Frequency - time characteristics of geomagnetic disturbances with periods of 1 - 30 min

Frequency-and-time characteristics of geomagnetic pulsations with 1 - 30 min periods during the substorm that took place July 28 - 29, 1987 are studied on the ground of data obtained at Sabetta station within polar aurorae zone. Integral spectrum covering constantly observed maxima at 15.8 and 3.3 min periods during the disturbance is plotted for the given event within the mentioned range of periods. Possible model concepts about excitation mechanisms of pulsations with the given periods are studied. 16 refs., 4 figs