Patterns of simultaneous observations of high-latitude magnetic impulses (MIEs) and impulsive bursts in the Pc1–2 band

Abstract

The analysis of simultaneous observations of 128 cases of high-latitude magnetic impulse events (MIEs), as well as geomagnetic pulsations in the Pc1–2 band observed in the area of the dayside cusp, was carried out. We investigated magnetograms from the Mirny Observatory, Antarctica. As a result of the examination, three groups of impulses were identified: (1) impulses accompanied by impulsive bursts of intervals of pulsations with rising periods (IPRPs)-type geomagnetic pulsations—16% of all events, (2) impulses accompanied by impulsive bursts of the Pi1B type (bursts of irregular magnetic pulsations)—48% of all events, and (3) impulses which were not accompanied by geomagnetic pulsations within a high-frequency band—36% of all events. It was found that the maximum frequency of occurrence of the impulses accompanied by impulsive bursts of the IPRP and Pi1B types was observed between 1200 and 1300 MLT. The events of the first two groups were observed predominantly when Bz>0. It was shown that the filling frequency of impulsive bursts that accompany the occurrence of impulses depends on the amplitude of the bursts. The maximum frequency of the occurrence of impulses which were not accompanied by impulsive bursts is between 1000 and 1100 MLT. The events of the third group were observed predominantly when Bz<0. In most cases, the occurrence of impulsive bursts coincided with the leading edge of the MIE. It is supposed that the MIE generation is stimulated by intensification of the plasma turbulence level at the dayside magnetopause in consequence of modulation instability development or reconnection processes.