Kinetic description of rotating Tokamak plasmas with anisotropic temperatures in the collisionless regime

TL;DR

This paper develops a kinetic theory framework for collisionless, anisotropic, rotating Tokamak plasmas using Vlasov-Maxwell equations and gyrokinetics, providing analytical solutions that incorporate pressure anisotropies and differential rotation.

Contribution

It introduces a perturbative gyrokinetic approach to construct asymptotic kinetic equilibria in collisionless Tokamak plasmas with anisotropic temperatures and differential rotation.

Findings

Existence of generalized bi-Maxwellian kinetic equilibria.

Kinetic equilibria can sustain differential rotation and temperature anisotropy.

Solutions satisfy quasi-neutrality and Ampere's law constraints.

Abstract

A largely unsolved theoretical issue in controlled fusion research is the consistent \textit{kinetic} treatment of slowly-time varying plasma states occurring in collisionless and magnetized axisymmetric plasmas. The phenomenology may include finite pressure anisotropies as well as strong toroidal and poloidal differential rotation, characteristic of Tokamak plasmas. Despite the fact that physical phenomena occurring in fusion plasmas depend fundamentally on the microscopic particle phase-space dynamics, their consistent kinetic treatment remains still essentially unchalleged to date. The goal of this paper is to address the problem within the framework of Vlasov-Maxwell description. The gyrokinetic treatment of charged particles dynamics is adopted for the construction of asymptotic solutions for the quasi-stationary species kinetic distribution functions. These are expressed in terms of the particle exact and adiabatic invariants. The theory relies on a perturbative approach, which permits to construct asymptotic analytical solutions of the Vlasov-Maxwell system. In this way, both diamagnetic and energy corrections are included consistently into the theory. In particular, by imposing suitable kinetic constraints, the existence of generalized bi-Maxwellian asymptotic kinetic equilibria is pointed out. The theory applies for toroidal rotation velocity of the order of the ion thermal speed. These solutions satisfy identically also the constraints imposed by the Maxwell equations, i.e. quasi-neutrality and Ampere's law. As a result, it is shown that, in the presence of non-uniform fluid and EM fields, these kinetic equilibria can sustain simultaneously toroidal differential rotation, quasi-stationary finite poloidal flows and temperature anisotropy.