Magneto-thermal reconnection processes, related mode momentum and formation of high energy particle populations. (31st May 2017)

• Record Type: Journal Article
• Authors: Coppi, B.; Basu, B.; Fletcher, A.
• Is Part Of: Nuclear fusion. Volume 57:Number 7(2017:Jul.)
• Publication Date: 2017-05-31
• Subjects: magneto-thermal reconnection -- electron temperature gradient -- high energy particle populations; Nuclear fusion -- Periodicals; 621.48405
• DOI: 10.1088/1741-4326/aa6c70
• Languages: English
• ISSNs: 0029-5515

Abstract

Abstract: In the context of a two-fluid theory of magnetic reconnection, when the longitudinal electron thermal conductivity is relatively large, the perturbed electron temperature tends to become singular in the presence of a reconnected field component and an electron temperature gradient. A finite transverse thermal diffusivity removes this singularity while a finite 'inductivity' can remove the singularity of the relevant plasma displacement. Then (i) a new 'magneto-thermal' reconnection producing mode, is found with characteristic widths of the reconnection layer remaining significant even when the macroscopic distances involved are very large; (ii) the mode phase velocities can be both in the direction of the electron diamagnetic velocity as well in the opposite (ion) direction. A numerical solution of the complete set of equations has been carried out with a simplified analytical reformulation of the problem. A sequence of processes is analyzed to point out that high-energy particle populations can be produced as a result of reconnection events. These involve mode-particle resonances transferring energy of the reconnecting mode to a superthermal ion population and the excitation of lower hybrid waves that can lead to a significant superthermal electron population. The same modes excited in axisymmetric (e.g. toroidal) confinement configurations can extract angular momentum from the main body of the plasma column and thereby sustain a local 'spontaneous rotation' of it.