Author name code: schad ADS astronomy entries on 2022-09-14 author:"Schad, Thomas Antony" ------------------------------------------------------------------------ Title: Ground-based instrumentation and observational techniques Authors: Rimmele, Thomas; Kuhn, Jeff; Woeger, Friedrich; Tritschler, . Alexandra; Lin, Haosheng; Casini, Roberto; Schad, Thomas; Jaeggli, Sarah; de Wijn, Alfred; Fehlmann, Andre; Anan, Tetsu; Schmidt, Dirk Bibcode: 2022cosp...44.2507R Altcode: We'll review the current state-of-the-art for ground-based instrumentation and techniques to achieve high-resolution observations. We'll use the 4m Daniel K. Inouye Solar Telescope (DKIST), the European Solar Telescope (EST) and other ground-based instrumentation as examples to demonstrate instrument designs and observing techniques. Using adaptive optics and post-facto image processing techniques, the recently completed DKIST provides unprecedented resolution and high polarimetric sensitivity that enables astronomers to unravel many of the mysteries the Sun presents, including the origin of solar magnetism, the mechanisms of coronal heating and drivers of flares and coronal mass ejections. Versatile ground-based instruments provide highly sensitive measurements of solar magnetic fields, that in the case of DKIST, also include measurements of the illusive magnetic field of the faint solar corona. Ground-based instruments produce large and diverse data sets that require complex calibration and data processing to provide science-ready to a broad community. We'll briefly touch on ongoing and future instrumentation developments, including multi-conjugate adaptive optics. Title: Science Commissioning of the Diffraction-Limited Near-IR Spectropolarimter for the Daniel K. Inouye Solar Telescope Authors: Lin, Haosheng; Schad, Thomas; Kramar, Maxim; Jaeggli, Sarah; Anan, Tetsu; Onaka, Peter Bibcode: 2022cosp...44.2508L Altcode: The Diffraction-Limited Near-IR Spectropolarimeter (DL-NIRSP) is one of the first-generation facility instruments of the Daniel K. Inouye Solar Telescope (DKIST, or The Inouye Solar Telescope). It is a near-IR spectropolarimeter optimized to study the magnetism of the dynamic solar atmosphere, from the photosphere to the corona. DL-NIRSP is equipped with two integral field units (IFUs) coupled to a high-resolution grating spectrograph, and is capable of simultaneous measurements of the full polarized spectra of a 2-dimensional spatial field without scanning. Large field of view observations are supported by mosaicking. DL-NIRSP observes simultaneously at three spectral windows, enabling simultaneous coverage of different atmospheric layers with carefully selected spectral lines. It can also observe the Sun with three resolution modes, from diffraction-limited observations with a spatial sampling of 0.03" to wide-field mode covering a 32"x15" instantaneous FOV with 0.5" sampling. This paper will present results from science commissioning observations conducted in late 2021. Title: Thomson Scattering above Solar Active Regions and an Ad Hoc Polarization Correction Method for the Emissive Corona Authors: Schad, Thomas A.; Jaeggli, Sarah A.; Dima, Gabriel I. Bibcode: 2022ApJ...933...53S Altcode: 2022arXiv220509808S Thomson-scattered photospheric light is the dominant constituent of the lower solar corona's spectral continuum viewed off-limb at optical wavelengths. Known as the K-corona, it is also linearly polarized. We investigate the possibility of using the a priori polarized characteristics of the K-corona, together with polarized emission lines, to measure and correct instrument-induced polarized crosstalk. First we derive the Stokes parameters of the Thomson scattering of unpolarized light in an irreducible spherical tensor formalism. This allows forward synthesis of the Thomson-scattered signal for the more complex scenario that includes symmetry-breaking features in the incident radiation field, which could limit the accuracy of our proposed technique. For this, we make use of an advanced 3D radiative magnetohydrodynamic coronal model. Together with synthesized polarized signals in the Fe XIII 10746 Å emission line, we find that an ad hoc correction of telescope- and instrument-induced polarization crosstalk is possible under the assumption of a nondepolarizing optical system. Title: A Model-based Technique for Ad Hoc Correction of Instrumental Polarization in Solar Spectropolarimetry Authors: Jaeggli, Sarah A.; Schad, Thomas A.; Tarr, Lucas A.; Harrington, David M. Bibcode: 2022ApJ...930..132J Altcode: 2022arXiv220403732J We present a new approach for correcting instrumental polarization by modeling the nondepolarizing effects of a complex series of optical elements to determine physically realizable Mueller matrices. Provided that the Mueller matrix of the optical system can be decomposed into a general elliptical diattenuator and general elliptical retarder, it is possible to model the crosstalk between both the polarized and unpolarized states of the Stokes vector and then use the acquired science observations to determine the best-fit free parameters. Here we implement a minimization for solar spectropolarimetric measurements containing photospheric spectral lines sensitive to the Zeeman effect using physical constraints provided by polarized line and continuum formation. This model-based approach is able to provide an accurate correction even in the presence of large amounts of polarization crosstalk and conserves the physically meaningful magnitude of the Stokes vector, a significant improvement over previous ad hoc techniques. Title: Polarized forbidden coronal line emission in the presence of active regions Authors: Schad, Thomas; Dima, Gabriel Bibcode: 2021AGUFMSH15G2087S Altcode: Photoexcited forbidden lines at visible and infrared wavelengths provide important diagnostics for the coronal magnetic field via scattering induced polarization and the Zeeman Effect. In forward models, the polarized formation of these lines is often treated assuming a simplified exciting radiation field, consisting only of the photospheric quiet-sun continuum, which is both cylindrically-symmetric relative to the solar vertical and unpolarized. Near active regions in particular, this assumption breaks down, especially due to the presence of sunspots and other surface features that lead to additional asymmetries in the continuum radiation field. Here we investigate the role of symmetry-breaking on the emergent polarized emission within high resolution models of the active corona simulated by the MURaM code. We treat the full 3D (unpolarized) continuum radiation field of the photosphere exciting the coronal ions and compare the cases that include and ignore the symmetry-breaking effects of the photospheric features. Our discussion focuses on the key observables soon to be made available by the National Science Foundation's Daniel K Inouye Solar Telescope. The results indicate that while symmetry breaking can in principle have a large effect, its role is relatively minor for the simulated active region largely due to the low inherent polarization fraction emitted by forbidden lines in denser active region plasmas. Title: pycelp: Python package for Coronal Emission Line Polarization Authors: Schad, T. A.; Dima, G. I. Bibcode: 2021ascl.soft12001S Altcode: pyCELP (aka "pi-KELP") calculates Coronal Emission Line Polarization. It forward synthesizes the polarized emission of ionized atoms formed in the solar corona and calculates the atomic density matrix elements for a single ion under coronal equilibrium conditions and excited by a prescribed radiation field and thermal collisions. pyCELP solves a set of statistical equilibrium equations in the spherical statistical tensor representation for a multi-level atom for the no-coherence case. This approximation is useful in the case of forbidden line emission by visible and infrared lines, such as Fe XIII 1074.7 nm and Si X 3934 nm. Title: Chromospheric Heating Mechanisms in a Plage Region Constrained by Comparison of Magnetic Field and Mg II h & k Flux Measurements with Theoretical Studies Authors: Anan, Tetsu; Schad, Thomas; Kitai, Reizaburo; Dima, Gabriel; Jaeggli, Sarah; Tarr, Lucas; Collados, Manuel; Dominguez-Tagle, Carlos; Kleint, Lucia Bibcode: 2021AGUFMSH44A..05A Altcode: The strongest quasi-steady heating in the solar atmosphere from the photosphere through the corona occurs in plage regions. As many chromospheric heating mechanisms have been proposed, important discriminators of the possible mechanisms are the location of the heating and the correlation between the magnetic field properties in the chromosphere and the local heating rate. We observed a plage region with the He I 1083.0 nm and Si I 1082.7 nm lines on 2018 October 3 using the integral field unit mode of the GREGOR Infrared Spectrograph (GRIS) installed at the GREGOR telescope. During the GRIS observation, the Interface Region Imaging Spectrograph (IRIS) obtained spectra of the ultraviolet Mg II h & k doublet emitted from the same region. In the periphery of the plage region, within the limited field of view seen by GRIS, we find that the Mg II radiative flux increases with the magnetic field in the chromosphere. The positive correlation implies that magnetic flux tubes can be heated by Alfvén wave turbulence or by collisions between ions and neutral atoms relating to Alfvén waves. Within the plage region itself, the radiative flux was large between patches of strong magnetic field strength in the photosphere, or at the edges of magnetic patches. On the other hand, we do not find any significant spatial correlation between the enhanced radiative flux and the chromospheric magnetic field strength or the electric current. In addition to the Alfvén wave turbulence or collisions between ions and neutral atoms relating to Alfvén waves, other heating mechanisms related to magnetic field perturbations produced by interactions of magnetic flux tubes could be at work in the plage chromosphere. Title: Measurements of Photospheric and Chromospheric Magnetic Field Structures Associated with Chromospheric Heating over a Solar Plage Region Authors: Anan, Tetsu; Schad, Thomas A.; Kitai, Reizaburo; Dima, Gabriel I.; Jaeggli, Sarah A.; Tarr, Lucas A.; Collados, Manuel; Dominguez-Tagle, Carlos; Kleint, Lucia Bibcode: 2021ApJ...921...39A Altcode: 2021arXiv210807907A In order to investigate the relation between magnetic structures and the signatures of heating in plage regions, we observed a plage region with the He I 1083.0 nm and Si I 1082.7 nm lines on 2018 October 3 using the integral field unit mode of the GREGOR Infrared Spectrograph (GRIS) installed at the GREGOR telescope. During the GRIS observation, the Interface Region Imaging Spectrograph obtained spectra of the ultraviolet Mg II doublet emitted from the same region. In the periphery of the plage region, within the limited field of view seen by GRIS, we find that the Mg II radiative flux increases with the magnetic field in the chromosphere with a factor of proportionality of 2.38 × 104 erg cm-2 s-1 G-1. The positive correlation implies that magnetic flux tubes can be heated by Alfvén wave turbulence or by collisions between ions and neutral atoms relating to Alfvén waves. Within the plage region itself, the radiative flux was large between patches of strong magnetic field strength in the photosphere or at the edges of magnetic patches. On the other hand, we do not find any significant spatial correlation between the enhanced radiative flux and the chromospheric magnetic field strength or the electric current. In addition to the Alfvén wave turbulence or collisions between ions and neutral atoms relating to Alfvén waves, other heating mechanisms related to magnetic field perturbations produced by interactions of magnetic flux tubes could be at work in the plage chromosphere. Title: Polarized Forbidden Coronal Line Emission in the Presence of Active Regions Authors: Schad, Thomas; Dima, Gabriel Bibcode: 2021SoPh..296..166S Altcode: Photoexcited forbidden lines at visible and infrared wavelengths provide important diagnostics for the coronal magnetic field via scattering induced polarization and the Zeeman effect. In forward models, the polarized formation of these lines is often treated assuming a simplified exciting radiation field consisting only of the photospheric quiet-Sun continuum, which is both cylindrically-symmetric relative to the solar vertical and unpolarized. In particular, this assumption breaks down near active regions, especially due to the presence of sunspots and other surface features that modify the strength and anisotropy of the continuum radiation field. Here we investigate the role of symmetry-breaking on the emergent polarized emission in high resolution models of the active corona simulated with the MURaM code. We treat the full 3D unpolarized continuum radiation field of the photosphere that