HR: 09:15h
AN: SM31A-04 [Abstracts]
TI: Sub-Auroral proton precipitation as a Result of Plasmapause-Ring-Current Interaction
AU: * Frey, H U
EM: hfrey@ssl.berkeley.edu
AF: Space Sciences Lab, University of California at Berkeley, 7 Gauss Way, Berkeley, CA 94720 United States
AU: Mende, S B
EM: mende@ssl.berkeley.edu
AF: Space Sciences Lab, University of California at Berkeley, 7 Gauss Way, Berkeley, CA 94720 United States
AU: Immel, T J
EM: immel@ssl.berkeley.edu
AF: Space Sciences Lab, University of California at Berkeley, 7 Gauss Way, Berkeley, CA 94720 United States
AU: Forrester, T
EM: terryf@lpl.arizona.edu
AF: LPL, Univ. Arizona, 1629 E. University Blvd., Tucson, AZ 85721 United States
AU: Spasojevic, M
EM: maria@nova.stanford.edu
AF: STAR Lab., Stanford University, Stanford, CA 94305 United States
AB:
The proton aurora imager SI-12 on the IMAGE spacecraft occasionally observes subauroral proton precipitation in the morning
and the afternoon sectors. Sub-auroral Morning Proton Spots (SAMPS) rotate with 80-90% of the Earth's corotation speed,
while the detached afternoon proton arcs do not move in local time. Coincident particle measurements by DMSP of both
phenomena confirm the source as pure high energy precipitating protons with energy likely above the detector limit of 30 keV. The spots appear after magnetic storms in the recovery phase and last for 1-4 hours in the magnetic local time region of
0600-1200 hours. The subauroral arcs appear after a direction change of the southward or westward components of the
interplanetary magnetic field. IMAGE-EUV observations of the plasmasphere indicate a relationship with density gradients in
the plasmapause. This is supported by nearby geosynchronous observations of increased cold plasma density. We interpret these phenomena as the result of the interaction of ring current protons with electromagnetic ion-cyclotron (EMIC) waves caused by the dense, cold plasmasphere ions. The spots are therefore a consequence of plasmasphere refilling after geomagnetic storms. In contrast, the afternoon arcs are the result of enhanced EMIC waves during moderately disturbed geomagnetic conditions.
DE: 2704 Auroral phenomena (2407)
DE: 2716 Energetic particles, precipitating
DE: 2768 Plasmasphere
DE: 2778 Ring current
SC: SPA-Magnetospheric Physics [SM]
MN: 2005 Joint Assembly