ИСТИНА

We briefly discuss the pioneer works by Grinin and Sobolev concerning the relation between the optical continuum of the flare emission and the accelerated particles flux. Subsequently, consideration of this idea required the modelling of the gasdynamical response of the chromosphere to the impulsive heating. In this work we present the calculation of the emission spectrum of the hydrogenic plasma of this condensation. It is shown that within such a model one can explain the line emission of hydrogen and the continuous recombination emission. In the visible region this continuum appears to be weak: the emission contrasts do not exceed 5-7% even in the case of the most powerful heating flux. But the contrast can reach as much as 15-20% in some cases. In order to explain so large values, one has to introduce the additional heating of the upper photosphere, the nature of which is unclear. We shortly discuss Solar observations of "black light flares", which were predicted by Grinin and Sobolev.