excites the coronal ions and compare the cases where the symmetry-breaking effects of the photospheric features are included or ignored. Our discussion focuses on the key observables soon to be available by the National Science Foundation's Daniel K Inouye Solar Telescope. The results indicate that while symmetry breaking can in principle have a large effect, its role is relatively minor for the simulated active region, largely due to the low inherent polarization fraction emitted by forbidden lines in denser active region plasmas. Title: He I Spectropolarimetry of a Supersonic Coronal Downflow Within a Sunspot Umbra Authors: Schad, Thomas A.; Dima, Gabriel I.; Anan, Tetsu Bibcode: 2021ApJ...916....5S Altcode: We report spectropolarimetric observations of a supersonic downflow impacting the lower atmosphere within a large sunspot umbra. This work is an extension of Schad et al. using observations acquired in the He I 10830 Å triplet by the Facility Infrared Spectropolarimeter. Downflowing material accelerating along a cooled coronal loop reaches peak speeds near 200 km s-1 and exhibits both high speed emission and absorption within the umbra, which we determine to be a consequence of the strong height dependence of the radiatively controlled source function above the sunspot umbra. Strong emission profiles close to the rest wavelengths but with long redshifted tails are also observed at the downflow terminus. From the polarized spectra, we infer longitudinal magnetic field strengths of ~2.4 kG in the core portion of the He I strong emission, which we believe is the strongest ever reported in this line. Photospheric field strengths along the same line of sight are ~2.8 kG as inferred using the Ca I 10839 Å spectral line. The temperatures of the highest speed He I absorption and the near-rest emission are similar (~10 kK), while a differential emission measure analysis using Solar Dynamics Observatory/Atmospheric Imaging Assembly data indicates significant increases in radiative cooling for temperatures between ~0.5 and 1 MK plasma associated with the downflow terminus. Combined we interpret these observations in the context of a strong radiative shock induced by the supersonic downflow impacting the low sunspot atmosphere. Title: The National Science Foundation's Daniel K. Inouye Solar Telescope — Status Update Authors: Rimmele, T.; Woeger, F.; Tritschler, A.; Casini, R.; de Wijn, A.; Fehlmann, A.; Harrington, D.; Jaeggli, S.; Anan, T.; Beck, C.; Cauzzi, G.; Schad, T.; Criscuoli, S.; Davey, A.; Lin, H.; Kuhn, J.; Rast, M.; Goode, P.; Knoelker, M.; Rosner, R.; von der Luehe, O.; Mathioudakis, M.; Dkist Team Bibcode: 2021AAS...23810601R Altcode: The National Science Foundation's 4m Daniel K. Inouye Solar Telescope (DKIST) on Haleakala, Maui is now the largest solar telescope in the world. DKIST's superb resolution and polarimetric sensitivity will enable astronomers to unravel many of the mysteries the Sun presents, including the origin of solar magnetism, the mechanisms of coronal heating and drivers of flares and coronal mass ejections. Five instruments, four of which provide highly sensitive measurements of solar magnetic fields, including the illusive magnetic field of the faint solar corona. The DKIST instruments will produce large and complex data sets, which will be distributed through the NSO/DKIST Data Center. DKIST has achieved first engineering solar light in December of 2019. Due to COVID the start of the operations commissioning phase is delayed and is now expected for fall of 2021. We present a status update for the construction effort and progress with the operations commissioning phase. Title: Forward Synthesis Of The Active Corona In DKIST Coronal Lines Authors: Schad, T.; Dima, G. Bibcode: 2021AAS...23832801S Altcode: Large aperture coronagraphic spectropolarimeters offer unique possibilities to study the off-limb corona using polarized diagnostics, including those that probe the ill-measured coronal magnetic field properties. Here, we investigate the formation of the prime coronal lines targeted by US National Science Foundation's Daniel K Inouye Solar Telescope. We synthesize observables through advanced, high-resolution, and finely-structured, 3D MURaM coronal simulations. To do so, we have built and optimized Python-based synthesis modules that calculate the polarized line emission for multi-level atoms including the role of electron and proton collisions. We provide detailed benchmarks of these modules, in specific against tools provided by the Chianti team (in the scalar limit), both to validate the code and provide a primer for the line-dependent aspects of the polarization formation. The synthetic maps allow us to describe and predict polarized features within the array of multi-wavelength observables available. In addition, we comment on the opportunities provided for, as well as the challenges faced by, the analysis of the apparent polarized fine structures. Title: Possibilities and limitations of single-point coronal magnetometry based on multi-line spectropolarimetric observations Authors: Dima, G. I.; Schad, T. Bibcode: 2021AAS...23832810D Altcode: Emission from the solar corona in the visible and infrared is dominated by magnetic dipole (M1) emission lines. The magnetic and thermal properties of the coronal plasma influence the polarized properties of M1 lines and offer an opportunity to directly measure the coronal magnetic field. While the optically thin nature of the coronal plasma requires careful interpretation of observations, some differentiated coronal structures, like coronal loops, may offer opportunities for 'single-point' inversions to work. Generalizing the analytical formalism of the 'single-point' inversion approach introduced by Plowman (2014) for the Fe XIII 10747 / 10798 Å line pair, we show that some combinations of M1 lines contain degenerate spectropolarimetric information which prohibits their application for this technique. Combining polarized atomic modeling based on coronal loop properties with a sensitivity analysis based on photon noise, we discuss using the Fe XIII 10747 Å, Si X 14301 Å line pair as one alternative combination for implementing this technique. We show that at noise levels around 10-4 of the line intensity, magnetic fields with sufficient strength (~25 G) and not severely inclined to the line-of-sight (<35º) can be recovered using this method. The DKIST will feasibly reach such low noise levels while taking spectropolarimetric observations of multiple coronal emission lines at spatial resolutions close to 1 arcsec, comparable to space-based observatories. Title: A Coronal Downflow Induced Radiative Shock In A Sunspot Umbra Observed With He I Spectropolarimetry Authors: Schad, T. A.; Dima, G.; Anan, T. Bibcode: 2021AAS...23812703S Altcode: Downward directed energy deposition into sunspot umbrae may be an important contributor to the energetics of the umbral transition region (TR) and upper chromosphere. Supersonic downflows, and their association with TR bright dots, are now more routinely studied by NASA's Interface Region Imaging Spectrograph. Observations that trace the impact of these flows into the lower chromosphere and perhaps lower are less frequent. Here we report unique spectropolarimetric observations of a supersonic downflow using the He I 1083 nm triplet observed using the Facility Infrared Spectropolarimeter at the Dunn Solar Telescope. We observe downflows reaching speeds near 200 km/s into a sunspot umbra that present both high-speed absorption and emission profiles. At the downflow terminus, we also observe a sharp transition from supersonic speeds to near-rest speeds, which are connected by extended redshifted line wings of the near-stationary component. Careful analysis, correcting for straylight, and using spectropolarimetric inversions, provide a detailed picture of what we interpret as a strong radiative shock in the sunspot umbra. In particular, we find evidence of very strong magnetic field strengths in the post-shocked flow that suggests the flow penetrates into the deeper umbral atmosphere. Title: Magnetic field structures associated with chromospheric heating in a plage region Authors: Anan, T.; Schad, T.; Kitai, R.; Dima, G.; Jaeggli, S.; Collados, M.; Dominguez-Tagle, C.; Kleint, L. Bibcode: 2021AAS...23821222A Altcode: The strongest quasi-steady heating in the solar atmosphere occurs in the active chromosphere and in particular within plage regions. Our aim is to investigate the relation between magnetic structures and the signatures of heating in the plage regions so as to clarify what mechanisms are at work. We observed a plage region in NOAA active region 12723 in the near infrared He I triplet and Si I 1082.7 nm on 2018 October 3 using the Integral Field Unit mode of the GREGOR Infrared Spectrograph (GRIS) installed at the GREGOR telescope. At the same time, the Interface Region Imaging Spectrograph (IRIS) obtained spectra in the ultra-violet Mg II h & k doublet emitted from the same region. We applied the HAnle and ZEeman Light v2.0 inversion code (HAZEL v2.0) to the GRIS data to infer the photospheric and chromospheric magnetic field. We find that the radiative flux of the Mg II was large between patches of strong magnetic field strength in the photosphere, or at edges of the magnetic patches. On the other hand, the spatial correspondences between the Mg II flux and the magnetic field strength in the chromosphere and between the Mg II flux and the electric current are not so clear. In conclusion, chromospheric heatings in the plage region can be related to magnetic field perturbations produced by interactions of magnetic flux tubes. Title: He I spectropolarimetry of a supersonic coronal downflow within a sunspot umbra Authors: Schad, Thomas A.; Dima, Gabriel I.; Anan, Tetsu Bibcode: 2021arXiv210512853S Altcode: We report spectropolarimetric observations of a supersonic downflow impacting the lower atmosphere within a large sunspot umbra. This work is an extension of Schad et al. 2016 using observations acquired in the He I 10830 Angstrom triplet by the Facility Infrared Spectropolarimeter. Downflowing material accelerating along a cooled coronal loop reaches peak speeds near 200 km s$^{-1}$ and exhibits both high speed emission and absorption within the umbra, which we determine to be a consequence of the strong height dependence of the radiatively-controlled source function above the sunspot umbra. Strong emission profiles close to the rest wavelengths but with long red-shifted tails are also observed at the downflow terminus. From the polarized spectra, we infer longitudinal magnetic field strengths of ${\sim}2.4$ kG in the core portion of the He I strong emission, which we believe is the strongest ever reported in this line. Photospheric field strengths along the same line-of-sight are ${\sim}2.8$ kG as inferred using the Ca I 10839 Angstrom spectral line. The temperatures of the highest speed He I absorption and the near rest emission are similar (${\sim}$10 kK), while a differential emission measure analysis using SDO/AIA data indicates significant increases in radiative cooling for temperatures between $\sim$0.5 and 1 MK plasma associated with the downflow terminus. Combined we interpret these observations in the context of a strong radiative shock induced by the supersonic downflow impacting the low sunspot atmosphere. 