Author name code: schmit ADS astronomy entries on 2022-09-14 =author:"Schmit, Donald" OR =author:"Schmit, Donald J." OR =author:"Schmit, D.J." ------------------------------------------------------------------------ Title: First Imaging Spectroscopy of 92-115 Angstrom Solar Soft X-rays by EUNIS: Implications for Solar Coronal Heating Authors: Brosius, Jeffrey; Daw, Adrian; Rabin, Douglas; Landi, Enrico; Schmit, Donald Bibcode: 2021AGUFMSH12B..04B Altcode: The Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS) sounding rocket waslaunched from White Sands Missile Range, NM, on May 18, 2021. The instrumentcomprised a pair of coaligned imaging spectrographs, one of which observed solarline emission in first order at wavelengths between 525 and 639 A, and the secondof which observed line emission in third order at wavelengths between 92 and 115 Aand in first order between 277 and 345 A. Images of AR 12824, quiet-sun area, andoff-limb area were obtained by rastering the slits over the selected targets. Thisis the first time that solar imaging spectroscopy has been performed in the 92-115A soft X-ray range. This waveband was selected to (1) observe Fe XVIII 93.932 and103.948 A and Fe XIX 108.355 A line emission in a quiescent active region, and (2)explore a relatively unobserved portion of the solar electromagnetic spectrum. Theinstrument performed well during its 6-minute observing run. We report preliminaryresults on observations of Fe XVIII and Fe XIX in the quiescent active region, anddiscuss implications for the nanoflare model of solar coronal heating. EUNIS wassupported by NASA Heliophysics Low Cost Access to Space award 13-HTIDS13_2-0074. Title: A Novel Integral Field Spectrograph Design for taking High-Cadence Spectral Solar Images: SNIFS Authors: Knoer, Vicki; Chamberlin, Phillip; Daw, Adrian; Gong, Qian; Milligan, Ryan; Polito, Vanessa; Schmit, Donald Bibcode: 2021AGUFMSH55B1837K Altcode: Many features on the sun such as flares and nanoflares are highly dynamic and change over the course of seconds. This is at least an order of magnitude faster than our current ability to 2D spectrally image the sun. This difference in time scale has made it difficult to study some of the sun's faster-changing features. The newly designed Solar eruptioN Integral Field Spectrograph (SNIFS) is an extreme ultraviolet (EUV) integral field spectrograph which will be able to take spectral images of the sun at a 1 second time cadence. The game-changing innovations which allow a faster cadence include a fast-readout CMOS detector and an array of mirrorlets to focus the incoming light into a square array spatial pixels, the spectrum for each of which will be measured simultaneously. The optical path is doubled in order to view both active network and flaring sun. This new optical design will allow high-cadence spectral imaging of the sun which will contribute to our understanding of energy and mass transport in the chromosphere and transition region. 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: The Solar eruptioN Integral Field Spectrograph (SNIFS) Sounding Rocket Authors: Chamberlin, P. C.; Schmit, D. J.; Daw, A. N.; Polito, V.; Gong, Q.; Milligan, R. O. Bibcode: 2020AGUFMSH056..03C Altcode: The lower solar atmosphere is temporally dynamic and spatially inhomogeneous, and it is becoming increasingly clear that this complex activity must be measured and quantified if we are to fully understand how mass and energy are transported into the corona. The Solar eruptioN Integral Field Spectrograph (SNIFS) sounding rocket is designed to break new ground by using a unique set of capabilities to probe the most vexingly complex region of the solar atmosphere, the chromosphere. Hydrogen Lyman-alpha (Ly-α; 121.6 nm) is the brightest line in the solar UV spectrum, it is energetically one of the most important. Using radiation transfer models, we can use the observed line profiles to reconstruct the transit of these photon through the solar atmosphere and understand the plasma from which they came. SNIFS will observe not only Ly-ɑ, but the nearby Si III and O V emissions, two transition regions lines that allow us to observe how the chromosphere connects with upper atmosphere. The SNIFS rocket mission has a primary objective to explore the energetics and dynamics of chromosphere using a next-generation solar spectral imager.

