Wavelet characterisation of ionospheric acoustic and gravity waves occurring during the solar eclipse of August 11, 1999

We propose here a wavelet-based detection and characterisation of the propagation of acoustic-gravity waves induced in the ionosphere by the solar eclipse of August 11, 1999. The data are obtained from measurements of electron density profiles using (1 min vertical incidence) ionospheric sounding performed at Pruhonice (Czech Republic, 49.9N, 14.5E) and consist of the fluctuations of electron concentrations. The main goals of the current work are twofold. First, we describe in details the wavelet-based methodology used to detect and characterise acoustic and gravity waves and explain how and why this improves the previously proposed Fourier based approaches. Mainly, we show that wavelet transforms allow us to untangle waves that would be otherwise mixed up in Fourier decompositions. Second, we study carefully different waves and characterise them in terms of time of occurrence, period, wave vector, packet and phase velocities. We also demonstrate the existence of acoustic waves during the solar eclipse and characterise accurately. Such detections are made possible by the combined use of both data with a high sampling rate (1 min) and wavelet-based tools.