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: Single-point coronal magnetometry using multi-line spectropolarimetric observations Authors: Dima, Gabriel; Schad, Thomas Bibcode: 2021cosp...43E1788D Altcode: The US National Science Foundation's Daniel K Inouye Solar Telescope (DKIST) will soon provide large-aperture coronagraphic observations of polarized coronal emission lines in the visible and infrared spectrum at spatial resolutions close to 1 arcsec, comparable to space-based observatories. Polarized via coherent scattering and the Zeeman Effect, the targeted emission lines hold diagnostic potential for the hard-to-measure coronal magnetic field. DKIST provides the requisite advances in spatial resolution, spectral coverage, and polarimetric sensitivity in these lines to advance our understand of coronal magnetic structure; however, techniques for inferring the field parameters from the observations require careful consideration. Here we discuss a technique that combines two or more magnetic-dipole (M1) coronal lines to infer the vector components of the coronal magnetic field that do not require detailed knowledge of the other intrinsic plasma state variables. Generalizing the analytical formalism of the 'single-point' inversion approach introduced by Plowman (2014) we show that some combinations of M1 lines contain degenerate spectropolarimetric information which prohibits their application for this technique. This may include the pair of Fe XIII 10747, 10797 Å emission lines originally proposed by Plowman. Through a sensitivity analysis based on photon noise and polarized atomic modeling based on coronal loop properties, we discuss using the Fe XIII 10747 Å, Si X 14301 Å line pair as one alternative combination for implementing this technique. We find that for noise levels around 10$^{-4}$ of the line intensity, which will be available with DKIST, magnetic fields with sufficient strength ($\sim$25 G) and not severely inclined to the line-of-sight (<35$^\circ$) can be recovered with this method. We discuss potential targets for this method and limitations for it's applicability. Title: Remote sensing the thermal evolution and magnetic conditions within coronal thermal nonequilibrium events using ground-based large-aperture coronagraphic polarimetry Authors: Schad, Thomas Bibcode: 2021cosp...43E.988S Altcode: The solar atmosphere provides an unparalleled opportunity to study the detailed processes governing the onset and evolution of thermal instabilities in magnetized plasmas. Spectral imaging and polarimetric capabilities made available by ground-based large-aperture (coronagraphic) telescopes, in particular the soon-to-be commissioned US National Science Foundation's Daniel K Inouye Solar Telescope (DKIST), provide enhanced diagnostics of the thermal evolution and, uniquely, the magnetic conditions within coronal thermal nonequilibrium events. Here we demonstrate, using measurements from the MLSO/HAO CoMP instrument, the potential of linear polarized measurements of forbidden magnetic-dipole transitions of highly ionized species for studying the temporal evolution of temperature and density within unstable (cooling) loops. In addition, we show how DKIST linear and circular polarized measurements of these lines will provide the possibility for measuring the magnetic field conditions within the hot loops. As the thermal instability progresses in such structures and coronal rain is formed, the enhanced emission within permitted lines like He I and Ca II allow very detailed imaging of the rain parcels in addition to significant advantages for polarimetric measurements of coronal magnetism. In some cases, such rain events can be observed on-disk and traced directly to the lower atmosphere wherein the influence of the lower atmosphere's evolution on the instability might be assessed. DKIST provides a very flexible multi-instrument suite capable of taking advantage of these many diagnostics of thermal stabilities from the ground, and here we comment on specific strategies for observations. Title: New polarized views of the neutral and ionized solar corona using the US NSF's Daniel K Inouye Solar Telescope Authors: Schad, Thomas; Dima, Gabriel Bibcode: 2021cosp...43E1789S Altcode: This year's commissioning of the US National Science Foundation's 4-meter aperture Daniel K Inouye Solar Telescope (DKIST) on the island of Maui, in Hawaii, revolutionizes our view of the dynamic finely-structured solar corona in at least two important ways. First, its unprecedented spatial resolving power within the solar photosphere affords our most detailed view yet of the footpoints of coronal structures as we endeavor to understand the nature of the convective and magnetic drivers of coronal loop energetics. And second, the capabilities it provides off-limb for conducting low-scattered light, multi-wavelength spectropolarimetry of primarily highly ionized species opens up new remote diagnostic of magnetism directly in the corona, not only providing critical constraints for the large-scale configuration of active regions but also the possibility to study scaling relations between the magnetic field and localized heating and cooling. The challenges involved in interpreting these optically thin polarized diagnostics can be severe, as we will summarize; however, we also demonstrate via observations and simulations the power of multi-spectral diagnostics, and in particular, the value of neutral helium formation during corona rain events that make high-resolution coronal polarimetry of individuated structures a real possibility made available for the first time by the large-aperture coronagraphy of the DKIST. Title: DKIST and Advances in Chromospheric Polarimetry: Connecting the Trees with the Forest Authors: Schad, T. A. Bibcode: 2020AGUFMSH004..04S Altcode: The chromosphere is comprised of a wondrous taxonomy of multi-scaled dynamic phenomena. Together, localized features like jets, jet-lets, fibrils, and spicules, in congress with a vigorous and evolving wave field, create a rich interconnected forest. Indeed, observers have often remarked how spicules extending from the limb appear like a forest of trees, and on-disk, analogous references to fibril canopies are often invoked. Characterizing these basic chromospheric constituents requires highly advanced instrumentation pushing the boundaries of spatial, spectral, and temporal resolution. Yet, pushing for such a microscopic view is not a case of not seeing the forest for the trees. These dynamic features trace important, yet poorly understood, physical processes that are responsible for transporting significant energy from the sun's magnetized convection and depositing it throughout the global chromosphere. A key challenge is to connect the energy budget on local scales with that of the global chromosphere an d lower corona. The US National Science Foundation's Daniel K Inouye Solar Telescope (DKIST) is at the forefront of this observational effort. DKIST provides an extremely versatile facility designed from the ground-up to enable high-speed, multi-channel imaging, slit- and imaging-based spectroscopy and spectropolarimetry at the highest resolutions available. It is uniquely positioned to leverage recent advances in chromospheric polarimetry for inferring the magnetic fields and electric fields in chromospheric plasmas. Early operations start soon, and we are already seeing glimpses of the promise of DKIST. This talk will discuss the exciting opportunities provided by its first light instrument suite, in particular, to study non-equilibrium and non-ideal MHD effects in the Sun's chromospheric forest. Title: The Daniel K. Inouye Solar Telescope - Observatory Overview Authors: Rimmele, Thomas R.; Warner, Mark; Keil, Stephen L.; Goode, Philip R.; Knölker, Michael; Kuhn, Jeffrey R.; Rosner, Robert R.; McMullin, Joseph P.; Casini, Roberto; Lin, Haosheng; Wöger, Friedrich; von der Lühe, Oskar; Tritschler, Alexandra; Davey, Alisdair; de Wijn, Alfred; Elmore, David F.; Fehlmann, André; Harrington, David M.; Jaeggli, Sarah A.; Rast, Mark P.; Schad, Thomas A.; Schmidt, Wolfgang; Mathioudakis, Mihalis; Mickey, Donald L.; Anan, Tetsu; Beck, Christian; Marshall, Heather K.; Jeffers, Paul F.; Oschmann, Jacobus M.; Beard, Andrew; Berst, David C.; Cowan, Bruce A.; Craig, Simon C.; Cross, Eric; Cummings, Bryan K.; Donnelly, Colleen; de Vanssay, Jean-Benoit; Eigenbrot, Arthur D.; Ferayorni, Andrew; Foster, Christopher; Galapon, Chriselle Ann; Gedrites, Christopher; Gonzales, Kerry; Goodrich, Bret D.; Gregory, Brian S.; Guzman, Stephanie S.; Guzzo, Stephen; Hegwer, Steve; Hubbard, Robert P.; Hubbard, John R.; Johansson, Erik M.; Johnson, Luke C.; Liang, Chen; Liang, Mary; McQuillen, Isaac; Mayer, Christopher; Newman, Karl; Onodera, Brialyn; Phelps, LeEllen; Puentes, Myles M.; Richards, Christopher; Rimmele, Lukas M.; Sekulic, Predrag; Shimko, Stephan R.; Simison, Brett E.; Smith, Brett; Starman, Erik; Sueoka, Stacey R.; Summers, Richard T.; Szabo, Aimee; Szabo, Louis; Wampler, Stephen B.; Williams, Timothy R.; White, Charles Bibcode: 2020SoPh..295..172R Altcode: We present an overview of the National Science Foundation's Daniel K. Inouye Solar Telescope (DKIST), its instruments, and support facilities. The 4 m aperture DKIST provides the highest-resolution observations of the Sun ever achieved. The large aperture of DKIST combined with state-of-the-art instrumentation provide the sensitivity to measure the vector magnetic field in the chromosphere and in the faint corona, i.e. for the first time with DKIST we will be able to measure and study the most important free-energy source in the outer solar atmosphere - the coronal magnetic field. Over its operational lifetime DKIST will advance our knowledge of fundamental astronomical processes, including highly dynamic solar eruptions that are at the source of space-weather events that impact our technological society. Design and construction of DKIST took over two decades. DKIST implements a fast (f/2), off-axis Gregorian optical design. The maximum available field-of-view is 5 arcmin. A complex thermal-control system was implemented in order to remove at prime focus the majority of the 13 kW collected by the primary mirror and to keep optical surfaces and structures at ambient temperature, thus avoiding self-induced local seeing. A high-order adaptive-optics system with 1600 actuators corrects atmospheric seeing enabling diffraction limited imaging and spectroscopy. Five instruments, four of which are polarimeters, provide powerful diagnostic capability over a broad wavelength range covering the visible, near-infrared, and mid-infrared spectrum. New polarization-calibration strategies were developed to achieve the stringent polarization accuracy requirement of 5×10−4. Instruments can be combined and operated simultaneously in order to obtain a maximum of observational information. Observing time on DKIST is allocated through an open, merit-based proposal process. DKIST will be operated primarily in "service mode" and is expected to on average produce 3 PB of raw data per year. A newly developed data center located at the NSO Headquarters in Boulder will initially serve fully calibrated data to the international users community. Higher-level data products, such as physical parameters obtained from inversions of spectro-polarimetric data will be added as resources allow. Title: The off-limb polarized corona at high-resolution: new synthetic views for the DKIST era Authors: Schad, T. A.; Dima, G. I. Bibcode: 2020AGUFMSH0280015S Altcode: In anticipation of the great advances that the National Science Foundation's Daniel K. Inouye Solar Telescope will soon provide for spectropolarimetry of the off limb solar corona, we investigate the formation of the prime coronal lines targeted by DKIST as synthesized through advanced, high-resolution, finely-structured, 3D MURaM coronal simulations. In doing so, we demonstrate a new code developed for polarized line emission calculations referred to as pyCLE. We provide detailed benchmarks of pyCLE, in specific against tools provided by the Chianti team (in the scalar limit), both to validate the code and provide a primer for the line-dependent aspects of the polarization formation. Synthetic maps created using pyCLE and the MURaM active region simulation allow us to describe and predict polarized features within the array of multi-wavelength observables available. In addition, we comment on the opportunities provided for, as well as the challenges faced by, the analysis of the apparent polarized fine structure. Title: Forward Synthesis of Polarized Emission in Target DKIST Coronal Lines Applied to 3D MURaM Coronal Simulations Authors: Schad, Thomas; Dima, Gabriel Bibcode: 2020SoPh..295...98S Altcode: Self-consistent magnetohydrodynamic simulations of the solar corona with fine (≲10 km) grid scales are now being realized in parallel to advancements in high-resolution coronal spectropolarimetry provided by the National Science Foundation's Daniel K. Inouye Solar Telescope (DKIST). We investigate the synthesis of polarized emission in the presence of apparent coronal fine structure exhibited by 3D MURaM coronal simulations for the key polarized spectral lines targeted by DKIST, namely Fe XIVλ 5303 , Fe XIλ 7892 , Fe XIIIλ 10746 , Fe XIIIλ 10798 , Si Xλ 14301 , and Si IXλ 39343 . To benchmark our calculations, we provide detailed comparisons between the employed polarized line formation theory and established scalar line synthesis tools provided by the CHIANTI database team. To accelerate polarized synthesis for large simulations, we create efficient lookup tables based on atomic models significantly larger than previous studies. The spectral data cubes we describe provide a useful guide for the new era of multi-spectral DKIST coronal diagnostics as we discuss specific analysis techniques and challenges. Title: Using Multi-line Spectropolarimetric Observations of Forbidden Emission Lines to Measure Single-point Coronal Magnetic Fields Authors: Dima, Gabriel I.; Schad, Thomas A. Bibcode: 2020ApJ...889..109D Altcode: 2020arXiv200106123D Polarized magnetic dipole (M1) emission lines provide important diagnostics for the magnetic field dominating the evolution of the solar corona. This paper advances a multi-line technique using specific combinations of M1 lines to infer the full vector magnetic field for regions of optically thin emission that can be localized along a