ELF Resonance Line-Splitting in the Earth-Ionosphere Cavity

Abstract

At extremely low frequencies (ELF), the resonances in the spherical shell between the earth and the ionosphere are excited by natural thunderstorm activity. The frequencies of resonance are determined by the dimensions of the cavity and the conductivities of the earth and the ionosphere. Pronounced resonance ‘mode splitting’ has been observed during periods of high solar activity. After a detailed statistical analysis of ELF data recorded at University of Rhode Island, USA and relevant geo-physical parameters during a major solar event (August, 1972), very significant correlation was found between observation of ‘split’ resonance peaks and maxima of solar proton flux. Results of the statistical analysis have shown that the resonance line splitting is directly related to the enhancement of the solar proton flux and thereby increased ionization in the D-region of the ionosphere.

Indexing Terms:

• ELF Propagation
• Ionospheric Propagation
• Cavity Resonances