Spectral and spatial evolution of compressible turbulence in the inner solar wind

摘要: Magnetic field and plasma data collected by the Helios spacecraft between 0.3 1 AU near activity minimum of solar cycle 21 have been analyzed to establish spectral characteristics compressive fluctuations in inner wind their relation morphology flow magnetic field. The turbulence level is found be closely related stream structure or latitudinal location with respect heliospheric current sheet. Compressive low-speed flows more fully developed intense. spectra are radially invariant come close a −5/3 law. In contrast, fast becomes increasingly compressive, terms growing amplitudes δn/n δB/B, increasing heliocentric distance. reveal flatter high-frequency part, which gradually seems get straightened out at large distances. Single case studies, as well averaged features, presented discussed context theoretical literature.