be discussed in this paper while the propagating disturbances are described in the presentation by Eva Robbrecht at this conference. . Title: Supra-arcade Downflows in Long-Duration Solar Flare Events Authors: McKenzie, D. E. Bibcode: 2000SoPh..195..381M Altcode: This report seeks to introduce the reader to a set of observations made during the decay phase of long-duration event (LDE) flares on the Sun. In a number of events, the soft X-ray images from Yohkoh SXT indicate a downward-directed flow field in the region immediately above the flare arcade. The prototypical event is the M5 flare of 20 January 1999, presented by McKenzie and Hudson (1999); since the time that paper was completed, eleven more events, all related to coronal mass ejections, have been found in the interval 1 January 1998 to 8 May 1999. As in the 20 January event, the speeds of downflow are 45-500 km s−1, lower than both the free fall speed and the typically assumed Alfvén speed. A comparison is drawn between the SXT observations and the EUV and Hα data, where such are available. Important additions to our knowledge since the first paper are: (i) the motion is evidenced by both dark and bright (i.e., X-ray emitting) features, some of which may have a loop-like morphology; (ii) no cool counterparts have been detected in Hα or EUV observations. The data are compared to the expected appearance according to two likely (and opposing) interpretations: an `above-the-arcade coronal rain' interpretation and a `shrinking magnetic flux tube' interpretation. In the current standard explanation of the formation of post-CME arcades, motion of the latter type may be related to outflow from a reconnection site. Movies depicting some of the flare events are on the accompanying CD-ROM. Title: Flexure of Venusian Lithosphere Measured from Residual Topography Authors: Barnett, D. N.; McKenzie, D. Bibcode: 2000LPI....31.1254B Altcode: No abstract at ADS Title: Hard X-rays from "Slow LDEs" Authors: Hudson, H. S.; McKenzie, D. E. Bibcode: 2000ASPC..206..221H Altcode: 2000hesp.conf..221H No abstract at ADS Title: Multi-Imager Study of Transients and Propagating Disturbances in Active Region Loops (SOHO JOP80 Campaign) Authors: Berghmans, D.; Clette, F.; Robbrecht, E.; McKenzie, D. Bibcode: 1999ESASP.448..575B Altcode: 1999ESPM....9..575B; 1999mfsp.conf..575B No abstract at ADS Title: Active Region Transient Brightenings : EIT Versus SXT Authors: Berghmans, D.; McKenzie, D.; Clette, F. Bibcode: 1999ESASP.446..173B Altcode: 1999soho....8..173B On May 13, 1998, the Extreme-Ultraviolet Imaging Telescope (EIT, on board SOHO) has produced a unique image sequence operating in 'shutterless mode' (SOHO JOP 80). In JOP 80, EIT is the leading instrument, followed by several space born instruments (SXT, TRACE, MDI, CDS, SUMER), as well as two observatories on the ground (in La Palma and Sac Peak). The target of the campaign was a relatively small but rapidly evolving active region (AR 8218). For the EIT contribution, a 15 s cadence was achieved in the Fe XII bandpass at 195 deg by leaving EIT's shutter open for 1 hour and operating the CCD in frame transfer mode. We have started the analysis of the huge data set, by making an inventory of the transients observed in the EIT image sequence. These transients range from a B3.5 flare producing a large plasma flow along pre-existing loops, to smaller EUV brightenings of active region loops. In addition, a new class of weaker footpoint brightenings was discovered that produce wave-like disturbances propagating along quasi-open field lines (see the presentation by Eva Robbrecht at this workshop). In this paper we take the opportunity provided by JOP 80, to investigate the correspondence of the transient brightenings observed by EIT in this active region, with the ARTB previously observed by SXT and studied by Shimizu (1992). Within the simultaneous high cadence SOHO JOP 80 image sequences, both EIT and SXT accummulated a few tens of brightening events. At the time of the writing of this abstract, we can say that most of the SXT events have indeed 1 or more EIT counterparts. Typically the SXT events are somewhat bigger than the EIT events where the latter are ussualy located toward the point of origin of the SXT events. Whereas a few brightenings exist in one dataset without any trace in the other dataset (in both directions), we have additionally