Scholarly Work - Physics
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/3458
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Item First Flight of the EUV Snapshot Imaging Spectrograph (ESIS)(American Astronomical Society, 2022-10) Parker, Jacob D.; Smart, Roy T.; Kankelborg, Charles; Winebarger, Amy; Goldsworth, NelsonThe Extreme-ultraviolet Snapshot Imaging Spectrograph (ESIS) launched on a sounding rocket from White Sands Missile Range on 2019 September 30. ESIS is a computed tomography imaging spectrograph (CTIS) designed to map emission line profiles across a wide field of view, revealing the structure and dynamics of small-scale transient events that are prevalent at transition region temperatures. In this paper, we review the ESIS instrument, mission, and data captured. We demonstrate how this unique data set can be interpreted qualitatively and further present some initial quantitative inversions of the data. Using a multiplicative algebraic reconstruction technique, we combine information from all four ESIS channels into a single spatial–spectral cube at every exposure. We analyze two small explosive events in the O v 629.7 Å spectral line with jets near ±100 km s−1 that evolve on 10 s timescales and vary significantly over small spatial scales. Intriguingly, each of these events turns out to be a bimodal (red+blue) jet with outflows that are asymmetric and unsynchronized. We also present a qualitative analysis of a small jetlike eruption captured by ESIS and draw comparisons to previously observed mini-filament eruptions. In 5 minutes of observing time, ESIS captured the spatial and temporal evolution of tens of these small events across the ∼11.′5 field of view, as well as several larger extended eruptions, demonstrating the advantage of CTIS instruments over traditional slit spectrographs in capturing the spatial and spectral information of dynamic solar features across large fields of view.Item Instrument Calibration of the Interface Region Imaging Spectrograph (IRIS) Mission(2018-11) Wulser, J. P.; Jaeggli, Sarah A.; De Pontieu, Bart; Tarbell, Ted D.; Boerner, P.; Freeland, S.; Liu, W.; Timmons, R.; Brannon, Sean R.; Kankelborg, Charles; Madsen, C.; McKillop, Sean; Prchlik, J.; Saar, Steven; Schanche, N.; Bryans, P.; Wiesmann, M.The Interface Region Imaging Spectrograph (IRIS) is a NASA small explorer mission that provides high-resolution spectra and images of the Sun in the 133-141nm and 278-283nm wavelength bands. The IRIS data are archived in calibrated form and made available to the public within seven days of observing. The calibrations applied to the data include dark correction, scattered light and background correction, flat fielding, geometric distortion correction, and wavelength calibration. In addition, the IRIS team has calibrated the IRIS absolute throughput as a function of wavelength and has been tracking throughput changes over the course of the mission. As a resource for the IRIS data user, this article describes the details of these calibrations as they have evolved over the first few years of the mission. References to online documentation provide access to additional information and future updates.Item The Unresolved Fine Structure Resolved: IRIS Observations of the Solar Transition Region(2014-10) Hansteen, Viggo H.; De Pontieu, B.; Carlsson, Mats; Lemen, James; Title, Alan M.; Boerner, P.; Hurlburt, Neal E.; Tarbell, Ted D.; Wuelser, Jean-Pierre; Pereira, Tiago M. D.; De Luca, E.E.; Golub, Leon; McKillop, Sean; Reeves, Kathy K.; Saar, Steven; Testa, Paola; Tian, Hui; Kankelborg, Charles; Jaeggli, Sarah; Kleint, Lucia; Martínez-Sykora, J.The heating of the outer solar atmospheric layers, i.e., the transition region and corona, to high temperatures is a longstanding problem in solar (and stellar) physics. Solutions have been hampered by an incomplete understanding of the magnetically controlled structure of these regions. The high spatial and temporal resolution observations with the Interface Region Imaging Spectrograph (IRIS) at the solar limb reveal a plethora of short, lowlying loops or loop segments at transitionregion temperatures that vary rapidly, on the time scales of minutes. We argue that the existence of these loops solves a longstanding observational mystery. At the same time, based on comparison with numerical models, this detection sheds light on a critical piece of the coronal heating puzzle.Item A PSF equalization technique for the Multi-Order Solar Extreme-ultraviolet Spectrograph (MOSES)(2015-10) Atwood, Shane; Kankelborg, CharlesThe Multi-Order Solar Extreme Ultraviolet Spectrograph (MOSES) is a rocket-borne slitless imaging spectrometer, designed to observe He II (30.4 nm) emission in the solar transition region. This instrument forms three simultaneous images at spectral orders m=−1, 0, +1 over an extended field of view (FOV). A multi-layer coating on the grating