Correlated oscillations due to similar multi-path effects seen in two   widely separated radio telescopes
  A multipath mechanism similar to that used in Australia sixty years ago by the Sea-cliff Interferometer is shown to generate correlations between the periods of oscillations observed by two distant radio telescopes pointed to the Sun. The oscillations are the result of interferences between the direct wave detected in the main antenna lobe and its reflection on ground detected in a side lobe. A model is made of such oscillations in the case of two observatories located at equal longitudes and opposite tropical latitudes, respectively in Ha Noi (Viet Nam) and Learmonth (Australia), where similar radio telescopes are operated at 1.4 GHz. Simple specular reflection from ground is found to give a good description of the observed oscillations and to explain correlations that had been previously observed and for which no satisfactory interpretation, instrumental or other, had been found. 
P.N. Diep, N.T. Phuong, P. Darriulat, P.T. Nhung, P.T. Anh, P.N. Dong,   D.T. Hoai and N.T. Thao
astro-ph.IM astro-ph.SR