HR: 0800h
AN: SM41C-1201    [Abstracts]
TI: Strong Pitch-Angle Diffusion of the Ring Current Ions Induced by Electromagnetic ion Cyclotron Waves
AU: * Gamayunov, K V
EM: konstantin.gamayunov@msfc.nasa.gov
AF: NASA Marshall Space Flight Center, National Space Science and Technology Center, Mail Code XD12, 320 Sparkman Drive, Huntsville, AL 35805 United States
AU: Khazanov, G V
EM: george.khazanov.msfc.nasa.gov
AF: NASA Marshall Space Flight Center, National Space Science and Technology Center, Mail Code XD12, 320 Sparkman Drive, Huntsville, AL 35805 United States
AB: Deep and intense circulation of the magnetospheric plasma during geomagnetic storm is building up an energy content of the terrestrial ring current (RC) to an unusually high level, and the RC intensity strongly influence the storm-time space weather. The recovery of Dst index takes place hours or days after Dst minimum, and is caused by the decay of magnetopause and magnetotail current systems, and removal of the RC ions due to charge exchange, convection through the dayside magnetopause, Coulomb scattering, RC interaction with electromagnetic ion cyclotron (EMIC) waves, and scattering by field-line curvature. During the early recovery phase, the RC loss rate is about one hour or less, and it is more rapid than charge exchange can support. Ion scattering into the loss cone by EMIC waves is believed to be responsible for such fast RC decay during this storm stage. However, most RC-EMIC wave interaction models do not predict the strong pitch-angle diffusion that is theoretically discussed and observed in the Earth magnetosphere (particularly by SEPS detectors on board of the POLAR satellite). In present work, we employ our self-consistent RC-EMIC wave model in order to study systematically the occurrence of the RC strong pitch-angle diffusion caused by interaction with waves during the May 1998 storm. Most of cases of the strong diffusion and of the intense EMIC waves are located in the afternoon-premidnight MLT sector at 3 < L < 6, and exhibit significant linear correlation. During the early recovery phase (at about 08 UT on May 4), the entire RC energy range (less than 450 keV) is subject to strong pitch-angle diffusion. Although the flux transitions between trapped zone and loss cone are steeper for higher energy RC protons than for main body of the distribution function, the pitch-angle distributions are highly isotropic for all energies both inside and outside of the loss cone.
DE: 2716 Energetic particles: precipitating
DE: 2753 Numerical modeling
DE: 2778 Ring current
DE: 7867 Wave/particle interactions (2483, 6984)
SC: SPA-Magnetospheric Physics [SM]
MN: Fall Meeting 2005