Seasonal dependence of energetic electron precipitation: Evidence for a global role of lightning

Analysis of the DEMETER spacecraft particle precipitation data shows that energetic electron fluxes exhibit a seasonal dependence consistent with lighting-induced electron precipitation (LEP). For the first time monthly averages over three years of energetic electron data observed on the low altitude DEMETER satellite are presented. Over the United States, energetic electron fluxes in the slot region (between L = 2 and 3) are significantly higher in the northern summer than in the winter, consistent with the seasonal variation of lightning activity in the Northern Hemisphere. The association of precipitating fluxes with lightning is explored using lightning location data from the National Lightning Detection Network (NLDN) and VLF wave data on DEMETER. The increased precipitation of particles into the drift loss cone over the Northern Hemisphere in summer is consistent with expected pitch-angle scattering by non-ducted whistlers, indicating that lightning is a significant contributor to the loss of slot region electrons.