SNIFS will be the first of its kind: a solar ultraviolet integral field spectrograph (IFS; Chamberlin and Gong, 2016). SNIFS technology will revolutionize solar observations by obtaining high cadence 3D information simultaneously: two spatial dimensions and one spectral dimensions.SNIFS utilizes a novel optical design to simultaneously observe a 32 x 32 arcsec field of view with 0.45 arcsec pixels, with a spectral resolution of 66mÅ and at 1 s cadence. The SNIFS design employs, for the first time in a spaceflight instrument as a technology development, a 72x72 element 2D array of reflecting and focusing mirrorlets, allowing IFS concepts to move down into EUV wavelengths. This mirrorlet array is placed at the imaging plane of the telescope, similar to the location of a slit in a traditional imaging slit-spectrometer design. After the mirrorlet in the optical path, a focusing grating will then produce a high-resolution spectrum for each spatial element defined by the mirrorlet elements. SNIFS's IFS technology is truly a game-changing instrument needed for future solar physics missions, and was recently selected and funded by NASA to fly in Spring of 2024. Title: What Is the Source of Quiet Sun Transition Region Emission? Authors: Schmit, D. J.; De Pontieu, Bart Bibcode: 2016ApJ...831..158S Altcode: 2016arXiv160807620S Dating back to the first observations of the on-disk corona, there has been a qualitative link between the photosphere’s magnetic network and enhanced transition-temperature plasma emission. These observations led to the development of a general model that describes emission structures through the partitioning of the atmospheric volume with different magnetic loop geometries that exhibit different energetic equilibria. Does the internetwork produce transition-temperature emission? What fraction of network flux connects to the corona? How does quiet Sun emission compare with low-activity Sun-like stars? In this work, we revisit the canonical model of the quiet Sun, with high-resolution observations from the Interface Region Imaging Spectrograph (IRIS) and HMI in hand, to address those questions. We use over 900 deep exposures of Si IV 1393 Å from IRIS along with nearly simultaneous HMI magnetograms to quantify the correlation between transition-temperature emission structures and magnetic field concentrations through a number of novel statistics. Our observational results are coupled with analysis of the Bifrost MHD model and a large-scale potential field model. Our results paint a complex portrait of the quiet Sun. We measure an emission signature in the distant internetwork that cannot be attributed to network contribution. We find that the dimmest regions of emission are not linked to the local vertical magnetic field. Using the MHD simulation, we categorize the emission contribution from cool mid-altitude loops and high-altitude coronal loops and discuss the potential emission contribution of spicules. Our results provide new constraints on the coupled solar atmosphere so that we can build on our understanding of how dynamic thermal and magnetic structures generate the observed phenomena in the transition region. Title: Connecting Photospheric Magnetic Fields and Transition Temperature Plasma Emission Authors: Schmit, Donald Bibcode: 2016SPD....47.0332S Altcode: The connectivity of quiet sun magnetic fields is not well understood. One observational obstacle to probe this question has been the sparse spectral observations spanning the transition temperatures (3×104 K< T < 1×105K) between the chromosphere and corona. The Si IV lines observed by IRIS provide a rich dataset to address the structure of the cool quiet sun. We use over 900 deep exposures from IRIS to map the correlation between transition-temperature emission structures and magnetic field concentrations. Ultimately, our aim is to discern the topology and energetic equilibrium of the magnetic structures that span the quiet sun. We use both a potential field model and a snapshot of the Bifrost 3D MHD simulation to interpret our emission data. In a broad sense, we find there is a clear correlation between magnetic fields and strong Si IV emission. However, more pointed statistics suggest that the relationship is quite complex. We do not find evidence for cool loops longer than 3 Mm in length, but we see ubiquitous, smooth emission nearly everywhere in the quiet sun. Emission voids on scales larger than 8 Mm cannot be well explained by their proximity to magnetic fields. This evidence suggests that weak-field transition-temperature loops contribute significantly to quiet sun transition-temperature emission measure, and evolutionary effects likely play a role in structuring the magnetic atmosphere. Title: Cool Plasma Observed in the FUV using IRIS Authors: Schmit, D. J.; Innes, D. Bibcode: 2014AGUFMSH51C4177S Altcode: Cool plasma in the outer solar atmosphere is commonly observed in prominences and coronal rain. Theory suggests that these phenomena are related to cooling, and analysis of observations provides a constraint on the time-dependent energetics of the chromosphere and corona. Using the IRIS SG and SJI datasets, we discuss new observations of molecular absorption features in the Si IV emission lines near 1400A. The presence of molecules above the transition region provides an extreme example of complex structure and dynamics at the chromosphere-corona interface. There are two morphological models that can explain the absorption features: cool plasma hundreds of kilometers above the photosphere or a localized transition region deeply embedded in the photosphere. We discuss the merit of these scenarios and introduce complementary IRIS observations of inverted temperature structure in Ellerman bombs and diffuse Si I continuum absorption above active region loops. Title: Molecular absorption in transition region spectral lines Authors: Schmit, D. J.; Innes, D.; Ayres, T.; Peter, H.; Curdt, W.; Jaeggli, S. Bibcode: 2014A&A...569L...7S Altcode: 2014arXiv1409.1702S
Aims: We present observations from the Interface Region Imaging Spectrograph (IRIS) of absorption features from a multitude of cool atomic and molecular lines within the profiles of Si IV transition region lines. Many of these spectral lines have not previously been detected in solar spectra.
