HR: 09:15h
AN: NG21A-06 INVITED     [Abstracts]
TI: Susceptibility Divergence at the Mean-Field SOC Limit in a 2-D Driven Current-Sheet Model
AU: * Klimas, A
EM: alex.klimas@nasa.gov
AF: A J Klimas, NASA Goddard Space Flight Center, Greenbelt, MD 20771 United States
AU: Uritsky, V
EM: uritsky@geo.phys.spbu.ru
AF: V Uritsky, St. Petersburg State University, St. Petersburg, 198904 Russian Federation
AU: Vassiliadis, D
EM: vassi@electra.gsfc.nasa.gov
AF: D Vassiliadis, USRA at NASA Goddard Space Flight Center, Greenbelt, MD 20771 United States
AU: Baker, D N
EM: baker@lynx.colorado.edu
AF: D N Baker, LASP, University of Colorado, Boulder, CO 80309 United States
AB: Uritsky et al. [JGR, 2002; GRL, 2003] have shown that the evolution of bright night-side auroral emission regions shares several important properties with that of avalanches in numerical models of self-organized criticality (SOC). Klimas et al. [JGR, 2000] have suggested that this result is a reflection of the statistical behavior of reconnection in the magnetotail plasma sheet. They hypothesize that the spatiotemporal distribution of reconnection events in the plasma sheet is a reflection of an avalanching process in that region that is scale-free over a broad range of scales. The nature of this hypothetical avalanching process is presently under investigation. Klimas et al. [JGR, 2004] are considering a 2-D driven current-sheet model that exhibits scale-free avalanche distributions associated with bursty, intermittent reconnection and field annihilation in the modeled current sheet. The indices that define these power-law avalanche distributions and the range of scales contained in the distributions are quite similar to those of the auroral emission regions. For a broad class of sandpile-like models, Vespignani and Zapperi [Phys. Rev. E, 1998] have constructed a mean-field theory of SOC that describes the divergence of the susceptibility of the models as the SOC limit is approached. Results will be presented to show that the susceptibility of the 2-D driven current-sheet model mentioned above diverges in agreement with this SOC theory. As in a 1-D driven current-sheet model discussed earlier by Uritsky et al. [Phys. Rev. E, 2002], this divergence is governed by a reduced control parameter that allows a finite input rate in the scaling-neighborhood of the SOC limit. We will conclude that, over a range of finite driving rates, the behavior of the 2-D driven current sheet model is consistent with the mean-field SOC theory of Vespignani and Zapperi.
DE: 2407 Auroral ionosphere (2704)
DE: 2753 Numerical modeling
DE: 2764 Plasma sheet
DE: 3210 Modeling
DE: 3220 Nonlinear dynamics
SC: Nonlinear Geophysics [NG]
MN: 2004 AGU Fall Meeting