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Item Modeling the effects of flare energy release and transport through chromospheric condensation and ultraviolet coronal emission(Montana State University - Bozeman, College of Letters & Science, 2022) Ashfield, William Henry, IV; Chairperson, Graduate Committee: Dana W. Longcope; This is a manuscript style paper that includes co-authored chapters.Solar flares arise from the release of magnetic free energy through reconnection. A fraction of this energy travels from the corona to the lower solar atmosphere, heating the plasma and driving downflows -- chromospheric condensations -- critical to our understanding of flare energetics. While flare models with impulsive energy injections have successfully reproduced observed chromospheric responses, they typically focus on heating via electron beam deposition, neglecting other modes of energy transport. Observations of long-duration coronal emission in the extreme ultraviolet have further indicated a two-phase energy release process: impulsive energy deposition followed by persistent low-rate heating. As flare energy release and transport are measured by the indirect signatures of condensation and coronal emissions, flare models must account for these phenomena' behavior to infer the characteristics of reconnection. We first investigated the chromospheric response to a constant flare energy flux using a thermal flare model driven by in-situ coronal heating. An analytical expression for the condensation velocity was developed and found to be well described by the observed characteristic properties, allowing condensation to serve as a diagnostic for both the energy flux at the reconnection site and the pre-flare density scale height of the chromosphere. These results were tested on condensations observed in Si IV 1403 ?A spectral line redshifts. A Gaussian heating profile, inferred from footpoint UV emission corresponding to the measured downflows, was used to drive a one-dimensional simulation from which Si IV spectra were synthesized. Although the synthetic velocity evolution agreed reasonably well with observation, thus providing evidence for our model's validity, the condensation's timescale was found to be independent of the time scale of the energy release. To address coronal EUV emission signatures, long-duration flare heating was modeled through the slow dissipation of turbulent Alfven waves. Motivated by observations of supra-arcade downflows, the waves were initiated by retracting newly-reconnected flux tubes through a current sheet and dissipated through their non-linear interaction. EUV lightcurves synthesized from simulation results reproduced emissions that decayed in 40 minutes. This model, created self-consistently from reconnection-powered flare energy release, offers a possible explanation for the outstanding problem of persistent flare emission.Item Observations and modeling of plasma flows driven by solar flares(Montana State University - Bozeman, College of Letters & Science, 2016) Brannon, Sean Robert; Chairperson, Graduate Committee: Dana W. Longcope; Dana Longcope was a co-author of the article, 'Modeling properties of chromospheric evaporation driven by thermal conduction fronts from reconnection shocks' in the journal 'The astrophysical journal' which is contained within this thesis.; Dana W. Longcope and Jiong Qiu were co-authors of the article, 'Spectroscopic observations of evolving flare ribbon substructure suggesting origin in current sheet waves' in the journal 'The astrophysical journal' which is contained within this thesis.One of the fundamental statements that can be made about the solar atmosphere is that it is structured. This structuring is generally believed to be the result of both the arrangement of the magnetic field in the corona and the distribution of plasma along magnetic loops. The standard model of solar flares involves plasma transported into coronal loops via a process known as chromospheric evaporation, and the resulting evolution of the are loops is believed to be sensitive to the physical mechanism of energy input into the chromosphere by the are. We present here the results of three investigations into chromospheric plasma flows driven by solar are energy release and transport. First, we develop a 1-D hydrodynamic code to simulate the response of a simplified model chromosphere to energy input via thermal conduction from reconnection-driven shocks. We use the results from a set of simulations spanning a parameter space in both shock speed and chromospheric-to-coronal temperature ratio to infer power-law relationships between these quantities and observable evaporation properties. Second, we use imaging and spectral observations of a quasi-periodic oscillation of a are ribbon to determine the phase relationship between Doppler shifts of the ribbon plasma and the oscillation. The phase difference we find leads us to suggest an origin in a current sheet instability. Finally, we use imaging and spectral data of an on-disk are event and resulting are loop plasma flows to generally validate the standard picture of are loop evolution, including evaporation, cooling time, and draining downflows, and we use a simple free-fall model to produce the first direct comparison between observed and synthetic downflow spectra.