Methods: We examined spectra taken from deep exposures of plage on 12 October 2013. We observed unique absorption spectra over a magnetic element which is bright in transition region line emission and the ultraviolet continuum. We compared the absorption spectra with emission spectra that is likely related to fluorescence.
Results: The absorption features require a population of sub-5000 K plasma to exist above the transition region. This peculiar stratification is an extreme deviation from the canonical structure of the chromosphere-corona boundary. The cool material is not associated with a filament or discernible coronal rain. This suggests that molecules may form in the upper solar atmosphere on small spatial scales and introduces a new complexity into our understanding of solar thermal structure. It lends credence to previous numerical studies that found evidence for elevated pockets of cool gas in the chromosphere.

Movies associated to Figs. 1 and 2 are available in electronic form at http://www.aanda.org Title: On the Structure and Evolution of a Polar Crown Prominence/Filament System Authors: Panesar, N. K.; Innes, D. E.; Schmit, D. J.; Tiwari, S. K. Bibcode: 2014SoPh..289.2971P Altcode: 2014arXiv1402.4989P; 2014SoPh..tmp...50P Polar crown prominences, that partially circle the Sun's poles between 60° and 70° latitude, are made of chromospheric plasma. We aim to diagnose the 3D dynamics of a polar crown prominence using high-cadence EUV images from the Solar Dynamics Observatory (SDO)/AIA at 304, 171, and 193 Å and the Ahead spacecraft of the Solar Terrestrial Relations Observatory (STEREO-A)/EUVI at 195 Å. Using time series across specific structures, we compare flows across the disk in 195 Å with the prominence dynamics seen on the limb. The densest prominence material forms vertical columns that are separated by many tens of Mm and connected by dynamic bridges of plasma that are clearly visible in 304/171 Å two-colour images. We also observe intermittent but repetitious flows with velocity 15 km s−1 in the prominence that appear to be associated with EUV bright points on the solar disk. The boundary between the prominence and the overlying cavity appears as a sharp edge. We discuss the structure of the coronal cavity seen both above and around the prominence. SDO/HMI and GONG magnetograms are used to infer the underlying magnetic topology. The evolution and structure of the prominence with respect to the magnetic field seems to agree with the filament-linkage model. Title: Jets and Bombs: Characterizing IRIS Spectra Authors: Schmit, Donald; Innes, Davina Bibcode: 2014AAS...22432309S Altcode: For almost two decades, SUMER has provided an unique perspective on explosive events in the lower solar atmosphere. One of the hallmark observations during this tenure is the identification of quiet sun bi-directional jets in the lower transition region. We investigate these events through two distinct avenues of study: a MHD model for reconnection and the new datasets of the Interface Region Imaging Spectrograph (IRIS). Based on forward modeling optically thin spectral profiles, we find the spectral signatures of reconnection can vary dramatically based on viewing angle and altitude. We look to the IRIS data to provide a more complete context of the chromospheric and coronal environment during these dynamic events. During a joint IRIS-SUMER observing campaign, we observed spectra of multiple jets, a small C flare, and an Ellerman bomb event. We discuss the questions that arise from the inspection of these new data. Title: The Formation of a Cavity in a 3D Flux Rope Authors: Schmit, Donald; Gibson, Sarah Bibcode: 2014IAUS..300..147S Altcode: 2013arXiv1311.2384S There are currently no three dimensional numerical models which describe the magnetic and energetic formation of prominences self-consistently. Consequently, there has not been significant progress made in understanding the connection between the dense prominence plasma and the coronal cavity. We have taken an ad-hoc approach to understanding the energetic implications of the magnetic models of prominence structure. We extract one dimensional magnetic field lines from a 3D MHD model of a flux rope and solve for hydrostatic balance along these field lines incorporating field-aligned thermal conduction, uniform heating, and radiative losses. The 1D hydrostatic solutions for density and temperature are then mapped back into three dimensional space, which allows us to consider the projection of multiple structures. We find that the 3D flux rope is composed of several distinct field line types. A majority of the flux rope interior field lines are twisted but not dipped. These field lines are density-reduced relative to unsheared arcade field lines. We suggest the cavity may form along these short interior field lines which are surrounded by a sheath of dipped field lines. This geometric arrangement would create a cavity on top of a prominence, but the two structures would not share field lines or plasma. Title: Prominence Mass Supply and the Cavity Authors: Schmit, Donald J.; Gibson, S.; Luna, M.; Karpen, J.; Innes, D. Bibcode: 2013ApJ...779..156S Altcode: 2013arXiv1311.2382S A prevalent but untested paradigm is often used to describe the prominence-cavity system: the cavity is under-dense because it is evacuated by supplying mass to the condensed prominence. The thermal non-equilibrium (TNE) model of prominence formation offers a