A comprehensive study of the anisotropy (i.e. streaming) of solar cosmic rays at energies ~10 MeV revealed two distinct types (McCracken). The first occurs during onset phase of the event, is large (> 20%), and is really the flow of cosmic rays along lines of force driven by a density gradient. The second describes the decay of the event, is small (10%), and indicates a flow radially away from the Sun.

During the period 1966 July 12 to August 5 observations were made of the Sun at three radio observatories. The instruments used were the east-west arm of the Mills cross at Molonglo (408 MHz) and the Christiansen cross at Fleurs (696 MHz and 1424 MHz). The aim of these observations was to study the discrete sources of the slowly varying component of solar radio emission, while activity was comparatively quiet. The three frequencies enabled the variation of source structure with height of solar atmosphere to be studied. It has been pointed out by Swarup et al., and Christiansen et al. that the determination of the frequency dependence of these discrete sources is important for defining the physical mechanisms causing the radio emission.

Since the start of high-resolution observations with the radioheliograph at the Culgoora Solar Observatory it has been noted that some bursts which occur from separate active regions could be physically correlated. It was suggested that the time delay between the correlated bursts is of the order of seconds, and that fast electrons provide the trigger. Wild found that shortly before a large flare weak bursts, stronelv polarized in the same sense, appeared simultaneously in different sources after a quiet period and he discussed the phenomenon in the light of flare mechanisms.

Recent two-dimensional observations of the quiet sun at 80 MHz by Sheridan showed a persistent low-intensity source (radio enhancement) whose daily motion was consistent with a source at radius 0.95 R® rotating with a synodic period of 27.3 d. In this paper we shall attempt to interpret this result in terms of the effects of refraction and opacity in model coronas. Comprehensive studies of the Sun at 169 MHz show that similar radio enhancements are associated with coronal streamers and that reasonable values for electron density and temperature within the coronal streamer allow the observations to be explained in terms of thermal radiation. Hence we shall consider only coronal models that possess streamer structure. We shall show that temperature enhancements within the streamer (‘thermal model’) do not lead to an apparent radius as small as that observed by Sheridan and that his observation may be better understood in terms of a non-thermal model for radiation from the streamer region.

This paper presents a progress report on a programme of infra-red photoelectric photometry of the red giant sequences in some southern globular clusters. As measured in B and V these sequences are known to differ from cluster to cluster, at least one contributing factor being differential line-blanketing arising from variations in metal abundance. Observations in R and I should be substantially free of blanketing, and so enable us to eliminate this factor, clarifying the situation and making possible a more accurate transformation of the observations to the Mbol, log Tett plane. The difficulty of making this transformation has been a major obstacle in comparing observations and theory for cluster giants.

Detailed observations of the importance 2 flare of 9 June 1968, 00h25m U.T., were made at Culgoora in both its Hα and 80 MHz radio emissions, and the event should provide an opportunity for careful study. In this paper a description is given of the radio spectral observations (25-200 MHz) taken at the same site. These observations were among the first to be taken with a newly constructed spectrograph.

Over the past years considerable information has been acquired concerning the structure and magnitude of sunspot magnetic fields; however, there is a paucity of data concerning the motions of the seats of these fields, i.e., individual umbrae within a spot group. The well-known effects of differential rotation cause sunspots to diverge with time in longitude at a daily rate of, at most, a few degrees per solar rotation. On the other hand, a limited number of investigations have shown that individual umbrae can have proper motions of up to 100 to 200 m/s, or about ten times greater than effects of differential rotation. In addition, equally limited observations have shown that umbrae sometimes rotate about an axis through their centre; in an extreme case the rotation reached 30°/day. The last large sunspot group of the last cycle, having Central Meridian Passage 20.5 September, 1963, has been studied by means of photoheliograms and magnetograms obtained four days before and four days after CMP at the Crimean Astrophysical Observatory. The magnetograms show the distribution of both the transverse and longitudinal components of the magnetic field in the activity region. In this study we have studied umbral motions and their relation to the magnetic field.

Prior to the advent of the Culgoora 80 MHz radioheliograph position measurements on type II solar bursts were restricted to those made with one-dimensional interferometers. These measurements yielded conflicting evidence on the apparent positions of fundamental and harmonic emission observed at a given frequency; different observers reported the fundamental to be closer to and further from the centre of the Sun than the harmonic. Here we report on two-dimensional observations at 80 MHz made on both fundamental and harmonic emission of a type II event that occurred on 1969 March 2. The observations are shown to be consistent with the hypothesis that the emission is produced as the result of a disturbance moving out from the site of a flare and forming a shock front within an overlying coronal streamer. Both fundamental and harmonic are explained by ‘forward’ emission from the shock front. Observations of the harmonic emission at 158 MHz are also consistent with this model.

A coudé spectrogram of dispersion 150 µ/Å, exposed at the 74-inch reflector by D. S. Mathewson, reveals very many unusually sharp absorption lines due to ionized metals in the atmosphere of the B9 star HD 1909.

