The anisotropic nature of the intermittent turbulence spectra in the solar wind

Friday, 19 December 2014
Chuan-Yi Tu1, Xin Wang1, Jiansen He1, Eckart Marsch2 and Linghua Wang1, (1)Peking University, Beijing, China, (2)University of Kiel, Kiel, Germany
Intermittent structures in the solar wind turbulence carry important information on the turbulent non-linear dynamics and the heating effect of solar wind. However, the intermittency on small scales was rarely studied. Here we present a study of intermittent structures in the small timescale from 5 seconds to 100 seconds using the data from WIND observations in the high-speed solar wind. We find that the intermittent structures dominate the magnetic field turbulence in the scale. In this scale, the power spectrum of the intermittent structures with PVI >1 appears to be anisotropic with regards to the angle θRB between the direction of the local background magnetic field and the radial direction. The anisotropic nature in this sub-range is presented as follows: 1. At the scale τ=12s, the power spectral density of the intermittency withθRB = 84o-90o is one time larger than that of the intermittency with θRB =0o-6o; 2. The power spectrum becomes flatter as θRB increases, with an index of -2 at θRB =0o-6o and index of -1.6 at θRB =84o-90o; 3. The most probable value of the proton temperature distribution of the intermittent structures is 2.1×105K, higher than the most probable proton temperature for the general solar wind (1.9×105K); 4. The most probable value of the proton temperature of the intermittency with θRB =70o-90o is 2.2×105K, clearly higher than that with θRB =0o-20o, which is 2.0×105K. We think that the intermittent structures in the scale from 5s to 100s and their anisotropic spectral nature could be related to the non-linear interactions in the MHD turbulence, and they may have some influence on the dissipation processes in the solar wind turbulence.