Global profiles of compressional ultralow frequency wave power at geosynchronous orbit and their response to the solar wind

Abstract

We investigate the global local‐time profiles of compressional wave power in three ultralow frequency (ULF) bands corresponding to Pc3, Pc4, and Pc5 pulsations using magnetic field data from the geosynchronous GOES satellites. The global power profiles of the three frequency bands are studied for low, moderate, and high levels of geomagnetic activity based on the Dst index. We also consider the seasonal variation of the ULF power profiles, as well as the effects of solar wind and interplanetary magnetic field (IMF) parameters. For high geomagnetic activity, we find that the greatest power is associated with compressional Pc5 pulsations in the afternoon sector; for low geomagnetic activity, ULF power levels are consistently highest in the tail region. A summer power minimum in all three frequency bands is observed in our study of seasonal variation, while higher power levels occur around local midnight throughout the year. The enhancement of ULF power by high solar wind velocity and pressure is greater for the lower‐frequency waves. Furthermore, solar wind plasma parameters have a significantly greater influence on ULF wave power than IMF parameters like cone angle and northward/southward orientation.