The numerical solution of the basic equations for non-linear steady convection in the weak-coupling approximation is exceedingly difficult. In astronomical applications the Rayleigh number R will be of the order of1012, and we wish to report here some results obtained in the case of high Rayleigh numbers with the use of an asymptotic method.

The equation of motion, derived from the basic Lagrangian equations for the conservation of momentum and the conservation of energy, for non-linear non-adiabatic radial oscillations of a pulsating star takes the form

Ground level detectors observed several major changes in the primary cosmic-ray flux during November 4960. Large increases, of solar origin, occurred on November 12 and 15, and a smaller one on November 20. The galactic flux in the region of the Earth was severely reduced by a Forbush decrease on November 12, and remained notably depressed until November 25. Considerable magnetic activity was observed throughout the period. Several models have been proposed to account for these observations.

At present there are two general theories of the origin of cosmic rays. One is that most, if not all, galactic cosmic rays originate within the Galaxy, probably during supernova explosions. The other is that cosmic rays pervade the universe, originating mainly in the powerful radio galaxies and possibly in quasars, where vast stores of energy are available. The former theory has been discussed in detail by Ginzburg and Syrovatskii, while proponents of the latter theory include Burbidge and Hoyle, and Burbidge.

Recently a programme of observing 21 cm-λ solar radio bursts with high angular resolution has been commenced at the Fleurs Radio Field Station of the School of Electrical Engineering, University of Sydney. In some preliminary measurements fringes from two 2-element E-W interferometers, spaced at roughly 3800 and 1900 wavelengths, have been recorded simultaneously.

Recent observations of the radio-frequency flux spectrum of Jupiter in the frequency range 80-10 000 MHz suggest that the synchrotron component is not independent of frequency as has been generally accepted. Rather, the flux decreases at frequencies below 300 MHz and above 3000 MHz. In this paper we show that extensions and variations of the well-known dipolar model for this emission can account for the modified spectrum.

The only planet with observed secular motion between the body and the axis of rotation is the Earth itself, which rotates both progressively and with unexplained librations about equatorial axes.

It has recently been shown that the planet Mercury exerts a small control on relative sunspot numbers, the degree of control depending on the positions of the other planets.

This paper describes the results of extending the work to include all the planets.

As a working hypothesis we have assumed that gravitational tidal forces induced on the Sun by the planets may modulate solar activity and have accordingly calculated relative equilibrium ‘high tide’ displacements of the solar surface for each day from the positions, masses and distances of the first six planets. Although the tides are very slight, the mass of displaced material is appreciable and varies over the very wide range of nearly 5 to 1.

A morphological comparison between radar meteor survey data obtained at Ottawa (Millman and McIntosh, 1964) from 1958 to 1962 and that obtained from Christchurch (Ellyett and Keay, 1963) in 1960-61, confirms that the Daytime Arietid, Delta Aquarid meteor shower association is the most prominent feature of the annual activity. The data from Canada and New Zealand are easily reconciled as far as this activity is concerned and also for the weaker Eta Aquarid shower which, having a radiant at zero declination, is equally prominent in both sets of data. Furthermore, the data from both hemispheres is consistent with a forty per cent increase in overall activity during the second half of the year.

We have recently used the atmospheric air-shower Cerenkov technique in an attempt to observe pulsed gamma radiation from two southern pulsars, PSR 0833—45 and MP 0959. Northern hemisphere observers do not agree whether the pulsars CP 0950, CP 1133 and CP 1919 are sources of gamma emission, either pulsed or uniform in time.

The first daily maps showing the two-dimensional radio brightness distribution over the Sun were produced at Fleurs ten years ago when the 64-antenna grating cross was completed. The maps had a resolution of 3′ arc at λ = 21 cm.

When the Fleurs field station was given to the University by CSIRO in 1963 it was decided to use the antennas of the grating cross and add to them four or more larger antennas (45 ft diameter) to produce a pair of high resolving-power compound interferometers.

The purpose of this paper is to obtain an expression for the reflecting properties of a semi-infinite, plane parallel, isothermal atmosphere of scattering factor λ. The absorption and scattering of the incident radiation is assumed to be entirely due to transitions in two-level atoms, and the absorption and emission profiles are given by <f>(y), y being frequency from line centre in Doppler units.

During the interval May 1968 to March 1969 the 80 MHz radioheliograph at Culgoora has been used in a detailed study of the intensity variations in the pulsars CP 0834, 0950, 1133 and 1919. Some preliminary results for CP 1133 and 1919 have already been reported.

This paper is a progress report on an examination of the short-term variability of solar proton flux in interplanetary space at times of solar flare activity. The data are from the GRCSW cosmic-ray detector on board the Pioneer 7 space probe, which, at the times to be discussed, was more than a million miles from the Earth.

Those solutions which have so far been obtained to the problem of a star with both rotation and a magnetic field have been for certain special cases, mostly time-independent. It is known that, except for stars with special rotation laws, a rotating star in hydrostatic equilibrium cannot maintain thermal equilibrium without generating slow meridional circulation of matter. It is also known that an axially symmetric field with no azimuthal component tends very strongly to keep the star in a state of isorotation, with the angular velocity constant along field lines. A magnetic field also tends to upset thermal equilibrium and produce meridional circulation. In the absence of rotation, an equilibrium poloidal field has recently been found for which there is no circulation. The present paper reports analogous equilibrium solutions for a star which is in uniform rotation.

Recently I have carried out a two-dimensional radiative-transfer analysis of the data given by Edmonds on centrelimb relative rms intensity fluctuations in terms of horizontal temperature fluctuations in the solar photosphere. Edmonds himself attempted an analysis of his data and found a ΔTrms which increased monotonically from about 300°K at unit mean optical depth (i.e. at a given physical depth) to 500°K at optical depth 3.

The compound interferometer at Fleurs, N.S.W., consists of the separate arms of the Christiansen grating interferometer with the addition of two 45-ft dishes to each to give maximum spacings of 3710λ at 1415 MHz. The closest physical spacing is 60 ft and the spacings progress at 40-ft intervals to a maximum of 2580 ft as shown in Figure 1.

Since 1957, the University of Tasmania has operated cosmic-ray meson telescopes at an underground site near Hobart for the purpose of monitoring the intensity variations in the high energy component of the primary flux near the Earth. Details relating to the site, equipment, and meteorological influences on the observed intensity have been given previously. At a depth equivalent to 36m of water (36 m.w.e.), the equipment responds to an effective primary spectrum having a mean particle energy in the vicinity of 200 GeV and falling off rapidly at low energies, so that about 90% of the primaries have energy exceeding 50 GeV. The corresponding mean energy of response for surface muon telescopes at Hobart is about 25 GeV, while a neutron monitor at Hobart has a mean response at about 7 GeV.

We consider the effect of a velocity gradient on the source function for a spectral line formed in an atmosphere in non local thermodynamic equilibrium, a problem examined previously by Kulander and Hummer and Rybicki. A numerical method is used which extends the Feautrier technique.

While monitoring Barnard’s star in Ophiuchus for flare activity in August 1969, we accidentally recorded two bright flares on an early type star, 66 Oph. Apart from Andrews’ unconfirmed observation of a flare on a B8 star and Eggen’s report of a flare on the β Cephei Variable, (BO) HD 199 140, no other record of an early type flare star is known to the authors.