  We study the effects of Rashba spin-orbit coupling on the spin torque induced
by spin waves, which are the plane wave dynamics of magnetization. The spin
torque is derived from linear response theory, and we calculate the dynamic
spin torque by considering the impurity-ladder-sum vertex corrections. This
dynamic spin torque is divided into three terms: a damping term, a $distortion$
term, and a correction term for the equation of motion. The $distorting$ torque
describes a phenomenon unique to the Rashba spin-orbit coupling system, where
the distorted motion of magnetization precession is subjected to the
anisotropic force from the Rashba coupling. The oscillation mode of the
precession exhibits an elliptical trajectory, and the ellipticity depends on
the strength of the nesting effects, which could be reduced by decreasing the
electron lifetime.
