Radio frequency fluctuation spectra during the solar conjunctions of the Ulysses and Galileo spacecraft

Temporal power spectra have been computed from recordings of the downlink f requency fluctuations of the Galileo and Ulysses radio signals during their solar conjunctions. Both the equatorial streamer belt and the polar corona l holes were investigated over a range of ray path solar offset distances f rom 4 to 80 R-circle dot. By combining gapless data from successive trackin g passes, Doppler scintillation power spectra could be computed down to ext remely low frequencies. Some spectra feature a low-frequency turnover at fr equencies around 0.1 mHz that could be interpreted as an outer scale of den sity turbulence in the coronal plasma.