The Sun as a MHD generator: application of a new heating mechanism for the coronal loops and closed magnetic structures

Joule Physics Laboratory, Institute for Materials Research, School of Computing, Science and Engineering, University of Salford, Salford, Greater Manchester, M5 4WT, UK

Received: 31 March 2005
Accepted: 7 June 2005

Abstract

We investigate the possibility of heating of the loops and other closed magnetic structures in active regions of the solar corona by the flow of solar wind (plus other flows that may be present) across the magnetic field lines (that are perpendicular to the flow), in a similar manner to a conventional MHD generator. A simple model is formulated which allows us to calculate the typical currents generated by this mechanism. This enables us to make a judgement as to whether the loops in solar active regions can be heated by the proposed mechanism through the associated Ohmic dissipation. It is shown that even if the heating region width is of the order of a few proton Larmor radii (this effectively means that a loop is represented by nano-threads, by analogy with the nano-flare coronal heating mechanism, with width of a few proton Larmor radii) and the plasma flow speed is 50 km s^-1 then only about 1% of the heating requirement of coronal loops could be met under this conjecture. Other implications of the model, such as a predicted spatial heat distribution along the loop as well as application of the model to the other places e.g. chromosphere and corotating interaction region structures in the solar wind are discussed.