The article reports on recent developments in the theory of secondary instability in drift-ion temperature gradient turbulence. Specifically, the article explores secondary instability as a mechanism for zonal flow generation, transport barrier dynamics and avalanche formation. These in turn are related to the space-time statistics of the drift wave induced flux, the scaling of transport with collisionality and β, and the spatio-temporal evolution of transport barriers.
The influence of atmospheric aerosols on the filamentation patterns created by TW laser beams over 10 m propagation scales is investigated, both experimentally and numerically. From the experimental point of view, it is shown that dense fogs dissipate quasi-linearly the energy in the beam envelope and diminish the number of filaments in proportion. This number is strongly dependent on the power content of the beam. The power per filament is evaluated to about 5 critical powers for self-focusing in air. From the theoretical point of view, numerical computations confirm that a dense fog composed of micrometric droplets acts like a linear dissipator of the wave envelope. Beams subject to linear damping or to collisions with randomly-distributed opaque droplets are compared.
In this paper, we report on an integrated program of experimental, computational, and theoretical studies of sheared zonal flows and radially extended convective cells, with the aim of assessing the results of theory-experiment and theory-simulation comparisons. In particular, simulations are used as test beds for verifying analytical predictions (specifically locality and directionality of energy transfer) of nonlinear dynamics and to investigate the suitability of bispectral analysis for studying nonlinear couplings. Initial comparisons to experimental results are presented, and future experimental studies are motivated. We also present analytic and numerical work investigating the role of structures in transport.
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