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Measurements of three X-ray flares in October/November 1970 abord the Intercosmos 4 satellite confirm the existence of polarization in the initial phase of the X-ray bursts. The polarization can be observed for a few up to ten minutes, and an increase in polarization is observed during secondary maxima of the bursts as well.

Analysis of the X-ray polarization data at ,1. ~ 0.8 A for three major chromospheric flares shows that during the 'hard' phase of the flare the X-rays are polarized in the plane, the projection of which on the solar disc is going approximately from the flare region to the center of the disc. Simultaneously performed measurements of the spectral energy distribution have proved that observed X-rays are produced by the bremsstrahlung of the accelerated electrons with the energies in the range 10-100 keV, The experimental data are in good agreement with the flare model, which deals with the radial movement of accelerated electrons towards the photosphere, together with the continuous injection of these electrons into the emitting region.

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