Anisotropy in fast and slow solar wind fluctuations

Using 5 years of spacecraft data from near Earth orbit, we investigate the correlation anisotropy of solar wind magnetohydrodynamic-scale fluctuations and show that the nature of the anisotropy differs in fast (1500 km s(-1)) and slow (400 km s(-1)) streams. In particular, fast streams are relatively more dominated by fluctuations with wavevectors quasi-parallel to the local magnetic field, while slow streams, which appear to be more fully evolved turbulence, are more dominated by quasi-perpendicular fluctuation wavevectors.