Heat flux in a non-Maxwellian plasma

A hybrid numerical scheme is applied to solve the Landau equation for the electron distribution function over all velocity space. At low velocities the distribution is approximated by using the Spitzer-Härm method [Phys. Rev. 89, 977 (1953)], while at high velocities it is described by the high-velocity form of the Landau equation. The two parts of the distribution function are then matched at a suitably chosen value of electron speed. The distribution function is determined for a thermal structure typical of an active region of the solar atmosphere or flaring solar coronal loop. The heat flux is then calculated from the distribution function and is compared with the classical Fourier law of Spitzer and Härm and with the models of Campbell [Phys. Rev. A 30, 365 (1984)] and Luciani et al. [Phys. Fluids 28, 835 (1985); Phys. Rev. Lett. 51, 1664 (1983)].