Goff, C.P.; (2005) X-ray studies of flaring magnetic structures. Doctoral thesis , University of London.

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Abstract

This thesis studies non-thermal emission from flaring magnetic structures by looking at HXR emission from flare footpoints at a faint X-ray source above a flare loop and finally at radio emission generated by eruptions. By complementing high quality data from recent missions with data from older instrumentation, studies were performed to compare with accepted models. The relation between Hard X-ray footpoint emission and magnetic field strength in a sample of 32 flares was studied in order to investigate the effects of the magnetic field on the transport of accelerated electrons. It was found that one third of compact flares studied had stronger footpoints in stronger magnetic regions whereas the reverse is anticipated from magnetic trapping arguments. On 16th April 2002, a limb flare was studied in many wavelengths. This provided an opportunity to study an erupting filament from the low corona and into interplanetary space. RHESSI identified a moving X-ray source associated with a rising filament, confirming the plasmoid definition of Tsuneta (1997). The velocity profile of the filament was determined along with its exponential acceleration. This suggested that an instability was responsible for eruption, possibly the kink instability. Doppler shifts were observed on either side of the filament as it crossed the slit field of view, suggesting helical flows and thus a flux rope. A succession of quadrupolar flares, followed by an LDE were then studied. An associated CME was seen and appeared linked to the quadrupolar flares which should re main confined. The flaring region triggered loop expansion, which interacted with a neighbouring large-scale streamer. This led to a fast CME front, which weakened the restraining field above the active region filaments allowing a partial filament eruption. Although at first glance the observations appeared contradictory it was demonstrated that the quadrupolar flares remained confined while triggering a large-scale eruption.

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