HR: 17:30h
AN: SM14A-07    [Abstracts]
TI: Kinetic Ballooning Mode for Substorm Onset
AU: Gorelenkov, N N
EM: ngorelenkov@pppl.gov
AF: Princeton University, Princeton Plasma Physics Laboratory, Princeton, NJ 08543 United States
AU: * Cheng, C Z
EM: fcheng@pppl.gov
AF: Princeton University, Princeton Plasma Physics Laboratory, Princeton, NJ 08543 United States
AU: Zaharia, S
EM: szaharia@lanl.gov
AF: Los Alamos National Laboratory, MS D466, Los Alamos, NM 87545 United States
AU: Johnson, J R
AF: Princeton University, Princeton Plasma Physics Laboratory, Princeton, NJ 08543 United States
AB: AMPTE/CCE observations showed that the substorm onset in the near-Earth plasma sheet region ($\sim 8-10 R_E$) is associated with a low frequency (in the Pi 2 range) instability that is excited 1-2 minutes before substorm onset. The instability has been explained as kinetic ballooning modes (KBMs) which are excited when $\beta_{eq}$ increases from ~ 20 to above 50. We present theoretical analysis and numerical solutions of KBMs by performing kinetic calculations which include kinetic effects of particle trapping, finite ion gyroradii, and wave-particle resonances. The global magnetosphere prior to substorm onset is modeled realistically by 3D quasi-static equilibrium solutions which consist of a current sheet with an enhanced cross-tail current density with thickness of $\sim 1 R_E$ around the local midnight and with a longitudinal extent of $\sim 60-70^{\circ}$ at $X \sim 7-10 R_E$. The associated ionospheric Birkeland current moves equatorward with an enhanced current density shrinking in latitudinal width, consistent with the observed ionospheric growth phase signatures. The KBM has a real frequency in the Pi2 frequency range. The results of kinetic calculations will be compared with the MHD theory.
DE: 7827 Kinetic and MHD theory
DE: 2740 Magnetospheric configuration and dynamics
DE: 2764 Plasma sheet
DE: 2788 Storms and substorms
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting