Cyclic Conversion of Particle Kinetic Energy into Reconnected Magnetic Field Energy

Magnetic reconnection has been considered almost exclusively as a process through which magnetic energy is converted into particle kinetic energy. On the other hand recent theoretical developments [1] have illuminated the fact that a cyclic exchange of kinetic and magnetic energy can take place in weakly collisional plasmas by a reconnection process that is allowed by the relevant finite thermal conductivities (longitudinal and transverse to the unreconnected magnetic field). The combined effects of the aligned electron temperature and density gradients allows the reconnected field to grow involving layers that, differently from the case of conventional reconnection driven by current density gradients and relying on an Ohm’s law, remain significant even when the scale distances of the unreconnected field are large. The considered reconnection process is inherently cyclical and, comparing it to the Biermann battery driven by misaligned electron temperature gradient, can be viewed as an alternator. In retrospect, the well known sawtooth and fishbone oscillations of well confined plasmas belong to the class of processes identified on the basis of the results of Ref. [1] considering that the driving factor of the involved reconnection is the particle thermal energy gradient in the first case and the combination of this factor and mode-particle resonances with an injected high energy population in the second case.



[1] B. Coppi and B. Basu, Phys. Lett. A 397, 127265 (2021).