Sunspot rotation and flux rope formation in emerging active regions [poster]
Fan, Y. (2010). Sunspot rotation and flux rope formation in emerging active regions [poster]. In 216th American Astronomical Society Meeting. Miami, FL, US.
We present ideal 3D MHD simulations of the dynamic emergence of a twisted magnetic flux tube from the top layer of the solar convection zone into the solar atmosphere and corona. The simulations show that a twisted subsurface flux tube does not rise bodily into the corona as a whole due to the he... Show moreWe present ideal 3D MHD simulations of the dynamic emergence of a twisted magnetic flux tube from the top layer of the solar convection zone into the solar atmosphere and corona. The simulations show that a twisted subsurface flux tube does not rise bodily into the corona as a whole due to the heavy plasma that is trapped at the bottom concave portions of the helical field lines. Shear and rotational flows on the photosphere driven by the Lorentz force of the twisted flux tube during flux emergence are the crucial means whereby twist is transported from the interior into the solar corona, driving the formation of a coronal flux rope with sigmoid-shaped, dipped core fields. The simulations suggest that sunspot rotations observed in emerging active regions are manifestations of nonlinear torsional Alfvén waves propagating along the emerging flux tube due to an imbalance of twist rate that develops along the emerging flux tube because of the rapid stretching of the emerged field in the corona. Show less