Modeling the ionospheric effects of ion and electron precipitation in the cusp

The effect of increased ion production due to the precipitation of both ion s and electrons in the cusp region has been studied using a computational m odel of the high-latitude ionosphere. The modeling assumes that the cusp re gion is subject to fluxes of precipitating electrons which have a Maxwellia n energy distribution at a temperature of 50 eV. In addition to the electro ns the modeled cusp ionosphere is also subjected to precipitating ions with a Maxwellian energy distribution, at a temperature of 500 eV and a "low en ergy cutoff" for ions with an energy less than 900 eV. The results reveal b oth ion and electron precipitation to be important production sources in th e cusp region, but at markedly different altitudes. Electron precipitation produces dominant effects at F2 peak altitudes of around 300 km while the i ons, at higher energies, are capable of creating a precipitation "F1 ledge" at altitudes of around 150 km. A simulation of the ion dispersion with lat itude, known as the "velocity filter effect," reveals that this leads to la rge enhancements in lower-altitude electron concentration on the equatorwar d edge of the cusp, the enhancement tailing off sharply in latitude.