Wave example 4. The three first panels starting from top represents de background magnetic field, the solar wind speed, and the electron density measured by RPW, for a four-minute interval, centered on the snapshot (the vertical dashed lines indicates the snapshot boundary). The fourth and fifth panels show the three components and the Y component of the fluctuating magnetic and electric fields respectively: X is in blue, Y in orange, and Z in green. The three bottom panels show the spectral coherence, the phase difference (with electric field corrected by −50° in dashed lines), as well as the expected (orange, blue, and red) and measured (black) the wave phase velocity. The dotted vertical lines indicates the frequency range where the computation of the velocity is reliable (coherence greater than 0.8 between B_y and B_z and greater than 0.7 between E_y and B_z).