The collisional relaxation of electrons in a finite temperature plasma and the diagnostics of solar flare accelerated electrons from X-ray spectroscopy and imaging
Natasha Jeffrey
University of Glasgow
Eduard Kontar, Nicolas Bian and Gordon Emslie
During a solar flare, a large number of electrons are accelerated, and their properties deduced by X-ray observations with instruments such as the Ramaty High Energy Solar Spectroscopic Imager (RHESSI). The properties of accelerated electrons are changed when they encounter a dense atmosphere, where they lose energy collisionally, mainly to other electrons. Therefore, the properties of the accelerated electron distribution must be deduced via the application of a chosen model, which is frequently where electrons lose energy frictionally in a 'cold’ (electron energy much greater than the background temperature) high density region. However, such a model does not realistically account for the behaviour of accelerated electrons in a finite temperature ambient plasma (10s of megaKelvin in the corona) and the subsequent collisional diffusion and thermalization of electrons during a flare. I will discuss show how the inferred properties of the accelerated electron distribution from solar flare X-ray spectra, such as the injection rate and total energy content can be dramatically changed by accounting for the effects of collisional diffusion and thermalization. Particularly, such a model must be used to describe the observation of hot 20 MK, high density coronal X-ray sources, observed during a number of flares. The spatial changes of such coronal X-ray sources have been used to infer the properties of an electron acceleration region from X-ray imaging. The inferred properties of the acceleration region, such as size and number density, are altered by properly accounting for the collisional relaxation of electrons in a finite temperature plasma.