MHD consistent cellular automata (CA) models I: Basic features

Abstract

A set-up is introduced which can be superimposed onto the existing solar flare cellular automata (CA) models, and which specifies the interpretation of the model's variables. It extends the CA models, yielding the magnetic field, the current, and an approximation to the electric field, in a way that is consistent with Maxwell's and the MHD equations. Applications to several solar flare CA models during their natural state (self-organized criticality (SOC)) show, among others, that (1) the magnetic field exhibits characteristic large-scale organization over the entire modeled volume; (2) the magnitude of the current seems spatially dis-organized, with no obvious tendency towards large-scale structures or even local organization; (3) bursts occur at sites with increased current, and after a burst the current is relaxed; (4) by estimating the energy released in individual bursts with the use of the current as Ohmic dissipation, it turns out that the power-law distributions of the released energy persist. The CA models, extended with the set-up, can thus be considered as models for energy-release through current-dissipation. The concepts of power-law loading and anisotropic events (bursts) in CA models are generalized to 3--D vector-field models, and their effect on the magnetic field topology is demonstrated.