Global amplitudes of nonaxisymmetric density perturbations A _m as a function of time for individual cos( mϕ) perturbations. The formula for computing A _m is Equation (15) of Boley et al. (2006). Here the integrals are done only over the disk outside 15 AU to suppress contributions from edge effects in the inner disk. The top and bottom panels correspond to the fiducial run (no planet) and the t = 0 planet run, respectively.