Magnetospheric Oscillations and Their Relation to Periodic Multiple Discrete Solar Wind Number Density Variations

Sets of discrete magnetospheric oscillations in the mHz range have been observed in satellite measurements, HF radar measurements, and ground magnetometer data for the last decade. Kepko et al. [2002] and Kepko and Spence [2003] presented case studies showing that, in at least some instances, the apparent frequencies of periodic solar wind number density structures in Earth's reference frame are correlated with observations of magnetospheric oscillations. This strongly suggests that the solar wind is sometimes a driver of multiple discrete magnetospheric oscillations. We recently completed a statistical analysis of 11 years of solar wind data (1995-2005) investigating the occurrence of periodic solar wind number density structures and showed that they occur at preferred frequencies. We defined multiple discrete periodicity events in the solar wind by imposing a criterion that an event contained at least three discrete frequencies, and found stronger evidence for preferred multiple discrete apparent frequencies. In this paper, we extend this analysis to the magnetosphere. We present the results of an analysis of statistically robust magnetospheric peaks in power spectra observed at geosynchronous satellites and ground magnetometers. We compare the occurrence rate of statistically significant spectral peaks in the magnetosphere to our results from the upstream solar wind number density.