Solid lines (top panel): |J| plotted against t. Solid lines (bottom panel): ^∫E _∥ dl plotted against t. For the cases with two pulses the dashed lines indicate the driving amplitude of the second pulse. Black: t_lag = 0, red: t_lag = 0.9 and blue: t_lag = 1.8. The solid green line is with only one pulse. For the case of v₀ = 0.01. (This figure is available in color in the electronic form.)