Evaluating parameters of conductivity profile of the lower ionosphere by tweek-atmospherics

摘要

A method of determining the effective heights of the Earth-ionosphere waveguide for basic and higher types of normal waves (modes) and the distance to the radiation source – lightning is investigated by analyzing pulse signals in the range of extremely-low (ELF) and very low frequency (VLF) – tweek-atmospherics (tweeks). The resulted from analysis of multimode tweeks dependence of the effective height of the waveguide on the frequency is used for determining the parameters of the lower ionosphere conductivity profile. In computer simulations, waveforms of tweeks were synthesized in the frame of the Earth-ionosphere waveguide model with an exponential conductivity profile of the lower ionosphere. For the separation and analysis of individual waveguide modes in the signal the dynamic spectra of tweeks are used. The error in determining the effective height of the waveguide for different waveguide modes was 0.2…0.4 km, allowing estimating the parameters of the exponential conductivity profile of the lower ionosphere in the range of values typical for night conditions. Systematic and random error in determining the distance to the lightning were 10…40 km and 20…80 km, respectively, in the range of distances of 500…3000 km.