Theory of 3D reconnection and coronal heating

Magnetic reconnection is a prime candidate for heating coronae. We here summarise recent developments in the theory of 3D reconnection and the different ways in which it is thought to heat the solar corona. At 3D null points reconnection may occur by either spine, fan or separator reconnection. In absence of null points, reconnection of two flux tubes is completely different from 2D reconnection, since, in general in 3D a flux-conserving velocity w does not exist. Instead two flux tubes split into four parts, which 'flip' via 'virtual flux tubes' to form four flux tubes. Heating in the corona, has been proposed to occur by: driven reconnection at X-ray bright points; binary reconnection due to the coronal interaction of a pair of opposite-polarity magnetic sources; separator reconnection due to a higher-order interaction; braiding; and coronal tectonics due to the formation and dissipation of current sheets at myriads of separatix surfaces that thread the corona and separate the flux coming from the many different sources in the photosphere. (C) 2003 COSPAR. Published by Elsevier Ltd. All rights reserved.