Abstract
By examining the entropy production in fully kinetic simulations of collisional plasmas, it is shown that the transition from collisional Sweet-Parker reconnection to collisionless Hall reconnection may be viewed as a thermodynamic phase transition. The phase transition occurs when the reconnection electric field satisfies , where is the electron-to-ion mass ratio and is the Dreicer electric field. This condition applies for all , including , where the Hall regime vanishes and a direct phase transition from the collisional to the kinetic regime occurs. In the limit , this condition is equivalent to there being a critical electron temperature , where is the ion cyclotron frequency and is the current sheet half-thickness. The heat capacity of the current sheet changes discontinuously across the phase transition, and a critical power law is identified in an effective heat capacity. A model for the time-dependent evolution of an isolated current sheet in the collisional regime is derived.
- Received 1 March 2021
- Revised 30 April 2021
- Accepted 17 June 2021
DOI:https://doi.org/10.1103/PhysRevLett.127.055102
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