Articles | Volume 27, issue 8
04 Aug 2009
 | 04 Aug 2009

Multi-spacecraft measurement of anisotropic power levels and scaling in solar wind turbulence

K. T. Osman and T. S. Horbury

Abstract. Measurements by the four Cluster spacecraft in the solar wind are used to determine quantitatively the field-aligned anisotropy of magnetohydrodynamic inertial range turbulence power levels and spectral indexes. We find, using time-lagged second order structure functions, that the spectral index is near 2 around the field-parallel direction, which is consistent with a "critical balance" turbulent cascade. Solar wind fluctuations are found to be anisotropic with power mainly in wavevectors perpendicular to the mean field, where the spectral index is around 5/3.