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.     

Mass motions in a heated flare filament

Energy transport in a hot flare plasma is examined with particular reference to the influence of fluid motion. On the basis of dimensional considerations the dynamical timescale of the flare plasma is shown to be comparable to the timescale for energy loss by conduction and radiation. It is argued that mass motion is likely to have a profound influence on the evolution of the flare.The detailed response of a flare filament to a localized injection of energy is then analyzed. Radiative, conductive and all dynamical terms are included in the energy equation. Apart from greatly enhancing the rate of propagation of the thermal disturbance through space, mass motion is found to be significant in transferring energy through the moving fluid.Finally the predicted thermal structure is discussed and it is concluded that the presence of mass motions in the flare may be inferred from the form of the soft X-ray differential emission measure.     

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.     

Solar wind induction in Mercury: Constraints on the formation of a magnetosphere

The discovery of Mercury's magnetosphere by Mariner 10 was surprising since the conventional view of regenerative planetary dynamos had been that the spin requirement would likely have been in excess of the observed spin rate of Mercury. Also internal fluid motions were not expected to be sufficiently large. This paper explores the alternative model of the formation of Mercury's magnetosphere via electromagnetic induction forced by the solar wind. It is shown, however, that the constraints are so severe as to limit severely the applicability of such a model. Although induction is easily observed on the Moon, the modification of the magnetic boundary condition associated with a plasma magnetosphere on Mercury rules out its formation via induction except for interplanetary driving fields which are decreasing in amplitude. That model is explored but retains the difficulty that induced magnetospheres tend to be of small radial and temporal extent compared to that inferred by Ness et al. for Mercury.     

Prediction of satellite motions in the Earth's gravitational field with axial symmetry by the KS regularized theory

In this paper, economical and stable recurrence formulae for the Earth's zonal potential and its gradient for the KS regularized theory will be established for any numberN of the zonal harmonic coefficient. A general recursive computational algorithm based on these formulae is also established for the initial value problem of the KS theory for the prediction of artificial satellites in the Earth's gravitational field with axial symmetry. Applications of the algorithm for the problem of the final state prediction are illustrated by numerical examples of three test orbits each for two geopotential models corresponding toN=2 andN=36. A final state of any desired accuracy is obtained for each case study, a result which shows the flexibility of the algorithm.