Power spectrum of small-scale irregularities in the solar wind

Day to day observations of interplanetary scintillation on ten strongly scintillating radio sources over a period of twelve months show that the power spectrum of the small scale irregularities flattens considerably at temporal frequencies ν < 0·5 Hz. This flattening defines a scale which increases uniformly between 0·1 and 1·0 a.u. from the Sun. The implication of this result will be discussed.