  Several years ago, G. Brodin, A. P. Misra, and M. Marklund considered "Spin
Contribution to the Ponderomotive Force in a Plasma" Phys. Rev. Lett.
\textbf{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.
