Observations of Jupiter’s decametric radio burst have established that above 20 MHz more than 90% of the emission is elliptically polarized in the RH sense, but below this frequency the proportion of the LH polarization increases (Sherrill 1965) until at 10 MHz nearly 40% of the emission is LH polarized (Dowden 1963). The best time and frequency resolutions so far obtained when examining the polarization of the spectra of Jupiter’s bursts have been 10 ms and 50 kHz respectively (Gordon and Warwick 1967, Riihimaa 1975). To study the fine structure of Jupiter’s emission as observed by the linearly polarized Llanherne low frequency radio telescope (Ellis 1972), spectrum analysers with resolutions in the ranges 0.3 — 1 msec and 2–10 kHz have been used (Ellis 1973a, 1973b, 1974, 1975). A new telescope at Llanherne, which is capable of detecting the RH and LH circular components of incident radiation, is being used in conjunction with these analysers to yield information of the hyperfine polarization structure of Jupiter’s decametric radio emission. This paper is a preliminary report of this investigation.

A long-standing problem in the theory of astrophysical accretion disks has been to determine the nature of the stress that transports orbital angular momentum outward. The discovery of a local MHD instability is strong evidence that transport occurs through turbulent Maxwell and Reynolds stresses. Using numerical simulations, we have demonstrated that a weak seed magnetic field in an accretion disk shear flow is unstable and leads to sustained MHD turbulence at dynamically important levels.

It was first pointed out by Hoyle et al. that quasars if they are indeed located at cosmological distances, must be characterized by an extraordinarily large radiation density : and therefore, though their optical and near infra-red spectra appear to be dominated by synchrotron radiation, any ultrarelativistic electron present must necessarily lose essentially all its energy by inverse Compton scattering. This would mean that, though quasars are emitting fantastic amounts of energy at optical frequencies, they must also be emitting many orders of magnitude more at X-ray and γ-ray frequencies. This paradox has been evaded by several specially constructed models (e.g. Rees and Sciama, Woltjer and Jukes); but the problem has not been removed in general.

The purpose of this paper is to review current and planned Space Astronomy missions from an international perspective, with principal attention to the programs of the USA, Europe, Japan and the USSR. The review focusses on extra-solar astrophysics, and the capabilities and broad research objectives of numerous individual spacecraft are described. These collectively span more than seventeen decades in wavelength and thus provide an essential complement to ground-based astronomy. Many of the missions offer significant opportunities for Australian participation via three complementary routes. First through Guest Investigator programs analogous to that offered for the Hubble Space Telescope (HST). Second, through the proposed establishment of an Australian Space Astronomy Data Centre to gain access to archival data from HST and other missions (the creation of such an archival facility in Canada is highlighted as a pertinent example). Third, via the contribution of instrumentation or ground support services. This latter category includes the Radioastron VLBI mission for which an agreement with the USSR has already been signed. In addition, an unprecedented opportunity has arisen for Australia to provide a ground station for the Infrared Space Observatory (ISO), due to be launched by ESA in 1993. In return for providing this service, the Australian astronomical community would receive a guaranteed share of the ISO observing time during the two year mission. Finally, Australian astronomers have been invited to contribute an advanced All-sky X-ray Monitor for the Soviet Spectrum-X-Gamma mission in 1993. This opportunity, and also the Radioastron initiative, have arisen under the USSR-Australia Space Research Agreement signed in December 1987.

Shock drift acceleration of the electrons which produce herringbone structure in type II bursts is considered. A non-coplanar component of the magnetic field within the shock front and an electric field across the shock are taken into account. A quantitative difficulty with shock drift acceleration is identified, and possible ways of overcoming the difficulty are outlined.

The present Astronomy Advisory Committee (AAC) was set up by the then Minister for Science and the Environment, Senator J. J. Webster, in July 1979 following a Government review of astronomical facilities carried out by an interdepartmental committee (IDC) in 1978-1979. The IDC was assisted by an expert sub-committee, whose report Review of Observatories (1978) has since been published. The AAC consists of a chairman and ten members drawn from the astronomical community in Australia. It is serviced by the Department of Science and the Environment.

Although the maser hypothesis for anomalous OH emission encounters difficulties it has not been seriously questioned because, as pointed out by Turner, no alternative has been available. The following ideas might suggest that there is an alternative hypothesis for anomalous OH emission.

