Unveiling the Trigger Mechanism of an Explosive Plasma Eruption in a Toroidal Magnetic Fusion Device

Abstract Explosive phenomena, such as edge-localized modes (ELMs) in controlled-nuclear-fusion-devices and solar flares on the sun, have eluded scientists for a long time. Despite extensive investigation in laboratory and astrophysical plasmas, the trigger mechanism has remained elusive. Herein, we present the dynamics of tearing parity mode during an explosive eruption in magnetized plasmas and identified a critical threshold for mode amplitude. When the amplitude exceeds this threshold, an ELM-event is triggered, inducing the collapse of the plasma. The result also demonstrates rapid magnetic reconnection and the formation of stochasticity in magnetic field lines. The observed timescale between trigger events and the subsequent large-scale collapse provides a semiquantitative support for the hypothesis that magnetic braiding causes nonlinear instability and explosive growth. As a corollary, the mechanism of ELM-control using external magnetic-coils is also elucidated. These results have significant implications for laboratory and astrophysical understanding of magnetized plasma dynamics.