Radial variations of large‐scale magnetohydrodynamic fluctuations in the solar wind

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Abstract
Two time periods are studied for which a relatively complete set of magnetic field and plasma measurements are available at both 1 AU (from IMP 8 and ISEE 3) and near 4 to 5 AU (from Voyager 1). One of these periods is characterized by the predominance of corotating streams, whereas many transient flows were observed in the second period. The evolution of these two flow systems with heliocentric distance is studied by using power spectral techniques. The power spectra for the system of transient flows are consistent with the hypothesis of turbulent evolution, including an inverse cascade of magnetic helicity to large scales. The power spectra for the system of corotating flows cannot be described so simply.