Wavelet analysis of velocity and magnetic field fluctuations measured with the He I 10 830 Å triplet. Top panel: power of the WCS between the velocity and magnetic field fluctuations. The gridded region indicates the parts of the spectra outside the cone of influence. Solid black lines mark the 95% confidence level. The vertical dashed blue line indicates the time illustrated in the spectra from the middle and bottom panels. Middle panel: wavelet phase difference between the velocity and magnetic field fluctuations in the umbra at 08:20 UT. Vertical dotted lines delimit the region where the power of the WCS is above the 95% confidence level. Bottom panel: coherence of the phase difference. The horizontal dashed lines indicate the 0.7 threshold.