theoretical framework to predict the thermodynamic evolution of the prominence and the surrounding corona. We examine the evidence for a prominence-cavity connection by comparing the TNE model with diagnostics of dynamic extreme ultraviolet (EUV) emission surrounding the prominence, specifically prominence horns. Horns are correlated extensions of prominence plasma and coronal plasma which appear to connect the prominence and cavity. The TNE model predicts that large-scale brightenings will occur in the Solar Dynamics Observatory Atmospheric Imaging Assembly 171 Å bandpass near the prominence that are associated with the cooling phase of condensation formation. In our simulations, variations in the magnitude of footpoint heating lead to variations in the duration, spatial scale, and temporal offset between emission enhancements in the other EUV bandpasses. While these predictions match well a subset of the horn observations, the range of variations in the observed structures is not captured by the model. We discuss the implications of our one-dimensional loop simulations for the three-dimensional time-averaged equilibrium in the prominence and the cavity. Evidence suggests that horns are likely caused by condensing prominence plasma, but the larger question of whether this process produces a density-depleted cavity requires a more tightly constrained model of heating and better knowledge of the associated magnetic structure. Title: Diagnosing the Prominence-Cavity Connection Authors: Schmit, Donald J.; Gibson, Sarah Bibcode: 2013ApJ...770...35S Altcode: 2013arXiv1304.7595S Prominences and cavities are ubiquitously observed together, but the physical link between these disparate structures has not been established. We address this issue by using dynamic emission in the extreme ultraviolet to probe the connections of these structures. The SDO/AIA observations show that the cavity exhibits excessive emission variability compared to the surrounding quiet-Sun streamer, particularly in the 171 Å bandpass. We find that this dynamic emission takes the form of coherent loop-like brightening structures which emanate from the prominence into the central cavity. The geometry of these structures, dubbed prominence horns, generally mimics the curvature of the cavity boundary. We use a space-time statistical analysis of two cavities in multiple AIA bandpasses to constrain the energetic properties of 45 horns. In general, we find there is a positive correlation between the light curves of the horns in the 171 Å and 193 Å bandpasses; however, the 193 Å emission is a factor of five weaker. There is also a strong correlation between structural changes to the prominence as viewed in the He II 304 Å bandpass and the enhanced 171 Å emission. In that bandpass, the prominence appears to extend several megameters along the 171 Å horn where we observe co-spatial, co-temporal 304 Å and 171 Å emission dynamics. We present these observations as evidence of the magnetic and energetic connection between the prominence and the cavity. Further modeling work is necessary to explain the physical source and consequences of these events, particularly in the context of the traditional paradigm: the cavity is underdense because it supplies mass to the overdense prominence. Title: Magnetic structure and flows in coronal prominence cavities Authors: Gibson, S. E.; Bak-Steslicka, U.; Forland, B.; Schmit, D. J. Bibcode: 2013AGUSMSH23B..04G Altcode: Prominence cavities provide deep insight into the storage and release of magnetic energy in the solar corona. Recent studies have yielded a variety of observations that provide new constraints on models of prominences, cavities, and coronal mass ejections. In particular, a survey of SDO/AIA extreme-ultraviolet cavities has demonstrated that a tear-shaped morphology is a predictor of impending eruption, indicating that a change in topology may play a role in their destabilization. Other studies utilizing extreme-ultraviolet and infrared observations have shown both circulating plane-of-sky flows and a "bulls-eye" pattern in line-of-sight flows within cavities, indicating a central magnetic axis. A comparison of coronal flows within the cavity and flows associated with the embedded prominence demonstrate both spatial and temporal correlations, indicating they are both magnetically and thermodynamically connected. Finally, coronal magnetometric observations show a characteristic "rabbit-head" signature in linear polarization within polar-crown-prominence cavities, indicating twisted or sheared magnetic field at the heart of the cavity. All of these observations lend credence to the model of the cavity as a magnetic flux rope: both as a long-lived MHD equilibrium state and as a key component in the ultimate destabilization and eruption of coronal mass ejections. Title: Temperature and Extreme-ultraviolet Intensity in a Coronal Prominence Cavity and Streamer Authors: Kucera, T. A.; Gibson, S. E.; Schmit, D. J.; Landi, E.; Tripathi, D. Bibcode: 2012ApJ...757...73K Altcode: We analyze the temperature and EUV line emission of a coronal cavity and surrounding streamer in terms of a morphological forward model. We use a series of iron line ratios observed with the Hinode Extreme-ultraviolet Imaging Spectrograph (EIS) on 2007 August 9 to constrain temperature as a function of altitude in a morphological forward model of the streamer and cavity. We also compare model predictions to the EIS