Influence of photospheric back-scatteron flare hard x-ray diagnostics.

QB Astronomy;QC Physics

Alexander, Robert Calum ; Brown, John C.

University:University of Glasgow

Department:School of Physics and Astronomy

关键词: Solar Flare Spectroscopy, Solar Flare Hard X-Ray Diagnostics, Solar Photospheric Back-Scatter, Compton Back-Scatter, Albedo, Green’s Function Albedo Correction, Energy Dependent Anisotropic Primary Photon Emission, Hemispheric Eddington Anisotropic Approximation, Photon Spectra, Electron Spectra;   

Others  :  http://theses.gla.ac.uk/1707/1/2010alexanderphd.pdf

来源: University of Glasgow

【 摘 要 】

In this thesis I present the results of studies on the influence of solar photosphericback–scatter on Hard X–Ray (HXR) flare diagnostics. Specifically the thesis presentedis concerned with the effect of back–scatter photons upon the morphologyof the Hard X–Ray photon spectrum and its effect on the inferred parent electronspectrum.I present a theoretical investigation into Compton reflected HXR photons,known as the photospheric Albedo, and explore the effect of photospheric albedoon observations of global flare hard X-ray spectra for isotropic emission. I examine,for the Kramers cross-section, the consequences of ignoring the albedocorrection in using observed spectra to infer flare source electron spectra for thinand thick target interpretations and show that the effects are very significant interms of inferred spectral shape, especially for hard spectra.I extend this investigation to consider the effect of the photospheric albedoon observations of global flare hard X-ray spectra for anisotropic primary photonemission by examining, for the Kramers cross-section, the consequences of ignoringthe albedo correction in using observed spectra to infer flare source electronspectra for thin and thick target interpretations. For an energy dependent multiplierα I find that the results for anisotropic emission are similar in shape toisotropic emission when I assume a linear model for the anisotropy.I then explore two complementary techniques for determining the Comptonback-scattered component of the observed photon spectrum using a model independentGreens function approach. The first is a matrix based technique developedby Kontar & Brown (2006) which I extend to include anisotropic primaryphoton emission using an Eddington hemispheric approach along with an empiricalfit to published data. The second is a full radiative transfer Greens functionapproach developed by Poutanen et al. (1996) which I also extend to includeanisotropic primary photon emission again using an empirical fit to publisheddata.In both cases I investigate how anisotropic primary photon emission effectsthe observed photon spectrum by studying the differences in the size and shapeof the albedo.In the final chapter I use the results from the anisotropic Eddington hemisphericGreens function approach and the anisotropic full radiative transfer Greensfunction approach to investigate the findings published in Kontar & Brown (2006)using the Stereoscopic electron spectroscopy technique.I conclude from the results of this comparison that doing a full anisotropicscattering properly does not fundamentally change the findings of Kontar amp; Brownwhich are specifically that the electron distribution is nearly isotropicto such a degree of confidence that it casts doubt on models which are based uponbeaming such as the collisional thick target (Brown 1971).