Geomagnetic (MIE) and storm sudden commencement (SSC) impulses in a high-latitude magnetosphere

Abstract

Amplitude regularities, intermittence statistics, and conditions of generation of magnetic (mag- netic impulse event, MIE) and geomagnetic storm sudden commencement (SSC) impulses were compara- tively analyzed. Common and different properties of MIE and SSC impulses observed in a high-latitude mag- netosphere were detected. It was shown that MIE impulses are observed against a background of relatively stable interplanetary medium parameters and mostly when the IMF sector structure is negative. SSC impulses are observed against a background of sharply increasing solar wind and IMF parameters and when the IMF sector structure is positive. The amplitude dynamics, depending on the geomagnetic latitude of MIE and SSC impulses relative to the noon meridian, as well as in the daytime and nighttime MLT sectors, is sim- ilar. The dynamics of the intermittence indices (α), depending on the geomagnetic latitude of MIE and SSC impulses in the same MLT sectors, is antiphase. Independently of the IMF sector structure, the amplitudes of MIE and SSC impulses increase with increasing geomagnetic latitude, and the intermittence indices change in antiphase. It is assumed that the degree of plasma turbulence at the front boundary of magneto- sphere at moderate geomagnetic activity is relatively high and sufficient for the generation of MIE impulsive regimes. At the same time, SSC impulses originate at a lower turbulence level in the subsolar magnetospheric region but under the external action of solar wind inhomogeneities on the magnetosphere.