given line of sight. Our analytical formalism is a generalization of the "single-point inversion" approach introduced by Plowman. We show that combinations of M1 transitions for which each is either a $J=1\to 0$ transition or has equal Landé g-factors for the upper and lower levels contain degenerate spectropolarimetric information that prohibits the application of the single-point inversion technique. This may include the pair of Fe XIII lines discussed by Plowman. We identify the Fe XIII 10747 Å and Si X 14301 Å lines as one alternative combination for implementing this technique. Our sensitivity analysis, based on coronal loop properties, suggests that for photon noise levels around 10-4 of the line intensity, which will be achievable with the National Science Foundation's Daniel K. Inouye Solar Telescope, magnetic fields with sufficient strength (∼10 G) and not severely inclined to the line of sight (≲35°) can be recovered with this method. Degenerate solutions exist, though we discuss how added constraints may help resolve them or reduce their number. Title: Acceleration of Coronal Mass Ejection Plasma in the Low Corona as Measured by the Citizen CATE Experiment Authors: Penn, Matthew J.; Baer, Robert; Walter, Donald; Pierce, Michael; Gelderman, Richard; Ursache, Andrei; Elmore, David; Mitchell, Adrianna; Kovac, Sarah; Hare, Honor; McKay, Myles; Jensen, Logan; Watson, Zachary; Conley, Mike; Powers, Lynn; Lazarova, Marianna; Wright, Joseph; Young, David; Isberner, Fred; Hart, C. Alexandra; Sheeley, N. R., Jr.; Penn, Debbie; Allen-Penn, Kate; Alder, Bruce; Alder, Ryan; Hall-Conley, Geri; Gerdes, David; Weber, Katherine; Johnson, Jeffrey; Matzek, Gerald; Somes, Steven; Sobnosky, Rob; McGowen, Robert; Meo, Michael; Proctor, Damani; Wessinger, Charlie; Schilling, Jeannine; Kerr, Jay; Beltzer-Sweeney, Alexander; Falatoun, Alex; Higgins, David; Boyce, Grady; Hettick, Jared; Blanco, Philip; Dixon, Scott; Ardebilianfard, Sepehr; Boyce, Pat; Lighthill, Richard; Lighthill, Denese; Anderson, David; Anderson, Mine; Schad, Thomas; Smith, Sonna; Jensen, Declan; Allen, Anthony; Smith, Donavan; Brandon, Gage; Earp, Joe; Earp, Jane; Blair, Bob; Claver, Chuck F.; Claver, Jennifer A.; Claver, Ryan H.; Hoops, Danielle; Rivera, Esteban; Gibson, Llanee; Hiner, Martin; Lann, Rein; Miller, Shaedyn; Briggs, Burton; Davis, Karan; Jackson, Brian; Kautzsch, Kaleb; Sandidge, Wesley; Lucas, Russell; Gregg, Duane; Kamenetzky, Julia; Rivera, Tiffany; Shaw, Joe; Scherrer, Bryan; Sandbak, Dylan; McFate, Richard; Harris, Wilson; Brasier, Zachery; McNeil, Stephen; Jensen, Jack; Jensen, Makai; Moore, Mason; Temple, Alexandria; Vanderhorst, Thomas; Kautz, Richard; Bellorado, Orion; Jenkins, LaVor R.; Pantuso, Corey; Carey, Marley; Byrnes, Josh; Scholtens, Kyle; Web, Julian; Baker, Brain; Barngrover, Katie; Hathaway, Drew; Smith, Kallen; Chandler, Kellyn; Hinkle, Lydia; Chandler, Ione; Gisler, Galen; Benner, Jack; Mas, Madison; Rogers, Maya; Moore, Prescott; Pelofske, Elijah; Gulley, Stephen; Short, Beth; Crooker, Isabel; Hammock, Jennifer; Cardenas, Katsina; Cardenas, Kateri; Wellman, Jennifer; Roy, Mark; Meyer, Joe; Brough, Jalynne; Brough, Kameron; Nelson, Tim; Nelson, Zack; Russell, Caleb; Bautz, Theresa; Weitzel, Eric; Team; Wistisen, Michele; Aagard, Shae; Whipps, Zachary; Neuroth, Logan; Poste, Dawson; Worthen, Connor; Gosain, Sanjay; Steward, Mark; Gosain, Vanshita; Gosain, Ruchi; Jorgensen, Janet; Doucette, Eleanor; Doucette, Reba; Iwen, Elliott; Cochran, Alexus; Stith, James; Scribner, Doug; Kenney, Austen; Pisciotti, Kolby; Pease, Irene; Cynamon, Samuel; Cynamon, Charles; Cynamon, Dawn; Tolbert, Bart; Dupree, Jean A.; Weremeichik, Jeremy; Pindell, Nathan; Stives, Kristen; Simacek, Thomas K.; Simacek, Yolanta G.; Simacek, Anne L.; Boeck, Wayne; Boeck, Andreea; Ryan, Austin; Wierzorec, Gabriel; Klebe, Dimitri; Costanza, Bryan; Cerny, Arnie; Schmale, Trevor; Hoffman, Tessa; Streeter, Sam; Erickson, Jack; McClellan, Michele; Erickson, Ella; Brettell, Brynn; Shoffner, Savannah; McClellan, Emilie; VanVoorhis, Julie; Bramhall, Cole; Stelly, Daniel; Bee, Bentley; Acevedo, Bruno; Kroeger, Madison; Trumpenski, Ben; Sump, Nolan; Brook, Liam; Ernzen, Jagert; Lewis, Jessica; Maderak, Ryan; Kennedy, Charles; Dembinski, David; Wright, Rita; Foster, Michael; Ahmadbasir, Mohammad; Laycox, Monty; Foster, James; Orr, Ethan; Staab, Ashley; Speck, Angela; Baldridge, Sean; Kegley, Lucy; Bavlnka, Jordan; Ballew, Thomas; Callen, Bruce; Ojakangas, Gregory; Bremer, Mark; Angliongto, Maryanne; Redecker, Mark; Bremer, Chris; Hill, Peggy; Rodgers, Michael; Duncan, Jordan; Fincher, Sam; Nielsen, Ben; Hasler, Samantha; Shivelbine, Taylor; Howard, Tyler; Midden, Chris; Patrick, Sean; Glenn, Kerry; Mandrell, Chris; Dawson, Kyle; Cortez, Margaret; Levsky, Alyssa; Gallaba, Dinuka; Perrone, Mason; Taylor, Jasmyn; Yanamandra-Fisher, Padma A.; Harper, Howard; Adams, Lindsay; Springer, Michaela; Menard, BillyJoe; Boggs, Dylan; Lynch, Caitlin; Watson, Jacob; York, Andi; Matthews, David; Brown, Kiley; Garrison, Dylan; Mangin, Jonathan; Mangin, Isaac; Birriel, Jennifer; Birriel, Ignacio; Yess, Capp; Anderson, Jesse; Caudill, Ethan; Smith, Allyn; Buckner, Spencer; Longhurst, Russ; Fagan, Ben; Nations, Christian; DiMatties, Jeffrey; Thompson, Patricia; Garrison, David; Garrison, Thomas; Garrison, William; Kidd, Mary; Baker, Maria; Ledford, Mary-Beth; Winebarger, Amy; Freed, Michael; Church, Morgyn; Dickens, Jim; Anderson, Bob; Smith, Ned; Dorsey, Lynne; Justice, Doug; Zavala, Daniel; Stockbridge, Zach; Brittain, Sean; Jensen, Stanley; Leiendecker, Harrison; Thompson, Erin; Deady, Michelle; Quinn-Hughes, Kelly; Slimmer, David; Granger, Valerie; LaRoche, Michael; Hill LaRoche, Serena; Manspeaker, Rachel; Nguyen, Peter; Smith, Daniel; Payne, Jim; Zissett, Jerry; Roberts, Arianna M.; Roberts, Gabrielle W.; Roberts, Harrison; Riddle, Amy; Ursache, Corina; Ursache, Elena Bibcode: 2020PASP..132a4201P Altcode: The citizen Continental-America Telescopic Eclipse (CATE) Experiment was a new type of citizen science experiment designed to capture a time sequence of white-light coronal observations during totality from 17:16 to 18:48 UT on 2017 August 21. Using identical instruments the CATE group imaged the inner corona from 1 to 2.1 RSun with 1.″43 pixels at a cadence of 2.1 s. A slow coronal mass ejection (CME) started on the SW limb of the Sun before the total eclipse began. An analysis of CATE data from 17:22 to 17:39 UT maps the spatial distribution of coronal flow velocities from about 1.2 to 2.1 RSun, and shows the CME material accelerates from about 0 to 200 km s-1 across this part of the corona. This CME is observed by LASCO C2 at 3.1-13 RSun with a constant speed of 254 km s-1. The CATE and LASCO observations are not fit by either constant acceleration nor spatially uniform velocity change, and so the CME acceleration mechanism must produce variable acceleration in this region of the corona. Title: Shock Heating Energy of Umbral Flashes Measured with Integral Field Unit Spectroscopy Authors: Anan, Tetsu; Schad, Thomas A.; Jaeggli, Sarah A.; Tarr, Lucas A. Bibcode: 2019ApJ...882..161A Altcode: 2019arXiv190710797A Umbral flashes are periodic brightness increases routinely observed in the core of chromospheric lines within sunspot umbrae and are attributed to propagating shock fronts. In this work we quantify the shock heating energy of these umbral flashes using observations in the near-infrared He I triplet obtained on 2014 December 7 with the SpectroPolarimetric Imager for the Energetic Sun, which is a novel integral field unit spectrograph at the Dunn Solar Telescope. We determine the shock properties (the Mach number and the propagation speed) by fitting the measured He I spectral profiles with a theoretical radiative transfer model consisting of two constant-property atmospheric slabs whose temperatures and macroscopic velocities are constrained by the Rankine-Hugoniot relations. From the Mach number, the shock heating energy per unit mass of plasma is derived to be 2 × 1010 erg g-1, which is insufficient to maintain the umbral chromosphere. In addition, we find that the shocks propagate upward with the sound speed and the Mach number does not depend on the temperature upstream of the shocks. The latter may imply suppression of the amplification of the Mach number due to energy loss of the shocks. Title: Shock heating energy in an umbra of a sunspot with integral field unit spectroscopy Authors: Anan, Tetsu; Schad, Thomas A.; Jaeggli, Sarah A.; Tarr, Lucas A. Bibcode: 2019AAS...23421705A Altcode: On 2014 December 7 we used new integral field spectroscopy techniques to observe umbral flashes, which are periodic brightness increases routinely observed in the core of chromospheric lines within sunspot umbrae and are attributed to propagating shock fronts. In this work we quantify the shock heating energy of these umbral flashes using observations in the near infrared HeI triplet obtained with the SpectroPolarimetric Imager for the Energetic Sun (SPIES), which is novel integral field unit spectrograph at the Dunn Solar Telescope. We determine the shock properties (the Mach number and the propagation speed) by fitting the measured HeI spectral profiles with a theoretical radiative transfer model using two constant property atmospheric slabs whose temperatures and macroscopic velocities are constrained by the Rankine-Hugoniot relations. From the Mach number, the shock heating energy per unit mass of plasma is derived as 2 x 1010 erg/g. We conclude that the estimated shock heating energy rate is less than the amount required to maintain the umbral chromosphere. Title: Coronagraphic Observations of Si X λ14301 and Fe XIII λ10747 Linearly Polarized Spectra Using the SOLARC Telescope Authors: Dima, Gabriel I.; Kuhn, Jeffrey R.; Schad, Thomas A. Bibcode: 2019ApJ...877..144D Altcode: The forbidden Si X emission line at 14301 Å has been identified as a potentially valuable polarized diagnostic for solar coronal magnetic fields; however, the only polarized Si X measurements achieved to date have been during eclipses and at comparatively low spatial and spectral resolution. Here we report spectropolarimetric observations of both the Si X 14301 Å and more well-established Fe XIII 10747 Å coronal lines acquired with the 0.45 m aperture SOLARC coronagraph atop Haleakalā. Using its fiber-based integral field spectropolarimeter, we derive observations sampled at radial intervals of 0.05 {R} (i.e., ∼50″) with a spectral resolving power of ≈36,000. Results for both lines, which represent averages over different active and nonactive regions of the corona, indicate a relatively flat radial variation for the line widths and line centers and a factor of ≈2-3 decrease in polarized brightness between 1.05 and 1.45 {R}. Averaging over all the measurements the mean and standard deviations of line properties for Si X 14301 Å and Fe XIII 10747 Å are, respectively, FWHM of 3.0 ± 0.4 Å and 1.6 ± 0.1 Å, line-integrated polarized brightness of 0.07 ± 0.03 and 0.3 ± 0.3 erg s-2 cm-2 sr-1, where the uncertainty quoted reflects a large sample variance, and line center wavelengths 14300.7 ± 0.2 Å and 10746.3 ± 0.1 Å. The polarized brightness for both lines may be underestimated by up to a factor of 5 due to limitations in the photometric calibration. When accounting for this uncertainty we find consistency between our observations and previous measurements of the two lines as well as theoretical calculations and affirm the potential of the Si X line as a polarized diagnostic of the solar corona. Title: Polarimetric observations of the SiX and Fe XIII infrared coronal emission lines using the SOLARC telescope Authors: Dima, Gabriel; Kuhn, Jeffrey Richard; Schad, Thomas A. Bibcode: 2019AAS...23411704D Altcode: The forbidden Si X emission line at 14301 Å has been identified as a potentially valuable polarized diagnostic for solar coronal magnetic fields; however, the only polarized Si X measurements achieved to date have been during eclipses and at comparatively low spatial and spectral resolution. Here we report spectropolarimetric observations of both the Si X 14301 Å and more well-established FeXIII 10747 Å coronal lines acquired with the 0.45 m aperture SOLARC coronagraph atop Haleakala. Results for both lines, which represent averages over different active and non-active regions of the corona, indicate a relatively flat radial variation for the line widths and line centers and a factor of 2-3 decrease in polarized brightness between 1.05 and 1.45 R. Averaging over all the measurements the mean and standard deviations of line properties for Si X 14301 Å and Fe XIII 10747 Å are respectively: FWHM of 3.0±0.4 Å and 1.6±0.1, line-integrated polarized brightness of 0.07±0.03 and 0.3±0.3 erg s-2 cm-2 sr-1 where the uncertainty quoted reflects a large sample variance, and line center wavelengths 14300.7±0.2 Å and 10746.3±0.1 Å. The polarized brightness for