HR: 1340h
AN: SM23A-1186    [Abstracts]
TI: Substorm onset by kinetic ballooning instability
AU: * Cheng, C
EM: frankcheng@pssc.ncku.edutw
AF: Plasma and Space Science Center, National Cheng Kung University, Tainan, 70101, Taiwan
AU: Chang, T
EM: tfchang@pssc.ncku.edu.tw
AF: Plasma and Space Science Center, National Cheng Kung University, Tainan, 70101, Taiwan
AU: Zaharia, S
EM: szaharia@lanl.gov
AF: Los Alamos National Laboratory, Los Alamos National Laboratory, Los Alamos, NM 12345, United States
AU: Gorelenkov, N
EM: ngorelenkov@pppl.gov
AF: Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543, United States
AB: The onset of substorms has been observed to associate with ULF (in the Pi 2 frequency range) instabilities in the late growth phase in the magnetosphere. Recent substorm auroral breakup arc observation by ground-based All Sky Imagers and by the FORMOSAT-2 satellite¡¦s ISUAL instrument have also identified azimuthal mode structure of breakup arc with mode number on the order of 200-300. We have developed a Kinetic Ballooning Instability (KBI) theory, which is destabilized by plasma pressure gradient and magnetic field curvature in the high beta region, to explain the substorm observations in both the aurora breakup arc and ULF instabilities in the near- Earth plasma sheet region. The substorm onset model is based on the theoretical analysis and numerical solutions of the gyro-kinetic equations for late growth phase 3D magnetospheric quasi-static equilibria. The results show that the KBI has a real frequency associated with the ion magnetic drift frequency, which is in the Pi2 frequency range, and the most unstable KBI has an azimuthal mode number on the order of 200-300. The theoretical KBI features are consistent with observations in the aurora breakup arc formation and subsequent breakup and the ULF (in the Pi 2 frequency range) instabilities in the near-Earth plasma sheet. Comparison between the KBI model and substorm onset observations will be presented.
DE: 2704 Auroral phenomena (2407)
DE: 2764 Plasma sheet
DE: 2790 Substorms
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting