Magnetic reconnection in the era of exascale computing and multiscale experiments

TL;DR

This paper discusses the challenges and opportunities in understanding magnetic reconnection in large-scale astrophysical plasmas, emphasizing the role of exascale computing and multiscale experiments in advancing this field.

Contribution

It highlights the potential of exascale computing and laboratory experiments to address multiscale problems in magnetic reconnection, bridging kinetic and macroscopic scales.

Findings

Plasmoid instability as a multiscale solution for reconnection.

Exascale computing will enable modeling of large-scale reconnection phenomena.

Laboratory experiments are poised to explore regimes relevant to astrophysical plasmas.

Abstract

Astrophysical plasmas have the remarkable ability to preserve magnetic topology, which inevitably gives rise to the accumulation of magnetic energy within stressed regions including current sheets. This stored energy is often released explosively through the process of magnetic reconnection, which produces a reconfiguration of the magnetic field, along with high-speed flows, thermal heating, and nonthermal particle acceleration. Either collisional or kinetic dissipation mechanisms are required to overcome the topological constraints, both of which have been predicted by theory and validated with in situ spacecraft observations or laboratory experiments. However, major challenges remain in understanding magnetic reconnection in large systems, such as the solar corona, where the collisionality is weak and the kinetic scales are vanishingly small in comparison to macroscopic scales. The plasmoid instability or formation of multiple plasmoids in long reconnecting current sheets is one possible multiscale solution for bridging this vast range of scales, and new laboratory experiments are poised to study these regimes. In conjunction with these efforts, we anticipate that the coming era of exascale computing, together with the next generation of observational capabilities, will enable new progress on a range of challenging problems, including the energy build-up and onset of reconnection, partially ionized regimes, the influence of magnetic turbulence, and particle acceleration.