  The solar cycle appears to be remarkably synchronized with the gravitational
torques exerted by the tidally dominant planets Venus, Earth and Jupiter.
Recently, a possible synchronization mechanism was proposed that relies on the
intrinsic helicity oscillation of the current-driven Tayler instability which
can be stoked by tidal-like perturbations with a period of 11.07 years.
Inserted into a simple alpha-Omega dynamo model these resonantly excited
helicity oscillations led to a 22.14 years dynamo cycle. Here, we assess
various alternative mechanisms of synchronization. Specifically we study a
simple time-delay model of Babcock-Leighton type dynamos and ask whether
periodic changes of either the minimal amplitude for rising toroidal flux tubes
or the Omega effect could eventually lead to synchronization. In contrast to
the easy and robust synchronizability of Tayler-Spruit dynamo models, our
answer for those Babcock-Leighton type models is less propitious.
