The rapid rearrangement of magnetic field topology in a plasma, converting stored magnetic energy into kinetic and thermal energy — the fundamental process behind solar flares, sawtooth crashes, and disruptions.
Magnetic reconnection occurs when oppositely directed magnetic field lines break and rejoin in a new configuration, releasing stored magnetic energy as heat and kinetic energy. In an ideal (perfectly conducting) plasma, field lines cannot break; reconnection requires a localised breakdown of ideal MHD, typically in thin current sheets where resistive or kinetic effects dominate.[1]
The classical Sweet–Parker model predicts reconnection rates far too slow to explain observed phenomena. Modern understanding invokes plasmoid instabilities, Hall-MHD effects, or kinetic physics to produce “fast” reconnection at rates consistent with observations.[2]
In tokamaks, reconnection at rational surfaces drives sawtooth crashes (at q = 1) and major disruptions (at q = 2). Understanding and controlling reconnection is essential for disruption avoidance. The Magnetic Reconnection Experiment (MRX) at PPPL has provided key laboratory data on reconnection physics.[3]