The impact of intense fluxes of energetic protons on the low-latitude ionosphere

Experiments on board low-Earth orbit satellites show that energetic particles (tens of keV) of the Earth’s radiation belt can penetrate to the equatorial ionosphere. Impact of the energetic particles on the upper atmosphere and ionosphere was studied for the case of the geomagnetic storm on 22 July 2009. We present changes of local ion concentration in the low-latitude ionosphere at night measured by the C/NOFS satellite at heights 400-800 km during the magnetic storm and quiet days. The ionospheric density during the storm was compared with a simultaneous observation of enhancements of 30-80 keV proton fluxes measured by the NOAA/POES satellites near the equator at height ~850 km. We suggest that ionospheric irregularities at night can be caused by effect of energetic protons.