both lines may be underestimated by up to a factor of 5 due to limitations in the photometric calibration. When accounting for this uncertainty we find consistency between our observations and previous measurements of the two lines as well as theoretical calculations and affirm the potential of the Si X line as a polarized diagnostic of the solar corona. Title: Multi-line diagnostics of the coronal magnetic field with DKIST Authors: Dima, Gabriel; Schad, Thomas A. Bibcode: 2019AAS...23410601D Altcode: Full-stokes polarimetric observations of multiple coronal emission lines can in principle be used to infer the vector magnetic field in the solar corona assuming the emission is all coming from a single location in space. The Fe XIII line pair at 10747 / 10798 Å has already been identified as a prime candidate for multi-line inversions; although such measurements are sensitive to uncertainties and biases that must be carefully assessed. That said, this technique may have additional utility when expanded to other multi-line observations planned for the National Science Foundation's Daniel K Inouye Solar Telescope (DKIST). This work investigates, in particular, the use of the Fe XIII 10747 / Si X 14301 Å line pair, and its benefits for probing the magnetic conditions in cooler coronal loops formed near 1.4 MK. We discuss the advantages and limitations of the Fe XIII / Si X line pair as well as possible observing scenarios with the DL-NIRSP and Cryo-NIRSP instruments on the DKIST. Title: Neutral Helium Triplet Spectroscopy of Quiescent Coronal Rain with Sensitivity Estimates for Spectropolarimetric Magnetic Field Diagnostics Authors: Schad, Thomas A. Bibcode: 2018ApJ...865...31S Altcode: 2018arXiv180902252S On account of its polarizability and magnetic field sensitivity, as well as the role of neutral helium in partially ionized solar environments, the neutral helium triplet (orthohelium) system provides important, yet underutilized, diagnostics of solar coronal rain. This work describes off-limb observations of coronal rain in NOAA Active Region 12468 obtained in the He I 10830 Å triplet using the Massively MultipleXed Imaging Spectrograph experiment at the Dunn Solar Telescope along with cotemporal observations from NASA’s Solar Dynamics Observatory and the Interface Region Imaging Spectrograph (IRIS). We detect rain simultaneously in the IRIS 1400 and 2796 Å channels and in He I 10830 Å. The large degree of spatial coherence present between all channels agrees with previous observations of the multitemperature nature of coronal rain. A statistical analysis of He I spectral profiles for rain identified via automated detection indicates that He I line radiances are, on average, 104 erg cm-2 s-1 sr-1 the average translational velocity is 70 km s-1, and Doppler widths are distributed around 10 km s-1. Based on these results, forward models of expected He I polarized signals allow us to estimate, using synthetic observables and an inversion algorithm including fits for the scattering angle constraining the material’s location along the line of sight, the magnetic sensitivity of the upcoming National Science Foundation’s Daniel K. Inouye Solar Telescope. We predict that joint observations of the He I 10830 and 5876 Å multiplets using first-light instrumentation will provide inverted magnetic field errors of ±3.5 G (2σ) for spatial scales of 0.″5 (∼360 km), assuming dynamically limited integration times of 5.5 s. Title: Magnetic Diagnostics of Coronal Rain using the DKIST Authors: Schad, Thomas Bibcode: 2018cosp...42E3005S Altcode: The routine production of coronal rain in the outer solar atmosphere provides one of the finest probes we have of the coronal plasma environment and its apparent structuring. Despite the range of phenomena discovered with imaging observations, the magnetic environment hosting and marshaling rain production remains poorly constrained by observations. With the dawn of the DKIST and its advanced suite of five facility instruments, this is primed to change. The large DKIST aperture (4 meter) provides a collecting area capable of combining rapid exposure imaging diagnostics and spectroscopic observations of coronal rain with meaningful spectropolarimetric observations, which to date have been rarely achieved for coronal rain. The brightness of coronal rain in key chromospheric diagnostics (as compared to hot infrared coronal lines) offers a very significant photon advantage for conducting "cool" coronal magnetometry. This talk will discuss the building blocks for an observational framework to study coronal rain at DKIST, including how to coordinate VBI imaging, VISP spectropolarimetry, VTF 2D spectro-imaging, and DL-NIRSP IFU-based spectropolarimetry. This discussion will be guided by recent observations of neutral helium production within coronal rain that allow us to much better predict DKIST capabilities for coronal rain polarimetry. In addition, automated analysis techniques based on the Rolling Hough Transform have been developed that assist with these techniques. Coronal rain is a critical use case for early science at DKIST when it becomes operational in 2020. Title: Status of the Daniel K. Inouye Solar Telescope: unraveling the mysteries the Sun. Authors: Rimmele, Thomas R.; Martinez Pillet, Valentin; Goode, Philip R.; Knoelker, Michael; Kuhn, Jeffrey Richard; Rosner, Robert; Casini, Roberto; Lin, Haosheng; von der Luehe, Oskar; Woeger, Friedrich; Tritschler, Alexandra; Fehlmann, Andre; Jaeggli, Sarah A.; Schmidt, Wolfgang; De Wijn, Alfred; Rast, Mark; Harrington, David M.; Sueoka, Stacey R.; Beck, Christian; Schad, Thomas A.; Warner, Mark; McMullin, Joseph P.; Berukoff, Steven J.; Mathioudakis, Mihalis; DKIST Team Bibcode: 2018AAS...23231601R Altcode: The 4m Daniel K. Inouye Solar Telescope (DKIST) currently under construction on Haleakala, Maui will be the world’s largest solar telescope. Designed to meet the needs of critical high resolution and high sensitivity spectral and polarimetric observations of the sun, this facility will perform key observations of our nearest star that matters most to humankind. DKIST’s superb resolution and sensitivity will enable astronomers to address many of the fundamental problems in solar and stellar astrophysics, including the origin of stellar magnetism, the mechanisms of coronal heating and drivers of the solar wind, flares, coronal mass ejections and variability in solar and stellar output. DKIST will also address basic research aspects of Space Weather and help improve predictive capabilities. In combination with synoptic observations and theoretical modeling DKIST will unravel the many remaining mysteries of the Sun.The construction of DKIST is progressing on schedule with 80% of the facility complete. Operations are scheduled to begin early 2020. DKIST will replace the NSO facilities on Kitt Peak and Sac Peak with a national facility with worldwide unique capabilities. The design allows DKIST to operate as a coronagraph. Taking advantage of its large aperture and infrared polarimeters DKIST will be capable to routinely measure the currently illusive coronal magnetic fields. The state-of-the-art adaptive optics system provides diffraction limited imaging and the ability to resolve features approximately 20 km on the Sun. Achieving this resolution is critical for the ability to observe magnetic structures at their intrinsic, fundamental scales. Five instruments will be available at the start of operations, four of which will provide highly sensitive measurements of solar magnetic fields throughout the solar atmosphere - from the photosphere to the corona. The data from these instruments will be distributed to the world wide community via the NSO/DKIST data center located in Boulder. We present examples of science objectives and provide an overview of the facility and project status, including the ongoing efforts of the community to develop the critical science plan for the first 2-3 years of operations. Title: Pipeline development for routine chromospheric magnetic field inversions of DST/FIRS observations Authors: Wang, Shuo; Schad, Thomas A.; Mcateer, R. T. James Bibcode: 2018tess.conf30819W Altcode: The Facility Infrared Spectropolarimeter (FIRS) at the Dunn Solar Telescope (DST) provides efficient mapping of the full Stokes vector in the chromospheric He I triplet at 1083 nm across solar targets. The inversion of this type of data to achieve measurements of the magnetic field vector plays a key role in understanding chromospheric active region topologies and is especially useful in studying solar filaments and prominences. As a baseline supporting future synoptic magnetic observations of solar filaments at the DST, we demonstrate first steps in implementing a new pipeline that inverts FIRS data using the "Hanle and Zeeman Light" (HAZEL) code, which incorporates all the relevant atomic-level and Zeeman effect mechanisms. Inverted wide-field observations (170'' x 70'') of NOAA AR 12470 on December 14, 2015, exhibit our ability to recover reliable field measurements using multiple parallel FIRS slits. Using this pipeline, further analysis of active region magnetic fields may shed light on the formation and eruption processes of active region filaments. Title: Inference of chromospheric magnetic fields in a sunspot derived from spectropolarimetry of Ca II 8542 A Authors: Abdelkawy, Ali G. A.; Shaltout, Abdelrazek M. K.; Beheary, M. M.; Schad, T. A. Bibcode: 2017arXiv171206829A Altcode: We analyze spectropolarimetric observations of the chromospheric Ca II 8542 A line taken by the Interferometric Bidimensional Spectrometer (IBIS) at the Dunn Solar Telescope. The data were observed on 2012 January 29 for the NOAA active region 11408. Adopting the center-of-gravity (COG) approach we obtain the line-of-sight (LOS) field strength for the chromospheric IBIS data of Ca II 8542 A line. The LOS strength of the magnetic field is determined in the target active region inside a field of view 45 x 95 arcsec. The LOS field values were found to be increase up to 800 G inside the umbral region and decrease systematically toward the edges of a sunspot. Under the weak field approximation (WFA), the horizontal, vertical magnetic field components and azimuthal field vector are obtained. Title: Infrared Imaging Spectroscopy Using Massively Multiplexed Slit-Based Techniques and Sub-Field Motion Correction Authors: Schad, Thomas; Lin, Haosheng Bibcode: 2017SoPh..292..158S Altcode: 2018arXiv180905132S Targeting dynamic spatially extended phenomena in the upper solar atmosphere, a new instrument concept has been developed and demonstrated at the Dunn Solar Telescope in New Mexico, USA, which provides wide-field, rapid-scanning, high-resolution imaging spectroscopy of the neutral helium λ 10830 spectral triplet. The instrument combines a narrowband imaging channel with a novel cospatial grating-based spectrograph with 17 parallel long slits that are simultaneously imaged on a single HgCdTe detector. Over a 175×125 field of view, a temporal cadence of 8.5 s is achieved between successive maps that critically sample the diffraction limit of the Dunn Solar Telescope at 1083 nm (1.22 λ /D =0.36) and provide a resolving power (R =λ /δ λ ) up to ≈25 ,000 with a 1 nm bandwidth (i.e.275 kms−1 Doppler coverage). Capitalizing on the strict simultaneity of the narrowband channel relative to each spectral image (acquired at a rate of 9.53 Hz), this work demonstrates that sub-field image motion introduced by atmospheric seeing may be corrected post-facto in each mapped spectral data cube. This instrument furnishes essential infrared spectral imaging capabilities for current investigations while pioneering techniques for high-resolution wide-field time-domain solar astronomy. Title: Automated Spatiotemporal Analysis of Fibrils and Coronal Rain Using the Rolling Hough Transform Authors: Schad, Thomas Bibcode: 2017SoPh..292..132S Altcode: 2018arXiv180903635S A technique is presented that automates the direction characterization of curvilinear features in multidimensional solar imaging datasets. It is an extension of the Rolling Hough Transform (RHT) technique presented by Clark, Peek, and Putman (Astrophys. J.789, 82, 2014), and it excels at rapid quantification of spatial and spatiotemporal feature orientation even for applications with a low signal-to-noise ratio. It operates on a pixel-by-pixel basis within a dataset and reliably quantifies orientation even for locations not centered on a feature ridge, which is used here to derive a quasi-continuous map of the chromospheric fine-structure projection angle. For time-series analysis, a procedure is developed that uses a hierarchical application of the RHT to automatically derive the apparent motion of coronal rain observed off-limb. Essential to the success of this technique is the formulation presented in this article for the RHT error analysis as it provides a means