Nanoflare Theory and Stochastic Reconnection

Local magnetic reversals are an inseparable part of magnetohydrodynamic turbulence whose collective outcome may lead to a global reconnection with a rate independent of the small scale physics—stochastic reconnection. We show that this picture is related to the nanoflare theory, which is one of the most plausible models to solve the coronal heating problem. The magnetic field follows the turbulent flow in a statistical sense by means of stochastic flux freezing. Hence the turbulence, which bends and stretches the initially smooth field, will tend to increase the field’s spatial complexity. Strong magnetic shears associated with such a highly tangled field can trigger local reversals and field annihilations on a wide range of inertial scales, which convert magnetic energy into kinetic and thermal energy respectively. The former enhances the turbulence while the latter enhances heat generation on any inertial scale. These theoretical predictions are supported by scaling laws and simulations.