Arrival-time difference between left- and right-mode polarisations. The shadow covers the frequency 0.5−5 GHz, and the blue shadow presents that due to different velocities of the two modes. The red (green) shadow presents that due to different paths of the propagation caused by gravitational deflection (plasma deflection). The top (bottom) panel is for the magnetic profile with an index of h_b = 1 (h_b = 3).