Generation of 1–30 Hz waves near the plasmapause by resonant electron-instability

A generation mechanism for 1–30 Hz waves of the second category, observed near the plasmapause by Taylor and Lyons (1976), is suggested in terms of a resonant electron instability. The instability arises because of the resonant interaction between the ring current electrons outside the plasmapause and the ordinary mode drift waves. The instability can generate waves in the frequency range from 0.45 to 35.0 Hz in the region between L = 4.5 and 5.5. The instability can also explain satisfactorily the other properties such as no changes in the proton distributions, the direction of the wave magnetic field and the localization of the region of wave activity, associated with these waves.     

Light curve analysis of the short period eclipsing binary RT and

We have analysed the 1978 UBV photoelectric observations of the short-period (RS CVn type) binary system RT And, using the rectifiable methods of Russell and Merrill (1952) and Kitamura (1965). The primary minimum is a transit. The solutions allow us to classify the system as a detached one, but a certain disagreement results with respect to solutions of previous epochs. A graphical test of the reliability of the solution is given.     

Cosmic ray ionization of the Jovian atmosphere

An approximate form of the Boltzmann equation has been used to obtain local ionization rates due to the absorption of galactic cosmic rays in the Jovian atmosphere. It is shown that the muon flux component of the cosmic ray-induced cascade may be especially importannt in ionizing the atmosphere at levels where the total number density exceeds 10¹⁹ cm^?3 (well below the ionospheric layers produced by solar euv). A model containing both positive and negative ion reactions has been employed to compute equilibrium electron and ion number densities. Peak electron number densities on the order of 10³ cm^?3 may be expected even at relatively low magnetic latitudes. The dominant positive ions are NH₄⁺ and C_nH_m⁺ cluster ions, with n ? 2; it is suggested that the absorption of galactic cosmic ray energy at such relatively high pressures in the Jovian atmosphere $\text{(M ? 10}{}^{18}\text{to}\text{10}{}^{20}\text{cm}{}^{\mathrm{?3}}\text{)}$ and the subsequent chemical reactions may be instrumental in the local formation of complex hydrocarbons.     

Estimation of coronal magnetic field from razin effect in solar decametric continuum burst

A solar flare of importance 1B which occurred at 06:36 UT on April 27, 1979 on the solar disk (N 20, E 16) produced intense radio bursts. The most interesting feature of this event is the observation of a strong continuum radiation (type IV) starting at 06:53 UT and lasting for about 10 min in the decametric range. This continuum radiation displayed sharp low frequency cut-off, which varied from about 40 to 30 MHz in a quasiperiodic manner and could be attributed to Razin effect. The perturbation of this cut-off frequency is interpreted as that induced by the passing MHD shock wave through the region of the trapped energetic electrons. Assuming model electron density values and using the observed cut-off frequency, the magnitude of coronal magnetic field around 2R from Sun center works out to be about 6 G.     

On transfer equation in a semi-infinite atmosphere with albedo ω>1

In this note we derive an exact solution of transfer equation in a plane-parallel semiinfinite atmosphere with albedo >1, by the method of Laplace transform and Wiener-Hopf technique. The emergent intensityI(0, ) is obtained in terms of theH ⁰-functionH ⁰() (Das Gupta, 1978) for which some good approximations are given. Intensity at any depth is also obtained.I(0, )/I(0, 0) is plotted in graphs against [0,1], and shows a maximum which drops and shifts towards the origin as increases.     

Numerical simulation of the final stages of terrestrial planet formation

Three representative numerical simulations of the growth of the terrestrial planets by accretion of large protoplanets are presented. The mass and relative-velocity distributions of the bodies in these simulations are free to evolve simultaneously in response to close gravitational encounters and occasional collisions between bodies. The collisions between bodies, therefore, arise in a natural way and the assumption of expressions for the relative velocity distribution and the gravitational collision cross section is unnecessary. These simulations indicate that the growth of bodies with final masses approaching those of Venus and the Earth is possible, at least for the case of a two-dimensional system. Simulations assuming an initial uniform distribution of orbital eccentricities on the interval from 0 to e_max are found to produce final states containing too many bodies with masses which are too small when e_max < 0.10, while simulations with e_max > 0.20 result in too many catastrophic collisions between bodies thus preventing rapid accretion of planetary-size bodies. The e_max = 0.15 simulation ends with a state surprisingly similar to that of the present terrestrial planets and, therefore, provides a rough estimate of the range of radial sampling to be expected for the terrestrial planets.     

On the albedo of the interplanetary dust

The zodiacal light brightness and measured spatial density of the interplanetary dust lead to a mean geometric albedo of 0.24 for the dust particles near 1 AU; whereas the composition of collected micrometeroids suggests a geometric albedo ?0.1. The data do not support the very low albedo (?0.01) proposed by A. F. Cook [Icarus33 (1978), 349–360]. The evidence is against a change in the mean particle albedo between 0.1 and 2 AU. Beyond 2 AU the data are unclear and a change in albedo is not ruled out.     

The evening diffuse radio aurora,field-aligned currents and particle precipitation

The relationship of the afternoon/evening diffuse radio aurora, proton and electron precipitation and field-aligned currents is studied with data from the auroral radar at Slope Point, New Zealand, and the ISIS 2 satellite. It is shown that there is a very close association between the radio aurora and (primarily downward) field-aligned currents, which confirms and extends previous work, but that there is no clear relation with either proton or electron precipitation.     

Instability of a streaming jet under the influence of vacuum magnetic fields

The magnetohydrodynamic stability of a streaming liquid cylinder subject to surface tension and pervaded by a magnetic vacuum field has been elaborated for all axisymmetric and non-axisymmetric disturbances. The dispersion relation is obtained and studied analytically and numerically. the streaming has always a destabilizing effect. The axial magnetic fields inside and outside the jet have always stabilizing effects for all perturbations. The transverse magnetic field has a destabilizing effect. However, if the axial field intensity is so high and paramount over that the transverse field, the destabilizing character of the model is suppressed. The latter is satisfied if the Alfvén wave velocity is greater than the equilibrium liquid velocity.     

Effect of shallow and narrow water on added mass of cylinders with various cross-sectional shapes

The sway, heave and roll added masses of three uniform cylinders with semi-circular, rectangular and triangular cross-sectional shapes in shallow and narrow water are numerically analysed. The method is based on simulation of the potential flow induced by the cylinder's mode of motion. The effects of shallow and narrow water on added mass are analysed and presented. It is concluded that the shallow and narrow water effects on added mass depend on the different cross-section shapes of the cylinders. In particular, the water depth effect on sway added mass is stronger than that on heave added mass while the narrow water effect on sway is weaker than that on heave. The shallow water effect on added mass tends to weaken the narrow water effect. Lastly the effect of shallow and narrow water on added mass on a rectangular cylinder is the strongest while that on a triangular cylinder is the weakest.