Snapshot of the wave energy flux parallel (left) and perpendicular (right) with respect to the magnetic field. The color range is saturated. The solid (dashed) green lines show the first theoretical wave fronts of the fast (slow) waves; the gray lines show the magnetic field lines. The red bars below the x-axis indicate the driver location. The blue lines highlight the field line considered for the analysis in Fig. 8. Movies of the full time sequence are available online.