Schumann resonances and electrical conductivity of the atmospher and lower ionosphere—I. Effects of conductivity at various altitudes on resonance frequencies and attenuation

Abstract

Three realistic, continuous ionospheric conductivity profiles and an idealized model of the ionosphere, consisting of three discrete layers, are used to investigate the effects of conductivity at altitudes from ground level to 100 km upon the Schumann resonance frequencies and ELF attenuation. The ultimate objective is to infer a conductivity profile from resonance frequencies and cavity Q measured at ground level which will be done in Part II. In Part I it is shown that the dominant effects are due to the region between roughly 40 km and 60 km where the ratio of conduction current to displacement current is 0.01 ≲ [ σ/( ωϵ 0)] ≲ 40. A finite average conductivity σ a of the atmosphere below approximately 40 km altitude must be considered for accurate evaluation of wave attenuation or cavity Q. Variations in σ a can have the same effect upon attenuation as possible changes in ionospheric conductivity in the 70–80 km altitude range.