Here, the orbital term is determined by the macroscopic energy current with respect to an arbitrary reference point and does not depend on the polarization. The spin term, on the other hand, relates to the phase between orthogonal field components and is completely determined by the state of polarization [25]. In a monochromatic optical beam, the spin and orbital currents can be respectively written in the form where E [M] ∗ · ( ∇ ) E [M] = E [M] ∗ x ∇ E [M] ∗ x + E [M] ∗ y ∇ E [M] y + E [M] ∗ z ∇ E [M] z is the invariant Berry notation [26]. It has been shown that both spin and orbital currents originate from the beam transverse inhomogeneity and their components are directly related to the azimuthal and radial derivatives of the beam profile parameters. However, the orbital currents are mainly produced by the phase gradient, while the spin currents are orthogonal to the intensity gradient [22]. As shown in the following, the spin and orbital currents will play different roles in the optical Magnus effect. The monochromatic beam can be formulated as a localized wavepacket whose spectrum is arbitrarily narrow [27]. As a mechanical analogy, the circularly polarized wavepacket acts as the rotating ball in our model. To generate an asymmetric intensity distribution, we choose the angle of the fixed unit vector u as θ = π/ 360. Note that such a vectorial beam should can be realized experimentally without technical difficulties [28, 29]. In general, the rotation properties of wavepacket are expressed by the transverse momentum currents as shown in Fig. 2. Very surprisingly, the orbital currents are polarization-dependent in this polarization model [Figs. 2(a) and 2(d)]. This is due to the presence of polarization-dependent screw wavefront. For the left circular polarization σ = +1, the total transverse momentum currents in the exterior part of wavepacket present an anticlockwise circulation, while in the inner part exhibit a clockwise circulation [Fig. 2(c)]. For the right circular polarization σ = − 1, the total transverse momentum currents present an opposite characteristics [Fig. 2(f)]. The inherent physics underlying this intriguing effect is the combined contributions of transverse spin and orbital currents. The wavepacket cannot be regarded as a rigid ball due to the opposite circulations. This is significantly different from the mechanical Magnus effect. For the model [W] under the condition θ = π/ 2, which has also been verified by Hertz vec- tor method [30], the polarization-dependent rotation of the transverse momentum currents are plotted in Fig. 3. Very interestingly, the orbital currents are polarization-independent 7 p [M] S = Im[( E [M] · ∇ ) E [M] ∗ ] , (17) p [M] O = Im[ E [M] ∗ · ( ∇ ) E $^{[M]}$] , (18)