EUV line intensities and polarized brightness (pB) data from the Mauna Loa Solar Observatory (MLSO) Mark 4 K-coronameter. This work builds on earlier analysis using the same model to determine geometry of and density in the same cavity and streamer. The fit to the data with altitude-dependent temperature profiles indicates that both the streamer and cavity have temperatures in the range 1.4-1.7 MK. However, the cavity exhibits substantial substructure such that the altitude-dependent temperature profile is not sufficient to completely model conditions in the cavity. Coronal prominence cavities are structured by magnetism so clues to this structure are to be found in their plasma properties. These temperature substructures are likely related to structures in the cavity magnetic field. Furthermore, we find that the model overestimates the EUV line intensities by a factor of 4-10, without overestimating pB. We discuss this difference in terms of filling factors and uncertainties in density diagnostics and elemental abundances. Title: Diagnosing the Prominence-Cavity Connection Authors: Schmit, Donald; Gibson, S. Bibcode: 2012AAS...22052102S Altcode: Prominences are regions of cool, dense plasma which are suspended above the solar limb within the much hotter and more rarefied solar corona. The coronal environment surrounding the prominence is often observed as a elliptical region of reduced density (compared to the ambient corona) known as a cavity. To date, the cavity has been a neglected constraint on the prominence system. In this research, I probe the magnetic structural connection between the cavity and prominence and the potential role the cavity plays in the mass and energy balance of the prominence. Observationally, I use the Hinode/EIS and SDO/AIA datasets to extract dynamic substructure from the cavity. The temperature-sensitivities of these data are used to diagnose the interaction of plasma in the prominence and in the surrounding corona.These observational dynamics present a viable constraint on prominence models in two ways. Structurally, the morphology of the extract substructure can be compared to the 3D models of prominence support. Energetically, the spatial and temporal signature of EUV dynamics can be compared to the thermal non-equilibrium model for prominence mass supply. This joint approach systematically addresses the two largest questions in prominence research: how is the prominence mass supported and where does it come from. Title: Temperature Structure of a Coronal Cavity and Streamer Authors: Kucera, Therese A.; Gibson, S. E.; Schmit, D. J.; Landi, E.; Tripathi, D. Bibcode: 2012AAS...22052113K Altcode: We analyze the temperature and EUV line emission of a coronal cavity and surrounding streamer in terms of a morphological forward model. We use a series of iron line ratios observed with the Hinode Extreme-ultraviolet Imaging Spectrograph (EIS) on 2007 Aug. 9 to constrain temperature as a function of altitude in a morphological forward model of the streamer and cavity. We also compare model prediction of the EIS EUV line intensities and polarized brightness (pB) data from the Mauna Loa Solar Observatory (MLSO) MK4. This work builds on earlier analysis using the same model to determine geometry of and density in the same cavity and streamer (Gibson et al. 2010 and Schmit and Gibson 2011). The fit to the data with altitude dependent temperature profiles indicates that both the streamer and cavity have temperatures in the range 1.4-1.7 MK. However, the cavity exhibits substantial substructure such that the altitude dependent temperature profile is not sufficient to completely model conditions in the cavity. This work is supported in part by the NASA SHP program Title: Diagnosing the Prominence-Cavity Connection Authors: Schmit, Donald; Gibson, Sarah Bibcode: 2012decs.confE...7S Altcode: Prominences are regions of cool, dense plasma which are suspended above the solar limb within the much hotter and more rarefied solar corona. The coronal environment surrounding the prominence is often observed as an elliptical region of reduced density (compared to the ambient corona) known as a cavity. The fundamental problems in prominence physics are the magnetic support of condensed plasma and the mass-source of those condensations. We use the SDO/AIA dataset to probe the correlated dynamics in between the cool prominence and the coronal cavity. These dynamics are explained through the 1D modeling of the radiative instability. The magnetic field inferred from these dynamics is also compared to the 3D MHD models of prominence support. Through this joint approach, the dynamic nature of the prominence system is brought into sharp focus for the first time. Title: Diagnosing the Prominence-Cavity Connection in the Solar Corona Authors: Schmit, D. J. Bibcode: 2012PhDT.......416S Altcode: The energetic equilibrium of the corona is described by a balance of heating, thermal conduction, and radiative cooling. Prominences can be described by the thermal instability of coronal energy balance which leads to the formation of cool condensations. Observationally, the prominence is surrounded by a density depleted elliptical structure known as a cavity. In this dissertation, we use extreme ultraviolet remote sensing observations of the prominence-cavity system to diagnose the static and dynamic properties of these structures. The observations are compared with numerical models for the time-dependent