Median value (crosses) of several whistler wave parameters as a function of the propagation angle. The black lines show the smoothed values and the smoothed 95% error bars (assuming a normal distribution) are shown in green. Panel a: Wave amplitude normalized to the background magnetic field amplitude. Panel b: Duration of the wave packets. Panel c: Theoretical phase velocity (v_φ) in the plasma frame. Panel d: Frequency in the plasma frame normalized by the local electron cyclotron frequency.