Finding Evidence of Two Inertial Sub-Ranges in Solar Wind Turbulence

This study examines magnetic field turbulence in the near-Sun solar wind using high-resolution measurements from the Parker Solar Probe at a heliocentric distance of approximately ≈ 0.15 au. Power spectral densities (PSDs) were computed from magnetic field fluctuations and analyzed using three complementary methods: visual regression, compensated spectra, and local slope estimates. From the power-law relationship of the form , two spectral breaks were identified at f ≈ 0.005 Hz and f ≈ 0.15 Hz, dividing the PSD into three distinct regions: a 1/f injection range with spectral exponent = 0.90 ± 0.03, an Iroshnikov–Kraichnan subrange with = 1.50 ± 0.04, and a short Kolmogorov subrange with = 1.70 ± 0.01. Structure function analysis supports the presence of these regimes. Using the P-model, the intermittency parameter p was estimated for each region, yielding p ≈ 0.15 in the Kolmogorov range and p ≈ 0.16 in the Iroshnikov–Kraichnan range. Despite differing spectral slopes, the similar p values in the inertial subranges suggest comparable levels of intermittency. Overall, this study demonstrates the coexistence of inertial subranges corresponding to the Iroshnikov–Kraichnan and Kolmogorov regimes. These findings align well with recent observations by Sorriso-Valvo et al. and challenge the notion of a smooth spectral transition between turbulence regimes as a function of heliocentric distance, exemplified in a study by Chen et al.