Table of contents

We review the results of numerical and experimental studies in quasi-two-dimensional (Q2D) turbulence. We demonstrate that theoretical energy spectra with slopes –5/3 and –3 (Kraichnan–Batchelor–Leith) can be observed only for a special set of external parameters. The bottom drag, beta effect, finite Rossby–Obukhov radius or vertical stratification, which distinguish geophysical Q2D turbulence from its purely 2D counterpart, determine the organization of a Q2D flow on a large scale. Since the spectral energy flux in 2D turbulence is directed upscale, the bottom friction takes on a special role. In the absence of bottom drag the energy condenses on the largest resolvable scale and flow equilibration is not attained.

The evolution of large clusters exposed to a superintense ultrashort laser pulse is considered. Cluster excitation results from the interaction of its electron subsystem with the laser field. Multiple ionization and X-ray emission followed by explosion in clusters irradiated by a laser field are investigated. The increase of the electron temperature in this process and of the charge of the cluster ion are discussed. The reabsorption of photons in such a plasma is found to be relatively small. The optimal conditions are analyzed for efficient absorption of laser radiation by large clusters. This absorption occurs on the surface of the cluster only. The review is done of the works devoted to X-ray emission and generation of high harmonics of the incident radiation from a hot cluster ion. The optical density of the cluster plasma is found to be relatively small for resonance photons of multiply charged atomic ions produced inside the cluster. Expansion and decay of the cluster during and after the laser pulse are discussed.

A letter from S I Vavilov, then President of the Academy of Sciences of the USSR, to Stalin has been discovered in the archives of the Science Department of the Central Committee of the Communist Party of the Soviet Union, which is concerned with the problem of secrecy in physics and suggests criteria by which classified and nonclassified studies may be distinguished. The letter is not only of interest to physicists and science historians, but also is a telling document of the totalitarian times, when it took no less than the states's top leaders to resolve issues as this.