Power spectrum displaying the pattern speed of the m = 2 and m = 4 Fourier components, during the entire simulation, of the gSa (top) and gSb (bottom) models. Contour levels are indicated for each panel. Note that the gSa bar evolves (slows down and extends) much more and its two-armed SS is twice as strong as for the gSb model (top left). Despite the slightly stronger gSb bar, the effect on ΔL in the gSa’s outer disk is much more prominent (Fig. 2) because of the combined effect of the bar and stronger spirals.