Thunderstorm-related variations in the sporadic E layer around Rome

Abstract

Superposed epoch analysis (SEA) was used to study possibly statistically significant variations of the critical frequency (foEs) and virtual height (h’Es) of the sporadic E layer (Es) related to thunderstorm activity generated in the troposphere. The reference time for the SEA was the time of lightning strokes measured by theWorldWide Lightning Location Network at the ionosonde station of Rome (41.9◦N, 12.5◦E) during the year 2009. The results obtained reveal that: (a) a statistically significant decrease of foEs after the time of lightnings has been found for time windows of ±100 h; (b) the effects of thunderstorms on the ionosphere is larger when the thunderstorm approaches from the opposite direction to the mean neutral stratosphere–mesosphere wind flow; (c). a statistically significant decrease of foEs related to thunderstorms during nighttime was observed. No significant changes in foEs and hEs over the seasonal time scale as well as in the latter parameter in the three (a–c) cases related to thunderstorms.