coronal condensation process and the time-independent corona-prominence magnetic field. To diagnose the density of the cavity, we construct a three-dimensional structural model of the corona. This structural model allows us to synthesize extreme ultraviolet emission in the corona in a way that incorporates the projection effects which arise from the optically thin plasma. This forward model technique is used to constrain a radial density profile simultaneously in the cavity and the streamer. We use a χ2 minimization to find the density model which best matches a density sensitive line ratio (observed with Hinode/Extreme ultraviolet Imaging Spectrometer) and the white light scattered intensity (observed with Mauna Loa Solar Observatory MK4 coronagraph). We use extreme ultraviolet spectra and spectral images to diagnose the dynamics of the prominence and the surrounding corona. Based on the doppler shift of extreme ultraviolet coronal emission lines, we find that there are large regions of flowing plasma which appear to occur within cavities. These line of sight flows have speeds of 10 km/s-1 and projected spatial scales of 100 Mm. Using the Solar Dynamics Observatory Atmospheric Imaging Assembly (SDO/AIA) dataset, we observe dynamic emission from the prominence-cavity system. The SDO/AIA dataset observes multiple spectral bandpasses with different temperature sensitivities. Time-dependent changes in the observed emission in these bandpass images represent changes in the thermodynamic properties of the emitting plasma. We find that the coronal region surrounding the prominence exhibits larger intensity variations (over tens of hours of observations) as compared to the streamer region. This variability is particularly strong in the cool coronal emission of the 171Å bandpass. We identify the source of this variability as strong brightening events that resemble concave-up loop segments and extend from the cool prominence plasma. Magnetic field lines are the basic structural building block of the corona. Energy and pressure balance in the corona occur along magnetic field lines. The large-scale extreme ultraviolet emission we observe in the corona is a conglomerate of many coronal loops projected along a line of sight. In order to calculate the plasma properties at a particular point in the corona, we use one-dimensional models for energy and pressure balance along field lines. In order to predict the extreme ultraviolet emission along a particular line of sight, we project these one-dimensional models onto the three-dimensional magnetic configuration provided by a MHD model for the coronal magnetic field. These results have allowed us to the establish the first comprehensive picture on the magnetic and energetic interaction of the prominence and the cavity. While the originally hypothesis that the cavity supplies mass to the prominence proved inaccurate, we cannot simply say that these structures are not related. Rather our findings suggest that the prominence and the cavity are distinct magnetic substructures that are complementary regions of a larger whole, specifically a magnetic flux rope. (Abstract shortened by UMI.). Title: Diagnosing the Prominence-Cavity Connection Authors: Schmit, D. J.; Gibson, S. E. Bibcode: 2011AGUFMSH43B1947S Altcode: The magnetic field is thought to play a central role in both the support of prominence plasma as well as the thermodynamic isolation of the surrounding cavity. We use the statistical goldmine of the SDO/AIA dataset to probe for the first time the dynamical link between these related structures. These observations are compared to the 3D magnetic geometries predicted by MHD models. The dynamic features are explained within the context of 1D field-aligned momentum and energy imbalance. Title: Forward Modeling Cavity Density: A Multi-instrument Diagnostic Authors: Schmit, D. J.; Gibson, S. E. Bibcode: 2011ApJ...733....1S Altcode: The thermodynamic properties of coronal prominence cavities present a unique probe into the energy and mass budget of prominences. Using a three-dimensional morphological model, we forward model the polarization brightness and extreme-ultraviolet (EUV) emission of a cavity and its surrounding streamer. Using a genetic algorithm, we find the best-fit density model by comparing the models to Mauna Loa Solar Observatory MK4 and Hinode EUV Imaging Spectrometer data. The effect of temperature variations on the derived density is also measured. We have measured the density inside a cavity down to 1.05 R sun with height-dependent error bars. Our forward modeling technique compensates for optically thin projection effects. This method provides a complementary technique to traditional line ratio diagnostics that is useful for diffuse off-limb coronal structures. Title: Temperature Structure of a Coronal Cavity Authors: Kucera, Therese A.; Gibson, S. E.; Schmit, D. J. Bibcode: 2011SPD....42.1833K Altcode: 2011BAAS..43S.1833K We analyze the temperature structure of a coronal cavity observed in Aug. 2007. Coronal cavities are long, low-density structures located over filament neutral lines and are often seen as dark elliptical features at the solar limb in white light, EUV and X-rays. When these structures erupt they form the cavity portions of CMEs. It is important to establish the temperature structure of cavities in order to understand the thermodynamics of cavities in relation to their three-dimensional magnetic structure.

