Intermittent Turbulence and SOC Dynamics in a 2-D Driven Current-Sheet Model

Borovsky et al. [Phys Plasma, 1997] have shown that Earth's magnetotail plasma sheet is strongly turbulent. More recently, Borovsky and Funsten [JGR, 2003] have shown that eddy turbulence dominates and have suggested that the eddy turbulence is driven by fast flows that act as jets in the plasma. Through basic considerations of energy and magnetic flux conservation, these fast flows are thought to be localized to small portions of the total plasma sheet and to be generated by magnetic flux reconnection that is similarly localized. Angelopoulos et al. [Phys Plasma, 1999], using single spacecraft Geotail data, have shown that the plasma sheet turbulence exhibits signs of intermittence and Weygand et al. [JGR, 2005], using four spacecraft Cluster data, have confirmed and expanded on this conclusion. Uritsky et al. [JGR, 2002; GRL, 2003], using Polar UVI image data, have shown that the evolution of bright, night-side, UV auroral emission regions is consistent with many of the properties of systems in self-organized criticality (SOC). Klimas et al. [JGR, 2000; 2004] have suggested that the auroral dynamics is a reflection of the dynamics of the fast flows in the plasma sheet. Their hypothesis is that the transport of magnetic flux/energy through the magnetotail is enabled by scale-free avalanches of localized reconnection whose SOC dynamics are reflected in the auroral UV emission dynamics. A corollary of this hypothesis is that the strong, intermittent, eddy turbulence of the plasma sheet is closely related to its critical dynamics. The question then arises: Can in situ evidence for the SOC dynamics be found in the properties of the plasma sheet turbulence? A 2-dimensional numerical driven current-sheet model of the central plasma sheet has been developed that incorporates an idealized current-driven instability with a resistive MHD system. It has been shown that the model can evolve into SOC in a physically relevant parameter regime. Initial results from a study of intermittent turbulence in this model and the relationship of this turbulence to the model's known SOC dynamics will be discussed.