Abstract
We report a numerical investigation of three dimensional, incompressible, Hall magnetohydrodynamic turbulence with a relatively strong mean magnetic field. Using helicity decomposition and cross-bicoherence analysis, we observe that the resonant three--wave coupling is substantial among ion cyclotron and whistler waves. A detailed study of the degree of non-linearity of these two populations shows that the ion cyclotron component experiences a transition from weak to strong wave turbulence going from large to small scales, while the whistler fluctuations display a weak wave turbulence character for all scales. This non-trivial coexistence of the two regimes with the two populations of waves gives rise to anomalous anisotropy and scaling properties. The weak and strong wave turbulence components can be distinguished rather efficiently using spatio-temporal Fourier transforms. The analysis shows that while resonant triadic interactions survive the highly non-linear bath of ion cyclotron fluctuations at large scales for which the degree of non-linearity is low for both populations of waves, whistler waves tend to be killed by the non-linear cross-coupling at smaller scales where the ion cyclotron component is in the strong wave turbulent regime. Such situation may have far-reaching implications for the physics of magnetized turbulence in many astrophysical and space plasmas where different waves coexist and compete to transfer non-linearly energy across scales.
Highlights
Turbulence is an ubiquitous dynamical phenomenon involving many spatial and temporal scales
The analysis shows that while resonant triad interactions survive the highly nonlinear bath of ion-cyclotron fluctuations at large scales for which the degree of nonlinearity is low for both populations of waves, whistler waves tend to be killed by the nonlinear cross-coupling at smaller scales where the ion-cyclotron component is in the strong wave turbulent regime
IV, we first show that resonant triadic interactions survive the highly nonlinear bath of ion-cyclotron fluctuations; we show that the three-wave coupling is substantial among ion-cyclotron and whistler waves, using higher-order polyspectra techniques
Summary
Turbulence is an ubiquitous dynamical phenomenon involving many spatial and temporal scales. In rotating turbulence, the effect of the Coriolis force, which decreases as a function of scale, may lead to the conversion of inertial waves into highly nonlinear fluctuations at the so-called Rhines scale Because of these “real life” effects, experiments often show deviations from the existing predictions, and as a result, weak wave turbulence is rarely observed in its pure form [10]. In these examples, the coherent nonlinear structures and/or the different weak wave fields do not “live” in the same part of the spectral range, which facilitates the analytical and experimental disentangling of the two components. VI, where this and other findings are discussed along with their implications
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