The magnetic structure in the source region of a type II burst and along the path of the type II disturbance has remained an enigma despite over 20 years of radio observations of the Sun (see e.g. reviews by Wild and Smerd (1972) and McLean (1974)). This paper describes the first radioheliograph observations of a type II burst near coronal magnetic structures depicted by soft X-ray pictures. It will be shown that three separate lanes in a type II burst are associated with three separate source regions each located almost radially above a soft X-ray loop. To explain these observations a model is derived in which a wide-fronted m.h.d. disturbance travels from the flare explosion along magnetic field lines and then intersects successively with three coronal streamer structures each located above a soft X-ray loop. An estimate of the magnetic flux density along the soft X-ray loops is obtained from the velocity of the m.h.d. disturbance.

Four catalogues based on the survey made with the Molonglo Cross-type radio telescope have so far been completed, the largest of which is MCI (Davies, Little and Mills,1973). These catalogues were noise limited and had a 5α lower limit of about 0.3 Jy. This paper gives an outline of deep surveys that have been made in order to reach significantly fainter sources, but only in a small solid angle of sky.

On 1975 August 22 an outburst above the west limb of the Sun was observed with the Culgoora radioheliograph at 43, 80 and 160 MHz. The first stages of the event included intense type III/V bursts followed by a type II burst with multiple, fundamental and harmonic bands and herringbone structure. While the type II burst was still in progress a moving type IV burst appeared. It was eventually observed out to a distance of more than 3 R⊙. This was the first moving type IV burst observed with the two-dimensional radioheliograph operating at three frequencies; as such it provides valuable constraints on models of moving type IV sources.

I will summarize briefly some results obtained from further studies of the Molonglo catalogues MC2 and MC3, centred approximately at declinations +11° and +16° respectively (Sutton et al. 1974).

It has been known for about 5 years that the flux densities at 408 MHz of some sources change over time scales of a few months, but discovery of these variable sources has been largely accidental during the intensity calibration of various observing programs at Molonglo. This paper describes some results from systematic observation of 254 sources over a 12 month period, through which we hope to better understand the telescope performance, find more identifications in the southern sky, and recognise variable sources. An improved calibration will be applied to digital data from Molonglo observations since 1967 (both surveys and individual source observations), now stored on magnetic tape.

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 energy passing through the boundaries of a convective zone in a star, in an outward radial direction per second, must in total be equal to the luminosity of the star, provided of course that this zone does not encompass nuclear energy producing regions. If, in an endeavour to establish the nature of the convective motions in this zone, a section of the zone is modelled by considering steady cellular convection in a horizontal layer of Boussinesq fluid, it is on the basis of an average energy flux being imposed. Moreover, the sum of the conductive and convective heat fluxes is represented by the Nusselt number, which is specified and constant for the zone.

Semiconvection is the name given to a situation that arises in the evolution of large-mass main-sequence stars and lower-mass horizontal-branch stars, in which a layer forms where almost all of the heat flux is transported by radiation, but where slow convection is required to redistribute a stably stratified solute (e.g. helium). For a general discussion on semiconvection, see Spiegel (1969). The main problem is to determine the correct relationship between the solute distribution and the temperature gradient in the inhomogeneous layer. Ledoux (1947) and Schwarzschild and Harm (1958) have proposed two very different prescriptions. Since theory and experiment indicate that the Schwarzschild-Harm (SH) prescription is correct for the onset of convection (in the form of overstability), Spiegel (1969) has proposed that SH are correct. However, neither observation (oceanographic or laboratory) nor theory precludes a substantial deviation from the SH prescription as applied to finite amplitude semiconvection. The observational evidence is only readily applicable to stars if Pr≳, 1, where Pr is the Prandtl number of the fluid. In fact, Pr≪ 1 in stars. It is shown below that if one could have stars in which Pr ≳ 1, then the SH prescription would probably be wrong, and the Ledoux criterion might then be nearer to being correct. In the real situation (Pr≪ 1), observations or experiments are lacking and theory alone does not provide an unequivocal answer to the problem. This paper does not attempt a complete discussion of the problem, and a more detailed report will be submitted elsewhere. Some aspects of the problem have already been discussed in the context of the giant planets (Stevenson and Salpeter 1977).

The deep interiors of cold, degenerate stars consist of a mixture of elements, either because of primordial inhomogeneities or because of incomplete nuclear burning. However, most existing calculations for the cooling of such bodies (subsequent to any nuclear burning) assume that the only source of luminosity is the heat content of the star. An additional (and potentially much larger) energy source is available if the elements have limited mutual solubility below some temperature. The resulting differentiation and gravitational settling can dramatically decrease the rate of cooling, enhance the number of (potentially) observable low luminosity bodies, and may deplete the atmosphere of heavy elements (if substantial mixing between the atmosphere and deep interior occurs). The observational evidence for these phenomena is equivocal at present.

A number of authors (Reddish, 1968, 1969, Reddish and Wickramasinghe 1969) have stressed the importance for star formation of the role of condensation of H2, onto solid grains inside the cool dark regions of a large interstellar cloud. However, although the thermodynamic consequences of the existence of grains have been extensively studied, the dynamical implications have received little attention. Solid grains of course do not possess a thermal pressure as their gaseous counterpart does, neither do they directly experience the magnetic fields which thread the ions and electrons of the gas cloud. The grains therefore, as soon as they are formed, are free to fall toward their common centre of mass, relatively unrestricted by the constraints on the gas cloud.

A major area of difficulty in the cosmogony of the solar system is understanding how a large number of small planetesimals, which have condensed from the primordial gas, can aggregate into the ordered planetary system present today. Theories involving aggregation within a gaseous disc [e.g. Cameron (1973)] suffer the common difficulty that the particles, once condensed, are no longer supported by the radial gas pressure gradient and spiral rapidly in towards the Sun. Most of the planetesimals are dragged in to the central body in times several orders of magnitude less than would be required for larger bodies to accrete (Goldreich & Ward 1973).

It is well known that the satellite systems of the major planets Jupiter, Saturn and Uranus share many of the same regular features that can be seen in the planetary system of the Sun. The inner satellite orbits are nearly circular and lie in the plane defined by the axis of rotation of the central body. Again the distances Rn of the regular satellites, numbered inwards to the centre n = 0, 1, 2, …, form a nearly geometric sequence

Rn/Rn + 1 ≌ constant,

similar to the Titius-Bode law of planetary distances. These facts suggest that the same cosmogonic process must have been responsible for the origin of both types of systems.

In discussions of the non-radiative propagation of energy through stellar atmospheres hydromagnetic waves, or in their more specialized form Alfven waves, have played an increasingly important role. Parker (1974) has suggested that they provide the cooling mechanism for sunspots, while Piddington (1974) has attempted to explain the flare energy supply in terms of hydromagnetic energy transport. While most analyses assume a homogeneous magnetic field extending to infinity in a compressible but unstratified atmosphere, it is important to remember that most astrophysical plasmas are gravitationally stratified and that the magnetic fields are highly inhomogeneous, exhibiting a variety of different structures.