Case study of July 11, 2020: Spectra extracted from the spectrograms displayed in Fig. 3 and corresponding to 07:11:12 UTC, plus a second estimate of the phase velocity and a comparison with a theoretical whistler mode phase velocity model. From top to bottom: magnetic (PB) and electric (PE) trace power spectra of the measured field fluctuations; degree of polarization (DOP) and wave ellipticity (ellip); wave normal vector components (n_X, n_Y, n_Z) in SRF; angle between n and B₀; observed phase velocities and , and cold plasma model of the whistler mode phase velocity calculated in the plasma frame (ω′​/k); arguments of and . See text for more details.