A phase-space boundary integration of the Vlasov equation for collisionless one-dimensional stellar systems

The evolution of one dimensional (stratified) self-gravitating systems of stars with constant phase-space density (water bag model) is investigated by following the motion of the boundary curves defining the systems. The results are compared with those obtained by sheet-model computer experiments and good agreement is found. New aspects of the evolution, revealed by the present method, are discussed.     

Eclipse of radio emission on 7 March, 1970 at 10 cm wavelength from the active region associated with McMath plage 10 618

Radio emission of 10 cm from the whole disk was monitored during the eclipse of 7 March, 1970 by the Aerospace San Fernando Observatory and AFCRL Sagamore Hill Solar Radio Observatory. For both, the active region associated with sunspot 17 774, McMath region 10 618, was occulted. At Sagamore Hill the entire region was occulted. At SFO only the southern half of the sunspot group and the hydrogen plage southeast of the group was occulted. This region produced an importance class 1N flare and 10 cm burst beginning at 1601 UT and was enhanced about 15 flux units above the mean value of 190 units at onset.The Sagamore Hill data indicate the region was about 3.8 and contributed about 0.21 of the total radiation from the disk. The SFO data gave about 5.4 for the size of the southern half of the region and showed that about 0.20 of the total radiation came from there. Radiation came primarily from the hydrogen plage southeast of the major spot of the group. The hydrogen plage northwest of the group did not contribute significantly. Although the small flare occurred in this region, it did not contribute more than 0.04 of the total (0.20 of the active region) at occultation of region 10 618.     

The termination of the solar wind

It has previously been suggested that the solar wind might terminate at distances of 5 AU to 20 AU from the Sun, and that the solar wind might be drastically slowed down by charge exchange and photoionization of interstellar hydrogen atoms which approach the Sun. However, recent satellite measurements of resonantly scattered Lyman alpha radiation, together with pulsar dispersion and Faraday rotation measures, imply very small values for the interstellar hydrogen density (0.05 cm⁻³) and magnetic field strength (3 μG). As a result, the solar wind is not expected to be slowed down by more than about 30% inside the termination distance, which is expected to be about 100 AU.     

Imperfect fluid Friedmannian cosmology

The bulk viscosity is introduced into the frame of ordinary Friedmannian cosmology (under highly idealized assumption of the constant coefficient of bulk viscosity). Explicit solutions are given for the viscous flat universe filled with the dust-substratum and for the viscous radiative universe. The problem, how does the introduction of viscosity affect the appearance of singularity, is briefly discussed.     

Densities deduced from perturbations at high altitudes

Atmospheric densities between 1500 and 3000km have been determined from observations of satellites with large surface to mass ratios. The analysis has been made for optimum periods where the satellite is continuously in sunlight and when the effects of Earth albedo are minimum. Twenty six values of density obtained from 1965 to 1970 have been analysed.     

Equivalent width of interstellar molecular lines

We have made an analysis of the observed equivalent widths of the lines of Lyman and Werner bands by Smith. The H₂ column densities of 3×10¹⁹ to 10²⁰ and the excitation temperature of 80 to 150 K satisfy the observations. This temperature refers to the kinetic temperature. We have also discussed the importance of getting the excitation temperature from lines of H₂ and other heteronuclear diatomic molecules for the same star and from different regions of space.     

Fine structure of a very bright active region at a wavelength of 2.8 cm

The radio structure of the active region McMath 11976 has been investigated with an east-west resolution of 16″ at a wavelength of 2.8 cm. Six bright components were found with angular sizes of the order of 20″. From the position measure of these components in two following days the heights above the solar photosphere are determined. Their positions are compared with the Hα and magnetic structure of the active region. The derived brightness temperatures reach unusual values, up to 6 × 10⁶K for the brightest component.     

8–13 μm spectrophotometry of Comet Kohoutek

Spectrophotometry of Comet Kohoutek (1973f) covering the wavelength range 8–13 μm is presented. The spectral shape of the derived flux excess above a blackbody closely resembles that seen in circumstellar and interstellar dust and generally attributed to metallic silicates.     

MHD free-convection flow past an accelerated vertical porous plate in a rotating fluid

The three-dimensional flow of an electrically conducting and incompressible viscous fluid past a uniformly accelerated infinite vertical porous plate is studied in a rotating fluid. The flow is assumed to be at small magnetic Reynolds number so that the induced magnetic field is neglected. An exact solution has been obtained by defining a complex velocity with the help of the Laplace transform method for the Prandtl number equal to unity. The effects of rotation, magnetic and free-convection parameters are discussed for the whole problem. Also, the skin-friction components on the plate are discussed.