Lightning-induced electron precipitation: Statistical analysis of DEMETER satellite data and WWLLN lightning locations

We experimentally analyze the importance of lightning-generated whistlers for electron precipitation from the Van Allen radiation belts. For this purpose, we use the wave and energetic particle data measured by the low-altitude DEMETER spacecraft between 2006 and 2010, complemented by the lightning locations and times obtained by the World Wide Lightning Location Network (WWLLN). We focus on the region above the United States (L-shells between 2 and 3, geomagnetic longitudes between 300 and 360 degrees). This region exhibits a significant difference in the number of lightning between the local summer and winter, allowing us to contrast the two seasons. Additionally, it is located westward of the South Atlantic Anomaly, i.e., the drift loss cone has not yet been emptied, and there are many particles with pitch angles not too far from the bounce loss cone. We show that during the northern summer, when the number of lightning in the region increases tremendously, there is a considerable increase in both the VLF wave intensity and the precipitating energetic electron flux. We perform a correlation analysis to determine the most affected energy range. It also reveals that the effect is more pronounced during the night than during the day, in agreement with the lower wave attenuation in the ionosphere, and it is more pronounced during periods of low geomagnetic activity compared to those of high geomagnetic activity.