A non-linear approach to the kinetic theory of heat conductivity in a plasma

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Abstract
Collisional heat transport in a two-component plasma described by the Landau equation is studied in a regime beyond the linear, small temperature gradient approximation. The non-linear heat conductivity is investigated on the basis of a 'modified moment' expansion of the distribution function together with a 'cumulant expansion' of the entropy source density. The heat flux derived starts as a linear function of the temperature gradient but deviates from linearity and grows slower than logarithmically for large values of the temperature gradient. In connection with the field of laser-plasma interactions, the authors conclude that qualitative (but not quantitative) agreement has been reached with the concept of heat flux inhibition, encouraging further improvements of the theory.