Spectral features of magnetic field observations. Upper panel: trace of the Fourier power spectral densities (PSDs) for PSP (black line) and BepiColombo (red line) orbits. The PSD at the PSP orbit follows the Iroshnikov-Kraichnan scaling of MHD turbulence f^−3/2, while at the BepiColombo orbit, the Kolmogorov scaling of fluid turbulence f^−5/3 is observed. Lower panel: helicity spectrum h_m at both PSP (a) and BepiColombo (b) locations, respectively. At the PSP orbit, h_m follows a f^−5/2 power-law, while at the BepiColombo orbit, a f^−8/3 scaling is observed. The gray lines are the 95% confidence intervals for both panels.