HR: 0800h
AN: SM31A-0383    [Abstracts]
TI: Categories of Externally Triggered Substorms: Applications to Observable Plasma Sheet Dynamics and Sawtooth Events
AU: * Lyons, L R
EM: larry@atmos.ucla.edu
AF: Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles 405 Hilgard Ave, Los Angeles, CA 90095-1565 United States
AU: Lee, D
EM: dylee@chungbuk.ac.kr
AF: Department of Astronomy and Space Science, Chungbuk National University, 48 Gaeshin-dong, Heungduk-gu, Cheongju, Chungbuk, 361-763 Korea, Republic of
AU: Zou, S
EM: sha@atmos.ucla.edu
AF: Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles 405 Hilgard Ave, Los Angeles, CA 90095-1565 United States
AU: Wand, C
EM: cat@atmos.ucla.edu
AF: Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles 405 Hilgard Ave, Los Angeles, CA 90095-1565 United States
AU: Mende, S B
EM: mende@ssl.berkeley.edu
AF: Space Sciences Laboratory, University of California 7 Gauss Way, Berkeley, CA 94720-7450
AB: Identification of the different types of external substorm triggers and the differing magnetospheric responses to each type reveal fundamental aspects of the physical processes responsible for the substorm expansion phase. Both IMF changes leading to a reduction of magnetospheric convection and solar wind dynamic pressure increases (following prolonged strongly southward IMF) are found to trigger substorms. Important and observable differences in the plasma sheet and auroral response to these two different substorm triggers can be identified. Furthermore, the interplay between effects of IMF and dynamic pressure changes is found to be important, which, for example, can lead to a cancellation of effects and to "null" events. These results indicate that external substorm triggering works by causing an abrupt reduction in the strength of convection in the inner plasma sheet following a growth phase of enhanced convection. This is a fundamental condition that must be accounted for by any substorm model. Sawtooth events are ideal for evaluating the effects of external substorm triggers because they consist of large and clearly identifiable substorm expansions, and it is demonstrated that the large-majority of sawtooth expansions reflect IMF and dynamic pressure substorm triggers, both acting individually and together.
DE: 2407 Auroral ionosphere (2704)
DE: 2704 Auroral phenomena (2407)
DE: 2784 Solar wind/magnetosphere interactions
DE: 2788 Magnetic storms and substorms (7954)
SC: SPA-Magnetospheric Physics [SM]
MN: Fall Meeting 2005