Extraordinary plasma wave ($n^2=RL/S$)

For propagation perpendicular to the equilibrium magnetic field, this plasma wave has its electric field perpendicular to that magnetic field and generally both parallel and perpendicular to its wavevector. Its dispersion relation is $n^2=RL/S$, using the magnetized cold-plasma dielectric tensor conventions $R=S-g$, $L=S+g$.