Theses and Dissertations at Montana State University (MSU)
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Item Modeling and understanding coronal loop dynamics during solar flares(Montana State University - Bozeman, College of Letters & Science, 2020) Unverferth, John Edward, IV; Chairperson, Graduate Committee: Dana W. Longcope; Dana Longcope was a co-author of the article, 'Effects of the canopy and flux tube anchoring on evaporation flow of a solar flare' in the journal 'The astrophysical journal' which is contained within this dissertation.; Dana Longcope was a co-author of the article, 'Modeling observable differences in flare loop evolution due to reconnection location and current sheet structure' in the journal 'The astrophysical journal' which is contained within this dissertation.; Dana Longcope was a co-author of the article, 'Flux tube interactions as a cause for sub-alfvenic reconnection outflow' submitted to the journal 'The astrophysical journal' which is contained within this dissertation.Magnetic reconnection is widely considered to be the mechanism behind solar flares. Models powered by reconnection manage to explain many of the observational features seen in a flare. However, these models miss or contradict important elements of the flare. Here we consider three effects overlooked by models. First, the role played by the magnetic canopy in determining the chromospheric response in a flare. Second, how variations in magnetic field strength along the current sheet impact the evolution of are loops. Third, how flux tube interactions with the current sheet can lead to sub-Alfvenic motion, bringing dynamics in line with observations. These three effects were investigated with the use of one dimensional and thin flux tube models. This allowed for the dynamics to be considered independent of the reconnection process that generated the flux tubes. The canopy interaction revealed that the creation of an expansion followed by a constriction, a chamber in the flux tube, leads to multiple solutions. The solutions include smooth flow and standing shocks in the chamber. The standing shock increases the emission of the flow, as well as slowing it to subsonic speeds. The shocked solution shifts the ensemble of flux tubes to have a distribution that would indicate slower speeds than expected. The structure of the current sheet magnetic field leaves a signature on the flux tube. Each case leads to a difference in emission. Retraction through a constricting field creating a plug of material leading to a bright emission in the apex. This contrasts with retraction through an expanding field which generates high temperatures, but as a fainter emission. The interaction of drag in the current sheet allowed for the retraction to proceed at slower rates. The slower retraction matches observations of features in flares more accurately. The slower retraction also increases the brightness of the synthetic current sheet. This increased brightness brings the current sheet closer to the observed brightness. These investigations found that there was benefit to considering these additional effects. Each one of these effects was found to bring the models more in line to what observations note.Item Partitioning of reactive oxygen species via the re-oxidation of electron transfer flavoprotein(Montana State University - Bozeman, College of Letters & Science, 2019) Austvold, Chase Kennor; Chairperson, Graduate Committee: Edward DratzThe biology of Reactive Oxygen Species are poorly understood. Within a healthy cell, Reactive Oxygen Species behave as signaling molecules, although overproduction leads to oxidative damage. In order to understand when the overproduction of Reactive Oxygen Species takes place, or leads to oxidative damage, the elementary step of quantification becomes necessary. Electron Transfer Flavoprotein is a known Reactive Oxygen Species producing enzyme and was studied. Electron Transfer Flavoprotein is a key-player within the production of energy within the eukaryotic mitochondria. The redox nature of Electron Transfer Flavoprotein's catalytic cofactor, flavin adenine dinucleotide produced two types of ROS; the superoxide anion (O 2 °-) and hydrogen peroxide (H 2 O 2). Electron Transfer Flavoprotein produced roughly five-fold more O 2 °-compared to H 2 O 2 as the enzyme became oxidized. It has been put forward that the production of these two Reactive Oxygen Species is dictated by the formation of a radical pair between the flavin adenine dinucleotide of Electron Transfer Flavoprotein and molecular oxygen. Two types of radical pairs can be formed, either in a triplet or singlet state, and the rate in which these states occur can be influenced by a static magnetic field. Therefore, the effect of a magnetic field on these products was also studied. Upon the suppression of magnetic field strength, the production of H 2 O 2 decreased and a proportional increase of O 2 °-was observed.Item Statistical properties of separators in model active regions(Montana State University - Bozeman, College of Letters & Science, 1998) Welsch, Brian ThomasItem Coupling the photospheric and coronal magnetic fields : observations and analysis(Montana State University - Bozeman, College of Letters & Science, 1998) Handy, Brian NealItem Synthetic x-ray imager for solar plasma loops(Montana State University - Bozeman, College of Engineering, 1998) Lundberg, Steven KennethItem Magnetic helicity transport in the quiet Sun(Montana State University - Bozeman, College of Letters & Science, 2002) Welsch, Brian ThomasItem Twist in coronal magnetic fields(Montana State University - Bozeman, College of Letters & Science, 2010) Malanushenko, Anna Viktorovna; Chairperson, Graduate Committee: Dana W. LongcopeTwist of magnetic field is believed to play important role in driving instabilities that result in eruptive events on the Sun. This thesis provides different methods to measure twist in the solar corona. First, given a model of coronal field, twist of a magnetic domain (i.e., a volume that contains all field lines connecting two regions of interest in the photosphere) is well studied for cases when the domain is a thin cylinder. For cases when such approximation is inapplicable a generalization of twist can be derived from a quantity called additive self-helicity. I develop explicit numerical methods to compute generalized twist. I also demonstrate that such a quantity sets a threshold on kink instability like the traditional twist does for thin cylinders. In a more realistic scenario, coronal magnetic field is not known and so neither is its helicity. There are two principal methods to overcome this problem. The first is to integrate helicity flux across the photosphere (as helicity is believed to be approximately conserved in the corona) using magnetic field on Sun's surface. There is little published evidence as yet that coronal helicity indeed corresponds to its integrated photospheric flux. The second is to extrapolate the coronal magnetic field using surface measurements as boundary conditions and use this extrapolation for helicity computation; for fields with complicated structure such extrapolations are extremely challenging and suffer from major drawbacks. I develop a method to estimate twist of coronal fields without attempting complicated extrapolations or studying helicity flux. The method builds a simple uniformly-twisted magnetic field and adjusts its properties until there is one line in this field that matches one coronal loop; this is repeated for all evident coronal loops resulting in twist measurements for each individual loop. I use this method to demonstrate that the rate of change of twist in the solar corona is indeed approximately equal to the one derived from photospheric helicity flux. The results of this dissertation are useful for better understanding of magnetic topology in general. They are also extremely promising for extrapolating coronal magnetic fields. Measurements of coronal twist might aid in predicting magnetic instabilities.