V.P51 — Magnetosonic dispersion

Magnetosonic dispersion: fast and slow magnetosonic modes have omega^2 = (1/2) k^2 [(c_s^2 + v_A^2) +/- sqrt((c_s^2 + v_A^2)^2 - 4 c_s^2 v_A^2 cos^2 theta)], the two compressible MHD wave modes coupling sound speed c_s and Alfven speed v_A.