Take a look at this:
http://news.stanford.edu/news/2010/august/sun-082310.html
A correspondent suggested that the effect may not be clear - see these:
3 attachments — Download all attachments (zipped for English (US))
Evidence against correlations between nuclear decay rates and Earth–Sun distance.pdf
Evidence for Correlations Between Nuclear Decay Rates and Earth-Sun Distance.pdf
Perturbation of Nuclear Decay Rates During the Solar Flare of 13 December 2006.pdf