Magnetic reconnection with radiative cooling. I. Optically thin regime

Magnetic reconnection processes in many high-energy-density astrophysical and laboratory plasma systems are significantly affected by radiation; hence traditional, nonradiative reconnection models are not applicable to these systems. Motivated by this observation, the present paper develops a Sweet-Parker-like theory of resistive magnetic reconnection with strong radiative cooling. It is found that, in the case with zero guide field, intense radiative cooling leads to a strong plasma compression, resulting in a higher reconnection rate. The compression ratio and the reconnection layer temperature are determined by the balance between ohmic heating and radiative cooling. The lower temperature in a radiatively cooled layer leads to a higher Spitzer resistivity and, hence, a higher reconnection rate. Several specific radiative processes (bremsstrahlung, cyclotron, and inverse Compton) in the optically thin regime are considered for both the zero- and strong-guide-field cases, and concrete expressions for the reconnection parameters are derived, along with the applicability conditions.