Relaxation of a thermal perturbation in a collisional plasma

The relationship between the nonlocal and nonstationary effects in electron heat transport processes in a weakly collisional plasma is investigated by considering the problem of the relaxation of a thermal perturbation as an example. It is shown that, for small-scale perturbations, the electron thermal conductivity depends not only on the temperature scale length but also on time. The consequence is that there exist two qualitatively different characteristic relaxation regimes of thermal perturbations on small and large scale lengths. As a result, the evolution of hot spots in laser plasmas should be described with allowance for the nonstationary nature of electron heat transport. In the course of this evolution, relaxation on the collisional kinetic time scale is clearly seen to change into relaxation on the collisional hydrodynamic time scale