  The dynamics of convecting fluids in rotating spherical shells is governed at
Prandtl numbers of the order unity by the interaction between differential
rotation and roll-like convection eddies. While the differential rotation is
driven by the Reynolds stresses of the eddies, its shearing action inhibits
convection and causes phenomena such as localized convection and turbulent
relaxation oscillations. The response of the system is enriched in the case of
dynamo action. Lorentz forces may brake either entirely or partially the
geostrophic differential rotation and give rise to two rather different dynamo
states. Bistability of turbulent dynamos exists for magnetic Prandtl numbers of
the order unity. While the ratios between mean magnetic and kinetic energies
differ by a factor of 5 or more for the two dynamo states, the mean convective
heat transports are nearly the same. They are much larger than in the absence
of a magnetic field.