for a few brightenings in the SXT data, a corresponding EIT darkening as if the plasma is suddenly heated and dissappears from the EIT passband. Title: X-Ray Observations of Motions and Structure above a Solar Flare Arcade Authors: McKenzie, D. E.; Hudson, H. S. Bibcode: 1999ApJ...519L..93M Altcode: In this Letter, we describe a solar flare that was observed by Yohkoh in 1999 January 20. This long-duration event is notable because the Yohkoh images show not only the formation of the arcade associated with the coronal mass ejection but also a considerable amount of motion above the arcade in the region normally identified with a large-scale current sheet or the outflow from magnetic reconnection in the current sheet. A number of arcade events of this morphological type (i.e., a fan of spikelike ``rays'' above the posteruption loops) have been seen by Yohkoh, but in this case we have a much clearer view of mass motions in the region above the arcade. The motions indicate field-line retraction without the formation of long-lasting cusps during the rise phase of the flare, and a downward flow above the arcade during the decay phase. The late-phase downward motion is in the form of X-ray dark voids moving at 100-200 km s-1, i.e., at velocities much smaller than the free-fall speed or the assumed Alfvén speed. We interpret the voids as cross sections of evacuated flux tubes resulting from intermittent reconnection following the associated coronal mass ejection. We believe these data represent the first direct evidence of high-speed flows in the region immediately above the flare loops. Title: Making YOHKOH SXT Images Available to the Public: The YOHKOH Public Outreach Project Authors: Larson, M. B.; McKenzie, D.; Slater, T.; Acton, L.; Alexander, D.; Freeland, S.; Lemen, J.; Metcalf, T. Bibcode: 1999AAS...194.7024L Altcode: 1999BAAS...31..941L The NASA funded Yohkoh Public Outreach Project (YPOP) provides public access to high quality Yohkoh SXT data via the World Wide Web. The products of this effort are available to the scientific research community, K-12 schools, and informal education centers including planetaria, museums, and libraries. The project utilizes the intrinsic excitement of the SXT data, and in particular the SXT movies, to develop science learning tools and classroom activities. The WWW site at URL: http://solar.physics.montana.edu/YPOP/ uses a movie theater theme to highlight available Yohkoh movies in a format that is entertaining and inviting to non-scientists. The site features informational tours of the Sun as a star, the solar magnetic field, the internal structure and the Sun's general features. The on-line Solar Classroom has proven very popular, showcasing hand-on activities about image filtering, the solar cycle, satellite orbits, image processing, construction of a model Yohkoh satellite, solar rotation, measuring sunspots and building a portable sundial. The YPOP Guestbook has been helpful in evaluating the usefulness of the site with over 300 detailed comments to date. Title: Arcade Structure and Dynamics in the 20-Jan-99 M5 Solar Flare Authors: McKenzie, D. E.; Hudson, H. S. Bibcode: 1999AAS...19410108M Altcode: 1999BAAS...31..999M We present observations of a remarkable solar flare which was observed by Yohkoh on 20-Jan-99. This long duration event is notable because the Yohkoh images show not only the formation of the arcade associated with the coronal mass ejection, but also a considerable amount of structure and motion in the current sheet above the arcade. Though not unique, the structure of this arcade is different from the majority of flare arcades observed by Yohkoh. The motions indicate field line shrinkage during the rise phase of the flare, and downward flow above the arcade during the decay phase. The late-phase downward motion suggests the possibility either of a high-Beta regime in the current sheet, or of shrinkage of evacuated flux tubes downward through the current sheet. This research is supported by NASA under MSFC contract NAS8-40801. Title: Crustal and Elastic Thickness Estimates for the Moon Authors: Nimmo, F.; McKenzie, D. Bibcode: 1999LPI....30.1325N Altcode: The crustal thickness of non-mascon lunar areas is about 45 km, assuming isostasy. The elastic thickness of the South Pole-Aitken Basin is about 5 km. These areas are weak, implying they must have formed early in the Moon's