A SOC based avalanche model to study the magnetosphere-ionosphere energy transfer and AE index fluctuations

Abstract

ABSTRACT Magnetosphere-ionosphere energy transfer and AE fluctuations are studied using a cellular automata model of terrestrial magnetosphere based on the concept of self-organised criticality (SOC). The model is a SOC-driven dissipative dynamical system with both spatial and temporal degrees of freedom. The input parameter to this model is derived from the real-time values of solar wind ion density and flow speed data. Both the direction and intensity of the real-time values of the BZ component of the interplanetary magnetic field (IMF) are the factors controlling the energy injection into the system. The model produces an output series which can be regarded as a mathematical representation of the AE index. The spectral response of the simulated output follows a 1/fβ power law, demonstrates a breakpoint at f0 = 0.050 mHz (5.5 hours) having slopes βA = 2.2–2.4 for f > f0 and βB = 0.9–1.0 for f < f0, the typical characteristics of the natural AE index. The entire 23rd solar cycle had been studied using the model. The parameter KA plays a significant role in the entire process. KA represents the remaining percentage of the released energy from the previous magnetosphere-ionosphere energy transfer, stored in the ionosphere.