Beam-Driven Return Current Instability in Solar Flares

Astronomy

Cromwell, David

University:University of Glasgow

关键词: Astronomy;   

Others  :  http://theses.gla.ac.uk/77555/1/10995603.pdf

来源: University of Glasgow

【 摘 要 】

It is generally accepted that thick-target electron beams play a major role in the production, by collisional bremsstrahlung, of hard X-ray bursts during the impulsive phase of solar flares. The large electron flux demanded by the observed X-ray photon flux in such an interpretation requires that a beam-neutralising return current be set up. Ohmic dissipation of this return current increases the energy loss of the beam electrons in addition to the energy lost in Coulomb collisions with the ambient plasma. We investigate the effect on the hard X-ray signature when the return current is unstable to the generation of low-frequency electrostatic plasma waves (i.e. waves giving rise to anomalous plasma resistivity). Specifically, we compare the thermal emission, which rises due to enhanced plasma heating, with the non-thermal yield from the beam, which falls when turbulence is excited.