history. Title: A Stable Filament Cavity with a Hot Core Authors: Hudson, H. S.; Acton, L. W.; Harvey, K. L.; McKenzie, D. E. Bibcode: 1999ApJ...513L..83H Altcode: We present observations of a long-lived solar filament cavity with soft X-ray sources along its axis. This structure appeared above the southern polar crown polarity-inversion line for approximately three rotations during 1997 June-August, centered at a west-limb passage on approximately July 3. At the limb, the Yohkoh soft X-ray data showed a bright region situated above and around the projected filament location but near the axis of the cavity. We describe measurements of the geometry of the cavity, which we interpret as a flux rope that is partially embedded in the photosphere, and use the Yohkoh data to describe the physical parameters of the structure. We find that the core consists of an unresolved mass of filamentary substructures, with a volume filling factor significantly less than unity for the soft X-ray telescope (SXT) resolution. The core has a higher temperature than the cavity surrounding it, ruling out explanations in terms of a transition region supported by thermal conduction. Transient activity occurred in the polar crown region, but no detectable destabilization or eruption of the cavity structure resulted from it. We suggest that the bright structure at the core of the cavity corresponds to higher altitude coronal segments of the field lines that support the filament material. Title: Sigmoidal morphology and eruptive solar activity Authors: Canfield, Richard C.; Hudson, Hugh S.; McKenzie, David E. Bibcode: 1999GeoRL..26..627C Altcode: Soft X-ray images of solar active regions frequently show S- or inverse-S (sigmoidal) morphology. We have studied the Yohkoh Soft X-Ray Telescope video movie for 1993 and 1997. We have classified active regions according to morphology (sigmoidal or non-sigmoidal) and nature of activity (eruptive or non-eruptive). As well, we have used NOAA sunspot areas for each region as a measure of size. We find that regions are significantly more likely to be eruptive if they are either sigmoidal or large. Title: Deglaciation effects on mantle melting under Iceland: results from the northern volcanic zone Authors: Slater, L.; Jull, M.; McKenzie, D.; Gronvöld, K. Bibcode: 1998E&PSL.164..151S Altcode: A striking feature of Icelandic volcanism is the effect that the last ice age had on volcanic activity. After the final retreat of ice ∼11 kyr BP, the average eruption rate is estimated to have been 20-30 times greater than it is today. This increase has been attributed to the release of pooled magma through differential tectonic movements during the unloading of ice. However recent work has shown that deglaciation can account for the increase in mantle melting by decreasing the pressure in the upper mantle. We present geochemical data and volume estimates of erupted magmas from Iceland's northern neovolcanic zone which show that the average composition of magmas erupted during the last glacial period in Iceland are significantly more enriched in incompatible trace elements than postglacial and interglacial lavas. The difference in light rare earth element concentrations cannot be accounted for by liquid-crystal fractionation. Averaging the compositions of glacial and postglacial magmas also eliminates the likelihood that the compositional change is due to variations in source composition. An increase in mantle melting from deglaciation can account for both the magma eruption rate and observed changes in trace element concentrations. Finite transport times for magma to travel from the source region to the surface can be estimated from the delay in timing of the increased eruption rates and the end of the last glacial period. This gives transport times of about 1-3 kyr and is consistent with estimates from ( 226Ra/ 230Th) activity ratios measured in ocean island and mid-ocean ridge basalts. Title: A space-age portrait of the active sun Authors: McKenzie, David E.; Slater, Timothy F. Bibcode: 1998PhTea..36..403M Altcode: Recent observations from space observatories focused on high energy emission from the Sun has provided both exciting science and beautiful pictures, particularly in X-ray wavelengths. This manuscript is adapted from an invited Frontiers in Astronomy talk given at the AAPT Winter Meeting, New Orleans, January 1998 on