Let us consider heat conduction in a dilute plasma. The calculation of the diffusion coefficient is similar to the calculation of the electrical conductivity. The effective collision rate is given by

 \omega \approx \frac{n q^4}{m^2 v^3}

where  n is the number density,  q is the electric charge,  m is the electron mass and  v is the thermal velocity. The diffusion coefficient is given by

 D \approx v^2/\omega \approx \frac{m^2 v^5}{n q^4}

The heat flux is given by Fick's law

 F_c \approx D \nabla \left(n k T \right ) \approx \frac{\left(k T \right )^{5/2}}{m^{1/2} q^4} \nabla \left(k T \right )

where T \, is the temperature and  k is the Boltzmann constant.