If the mechanism responsible for creating the high-temperature solar corona is a magnetic one, the resulting coronal heating events are likely to be highly sporadic and fragmented. Therefore, nanoflare heating, where both these features are present, by the very meaning of the concept, is a strong candidate. The major problem is how to test this theory while individual nanoflares remain beyond observational recognition. Here, we discuss a possibility of probing the nanoflare heating scenario by considering statistical characteristics of coronal active regions, which presumably originate from a large number of random impulsive heating events. This approach allows one to derive various parameters of x-ray coronal loops (temperature, emission measure, filling factor, etc) without specifying particular details of the heating events. How the energy of individual nanoflares can be estimated from observed fluctuations in the coronal x-ray emission is also discussed. Comparison of our results with recently reported analysis of small fluctuations of coronal x-ray intensity observed with Yohkoh SXT telescope yields an estimate of (1022–1023) erg for the energy of nanoflares in the active region.
Globally propagating waves in the solar corona