Isolated nighttime substorms and morning geomagnetic Pc5 pulsations from ground-based and satellite (THEMIS) observations

Abstract

The analysis results of a complex of phenomena that were developing in the evening and morning magnetospheric and ionospheric sectors during two events (January 18 and February 19, 2008) are presented. The analysis is based on the observation data in the magnetotail from the THEMIS satellites and ground-based observations in the morning (MIRACLE network) and nighttime (THEMIS ground-based network) sectors. The events with moderate substorms in the nighttime sector were preceded by strong geomagnetic Pc5 pulsations in the morning sector, the regime of which changed during the development of auroral disturbances. The substorms were accompanied by dipolizations in the magnetotail at distances of ~10 Re and unexpected jump-like fluxes of ∼200-keV electrons. The fluxes appeared within several minutes after a breakup at three central THEMIS satellites simultaneously spaced up to 1.7 Re. According with the ASC data at the NAL observatory (3 frames/min) and with the THEMIS network of ASC data, onset of auroral activations in the night and morning sectors occurred simultaneously. Probable reasons for the sudden suppression or intensification of Pc5 pulsations are discussed.