Influence of intermittency on the anisotropy of magnetic structure functions of solar wind turbulence

Intermittency appears to be connected with the spectral anisotropy of solar wind turbulence. We use the Local Intermittency Measure to identify and remove intermittency from the magnetic field data measured by the Ulysses spacecraft in fast solar wind. Structure functions are calculated based on the time sequences as obtained before and after removing intermittency and arranged by time scale ( τ ) and Θ RB (the angle between local mean magnetic field B 0 and radial direction R ). Thus, the scaling exponent ( ξ ( p , Θ RB )) of every structure function of order ( p ) is obtained for different angles. Before removing intermittency, ξ ( p , Θ RB ) shows a distinctive dependence on Θ RB : from monofractal scaling law at Θ RB ~0° to multifractal scaling law at Θ RB ~90°. In contrast after eliminating the intermittency, ξ ( p , Θ RB ) is found to be more monofractal for all Θ RB . The extended structure‐function model is applied to ξ ( p , Θ RB ), revealing differences of its fitting parameters α (a proxy of the power spectral index) and P 1 (fragmentation fraction) for the cases with and without intermittency. Parameter α shows an evident angular trend falling from 1.9 to 1.6 for the case with intermittency but has a relatively flat profile around 1.8 for the case without intermittency. Parameter P 1 rises from around 0.5 to above 0.8 with increasing Θ RB for the intermittency case and is located between 0.5 and 0.8 for the case lacking intermittency. Therefore, we may infer that it is the anisotropy of intermittency that causes the scaling anisotropy of energy spectra and the unequal fragmentation of energy cascading.