Time series of Encounter 4 solar wind parameters: Magnetic field B in RTN coordinates (blue=radial, red=tangential, yellow=normal, purple=magnitude), electron density n_e, solar wind speed v_i, ion temperature T_i, mass flux 4πρv_rr², energy flux , ion beta β_i, predicted angular distance to the heliospheric current sheet ϕ_HCS, and radial distance r. The verticaldashed lines indicate the intervals used to calculate the spectra in Fig. 6.