Title | Dynamic Phase Alignment in Inertial Alfvén Turbulence |
Publication Type | Journal Article |
Year of Publication | 2020 |
Authors | Milanese LM, Loureiro NF, Daschner M, Boldyrev S |
Journal | Physical Review Letters |
Volume | 125 |
Date Published | 12/2020 |
Keywords | Magnetosphere, Nonlinear dynamics, Solar corona, solar wind |
Abstract | In weakly collisional plasma environments with sufficiently low electron beta, Alfvénic turbulence transforms into inertial Alfvénic turbulence at scales below the electron skin depth, k ⊥ d e ≳ 1. We argue that, in inertial Alfvénic turbulence, both energy and generalized kinetic helicity exhibit direct cascades. We demonstrate that the two cascades are compatible due to the existence of a strong scale dependence of the phase alignment angle between velocity and magnetic field fluctuations, with the phase alignment angle scaling as cos $\alpha$ k ∝ k −1 ⊥. The kinetic and magnetic energy spectra scale as ∝ k −5=3 ⊥ and ∝ k −11=3 ⊥ , respectively. As a result of the dual direct cascade, the generalized helicity spectrum scales as ∝ k −5=3 ⊥ , implying progressive balancing of the turbulence as the cascade proceeds to smaller scales in the k ⊥ d e ≫ 1 range. Turbulent eddies exhibit a phase-space anisotropy k k ∝ k 5=3 ⊥ , consistent with critically balanced inertial Alfvén fluctuations. Our results may be applicable to a variety of geophysical, space, and astrophysical environments, including the Earth's magnetosheath and ionosphere, solar corona, and nonrelativistic pair plasmas, as well as to strongly rotating nonionized fluids. |
DOI | 10.1103/PhysRevLett.125.265101 |
Dynamic Phase Alignment in Inertial Alfvén Turbulence
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