Impurity pinch from a ratchet process.

A ratchet-type average velocity is shown to appear for test particles moving in a stochastic potential and a magnetic field that is space dependent. This is a possible explanation for impurity behavior in tokamak plasmas.

Stationary vortical flows in two-dimensional plasma and in planetary atmospheres.

We derive the equation governing the asymptotic stationary states generated by decaying turbulence in two-dimensional plasma and planetary atmosphere. These fluids may be described by the Charney-Hasegawa-Mima equation and their relaxation states show a high degree of organization in vortical flows, similar to the Euler fluid. We develop a field-theoretical framework and show that these systems attain at stationarity the extremum of an energy functional corresponding to self-dual fields.

Pole dynamics for the flierl-petviashvili equation and zonal flow.

Using the method of positions of the complex singularities, we identify a class of new, exact solutions of the Flierl-Petviashvili equation. The solutions are periodic and have the geometry of the zonal flow. We examine the physical properties and find that the solution can reproduce data from experimental observations and numerical simulations.

Self-duality of the asymptotic relaxation states of fluids and plasmas.

The states of asymptotic relaxation of two-dimensional fluids and plasmas present a high degree of regularity and obedience to the sinh-Poisson equation. We find that by embedding the classical fluid description into a field-theoretical framework, the same equation appears as a manifestation of the self-duality.

Magnetic line trapping and effective transport in stochastic magnetic fields.

The transport of collisional particles in stochastic magnetic fields is studied using the decorrelation trajectory method. The nonlinear effect of magnetic line trapping is considered together with particle collisions. The running diffusion coefficient is determined for arbitrary values of the statistical parameters of the stochastic magnetic field and of the collisional velocity. The effect of the magnetic line trapping is determined. New anomalous diffusion regimes are found.

Soliton modulation of the turbulence envelope and plasma rotation.

The space-uniform amplitude envelope of the ion-temperature-gradient driven turbulence is unstable to small perturbations and evolves to nonuniform, solitonlike modulated profiles. The induced poloidal asymmetry of the transport fluxes can generate spontaneous poloidal spin-up of the tokamak plasma.

Coherent structures in a turbulent environment.

A systematic method is proposed for the determination of the statistical properties of a field consisting of a coherent structure interacting with turbulent linear waves. The explicit expression of the generating functional of the correlations is obtained, performing the functional integration on a neighborhood in the function space around the soliton. The results show that the non-Gaussian fluctuations observed in the plasma edge can be explained by the intermittent formation of nonlinear coherent structures.

Diffusion in biased turbulence.

Particle transport in two-dimensional divergence-free stochastic velocity fields with constant average is studied. Analytical expressions for the Lagrangian velocity correlation and for the time-dependent diffusion coefficients are obtained. They apply to stationary and homogeneous Gaussian velocity fields.

Spectrum of coherent structures in a turbulent environment

The statistical properties of the turbulent field consisting of drift waves randomly interacting with a coherent structure are investigated. By using a nonperturbative method (analogous to the "semiclassical" approach in quantum mechanics), we calculate explicitly the generating functional of the correlations.

Possible mechanism for laser-induced two-dimensional periodic structures by analogy with the Bénard effect.

An explanation is presented for the formation of periodic structures on solid surfaces under powerful laser irradiation through an analogy to the Bénard effect.