HR: 1340h
AN: NG23A-1193    [Abstracts]
TI: Scale-Invariance and Universality in a 2-D Turbulent Current Sheet Model
AU: Urtisky, V M
EM: uritsky@geo.phys.spbu.ru
AF: Institute of Physics, St. Petersburg State University, Ulianovskaya-1, St. Petersburg, 198504 Russian Federation
AU: * Klimas, A J
EM: alex.klimas@nasa.gov
AF: NASA Goddard Space Flight Center, Code 692, Greenbelt, MD 20771 United States
AU: Vassiliadis, D
EM: vassi@electra.gsfc.nasa.gov
AF: USRA at NASA/Goddard Space Flight Center, Code 692, Greenbelt, MD 20771 United States
AU: Pulkkinen, A
EM: antti.pulkkinen@gsfc.nasa.gov
AF: NRC at NASA/Goddard Space Flight Center, Code 692, Greenbelt, MD 20771 United States
AB: Magnetospheric substorm is a complex and partially unpredictable phenomenon involving vast ranges of spatial and temporal scales. Recently, it has been revealed based on POLAR UVI observations that multiscale dynamics of auroral active areas associated with multiscale activity in the magnetotail (BBFs, pseudo-breakups, intermittent turbulence) is arranged across different time, space and energy scales in a scale-invariant way typical for many-body nonlinear systems in the vicinity of a nonequilibrium critical point. Remarkable stability of the observed phenomenon under changeable solar wind conditions has been interpreted as a manifestation of self-organized critical (SOC) dynamics in the magnetotail plasma sheet. In this paper, we present first numerical results leading to the identification of the universality class of such dynamics as represented by the 2-D current sheet model (CSM) proposed by A. Klimas et al. [JGR, 2004, 109(A2)]. Based on the analysis of power-law critical relations characterizing statistical scaling, spreading behavior and fractal properties of current-driven instabilities in CSM, it is shown that the model belongs to the universality class of stochastic directed sandpiles (SDSP) characterized by strongly anisotropic energy transfer, and seems to operate in the regime that can be described using a relatively simple dynamic mean-field approximation. A number of scaling relations for different groups of critical exponents is verified, and a quantitative agreement between CSM exponents and the exponents reported in the literatures for other SDSP models is demonstrated. Most of the critical exponents obtained for CSM are shown to be reasonably close to the exponents calculated earlier for POLAR UVI data, which suggests possible casual relation between the SOC dynamics in the magnetotail plasma sheet and scale-invariant high-latitude geomagnetic perturbations.
DE: 7839 Nonlinear phenomena
DE: 2159 Plasma waves and turbulence
DE: 2753 Numerical modeling
DE: 2788 Storms and substorms
SC: Nonlinear Geophysics [NG]
MN: 2004 AGU Fall Meeting