Thin current sheet formation: comparison between Earth's magnetotail and coronal streamers

TL;DR

This study compares the formation of thin current sheets in Earth's magnetotail and solar corona streamers, revealing similar behaviors driven by plasma pressure gradients despite different environments.

Contribution

It provides a comparative analysis of current sheet evolution in magnetotail and coronal streamers, highlighting the role of plasma pressure gradients in both systems.

Findings

Pre-reconnection current sheet thinning is controlled by plasma pressure gradients.

Scaling laws for current density, magnetic field, and pressure are similar in both systems.

Magnetotail data and simulations can inform models of solar corona current sheets.

Abstract

Magnetic field line reconnection is a universal plasma process responsible for the magnetic field topology change and magnetic field energy dissipation into charged particle heating and acceleration. In many systems, the conditions leading to the magnetic reconnection are determined by the pre-reconnection configuration of a thin layer with intense currents -- otherwise known as the thin current sheet. In this study we investigate two such systems: Earth's magnetotail and helmet streamers in the solar corona. The pre-reconnection current sheet evolution has been intensely studied in the magnetotail, where in-situ spacecraft observations are available; but helmet streamer current sheets studies are fewer, due to lack of in-situ observations -- they are mostly investigated with numerical simulations and information that can be surmised from remote sensing instrumentation. Both systems exhibit qualitatively the same behavior, despite their largely different Mach numbers, much higher at the solar corona than at the magnetotail. Comparison of spacecraft data (from the magnetotail) with numerical simulations (for helmet streamers) shows that the pre-reconnection current sheet thinning, for both cases, is primarily controlled by plasma pressure gradients. Scaling laws of the current density, magnetic field, and pressure gradients are the same for both systems. We discuss how magnetotail observations and kinetic simulations can be utilized to improve our understanding and modeling of the helmet streamer current sheets.