Area of whistler penetration to the ionosphere

In our analysis, we processed data from 186 DEMETER passes over the European region and found 30,000 of pairs causative lightning-whistler. We find that mean whistler amplitude monotonically decreases with horizontal distance up to 1000 km from the lightning source. At larger distances, the mean whistler amplitude usually merges into the background noise and the whistlers become undetectable. The maximum of whistler intensities is shifted from the satellite magnetic footprint 1° owing to the oblique propagation. The average amplitude of whistlers increases with the lightning current. At nighttime (late evening), the average amplitude of whistlers is about three times higher than during the daytime (late morning) for the same lightning current.