Simulation of the dynamics in the magnetotail current sheet

TL;DR

This paper models the magnetotail current sheet dynamics using a cellular automaton approach, revealing power-law distributions of energy avalanches and their relation to magnetic substorms influenced by interplanetary magnetic field conditions.

Contribution

It introduces a cellular automaton model for magnetosphere current sheet dynamics that captures self-organized criticality and links avalanches to substorm activity.

Findings

Power-law distribution of avalanche sizes indicating SOC behavior

Big avalanches correlate with intense magnetic substorms

Negative Bz IMF component triggers substorm activity

Abstract

The dynamics in the magnetosphere current sheet was simulated following transformations to the rectangular NxM array of cells (cellular automaton) originally proposed by Koselov and Koselova (2002). The magnetosphere part of the modeling system was organized as a rectangular arrangement of cells with a stored energy, a local redistribution of the energy will exist when a value threshold is exceeded in one of the cells. We assume that the threshold value in each cell depends on external control parameter which influences the long boundaries of the rectangular array (40x80). The model dynamics controlled by the z-component of the interplanetary magnetic field (Bz) as well as analogies between the model transient processes and the observed substorm auroral activations are discussed. The Bz correspond to temporary windows of the solar wind for a group of magnetic clouds and plasmoids. The model simulates organized patterns in the energy distribution. The function of distribution of probability (or PDF) of the size of the avalanches have a power-law form, showing evidences of a system with Self-Organized Criticality (SOC). The occurrence of big avalanches in the model is related with the activation of some intense magnetic substorm. The arrival to the terrestrial magnetopause of a solar wind with Bz negative is a fundamental condition of occurrence of magnetic substorms. While more negative it is the Bz IMF component bigger it is the value of the AE index and trigger a strong magnetic substorm.