current research in solar physics. Title: Modelling Plume-related Uplift, Gravity and Melting on Mars Authors: Nimmo, F.; McKenzie, D. Bibcode: 1998LPI....29.1783N Altcode: No abstract at ADS Title: Martian Dikes, Outflow Channels and Valles Marineris Authors: McKenzie, D.; Nimmo, F. Bibcode: 1998LPI....29.1778M Altcode: No abstract at ADS Title: Volcanism and Tectonics on Venus Authors: Nimmo, F.; McKenzie, D. Bibcode: 1998AREPS..26...23N Altcode: We review recent developments in the study of volcanism and tectonics on Venus. Venus's crust is basaltic, dry, and probably about 30~km thick. The mantle convects, giving rise to plumes, and has a similar composition and mean temperature (~1300 deg C), but a higher viscosity (~10^20 Pa s), than that of the Earth. Inferred melt generation rates constrain the lithospheric thickness to between 80 and 200 km. The elastic thickness of the lithosphere is about 30 km on average. The present-day lack of plate tectonics may be due to strong faults and the high viscosity of the mantle. Most of the differences between Earth and Venus processes can be explained by the absence of water. Venus underwent a global resurfacing event 300--600 Ma ago, the cause and nature of which remains uncertain. The present-day surface heat flux on Venus is about half the likely radiogenic heat generation rate, which suggests that Venus has been heating up since the resurfacing event. Title: Periodic Modulation of X-Ray Intensity from Coronal Loops - Heating by Resonant Absorption? Authors: McKenzie, D. E.; Mullan, D. J. Bibcode: 1997SoPh..176..127M Altcode: We have applied time-series analysis to sequences of coronal loop images obtained with the Yohkoh soft X-ray telescope (SXT). Using images obtained in fast-cadence mode (δ t = 4 s), we have generated X-ray light curves and power spectra for multiple subregions of a number of coronal loops. Our analysis indicates that out of 544 spectra of loops which range in length L from 40 Mm to 150 Mm, there are 16 cases where the X-ray brightness is modulated periodically with ≥99.5% confidence. The periods τ range from 9.6 s to 61.6 s, and the amplitudes range from 0.4% to 1.8%. Our result is statistically significant at the 8σ level. Title: Search for Periodicity in Image Sequences from YOHKOH Soft X-Ray Telescope Authors: McKenzie, David Eugene Bibcode: 1997PhDT.........9M Altcode: The process by which the Sun's corona is heated is not well known. A leading model is the resonant absorption of Alfvenic surface waves. In order to be efficient as a heating mechanism, this process depends on the surface waves being well matched to the length of the coronal loop through the condition of global-mode resonance: v Alfvén = 2L/period (Davila 1987). The Yohkoh Soft X-Ray Telescope provides a means of recording the behavior and evolution of structures in the solar corona. Relatively fast-cadence sequences of CCD images become movies depicting the changing conditions in the X-ray emitting regions. By using software provided by the Yohkoh science team to measure the brightness of a selected subset of pixels in all the images of a movie, we can generate an X-ray light curve of a small portion of a given coronal structure. For the present dissertation, a number of SXT image sequences were selected from the Yohkoh archives. Light curves were generated in the manner outlined above, and these light curves were then examined for periodic modulations. It is shown that periodic modulations of X-ray brightness were detected with amplitudes of about 1%, and that the speeds implied by global-mode resonance are in the neighborhood of 1800-14000 km/s, consistent with Alfven wave speeds but much higher than sound speeds implied by the temperatures measured from the images. The wave speeds and the modulation amplitudes imply plasma beta values in the range β p ≈ 10-3-10-2. Tests for correlations among physical conditions (loop length L, temperature T, pressure p, modulation depth ΔI/I, quality Q, and period τ) in the periodically modulated loops tentatively support relationships like T ~ (pL)1/3, after Rosner et al. (1978), and Q ~ (Δ I/I)-2, after Zaitsev & Stepanov (1989), but do not support relationships like L ~ τ,/ L ~ p,/ L ~ T, or p ~ τ. Title: Search for Periodicity in Image Sequences from the Yokoh Soft X-Ray Telescope Authors: McKenzie, D. E. Bibcode: 1997PASP..109..739M Altcode: The process