Ring Current He-Ion Control by Bounce Resonant ULF Waves

TitleRing Current He-Ion Control by Bounce Resonant ULF Waves
Publication TypeJournal Article
Year of Publication2017
AuthorsKim, H, Gerrard, AJ, Lanzerotti, LJ, Soto-Chavez, R, Cohen, RJ, Manweiler, JW
JournalJournal of Geophysical Research: Space Physics
Date Published09/2017
Keywordsbounce resonance; Helium ion; ring current; ULF waves; Van Allen Probes
AbstractRing current energy He-ion (∼65 keV to ∼520 keV) differential flux data from the Radiation Belt Storm Probe Ion Composition Experiment (RBSPICE) instrument aboard the Van Allan Probes spacecraft show considerable variability during quiet solar wind and geomagnetic time periods. Such variability is apparent from orbit to orbit (∼9 hours) of the spacecraft and is observed to be ∼50–100% of the nominal flux. Using data from the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) instrument, also aboard the Van Allen Probes spacecraft, we identify that a dominant source of this variability is from ULF waveforms with periods of 10's of sec. These periods correspond to the bounce resonant timescales of the ring current He-ions being measured by RBSPICE. A statistical survey using the particle and field data for one full spacecraft precession period (approximately two years) shows that the wave and He-ion flux variations are generally anti-correlated, suggesting the bounce resonant pitch-angle scattering process as a major component in the scattering of He-ions.
Short TitleJ. Geophys. Res. Space Physics

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