Acoustic-gravity waves during solar eclipses: Detection and characterization using wavelet transforms

In the present contribution, we first propose a methodology that enables to detect wave-like structures propagating in ionosphere, by tracking the local maxima of the modulus of continuous complex wavelet transform coefficients with respect to heights. From the derivation of the phases of the wavelet transform, we measure the corresponding propagation parameters. These tools are applied to measurements collected by vertical ionospheric sounding at high-time resolution sampling regime (sampling periods ranged from 1 to 3 min) in the observatory Pruhonice (49.9N, 14.5E, Czech Republic). The aim of these experiments is to analyze the changes in the ionospheric plasma induced by three different solar eclipse events (total solar eclipses, I I August 1999, 29 March 2006, and annular solar eclipse, 3 October 2005) and to detect and analyze the propagation of the generated acoustic-gravity waves (AGWs). Second, injecting wave vector components measured from the data into the AGW propagation equations, we obtain a full description of the propagation of the waves. This enables us to differentiate AGWs from others wave-like oscillations and to discuss similarities and differences of the waves detected during these three particular events. These procedures also enabled us to detect acoustic waves. We believe that the methodology proposed here brings significant improvement in detecting and characterizing AGW propagations from empirical data and can be readily used in the ionosphere community. (C) 2007 Elsevier Ltd. All rights reserved.