by which the Sun's corona is heated is not well known. A leading model is the resonant absorption of Alfvénic surface waves. In order to be efficient as a heating mechanism, this process depends on the surface waves being well matched ot the length of the coronal loop through the condition of global-mode resonance: $v_{Alfv\acute{e}n}$ = 2L/period (Davila, 1987). The Yohkoh Soft X-Ray Telescope (SXT) provides a means of recording the behavior and evolution of structures in the solar corona. Relatively fast-cadence sequences of CCD images become movies depicting the changing conditions in the X-ray emitting regions. By using software provided by the Yohkoh science team to measure the brightness of a selected subset of pixels in all the images of a movie, we can generate an X-ray light curve of a small portion of a given coronal structure. For the present dissertation, a number of SXT image sequences were selected from the Yohkoh archives. Light curves were generated in the manner outlined above, and these light curves were then examined for periodic modulations. It is shown that periodic modulations of X-ray brightness were detected with amplitudes of nearly 1\%, and that the speeds inferred from interpreting these oscillations as global-mode resonance are in the neighborhood of 1800 -- 14000 km/s, consistent with Alfvén wave speeds but much higher than sound speeds implied by the temperatures measured from the images. The wave speeds and the modulation amplitudes imply plasma beta values in the range $\beta_p \approx 10^{-3} -- 10^{-2}$. (SECTION: Dissertation Summaries) Title: Search for Periodicity in Image Sequences from YOHKOH Soft X-Ray Telescope Authors: McKenzie, D. E. Bibcode: 1997SPD....28.0704M Altcode: 1997BAAS...29..911M We have applied time-series analysis to sequences of coronal loop images obtained with the Yohkoh Soft X-Ray Telescope (SXT). Using images obtained in fast-cadence mode (Delta t = 4 sec), we have generated X-ray light curves and power spectra for multiple subregions of a number of coronal loops. Our analysis indicates that out of 544 spectra of loops which range in length L from 40 Mm to 150 Mm, there are 16 cases where the X-ray brightness is modulated periodically with >=99.5% confidence. The periods tau range from 9.6 sec to 61.6 sec, and the amplitudes range from 0.4% to 1.8%. Our result is statistically significant at the 8sigma level. The observed periods can hardly be due to fluctuations in gas pressure: temperatures estimated from image ratios indicate sound speeds of 200 -- 280 km/sec, with loop crossing times of hundreds of seconds. On the other hand, the ratio 2 L / tau yields ``velocities" of 2 -- 14 Mm/sec: these overlap with published estimates of Alfven speeds v_A in coronal loops, 3.5 -- 37 Mm/sec (Schmelz et al., 1994, ApJ, 434, 786). Now, in the context of coronal loop heating by resonant absorption of MHD waves, the period tau_g ~ 2 L / v_A plays a key role: loops which are oscillating in their global mode (with period tau_g ) are maximally efficient at absorbing energy (Steinolfson and Davila, 1993, ApJ, 415, 354). We suggest that the loops which we have found to be modulated periodically are oscillating in their global mode. With this interpetation, we find that the plasma beta in the loops lies in the range beta _p = 0.001 -- 0.045. According to the oscillating loop model of Zaitsev and Stepanov (1989, Sov. Astron. Letters, 15, 66), loops with such beta _p values should be modulated with amplitudes of 1.1% or less: our data are consistent with at least the upper limit of this prediction. Title: Using the WWW to Make YOHKOH SXT Images Available to the Public: The YOHKOH Public Outreach Project Authors: Larson, M.; McKenzie, D.; Slater, T.; Acton, L.; Alexander, D.; Freeland, S.; Lemen, J.; Metcalf, T. Bibcode: 1997SPD....28.0231L Altcode: 1997BAAS...29..898L The Yohkoh Public Outreach Project (YPOP) is funded by NASA as one of the Information Infrastructure Technology and Applications Cooperative Agreement Teams to create public access to high quality Yohkoh SXT data via the World Wide Web. These products are being made available to the scientific research community, K-12 schools, and informal education centers including planetaria, museums, and libraries. The project aims to utilize the intrinsic excitement of the SXT data, and in particular the SXT movies, to develop science