With a number of important exceptions associated with transitory flare activity, most persistent sources of solar radio emission observed to date with the 80 MHz Culgoora radioheliograph have been stable in position over periods of tens of minutes or hours even though they fluctuated greatly in intensity. During several hours on 1968 November 11, however, we observed some interesting activity which showed frequent changes in the position of a source.

I am reporting here work done recently by the astrophysics group at the University of Queensland (notably G. D. Finn and R. L. Young). We are interested in the detailed formation of the profiles of the sodium-D solar absorption lines. These lines are very strong with extended wings and the object of the exercise is to determine how closely, under the physical conditions assumed to exist in the solar atmosphere, we can theoretically reproduce the detailed line profile which is observed.

A moving type IV radio source on 1970 March 21 was observed with the 80 MHz Culgoora radioheliograph to move out to a distance of p = 6 (where p = R/R®). Starting as a single source of complex shape it later developed strong circular polarization (> 90% R.H.) and separated into components which retained the same polarization. The source appeared soon after a prominence eruption (or flare spray) from which some of the ejected matter travelled in the same direction as, and with a velocity close to, that of the radio source.

Travelling disturbances in the solar corona with velocities ~103 km/s manifest themselves at radio frequencies by two distinctive phenomena—the type II burst, the spectrum of which shows a slow frequency drift that corresponds to quasi-radial outward motion, and the moving type IV burst, for which positional observations show transverse motion directly. A close relation between the two phenomena has long been suspected, and each type has separately been ascribed to a shock wave disturbance. In this paper we summarize three events recorded by the Culgoora radioheliograph and spectograph (two in the course of publication and one unpublished) in each of which a type II and a moving type IV burst can be consistently attributed to the effects of a common shock wave.

Radio pictures of the Sun from the Culgoora radioheliograph have already shown instances in which flares have initiated radio bursts in parts of the Sun remote from the flare position. In this paper we discuss two such events on 1968 May 4 and May 6, in each of which it appears that shock-waves arising from a flare produced distant prominence activity which led to the generation of metre-wave continuum radiation.

Of the metre-wavelength solar radio bursts which have been recognized, those of type II are characterized by the most complex set of spectral features. Apparently acceptable explanations have now been put forward for most of these features. However, not all these explanations can be considered to be established. In particular the phenomenon of band splitting has been explained in different ways by Sturrock, by Tidman et al., by Zheleznyakov and Zaitsev. However, the theories of Sturrock and Tidman apparently require magnetic fields so strong as to preclude the formation of a magnetohydrodynamic shock wave by a disturbance moving at the velocity (<~ 1000 km/s) attributed to type II bursts. The same problem is encountered in other earlier theories of band splitting involving magnetic effects. The other theory does not involve the magnetic field strength. However, the details of this theory do not appear to have been properly worked out as yet.

Significant evidence for a bi-directional sidereal anisotropy has been obtained from observations with meson telescopes at depths in the vicinity of 40 metres water equivalent (m.w.e.) underground. The anisotropy is of the type which should occur when charged particles which were formerly isotropic stream equally in both directions along a magnetic field, if there is a tendency for pitch angles to become reduced (the pitch angle being the angle between the particle trajectory and the direction of the field). If the magnetic moments of the particles are adiabatically invariant, changes in the magnetic field, both with position and time, could be responsible for the anisotropy.

Since they were first interpreted, moving type IV bursts have been attributed to synchrotron radiation from electrons with energy ∼3 MeV radiating in weak magnetic fields (∼1 G) high in the solar corona. In this paper a description is given of 80 MHz radioheliograph observations of an outburst in which it was possible to isolate the moving type IV source and demonstrate that its circular polarization was strong (∼80%). Hence it is shown that the energy of the radiating electrons cannot exceed 6 = 105eV.

It has become recognized that the dominant mechanism in the formation of the cores of resonance lines in the solar spectrum is non-coherent scattering, e.g., Thomas (1957). A study, preliminary to the theoretical investigation of the spectra of chromospheric structures, is the evaluation of the effect of diffuse reflection and transmission by non-coherently scattering media.

The stellar interferometer at Narrabri Observatory measures the angular diameter of hot, bright stars. It does this by matching the observed intensity correlation from two detectors, as a function of separation between the detectors, with that from a uniform disk (see Hanbury Brown et al.). When this measurement is taken in conjunction with experimental determinations of the monochromatic flux received at the Earth, the effective temperature of the star, Te, can be determined. However, if the star being observed is rotating rapidly, comparison with a uniform disk is of doubtful validity. Owing to its rotation the shape of the star will be distorted, and its effective temperature will vary over the surface (being apparently hotter at the poles). Therefore the measured angular diameter of the star will be different, and will change with the orientation of the star’s axis of rotation in the sky.

During the past year we have investigated 72 regions in the galactic plane at 408 and 5000 MHz using the Molonglo and Parkes radio telescopes, respectively.