Example of a helical structure (HS) observed by Solar Orbiter on April 27, 2021. From top to bottom: Total ion density and solar wind radial speed (V_R) in black and blue, respectively; the transverse and normal component (V_T and V_N) of the solar wind speed; the Radial-Transverse-Normal (RTN) component of the interplanetary magnetic field along with |B|; the wavelet spectrum of the total ion density; spectrogram of the normalized reduced magnetic helicity, σ_m; spectrogram of the normalized cross helicity, σ_c; and spectrogram of the normalized residual energy, σ_r. The vertical black and the dashed horizontal white lines denote the PDS start and end time and the f_PDS ± 0.15 mHz range, respectively. The black contour in the wavelet spectrum corresponds to the wavelet power threshold (see also Katsavrias et al. 2026 for more details). The black contour in the σ_m, σ_c, and σ_r panels corresponds to |σ_m| = 0.7.