Abstract. The radial neoclassical fluxes of electrons in the 1/ν−regime are calculated with relativistic effects taken into account and compared with those in the non-relativistic approach. The treatment is based on the relativistic drift-kinetic equation with the thermodynamic equilibrium given by the relativistic MaxwellJüttner distribution function. It is found that for the range of fusion temperatures, T e < 100 keV, the relativistic effects produce a reduction of the radial fluxes which does not exceed 10%. This rather small effect is a consequence of the non-monotonic temperature dependence of the relativistic correction caused by two counteracting factors: a reduction of the contribution from the bulk and a significant broadening with the temperature growth of the energy range of electrons contributing to transport.The relativistic formulation for the radial fluxes given in this paper is expressed in terms of a set of relativistic thermodynamic forces which is not identical to the canonical set since it contains an additional relativistic correction term dependent on the temperature. At the same time, this formulation allows application of the non-relativistic solvers currently used for calculation of mono-energetic transport coefficients.

Abstract. The collisional coupling of relativistic electrons and non-relativistic ions in hot plasmas has been analysed. It is found that relativistic effects produce a new feature: while the condition T e < 3T i guarantees a stable collisional coupling between electrons and ions in low-temperature plasmas, relativistic effects shift the upper T e /T i boundary of stability to higher values. Moreover, for sufficiently high temperatures, T e,i > 75 keV, collisional decoupling between relativistic electrons and ions becomes impossible.

In the paper, the Braginskii equations for relativistic electrons in hot plasmas with slow macroscopic fluxes are derived. This consideration is suitable for description of the typical fusion plasma with the temperatures of about several tens of kiloelectronvolt, when the plasma rotation and the longitudinal currents should be taken into account. Contrary to other papers devoted to classical description of transport processes in fusion devices, as well as to fully relativistic description of the astrophysical objects, we propose the mixed approach with fully relativistic kinetics for the hot electrons and non-relativistic macroscopic fluxes. The obtained form of the Braginskii equations includes all important features of relativistic hydrodynamics, has the same form as the classical representation, which is currently implemented into modern transport codes, and can easily replace the latter.

In the paper, relativistic equations of local hydrodynamics for the laboratory fusion plasmas are obtained. Relativistic effects in the physics of electron transport appear primarily because of macroscopic features of relativistic thermodynamic equilibrium given by the Maxwell-Jüttner distribution function, and the characteristic velocity of plasma flow is significantly small: 𝑉 ≪ 𝑣𝑡𝑒 < 𝑐. We propose an approach in which the plasma electrons are treated as fully relativistic and the hydrodynamic flow is treated in the weakly relativistic approximation. For convenience, the obtained relativistic effects are divided between “quasi-relativistic” terms, which in the nonrelativistic limit coincide with well-known expressions, and fully relativistic terms, which disappear at 𝑐 → ∞. The considered mixed approach can be useful for construction of transport models for numerical studies of both astrophysical objects and hot fusion plasma.

In the present work, the neoclassical transport theory in tokamaks is re-considered with the relativistic effects for electrons taken into account. Since such effects are important only in high-temperature plasmas, only the low collisional banana regime has been considered. The obtained formulations give a possibility to calculate the electron neoclassical fluxes in very broad range of temperatures.