HR: 0800h
AN: SM31D-0660    [Abstracts]
TI: Ballooning stability of near-Earth plasma sheet in presence of magnetospheric convection*
AU: * Zhu, P
EM: pzhu@wisc.edu
AF: University of Wisconsin-Madison, 1500 Engineering Drive, Madison, WI 53706, United States
AU: Raeder, J
EM: J.Raeder@unh.edu
AF: University of New Hampshire, 39 College Road, Durham, NH 03824, United States
AU: Bhattacharjee, A
EM: amitava.bhattacharjee@unh.edu
AF: University of New Hampshire, 39 College Road, Durham, NH 03824, United States
AU: Hegna, C C
EM: hegna@cae.wisc.edu
AF: University of Wisconsin-Madison, 1500 Engineering Drive, Madison, WI 53706, United States
AB: Most investigations of ballooning instabilities in the near-Earth magnetotail have been carried out under the assumption of a magnetostatic magnetosphere. In reality, the magnetosphere exhibits persistent convection in the tail region, which is often turbulent, as evidenced by the presence of bursty bulk flows in both observations and simulations. The convection across magnetic flux surfaces has the effect of limiting the ballooning growth by reducing the interaction time as the perturbation passes through the destabilizing region. Crudely, this yields a window in the pressure gradient required for ballooning instability. In this work, we analyze the ballooning properties of the near-Earth plasma sheet in the presence of magnetospheric convection. The configurations of the near-Earth magnetotail are obtained from global MHD simulations using the OpenGGCM code, using idealized, as well as observed solar wind conditions as input. An approximate local dispersion relation for ballooning instability in the presence of flow is evaluated for the tail region when the configuration attains quasi steady-state conditions. Under simple, idealized solar wind conditions with steady southward IMF, the near-Earth tail region is analyzed and the stability boundaries are determined. Using solar wind data from recent observed substorm events, we developed a sequence of global magnetospheric configurations by means of OpenGGCM simulations, and the role of the ballooning instability in these events is delineated. *Research supported by NSF Grant No. ATM-0542954.
DE: 2752 MHD waves and instabilities (2149, 6050, 7836)
DE: 2753 Numerical modeling
DE: 2764 Plasma sheet
DE: 2790 Substorms
DE: 7839 Nonlinear phenomena (4400, 6944)
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting