EUV blinkers: The significance of variations in the extreme ultraviolet quiet sun

A search for microflare activity in the extreme ultraviolet (EUV) quiet Sun using the Coronal Diagnostic Spectrometer (CDS) aboard the Solar and Heliospheric Observatory (SOHO) spacecraft has not resulted in the identification of microflare activity, but has resulted in the identification of a hitherto unknown phenomenon: enhancements of a factor of 2-3 in the flux of transition region lines at network junctions. A total of some 6 hours of observation of 5 different target areas showed this 'blinker' activity at each area, with durations ranging from 1 to 30 min and averaging 13 min, and thermal energy content of order 10(-6) that of a 'standard' flare. Assuming that the observations are of typical quiet Sun, and projecting these data to predict a distribution of these events over the entire Sun, the total thermal energy content of these 'blinkers' is insignificant when compared to the energy required to heat the corona. The nature of these events and their significance are discussed in this paper.