Abstract

Variations of turbulence properties of the plasma sheet during geomagnetic substorms are investigated using observations of the INTERBALL Tail Probe satellite. The periods are chosen when the satellite was inside the plasma sheet. Fluctuations of the plasma bulk velocity across the plasma sheet are studied for the growth, expansion, and recovery phases of geomagnetic substorms on October 14, 1997; October 30, 1997; and December 16, 1998. It was demonstrated that the level of turbulence increases considerably after the onset of the substorm expansion phase and slowly decreases nearly to the presubstorm level later. The correlation times of plasma fluctuations in the Z-direction are estimated, and diffusion coefficients in the Z-direction are calculated.