Publication: Living Reviews in Solar Physics, 18, 5 (2021); Author: Yuhong Fan
3D view of the magnetic field lines in a simulation of the solar convective dynamo by Fan and Fang (2014) showing the formation of coherent emerging flux bundles of super-equipartition field strengths in the bulk of the solar convection zone.
It has been a prevailing picture that active regions on the solar surface originate from a strong toroidal magnetic field stored in the overshoot region at the base of the solar convection zone, generated by a deep seated solar dynamo mechanism. This article reviews the studies in regard to how the toroidal magnetic field can destabilize and rise through the convection zone to form the observed solar active regions at the surface. Furthermore, new results from the global simulations of the convective dynamos, and from the near-surface layer simulations of active region formation, together with helioseismic investigations of the pre-emergence active regions, are calling into question the picture of active regions as buoyantly rising flux tubes originating from the bottom of the convection zone. This article also gives a review on these new developments. (DOI link to abstract)