Source, propagation, and effects of lightning in the Earth-ionosphere system
Hutchins, Michael Lawrence
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The capabilities of the World Wide Lightning Location Network (WWLLN) are expanded to enable research of the source, propagation, and effects of lightning in the Earth-ionosphere system. The main expansion of the network capability is the measurement of the very low frequency radiated energy from lightning; the radiated stroke energy is one to one related to the canonical peak current measurements of other ground based networks. Stroke energy is used to develop a model of the network relative detection efficiency; this internal model rates the coverage capabilities of the network compared to the networks best regional coverage. The last dataset developed and discussed is the clustering of the lightning locations into both flashes and the active lightning regions of thunderstorms. These three capabilities of the network allow tracing the effects of lightning and thunderstorms from their source, to a proxy for the global electric circuit and to the magnetosphere. The source of lightning is investigated in two regimes: within thunderstorms and between thunderstorms. Within thunderstorms the time between flashes is found to be proportional to the resulting flash energy for differing thunderstorms, regions, and seasons. Between thunderstorms the lightning energy is shown to differ between land and ocean, with oceanic thunderstorms producing stronger and fewer strokes. The propagation of the radiated energy is measured using the lightning as a probe of attenuation along the different propagation paths. Attenuation is seen to have an asymmetry with magnetic azimuth: eastward moving waves are attenuated less than westward moving waves. The attenuation asymmetry is complimentary to the observed asymmetry in whistler and radio energy emitted through the ionosphere into the magnetosphere. Thunderstorm clusters are used to estimate the total upward current contribution of thunderstorms to the global electric circuit. It is shown that WWLLN can provide one of the first continuous global measurements of this current to the global electric circuit.