Anisotropic cascades in interstellar medium turbulence

作者：Shaikh Dastgeer^*; Zank Gary P

来源：Astrophysical Journal, 2007, 656(1): L17-L20.

DOI：10.1086/512051

• interplanetary medium
• ISM : kinematics and dynamics
• methods : numerical
• MHD
• solar wind
• turbulence

Anisotropic turbulent cascades in the solar wind and interstellar medium ( ISM) are investigated using three-dimensional incompressible magnetohydrodynamic (MHD) simulations with a numerical resolution of 256(3). In the absence of an external magnetic field (B-0 = 0), the anisotropy in the MHD turbulent fluctuations is mediated primarily by the local magnetic field. The latter leads to a disparity in the spectral transfer of energy along and across the local mean magnetic field. While the anisotropic cascades give rise to the relationship lambda(parallel to) proportional to lambda(2/3)(perpendicular to) between the parallel (lambda(parallel to) similar to 1/k(parallel to)) and perpendicular (lambda(perpendicular to) similar to 1/k(perpendicular to)) length scales of the eddies relative to the local magnetic field, the global energy is found to obey a Kolmogorov-like k(-5/3) anisotropic spectrum in our simulations where turbulence is predominantly subcritical. In the latter, the turbulent cascades are dominated by the nonlinear eddy turnover timescales compared to the linear Alfven wave periods. The critical-balance criterion is therefore not necessarily satisfied in fully developed, strong, anisotropic, high plasma-beta magnetofluid ISM turbulence.

• 出版日期2007-2-10