Anisotropy and velocity of small-scale irregularities in the region of solar-wind acceleration

We present the amplitude and frequency fluctuations of radio signals detect ed simultaneously at ground stations at Evpatoriya and Ussuriisk during exp eriments in which radio signals with wavelengths of 5, 8. and 32 cm emitted from the Venera-15 and Venera-16 spacecraft were transmitted through the s olar plasma environment. Relations are obtained between the rates of amplit ude scintillations (determined from the width of temporal spectral and freq uency scintillations (determined from the delay of the fluctuations between the ground stations), on the one hand, and the velocities of the solar win d and of wave-like density disturbances and the anisotropy of irregularitie s, on the other hand. Analysis shows that the transition of the solar-wind flow to a supersonic regime takes place at heliocentric distances of 10-15 solar radii (R-s) and that the flow becomes supersonic at distances exceedi ng 15R(s). Solar-wind density inhomogeneities with scales of about 50 km ar e radially extended. For heliocentric distances from 10 to 20R(s), the degr ee of extension is modest and, as a rule, does not exceed a factor of two. (C) 2000 MAIK "Nauka/Interperiodica".