Magnetic reconnection in the era of exascale computing and multiscale experiments

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.Website summary: Magnetic reconnection explosively releases stored magnetic energy in astrophysical plasmas. Thanks to advances in observations, exascale computing and multiscale experiments, it will be possible to solve outstanding physics problems, including the immense separation between global and dissipation scales, reconnection onset, and particle acceleration.

Dense Gas Formation via Collision-induced Magnetic Reconnection in a Disk Galaxy with a BiSymmetric Spiral Magnetic Field

“…First, it is necessary to distinguish between magnetic reconnection in a current sheet and fast reconnection due to the plasmoid instability. Generally speaking, there are three phases of magnetic reconnection (see, e.g., Pucci & Velli 2014;Comisso et al 2016;Ji et al 2022). In phase-1, antiparallel magnetic fields are brought together to form a current sheet at the field-reversing interface.…”

Particle Acceleration in Magnetic Reconnection with Ad hoc Pitch-angle Scattering

“…Corresponding author: Grant Johnson grj@princeton.edu Magnetic reconnection converts magnetic energy into plasma energies by releasing free energy stored in the configuration of field lines of force (Yamada et al 2010;Ji et al 2022). It has been proposed as a mechanism for producing high energy charged particles in space, solar, and astrophysical processes.…”