Left panel: amplitude ratio of the fast wave train and slow wave measured at t = 110 plotted against the driver duration in units of the Alfvén transit time across the waveguide. The cutoff above which the fast wave train is no longer considered to be efficiently excited is shown by the vertical dashed line. Middle panel: wavelength of peak spectral amplitude (in units of the waveguide width) of the fast wave train plotted against the driver duration. Right panel: spectral width of the fast wave train signal plotted against the driver duration.