to properly filter results. Title: Critical Infrared Science with the Daniel K. Inouye Solar Telescope Authors: Schad, Thomas A.; Fehlmann, Andre; Jaeggli, Sarah A.; Kuhn, Jeffrey Richard; Lin, Haosheng; Penn, Matthew J.; Rimmele, Thomas R.; Woeger, Friedrich Bibcode: 2017SPD....4811703S Altcode: Critical science planning for early operations of the Daniel K. Inouye Solar Telescope is underway. With its large aperture, all-reflective telescope design, and advanced instrumentation, DKIST provides unprecedented access to the important infrared (IR) solar spectrum between 1 and 5 microns. Breakthrough IR capabilities in coronal polarimetry will sense the coronal magnetic field routinely for the first time. The increased Zeeman resolution near the photospheric opacity minimum will provide our deepest and most sensitive measurement of quiet sun and active region magnetic fields to date. High-sensitivity He I triplet polarimetry will dynamically probe the chromospheric magnetic field in fibrils, spicules, and filaments, while observations of molecular CO transitions will characterize the coolest regions of the solar atmosphere. When combined with the longer timescales of good atmospheric seeing compared with the visible, DKIST infrared diagnostics are expected to be mainstays of solar physics in the DKIST era. This paper will summarize the critical science areas addressed by DKIST infrared instrumentation and invite the community to further contribute to critical infrared science planning. Title: Wide-field, dynamic, slit-based spectroscopy of neutral helium in coronal rain Authors: Schad, T. A. Bibcode: 2016AGUFMSH43C2581S Altcode: Building upon the Massively Multiplexed Spectrograph (mxSPEC) instrument concept [Lin, H. SPIE Vol. 9147 (2014)], we report dynamical observations of off-limb coronal rain in the neutral orthohelium lines at 1083 nm using an experiment that combines a narrowband imaging channel with a co-spatial, 17 parallel-long-slit, grating-based, spectrograph on a single HgCdTe detector. Over a 170'' x 120'' field of view, a temporal cadence of 8.5 seconds is achieved between successive maps that critically sample the diffraction limit of the Dunn Solar Telescope (1.22λ/D = 0.36'') while providing a spectral resolution (R = λ/δλ) of 40000 and a bandwidth of 1 nm (i.e. 275 km/sec Doppler coverage). The strict simultaneity of the narrowband channel relative to the each spectra (acquired at a rate of 10 Hz) allows a robust assessment (and/or compensation) of the atmospheric seeing. Due to the relatively high helium abundance, the magnetic sensitivity of the helium triplet, and the expected important role of neutral helium atoms in partially ionized environments, the He I triplet is an important diagnostic of coronal rain that will be made available by the Daniel K Inouye Solar Telescope (DKIST), currently under construction on Haleakala, Maui, Hawaii. This report will introduce the modified mxSPEC observing technique, discuss the dynamics observed in the He I spectra, and compare these dynamics with coordinated slit-jaw measurements at 1400 and 2796 Angstrom from the Interface Region Imaging Spectrograph (IRIS). Title: Vector Magnetic Field Measurements along a Cooled Stereo-imaged Coronal Loop Authors: Schad, T. A.; Penn, M. J.; Lin, H.; Judge, P. G. Bibcode: 2016ApJ...833....5S Altcode: 2016arXiv161005332S The variation of the vector magnetic field along structures in the solar corona remains unmeasured. Using a unique combination of spectropolarimetry and stereoscopy, we infer and compare the vector magnetic field structure and three-dimensional morphology of an individuated coronal loop structure undergoing a thermal instability. We analyze spectropolarimetric data of the He I λ10830 triplet (1s2s{}3{S}1-1s2p{}3{P}{2,1,0}) obtained at the Dunn Solar Telescope with the Facility Infrared Spectropolarimeter on 2011 September 19. Cool coronal loops are identified by their prominent drainage signatures in the He I data (redshifts up to 185 km s-1). Extinction of EUV background radiation along these loops is observed by both the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory and the Extreme Ultraviolet Imager on board spacecraft A of the Solar Terrestrial Relations Observatory, and is used to stereoscopically triangulate the loop geometry up to heights of 70 Mm (0.1R Sun) above the solar surface. The He I polarized spectra along this loop exhibit signatures indicative of atomic-level polarization, as well as magnetic signatures through the Hanle and Zeeman effects. Spectropolarimetric inversions indicate that the magnetic field is generally oriented along the coronal loop axis, and provide the height dependence of the magnetic field intensity. The technique we demonstrate is a powerful one that may help better understand the thermodynamics of coronal fine-structure magnetism. Title: Student artistry sparks eclipse excitement on Maui: NSO/DKIST EPO for the 2016 Partial Solar Eclipse Authors: Schad, Thomas A.; Penn, Matthew J.; Armstrong, James Bibcode: 2016SPD....47.0501S Altcode: Local creativity and artistry is a powerful resource that enhances education programs and helps us generate excitement for science within our communities. In celebration of the 2016 Solar Eclipse, the National Solar Observatory (NSO) and its Daniel K Inouye Solar Telescope (DKIST) project were pleased to engage with students across Maui County, Hawai`i, via the 2016 Maui Eclipse Art Contest. With the help of the Maui Economic Development Board and the University of Hawai'is Institute for Astronomy, we solicited art entries from all K-12 schools in Maui County approximately 6 months prior to the eclipse. Along with divisional prizes, a grand prize was selected by a panel of local judges, which was subsequently printed on 25,000 solar eclipse viewing glasses and distributed to all Maui students. We found that the impact of a locally-sourced glasses design cannot be understated. Overall, the success of this program relied upon reaching out to individual teachers, supplying educational flyers to all schools, and visiting classrooms. On the day of the eclipse, all of the art entries were prominently displayed during a community eclipse viewing event at Kalama Beach Park in Kihei, HI, that was co-hosted by NSO and the Maui Science Center. This eclipse art contest was integral to making local connections to help promote science education on Maui, and we suggest that it could be adapted to the solar community's EPO activities for the upcoming 2017 Great American Solar Eclipse. Title: He I Vector Magnetic Field Maps of a Sunspot and Its Superpenumbral Fine-Structure Authors: Schad, T. A.; Penn, M. J.; Lin, H.; Tritschler, A. Bibcode: 2015SoPh..290.1607S Altcode: 2015arXiv150505567S; 2015SoPh..tmp...60S Advanced inversions of high-resolution spectropolarimetric observations of the He I triplet at 1083 nm are used to generate unique maps of the chromospheric magnetic field vector across a sunspot and its superpenumbral canopy. The observations were acquired by the Facility Infrared Spectropolarimeter (FIRS) at the Dunn Solar Telescope (DST) on 29 January 2012. Multiple atmospheric models are employed in the inversions because superpenumbral Stokes profiles are dominated by atomic-level polarization, while sunspot profiles are Zeeman-dominated, but also exhibit signatures that might be induced by symmetry-breaking effects of the radiation field incident on the chromospheric material. We derive the equilibrium magnetic structure of a sunspot in the chromosphere and furthermore show that the superpenumbral magnetic field does not appear to be finely structured, unlike the observed intensity structure. This suggests that fibrils are not concentrations of magnetic flux, but are instead distinguished by individualized thermalization. We also directly compare our inverted values with a current-free extrapolation of the chromospheric field. With improved measurements in the future, the average shear angle between the inferred magnetic field and the potential field may offer a means to quantify the non-potentiality of the chromospheric magnetic field to study the onset of explosive solar phenomena. Title: Polarization properties of a birefringent fiber optic image slicer for diffraction-limited dual-beam spectropolarimetry Authors: Schad, Thomas; Lin, Haosheng; Ichimoto, Kiyoshi; Katsukawa, Yukio Bibcode: 2014SPIE.9147E..6ES Altcode: The birefringent fiber optic image slicer design, or BiFOIS, adapts integral field spectroscopy methods to the special needs of high-sensitivity, spatially-resolved spectropolarimetry. In solar astronomy these methods are of particular importance, as dynamic magnetism lies at the heart of various multi-scaled phenomena in the solar atmosphere. While integral field units (IFU) based on fiber optics have been in continual development for some time, standard stock multimode fibers do not typically preserve polarization. The importance of a birefringent fiber optic IFU design stems from the need for dual-beam spatio-temporal polarimetric modulation to correct for spurious polarization signals induced either by platform jitter or atmospheric seeing. Here we characterize the polarization response of a second generation BiFOIS IFU designed for solar spectropolarimetry. The unit provides 60 × 64 spatial imaging pixels in a densely-packed, high filling factor configuration. Particular attention is placed on the spatial uniformity of the IFU polarization response. Calibrated first-light solar observations are also presented to demonstrate the performance of the device in a real application. Title: Tools for 3D Spectropolarimetry - A Birefringent Fiber Optic Image Slicer Authors: Schad, Thomas A.; Lin, Haosheng Bibcode: 2014AAS...22412358S Altcode: Image-slicing technology benefits astronomical spectropolarimetry by transposing a three-dimensional informational set--two spatial and one spectral dimension--into a format more amenable to simultaneous coverage by conventional spectrographs. To probe, for example, the magnetism of the fine-scaled, dynamic chromosphere, methods beyond slit-based spectropolarimetry are essential. Fiber optic integral field units (IFUs) present one promising solution. The importance of a birefringent fiber-optic IFU design stems from the need of spatio-temporal modulation to correct for spurious polarization signals induced either by platform jitter or atmospheric seeing. Standard stock fibers do not typically preserve polarization. Here we characterize the polarization response of a close-packed IFU based on rectangular optical fibers, currently under development for the Diffraction-Limited Near-IR Spectropolarimeter, a facility instrument of the Advanced Technology Solar Telescope. Solar observations utilizing this device will be presented. Title: From static to dynamic mapping of chromospheric magnetism - FIRS and SPIES Authors: Schad, Thomas A.; Lin, Haosheng Bibcode: 2014AAS...22430204S Altcode: Advancements in theoretical forward modeling and observational techniques now allow the mapping of the chromospheric magnetic field vector in some regions. We report on full maps of the chromospheric magnetic field vector across a sunspot and its superpenumbra within NOAA AR 11408. These maps are derived from full Stokes observations of the He I triplet at 1083 nm, which show both Zeeman and atomic-level polarization signatures. Yet, due to the long time to acquire these observations with the slit-based Facility Infrared Spectropolarimeter (FIRS), our measurements primarily probe long-lived chromospheric structures, albeit at very high polarization sensitivity. The fast temporal scales remain difficult to probe with conventional slit-based spectropolarimeters. Alternatively, SPIES is an instrument based on a birefringent fiber optic IFU, designed to multiplex a two-dimensional spatial field with high spectral resolution spectropolarimetry, and is an ideal tool for probing small-scale, dynamic magnetic features. We will present movies of the dynamic chromosphere acquired from SPIES across a sunspot and its fine-scaled superpenumbra. Title: On the Collective Magnetic Field Strength and Vector Structure of Dark Umbral Cores Measured by the Hinode Spectropolarimeter Authors: Schad, T. A. Bibcode: 2014SoPh..289.1477S Altcode: 2015arXiv150505581S We study 7530 sunspot umbrae and pores measured by the Hinode Spectropolarimeter (SP) between November 2006 and November 2012. We primarily seek confirmation of the long term secular decrease in the mean magnetic field strength of sunspot umbrae found by Penn and Livingston (IAU Symp.273, 126, 2011) between 1998 and 2011. The excellent SP photometric properties and full vector magnetic field determinations from full-Stokes Milne-Eddington inversions are used to address the interrelated properties of the magnetic field strength and brightness temperature for all umbral cores. We find non-linear