  Direct numerical simulations of a liquid metal filling the gap between two
concentric spheres are presented. The flow is governed by the interplay between
the rotation of the inner sphere (measured by the Reynolds number Re) and a
weak externally applied axial magnetic field (measured by the Hartmann number
Ha). By varying the latter a rich variety of flow features, both in terms of
spatial symmetry and temporal dependence, is obtained. Flows with two or three
independent frequencies describing their time evolution are found as a result
of Hopf bifurcations. They are stable on a sufficiently large interval of
Hartmann numbers where regions of multistability of two, three and even four
types of these different flows are detected. The temporal character of the
solutions is analysed by means of an accurate frequency analysis and Poincar\'e
sections. An unstable branch of flows undergoing a period doubling cascade and
frequency locking of three-frequency solutions is described as well.
