A Study of the African 'Chimney' Region with Schumann Resonance Methods

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This grant supports continuing research on the interpretation of Schumann Resonance observations at several sites around the globe. The surface of the planet Earth and the ionosphere that surrounds it constitute a spherical capacitor, which serves as a resonant cavity for extremely low-frequency electromagnetic waves. The amplitude of the fundamental mode (about 8 Hz) is related to world-wide lightning activity. Observations of the Schumann Resonances (SR) at a given location reveal a background signal on which are superimposed transients caused by intense thunderstorms. The three main regions of global lightning activity are tropical Africa, tropical South America, and Indonesia. This work focuses on lightning in the first of these regions, the African convective or "chimney" zone. Observations at the SR field station in Rhode Island indicate a four-to-five day periodicity in lightning activity over Africa. Two possible explanations of this periodicity are African easterly waves or the global 5-day wave. One objective of the program is to analyze the SR data and supporting observations from satellites, rainfall observations, and global weather maps, to determine the cause of the periodicity. Another objective is to explain the apparent tendency for lightning to have positive polarity over the African continent and negative polarity offshore over the Atlantic Ocean.