Geometrical configuration of a dust grain partially aligned with its angular momentum J to the magnetic field direction B. The precession of J around B defines the cone angle β, and the precession of maximum moment of inertia I around J defines the angle of internal alignment ζ. Here, the angle ϑ is defined as being between the direction of incident light k and B. The angles α and ϵ are between the direction of the supersonic velocity stream v_g and B and between the anisotropy u_λ in the radiation field and B, respectively. The vector is the projection of v_g on the direction of the magnetic field direction B.