HR: 0800h
AN: SM31A-1214    [Abstracts]
TI: Meso-Scale Dynamics of the Near-Earth Plasma Sheet During Breakups
AU: * Voronkov, I O
EM: igor@phys.ucalgary.ca
AF: Voronkov Igor, Department of Physics and Astronomy, University of Calgary, Calgary, AB T2N 1N4 Canada
AU: Donovan, E F
EM: donovan@phys.ucalgary.ca
AF: Voronkov Igor, Department of Physics and Astronomy, University of Calgary, Calgary, AB T2N 1N4 Canada
AB: This study is focused on the separation of signatures of the local inner edge pseudo-breakup, breakup at full onset, and bursty flows. Sample events are presented in support of the following. A pre-breakup equator-most arc appears and intensifies at the growth phase in association with the stretching of the near-Earth magnetotail. The latter appears to be the main energy reservoir for the breakup. Sufficient stretching of the inner PS is compulsory for the arc intensification but may be not sufficient for a breakup. In some cases, the equatorial plasma sheet and arc represent a marginally stable system. Once the energy is stored in the inner plasma sheet and arc system, breakup can be triggered by various mechanisms. This can be an internal instability starting with no evident external influence (e.g., nonlinear ballooning instability). The instability of the inner PS can also start in association with the solar wind magnetic field changes (as the northward turning causing the changes of convection in the magnetosphere) or as a result of the earthward traveling perturbations of the more distant magnetotail. Externally and internally triggered breakups manifest the same signatures (onset of Pi2s, dipolarization in the near-Earth PS, vortex and electrojet expansion, etc.) When the entire PS becomes very thin, the near-Earth breakup region interacts with the NENL region. Interaction can be initiated by both the mid-tail (NENL) and near-Earth breakup activations. These two processes can also be seen virtually at the same time, suggesting that stretching of the entire magnetotail gives a start to both activations. In that sense, the question ``how does the substorm start?" may not be well posed: full onset is an interaction of the near-Earth breakup region and more distant (NENL) tail disruption in which both processes play an essential role.
DE: 2700 MAGNETOSPHERIC PHYSICS
DE: 2704 Auroral phenomena (2407)
DE: 2740 Magnetospheric configuration and dynamics
DE: 2744 Magnetotail
DE: 2764 Plasma sheet
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting