Magnetic topology during the reconnection process in a kinked coronal loop

The magnetic topology change that arises during the evolution of the kink instability in a solar coronal loop is studied using a three-dimensional MHD simulation in cylindrical geometry. The initial structure is an axisymmetric twisted magnetic flux tube carrying a vanishing axial electric current, that has primarily evolved towards a kinked configuration containing an intense current concentration along the loop. Consequently, the ensuing evolution becomes resistive allowing a stationnary reconnection process to occur (Baty 2000). The system finally reaches a relaxed configuration of lower magnetic energy with three topologically distinct regions. Indeed, the original highly twisted central region is transformed into two interwoven flux tubes with field lines having a small amount of twist within each tube. This first region is surrounded by a weakly non axisymmetric annular flux tube that is embedded into the original potential magnetic field. Using mappings of field lines along the loop from one photospheric end, we draw a schematic description of the magnetic topology change in terms of the initial distributions of the twist and/or of the axial current density.