Similarity Invariance of Magnetic States and Nonlocal Transient Effects on Heat Transport in Tokamaks

Abstract

States of stationary magnetic entropy are connected by a similarity transformation that describes a poloidal flux-conserving rearrangement of the equilibrium and a global invariance of the magnetic structure. It is conjectured that the only permissible states in the confinement zone of a tokamak are magnetically similar states of stationary entropy, and that the physical properties of transport in these states are the same, apart from a similarity transformation. This conjecture, which establishes a connection between transport and magnetic structure, allows one to write down a power balance equation in the confinement zone that describes the temperature evolution in transient processes driven by rapid changes of the magnetic equilibrium. In the present paper the following experimental facts are considered in the light of this equation: the sensitivity of the core temperature of the tokamak to edge perturbations of the current channel, the nonlocal, nondiffusive behaviour of heat pulses from the mixing zone observed in heat modulated experiments and the global temperature evolution observed immediately after the L-H transition.