learning tools and classroom activities. The WWW site at URL: http://www.space.lockheed.com/YPOP/ uses a movie theater theme to highlight available Yohkoh movies in a non-intimidating and entertaining format for non-scientists. The site features lesson plans, 'solar' activities, slide shows and, of course, a variety of movies about the Sun. Classroom activities are currently undergoing development with a team of scientists and K-12 teachers for distribution in late 1997. We will display the products currently online, which include a solar classroom with activities for teachers, background resources, and a virtual tour of our Sun. Title: Using the World Wide Web to Make YOHKOH SXT Images Available to the Public: The YOHKOH Public Outreach Project Authors: McKenzie, D.; Larson, M. B.; Slater, T.; Acton, L.; Alexander, D.; Freeland, S.; Lemen, J.; Metcalf, T. Bibcode: 1997ESASP.404..561M Altcode: 1997cswn.conf..561M No abstract at ADS Title: Modeling plume-related melting, uplift and gravity on Venus Authors: Nimmo, F.; McKenzie, D. Bibcode: 1997E&PSL.145..109N Altcode: No abstract at ADS Title: Average lithospheric structure of southern Africa Authors: Qiu, X.; Priestley, K.; McKenzie, D. Bibcode: 1996GeoJI.127..563Q Altcode: No abstract at ADS Title: Magnetic Wave Resonance in Solar Coronal Structures Authors: McKenzie, D. E. Bibcode: 1995SPD....26..703M Altcode: 1995BAAS...27..966M No abstract at ADS Title: Ultralow temperature resonant-mass gravitational radiation detectors: current status of the Stanford program. Authors: Michelson, P. F.; Mann, L.; Penny, R.; Henderson, J.; McKenzie, D.; Zhou, C. Bibcode: 1995gwe..conf..195M Altcode: 1995grwa.conf..195M The main focus of the Stanford program during the past year has been on completing the design of a second generation resonant-mass detector designed to operate at 50 mK with an rms noise level for burst detection approaching h ≡ 10-20. The design is complete and final detector assembly is underway. It is expected to begin initial operation in the first quarter of next year. After establishing reliable operation of the new detector, the principal goal during the next few years is to operate it in coincidence with other gravitational radiation detectors including a similar ultralow temperature detector that has been constructed by the University of Rome. Improving energy sensitivity by about four orders-of-magnitude beyond that currently available from resonant-mass detectors (now routinely operating at 4 K) will be a major milestone for the field. Title: Radioactive disequilibria from 2D models of melt generation by plumes and ridges Authors: Richardson, C.; McKenzie, D. Bibcode: 1994E&PSL.128..425R Altcode: We present a simple method of calculating radiogenic excesses caused by the melting process in 2D models of melting regions. 238U series disequilibrium in basalt from recent Hawaiian eruptions can be explained using an axisymmetric plume model and a melt parameterisation based on laboratory experiments. The model is also applied to mid-ocean ridges and shows that the disequilibria are controlled by the mean melting rate at the base of the melting region and by the melt fraction present during melting. ( 230Th/235U) data constrains the mean melting rate at the onset of melting to less than 8 × 10 -8 yr -1, which is consistent with that expected from the experimental parameterisation. Limited ( 231Pa/235U) data give a maximum initial melting rate of 0.4 × 10 -8 yr -1. Melting begins in the garnet peridotite stability field and melt extraction is rapid ( ∼ 2000 yr). Extraction on this time scale is most easily explained if melt transport is by channel flow. The geochemical observations require the melt fraction in the region where U, Th and Ra are extracted from the source to be ∼ 0.1%, in agreement with estimates from a simple fluid dynamical model of melt separation. Title: Transient Period Found in the BY Dra Variable OU Geminorum Authors: McKenzie, D. E.; Herr, R. B. Bibcode: 1994IBVS.4014....1M Altcode: No abstract at ADS Title: Reply to the comment by R. Westaway on 'Active tectonics of the north and central Aegean Sea' by T. Taymaz, J. Jackson and D. McKenzie Authors: Taymaz, T.; Jackson, J.; McKenzie, D. Bibcode: 1992GeoJI.110..623T Altcode: No abstract at ADS Title: Venus Tectonics: Initial Analysis from Magellan Authors: