ULF wave activity in high‐speed streams of the solar wind: Impact on the magnetosphere

Abstract

AbstractIn recent years, the study of solar‐magnetospheric interaction has increasingly been focusing on wave phenomena and the role of turbulence in the processes of energy and momentum transfer from the Sun to the Earth's magnetosphere. Here we consider one aspect of the problem — the impact of wave patterns associated with high‐speed solar wind streams (HSSs) on the variable geomagnetic field and the trapped radiation. The superposed epoch method was chosen as our research technique. We use observations of the solar wind plasma and the interplanetary magnetic field at libration point L1, as well as measurements of electron fluxes at geostationary orbit and of geomagnetic pulsations on ground. Data from 31 corotating interaction regions (CIR), their sources being coronal holes on the Sun, and 13 streams from coronal mass ejections (CME) were processed. The focus is on the regime of ultra‐low frequency (ULF) waves in high‐speed flows and ULF fluctuations in the magnetosphere. A significant difference has been revealed between the wave activity characteristics of the two HSS types in the solar wind and on the earth. Irregular pulses are typical for coronal mass ejections and wave‐like conditions are common for CIRs. For the latter, the temporal profile of the normalized ULF amplitude in the solar wind is similar to the pulsation amplitude profile on the ground. We also found that a high level of ULF activity in the magnetosphere during CIR intervals is favorable to 2 MeV electron flux enhancement, but does not affect the flux of less energetic electrons.