On solar coronal heating

Abstract

We review heating of solar corona by magnetic fields/currents. Our emphasis is on micro- and nano-flares. In case of a microflare the energy release is ~1026 ergs whereas in a nanoflare ~1023 - 1025 ergs of energy is released. Flares have a distribution law over total radiated energy with exponent α = 1.8. Extending the same power law to micro-and nano-flares and assuming that they constitute a dominant heating mechanism for solar corona ??must be greater than 2. Many investigations lead to α < 2 whereas a few yield α > 2. The verdict remains inconclusive. More observational analyses and numerical simulations are needed to discriminate between the two cases.