Characteristics of particle precipitation in the polar cap region

Abstract:

Previous observations and simulations have shown that the low-energy electron precipitation in the cusp plays an important role in ionosphere and thermosphere through particle impact ionization and heating. In this study, we investigate the precipitating particles in the polar cap region, which is also an open-field line region as the cusp. In most numerical modeling of the upper atmosphere, the polar cap region is described as a uniform area with little variation in the particle energy and fluxes. We analyze the particle observations from DMSP satellites to show the spatial and temporal variations of particle characteristics in the region poleward of 80 degree magnetic latitudes. The results illustrate the spatial distribution of particle energy, number flux and energy flux in the polar cap, and also demonstrate their hemispheric asymmetry, annual and seasonal variations. In addition, the particle characteristics under different solar wind conditions are also investigated. The results will be useful to improve the polar-latitude precipitating particle description in upper atmosphere modeling.