Browsing by Author "Scott, Roger Benezet"

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Analytical and numerical modeling of coronal supra-arcade fan structures
(Montana State University - Bozeman, College of Letters & Science, 2016) Scott, Roger Benezet; Chairperson, Graduate Committee: David E. McKenzie; Dana W. Longcope and David E. McKenzie were co-authors of the article, 'Peristaltic pumping near post-CME supra-arcade current sheets' in the journal 'The astrophysical journal' which is contained within this thesis.; Dana W. Longcope and David E. McKenzie were co-authors of the article, 'Numerical simulations of plasma dynamics in the vicinity of a retracting flux tube' submitted to the journal 'The astrophysical journal' which is contained within this thesis.; David E. McKenzie and Dana W. Longcope were co-authors of the article, 'Inferring the magnetohydrodynamic structure of solar flare supra-arcade plasmas from a data assimilated field transport model' submitted to the journal 'The astrophysical journal' which is contained within this thesis.
Among the myriad of interesting phenomenon in the solar corona is the highly dynamic region above active region arcades, commonly referred to as the "supra-arcade" region. In the minutes and hours following the formation of an arcade of post-flare loops, we commonly observe the development of a curtain like structure, with spiny rays of enhanced emission in X-Ray and extreme ultra-violet. Additionally, these structures often exhibit dynamics over a variety of length scales, from large-amplitude coherent transverse oscillations, to the appearance of low-emission columns that seem to descend toward the solar limb. The wealth of dynamical aspects that are present in the supra-arcade seems to indicate that the plasma there is subject to a complex balance of influencing factors, which makes it difficult to develop a self-consistent hypothesis for describing all of the various features simultaneously. In this work we undertake to explain one such behavior as an isolated phenomenon. We argue that the descending low-emission voids, sometimes called Supra-Arcade Downflows (SADs) are consistent with the formation of a particular kind of shock in the vicinity of a retracting element of reconnected magnetic flux. We then use numerical simulations to expand this result to a broader parameter space, as well as investigating the details of a variety of other behavioral regimes. Finally, in an effort to understand the broader dynamics of the supra-arcade region, we undertake a study that incorporates imaging data into a numerical simulation, which can then be used to estimate the ambient plasma parameters in the supra-arcade region. In this way we show that the balance of influencing factors in the supra-arcade is indeed highly dynamic and that the simplifications offered in certain extremes of magnetohydrodynamics are ill-applied in this case.