STATISTICAL ANALYSIS OF THE ENERGY DISTRIBUTION OF NANOFLARES IN THE QUIET SUN

摘要

For many years it has been debated whether the quiet solar corona is heated by nanoflares and micro- flares or by magnetic waves. In this paper TRACE data 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 events and their energy. We find that gamma is highly dependent on the form of the line-of sight depth assumed to determine the event energies. If a constant line-of sight depth is assumed, then y 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. is event area and k is a constant, then gamma lies between 2.0 and 2.1. In all cases the value of y is greater than 2 and therefore implies that the events with the lowest energies dominate the heating of the quiet solar corona. Moreover, there are strong indications that there is insufficient energy from events with nanoflare energies (i.e., energies in the range 10~24-l0~27 ergs) to explain the total energy losses in the quiet corona. However, our results do not rule out the possi- bility that events with 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 magnetic fields. Indeed, just 16/100 of the quiet corona possesses such events.