Energetic electron precipitation from the outer radiation belt during geomagnetic storms

first_imgRelativistic electron precipitation changes thechemistry of the upper atmosphere and depletes ozone,but the spatial and temporal distributions are poorly known.Here we survey more than 9 years of data from low altitudesatellites for different phases of geomagnetic storms. Wefind that for the outer radiation belt, electron precipitation>300 keV peaks during the main phase of storms whereasthat >1 MeV peaks during the recovery phase. Precipitation>300 keV can occur at all geographic longitudes in bothhemispheres whereas that >1 MeV occurs mainly polewardof the South Atlantic anomaly (SAA) region. The datasuggest that wave-particle interactions are strong enough toprecipitate >300 keV electrons into the bounce loss cone,but precipitate >1 MeVelectrons into the drift loss cone. Wefind that whistler mode chorus waves alone cannot accountfor the higher MeV precipitation flux during the recoveryphase. We suggest that whistler mode chorus wavesaccelerate electrons up to MeV energies during therecovery phase which are then precipitated by EMICwaves. The effects on atmospheric chemistry due to MeVelectron precipitation are more likely to occur in thesouthern hemisphere poleward of the SAA region with adelay of 1–2 days or more from the peak of the storm.Citation: Horne, R. B., M. M. Lam, and J. C. Green (2009),Energetic electron precipitation from the outer radiation beltduring geomagnetic storms, Geophys. Res. Lett., 36, L19104,doi:10.1029/2009GL040236.last_img read more