Detection of acoustic-gravity waves in lower ionosphere by VLF radio waves

摘要

We present a new method to study harmonic waves in the low ionosphere (60 -90 km) by detecting their effects on reflection of very low frequency (VLF)radio waves. Our procedure is based on amplitude analysis of reflected VLFradio waves recorded in real time, which yields an insight into the dynamics ofthe ionosphere at heights where VLF radio waves are being reflected. The methodwas applied to perturbations induced by the solar terminator motions atsunrises and sunsets. The obtained results show that typical perturbationfrequencies found to exist in higher regions of the atmosphere are also presentin the lower ionosphere, which indicates a global nature of the consideredoscillations. In our model atmosphere, they turn out to be the acoustic andgravity waves with comparatively short and long periods, respectively.