Evidence for intermittency in Earth's plasma sheet and implications for self-organized criticality

It has been proposed recently that a description of the magnetosphere as a system in a state of self-organized criticality would be fruitful for understanding (and predicting) the global response to solar wind input. In this paper it is shown that the proposed description fits the characteristics of magnetotail plasma flows and their variability. According to observations, the magnetotail is in a bi-modal state: nearly stagnant, except when driven turbulent by transport-efficient fast flows. The distributions of flows are in agreement with sporadic (intermittent) variability in the magnetotail. The variability may resemble hydrodynamic turbulence around a jet. The presence of turbulence alters the conductivity and the mass/momentum diffusion properties across the plasma sheet and may permit cross-scale coupling of localized jets into a global perturbation. Bursty-flow-driven turbulence is a physical process that may have an important role to play in the establishment of a state of self-organized criticality. (C) 1999 American Institute of Physics. [S1070-664X(99)02911-0].