A Theoretical Study of the High Latitude \u3ci\u3eF\u3c/i\u3e region’s Response to Magnetospheric Storm Inputs

The response of the polar ionosphere to magnetospheric storm inputs was modeled. During the storm the two major processes that couple the F region to the magnetosphere, namely the electric field distribution and the particle precipitation from the magnetosphere, undergo drastic modification on relatively short F region time scales. These time-dependent changes are not simply related to the F region storm time dependent changes. The lower F region responds on a time scale of only minutes to the storm associated changes in the auroral precipitating electron flux, owing to the dominance of chemistry production-loss mechanisms over transport processes. At higher altitudes in the vicinity of hmF2, the chemistry is balanced by both plasma diffusion along field lines and horizontal plasma convection, which acts to prolong the effect of the storm for many hours after it has ceased. The peak density responds only slowly to increased precipitation and may not reach its maximum enhanced value until over an hour after the storm main precipitation has passed. However, the F region peak can be drastically altered on a time scale of minutes if large vertical transport velocities are associated with the storm electric field distribution. In the topside ionosphere the density variations are not correlated with the morphology of the storm auroral precipitation or the temporal variation of the storm electric field pattern. Time delays of up to 3 or 4 hours occur at high altitudes for ‘peak’ densities to be reached after a storm, and the subsequent recovery is on the order of 5 hours. These long delays at altitudes above 400 km reflect the long time constants associated with plasma diffusion from low altitudes, where the plasma is created, to high altitudes