Cylindrical oscillations of force-free electromagnetic fields

This paper is devoted to Force-Free Electromagnetic Oscillations in a constant magnetic field. A correction is made in the derivation of the basic equation. The paper confirms the predicted spectrum of frequencies, namely _n = _o (n + 1)^1/2;n = 0, 1, 2, .... In addition it is suggested that hybrid frequency _n = ( _n ² + _H ² )^1/2 should be found in observational data.     

The production of light elements in unconventional cosmologies with VMOs

The abundances of light elements (deuterium, helium and lithium) are calculated in unconventional cosmologies in which these elements are produced by interaction of fast -particles ejected by massive pregalactic stars with a purely hydrogenous cosmological substrate. The number density and energetics of such stars needed for suitable production of light elements are estimated. It is shown that the models always lead to overproduction of lithium. The intensity of ultraviolet, X-ray, and -ray emission caused by explosions of pregalactic massive stars is calculated. The distortions of cosmic background radiation by Compton losses of electrons heated by explosive stars are also calculated.     

Magnetic reconnection in a high-temperature plasma of solar flares

A simple self-consistent model of a high-temperature turbulent current sheet (HTCS) is considered. The anomalous character of plasma conductivity in a sheet is assumed to be due to gradient instabilities. The possibility of a low threshold of their excitation is demonstrated by an example of temperature-drift instability.Application of the HTCS model to the hot or main phase of a solar flare is discussed. The model consistently explains many observed properties of this phase.     

On the existence of cosmological evolutionary effects

Parameters of the distant galaxy clusters of 3C295 (z=0.46) and Cl 0024+1654 (z=0.39) are compared with the predictions made using galaxies of the local clusters Coma (z=0.023) and DC 0329–52 (z=0.057) taking theK-effect into account. The distributions of colour and morphological type, and the amplitudesF ⁺/F^– of the ₀ 4000 discontinuity are examined and no evidence for evolution of the galaxies and the clusters can be seen.     

Observation of chromospheric evaporation during the solar maximum mission

A sample of flares detected in 1980 with the Bent Crystal Spectrometer and the Hard X-Ray Burst Spectrometer on the Solar Maximum Mission satellite has been analysed to study the upward motions of part of the soft X-ray emitting plasma. These motions are inferred from the presence of secondary blue-shifted lines in the Ca XIX and Fe XXV spectral regions during the impulsive phase of disk flares. Limb flares do not show such blue-shifted lines indicating that the direction of the plasma motion is mainly radial and outward. The temporal association of these upward motions with the rise of the thermal phase and with the impulsive hard X-ray burst, as well as considerations of the plasma energetics, favour the interpretation of this phenomenon in terms of chromospheric evaporation. The two measureable parameters of the evaporating plasma, emission measure and velocity, depend on parameters related to the energy deposition and to the thermal phase. The evaporation velocity is found to be correlated with the spectral index of the hard X-ray flux and with the rise time of the thermal emission measure of the coronal plasma. The emission measure of the rising plasma is found to be correlated with the total energy deposited by the fast electrons in the chromosphere by collisions during the impulsive phase and with the maximum emission measure of the coronal plasma.     

DEFORMATION OF SEISMIC WAVELETS BY THIN LAYERS AND LAYERED BOUNDARIES*

Using plane wave theory and assuming a given input wavelet the shape of the reflected (or transmitted) wavelet from a layered boundary is derived. Several types of boundaries are considered, among them the weathered layer and a wedge shaped intermediate layer. Different angles of incidence and all internal multiples are taken into account. The examples shown in the figures can be used for a direct comparison between theoretical and observed shapes of reflected (or transmitted) wavelets from special boundaries.     

An ocean-bottom hydrophone recorder for seismic refraction experiments

A new and inexpensive pop-up ocean-bottom hydrophone recorder has been developed for use in seismic refraction experiments. It is capable of operating in water depths of up to 4000 m and in very rugged topography, and uses an acoustic command system built by the U.K. Institute of Oceanographic Sciences for recovery. The instrument is mounted in an inexpensive cylindrical pressure case based on commercially available extruded aluminium alloy tubing, and uses glass spheres and syntactic foam for buoyancy. Hydrophone and clock signals are frequency modulated and recorded on tape cassettes, with a recording duration of three hours allowing up to 18 programmed shot windows. The prototype has made seven free descents on the Mid-Atlantic ridge and in the Gulf of Oman, and successfully recorded shots under operational conditions for the first time in September 1979. The total component cost of the prototype was £2740 (1979 prices).(Department of Earth Sciences, University of Cambridge Contribution No. ES135).     

Evidence for gas accumulation associated with diapirism and gas hydrates at the head of the Cape Fear Slide

Single-channel seismic reflection profiles show evidence for areas of significant gas accumulation at the head of the Cape Fear Slide on the continental rise off North Carolina. Gas accumulation appears to occur beneath a gas hydrate seal in landward-dipping strata and in domed strata associated with diapirism. In addition, gas venting may have occurred near diapirs located at the head of the slide.     

Weakly non-linear free oscillations in a basin of variable depth

Weakly non-linear free oscillations in a basin of variable depth filled with non-viscous fluid are investigated in terms of the long waves theory using the perturbation technique. Solutions to the initial two approximations for the horizontal velocity component and free surface departure are numerically derived. An attempt is made to determine the area of applicability of the linear theory by applying a parabolic bottom profile to the basin.Translated by V. Puchkin.