Relaxation Processes in Solar Wind Turbulence

TL;DR

This paper demonstrates the observation of localized relaxation events in solar wind turbulence, showing that such equilibria can occur during the turbulent cascade, impacting plasma turbulence statistics.

Contribution

It provides the first observational evidence of local relaxation events in the solar wind using multi-spacecraft data analysis.

Findings

Localized relaxation events are observed in the solar wind.

Relaxation processes occur during the turbulent cascade.

These events influence plasma turbulence statistics.

Abstract

Based on global conservation principles, magnetohydrodynamic (MHD) relaxation theory predicts the existence of several equilibria, such as the Taylor state or global dynamic alignment. These states are generally viewed as very long-time and large-scale equilibria, which emerge only after the termination of the turbulent cascade. As suggested by hydrodynamics and by recent MHD numerical simulations, relaxation processes can occur during the turbulent cascade that will manifest themselves as local patches of equilibrium-like configurations. Using multi-spacecraft analysis techniques in conjunction with Cluster data, we compute the current density and flow vorticity and for the first time demonstrate that these localized relaxation events are observed in the solar wind. Such events have important consequences for the statistics of plasma turbulence.