Coronal Heating By Forced Magnetic Reconnection
G. Vekstein and N. Bian
Although it is now generally accepted that magnetic reconnection is responsible for coronal heating as well as for various other manifestations of the solar coronal activity
(flares, mass ejections, etc), many important details of these processes are still poorly understood. Therefore, clarifying them is one of the major scientific objectives of the upcoming Solar-B mission.
A likely scenario of explosive events in the solar atmosphere looks as follows. The photospheric convection shuffles footpoints of coronal magnetic loops, causing in this way continuous deformation of the coronal magnetic field. In response, regions of high electric currents (current sheets) readily form within the corona. Then, even a very small electric resistivity, which is typical for hot coronal plasma, leads to fast current sheets dissipation, thus bringing about magnetic reconnection and efficient release of an excess magnetic energy accumulated in the corona.
This type of reconnection, which is not due to an intrinsic plasma instability such as the tearing mode, but is triggered by some external perturbation, is generally called `forced reconnection'. The latter is of significant importance for the solar corona, since even a weak external perturbation can cause a substantial magnetic relaxation. Here we demonstrate this by considering two particular models of forced magnetic reconnection. The first one, which deals with a sheared force-free magnetic field, is relevant to coronal reconnection triggered by emerging new magnetic flux. The second model studies forced reconnection at a neutral magnetic X-point.
Correspondence
Grisha Vekstein (g.vekstein@manchester.ac.uk), School of Physics and Astronomy, The University of Manchester, United Kingdom
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