relationships between magnetic field strength and umbral temperature (and continuum contrast), as well as between umbral radius and magnetic field strength. Using disambiguated vector data, we find that the azimuths measured in the umbral cores reflect an organization weakly influenced by Joy's law. The large selection of umbrae displays a log-normal size spectrum similar to earlier solar cycles. Influenced by the amplitude of the solar cycle and the non-linear relationship between umbral size and core magnetic field strength, the distribution of core magnetic field strengths, fit most effectively with a skew-normal distribution, shows a weak solar cycle dependence. Yet, the mean magnetic field strength does not show a significant long term trend. Title: He I Vector Magnetometry of Field-aligned Superpenumbral Fibrils Authors: Schad, T. A.; Penn, M. J.; Lin, H. Bibcode: 2013ApJ...768..111S Altcode: 2013arXiv1303.4463S Atomic-level polarization and Zeeman effect diagnostics in the neutral helium triplet at 10830 Å in principle allow full vector magnetometry of fine-scaled chromospheric fibrils. We present high-resolution spectropolarimetric observations of superpenumbral fibrils in the He I triplet with sufficient polarimetric sensitivity to infer their full magnetic field geometry. He I observations from the Facility Infrared Spectropolarimeter are paired with high-resolution observations of the Hα 6563 Å and Ca II 8542 Å spectral lines from the Interferometric Bidimensional Spectrometer from the Dunn Solar Telescope in New Mexico. Linear and circular polarization signatures in the He I triplet are measured and described, as well as analyzed with the advanced inversion capability of the "Hanle and Zeeman Light" modeling code. Our analysis provides direct evidence for the often assumed field alignment of fibril structures. The projected angle of the fibrils and the inferred magnetic field geometry align within an error of ±10°. We describe changes in the inclination angle of these features that reflect their connectivity with the photospheric magnetic field. Evidence for an accelerated flow (~40 m s-2) along an individual fibril anchored at its endpoints in the strong sunspot and weaker plage in part supports the magnetic siphon flow mechanism's role in the inverse Evershed effect. However, the connectivity of the outer endpoint of many of the fibrils cannot be established. Title: He I Spectropolarimetry with FIRS: Towards Vector Magnetometry of Chromospheric Fibrils Plus New Diagnostics of Coronal Rain Authors: Schad, T. A.; Penn, M. J.; Lin, H.; Tritschler, A. Bibcode: 2012ASPC..463...25S Altcode: At the Dunn Solar Telescope, the Interferometric Bidimensional Spectrometer (IBIS) can measure the full Stokes vector of the Ca II 854.2 nm spectral line while the Facility Infrared Spectropolarimeter (FIRS) measures the Stokes vector of the He I triplet at 1083 nm. We analyze the He I triplet observed in two widely different features above NOAA AR 11295 on 19 September 2011 - thin (< 1″) chromospheric fibrils and a large-scale loop hosting a high-velocity coronal rain event. These two features are shown to first demonstrate the diagnostic potential of the He I triplet for magnetic fields in the chromosphere/transition region and second to stress the need to pair large-aperture facilities with flexible instrumentation. Inversions of the He I triplet near the penumbral boundary return azimuthal directions of the magnetic field aligned with fine-scale fibrils observed in the line core of Ca II. The coronal rain event shows Doppler velocities up to 195 km s-1, among the largest reported. We observe measurable polarization within the raining material, which may be a good magnetic diagnostic of chromospheric-like material higher in the corona within condensating loops. Title: Removal of Spectro-polarimetric Fringes by Two-dimensional Pattern Recognition Authors: Casini, R.; Judge, P. G.; Schad, T. A. Bibcode: 2012ApJ...756..194C Altcode: 2012arXiv1208.5104C We present a pattern-recognition-based approach to the problem of the removal of polarized fringes from spectro-polarimetric data. We demonstrate that two-dimensional principal component analysis can be trained on a given spectro-polarimetric map in order to identify and isolate fringe structures from the spectra. This allows us, in principle, to reconstruct the data without the fringe component, providing an effective and clean solution to the problem. The results presented in this paper point in the direction of revising the way that science and calibration data should be planned for a typical spectro-polarimetric observing run. Title: Spectropolarimetry of a Limb Active Region and its Cool Coronal Structures Authors: Judge, Philip G.; Kleint, L.; Casini, R.; Schad, T. Bibcode: 2012AAS...22052119J Altcode: During the SDO mission we have regularly used the IBIS and FIRS spectropolarimeters at the Dunn Solar Telescope to measure magnetic fields and plasma parameters from photosphere up to the coronal base. Here we analyze data of a region at and above the east limb (later named NOAA 11302) obtained on September 22nd 2011. The measurements show an erupting prominence, remarkably uniform cool plumes and some material seemingly draining into the active region along post-flare loops. The imaging Fabry-Perot instrument IBIS obtained 30 scans of intensity spectra (30s cadence) and 40 scans of Stokes parameters (90s cadence) in lines of Fe I 630 nm, Na I 596 nm, Ca II 852 nm and H-alpha 656 nm, with an angular resolution near 0.2", over a 40"x80" field of view. The FIRS slit was scanned across the solar image to obtain Stokes profiles including lines of Si I 1028.7 nm and He I 1083 nm. We obtained 3 FIRS scans covering a 90"x75" area with cadences of between half an hour and an hour simultaneously with IBIS, at a lower angular resolution. Simultaneous broad band Ca II K and G-band data were obtained with a cadence of 5s. We discuss the vector magnetic fields and plasma properties of NOAA 11302, with emphasis on cool

plasma structures extending many Mm into the corona. Title: Multi-wavelength Spectropolarimetry Of A Sunspot Superpenumbra With Firs And Ibis Authors: Schad, Thomas A.; Tritschler, A.; Penn, M. J. Bibcode: 2012AAS...22020302S Altcode: Extending nearly radially from magnetic field concentrations like sunspot umbrae or pores, threadlike fibrils observed in the chromosphere and transition region host a variety of dynamic behavior and have long been considered local tracers for the magnetic field. Morphologically, fibrils are similar to spicules seen on the limb. The connectivity of fibrils outside of the magnetic field concentrations with the photosphere and/or corona is not well understood, and probing the magnetic field in these features remains challenging. In this contribution we describe multi-wavelength spectropolarimetric observations from the Dunn Solar Telescope in New Mexico using the Facility Infrared Spectropolarimeter (FIRS) and the Interferometric BiDimensional Spectropolarimeter (IBIS). FIRS performs high resolution slit spectropolarimetry in the He I triplet at 1083 nm, which is a promising diagnostic of chromospheric vector fields. Significant progress has been made to boost the accuracy and sensitivity of these measurements. Here we present measurements of an active region sunspot at a spatial resolution of 0.3 arcsec and an RMS noise in Stokes Q,U,V spectra down to 0.0003 in units of the local continuum (SNR > 3300). We perform full inversions of these spectra taking into account both Zeeman and Hanle effects. Initial results lend support for field-aligned fibrils near the penumbral boundary of a sunspot. Jointly with the FIRS observations, we use IBIS to observe the Stokes vectors of Ca II 854.2 nm and Fe I 617.3 nm and the intensity spectrum of H-alpha 656.3 nm. As a spectral imaging instrument, IBIS rapidly scans through the three spectral lines over a 45'' by 95'' FOV at an overall cadence of 50 seconds, allowing a much better description the dynamics of fibrils observed by both FIRS and IBIS. Title: Coronal Rain Observed On-disk with He I Spectropolarimetry from DST/FIRS Authors: Schad, Thomas A.; Penn, M. J.; Pietarila, A. Bibcode: 2012AAS...22031005S Altcode: Coronal rain refers to cool, dense blobs of plasma that presumably condense near the apex of hot coronal loops and then "rain" down upon the chromosphere traveling along curved loop-like paths. Considered to be the result of a thermal instability known as "catastrophic cooling", coronal rain places constraints on heating mechanisms for coronal loops. Nearly all observational studies of coronal rain, however, have been limited to the solar limb where cooler material within hot coronal loops is more readily identified. Here, we report observations of what we interpret to be the on-disk counterpart of coronal rain. Scanned spectropolarimetric observations in the He I triplet (1083 nm) from the Facility Infrared Spectropolarimeter (FIRS) reveal highly-redshifted material displaying an acceleration along curved trajectories terminating within a large sunspot (located at N17W21). Line-of-sight velocities in the He I triplet peak near 190 km/s, which can be consider high in relation to most coronal rain observations. This is also the largest redshift ever reported in the He I triplet. These curved loops correspond to an overarching loop structure seen in SDO/AIA anchored at its ends by a large sunspot and a group of pores. The loops observed with SDO/AIA display significant cooling as dark (EUV absorptive) blobs begin to form near the loop apex and then traverse along the same trajectories observed in the He I FIRS observations. Although the EUVI instrument of STEREO-A/SECCHI has a reduced temporal resolution compared to SDO/AIA, we are able to confidently match rain features in both spacecraft and thus stereoscopically reconstruct the three-dimensional trajectory to confirm the material is raining upon the solar surface. Title: Sunspot Dynamics as seen with CO 4666nm Spectroscopy Authors: Penn, Matthew J.; Schad, T. Bibcode: 2012AAS...22020610P Altcode: High resolution adaptive-optics corrected spectroscopy of sunspots using strong CO absorption lines at 4666nm was performed at the McMath-Pierce Solar Telescope using the NSO Array Camera. Active region NOAA 11158 was observed after the X-class flare on 17 Feb 2011. Several hours of rapid cadence scans reveal changes in umbral bright points, Evershed flows, flows along a sheer zone and penumbral fibrils as seen with the cool CO lines. Solar oscillations are studied, and the chromospheric structure associated with the regions of CO absorption are examined using 854.2nm Ca spectroscopy. Title: Probing the Solar Atmosphere Using Oscillations of Infrared CO Spectral Lines Authors: Penn, M. J.; Schad, T.; Cox, E. Bibcode: 2011ApJ...734...47P Altcode: 2010arXiv1012.2371P Oscillations were observed across the whole solar disk using the Doppler shift and line center intensity of spectral lines from the CO molecule near 4666 nm with the National Solar Observatory's McMath/Pierce solar telescope. Power, coherence, and phase spectra were examined, and diagnostic diagrams reveal power ridges at the solar global mode frequencies to show that these oscillations are solar p-modes. The phase was used to determine the height of formation of the CO lines by comparison with the IR continuum intensity phase shifts as measured in Kopp et al. we find that the CO line formation height varies from 425 km < z < 560 km as we move from disk center toward the solar limb 1.0 > μ > 0.5. The velocity power spectra show that while the sum of the background and p-mode power increases with height in the solar atmosphere as seen in previous work, the power in the p-modes only (background subtracted) decreases with height. The CO line center intensity weakens in regions of stronger magnetic fields, as does the p-mode oscillation power. Across most of the solar surface the phase shift is larger than the expected value of 90° for an adiabatic atmosphere. We fit the phase spectra at different disk positions with a simple atmospheric model to determine that the acoustic cutoff frequency is about 4.5 mHz with only small variations, but that the thermal relaxation frequency drops significantly from 2.7 to 0 mHz at these heights in the solar atmosphere. Title: High-Resolution He I Spectropolarimetry of Chromospheric Fibrils Authors: Schad, Thomas A.; Penn, M. J. Bibcode: 2011SPD....42.0305S Altcode: 2011BAAS..43S.0305S Of spectral diagnostics for the magnetic field in the solar chromosphere, the He I triplet at 1083 nm offers a comparatively simple means to determine both the magnitude and direction of the field vector. The triplet forms over a narrow range of heights when compared to strong optical lines, and recently the mechanisms that influence its polarization have been well characterized, thus allowing inversions of