We present an analysis of the occurrence distributions of statistically significant apparent frequencies of periodic solar wind number density structures and dayside magnetospheric oscillations in the f = 0.5–5.0 mHz range. Using 11 years (1995–2005) of solar wind data, we identified all spectral peaks that passed both an amplitude test and a harmonic F test at the 95% confidence level in 6-hour data segments. We find that certain discrete frequencies, specifically f = 0.7, 1.4, 2.0, and 4.8 mHz, occur more often than do other frequencies over those 11 years. We repeat the analysis on discrete oscillations observed in 10 years (1996–2005) of dayside magnetospheric data. We find that certain frequencies, specifically f = 1.0, 1.5, 1.9, 2.8, 3.3, and 4.4 mHz, occur more often than do other frequencies over those 10 years. Many of the enhancements found in the magnetospheric occurrence distributions are similar to those found in the solar wind. Lastly, we counted the number of times the same discrete frequencies were identified as statistically significant using our two spectral tests on corresponding solar wind and magnetospheric 6-hour time series. We find that in 54% of the solar wind data segments in which we identified a spectral peak, at least one of the same discrete frequencies was statistically significant in the corresponding magnetospheric data segment. Our results argue for the existence of inherent apparent frequencies in the solar wind number density that directly drive global magnetospheric oscillations at the same discrete frequencies, although the magnetosphere also oscillates through other physical mechanisms.
Journal of Geophysical Research
American Geophysical Union
Digital Object Identifier (DOI)
Viall, N. M., L. Kepko, and H. E. Spence (2009), Relative occurrence rates and connection of discrete frequency oscillations in the solar wind density and dayside magnetosphere, J. Geophys. Res.,114, A01201, doi:10.1029/2008JA013334.
Copyright 2009 by the American Geophysical Union.