Satellite observations of lightning-induced hard X-ray flux enhancements in the conjugate region

Abstract. Preliminary examination of October-December 2002 SONG (SOlar Neutron and Gamma rays) data aboard the Russian CORONAS-F (Complex Orbital Near-Earth Observations of the Activity of the Sun) low-altitude satellite has revealed many X-ray enhanced emissions (30–500 keV) in the slot region (L ~ 2–3) between the Earth's radiation belts. In one case, CORONAS-F data were analyzed when the intense hard X-ray emissions were seen westward of the South Atlantic Anomaly in a rather wide L shell range from 1.7 to 2.6. Enhanced fluxes observed on day 316 (12 November) were most likely associated with a Major Severe Weather Outbreak in Eastern USA, producing extensive lightning flashes, as was documented by simultaneous optical observations from space. We propose that whistler mode signals from these lightning discharges cause precipitation of energetic electrons from terrestrial trapped radiation belts, which, in turn, produce atmospheric X-rays in the Southern Hemisphere.