Determination of the ionospheric transmission loss of the low frequency EM waves by simultaneous measurements of satellite and ground-based experiments

摘要

Propagation characteristics of the low frequency electromagnetic waves in the ionosphere are experimentally derived using simultaneous measurements of electromagnetic waves from intensive lightning by French DEMETER satellite and ground-based observations. The transient waveforms generated by worldwide intensive lightning in ELF range are continuously monitored by multi-component measurements in Moshiri, Hokkaido, Japan. Corresponding lightning locations and their electric properties are also derived from the ELF measurement whilst the low altitude satellite (DEMETER) successfully detects electromagnetic pulses over the same lightning sources penetrated through the ionosphere. Direct comparison of ELF transient waves observed by the satellite with the ground experiment gives the unique opportunity to derive the experimental ionospheric property such as an ionospheric transmission loss. The ionospheric transmission loss is obtained for different latitudes and local times by calculating Poynting flux at the lightning and above the ionosphere, and these results are compared with the theoretical calculations by using full-wave numerical method. As a result, the ionospheric penetration loss increases with decreasing the magnetic latitude and with increasing wave frequency. The penetration loss is much larger in daytime rather than night time. The experimentally obtained results are in good agreement with those from theoretical calculations.