Nonlinear evolution of plasma turbulence generated by a plasma cloud released into a magnetized background plasma is studied using electromagnetic hybrid (fluid electrons and particle ions) plasma simulations incorporating electron inertia. The turbulence considered is generated from free energy in an assumed ring velocity distribution in the released plasma cloud heavy ions. The turbulence ini...

Simulations showing the effect of shear on the collisional diffusion of a 2D point vortex gas are compared to theory. For finite shear the diffusion is considerably smaller than previous zero-shear theories predict. Surprisingly, changing the sign of the applied shear changes the diffusion by an order of magnitude.  2001 Elsevier Science B.V. All rights reserved. The self-diffusion of a 2-dime...

We present an analogy between large plastic deformations of polycrystals and turbulent flows in fluid dynamics. The analogy explains a number of effects observed during large deformations, still unexplained in the language of plasticity theory. We also propose a phenomenological criteria characterizing the “turbulence” of polycrystals. Using this criteria, the paper shows that simple shear is p...

The dependence of mixing efficiency on time-varying forcing is studied by direct numerical simulation (DNS) of Kelvin–Helmholtz (KH) instability. Time-dependent forcing fields are designed to reproduce a wavelike oscillation by solving the equations of motion in a tilted coordinate frame and allowing the tilt angle to vary in time. Mixing efficiency Gc is defined as the ratio of potential energ...

Arguments for and against the widely accepted picture of a solar dynamo being seated in the tachocline are reviewed, and alternative ideas concerning dynamos operating in the bulk of the convection zone, or perhaps even in the near-surface shear layer, are discussed. Based on the angular velocities of magnetic tracers, it is argued that the observations are compatible with a distributed dynamo ...

Atmospheric wind shears control the irregularity structure in the E-region. Near 100 km altitude, where the ion collision frequency is much larger than the ion cyclotron frequency, the degree of shear turning and the direction of maximum shear gradient determine the location of the E-layer peak. The effects of speed shears on the three-dimensional structure of the E-layer are modeled using a sy...

We reconsider the important question of the effect of a strong mean shear flow on the transport of a passive scalar field. By incorporating the effect of resonance, we show that the flux scales with the mean shear Omega as Omega(-1). The results also indicate that the scaling of the flux and cross phase with shear is rather weak and that the cross phase is not always more heavily suppressed tha...

The dependence of mixing efficiency on time-varying forcing is studied by direct numerical simulation (DNS) of Kelvin-Helmholtz (KH) instability. Timedependent forcing fields are designed to mimic a breaking internal wave by solving the equations of motion in a tilted coordinate frame and allowing the tilt angle to vary in time. Mixing efficiency Γc is defined as the ratio of potential energy g...

A generalized quasilinear (GQL) approximation is applied to homogeneous shear turbulence following previous work on the (QL) model. For GQL approximation, velocity fluctuations are decomposed into low- and high-wavenumber groups, former of which solved by considering full nonlinear equations whereas latter obtained from linearized around former.