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. \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. 
Pavel A. Andreev
physics.plasm-ph