Radiatively Cooled Magnetic Reconnection Experiments Driven by Pulsed Power

TL;DR

This study explores magnetic reconnection under radiative cooling conditions through innovative experiments and simulations, revealing plasmoid formation and radiative effects relevant to astrophysical phenomena.

Contribution

It introduces the first experimental and computational investigation of radiatively cooled magnetic reconnection in a laboratory setting, bridging astrophysics and high-energy-density physics.

Findings

Confirmation of plasmoid formation during reconnection

Evidence of strong radiative cooling effects

Validation of simulation predictions with experimental data

Abstract

Magnetic reconnection is a ubiquitous process in astrophysical plasmas, responsible for the explosive conversion of magnetic energy into thermal and kinetic energy. In extreme astrophysical systems, such as black hole coronae and neutron star magnetospheres, radiative cooling modifies the energy partition by rapidly removing internal energy. In this thesis, we perform experimental and computational studies of magnetic reconnection in a radiatively cooled regime, previously unexplored in reconnection studies. The Magnetic Reconnection on Z (MARZ) experiments consist of a dual exploding wire array, driven by a 20 MA peak, 300 ns rise time current generated by the Z pulsed-power machine (Sandia National Labs). The load generates oppositely-directed supersonic, super-Alfv\'enic, collisional plasma flows with anti-parallel magnetic fields, that generate a reconnection layer, in which the total cooling rate far exceeds the Alfv\'enic transit rate. Two- and three-dimensional simulations of the MARZ experiments are performed in GORGON, an Eulerian resistive magnetohydrodynamic code. The experiments confirm numerical predictions by providing evidence of plasmoid formation and strong radiative cooling. The findings in this thesis are of particular relevance to the generation of radiative emission from reconnection-driven astrophysical events, and to the global dynamics of reconnection in strongly cooled systems. The MARZ experiments also provide a novel platform for investigating radiative effects in high-energy-density and laboratory astrophysics experiments, and for validation of radiation magnetohydrodynamic and atomic spectroscopy codes.