the magnetic field from observed Stokes profiles. We discuss recent work with the Facility Infrared Spectropolarimeter (FIRS) at the Dunn Solar Telescope (DST), New Mexico, USA to measure and infer the magnetic field vector of chromospheric fibrils. FIRS is designed to perform fast diffraction-limited dual-beam spectropolarimetry simultaneously at visible and infrared wavelengths through the use of multiple slits and narrowband filters. It can be operated in congress with the High Order Adaptive Optics (HOAO) system of the DST as well as with the Interferometric BiDimensional Spectropolarimeter (IBIS). Here we present high-resolution FIRS observations of chromospheric fibrils which employ the HOAO system under great seeing. We calibrate these observations for the full effect of the FIRS-DST combined analysis system on the Stokes vector which allow us to define the observed Stokes geometry with respect to solar coordinates. Full inversions of our measurements incorporating the effects of atomic polarization, the Hanle effect, and the Zeeman effect will be presented showing support for chromospheric fibrils that are aligned with the magnetic field direction. Title: Probing the Solar Atmosphere Using Oscillations of Infrared CO Spectral Lines Authors: Penn, Matthew J.; Schad, T.; Cox, E. Bibcode: 2011SPD....42.1702P Altcode: 2011BAAS..43S.1702P Oscillations were observed across the whole solar disk using the Doppler shift and line center intensity of spectral lines from the CO molecule near 4666 nm with the National Solar Observatory's McMath/Pierce solar telescope. Power, coherence, and phase spectra were examined, and diagnostic diagrams reveal power ridges at the solar global mode frequencies to show that these oscillations are solar p-modes. The phase was used to determine the height of formation of the CO lines by comparison with the IR continuum intensity phase shifts as measured in Kopp et al., 1992; we find the CO line formation height varies from 425 < z < 560 km as we move from disk center towards the solar limb 1.0 > mu > 0.5. The velocity power spectra show that while the sum of the background and p-mode power increases with height in the solar atmosphere as seen in previous work, the power in the p-modes only (background subtracted) decreases with height. The CO line depth weakens in regions of stronger magnetic fields, as does the p-mode oscillation power. Across most of the solar surface the phase shift is larger than the expected value of 90 degrees for an adiabatic atmosphere. We fit the phase spectra at different disk positions with a simple atmospheric model to determine that the acoustic cutoff frequency is about 4.5 mHz with only small variations, but that the thermal relaxation frequency drops significantly from 2.7 to 0 mHz at these heights in the solar atmosphere. Title: Spectropolarimetry of Chromospheric Magnetic and Velocity Structure Above Active Regions Authors: Schad, T. A.; Jaeggli, S. A.; Lin, H.; Penn, M. J. Bibcode: 2011ASPC..437..483S Altcode: 2011arXiv1101.0631S Active regions often host large-scale gas flows in the chromosphere presumably directed along curved magnetic field lines. Spectropolarimetric observations of these flows are critical to understanding the nature and evolution of their anchoring magnetic structure. We discuss recent work with the Facility Infrared Spectropolarimeter (FIRS) located at the Dunn Solar Telescope in New Mexico to achieve high-resolution imaging-spectropolarimetry of the Fe I lines at 630 nm, the Si I line at 1082.7 nm, and the He I triplet at 1083 nm. We present maps of the photospheric and chromospheric magnetic field vector above a sunspot as well as discuss characteristics of surrounding chromospheric flow structures. Title: IR spectroscopy of COmosphere dynamics with the CO first overtone band Authors: Schad, T. A.; Penn, M. J. Bibcode: 2010AN....331..589S Altcode: 2010arXiv1008.5375S We discuss observations of the weak first overtone (\Delta\nu=2) CO absorption band near 2300 nm with the U.S. National Solar Observatory Array Camera (NAC), a modern mid-infrared detector. This molecular band provides a thermal diagnostic that forms lower in the atmosphere than the stronger fundamental band near 4600 nm. The observed center-to-limb increase in CO line width qualitatively agrees with the proposed higher temperature shocks or faster plasma motions higher in the COmosphere. The spatial extent of chromospheric shock waves is currently at or below the diffraction limit of the available CO lines at existing telescopes. Five minute period oscillations in line strength and measured Doppler shifts are consistent with the p-mode excitation of the photospheric gas. We also show recent efforts at direct imaging at 4600 nm. We stress that future large-aperture solar telescopes must be teamed with improved, dynamic mid-infrared instruments, like the NAC, to capitalize on the features that motivate such facilities. Title: Structural Invariance of Sunspot Umbrae over the Solar Cycle: 1993 - 2004 Authors: Schad, T. A.; Penn, M. J. Bibcode: 2010SoPh..262...19S Altcode: 2010SoPh..tmp...22S; 2009arXiv0912.2370S Measurements of maximum magnetic flux, minimum intensity, and size are presented for 12 967 sunspot umbrae detected on the National Aeronautics and Space Administration/National Solar Observatory (NASA/NSO) spectromagnetograms between 1993 and 2004 to study umbral structure and strength during the solar cycle. The umbrae are selected using an automated thresholding technique. Measured umbral intensities are first corrected for center-to-limb intensity dependence. Log-normal fits to the observed size distribution confirm that the size-spectrum shape does not vary with time. The intensity - magnetic-flux relationship is found to be steady over the solar cycle. The dependence of umbral size on the magnetic flux and minimum intensity are also independent of the cycle phase and give linear and quadratic relations, respectively. While the large sample size does show a low-amplitude oscillation in the mean minimum intensity and maximum magnetic flux correlated with the solar cycle, this can be explained in terms of variations in the mean umbral size. These size variations, however, are small and do not substantiate a meaningful change in the size spectrum of the umbrae generated by the Sun. Thus, in contrast to previous reports, the observations suggest the equilibrium structure, as manifested by the invariant size-magnetic field relationship, as well as the mean size (i.e., strength) of sunspot umbrae do not significantly depend on the solar-cycle phase. Title: Evershed Outflow During Solar Cycle 23 Authors: Penn, Matthew J.; Schad, T. Bibcode: 2009SPD....40.0907P Altcode: We analyze several thousand Doppler observations of Evershed outflow in sunspot penumbrae taken at the National Solar Observatory's Kitt Peak Vacuum Telescope from 1993 to 2003. We compare the mean penumbral flow vector components with properties of the sunspot, latitude of the sunspot, and search for evolution of the components as a function of time. We discuss how our findings relate to measurements of sunspot magnetic helicity. Title: Solar Cycle Dependence of Umbral Magneto-Induced Line Broadening Authors: Schad, T. A.; Penn, M. J. Bibcode: 2008AGUSMSP41B..06S Altcode: Studies of the solar cycle dependence of peak umbral magnetic field strength have focused upon measurements of continuum intensity and the Zeeman splitting of infrared spectral lines. Here we extend the discussion into a measurement of effective line width using eleven years of spectromagnetograms from the Kitt Peak Vacuum Telescope (KPVT). The KPVT observed the 868.8 nm Fe I absorption line in opposing states of circular polarization between 1992 and 2003, deriving full-disk images of line-of-sight (LOS) velocity, LOS magnetic flux, continuum intensity, equivalent line width, and central line depth. We determine an effective spectral line width through a relation of the measured equivalent line widths and central line depths. Developing a basic model of the Stokes line profiles using the Seares formalism, we illustrate that a change in the effective line width within the umbra as determined using the KPVT data is consistent with the change in the Zeeman splitting. We discuss the effect of observed distance from disk center, stray light, and the unknown inclination angle of the magnetic field. Within individual sunspots observed near disk center, the determined effective line width decreases with distance from the umbral core consistent with the studied magnetic field gradient. Measurements of different sunspots show a clear dependence on umbral size consistent with previous studies of the umbral magnetic field. Using this effective line width as a diagnostic for magnetic field, we examine the dependence of maximum magnetic field strength on the phase of the solar cycle. We present a comprehensive statistical analysis using a sample size of over 3500 umbral measurements. Title: Alfven Waves in the Solar Corona Authors: Tomczyk, S.; McIntosh, S. W.; Keil, S. L.; Judge, P. G.; Schad, T.; Seeley, D. H.; Edmondson, J. Bibcode: 2007AGUFMSH21A0289T Altcode: We present observations of the coronal intensity, line-of-sight velocity, and linear polarization obtained in the FeXIII 1074.7 nm coronal emission line with the Coronal Multi-channel Polarimeter (CoMP) instrument. Analysis of these observations reveal ubiquitous upward propagating waves with phase speeds of 1-4 Mm/s and trajectories consistent with the direction of the magnetic field inferred from the linear polarization measurements. We can definitively identify these as Alfvén waves. An estimate of the energy carried by the waves that we spatially resolve indicates that they are unable to heat the solar corona, however, unresolved waves may carry sufficient energy. Title: Alfvén Waves in the Solar Corona Authors: Tomczyk, S.; McIntosh, S. W.; Keil, S. L.; Judge, P. G.; Schad, T.; Seeley, D. H.; Edmondson, J. Bibcode: 2007Sci...317.1192T Altcode: Alfvén waves, transverse incompressible magnetic oscillations, have been proposed as a possible mechanism to heat the Sun’s corona to millions of degrees by transporting convective energy from the photosphere into the diffuse corona. We report the detection of Alfvén waves in intensity, line-of-sight velocity, and linear polarization images of the solar corona taken using the FeXIII 1074.7-nanometer coronal emission line with the Coronal Multi-Channel Polarimeter (CoMP) instrument at the National Solar Observatory, New Mexico. Ubiquitous upward propagating waves were seen, with phase speeds of 1 to 4 megameters per second and trajectories consistent with the direction of the magnetic field inferred from the linear polarization measurements. An estimate of the energy carried by the waves that we spatially resolved indicates that they are too weak to heat the solar corona; however, unresolved Alfvén waves may carry sufficient energy. Title: Coronal Seismology: The Search for Propagating Waves in Coronal Loops Authors: Schad, Thomas A.; Seeley, D.; Keil, S. L.; Tomczyk, S. Bibcode: 2007AAS...210.9113S Altcode: 2007BAAS...39Q.206S We report on Doppler observations of the solar corona obtained in the Fe XeXIII 1074.7nm coronal emission line with the HAO Coronal Multi-Channel Polarimeter (CoMP) mounted on the NSO Coronal One Shot coronagraph located in the Hilltop Facility of NSO/Sacramento Peak. The COMP is a tunable filtergraph instrument that records the entire corona from the edge of the occulting disk at approximately 1.03 Rsun out to 1.4 Rsun with a spatial resolution of about 4” x 4”. COMP can be rapidly scanned through the spectral line while recording orthogonal states of linear and circular polarization. The two dimensional spatial resolution allows us to correlate temporal fluctuations observed in one part of the corona with those seen at other locations, in particular along coronal loops. Using cross spectral analysis we find that the observations reveal upward propagating waves that are characterized by Doppler shifts with rms velocities of 0.3 km/s, peak wave power in the 3-5 mHz frequency range, and phase speeds 1-3 Mm/s. The wave trajectories are consistent with the direction of the magnetic field inferred from the linear polarization measurements. We discuss the phase and coherence of these waves as a function of height in the corona and relate our findings to previous observations. The observed waves appear to be Alfvenic in character.

"Thomas Schad was supported through the National Solar Observatory Research Experiences for Undergraduate (REU) site program, which is co-funded by the Department of Defense in partnership with the National Science Foundation REU Program." Daniel Seeley was supported through the National Solar Observatory Research Experience for Teachers (RET) site program, which is funded by the National Science Foundation RET program.