Creation of twist at the core-convection zone interface

Current helicity is a convenient measure of twist of magnetic flux at the base of the solar convection zone. Accurate estimates of twist at these depths are difficult: only surface observations are available, dynamos predict mean rather than total fields, and flux concentration is not well understood. We generate butterfly diagrams’ for a variety of mean field dynamos, showing they produce a variety of current helicities. Not all have the predominance of left-handed twist in the northern hemisphere seen in modern observations. Current helicity therefore may be a useful discriminator among various solar dynamos. Convection influenced by rotation and shear should be the primary source of twist within the convection zone, while ‘helical waves’ driven by magnetic buoyancy, and the nearly 2D mhd instability of toroidal field and differential rotation, could be sources below the convection zone.