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

The effect of increased ion production due to the precipitation of both ions and electrons in the cusp region has been studied using a computational model of the high-latitude ionosphere. The modeling assumes that the cusp region is subject to fluxes of precipitating electrons which have a Maxwellian energy distribution at a temperature of 50 eV. In addition to the electrons the modeled cusp ionosphere is also subjected to precipitating ions with a Maxwellian energy distribution, at a temperature of 500 eV and a “low energy cutoff” for ions with an energy less than 900 eV. The results reveal both ion and electron precipitation to be important production sources in the cusp region, but at markedly different altitudes. Electron precipitation produces dominant effects at F2 peak altitudes of around 300 km while the ions, at higher energies, are capable of creating a precipitation “F1 ledge” at altitudes of around 150 km. A simulation of the ion dispersion with latitude, known as the “velocity filter effect,” reveals that this leads to large enhancements in lower-altitude electron concentration on the equatorward edge of the cusp, the enhancement tailing off sharply in latitude.

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