Diffusion correction and thermal diffusion factors of ions in the ionosphere and plasmasphere Original Research Article

Diffusion equations determining ion diffusion velocities along magnetic field lines in the multicomponent ionosphere and plasmasphere composed of ions, electrons, and neutral species are derived from Grad’s 13-moment equations for average species velocities and heat flows. The general expressions for thermal diffusion and diffusion correction factors of an ion are simplified for the following cases of a multicomponent partially ionized plasma: (1) a major ion, a minor ion, electrons, and neutral species; (2) three major O+, H+, and He+ ions, electrons, and neutral species; (3) two major O+ and H+ ions, a minor ion, electrons, and neutral species. The ion thermal diffusion and diffusion correction factors calculated for O+, H+, and He+ ions of a fully ionized plasma are approximated by the analytical formulas as functions of [O+]/[H+] while changing the ratio of [He+] to ([O+] + [H+] + [He+]) between 0.01 and 0.9. A fully ionized plasma composed of two major ion species, O+ and H+, electrons, and a minor ion component, x, where x stands for NO+, image, N+, O++, N++, Fe+, Mg+, Na+, Ca+, Al+, and Si+ is considered to calculate the thermal diffusion and diffusion correction factors of each minor ion. Analytical approximating relationships of these thermal diffusion and diffusion correction factors with the [O+]/[H+] ratio are presented for use in ionospheric models.