[1] A superposed‐epoch analysis of ACE and OMNI2 measurements is performed on 27 corotating interaction regions (CIRs) in 2003–2008, with the zero epoch taken to be the stream interface as determined by the maximum of the plasma vorticity. When the measurements are rotated into the local‐Parker‐spiral coordinate system, the shear is seen to be abrupt. Converging flows are seen; about half of th...

Abstract. The turbulent dynamo action in a shear flow is considered by making use of a quasilinear approximation and neglecting the back-reaction of a generated magnetic field on turbulence. The shear can stretch turbulent magnetic field lines in such a way that turbulent motions may become suitable for the generation of a large-scale magnetic field even in the absence of any stratification. Th...

We find and investigate via numerical simulations self-sustained two-dimensional turbulence in a magnetohydrodynamic flow with a maximally simple configuration: plane, noninflectional (with a constant shear of velocity), and threaded by a parallel uniform background magnetic field. This flow is spectrally stable, so the turbulence is subcritical by nature and hence it can be energetically suppo...

We study the effects of kinetic helicity fluctuations in a turbulence with large-scale shear using two different approaches: the spectral tau approximation and the second-order correlation approximation (or first-order smoothing approximation). These two approaches demonstrate that homogeneous kinetic helicity fluctuations alone with zero mean value in a sheared homogeneous turbulence cannot ca...

We review recent results obtained in [14] on weak turbulence of shear-Alfvén waves in the limit of strongly anisotropic pulsations that are elongated along a strong external magnetic field. The kinetic equation for energy is presented at the level of three-wave interactions. It is in agreement with the Galtier et al. [13] formulation of the full three–dimensional helical case when taking the pr...

We examine the role of anisotropic turbulence on the shear instabilities in a stratified flow. Such turbulence is expected to occur in the radiative interiors of stars, due to their differential rotation and their strong stratification, and the turbulent transport associated with it will be much stronger in the horizontal than in the vertical direction. It will thus weaken the restoring force w...

The long term goal of this work is to understand the physics of turbulent stratified shear flows as might be found in coastal regions and estuaries where both shear and stratification are strong. It is our hypothesis that turbulence under these conditions of active generation may function in a way that is fundamentally different from weak turbulence below the thermocline (or above the bottom mi...

Many formulas available in the literature for computing sediment transport rates are often expressed in terms of time-mean variables such as time-mean bed shear stress or flow velocity, while effects of turbulence intensity, e.g., bed shear stress fluctuation, on sediment transport were seldom considered. This may be due to the fact that turbulence fluctuation is relatively limited in laborator...

Monte Carlo ion simulation based on neoclassical radial current balance in a divertor tokamak gives a stationary sheared E-->xB--> flow. The neoclassical radial electric field E(r) shows no bifurcation in contrast with earlier orbit loss models, but the shear in E(r) reaches values at which a transition to enhanced confinement has been observed. Also, MHD turbulence analysis shows that a smooth...

Exact coherent structures are three-dimensional, nonlinear traveling wave solutions of the Navier-Stokes equations. These solutions are typically unstable from onset, yet they capture the basic statistical and structural features of low Reynolds number turbulent shear flows remarkably well. These exact coherent structures have now been found in all canonical shear flows: plane Couette, Poiseuil...