On polarization of hard x radiation of solar flares

Hard X radiation was studied using polarimeters installed on the ''Interkosmos'' satellites. Experiments were made in 1969-1974. Experimental data of the ''Interkosmos'' and ''OSO-7'' satellites are compared with the value of polarization, calculated in different models of nonthermal X radiation sources. It is shown that the measured value of polarization and the long time of its existance are not in contradiction with the flare model, in electron acceleration occur on current layer ruptures in the form of consistent ''elementaryflare bursts''. Plasma heating by accelerated electrons may be realized in a fast regime, wich limits the maximum temperature. In result, bremsstrahlung polarized of electrons may prevail over thermal radiation of plasma heated by them