Sprite-Producing Lightning-Ionosphere Coupling and Associated Low-Frequency Phenomena

Theoretical and experimental evidence is collected for additional ionization regions in the mesosphere above lightning discharges and their connection with transient luminous events (TLE). New insights are reported into the different appearances in the Very Low Frequency (VLF) link traces as affected by the mesospheric ionization regions. Based on these findings, physical processes going on in the ionization regions and their coupling to the primary lightning discharge process are conceptualized. Thereafter, some diagnostic potential is outlined. Finally, the ionization regions are considered as a transmitter of secondary low-frequency waves. The distinction is made between the primary electromagnetic waves emitted by the lightning and the secondary waves. As a consequence the Extremely Low Frequency (ELF) and Ultra Low Frequency (ULF) transient signatures observed on the ground are understood as a composite of both wave types. In addition a novel method is introduced to extract the charge moment change of a sprite producing lightning discharge.