Turbulence associated with corotating interaction regions at 1 AU: Inertial and dissipation range magnetic field spectra

Abstract

We examine five Corotating Interaction Regions (CIRs) observed during the recent solar minimum by the Advanced Composition Explorer spacecraft at 1 AU. We apply a familiar series of spectral examinations and compare quantities such as the variance anisotropy, spectral index, cross-and magnetic helicities, and the infered geometry of the wave vectors against established correlations seen in 1 AU turbulence apart from CIR regions. We find variance anisotropies that scale with plasma beta and spectral amplitude, spectral indices in the same familiar ranges, indices within the dissipation range scaling with the apparent rate of energy cascade within the inertial range, and the same linear relationship between cross-and magnetic helicities. As the results agree with earlier established correlations, we conclude that the rate of energy injection by large-scale shear is sufficiently slow as to allow for significant reorganization of the injected energy by the turbulent cascade. This does not mean that there is no evidence of newly injected energy as a result of that large-scale shear. Our companion paper argues that there is significant energy injection within the CIRs. This analysis only argues that energy injection is too slow to fully dominate the interplanetary spectrum. Copyright 2011 by the American Geophysical Union.