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Observations of the distribution of millimetre-wavelength brightness over the quiet Sun provide an important test of models of the solar chromosphere. The author and colleagues have recently carried out two investigations of the quiet-Sun brightness at 3 mm wavelength — one by means of a total eclipse observation (Labrumet al. 1978) and the other by aperture synthesis with a two-element interferometer (Archeret al. 1978). I present here a preliminary discussion of these and other measurements of millimetre-wavelength brightness distributions and of their interpretation in terms of chromospheric structure.

Observations of the Sun were made at 3 mm wavelength during the total eclipse of 1976 October 23. Analysis of the record obtained near third contact indicates that the Sun at this wavelength is slightly limb-brightened, and that the solar radius is 1.007 times the photospheric radius.

Meter-wavelength observations are presented for the solar radio storm of August 17–22, 1968. The data comprise dynamic spectra and high-resolution brightness distributions from the 80 MHz radioheliograph.

The U-burst, first identified by Maxwell and Swarup and Haddock, is a type of solar radio event lasting ~ 10 s in which the frequency of the emission at first drifts rapidly downwards, then increases again. On the dynamic spectrum record the burst has the appearance of an inverted letter U.

On 1968 October 30 a large solar flare (importance 3B to 4B) began at approximately 23h42m U.T. We present here a preliminary account of the associated radio emission.

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.