Multi-mode kink instability as a mechanism for δ-spot formation Original Research Article

We investigate the current driven kink instability of twisted magnetic flux tubes in the solar convection zone. The possibility that kinking flux tubes are responsible for the formation of some δ-spot active regions provides the motivation for this work. We simulate the evolution of a twisted flux tube with a highly parallelized three dimensional MHD spectral code run on a 128 cubed grid. We find that highly twisted flux tubes, when perturbed with a single wavenumber mode, develop large kinks which lead to δ-spot tilt angles as large as 60°. We find that when tubes are perturbed with multiple wavenumber modes, the modes can interact to create a localized kink tilted by as much as 80° with respect to the unkinked portion of the tube. We show that this kind of kinked flux tube can create a δ-spot configuration with opposite polarity spots emerging and remaining in close proximity to each other, with shear developing along the neutral line as the region develops, and with the opposite polarity regions rapidly rotating about each other.