Micro-Turbulence in the solar wind at 5-76 Rs observed with interplanetary scintillation

We study the properties of micro-turbulence in the solar wind using interplanetary scintillation (IPS) observations made with the single dish antenna operating at 2.3 GHz and 8.5 GHz. Our IPS observations were made during September-October in 1992 and 1993 and covered a radial distance range of 5-76 solar radii (Rs). We apply the spectral-fitting method to obtain properties of solar wind turbulence, such as axial ratio of anisotropy, inner scale of dissipation length, power-law spectral index, and solar wind velocity. We also examine the velocity dependence of the turbulence near the sun, and find the following results. (1) Both low-speed and high-speed solar-wind flows show acceleration at the distance range of 10-30 Es, which is consistent with previous works. (2) The radial dependence of anisotropy and spectral index show no significant difference between the low-speed and high-speed solar wind. (3) Only the inner scale length shows a dependence on flow speed: the inner scale in the high-speed wind is 1.4 ±0.3 times larger than that in the low-speed wind.