Foreshock Significance in Generation of ULF Waves

Thursday, 18 December 2014
Alexandra Angelo1, Olga Gutynska2, David G Sibeck3 and Gerard J Fasel1, (1)Pepperdine University, Malibu, CA, United States, (2)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (3)NASA/GSFC, Greenbelt, MD, United States
Ultra-Low Frequency (ULF) waves in the magnetosphere have been a topic of interest for many years. A variety of different processes (including the Kelvin-Helmholtz Instability, reconnection, and flux transfer events) are thought to input the energy for the ULF waves. We use THEMIS simultaneous observations in the upstream solar wind and in the downstream magnetosphere from October 24, 2007 to June 23, 2014. We use 3 s velocity moments from the THEMIS ESA instrument and 3 s magnetic field magnitude from the THEMIS FGM instrument to perform a Fast Fourier analysis and determine the dominant frequencies of the waves during 10 minutes and 1 hour intervals. The typical periods for solar wind fluctuations are 209 s and typical periods in magnetosphere are 267 s based off of magnetic fluctuation magnitudes. We discuss the foreshock as a trigger in the generation of ULF waves in the magnetosphere. We examine the effects of upstream solar wind parameters on exciting ULF waves pulsations in the magnetosphere.