A charged spinning particle is considered on a general-relativistic spacetime in the presence of a magnetic field. The equation of motion is written in Dixon’s center-of-mass form, but some terms, in particular the spin-electromagnetism interaction, are neglected. The gravitational field is linearized around Minkowski background, and the magnetic field is assumed to be homogeneous (with respect to the flat background). Moreover, the gravitational field is assumed to satisfy the linearized vacuum Einstein equations, so it may be interpreted as a freely propagating (weak) gravitational wave; as the author correctly indicates, this implies, of course, that the gravitational field produced by the magnetic field is neglected. The study concentrates on the observation that, in this situation, one finds some kind of magnetic resonances. These resonances vanish if the gravitational wave is not present. Possible applications to the merger of two neutron stars are briefly indicated.