Statistical analysis of the energy distribution of nanoflares in the quietSun

For many years it has been debated whether the quiet solar corona is heated by nanoflares and microflares or by magnetic waves. In this paper TRACE da ta of events with energies in the range 10(23)-10(26) ergs are investigated . A new stable and objective statistical technique is proposed to determine the index, -gamma, of a power-law relation between the frequency of the ev ents and their energy. We find that gamma is highly dependent on the form o f the line-of-sight depth assumed to determine the event energies. If a con stant line-of-sight depth is assumed, then gamma lies between 2.4 and 2.6; however, if a line-of-sight depth of the form (Ae(/)k(2))(1/2) is assumed, where A(e) is event area and k is a constant, then gamma lies between 2.0 a nd 2.1. In all cases the value of gamma is greater than 2 and therefore imp lies that the events with the lowest energies dominate the heating of the q uiet solar corona. Moreover, there are strong indications that there is ins ufficient energy from events with nanoflare energies (i.e., energies in the range 10(24)-10(27) ergs) to explain the total energy losses in the quiet corona. However, our results do not rule out the possibility that events wi th picoflare energies (i.e., energies in the range 10(21)-10(24) ergs) heat the quiet corona. From analysis of the spatial distribution of the events, we find that events are mainly confined to regions with the brightest EUV emission, which are presumably the regions connected to the strongest magne tic fields. Indeed, just 16% of the quiet corona possesses such events.