Some characteristics of atmospheric gravity waves observed by radio-interferometry

Abstract. Observations of atmospheric acoustic-gravity waves (AGWs) are considered through their effect on the horizontal gradient G of the slant total electron content (slant TEC), which can be directly obtained from two-dimensional radio-interferometric observations of cosmic radio-sources with the Nançay radioheligraph (2.2^°E, 47.3^°N). Azimuths of propagation can be deduced (modulo 180^°). The total database amounts to about 800 h of observations at various elevations, local time and seasons. The main results are:

a) AGWs are partially directive, confirming our previous results.

b) The propagation azimuths considered globally are widely scattered with a preference towards the south.

c) They show a bimodal time distribution with preferential directions towards the SE during daytime and towards the SW during night-time (rather than a clockwise rotation as reported by previous authors).

d) The periods are scattered but are larger during night-time than during daytime by about 60%.

e) The effects observed with the solar radio-sources are significantly stronger than with other radio-sources (particularly at higher elevations), showing the role of the geometry in line of sight-integrated observations.