Global Fourier amplitudes vs. time in models with various burst durations t_bst. The four lowest modes m = 1, 2, 3, and 4 are shown. The left and right columns correspond to the constant-magnitude and declining-magnitude bursts, respectively.The vertical dotted lines indicate the end of the burst in each model. The dotted lines in the bottom row show Fourier amplitudes for the model without the burst for comparison.