The acceleration and transport of electron populations in solar flares

QB Astronomy;QC Physics

Stackhouse, Duncan James ; Kontar, Eduard P.

University:University of Glasgow

Department:School of Physics and Astronomy

关键词: Sun, flares, particle acceleration.;   

Others  :  http://theses.gla.ac.uk/7939/1/2017stackhousephd.pdf

来源: University of Glasgow

【 摘 要 】

Solar flares are known to accelerate electrons to high energies, resulting in the movement of these particles throughout the Sun's atmosphere. Although this has been known since the middle of the last century, it is still unknown quite how these particles are accelerated, how they are transported and where the energization takes place. This thesis is concerned with these key questions of solar physics, using a mixture of analytical and numerical modellingin conjunction with the valuable diagnostic tool of the X-rays observed by the Reuven-Ramaty High Energy Solar Spectroscopic Imager (RHESSI). First, imaging spectroscopy with RHESSI is shown, focussing on how to infer to the underlying electron distribution producing the X-ray photons and how this can be used to produce more realistic models. Secondly, a model where the region in which the electrons are accelerated, stopped and emit X-rays is the same is presented, driven specifically by observations of such sources by RHESSI. This admits a steady-state kappa distribution solution and it is shown that the relaxation of an originally thermal Maxwellian population of electrons to this final state proceeds as a wavefront in velocity space. Finally, a model which takes account of recent studies showing the extended nature of the acceleration region within the loops of solar flares is considered. For the first time the intrinsic spatial dependencies of acceleration and transport are explicitly studied, showing the importance of accounting for this in future modelling of solar flares.