Electrodynamic effects of lightning discharges on the ionosphere and the radiation belts

Understanding and quantification of the acceleration and loss processes for energetic electrons in the radiation belts is now a prime topic of interest for now-casting and forecasting of Space Weather. Although the loss processes for the electrons are fundamentally understood to be cyclotron resonant scattering by electromagnetci plasma waves, quantification of the losses are now most important than ever, since it is a prerequisite to the quantification (and therefore understanding) of the acceleration processes. Especially in the inner radiation belt and the slot region, recent results have brought to fore the potential role of electron precipitation losses driven by lightning-generated whistler waves. For electrons having energies >100 keV, ground-based methods involving subionospheric VLF measurements have proven to be an effective means of measuring bursts of precipitation driven by individual (discrete) whistler waves launched by lightning discharges. Such measurements allow a degree of quantification and cause-and-effect relationahips that are normally only realized in laboratory experiments. In this paper, we present recent measurements of lightning-induced electron precipitation, especially aimed at determining the relative roles of thunderstorm activity and geomagnetic activity in determining the rate of occurrence of observed events. Although lightning-whistler-induced electron precipitation is a form of upward/downward coupling of upper atmospheric regions, also discuss other forms of direct upward electrodynamic coupling driven by lightning discharges, leading to phenomena such as sprites, elves, and Terrestrial Gamma-ray Flashes.