Scattering of radiation from solar radio sources by in homogeneities in the electron density structure of the corona can have marked effects on the observed time profile and the brightness distribution. These effects are appreciable for any localized source emitting a brief burst of radiation and are most pronounced when the radiation propagates close to the plasma level; it is such sources, illustrated here by those of type III bursts, that will be considered in this paper.

Dissipation of shock waves has often been proposed as the energy source required to sustain the outward temperature rise in the solar atmosphere. Theoretical models for the heating process have been developed by equating the mechanical energy input to the radiative energy loss at each height, but neither of these processes is well understood, and the lack of data means that the models are necessarily crude.

Baade (1963) pointed out three regions of low obscuration in the general direction of the galactic centre, wherein a stellar population assumed to be characteristic of the galactic bulge could be studied.

Improved solutions have been obtained for the orbit and equatorial cross-section of Mercury using radar ranging data spanning 22 years. These data have yielded new results on the precession of Mercury’s perihelion and better limits on a possible time variation in the gravitational constant G.

Individual pulses from a given pulsar can differ greatly in both shape and intensity, and are often made up of narrower ‘subpulses’, i.e. local emission peaks one tenth the width of the mean pulse. Properties such as shape, polarization and position of subpulses presumably reflect details of the emission processes and of the regions that produce the radiation.

The Parkes radio telescope has been used to search a list of small, dense southern dark clouds and Bok globules for ammonia emission at 23.7 GHz. The ammonia observations, together with IRAS data and the cloud’s visual appearance, have been used to determine a short list of dark clouds for observation with the infrared imaging system (IRIS) on the Anglo-Australian Telescope, in an attempt to determine the dust density distribution within the clouds. Near-infrared images of a number of the short listed clouds have been obtained with IRIS at J, H and K’. Preliminary results are reported for this ammonia survey, together with IRIS images of the strong ammonia source DC 297.7–2.8. Coincident with the dense ammonia core of this object is an IRAS ‘core’ source, IRAS 11590–6452 and an extremely interesting near-infrared source, which lies on the edge of the error ellipse of the IRAS source.

It has been accepted since the mid-1950’s that the LMC is a flat rotating body, with its plane inclined at an angle of about 27° to the line of sight and so nearly face on, and its line of nodes running 10° west of north (de Vaucouleurs and Freeman 1972). The inclination is inferred from the ellipticity of the outermost optical and radio isophotes but there has been no convincing way to fix its sense — whether the E or W side is nearer. Some years ago the late Dr David Thackeray suggested to one of us (SCBG) that this could be done by comparing the magnitudes of cepheids on the extreme E and W sides of the Cloud. With the discovery of the Magellanic Stream and the great increase of interest in the spatial geometry and dynamics of the Clouds and Galaxy complex, the sense of the tilt of the LMC has become a matter of importance, and we decided to go ahead with the project.

Evidence exists for mode energy changes in beat Cepheid variable stars over the 20-30 year interval during which photoelectric observations of the objects have been obtained. For TU Cas, Hodson, Stellingwerf and Cox (1979) have found that the first overtone amplitude has been decreasing with time from 0.4 to 0.25 mag over a 67 year timebase; these authors also included some early visual estimates in their analysis. For U TrA, Faulkner & Shobbrook (1979) have found that the first overtone pulsation has been increasing relative to the fundamental over a twenty year timebase.

The U.K. 1.2 metre Schmidt Telescope acquired its first full aperture objective prism in 1975. This was a very low dispersion prism (2400 Å/mm at 4300 Å) which has been found to be particularly useful in searching for faint QSO’s.

In this paper we model mathematically the propagation of galactic cosmic-rays in the solar cavity and study the effects of changing the physical parameters; in particular the radius of the cavity. We assume spherical symmetry with heliocentric distance r, momentum p and work in terms of F0(r, p) the mean distribution function with respect to momentum; it is related to JT the mean differential intensity w.r.t. energy by JT = p2F0 . The boundary is at r = rb beyond which the galactic spectrum prevails; there is free escape of particles incident on rb from within, and the distribution is steady state.

The effective Rayleigh number, in the solar convection zone, soon reaches a value of the order of 106 and, although considerable progress has been made in the numerical integration of the basic system of differential equations at high Rayleigh number, it is of interest to investigate more fully the application of asymptotic methods to such a problem.