Storm-time Ion Acceleration in Kinetic Scale Alfvénic Fluctuations: Van Allen Probes/THEMIS Observations and Modelling.

Christopher Carew Chaston, University of California Berkeley, Space Sciences Laboratory, Berkeley, CA, United States; University of Sydney, School of Physics, Sydney, Australia, John W Bonnell, University of California Berkeley, Berkeley, CA, United States, John R Wygant, University of Minnesota Twin Cities, Minneapolis, MN, United States, Craig Kletzing, University of Iowa, Physics and Astronomy, Iowa City, United States, George B Hospodarsky, University of Iowa, Physics and Astronomy, Iowa City, IA, United States, William S Kurth, University of Iowa, Iowa City, IA, United States, Charles William Smith, University of New Hampshire Main Campus, Space Science Center, Durham, NH, United States, Elizabeth MacDonald, NASA Goddard Space Flight Center, Greenbelt, MD, United States, Louis J Lanzerotti, New Jersey Institute of Technology, Center for Solar-Terrestrial Research, Newark, NJ, United States, Jerry Wayne Manweiler, Fundamental Technologies, LLC, Lawrence, KS, United States and Donald G Mitchell, JHU/APL, Laurel, MD, United States
Abstract:
Models describing energetic ion dynamics in the inner magnetosphere often significantly under-estimate the enhancement in ion energy density during geomagnetic storms. In this presentation we suggest that this may be a consequence of the action of kinetic scale ultra-low frequency electromagnetic field variations or kinetic Alfven waves and eigenmodes. We show how these waves originate in the plasma sheet and subsequently fill a large fraction of the inner magnetosphere during storm times. The amplitude of the eigenmodes can exceed 100 mV/m. These fluctuations have the capacity to break the traditional invariants constraining ion motion to drive very rapid energisation and heating of the ion plasma. We show how these waves can lead to large increases in particle pressure due to the extraction and continuous acceleration of oxygen ions from the ionosphere and injected ions from the plasma sheet. These waves present a new mechanism for enhancing the ring current that both observations and simulations indicate should be active during storm times.
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