and thin film filters in front of the detectors defines the instrument passband. Each image contains a unique combination of spectral and spatial information. Our overarching goal in analyzing these data is to estimate a spectral line profile at every point in the FOV. Each spectral order has different image geometry, and therefore different aberrations. Since the point spread function (PSF) differs between any two images, systematic errors are introduced when we use all three images together to invert for spectral line profiles. To combat this source of systematic error, we have developed a PSF equalization scheme. Determination of the image PSFs is impractical for several reasons, including changes that may occur due to vibration during both launch and recovery operations. We have therefore developed a strategy using only the solar images obtained during flight to generate digital filters that modify each image so that they have the same effective PSF. Generation of the PSF equalization filters does not require that the PSFs themselves be known. Our approach begins with the assumption that there are only two things that cause the power spectra of our images to differ: (1) aberrations; and (2) the FOV average spectral line profile, which is known in principle from an abundance of historical data. To validate our technique, we generate three synthetic images with three different PSFs. We compare PSF equalizations performed without knowledge of the PSF to corrections performed with that knowledge. Finally, we apply PSF equalization to solar images obtained in the 2006 MOSES flight and demonstrate the removal of artifacts.Item Using local correlation tracking to recover solar spectral information from a slitless spectrograph(2015-10) Courrier, Hans T.; Kankelborg, CharlesThe Multi-Order Solar EUV Spectrograph (MOSES) is a sounding rocket instrument that utilizes a concave spherical diffraction grating to form simultaneous solar images in the diffraction orders m = 0, +1, and −1. The large 2D field of view allows a single exposure to capture spatial and spectral information for large, complex solar features in their entirety. Most of the solar emission within the instrument passband comes from a single bright emission line. The m = 0 image is simply an intensity as a function of position, integrated over the passband of the instrument. Dispersion in the images at m = ±1 leads to a field-dependent displacement that is proportional to Doppler shift. Our goal is to estimate the Doppler shift as a function of position for every exposure. However, the interpretation of the data is not straightforward. Imaging an extended object such as the Sun without an entrance slit results in the overlapping of spectral and spatial information in the two dispersed images. We demonstrate the use of local correlation tracking as a means to quantify the differences between the m = 0 image and either one of the dispersed images. The result is a vector displacement field that may be interpreted as a measurement of the Doppler shift. Since two dispersed images are available, we can generate two independent Doppler maps from the same exposure. We compare these to produce an error estimate.Item A Transition Region Explosive Event Observed in He II with the MOSES Sounding Rocket Authors(2010-07-27) Fox, J. Lewis; Kankelborg, Charles; Thomas, Roger J.Transition region explosive events (EEs) have been observed with slit spectrographs since at least 1975, most commonly in lines of C IV (1548 Å, 1550 Å) and Si IV (1393 Å, 1402 Å). We report what we believe to be the first observation of a transition region EE in He II 304 Å. With the MultiOrder Solar EUV Spectrograph (MOSES) sounding rocket, a novel slitless imaging spectrograph, we are able to see the spatial structure of the event. We observe a bright core expelling two jets that are distinctly noncollinear, in directions that are not antiparallel. The jets have skyplane velocities of order 75 km s1 and lineofsight velocities of +75 km s1 (blue) and 30 km s1 (red). The core is a region of high nonthermal Doppler broadening, characteristic of EEs, with maximal broadening 380 km s1 FWHM. It is possible to resolve the core broadening into red and blue lineofsight components of maximum Doppler velocities +160 km s1 and 220 km s1. The event lasts more than 150 s. Its properties correspond to the larger, longlived, and more energetic EEs observed in other wavelengths.Item Exploring the interface between the Sun's surface and corona(2012-04) Kankelborg, CharlesWe present the science case for a broadband Xray imager with highresolution spectroscopy, including simulations of Xray spectral diagnostics of both active regions and solar flares. This is part of a trilogy of white papers discussing science, instrument (Bandler et al. 2010), and missions (Bookbinder et al. 2010) to exploit major advances recently made in