Collisionless Kinetic Theory Research Articles

An equilibrium model of plasmaspheric composition and density

We have constructed a model of plasmaspheric composition and density in the region bounded by the 500‐km altitude level and by the dipole field line L = 5. We first discuss the collisionless kinetic theory model of quasi‐neutral plasma distributions along a dipole field line under the gravitation field, the ambipolar diffusion electric field and the inhomogeneous magnetic field. A simpler fluid‐equation model of the plasma distribution under the influence of the above force fields is shown to be able to incorporate effects of plasmasphere thermal structure. With O+, H+, and He+ densities at 500 km as input boundary values and with a phenomenological thermal structure of the plasmasphere abstracted from Ogo 5, Prognoz, and S3‐3 satellite data, we show that the plasma density distributions in the fluid‐equation model are consistent with the densities derived from in situ satellite measurements and from whistler observations, both in the topside ionosphere and in the outer plasmasphere.