Dispersion relation of fast (FM) and slow (SM) Rossby modes as well as inertio-gravity (IG) modes, respectively, using the f-plane and the beta-plane approximations at 30° (solid lines) and 15° (dotted lines) for several magnitudes of the toroidal tacholine magnetic field. It starts from panel (a) 0 kG, where the waves are purely hydrodynamic and there is only one Rossy mode, the hydrodynamic Rossby mode (HD). By increasing the intensity of the magnetic field to (b) 5 kG, (c) 15 kG, and (d) 30 kG, we notice that the dispersion relations become increasingly steep.