Figure 1: Rotational configuration of a triaxial ellipsoid characterized by three principal axes: , , and in the inertial coordinate system . Grain angular momentum is conserved in the absence of external torques and directed along -axis. The torque-free motion of the triaxial grain comprises the rotation around the axis of major inertia , the precession of around , and the wobbling of with respect to . The dipole moment , which is fixed to grain body, moves together with the grain and thus radiates electric dipole emission.