It is generally agreed that T-Tauri stars are very young stars of solar mass which are still engaged in the process of gravitational contraction toward the main sequence (Ambartzumian, Herbig).

The necessity of having accurate oscillator strengths in astrophysical applications is well known. The apparent discrepancy which existed between the solar and meteoritic abundance of iron is just one example of the problems which can arise from poor f-values. An excellent critique of methods for determining both absolute and relative f-values has been given by Blackwell & Collins (1972). Their comments on life-time techniques provide a clear indication of both the advantages and difficulties associated with these techniques: “In principle, a life-time method, as exemplified by the technique of beam foil spectroscopy, described for example by Wiese (1970), has the fundamental advantage that in some restricted circumstances its application does not depend upon a temperature measurement or any assumption of themodynamic equilibrium in the source: in addition it gives an absolute result without the need of an absolute number density of atoms. The hope is sometimes expressed that the method of beam foil spectroscopy will yield oscillator strengths of the required accuracy. In practice, the technique suffers from the difficulty that although the life-time of an excited state can be measured with reasonable accuracy, it is also necessary to measure in a separate experiment the branching ratios for radiative de-excitation. As these ratios are usually measured by an arc method, the accuracy of the final oscillator strengths is limited by the deficiencies of this source. Also, some atoms in the beam may be excited to higher levels than the one being examined, and because of the nature of the initial excitation is unknown, radiative de-excitation (cascading) takes place to this lower level in a way that is wholly unpredictable. This difficulty is especially important for levels of low excitation.” In this talk techniques will be described for overcoming the cascading problem in beam foil spectroscopy and for measuring the associated branching ratios.

I shall briefly outline some observational aspects of the Magellanic Stream before discussing the pros and cons of the two conflicting theories of its origin: a) that the Stream was pulled out of the Clouds by tidal forces produced by a close encounter with our Galaxy and b) that the gas clouds of the Stream are primordial and in the same orbit as theMagellanic Clouds.

Time dependent solutions of the nonlinear modal equations for cellular convection in a fluid layer heated below have demonstrated the existence of a nonlinear bifurcation which leads to a stable regime with reduced heat flux and vertical velocities. This new state is brought about by the growth, to a significant level, of the vertical component of vorticity after an initial quasi-steady state has been established. The growth rate mechanism has been investigated analytically and compared with the numerical results. These vorticity modified solutions exhibit favourable features Which could be established in the solar convection zone.

Although cosmic rays detected in interplanetary space have often been correlated with visible flares at the Sun, little is known about the transport of these particles through the corona. Lin demonstrated a good correlation between ≳20 keV electron events detected by spacecraft near the Earth and type III radio bursts at the Sun. In a detailed investigation of many of these electron events from one particular active region source, Lin proposed that the injection of electrons was characterized by a source region in the corona which extended over ~70° in longitude, such that in this region the electrons had direct access to an ‘open cone’ of propagation in interplanetary space. When the spacecraft was situated outside this open cone (by up to 15°), impulsive electron events were still recorded, but these were now modified by diffusion through the corona of the electrons from the 70° source region.

Who discovered QSOs? What was the first QSO discovered? To Maarten Schmidt (1963) goes the credit for realising that the emission lines he saw in a 13 mag star were the Balmer series in hydrogen at a redshift of 0.158. The first QSO had been recognised. But discovery is a complex process. Schmidt observed the ‘star’ because it was associated with a radio source 3C 273 by means of an accurate radio position. This was the first of several instances where accurate radio positions have enabled significant progress in the QSO story.

Theoretical work on the radio emission from supernova remnants (SNRs) has not developed much since the pioneering work of Shklovsky (1960) and van der Laa (1962a, b). Despite agreement that the emission results from the synchrotron process, the origin of the relativistic particles and magnetic field is not clear. There are three reasonable alternatives:

1. (i) particles and field originate within the ejected material (e.g. Shklovsky 1960);

2. (ii) both field and particles originate in the compressed interstellar medium (e.g. van der Laan 1962a);

3. (iii) the field is interstellar but the particles are from the ejecta (as outlined by van der Laan 1962b).

We have simulated numerically the hydrodynamic cooling process after the maximum phase of a solar flare with improvements on the chromospheric radiative loss and the resolution of the transition region, together with the introduction of the mechanism of chromospheric heating by coronal soft X-rays. The main results are as follows:

1. 1. At the early stage of the gradual phase, thermal conduction maintains chromospheric evaporation, but with the cooling of the atmosphere, chromosphere evaporation decreases gradually.

