Energy Distribution of Microevents in the Quiet Solar Corona

Recent imaging observations of EUV line emissions have shown evidence forfrequent flare-like events in a majority of the pixels in quiet regions of thesolar corona. The changes in coronal emission measure indicate impulsiveheating of new material to coronal temperatures. These heating or evaporationevents are candidate signatures of "nanoflares" or "microflares" proposed tointerpret the high temperature and the very existence of the corona. The energydistribution of these micro-events reported in the literature differ widely,and so do the estimates of their total energy input into the corona. Here weanalyze the assumptions of the different methods, compare them by using thesame data set and discuss their results. We also estimate the different forms of energy input and output, keeping inmind that the observed brightenings are most likely secondary phenomena. Arough estimate of the energy input observed by EIT on the SoHO satellite is ofthe order of 10% of the total radiative output in the same region. It isconsiderably smaller for the two reported TRACE observations. The discrepancycan be explained partially by different thresholds for flare detection. Thereis agreement on the slope and the absolute value of the distribution if thesame method were used and a numerical error corrected. The extrapolation of thepower law to unobserved energies that are many orders of magnitude smallerremains questionable. Nevertheless, these micro-events and unresolved smallerevents are currently the best source of information on the heating process ofthe corona