Multiscale auroral emission statistics as evidence of turbulent reconnection in Earth's midtail plasma sheet

Abstract

We provide indirect evidence for turbulent reconnection in Earth's midtail plasma sheet by reexamining the statistical properties of bright, nightside auroral emission events as observed by the UVI experiment on the Polar spacecraft and discussed previously by Uritsky et al. (2002, 2003, 2006). The events are divided into two groups: (1) those that map to ∣XGSM∣ < 12 RE in the magnetotail and do not show scale‐free statistics and (2) those that map to ∣XGSM∣ > 12 RE and do show scale‐free statistics. The ∣XGSM∣ dependence is shown to most effectively organize the events into these two groups. Power law exponents obtained for group 2 are shown to validate the conclusions of Uritsky et al. concerning the existence of critical dynamics in the auroral emissions. It is suggested that the auroral dynamics is a reflection of a critical state in the magnetotail that is based on the dynamics of turbulent reconnection in the midtail plasma sheet.