Evolution of Near-Sun Solar Wind Turbulence

Abstract

This paper presents a preliminary analysis of the turbulence spectrum of the solar wind in the near-Sun region R < 50R_⊙, obtained from interplanetary scintillation measurements with the Ooty Radio Telescope at 327 MHz. The results clearly show that the scintillation is dominated by density irregularities of size about 100–500km. The scintillation at the small-scale side of the spectrum, although significantly less in magnitude, has a flatter spectrum than the larger-scale dominant part. Furthermore, the spectral power contained in the flatter portion rapidly increases closer to the Sun. These results on the turbulence spectrum forR < 50R_⊙ quantify the evidence for radial evolution of the small-scale fluctuations (≤50 km) generated by Alfvén waves.