Study of driven magnetic reconnection in a laboratory plasma

TLDR

The experiment was built to study fundamental magnetic reconnection physics in a controlled laboratory environment. The device creates a high‑S, low‑ρi magnetohydrodynamic plasma and allows controlled study of the third‑component effects in reconnection. Controlled boundary conditions enable fully 3D reconnection, revealing that the third magnetic component determines neutral‑sheet geometry: antiparallel reconnection yields a thin double‑Y diffusion region down to the ion gyroradius, while co‑helicity reconnection produces an O‑shaped diffusion region that expands into a spheromak.

Abstract

The magnetic reconnection experiment has been constructed to investigate the fundamental physics of magnetic reconnection in a well-controlled laboratory setting. This device creates an environment satisfying the criteria for a magnetohydrodynamic plasma (S≫1, ρi≪L). The boundary conditions can be controlled externally, and experiments with fully three-dimensional reconnection are now possible. In the initial experiments, the effects of the third vector component of reconnecting fields have been studied. Two distinctively different shapes of neutral sheet current layers, depending on the third component, are identified during driven magnetic reconnection. Without the third component (antiparallel or null–helicity reconnection), a thin double-Y-shaped diffusion region is identified. A neutral sheet current profile is measured accurately to be as narrow as the order of the ion gyroradius. In the presence of an appreciable third component (co-helicity reconnection), an O-shaped diffusion region appears and grows into a spheromak configuration.