Laboratory evidence of electron pressure anisotropy driving plasmoid mediated magnetic reconnection

TL;DR

This study combines simulations and experiments to demonstrate that electron pressure anisotropy can drive plasmoid-mediated magnetic reconnection, even without classical resistivity, impacting plasma turbulence and particle acceleration.

Contribution

It reveals that electron pressure anisotropy is a key driver of tearing instability and reconnection, a novel insight supported by hybrid simulations and laser-driven experiments.

Findings

Electron pressure anisotropy enhances tearing instability growth rate.

Reconnection persists without classical resistivity due to pressure anisotropy.

Dissipative effects like resistivity stabilize the current sheet.

Abstract

Plasmoid-driven magnetic reconnection in elongated current sheets is suspected to be an ubiquitous phenomenon in space and astrophysical plasmas, but the mechanisms driving its onset and dynamics are still debated. Deciphering the physical mechanisms dominating the destabilization and fragmentation of the current sheet, as well as its evolution, would have a wide impact into our understanding of the induced plasma turbulence and particle acceleration. Here, by coupling 3D hybrid simulations with laser-driven experiments that involve counterflowing high-energy-density magnetized plasmas with a long aspect ratio of their contact layer, we show that electron pressure anisotropy is the driving factor of the growth rate of the tearing instability, and will sustain the reconnection process even without classical resistivity. Dissipative mechanisms, such as resistivity and isotropization, are further found to stabilize the sheet to varying degrees, thus modifying plasmoid formation. By identifying the roles of pressure anisotropy, dissipation, and large-scale geometry, our work lays the groundwork for the evaluation of plasmoid-driven reconnection impact on the dynamics of laboratory and astrophysical plasmas.