The Influence of the Asymmetric Ionosphere on the Schumann Resonances

Abstract:

The asymmetric ionosphere is known to affect the behavior of the Earth’s Schumann resonances (SR). Several studies have addressed the day-night asymmetry with observation or simulation and showed the contrast in SR amplitude between day and night (Satori et.al 2007, Pechony and Price 2007, Yang et.al., 2006). And distinct perturbations in the ionosphere caused by solar proton events, x-ray emission and earthquake coupling will also produce variations in SRs (Roldugin et.al., 2004, De et al., 2010; Satori et.al., 2015). Considering all these possible variations produced by changes in ionospheric asymmetry, we simulate the SR propagation in an asymmetric cavity including the day-night contribution and the more general perturbation asymmetry using a TDTE (Two Dimensional Telegraph Equation) approach. The change of source position in the asymmetric ionosphere and the size of the perturbation will also affect the SR parameters such as amplitude and modal frequency. The central location of the source in either the daytime or nighttime zone will produce a larger amplitude than other locations in the cavity. For example, the amplitude from a source in the zone with lower electric height (like the daytime region) is larger than the situation with source in region of larger electric height (like nighttime region). The asymmetry(difference on EM amplitude between two regions) will be more distinct when the source is on the terminator between two region than on other position. And when the size of the asymmetric construction is changed, the amplitude and modal frequency will also be changed. The increased size of the zone with lower electric height will produce larger SR amplitudes and decreased modal frequency.