Modulation of Ring Current He-Ions by Bounce-Resonant ULF Waves

Andrew J Gerrard1, Louis J Lanzerotti2, Jerry Wayne Manweiler3, Jacob Bortnik4 and Kevin D Urban1, (1)New Jersey Institute of Technology, Edison, NJ, United States, (2)New Jersey Institute of Technology, Center for Solar-Terrestrial Research, Newark, NJ, United States, (3)Fundamental Technologies, LLC, Lawrence, KS, United States, (4)University of California Los Angeles, Los Angeles, CA, United States
Abstract:
The Radiation Belt Storm Probe Ion Composition Experiment (RBSPICE) instrument on the Van Allan Probes makes unique measurements of, among other ring current species, He-ions in the 65-keV to 520-keV energy range. In this paper we report the spatial and temporal variability of the high L-shell, low energy He-ion phase-space densities (PSD), as measured on both spacecraft during non-storm intervals. We find that the He-ion PSD at these locations and energies change dramatically from orbit to orbit across similar regions of the magnetosphere, and this variability is often related to simultaneously-observed variability in H-ion PSD (also at high L-shell and low energy). We show that the hourly modulation of both species is highly correlated to Pc1 and Pc3 wave activity. Specifically, we conclude that Pc3 frequency bounce-resonant ULF waves are responsible for scattering of He-ions, and thus control the non-storm morphology of ring current He-ions.
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