[en] The problem of plasma expansion in vacuum is quantatively solved. Considered is the process of the flow transition to the automodel regime and a detailed comparison of the obtained solution with the automodel one is carried out. It is seen from the given results that the automodel solution gives a right asymptotic description of the flow, caused by density discontinuity. The automodel solution is not acceptable at the initial stage of discontinuity decomposition and in the vicinity of the ion front. The automodel solution does not also describe oscillations of the electric field in the frequencies of the order of electron plasma, which appear in taking into account the final electron mass. Studied is ion acceleration, as well as the effect of electron temperature on it and on the whole process