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Self-Organization and Heating by Inward Diffusion in Magnetospheric Plasmas

Naoki SATO, Zensho YOSHIDA and Yohei KAWAZURA

Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba 277-8561, Japan

(Received 22 October 2015 / Accepted 19 January 2016 / Published 24 February 2016)

Abstract

Through the process of inward diffusion, a strongly localized clump of plasma is created in a magnetosphere. The creation of the density gradient, instead of the usual flattening by a diffusion process, can be explained by the topological constraints given by the adiabatic invariants of magnetized particles [Z. Yoshida and S.M. Mahajan, Prog. Theor. Exp. Phys. 2014, 073J01 (2014). N. Sato and Z. Yoshida, J. Phys. A: Math. Theor. 48, 205501 (2015).]. After developing a canonical formalism for the standard guiding center dynamics in a dipole magnetic field, we complete our attempt to build a statistical mechanics on a constrained phase space by discussing the construction principles of the associated diffusion operator. We then investigate the heating mechanism associated with inward diffusion: as particles move toward regions of higher magnetic field, they experience preferential heating of the perpendicular (with respect to the magnetic field) temperature in order to preserve the magnetic moment. A relationship between conservation of bounce action and temperature isotropy emerged. We further show that this behavior is scaled by the diffusion parameter of the Fokker-Planck equation. These results are confirmed by numerical simulations.

Copyright (c) 2016 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

inward diffusion, heating, anistropy, phase space foliation, Fokker-Planck equation

DOI: 10.1585/pfr.11.2401009

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