Turbulence associated with corotating interaction regions at 1AU: Inertial range cross-helicity spectra

Abstract

[1] We examine five corotating interaction regions and their surrounding slow and fast wind flows observed by the Advanced Composition Explorer spacecraft at 1 AU during solar minimum conditions in 2007 and 2008. We compute spectra of total power (magnetic + kinetic) and spectra of the cross helicity in an attempt to better understand turbulence generation within the shear flow. Consistent with previous work, we find that Sunward-propagation signatures exist at high levels compared with the surrounding flow and sometimes dominate over a broad range of spacecraft-frame frequencies. There is a suggestion that the Sunward-propagation signatures start at small scales and evolve toward larger scales, although this may simply reflect the need to inject larger amounts of energy at the large scales before significant Sunward propagation is observed. The power spectra are conspicuously lacking in any features that would normally be expected to show energy injection over a finite range of frequencies as is the often the case in kinetic instabilities.