Radio wave propagation in the turbulent solar plasma using three satellites

The radio wave propagation in the solar-wind plasma was investigated before and after Mars-2, Mars-7 and Venera-10's superior conjunction. It was found that the moving turbulent solar-wind plasma produced the amplitude and frequency fluctuations and the spectral broadening of monochromatic radio waves. When the Sun-Earth-spacecraft angle decreases from 6° to (0.6) the bandwidth of spectral broadening increases from (0.3) Hz to 300 Hz. The region of 2.5–4° is specific since the bandwidth of spectral broadening is independent of Sun-Earth-spacecraft angle. The spectrum of frequency fluctuations could be represented by a power law with a spectral index of 0.7 ± 0.2. The temporal frequency spectra of the amplitude have two distinct regions. In the low-frequency region the spectral density is approximately constant. The high-frequency portion of the amplitude spectrum follows the power law with a spectral index of 2.8 ± 0.4. The turbulence characteristics of a solar-wind plasma are determined from the experimental data obtained. The three-dimensional wave-number spectrum of irregularities is found to be close to the Kolmogorov-Oboukhov spectrum.The solar-wind density fluctuations decline with heliocentric distance very steeply, but in the distance interval of 7 × 10⁶ – 12 × 10⁶ km, there is a region of enhanced turbulence which could be caused by shock waves.