A study of the unification of quiet-Sun transient-event phenomena

¹ Space Science and Technology Dept., Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, England, and Honorary Visiting Professor, School of Mathematics and Statistics, the University of St Andrews, UK
² Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking Surrey RH5 6NT, UK
³ Kiepenheuer-Institut für Sonnenphysik, 79104-Freiburg, Germany
⁴ School of Mathematics and Statistics, The University of St Andrews, St Andrews, Fife KY16 9SS, UK

Corresponding author: R. A. Harrison, r.harrison@rl.ac.uk

Received: 2 December 2002
Accepted: 9 July 2003

Abstract

A number of small-scale, globally distributed solar transient event-types have been reported in the literature. Their potential role in fundamental processes in the solar atmosphere, such as coronal heating and wind acceleration, is under active investigation. However, the event-types, such as those known as blinkers, explosive events, EUV (extreme-UV) network and cell brightenings, network flares, heating events, nanoflares and EUV brightenings are basically classifications which are driven to a large extent by different observational techniques and different instruments rather than the identification of a clear differing physical phenomenon. We investigate the different instrumental and technique limitations and attempt to identify any unification of the reported quiet-Sun transient, small-scale phenomena. We find that once observational techniques have been considered, a number of the different classifications appear to be the same. This suggests that events known as blinkers, network and cell brightenings and EUV brightenings are the same event-type. We suggest that the term blinker be used as a generic term to describe these events. However, there appears to be little evidence that blinkers and explosive events are directly related. Furthermore, although a small percentage of blinkers and nanoflares/heating events appear to be related to one another, these events pose a number of important questions suggesting that either (i) blinkers and nanoflare/heating events are all created by the same mechanism, i.e. for some blinker events, the conditions are such that higher temperatures are found, or (ii) there are two types of event, including the “traditional” blinker which is effectively a transition region brightening driven by a density or filling factor enhancement, and a mini-flare-like event which reaches higher temperatures, presumably driven by reconnection.