Anisotropic MHD Turbulence in the Interstellar Medium and Solar Wind

Abstract

Abstract.A theoretical model is given of anisotropic magnetohydrodynamic turbulence in the interstellar medium and the solar wind. The model is motivated by observations that show significant deviations from the Kolmogorov powerlaw. Dimensional and heuristic arguments are given and critically assessed. On the basis of the weak turbulence approximation in which three-wave interactions dominate, analytical and numerical results are obtained for the anisotropic energy spectrum produced by the random scattering of shear Alfvén waves propagating parallel to a largescale magnetic field. The energy spectrum is shown to be proportional to 2 k − ⊥ , qualitatively consistent with some observations and wave kinetic theory.

A fluid description of kinetic effects for Alfvén wave trains

“…In the range of scales for which the Alfvén time is the shortest, a weak turbulence regime is expected, characterized by a k 2 energy spectrum [3,4]. In contrast, in the spectral domain where the opposite ordering holds, the turbulence is strong with a spectrum whose behavior is still debated between k 5 3 and k 3 2 [5,6,7,8]. In the´k k µ-plane, the two regimes are separated by a "critical curve" of the form k k 2 3 , according to the Goldreich-Shridhar theory [9].…”