Coronal heating and nanoflares: current sheet formation and heating

School of Mathematics and Statistics, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9SS, UK
e-mail: ruthc@mcs.st-andrews.ac.uk

Received: 4 February 2011
Accepted: 14 November 2013

Abstract

Aims. Solar photospheric footpoint motions can produce strong, localised currents in the corona. A detailed understanding of the formation process and the resulting heating is important in modelling nanoflares, as a mechanism for heating the solar corona.

Methods. A 3D MHD simulation is described in which an initially straight magnetic field is sheared in two directions. Grid resolutions up to 512³ were used and two boundary drivers were considered; one where the boundaries are continuously driven and one where the driving is switched off once a current layer is formed.

Results. For both drivers a twisted current layer is formed. After a long time we see that, when the boundary driving has been switched off, the system relaxes towards a lower energy equilibrium. For the driver which continuously shears the magnetic field we see a repeating cycle of strong current structures forming, fragmenting and decreasing in magnitude and then building up again. Realistic coronal temperatures are obtained.