Temporal variation of particle precipitation in Erath's polar cap from DMSP observations

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 Earth's polar cap region, which is also an open-field line region as the cusp. In many numerical simulations of the upper atmosphere, the polar cap region is described as a uniform area with no spatial and temporal variations of the particle energy and fluxes. We analyze years of the particle observations from DMSP satellites to show the temporal variations of particle characteristics in the region poleward of 80 degree magnetic latitudes in this study. The results show the solar cycle, annual and seasonal variations of particle (electrons, ions) energy, number flux and energy flux in the polar cap. The results will be useful to improve the polar-latitude precipitating particle description in upper atmosphere modeling.