Cross-Magnetic-Field Heat Conduction in Non-neutral Plasmas

This Letter discusses cross-magnetic-field collisional heat transport for a non-neutral plasma in the typical operating regime ${\lambda }_D\gg r_c$, where ${\lambda }_D$ is the Debye length and $r_c$ is the cyclotron radius. The dominant transport mechanism is the exchange of energy associated with velocity components parallel to the magnetic field. For a thermal gradient scale length $L_T\gtrsim 100{\lambda }_D$, the energy exchange is dominated by interactions between particles separated by $O\left({\lambda }_D\right)$ and yields a thermal diffusivity $\chi \sim {\nu }_c{\lambda }_D^2$, where ${\nu }_c=n\overline{v}{b}^2$ is the collision frequency. The diffusivity is even larger for larger $L_T$, where the energy exchange is dominated by the emission and absorption of plasma waves.