HR: 17:45h
AN: SM14A-07    [Abstracts]
TI: Fundamental Aspects of External Triggers and Non-Triggers of Substorm Particle Injections, and Implications on Sawtooth Events and Repetitive Substorms
AU: * Lee, D
EM: dylee@chungbuk.ac.kr
AF: Chungbuk National University, Dept of Astronomy and Space Science, Cheongju, 361-763 Korea, Republic of
AU: Lyons, L
EM: larry@atmos.ucla.edu
AF: UCLA, Dept of Atmospheric and Oceanic Sciences, Los Angeles, CA 90095-1565 United States
AU: Reeves, G
EM: reeves@lanl.gov
AF: LANL, Space Science and Applications, Los Alamos, NM 37545 United States
AB: It is important to understand what specific types of solar wind disturbances lead to a substorm and what other specific types do not. The types of solar wind disturbances include a variation in either IMF or dynamic pressure or a combination of simultaneous variations in both. We used observations of geosynchronous particle fluxes at energies of tens to hundreds of keV and found the following features. (1) A northward turning of the IMF is found to trigger the typical substorm injection as well known already. The injection front is wider when it is triggered by a northward turning under a strongly southward IMF condition. (2) The effect by the northward turning can however be cancelled out by a simultaneous increase of the IMF By magnitude and/or a simultaneous decrease of the dynamic pressure, leading to no substorm. (3) Generally a pressure increase leads to a compression effect which appears as flux increase or decrease or even no change, depending on the radial profile of the particle distribution at constant adiabatic invariants. This compression effect can be different between different MLTs and different particle species. (4) However, a pressure increase under strongly southward IMF conditions leads to not only the typical compression effect but also a nightside substorm injection, i.e., a two-mode response. (5) This pressure-induced substorm injection can however be cancelled out by a simultaneous (further) decrease of the already-southward IMF and/or by a simultaneous increase of the IMF By magnitude. (6) In addition, the effects by a simultaneous increase of both IMF Bz and dynamic pressure add up to lead to a substorm injection accompanied by the typical compression effect, while no substorm injection is expected by a pressure decrease or a decrease of the IMF Bz or a simultaneous decrease of both. We suggest that a substorm injection is triggered only by a variation or a combination of variations that results in a convection reduction within the inner plasma sheet. The features found above serve as fundamental bases for a reliable interpretation on the origin of each tooth during sawtooth injections, which usually occur during a strongly southward IMF condition. In addition, we find that the repetitive injections that occur during the high-speed stream periods are caused by the successive northward turnings of the IMF preceded by weak to moderate southward periods. We will discuss differences between the sawtooth injections and the repetitive injections during the high-speed streams.
DE: 2720 Energetic particles: trapped
DE: 2730 Magnetosphere: inner
DE: 2760 Plasma convection (2463)
DE: 2784 Solar wind/magnetosphere interactions
DE: 2790 Substorms
SC: SPA-Magnetospheric Physics [SM]
MN: Fall Meeting 2005