| 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. |