Polarization drift (${\mathbf{v}}_{\mathrm{pol}}=\mathbf{b}\times D_t{\mathbf{u}}_E/{\Omega }_s$)

The inertial correction to the electric drift ${\mathbf{u}}_E=c\mathbf{E}\times \mathbf{B}/B^2$ in a slowly varying magnetic field. In the simplest uniform-field electrostatic case it is ${\mathbf{v}}_{\mathrm{pol}}=m_s{c}^2{\partial }_t{\mathbf{E}}_{\perp }/(q_s{B}^2)$. Its species-dependent current density supplies the perpendicular polarization response needed in many slow plasma instabilities.