On the influence of the Sun on the rapid variability of compact   extragalactic sources
  Starting from December 2004, a program for the monitoring of intraday variable sources at a frequency of 5 GHz was performed at the Urumqi Observatory. The analysis of the variability characteristics of the flat-spectrum radio source AO 0235+164 revealed the existence of an annual cycle in the variability amplitude. This appears to correlate with the solar elongation of the source. A thorough analysis of the results of the MASIV IDV survey --- which provides the variability characteristics of a large sample of compact radio sources --- confirms that there is a small but detectable component of the observed fractional modulation which increases with decreasing solar elongation. We discuss the hypothesis that the phenomenon is related to interplanetary scintillation. 
N. Marchili, T. P. Krichbaum, X. Liu, H.-G. Song, J. M. Anderson, A.   Witzel and J. A. Zensus
astro-ph.SR astro-ph.CO