Multifractal and intermittent nature of substorm-associated magnetic turbulence in the magnetotail

摘要

Analysis is performed on the magnetic field fluctuations for three events in the near-Earth tail to examine the multifractal and intermittent nature of current disruption. The three events encompass observations being made from very near the cross-tail current sheet center (neutral sheet) to some distance away from the neutral sheet. It is found that near the neutral sheet, the scaling properties of the components related to the intensity of the cross-tail current (B_v) and the field-aligned current (B_d) are similar. However, at some distance from the neutral sheet, the scaling properties of the components related to the global magnetic field reconfiguration (B_h) and the field-aligned current are similar. The intermittency coefficient, which is different for components with different scaling properties, ranges from 0.18 to 0.42. This result implies that the intermittency correction needed to apply to the power spectral index for comparison with turbulence theory prediction is ～0.06-0.14, which is significant in comparison with the difference required to distinguish between fluid and MHD turbulence.