Excitation of magnetospheric waves by a star quake with ω ≫ c/R _⋆ and a vertical (radial) wavevector k . The wave polarization is set by the direction of the electric field E = B × v /c in the crustal shear oscillation with a horizontal velocity v . Left: crustal motion with v ∥ n ≡ k × B _bg excites an Alfvén wave E ⊥ n . Right: v ⊥ n excites a magnetosonic wave E ∥ n . The wave amplitude is small, so B ≈ B _bg near the star.