Nonlinear energy dissipation in a cellular automaton magnetotail field model

A magnetic field model of the magnetotail current sheet based on cellular a utomaton (CA) is presented. The present isotropic model is a continuously d riven, two-dimensional running CA. The model has a physical interpretation in terms of magnetohydrodynamic (MHD) equations, and features self-organize d critical (SOC) behavior with power-law scalings both in durations and siz es of instabilities (avalanches). The model has nonlinear energy dissipatio n, and shows avalanches with and without an external trigger. Thus the mode l reproduces some of the statistical features recently observed in the magn etotail.