- Journal Article
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⊥de≳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 cosαk∝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⊥de≫1 range. Turbulent eddies exhibit a phase-space anisotropy k∥∝k5/3⊥, 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. Show more
Journal / seriesPhysical Review Letters
Pages / Article No.
PublisherAmerican Physical Society
MoreShow all metadata