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The new entropy concept for the collective magnetic equilibria developed in preceding papers is applied to the description of the states of a Tokamak subject to Ohmic and auxiliary heating. The condition of existence of steady-state plasmas with vanishing entropy production implies, on the one hand, the resilience of specific current density profiles and, on the other, severe restrictions on the scaling of the confinement time with power and current in the presence of Ohmic relaxation. These restrictions are consistent with the Goldston scaling and with the existence of a heat pinch.

A wave-dynamical analysis of the interaction of the ordinary wave propagating perpendicularlj to the magnetic field across the electron cyclotron resonance is performed. A sufficient condition for the validity of a WKB approach is obtained. but it is shown that as far as the calculation of wave absorption is concerned. WKB results remain a good approximation. even if this condition is biolated.

The processes of propagation and absorption of electron cyclotrori extraordinary modes in a Tokamak type plasma slab are studied by means of a wave-dynamical system of differential equations in which temperature effects are taken into account. Also the mode conversion of the incoming wave into Bernstein waves is described by the propagation equations and is analysed in the parameter space together with its effects on the global absorption. Similarities and discrepancies between the results of the numerical integration of the full-wave system and those provided by the WKB approximation are discussed as a function of the electron density and temperature.

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