Panel a: example of a wavelet spectrum for the pre-jet intensity oscillations for jet2. The solid thick white contours (around the green surface) are the regions in which the value of the wavelet function is higher than 95% of its maximum value. The area outside the parabolic COI is the region where the wavelet analysis is not valid. Panel b: global wavelet spectra for the distribution of power over time. The highest peak corresponds to the time period of the pre-jet intensity oscillations, i.e. 1.5 min for jet2.