Illumination of mesospheric irregularity by lightning discharge

Abstract

Theoretical model calculations recently predicted the existence of mesospheric irregularities which assist the initiation of sprites. Here we report the experimental detection of a ∼3–19 km3 large mesospheric irregularity at ∼80–85 km height which is illuminated by the electromagnetic field of an intense positive cloud‐to‐ground lightning discharge. While the lightning discharge causes a prompt group of four sprites above the lightning discharge, the mesospheric irregularity is found at a horizontal distance at least ∼15–20 km away from the sprite group and it rebrightens ∼40–60 ms after the sprite group occurrence. This rebrightening is driven by a local quasi‐static electric field enhancement with a charge moment ∼4–20 Ckm which causes the irregularity to develop a downward descending luminous column from ∼75–85 km height. The quasi‐static electric field enhancement is caused by the reorganization of residual charge inside the thundercloud during a high‐level activity of intracloud discharges with ∼10–20 pulses per ms. Such mesospheric irregularities might have an effect on the wave propagation of 100 kHz radio waves which are used for atomic time transfer and marine navigation.