Turbulence Regimes of the Solar Wind in the Region of its Acceleration and Initial Stage of Supersonic Motion

Coronal radio sounding experiments were carried out during the solar conjunctions of the spacecraft Ulysses and Galileo, providing information on the solar wind plasma over a wide range of heliocentric distances and heliolatitudes on both East and West limbs of the Sun. An important component of these investigations is to identify the turbulence regimes of the solar wind in its acceleration and initial supersonic regions. This work concentrates on the variation of the spectral index of the temporal frequency fluctuation spectrum αf. The analysis leads to the following preliminary conclusions: (1) At low heliolatitudes the turbulence becomes ‘developed’, with αf reaching the Kolmogorov value of 2/3, at distances beyond 2O R⊙; (2) At high heliolatitudes (poleward of 65°) the solar wind turbulence remains undeveloped out to distances of at least 30 R⊙; (3) At distances close to the Sun (less than 7 R⊙) the spectrum sometimes becomes a double power‐law with small spectral index αf ≃ 0.03–0.11 at low fluctuati...