Observation of Inertial-range Energy Cascade within a Reconnection Jet in Earth's Magnetotail

TL;DR

This study provides direct evidence of an inertial-range energy cascade within a reconnection jet in Earth's magnetotail, revealing a highly energetic turbulence process distinct from solar wind conditions.

Contribution

First direct observation of inertial-range turbulence cascade during magnetic reconnection in Earth's magnetotail, with quantitative energy transfer rate estimation.

Findings

Kolmogorov $-5/3$ scaling observed in spectra

Linear scaling of third-order structure functions confirmed cascade

Energy transfer rate estimated at $ extasciitilde 10^{7}$ J kg$^{-1}$ s$^{-1}$, much higher than solar wind

Abstract

Earth's magnetotail region provides a unique environment to study plasma turbulence. We investigate the turbulence developed in an exhaust produced by magnetic reconnection at the terrestrial magnetotail region. Magnetic and velocity spectra show broad-band fluctuations corresponding to the inertial range, with Kolmorogov $-5/3$ scaling, indicative of a well developed turbulent cascade. We examine the mixed, third-order structure functions, and obtain a linear scaling in the inertial range. This linear scaling of the third-order structure functions implies a scale-invariant cascade of energy through the inertial range. A Politano-Pouquet third-order analysis gives an estimate of the incompressive energy transfer rate of $\sim 10^{7}~\mathrm{J\,kg^{-1}\,s^{-1}}$. This is four orders of magnitude higher than the values typically measured in 1 AU solar wind, suggesting that the turbulence cascade plays an important role as a pathway of energy dissipation during reconnection events in the tail region.