Dynamics of Interplanetary Parameters and Geomagnetic Indices during Magnetic Storms Induced by Different Types of Solar Wind

Аннотация

Based on the OMNI2 archival data for 1995–2017, the dynamics of geomagnetic activity indices (Dst, ap, AE, and PC) and interplanetary parameters over the periods of magnetic storms with a minimum of Dst_min ≤ –50 nT induced by different interplanetary sources is analyzed: CIR regions of the interaction of solar wind (SW) streams with different speeds; Sheath-compression regions before interplanetary CMEs (ICMEs); magnetic clouds (MCs) and Ejectas. 181 storms with a monotonic course of the Dst index during the main phases were selected. Similarly to earlier works (Yermolaev et al., 2010a, 2011), which analyzed the OMNI data for 1976–2000, double superposed epoch analysis method with two reference times was used: at the beginning of the main phase and at the minimum Dst_min. This approach allows one to reveal trends in the dynamics of the magnetic activity indices and the SW parameters during storms with different durations of main phases, as well as the difference between these trends for the storms generated by different sources. It is shown that the largest average Dst, aр, AE, and PC indices take place during Sheath storms, and the smallest are registered during the Ejecta storms. The dynamics of the AE and ap indices is similar, and the polar cap index PC dynamics considerably varies during storms with different interplanetary sources, which is evidence of differences between the responses of the polar magnetosphere during storms generated by different sources. There are significant differences between the variations of SW parameters of different storm groups: a very high level of fluctuations of the B and Bz of the IMF is characteristic of the Sheath storms, while, it is close to average for the CIR storms and is considerably lower than average for MCs and Ejecta.