Table of contents

The present state of the ball-lightning problem is analyzed. Observational data on ball lightning are reviewed and analyzed. Analogs of ball lightning in terms of properties are discussed. Basic characteristics of ball lightning are identified. They include a rigid framework, a chemical method of internal energy storage, and a spotty emission structure. The spottiness results from the existence of a large number of small hot zones which are responsible for the emission. Problems to be resolved are pointed out. Some models which might be of assistance here are described.

A theoretical investigation is reported of coherent bremsstrahlung generated by a relativistic particle together with noncoherent Bethe–Heitler radiation in a medium characterized by macroscopic density inhomogeneities. These inhomogeneities may be due to the structure of the medium or due to fluctuations excited in an initially macroscopically homogeneous medium. The conditions for the observation of the coherent bremsstrahlung in various systems (plasma channel, pile of plates) are considered. The relationship between the coherent bremsstrahlung and some already known effects (inverse Compton eifect involving Langmuir oscillations and transition radiation in media with inhomogeneities) is considered.

Electron Raman scattering of light has been observed recently in many high-temperature superconductors. At temperatures below the critical value there is a clear reduction in the scattering cross section at low transferred frequencies. In contrast to the theoretical predictions, there is no threshold which could be linked to the gap in the electron spectrum. This behavior of the scattering, and particularly its dependence on the transferred frequency, can be explained if we assume that the gap vanishes along certain lines on the Fermi surface.