Differences in the Dynamics of the Asymmetrical Part of the Magnetic Disturbance during the Periods of Magnetic Storms Induced by Different Interplanetary Sources

Abstract

The differences in the dynamics of the asymmetrical part of the geomagnetic disturbance at middle and low latitudes during magnetic storms initiated by different interplanetary sources are analyzed. The analysis is performed with the SYM-H, ASY-H, and Dst indices from the OMNI database during the periods of 58 intense magnetic storms with –270 ≤ Dstmin ≤ –90 nT that were recorded in 1995–2017 and initiated by one of the solar wind structures: compressed corotating interaction regions (CIRs); interplanetary coronal mass ejections (ICMEs) including magnetic clouds (MCs) and Ejecta “pistons”; and compressed Sheath regions in front of ICMEs. The interplanetary sources were identified on the basis of the catalog of large-scale solar-wind phenomena ( ftp://ftp.iki.rssi.ru/pub/omni/ ). A double superposed epoch analysis with reference points at the onset of the storm and during Dstmin was used. It is shown that the ASY-H values during Sheath-driven storms are, on average, 40% higher than for storms of other groups and that the ASY-H maximum occurs ~3 h earlier than Dstmin during Sheath-driven storms and 1–2 h earlier during MC-driven storms, which may indicate a more intense and uneven energy inflow during these periods. It is assumed that this energy inflow may be provided by the proton flux with energies of >10 MeV observed by the GOES geostationary satellites, which increases by more than two orders of magnitude in the intervals of Sheath-driven storms as compared to storms of other groups.