Ion heating and magnetic flux pile-up in a magnetic reconnection experiment with super-Alfvenic plasma inflows

TL;DR

This study investigates magnetic reconnection driven by super-Alfvenic plasma flows, revealing ion heating, magnetic flux pile-up, and temperature equilibration in a stable, long-lasting reconnection layer through detailed optical and polarimetric measurements.

Contribution

It demonstrates the role of plasma kinetic, magnetic, and thermal properties in reconnection, highlighting ion heating and magnetic flux pile-up in a controlled experimental setup.

Findings

Ions are more strongly heated than electrons during reconnection.

Magnetic flux pile-up occurs at the boundary of the reconnection region.

Ion and electron temperatures equilibrate over time in the layer.

Abstract

This work presents a magnetic reconnection experiment in which the kinetic, magnetic and thermal properties of the plasma each play an important role in the overall energy balance and structure of the generated reconnection layer. Magnetic reconnection occurs during the interaction of continuous and steady flows of super-Alfvenic, magnetized, aluminum plasma, which collide in a geometry with two-dimensional symmetry, producing a stable and long-lasting reconnection layer. Optical Thomson scattering measurements show that when the layer forms, ions inside the layer are more strongly heated than electrons, reaching temperatures of Ti~ZTe>300 eV - much greater than can be expected from strong shock and viscous heating alone. Later in time, as the plasma density in the layer increases, the electron and ion temperatures are found to equilibrate, and a constant plasma temperature is achieved through a balance of the heating mechanisms and radiative losses of the plasma. Measurements from Faraday rotation polarimetry also indicate the presence of significant magnetic field pile-up occurring at the boundary of the reconnection region, which is consistent with the super-Alfvenic velocity of the inflows.