Transition Region Blinkers – I. Quiet-Sun Properties

Abstract

An automated method of identifying transition region blinkers is presented. The distribution and general properties of blinkers identified in the quiet Sun are discussed. The blinkers are seen most clearly in the O v (629 A) transition region emission line, but they also have strong signatures in O iv (554 A), and the chromospheric line, He i (584 A). The strongest O v blinkers can also be identified in O iii (599 A). No significant signatures are found for blinkers in the Mg ix (368 A) and Mg x (624 A) coronal lines. A few hundred O v blinkers are analyzed. Their global frequency is between 1 and 20 s−1 depending on how significant the peaks of the blinkers are. They have a typical area of 3×107 km2, a typical lifetime of 16 min and a typical intensity enhancement factor of 1.8. We find the ratios of the oxygen lines to be flat confirming the result that blinkers are not temperature events, but are density enhancements or due to increases in filling factor. Blinkers are found to occur preferentially over regions of enhanced chromospheric or transition region emission such as network boundaries, however, it is not so clear that they appear below the brightest coronal regions. A rough analysis of the magnetic fragments show that blinkers preferentially occur above regions where there are large or strong magnetic fragments with 75% occurring in regions where one polarity dominates.