Velocity shear generation of solar wind turbulence

Journal Article · Sun Nov 01 04:00:00 EST 1992 · Journal of Geophysical Research

DOI:https://doi.org/10.1029/92JA01144· OSTI ID:166719

Roberts, D A; Goldstein, M L; Ghosh, S ^[1]; Matthaeus, W H ^[2]

---

1. NASA Goddard Space Flight Center, Greenbelt, MD (United States)
2. Univ. of Delaware, Newark, DE (United States)

The authors use a two-dimensional, incompressible MHD spectral code to establish that shear-driven turbulence is a possible means for producing many observed properties of the evolution of the magnetic and velocity fluctuations in the solar wind and, in particular, the evolution of the cross helicity ({open_quotes}Alfvenicity{close_quotes}) at small scales. They find that large-scale shear can nonlinearly produce a cascade to smaller scale fluctuations even when the linear Kelvin-Helmholtz mode is stable and that a roughly power law inertial range is established by this process. While the fluctuations thus produced are not Alfvenic, they are nearly equipartitioned between magnetic and kinetic energy. The authors report simulations with Alfvenic fluctuations at high wave numbers, both with and without shear layers and find that it is the low cross helicity at low wave numbers that is critical to the cross helicity evolution, rather than the geometry of the flow or the dominance of kinetic energy at large scales. The fluctuations produced by shear effects are shown to evolve similarly but more slowly in the presence of a larger mean field and to be anisotropic with a preferred direction of spectral transfer perpendicular to the mean field. The evolution found is similar to that seen in some other simulations of HMD turbulence, and thus seems in many respects to be an instance of a more generic turbulent evolution rather than due to specific conditions in the solar wind. 75 refs., 18 figs.

• Sponsoring Organization: USDOE
• OSTI ID: 166719
• Journal Information: Journal of Geophysical Research, Journal Name: Journal of Geophysical Research Journal Issue: A11 Vol. 97; ISSN 0148-0227; ISSN JGREA2
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
ALFVEN WAVES
MAGNETOHYDRODYNAMICS
SHEAR
SOLAR WIND
TURBULENCE
TWO-DIMENSIONAL CALCULATIONS
VELOCITY