To analyze the temperature we compare temperature ratios of a series of iron lines observed by the Hinode/EUV Imaging Spectrometer (EIS). We also use those lines to constrain a forward model of the emission from the cavity and streamer. The model assumes a coronal streamer with a tunnel-like cavity with elliptical cross-section and a Gaussian variation of height along the tunnel length. Temperature and density can be varied as a function of altitude both in the cavity and streamer. The general cavity morphology and the cavity and streamer density have already been modeled using data from STEREO's SECCHI/EUVI and Hinode/EIS (Gibson et al 2010 and Schmit & Gibson 2011). Title: Three-dimensional morphology of a coronal prominence cavity Authors: Gibson, S. E.; Kucera, T. A.; Rastawicki, D.; Dove, J.; de Toma, G.; Hao, J.; Hill, S. M.; Hudson, H. S.; Marque, C.; McIntosh, P. S.; Rachmeler, L.; Reeves, K. K.; Schmieder, B.; Schmit, D. J.; Sterling, A.; Tripathi, D.; Williams, D. R.; Zhang, M. Bibcode: 2010AGUFMSH51A1667G Altcode: We present a three-dimensional density model of coronal prominence cavities, and a morphological fit that has been tightly constrained by a uniquely well-observed cavity. Observations were obtained as part of an International Heliophysical Year campaign by instruments from a variety of space- and ground-based observatories, spanning wavelengths from radio to soft-X-ray to integrated white light. From these data it is clear that the prominence cavity is the limb manifestation of a longitudinally-extended polar-crown filament channel, and that the cavity is a region of low density relative to the surrounding corona. As a first step towards quantifying density and temperature from campaign spectroscopic data, we establish the three-dimensional morphology of the cavity. This is critical for taking line-of-sight projection effects into account, since cavities are not localized in the plane of the sky and the corona is optically thin. We have augmented a global coronal streamer model to include a tunnel-like cavity with elliptical cross-section and a Gaussian variation of height along the tunnel length. We have developed a semi-automated routine that fits ellipses to cross-sections of the cavity as it rotates past the solar limb, and have applied it to Extreme Ultraviolet Imager (EUVI) observations from the two Solar Terrestrial Relations Observatory (STEREO) spacecraft. This defines the morphological parameters of our model, from which we reproduce forward-modeled cavity observables. We find that cavity morphology and orientation, in combination with the viewpoints of the observing spacecraft, explains the observed variation in cavity visibility for the east vs. west limbs. Title: Three-dimensional Morphology of a Coronal Prominence Cavity Authors: Gibson, S. E.; Kucera, T. A.; Rastawicki, D.; Dove, J.; de Toma, G.; Hao, J.; Hill, S.; Hudson, H. S.; Marqué, C.; McIntosh, P. S.; Rachmeler, L.; Reeves, K. K.; Schmieder, B.; Schmit, D. J.; Seaton, D. B.; Sterling, A. C.; Tripathi, D.; Williams, D. R.; Zhang, M. Bibcode: 2010ApJ...724.1133G Altcode: We present a three-dimensional density model of coronal prominence cavities, and a morphological fit that has been tightly constrained by a uniquely well-observed cavity. Observations were obtained as part of an International Heliophysical Year campaign by instruments from a variety of space- and ground-based observatories, spanning wavelengths from radio to soft X-ray to integrated white light. From these data it is clear that the prominence cavity is the limb manifestation of a longitudinally extended polar-crown filament channel, and that the cavity is a region of low density relative to the surrounding corona. As a first step toward quantifying density and temperature from campaign spectroscopic data, we establish the three-dimensional morphology of the cavity. This is critical for taking line-of-sight projection effects into account, since cavities are not localized in the plane of the sky and the corona is optically thin. We have augmented a global coronal streamer model to include a tunnel-like cavity with elliptical cross-section and a Gaussian variation of height along the tunnel length. We have developed a semi-automated routine that fits ellipses to cross-sections of the cavity as it rotates past the solar limb, and have applied it to Extreme Ultraviolet Imager observations from the two Solar Terrestrial Relations Observatory spacecraft. This defines the morphological parameters of our model, from which we reproduce forward-modeled cavity observables. We find that cavity morphology and orientation, in combination with the viewpoints of the observing spacecraft, explain the observed variation in cavity visibility for the east versus west limbs. Title: Space Based Observations of Coronal Cavities in Conjunction with the Total Solar Eclipse of July 2010 Authors: Kucera, T. A.; Berger, T. E.; Boerner, P.; Dietzel, M.; Druckmuller, M.; Gibson, S. E.; Habbal, S. R.; Morgan, H.; Reeves, K. K.; Schmit, D. J.; Seaton, D. B. Bibcode: 2010AGUFMSH51A1666K Altcode: In conjunction with the total solar eclipse on July 11, 2010 we coordinated a campaign between ground and space based observations. Our specific goal was to augment the ground based measurement of coronal prominence cavity temperatures made using iron lines in