GAS-DYNAMIC RESPONSE OF THE ATMOSPHERE TO PULSE HEATING - 2-TEMPERATURE APPROXIMATION

Explosive evaporation of the chromosphere during powerful pulse flares is numerically modeled. Possible separation of electron and ion tempe ratures is taken into account. A column of the chromosphere with fixed pressure at its upper boundary is abruptly subject to heating, distri buted over the mass and lasting 10 s. Two phases of the process are co nfirmed: in the first tenths of a second, the temperature of the upper chromosphere increases, while its density remains almost unchanged; t hen, a quasiequilibrium flow of plasma forms, with a jump of temperatu re and a radiative shock, both moving downward. For a prolonged heatin g with rectangular time profile, a new effect was found. The effect is due to higher efficiency of heat flux from coronal layers to chromosp heric ones: in the heat-wave region, jumps of pressure are from time t o time formed; these jumps result in propagation of velocity perturbat ions up- and downward from the contact discontinuity. In the upper par t of the flow, electron temperature exceeds ion temperature by a facto r of up to 4 by the end of the heating, in spite of the fact that peri odic propagation of weak perturbations from the contact discontinuity slightly reduces this difference. Results of one- and two-temperature approximations are compared. Possible observational manifestations of the process modeled are discussed.