Pulse heating of the solar chromosphere during flares

The problem of nonstationary hydrodynamic plasma flow under impulsive heating of the chromosphere by large thermal fluxes and accelerated particles is solved numerically. Taking unto account all essential dissipative processes as well as heat flux saturation, the electron and ion temperature, the density and the hot flare plasma velocity are calculated. It is shown that in the case of heating by thermal flux to anomalous high temperatures (T> or approximately 108 K) the thermal bremsstrahlung radiation spectrum in the hard X-rays is well fitted by an exponential law