Influence of intermittency on the anisotropy of magnetic structure functions of solar wind turbulence. Issue 2 (6th February 2016)

• Record Type: Journal Article
• Authors: Pei, Zhongtian; He, Jiansen; Wang, Xin; Tu, Chuanyi; Marsch, Eckart; Wang, Linghua; Yan, Limei
• Is Part Of: Journal of geophysical research. Volume 121:Issue 2(2016:Feb.)
• Page Start: 911
• Page End: 924
• Publication Date: 2016-02-06
• Subjects: solar wind -- turbulence -- intermittency; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/2015JA021057
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: 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 ΘRB (the angle between local mean magnetic fieldB 0 and radial directionR ). Thus, the scaling exponent ( ξ ( p, ΘRB )) of every structure function of order ( p ) is obtained for different angles. Before removing intermittency, ξ ( p, ΘRB ) shows a distinctive dependence on ΘRB : from monofractal scaling law at ΘRB ~0° to multifractal scaling law at ΘRB ~90°. In contrast after eliminating the intermittency, ξ ( p, ΘRB ) is found to be more monofractal for all ΘRB . The extended structure‐function model is applied to ξ ( p, ΘRB ), 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 ΘRB 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. Key Points: Structure functions look more isotropic when most intermittency is removed Intermittency is more abundant when sampled transversely, while scarce when sampled longitudinally Extended P model is successfully applied to investigate the anisotropy of structure functions