Prima facie evidence of the fast impact of a lightning stroke on the lower ionosphere

Abstract

Studies show that intense lightning discharges can perturb nighttime lower ionosphere through induced electromagnetic fields. We report here new evidence that every lightning stroke, regardless of intensity, has an impact on both daytime and nighttime lower ionosphere. Through analysis of thousands of negative cloud-to-ground lightning strokes in southern China, we find that skywave features of a lightning sferic are closely related to its source intensity. Variations with increasing lightning intensity show a higher reflectivity from nighttime ionosphere but a larger time delay from daytime ionosphere. It also shows that the ionosphere recovers from the lightning impact in a time shorter than tens of milliseconds. This suggests that there exists a direct and fast nonlinear coupling between lightning-generated electromagnetic fields and lower ionosphere, making the ionospheric response to a lightning stroke dependent of the lightning intensity. A candidate mechanism for this is the Joule heating effect, but it needs future studies.