Duan, D;
He, J;
Pei, Z;
Huang, S;
Wu, H;
Verscharen, D;
Wang, L;
(2018)
Angular Independence of Break Position for Magnetic Power Spectral Density in Solar Wind Turbulence.
The Astrophysical Journal
, 865
(2)
10.3847/1538-4357/aad9aa.
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Abstract
The break in power spectral density (PSD) around the ion scales indicates the onset of dissipation and/or dispersion of kinetic turbulence. For Alfvén waves in the kinetic regime, the dissipation and dispersion are individually dependent on the propagation angle, θ kB, which has θ RB (the angle between radial direction and local mean magnetic field direction) as a proxy in solar wind measurements. The relation between θ RB and the break position helps us find the role of dissipation and/or dispersion for deforming the PSD profile. In order to locate the spectral break position automatically and quantitatively, we develop a dual-power-law fitting method to fit the PSD profiles in both MHD and kinetic ranges simultaneously. The break position f b is found to change little with θ RB, suggesting an angular independence of the spectral break. Furthermore, f b in our statistical study of fast solar wind near 1 au is consistent with a wavenumber k satisfying k(ρ p + d p) ~ 1 (ρ p is the thermal proton gyroradius and d p is the proton inertial length), independently of θ RB. To interpret this independence, we incorporate the effects of both dissipation and dispersion in a unified description, which is the breakdown of the magnetic frozen-in condition in wavenumber space (k ∥, k ⊥). The breakdown of the frozen-in condition is relatively isotropic compared to the strong anisotropy of dispersion and dissipation. Furthermore, the spatial scale for the onset of the breakdown frozen-in condition is estimated to be the sum of ρ p and d p.
| Type: | Article |
|---|---|
| Title: | Angular Independence of Break Position for Magnetic Power Spectral Density in Solar Wind Turbulence |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.3847/1538-4357/aad9aa |
| Publisher version: | http://doi.org/10.3847/1538-4357/aad9aa |
| Language: | English |
| Additional information: | This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions. |
| Keywords: | solar wind, turbulence |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10059466 |
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