Afternoon Subauroral Proton Precipitation Resulting from Ring Current - Plasmasphere Interaction

Details Afternoon Subauroral Proton Precipitation Resulting from Ring Current - Plasmasphere Interaction Afternoon Subauroral Proton Precipitation Resulting from Ring Current - Plasmasphere Interaction

Dec 2004

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004agufmsm11b..02s&link_type=abstract

American Geophysical Union, Fall Meeting 2004, abstract #SM11B-02

Physics

2716 Energetic Particles, Precipitating, 2768 Plasmasphere, 2772 Plasma Waves And Instabilities, 2778 Ring Current

Scientific paper

Although the dominant loss processes for ring current ions are collisional, wave-particle interactions are also believed to play an important role as they provide a mechanism for the rapid decay of the ring current during the early recovery phase of geomagnetic storms. Considerable attention has been given to regions of spatial overlap between energetic, anisotropic ring current ions and cold, dense plasmaspheric material that should be particularly conducive to the growth of electromagnetic ion cyclotron (EMIC) waves. Resonant interaction between ring current ions and EMIC waves results in pitch angle scattering and subsequent precipitation of the energetic ions into the upper atmosphere. Global imaging of the proton aurora by the Far Ultraviolet (FUV) Spectrographic Imager (SI) on-board the IMAGE satellite has led to the identification of arcs of precipitating protons at latitudes equatorward of and separated from the main proton auroral oval in the afternoon local time sector. We investigate the occurrence of these arcs and their relationship with the plasmasphere and electromagnetic ion cyclotron waves. In a four month study interval including sixteen events, we find that the detached proton arcs are more likely to occur during geomagnetically disturbed periods and specifically at times when enhanced energetic ion densities and temperature anisotropies are observed in the equatorial magnetosphere. The disturbance-time arcs tend to be located at lower magnetic latitudes and are consistently associated with plasmaspheric plumes as observed by the IMAGE Extreme Ultraviolet (EUV) instrument. Wave data from the POLAR Magnetic Field Experiment (MFE) available for two of the detached arc events indicate the presence of strong EMIC waves near the equator in the vicinity of the proton precipitation region.

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