The response of the polar cusp to a high-speed solar wind stream studied by a multispacecraft wavelet analysis

We investigate the coupling between the solar wind and the magnetospheric cusp during the passage of a Corotating Interaction Region (CIR) high-speed stream. A CIR event on 11 January 2002 is selected for this study. We use ACE (Advanced Composition Explorer) and Geotail plasma and magnetic field data for interplanetary solar wind observations and Cluster plasma and magnetic field data for the cusp observations. The response of the solar wind on the polar cusp was studied and made visible with the wavelet and cross-wavelet analysis. During the CIR event we observe significantly enhanced wave power for waves with periods ranging from 15 to 25 min (1.1–0.7 mHz). Significant cross-correlation power of the ACE and Geotail interplanetary magnetic field (IMF) Bz- and Ey-component and the solar wind Vx-component versus the Cluster cusp H+ density, the thermal temperature and energetic electron flux (50–244 keV) were found at the corresponding frequencies. We conclude that the solar wind Alfvén waves affect the magnetospheric dayside cusp density and heat the cusp. We interpret these correlation results as evidence of high-speed solar wind—magnetosphere coupling driven by waves in the solar wind.