Velocity of the Inner Solar Wind from Coronal Sounding Experiments with Spacecraft

Measurement results are presented for the velocity of density irregularities in solar wind plasma, which modulate the frequency of coherent radio signals from the Galileo spacecraft in the S-band. The measurements have been performed by the spaced receiving technique at ground monitoring stations. The data cover a range of heliocentric distances from 7 to 72 solar radii at low heliolatitudes near solar minimum. It is shown that acceleration of slow solar wind continues up to distances of about 30 solar radii. In the overlapping ranges of distances from the Sun, the results are qualitatively consistent with LASCO SOHO data for the same periods, with the previous results obtained by analyzing the amplitude fluctuations of signals from the Venera 15 and 16 spacecraft, and with the more recent measurements acquired using the Mars Express spacecraft.