Solar activity cycle during classical antiquity

Abstract

Early accounts of phenomena that may be identified as auroral displays have been abstracted from reports of unusual celestial prodigies in the classical literature. An extensive catalog of ancient aurorae and a new mathematical method of analyzing fragmentary time series of observations have been used to demonstrate, provisionally, that an auroral cycle actually existed in antiquity, at least during the 2nd century BC, and that it had an average length and amplitude comparable with those of the modern auroral cycle. On the reasonable supposition that solar activity has always been the factor responsible for aurorae, it can be concluded that the solar cycle two millennia ago was very similar to what it is today.