Inverse cascade of hybrid helicity in $B \Omega$-MHD turbulence
| Autor: | Sébastien Galtier, Ludovic Petitdemange, Mélissa D. Menu |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2019 |
| Předmět: |
Fluid Flow and Transfer Processes
Physics Turbulence Computational Mechanics Physics - Fluid Dynamics Rotation 01 natural sciences Helicity Physics - Plasma Physics 010305 fluids & plasmas Magnetic field Physics::Fluid Dynamics Rossby number Astrophysics - Solar and Stellar Astrophysics Inviscid flow Modeling and Simulation Quantum electrodynamics 0103 physical sciences Magnetic Prandtl number 010306 general physics Magnetic dipole Astrophysics - Earth and Planetary Astrophysics |
| Popis: | We investigate the impact of a solid-body rotation $\Omega_0$ on the large-scale dynamics of an incompressible magnetohydrodynamic turbulent flow in presence of a background magnetic field $\bf B_0$ and at low Rossby number. Three-dimensional direct numerical simulations are performed in a periodic box, at unit magnetic Prandtl number and with a forcing at intermediate wavenumber $k_f=20$. When $\Omega_0$ is aligned with $\bf B_0$ (i.e. $\theta \equiv \widehat{\left(\Omega_{0}, \bf B_0 \right)} = 0$), inverse transfer is found for the magnetic spectrum at $k0$ and becomes weak when $\theta \ge 35^o$. These properties are understood as the consequence of an inverse cascade of hybrid helicity which is an inviscid/ideal invariant of this system when $\theta=0$. Hybrid helicity emerges, therefore, as a key element for understanding rotating dynamos. Implication of these findings on the origin of the alignment of the magnetic dipole with the rotation axis in planets and stars is discussed. Comment: 9 pages, 10 figures |
| Databáze: | OpenAIRE |
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