Rotation of Tokamak-Plasmas out of Mechanical Equilibria, in Absence of External Torques

TL;DR

This paper investigates how tokamak plasmas can rotate out of mechanical equilibrium without external torques, using thermodynamics principles, and finds they can rotate freely with speeds exceeding traditional estimates, minimizing dissipation.

Contribution

It applies Prigogine's thermodynamics theorem to plasma rotation, showing plasmas can rotate freely out of equilibrium with higher speeds than neoclassical predictions.

Findings

Plasmas can rotate as a rigid body in the toroidal direction without external torque.

Toroidal rotation can induce faster poloidal rotation than neoclassical theory predicts.

The plasma configuration minimizes dissipation when rotation frequencies reach certain values.

Abstract

Rotation of tokamak-plasmas, not at the mechanical equilibrium, is investigated utilizing a theorem of thermodynamics, established by Prigogine. This theorem, suitably applied to toroidally confined plasmas, suggests that the global barycentric rotations of the plasma, in the toroidal and poloidal directions, are pure reversible processes. In case of negligible viscosity and by supposing the validity of the balance equation for the internal forces, we show that the plasma, even not in the mechanical equilibrium, may freely rotate as a rigid body in the toroidal direction with an angular frequency with an angular frequency, which may be higher than the neoclassical estimation. In addition, its toroidal rotation may cause the plasma to rotate globally in the poloidal direction at a speed faster than the expression found by the neoclassical theory. The eventual configuration is attained when the toroidal and poloidal angular frequencies reaches the values that minimize dissipation.