Distinct Scaling Regimes of Energy Release Dynamics in the Nighttime Magnetosphere

TL;DR

This study reveals two distinct energy release regimes in the nighttime magnetosphere, with different statistical behaviors indicating varied underlying physical processes in the inner and outer plasma sheet regions.

Contribution

It identifies and characterizes distinct scaling regimes of energy release in the magnetosphere based on auroral emission event analysis, highlighting different physics in inner and outer plasma sheets.

Findings

Inner plasma sheet shows substorm-scale disturbances violating power-law behavior.

Outer plasma sheet exhibits nearly perfect power-law statistics across scales.

Different scaling regimes suggest varied physical mechanisms in magnetospheric regions.

Abstract

Based on a spatiotemporal analysis of POLAR UVI images, we show that the auroral emission events that initiate equatorward of the isotropic boundary (IB) obtained from a time-dependent empirical model, have systematically steeper power-law slopes of energy, power, area and lifetime probability distributions compared to the events that initiate poleward of the IB. The low-latitude group of events contains a distinct subpopulation of substorm-scale disturbances violating the power-law behavior, while the high latitude group is described by nearly perfect power-law statistics over the entire range of scales studied. The results obtained indicate that the inner and outer portions of the plasma sheet are characterized by substantially different scaling regimes of bursty energy dissipation suggestive of different physics in these regions.