From top to bottom, a) velocity power on a logarithmic scale with a range of 10⁶ (blue-green-red-yellow),b) magnitude of α on a logarithmic scale from 0.1 to 10, and c) phase of α. The color coding for the phase is shown in the inset. Green (0°) corresponds to the amplitude increasing with I, black (180°) to decreasing, blue (90°) to the waves at higher intensity leading those at the reference intensity and red (270°) to trailing. Rough mode frequencies (courtesy of R. Bogart) for radial order 0 ≤ n ≤ 10 are shown by dots.