The topic of this Joint Discussion has received enormously increased interest in the last couple of years, owing to its potential for the investigation of the structure of the interior of the sun, including related topics like the structure of the convection zone, solar metal abundance, and the still unsettled neutrino problem.
The first stimuli came from the startling observations of Hill et al. (1976) in Arizona, Severny et al. (1976) on Crimea, and Brookes et al. (1976) in Birmingham, accompanied by a large volume of theoretical papers, the details of analysis of which soon went beyond the actual status of the observational facts.
We then witnessed, however, the success of considerable refinements of the techniques of observation, together with an obvious widespread temptation to push the interpretation of many of the new results to the limits of optimism. Yet, despite of the still increasing body of data suggesting the reality of the solar origin of the observed phenomena, much scepticism was prompted by the complicated statistics and the intricate numerical procedures involved in the data analysis, as well as by the great uncertainty about the significance and the amounts of “noise” contributed to the signal by electronics, changes of the conditions of the ray path within the telescope, terrestrial atmospheric inhomogeneities and solar quasi-stationary motions.