  Large scale dynamo-generated fields are a combination of interlocked poloidal
and toroidal fields. Such fields possess magnetic helicity that needs to be
regenerated and destroyed during each cycle. A number of numerical experiments
now suggests that stars may do this by shedding magnetic helicity. In addition
to plain bulk motions, a favorite mechanism involves magnetic helicity flux
along lines of constant rotation. We also know that the sun does shed the
required amount of magnetic helicity mostly in the form of coronal mass
ejections. Solar-like stars without cycles do not face such strong constraints
imposed by magnetic helicity evolution and may not display coronal activity to
that same extent. I discuss the evidence leading to this line of argument. In
particular, I discuss simulations showing the generation of strong mean
toroidal fields provided the outer boundary condition is left open so as to
allow magnetic helicity to escape. Control experiments with closed boundaries
do not produce strong mean fields.
