Laboratory Observation of Transition from Collisional Slow to Collisionless Fast Reconnection
Phys. Rev. Lett. 136, 085101 – Published 24 February, 2026
DOI: https://doi.org/10.1103/9l36-74my
Abstract
Temporal transition of an externally driven antiparallel asymmetric magnetic reconnection from collisional slow to collisionless fast regime is observed in a laboratory plasma for the first time. This transition is initiated when the two-fluid Hall effect begins to dominate over collisional effects at the X point, characterized by the ratio of electron-ion collision mean free path to current sheet thickness exceeding unity. Prior to the transition, an enhanced reconnection electric field develops on the low-density side where electrons are heated both ohmically and by large-amplitude lower-hybrid drift waves (LHDW) before collisionality at the X-point drop significantly. These LHDWs generate anomalous resistivity accounting for 30% of the reconnection electric field. The observed time evolution is consistent with the hybrid collisionless-collisional reconnection scenario relevant to onset of asymmetric reconnection in natural plasmas.