transitionedge sensor (TES) detector technology that enable resolution better than 2 eV in an array that can handle high count rates. Combined with a modest Xray mirror, this instrument would combine arcsecondscale imaging with highresolution spectra over a field of view sufficiently large for the study of active regions and flares, enabling a wide range of studies such as the detection of microheating in active regions, ionresolved velocity flows, and the presence of nonthermal electrons in hot plasmas. It would also enable more direct comparisons between solar and stellar soft Xray spectra, a waveband in which (unusually) we currently have much better stellar data than we do of the Sun.Item National Student Solar Spectrograph Competition overview(2012-10) Larimer, Randal M.; Des Jardins, Angela; Shaw, Joseph A.; Kankelborg, Charles; Palmer, Christopher; Springer, Larry; Key, Joey S.The yearly National Student Solar Spectrograph Competition (NSSSC) is Montana Space Grant Consortium's Education and Public Outreach (EP/O) Program for NASA's Interface Region Imaging Spectrograph (IRIS) mission. The NSSSC is designed to give schools with less aerospace activity such as Minority Serving Institutions and Community Colleges an opportunity for hands on real world research experience. The NSSSC provides students from across the country the opportunity to work as part of an undergraduate interdisciplinary team to design, build and test a ground based solar spectrograph. Over the course of nine months, teams come up with their own science goals and then build an instrument to collect data in support of their goals. Teams then travel to Bozeman, MT to demonstrate their instruments and present their results in a competitive science fair environment. This paper and poster will discuss the 2011-2012 competition along with results as well as provide information on the 2012 -2013 competition opportunities.Item Fast Differential Emission Measure Inversion of Solar Coronal Data(2012-10) Plowman, Joseph; Kankelborg, Charles; Martens, PetrusWe present a fast method for reconstructing differential emission measures (DEMs) using solar coronal data. The method consists of a fast, simple regularized inversion in conjunction with an iteration scheme for removal of residual negative emission measure. On average, it computes over 1000 DEMs s1 for a sample active region observed by the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory, and achieves reduced chisquared of order unity with no negative emission in all but a few test cases. The high performance of this method is especially relevant in the context of AIA, which images of order one million solar pixels per second. This paper describes the method, analyzes its fidelity, compares its performance and results with other DEM methods, and applies it to an active region and loop observed by AIA and by the Extremeultraviolet Imaging Spectrometer on Hinode.Item High‐resolution Observations of the Shock Wave Behavior for Sunspot Oscillations with the Interface Region Imaging Spectrograph(2014-05) Tian, Hui; DeLuca, E.E.; Reeves, Kathy K.; McKillop, Sean; De Pontieu, Bart; Martínez-Sykora, J.; Carlsson, Mats; Hansteen, Viggo H.; Kleint, Lucia; Cheung, M.; Golub, Leon; Saar, Steven; Testa, Paola; Weber, Mark A.; Lemen, James; Title, Alan M.; Boerner, P.; Hurlburt, Neal E.; Tarbell, Ted D.; Wülser, Jean-Pierre; Kankelborg, Charles; Jaeggli, Sarah; McIntosh, Scott W.We present the first results of sunspot oscillations from observations by the Interface Region Imaging Spectrograph. The strongly nonlinear oscillation is identified in both the slitjaw images and the spectra of several emission lines formed in the transition region and chromosphere. We first apply a single Gaussian fit to the profiles of the Mg II 2796.35 Å, C II 1335.71 Å, and Si IV 1393.76 Å lines in the sunspot. The intensity change is ~30%. The Doppler shift oscillation reveals a sawtooth pattern with an amplitude of ~10 km s1 in Si IV. The Si IV oscillation lags those of C II and Mg II by ~3 and ~12 s, respectively. The line width suddenly increases as the Doppler shift changes from redshift to blueshift. However, we demonstrate that this increase is caused by the superposition of two emission components. We then perform detailed analysis of the line profiles at a few selected locations on the slit. The temporal evolution of the line core is dominated by the following behavior: a rapid excursion to the blue side, accompanied by an intensity increase, followed by a linear decrease of the velocity to the red side. The maximum intensity slightly lags the maximum blueshift in Si IV, whereas the intensity enhancement slightly precedes the maximum blueshift in Mg II. We find a positive correlation between the maximum velocity and deceleration, a result that is consistent with numerical simulations of upward propagating magnetoacoustic shock waves.