HR: 08:20h
AN: SH51D-02    [Abstracts]
TI: Role of Collisionless Reconnection in the Sudden Onset of Flares and Substorms: a Comparative Study
AU: * Bhattacharjee, A
EM: amitava.bhattacharjee@unh.edu
AF: Space Science Center, University of New Hampshire, Durham, NH 03824, United States
AU: Yang, H
EM: hongang.yang@unh.edu
AF: Space Science Center, University of New Hampshire, Durham, NH 03824, United States
AB: Magnetic reconnection is widely believed to play an important role in magnetospheric substorms and solar flares. However, observations impose powerful constraints on theories of reconnection. Since the plasmas in the corona and the magnetosphere are characterized by very high values of the Lundquist number, it is likely that the relevant regime of reconnection is collisionless, and described by a generalized Ohm's law. Observations of substorms and flares demonstrate that they are generically not quasi-steady but impulsive phenomena, characterized not only by rapid growth, but a sudden change in the time-derivative of the reconnection rate, which places an additional burden on theory. We will present strong theoretical evidence that such fast and impulsive signatures can be obtained for both flares and substorms within the framework of two-fluid or Hall MHD theory, subject to the caveat that there are unresolved questions on how the present theoretical results on fast reconnection scale to large systems. Results of analytic theory and simulations will be presented for various system sizes, and comparisons will be made with in situ satellite measurements and RHESSI/SOHO/TRACE observations. The role of secondary instabilities of thin current sheets such as ballooning (for substorms) and tearing (for flares) will be discussed.
DE: 2788 Magnetic storms and substorms (7954)
DE: 7519 Flares
DE: 7526 Magnetic reconnection (2723, 7835)
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2007 Joint Assembly