Solomon, S. C.; Head, J. W.; Kaula, W. M.; McKenzie, D.; Parsons, B.; Phillips, R. J.; Schubert, G.; Talwani, M. Bibcode: 1991Sci...252..297S Altcode: Radar imaging and altimetry data from the Magellan mission have revealed a diversity of deformational features at a variety of spatial scales on the Venus surface. The plains record a superposition of different episodes of deformation and volcanism; strain is both areally distributed and concentrated into zones of extension and shortening. The common coherence of strain patterns over hundreds of kilometers implies that many features in the plains reflect a crustal response to mantle dynamic processes. Ridge belts and mountain belts represent successive degrees of lithospheric shortening and crustal thickening; the mountain belts also show widespread evidence for extension and collapse both during and following crustal compression. Venus displays two geometrical patterns of concentrated lithospheric extension: quasi-circular coronae and broad rises with linear rift zones; both are sites of significant volcanism. No long, large-offset strike-slip faults have been observed, although limited local horizontal shear is accommodated across many zones of crustal shortening. In general, tectonic features on Venus are unlike those in Earth's oceanic regions in that strain typically is distributed across broad zones that are one to a few hundred kilometers wide, and separated by stronger and less deformed blocks hundreds of kilometers in width, as in actively deforming continental regions on Earth. Title: Venus Tectonics: The Perspective from Magellan at the Half-way Point Authors: Solomon, S. C.; Head, J. W.; Kaula, W. M.; McKenzie, D.; Parsons, B. E.; Phillips, R. J.; Schubert, G.; Squyres, S. W.; Talwani, M. Bibcode: 1991LPI....22.1299S Altcode: No abstract at ADS Title: Tectonic Evolution of Lavinia Planitia, Venus Authors: Squyres, S. W.; Frank, S. L.; McGill, G. E.; McKenzie, D.; Parsons, B. E.; Solomon, S. C. Bibcode: 1991LPI....22.1309S Altcode: No abstract at ADS Title: Melt generation by plumes: A study of Hawaiian volcanism Authors: Watson, S.; McKenzie, D. Bibcode: 1991JPet...32..501W Altcode: No abstract at ADS Title: Ultralow temperature resonant-mass gravitational radiation detectors: current status and future prospects Authors: Michelson, P. F.; Aldcroft, T.; Chiang, J.; Debra, D.; Henderson, J.; Mann, L.; McKenzie, D.; McLoughlin, F.; Paik, H. J.; Penny, R.; Price, J. C.; Stevenson, T.; Vaughan, B.; Zhou, C.; Hansen, W. W. Bibcode: 1991gaid.conf...14M Altcode: No abstract at ADS Title: The volume and composition of melt generated by extension of the lithosphere Authors: McKenzie, D.; Bickle, M. J. Bibcode: 1988JPet...29..625M Altcode: No abstract at ADS Title: The existence of a thin low-viscosity layer beneath the lithosphere Authors: Craig, C. H.; McKenzie, D. Bibcode: 1986E&PSL..78..420C Altcode: The horizontal temperature gradient at the base of the lithosphere at an oceanic fracture zone, where plate of different ages is juxtaposed, is expected to drive a local circulation, the characteristics of which can be constrained by the amplitude, wavelength and age-dependence of the geoid. Two-dimensional numerical models of convection in a fluid layer overlain by a solid conducting lid have been used to generate theoretical geoid profiles at right angles to the fracture zone. Only a thin, low-viscosity layer provides a reasonable fit to the data. The best model so far obtained has a fluid layer 150 km thick with viscosity 1.5 × 10 19 Pa s under a 75 km lid. Such a layer, which is incapable of transmitting strong horizontal shear stresses, could provide the decoupling mechanism between plate and deep mantle flow required to balance the forces on the plates. Title: A possible mechanism for epeirogenic uplift Authors: McKenzie, D. Bibcode: 1984Natur.307..616M Altcode: Continental geology is dominated by vertical movements, some of these are the result of crustal shortening and extension associated with large horizontal displacements, involving processes which are now understood, at least in outline. However, both uplift and subsidence can occur without associated shortening or extension of the continental crust. Most investigations of such epeirogenic movements have been concerned with subsidence, partly because of the economic importance of the resulting sedimentary basins, and partly because of the existence of a simple