Comment on "Spin Contribution to the Ponderomotive Force in a Plasma"

Several years ago, G. Brodin, A. P. Misra, and M. Marklund considered “Spin Contribution to the Ponderomotive Force in a Plasma” Phys. Rev. Lett. $\mathbf{\text{105}}$, 105004 (2010). They applied a two fluid model of electron gas where spin-up and spin-down electrons are considered as two different species. Their approach to this problem appears to be in disagreement with the Pauli equation. The correct model is presented in this comment.