Bain, Hazel Miller
Hard X-ray and radio studies of solar flares.
PhD thesis, University of Glasgow.
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Combined X-ray and radio observations of the Sun provide powerful diagnostics of particle acceleration and transport effects during solar flares. In this thesis we present observations of two solar flares. In the first event we report what we believe to be the first observation of hard X-ray emission formed in a coronal, flare-related jet. Occurring on the 22nd of August 2002, the event was observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and the Nobeyama Radioheliograph (NoRH) and Polarimeters (NoRP). During the impulsive phase RHESSI observed significant hard X-ray emission to energies as high as 30-50 keV in the jet. RHESSI spectroscopy shows a powerlaw spectrum with a spectral index of ~4 and NoRH images reveal radio emission at 17 GHz and 34 GHz co-spatial with the hard X-ray emission, thus supporting the evidence for nonthermal emission in the jet.
The second event occurred on the 24th of August 2002 and was also observed by RHESSI and NoRH. The size and orientation of the flare, which occurred on the west limb of the Sun, make it particularly interesting to study. At both NoRH frequencies emission is observed at all points along a flare loop such that the looptop and footpoint emission are clearly separated. We present observations of the flare decay phase to investigate the long term evolution of the event. In particular we follow the evolution of relevant plasma parameters which are used as an input to a 3D gyrosynchrotron model in an attempt to reproduce the observed emission at radio wavelengths.
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