2. 2. In most of the gradual phase, the velocity is smaller than 40km s−1 in the corona and 4km s−1 in the chromosphere.

3. 3. From the middle stage of the gradual phase, the coronal atmosphere appears to have a quasi-periodic oscillation. The period is about two minutes, and the amplitude of velocity is within ±20km s−1.

4. 4. The transition region continues to move downward at first and then changes very slowly for quite a long time. The upward motion of the transition region takes place only at the latest stage, when the atmosphere cools below the quiet-Sun case.

5. 5. In contrast to the changes of temperature, the density of the corona does not seem to vary until the violent descent of coronal material takes place at the end of the gradual phase.

6. 6. The coronal part cools mainly by thermal conduction, while the chromospheric part cools by radiative loss. With our initial model, it takes about 25 minutes for cooling from the maximum phase to nearly the quiet-Sun case.

7. 7. The soft X-ray heating of the chromosphere seems to be of negligible importance in our calculations, but if the coronal density is greater than 1011 cm−3 at the maximum phase of the flare, the soft X-ray heating may play some role in the gradual phase.

8. 8. At the latest stage of the gradual phase, the atmosphere remains dense and at low temperature. As a further consequence, it would evolve into a post-flare loop.

During 1990 we surveyed the southern sky using a multi-beam receiver at frequencies of 4850 and 843 MHz. The half-power beamwidths were 4 and 25 arcmin respectively. The finished surveys cover the declination range between +10 and −90 degrees declination, essentially complete in right ascension, an area of 7.30 steradians. Preliminary analysis of the 4850 MHz data indicates that we will achieve a five sigma flux density limit of about 30 mJy. We estimate that we will find between 80 000 and 90 000 new sources above this limit. This is a revised version of the paper presented at the Regional Meeting by the first four authors; the surveys now have been completed.

The absorption counterpart of curvature emission is reexamined based on the Landau-Lifshitz approach. Early derivations led to the conclusion that maser emission is not possible, but these early derivations neglected a drift effect which was first discussed by Zheleznyakov and Shaposhnikov. When the drift effect is included, the derivation implies that curvature maser emission is possible. It is shown that for maser emission to be possible, the Lorentz factor needs to satisfy γ ≳ 103 for radius of curvature of the magnetic field lines RB ≈ 106 to 109cm and frequency ω ≈ 107 to 1011 s−1. Possible application to pulsars is discussed.

We present UBV photometry of SW Lac and analyse its light–curve to deduce starspot parameters for this star.

There has been a dramatic increase in astronomical research output in New Zealand over the last decade. This is set to increase with the advent of a number of new pieces of astronomical hardware over the last five years. These include the 1m telescope and associated instrumentation at Mount John and the JANZOS collaboration, with its instrumentation on Black Birch. Black Birch is also the site of the US Naval Observatory’s southern hemisphere astrometric station, where, using a transit circle instrument, they are collecting data which will form part of the International Reference Star Catalogue. As well as these ‘professional’ programs there is also a large network of amateur astronomers, who can provide extremely useful input into certain astronomical programs at the various observatories around the country and the world.

A brief overview of the existing New Zealand astronomical scene will be followed by discussion of a number of new initiatives being proposed, which includes an automatic patrol telescope being developed by Carter Observatory, an expansion of the JANZOS collaboration and initial discussion about the possibility of an eastern arm for the Australia Telescope some where in New Zealand. In addition, for programs which require a long timebase of observations, extreme southerly latitudes or longitudinal coverage, New Zealand could provide a unique opportunity.

According to Oort (1965), the mass density in the solar neighbourhood (inferred from the gravity component normal to the galactic plane) is between 50% and 150% greater than the mass density inferred from non-dwarf stars. One possible explanation for the “missing mass” is an overabundance of faint M-dwarfs (Weistrop 1972), but present indications are that this overabundance is either small (Weistrop 1976; Sanduleak 1976) or non-existent (Faber et al. 1976; Eggen 1976). Nevertheless, Salpeter’s initial mass function (Salpeter 1955) suggests that the total mass may be dominated by low mass stars, including masses M≤0.08M⊙ which never undergo significant hydrogen burning.

