Response of the magnetospheric ULF activity and relativistic electrons to high speed streams of the solar wind

Abstract:

The impact of wave patterns associated with high-speed solar wind streams on the variable geomagnetic field and the trapped radiation is studied. A superposed epoch analysis of the ULF oscillations associated with two main types of the solar wind high speed streams has been performed. Data from magnetic and plasma measurements onboard ACE spacecraft along with on-ground magnetic data were used for the analysis. The zero epoch of each event was set to the time of ACE observation of the current sheet coinciding with the stream front. The results demonstrate that CIR events produce a more intense and more continuous ULF activity both in the solar wind and in the magnetosphere. Data from GOES measurements of energetic electrons at geostationary orbit were also included in our superposed epoch study. Higher effectiveness of CIR events in enhancement of electron population in outer radiation belt is confirmed. A new feature is that higher amplitude of ULF on-ground oscillations gives more intense flux of 2 MeV electrons but it does not influence flux of less energetic electrons (600 keV).