Sub-second variations of HXR and H-alpha flare emission

Abstract

For a series of electron beam pulses, we have computed the time-dependent chromospheric heating and the corresponding hard X-ray (HXR) flux. Moreover, by solving the time-dependent NLTE problem for hydrogen, we theoretically predict the Ha-line intensity variations on sub-second time scales. Both HXR-fluxes and Ha wing intensities do exhibit a spiky behaviour, consistent with short pulse-beam heating. However, the spikes in Ha are unexpectedly ‘inverse’, i.e. the line intensity decreases during the beam heating. They correlate rather well with HXR emission peaks computed for 24 keV channel. We compare our theoretical results with recent observations of Kiplinger et al. (1991).