As Voyager 1 sailed through Saturn’s system of moons and rings last November 1980 it revealed new worlds not seen by man before. For centuries, since Galileo’s first telescopic observations in 1610, the satellites of Saturn had been no more than pin points of light, whilst the structure of the rings was barely resolved beyond 3 principal bands. Yet, within the space of a few hours, that picture changed dramatically as the images of these objects grew through Voyager’s cameras from mere specks into full and wondrous worlds. These pictures contained features that were not only intricate and astonishing in detail but which were, in many cases, unfamiliar and unexpected. A composite view of the Saturnian system as seen by Voyager 1 appears in Figure 1. Saturn’s rings, once thought to be broad belts of particles spread uniformly thin through billions of years of evolution and interparticle collisions, were found to be divided into hundreds of individual ringlets (Figure 2). And Cassini’s Division, a region which had been previously thought to be empty because of a ‘sweeping’ influence of Mimas, was found to contain many ringlets itself! The appearance of light and dark radial spokes in the B ring, which rotated with a velocity contrary to the law expected of Keplerian orbits, was baffling. And the F ring (Figure 3) was found to contain knots, kinks and braids which probably indicated the presence of electro-magnetic forces as well as gravitational forces (Smith et al. 1981).

The extreme isotropy of cosmic ray events allows one to put upper limits on any possible non-isotropic contribution to the flux. In particular, one can investigate any excess of events which may be confined to the galactic plane. Such extra events would be expected from galactic ultra-high-energy (UHE) gamma-ray sources. Under the assumption of an isotropic cosmic ray flux, recent Buckland Park data place a 95% confidence level limit on the total southern hemisphere (declination −15° to −55°) flux of UHE gamma-rays at between 0.6 and 6 equivalent Cygnus X-3 sources, depending on assumptions concerning the gamma-ray spectrum.

The coalescence of two Langmuir waves, L and L′, produces emission at twice the plasma frequency in type II and type III solar radio bursts. The analysis of the coalescence process is usually simplified by assuming the head-on approximation, where the wavevectors of the coalescing waves satisfy kL ′ ≈ −kL , corresponding to the two Langmuir waves meeting head on. However, this is not always a valid approximation, particularly when the peak of the Langmuir spectrum lies at small wavenumbers, for narrow band spectra, and for spectra with broad angular ranges. Realistic Langmuir wave spectra are used to investigate the effects of relaxing the head-on approximation.

In the first four years of operation with the 80 MHz heliograph at Culgoora, 24 events classified as moving type IV were observed. Their observed characteristics can be interpreted in terms of gyro-synchrotron radiation from mildly relativistic electrons. Many of these events have been presented at previous ASA meetings and 12 have been discussed in the literature in detail.

A 30 MHz radio telescope has recently been completed at Fleurs, N.S.W. There has been a need for a high resolution sky survey to be carried out in the Southern Hemisphere at a frequency intermediate between 19.7 MHz (Shain et al.) and 85.7 MHz (Mills et al). One particular reason lies in the fact that some HII regions which are seen in absorption against the galactic background at 19.7 MHz and in emission at 85.7 MHz may match the background temperature at 30 MHz. If the temperature of such a region has been found by other means, the 30 MHz temperature of the portion of the Galaxy beyond it is determined irrespective of conditions nearer the observer, since the two temperatures must be equal.

The Japanese National Large Telescope is an 8-metre class optical-infrared reflector with a monolithic thin meniscus mirror, to be constructed at the Mauna Kea summit, Hawaii. The JNLT will be characterised by high quality performance in the optical and infrared regions, achieved by adopting new technologies such as active mirror support, fast optics and a thermally controlled dome. In particular, high infrared qualities are regarded as the most important characteristics among various design goals.

The JNLT project is now close to the final study phase before construction. This paper reviews the scientific motivations and the special technical features of the JNLT. Finally, the promotion of international collaboration around the JNLT is emphasised.

It is known that in the radio spertrum the limb of the quiet sun is brighter in the equatorial regions than near the pole. But most of the available theoretical calculations of the brightness distribution over the quiet sun have been made with the assumption of spherical symmetry. We have therefore calculated two-dimensional distributions at several decimetre and metre wavelengths, taking account of the observed asymmetry in the north-south direction. Newkirk’s method of ray-tracing was used, the calculations being made with a CDC 3600 computer. Some of the preliminary results (particularly for a sunspot minimum period) are presented here; they indicate that the electron temperature of the solar corona has a value of about 1 to 1.5 x 106 °K.