model for the process1 which can account for the development of several basins in some detail2-4. However, uplift has been relatively neglected and cannot be produced by the same mechanism. The purpose of this paper is to examine whether epeirogenic uplift can result from the intrusion of large thicknesses of basic magma into the lower part of continental crust. This suggestion was considered as a possible mechanism for the regional uplift of the Colorado Plateau by Gilbert5 more than 100 years ago, and also by Holmes6 (though both rejected the idea). However, a recent discussion of no less than 14 different mechanisms for generating uplift7 did not include this process, even though it seems able to produce the observed vertical motions and also to account for some of the features of the evolution of sedimentary basins that cannot be explained by the uniform stretching model3,8,9. Although the suggestion is not new, the argument used here to support it is, and depends on an understanding of the relationship between ocean island volcanoes and mantle circulation. Title: The generation and compaction of partially molten rock Authors: McKenzie, D. Bibcode: 1984JPet....5..713M Altcode: No abstract at ADS Title: The depth of seismicity in the Kermanshah region of the Zagros Mountains (Iran) Authors: Niazi, M.; Asudeh, I.; Ballard, G.; Jackson, J.; King, G.; McKenzie, D. Bibcode: 1978E&PSL..40..270N Altcode: A detailed microearthquake survey in a small region of the Zagros Mountains in Iran failed to detect any shocks whose depths were greater than 20 km. One third of the shocks in the same area have depths greater than 50 km when located using teleseismic observations. Because of poor azimuthal coverage and lack of local stations these teleseismic locations are probably in error. There is therefore no reliable seismic evidence for the existence of oceanic lithosphere beneath the Zagros fold belt. Title: Surface deformation, gravity anomalies and convection. Authors: McKenzie, D. Bibcode: 1977GeoJ...48..211M Altcode: 1977GeoJI..48..211M No abstract at ADS Title: Geomagnetism in Marine Geology. V. Vacquier, 1972. Elsevier, Amsterdam, 1972, 200 pp., Ofl.42.50 Authors: McKenzie, D. Bibcode: 1973ESRv....9Q.289M Altcode: No abstract at ADS Title: A Comparison of Thermal and Non-thermal Solar Flare X-ray Emission Observed on OSO-7 Authors: Datlowe, D.; McKenzie, D. Bibcode: 1972BAAS....4Q.380D Altcode: No abstract at ADS Title: De-Occultation X-Ray Events of 2 December, 1967 Authors: Zirin, Harold; Ingham, William; Hudson, Hugh; McKenzie, David Bibcode: 1969SoPh....9..269Z Altcode: A flare rising from behind the solar limb was recorded simultaneously by the UCSD X-ray detector on OSO-III (7.7-200 keV) and the Caltech photoheliograph on Robinson Laboratory roof (Hα). The de-occultation gives excellent spatial resolution of the X-ray source. Spectra suggest that the material was already heated to 27 000 000° and that the increase in flux was due to the de-occultation. The flux rise to maximum was proportional to the apparent area. The uniformity of this rise shows that there was no special kernel of emission. Comparison of the deduced volume with the bremsstrahlung formula gives a density of about 1010 for the 27 000 000° component of the flare; this is confirmed by consideration of the maximum possible coulomb braking. The actual decay is more likely by escape rather than coulomb braking. Title: De-occultation x-Ray Event of 2 December 1967 Authors: Hudson, Hugh; McKenzie, David; Zirin, Harold; Ingham, William Bibcode: 1969BAAS....1T.280H Altcode: No abstract at ADS Title: The Upper Limit Solar Gamma-Ray Spectrum to 10 Mev Authors: Peterson, Laurence E.; Schwartz, Daniel A.; Pelling, R. M.; McKenzie, David Bibcode: 1966JGR....71.5778P Altcode: In this Letter we wish to report new upper limits on solar γ rays obtained from a balloon flight series in February 1966. These results, when combined with other recent work, form a composite upper-limit γ-ray spectrum from the quiet sun over the range 20 kev to 10 Mev, which is about a factor of 30 lower than that previously available. Since several experimental techniques were used to cover this large energy range, the results in the 20-200-kev range will be presented first, followed by the 1-10-Mev work. Upper limits in the 130-800-kev region are available from previous work [Frost et al., 1966].