Columnar content measurements of the solar-wind turbulence near the sun

The solar-wind turbulence near the Sun is investigated with data obtained near the superior conjunctions of Mariners 6, 7, and 9. The data are time histories of the change in the electron columnar content between the Earth and the spacecraft. It is found that the comoving turbulence spectrum is well represented by a power law P(ν) αν-/sup beta/ of index β=3.9 plus-or-minus0.2 Comparison of the average spectral amplitude near the Sun (rapprox. =0.15 AU) with that near 1 AU shows that the turbulence declines with heliocentric distance as Δn (r) αr-2.38/sup plus-or-minus//sup 0//sup .1//sup 1/, ignoring time variations. In the region near the Sun (0.07approximately-less-thanrapproximately-less-than0.22 AU), Δn (r) declines more slowly. It is suggested that there is a region of enhanced turbulence near the Sun. The Mariner 9 spectral amplitudes correlate with Zurich sunspot number. The relationship of the present observations to theories of solar-wind heating is discussed. (auth)