  We present a numerical study of the dynamics of magnetized, relativistic,
non-self-gravitating, axisymmetric tori orbiting in the background spacetimes
of Schwarzschild and Kerr black holes. The initial models have a constant
specific angular momentum and are built with a non-zero toroidal magnetic field
component, for which equilibrium configurations have recently been obtained. In
this work we extend our previous investigations which dealt with purely
hydrodynamical thick discs, and study the dynamics of magnetized tori subject
to perturbations which, for the values of the magnetic field strength
considered here, trigger quasi-periodic oscillations lasting for tens of
orbital periods. Overall, we have found that the dynamics of the magnetized
tori analyzed is very similar to that found in the corresponding unmagnetized
models. The spectral distribution of the eigenfrequencies of oscillation shows
the presence of a fundamental p mode and of a series of overtones in a harmonic
ratio 2:3:.... These simulations, therefore, extend the validity of the model
of Rezzolla et al.(2003a) for explaining the high-frequency QPOs observed in
the spectra of LMXBs containing a black-hole candidate also to the case of
magnetized discs with purely toroidal magnetic field distribution. If
sufficiently compact and massive, these oscillations can also lead to the
emission of intense gravitational radiation which is potentially detectable for
sources within the Galaxy.