the IR (Habbal et al. 2010 ApJ 719 1362) with measurements performed by space based instruments. Included in the campaign were Hinode/EIS, XRT and SOT, PROBA2/SWAP, SDO/AIA, SOHO/CDS and STEREO/SECCHI/EUVI, in addition to the ground based IR measurements. We plan to use a combination of line ratio and forward modeling techniques to investigate the density and temperature structure of the cavities at that time. Title: Density Diagnostics in Cavities: Incorporating and Bypassing Projection Effects Authors: Schmit, D. J.; Gibson, S. E.; Kucera, T. A. Bibcode: 2010AGUFMSH51A1668S Altcode: The highly ionized corona emits strongly in EUV atomic emission lines. Comparison of relative emission in various lines provides the temperature and density of the coronal plasma. We use an Fe XII line ratio to probe the density of a prominence cavity at heights generally only accessible to spectroscopic instruments. We take a novel approach in this diagnostic by fully accounting for the 3D structure of the corona so as to compensate for the projection effects in optical thin emission. The density inside the cavity and the streamer are constrained using a forward model where in emission is synthesized with CHIANTI. The synthetic emission and scattering is compared to Hinode/EIS and MLSO MKIV data. A least squares minimization is conducted using a genetic algorithm. In particular, this work addresses the degree to which we can answer the question, “Is there a density jump at all heights?”. Title: Flows and Plasma Properties in Quiescent Cavities Authors: Schmit, Donald; Gibson, Sarah Bibcode: 2009shin.confE.116S Altcode: Regions of rarefied density often form cavities above quiescent prominences. In an attempt to constrain the plasma properties of Title: Large-Scale Flows in Prominence Cavities Authors: Schmit, D. J.; Gibson, S. E.; Tomczyk, S.; Reeves, K. K.; Sterling, Alphonse C.; Brooks, D. H.; Williams, D. R.; Tripathi, D. Bibcode: 2009ApJ...700L..96S Altcode: Regions of rarefied density often form cavities above quiescent prominences. We observed two different cavities with the Coronal Multichannel Polarimeter on 2005 April 21 and with Hinode/EIS on 2008 November 8. Inside both of these cavities, we find coherent velocity structures based on spectral Doppler shifts. These flows have speeds of 5-10 km s-1, occur over length scales of tens of megameters, and persist for at least 1 hr. Flows in cavities are an example of the nonstatic nature of quiescent structures in the solar atmosphere. Title: A novel metric for coronal MHD models Authors: Schmit, D. J.; Gibson, S.; de Toma, G.; Wiltberger, M.; Hughes, W. J.; Spence, H.; Riley, P.; Linker, J. A.; Mikic, Z. Bibcode: 2009JGRA..114.6101S Altcode: 2009JGRA..11406101S In the interest of quantitatively assessing the capabilities of coronal MHD models, we have developed a metric that compares the structures of the white light corona observed with SOHO LASCO C2 to model predictions. The MAS model is compared to C2 observations from two Carrington rotations during solar cycle 23, CR1913 and CR1984, which were near the minimum and maximum of solar activity, respectively, for three radial heights, 2.5 R $\odot$ , 3.0 R $\odot$ , and 4.5 R $\odot$ . In addition to simulated polarization brightness images, we create a synthetic image based on the field topology along the line of sight in the model. This open-closed brightness is also compared to LASCO C2 after renormalization. In general, the model's magnetic structure is a closer match to observed coronal structures than the model's density structure. This is expected from the simplified energy equations used in current global corona MHD models. Title: Flows and Plasma Properties in Quiescent Cavities Authors: Schmit, Donald; Gibson, S.; Reeves, K.; Sterling, A.; Tomczyk, S. Bibcode: 2009SPD....40.1015S Altcode: Regions of rarefied density often form cavities above quiescent prominences. In an attempt to constrain the plasma properties of "equilibrium" cavities we conduct several diagnostics using Hinode/EIS, STEREO/EUVI, and CoMP. One novel observation is of large scale flows in cavities. Using different instruments to observe two distinct cavities off the solar limb in coronal emission lines, we find that spectral doppler shifts imply LOS velocities within cavities on the order of 1-10 km/s. These flows occur over length scales of several hundred Mm and persist for hours. Title: Multi-wavelength Comparison of Prominence Cavities Authors: Schmit, D. J.; Gibson, S.; de Toma, G.; Reeves, K.; Tripathi, D.; Kucera, T.; Marque, C.; Tomczyk, S. Bibcode: 2008AGUSMSP43B..04S Altcode: Recent observational campaigns have brought together a wealth of data specifically designed to explore the physical properties and dynamics of prominence cavities. In particular, STEREO and Hinode data have provided new perspectives on these structures. In order to effectively analyze the data in a cohesive manner, we produce overlays of several distinct and complimentary datasets including SOHO UVCS, CDS, and EIT, Hinode SOT and EIS, STEREO SECCHI, TRACE, and Nancay Radioheliograph data as well as new observations of coronal magnetic fields in cavities from the Coronal Multichannel Polarimeter. We are thus able to investigate how sensitive morphology is to the wavelength observed which details the nature of the plasma in the cavity.