HR: 1330h
AN: SM23B-07    [Abstracts]
TI: A Mechanism for the Loading-Unloading Substorm Cycle Missing in MHD Global Magnetospheric Simulation Models
AU: * Klimas, A
EM: alex.klimas@nasa.gov
AF: NASA Goddard Space Flight Center, Code 612.2, Greenbelt, MD 20771 United States
AU: Uritsky, V
EM: uritsky@geo.phys.spbu.ru
AF: St. Petersburg State University, Stary Petergoff 198904, St. Petersburg, Russian Federation
AU: Vassiliadis, D
EM: vassi@electra.gsfc.nasa.gov
AF: ST, NASA Goddard Space Flight Center, Code 612.2, Greenbelt, MD 20771 United States
AU: Baker, D N
EM: baker@lynx.colorado.edu
AF: Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80309 United States
AB: Loading and consequent unloading of magnetic flux is an essential element of the substorm cycle in Earth's magnetotail. We are unaware of an available global MHD magnetospheric simulation model that includes a loading-unloading cycle in its behavior. Given the central role that MHD models presently play in the development of our understanding of magnetospheric dynamics, and given the present plans for the central role that these models will play in ongoing space weather prediction programs, it is clear that this failure must be corrected. A 2-dimensional numerical driven current-sheet model has been developed that incorporates an idealized current-driven instability with a resistive MHD system. Under steady loading, the model exhibits a global loading-unloading cycle. The specific mechanism for producing the loading-unloading cycle will be discussed. It will be shown that scale-free avalanching of electromagnetic energy through the model, from loading to unloading, is carried by repetitive bursts of localized reconnection. Each burst leads, somewhat later, to a field configuration that is capable of exciting a reconnection burst again. This process repeats itself in an intermittent manner while the total field energy in the system falls. At the end of an unloading interval the total field energy is reduced to well below that necessary to initiate the next unloading event and, thus, a loading-unloading cycle results. It will be shown that, in this model, it is the topology of bursty localized reconnection that is responsible for the appearance of the loading-unloading cycle.
DE: 2740 Magnetospheric configuration and dynamics
DE: 2753 Numerical modeling
DE: 2764 Plasma sheet
DE: 2788 Storms and substorms
DE: 3220 Nonlinear dynamics
SC: SPA-Magnetospheric Physics [SM]
MN: 2005 Joint Assembly