Dynamical and fractal properties in a SOC model of magnetic substorms

MORALES, L. F.; CHARBONNEAU, P.; LIU, W. W.

Journal of Atmospheric and Solar-Terrestrial Physics

ELSEVIER

Lugar: Amsterdan; Año: 2017

1364-6826

p { margin-bottom: 0.25cm; line-height: 120%; }Earth´smagnetosphere is a complex system exhibiting stochastic propertiesboth in spatial and temporal domains as has been shown by ground andin-situ observations. Although the physical mechanisms responsiblefor this behavior are not fully understood, the fact that somemagnetospheric phenomena exhibit power law statistics, contributes tothe idea that the magnetosphere is in a self-organized critical (SOC)state. Assuming that the central plasma sheet in the Earth´smagnetotail is a collection of nonlinearly interacting flux tubes, westudy the evolution of the magnetic field in a weakly perturbedmagnetosphere using a simple 2D cellular automaton. This numericalmodel produced spatially and temporally intermittent, avalanche-likerelease of magnetic energy, with frequency distributions of avalanchesize parameters being in the form of power laws as shown in W. W.Liu. et al., JGR, 2011 (116). We calculate the exponents describingthe spreading activity, namely, the geometrical properties ofavalanches and correlation coefficients between total E, peak energyP and avalanche duration T. Our results support the idea that thedynamics of energy dissipation regions in the magnetotail obeysstatistical scaling laws consistent with the behavior of a generalclass of statistical physical systems in the vicinity of a stationarycritical point. Thus, the proposed numerical model is likely tooperate in a self-organized critical regime. The obtained spreadingexponents and correlation coefficients closely compare with thevalues reported earlier for the nighttime auroral emission statistics(V. M. Uritsky et al., JGR, 2002) characterizing burtsy energydissipation in the magnetotail plasma sheet.