Dayside distribution of Pc5 wave power in the quiet magnetosphere and its response to the solar wind

This paper is a statistical study of Pc5 activity in the quiet magnetosphere based on magnetic field data from the THEMIS mission. During the period under consideration (2007-2009), there were many extended intervals of low geomagnetic activity, defined here as 10≥Dst≥−20 nT. This criterion, along with the availability of solar wind data and THEMIS magnetic field data when the spacecraft were on the dayside between 4 and 9RE provided over 400,000 data points for our plots of dayside Pc5 compressional and transverse wave power. We examined the response of the wave power to the solar wind bulk velocity V, dynamic pressure P, and fluctuations in the dynamic pressure Pvar. The compressional and transverse power enhancements associated with the three parameters were comparable and were observed to a depth within the magnetosphere of about L=5. Power plots based on the combined effects of the dynamic pressure P, which controls the position of the magnetopause, and the bulk velocity V, the mechanism behind the KHI-driven waves on the magnetopause, reflected the solar wind dynamic pressure control of the magnetopause location. A comparison of the Pc5 power response to V and Pvar showed that the greater power enhancement was associated with V in the outer magnetosphere beyond L~6 but with Pvar at distances farther from the magnetopause and closer to Earth.