geomagnetic pulsation groups (observed during magnetospheric substorms and when these substorms are
absent) and the pulsation generation geophysical conditions have been experimentally studied based on obser-
vations at the Borok midlatitude observatory. It has been indicated that the dynamics of the occurrence fre-
quency of Pi2 substorm and nonsubstorm bursts and their amplitude, duration, and intervals between peaks
depending on the local time and season is identical in many respects. It has been found that substorm Pi2 bursts
are mostly observed when the IMF is sunward and the solar wind electric field (Ey) is positive, whereas non-
substorm bursts are observed when the IMF is antisunward and Ey is negative. The fundamental differences in
the diurnal and seasonal variations in index
, which characterizes the slope of the distribution function of the two-group Pi2 burst amplitudes, have been revealed. It has been found that the index
value substantially depends on Ey and the IMF longitude (
). It has been assumed that the plasma sheet turbulence of the metasta-ble magnetotail is responsible for reconnection and the generation of substorm and nonsubstorm Pi2 pulsation
bursts.