Cross field thermal transport in highly magnetized plasmas

Abstract
By combining the Poynting vector with the resistive MHD equations it is shown that the c ross field thermal diffusivity of electrons at the limit of very strong magnetic fields sca les as 2 / 3 2 ~ ~ ! ∀ e s ee e T # ∃ % where Te is the electron temperature, ee ! is the e-e collision frequency and s ! is the skin depth. This effect is independent of the magnetic fie ld strength B and of the perpendicular electron diffusion, and is due to kinetic energy exchange betw een colliding electrons moving on parallel field lines in the presence of a cross field temperature gra dient. For highly magnetized plasmas the present mode of heat transport is l arger than the classical heat conduction 2 ~ ! ∀ B e # and provides with a microscopic mechanism that balances magnetic diffusion (paleoclassical hypothesis) leading to an explanation of the anoma lous heat transport observed in tokamaks.