Lightning and the sun — Science News, June 22, 1974
The latest addition to the growing list of meteorological phenomena which have been linked with solar activity is lightning…. Using data from 1930 to 1973, [a researcher] reports in the May 24 Nature that “in spite of year-to-year variations in the incidence of lightning, there is an underlying cyclic variation with a period of about 11 years which is in phase with the solar cycle.”