GOOD WEATHER AFTER 1938.

Auckland Star, Volume LXVIII, Issue 156, 3 July 1937, Page 10 (Supplement)

GOOD WEATHER AFTER 1938.

Bonfires in the Sun THEORIES ABOUT SUNSPOTS (By BEN DUDLEY, F.R.A.S.) rE accompanying illustration represents the sun as it appeared over the week-end, June 1921. The sun is in a highly-disturbed condition, and marked by over a score of spots, many of which are some thousands of miles in diameter. Several of these spots are grouped, while round the darker centre of each is a ring irregularly shaped. This centre is known as the umbra, and the lighter enveloping ring the penumbra. Several spots are "loaders" followed by a train of smaller ones known as "trailers," quite a familiar feature of sunspot phenomena. The most ancient and perhaps the most fascinating explanation is that propounded by Alexander Wilson, of Glasgow, whose theories were amended by Sir William Hirschel. Professor Wilson took it for granted that the sun is enveloped within two atmospheres, the outer one being luminous and therefore fittingly called the photosphere, while the inner one is non-luminous. He further supposed the spots to be openings in thfse two atmospheric layers by which we are able to actually see the darker solid body of the sun itself. Since then, however, the generallyaccepted opinion of scientists is that the sun is not a solid sphere; bo that the'

Wilson theory, however attractive, has fallen into disfavour. An American astronomer, Professor Hale, was the first to put forward the idea that sunspots were often vertical in nature, although this had already been guessed by others He detected indications of a cyclonic action in these spots, as if they might be stom

centres. His conclusions on the matter have been largely accepted in view of the evidence that has been collected as a result of careful observation. Most readers will have made themselves familiar with the 11 year cycle of sunspot activity and the corresponding 11 year rise and fall in the magnetic condition of the earth. It is now known for certain that terrestrial magnetism conforms to the periodic cycle just referred to. The interval between two successive returns of a spot to the same place on 1 the sun's disc represents practically the

'period of the sun's revolution upon its axis, which corresponds with the interval between the successive returns of magnetic storms on the earth. This occurance has been observed and tested over and over again, so that there is no doubt of it. The inevitable conclusion is that either magnetic variations on earth are expressly due to sunspots. or both are more or less simultaneous expressions of some common cosmic cause. Of these alternatives the second is the more likely one. Very certainly, then, a maximum of solar agitation is associated with a maximum of terrestrial agitation, and a minimum condition in the sun's storminess is associated with a magnetic disturbance on the earth. It is also known that the periodic rise and fall in the intensity and frequency of auroral phenomena closely follows the rise and fall in the sun's activities. Auroral displays in this sense are, in other words, symptomatic. In connection with the present spot groups there are to be seen the usual accompanying display of faculae, consisting of bright, elevated streams belonging to the solar surface, such as are often found in greater abundance in the neighbourhood of dark spots. They are believed by some authorities to be the tops of clouds of vapour rising from the tremendous red flames or "prominences" which leap up from the surface of the sun to the height of many thousands of miles. It was such bonfires in the sun that the astronomers saw while witnessing the recent solar eclipse at Canton Island, the altitude reached bv these great flames being estimated at 5000 miles. Sometimes, however, they soar to vastly gi eater heights than this. In some instances they have reached the height of 400,000 or even .500,000 miles above the solar surface. The state of the sun will continue to manifest considerable agitation until 19;w «r even early 10:19, after which it will fall gradually to a quiescent condition. reaching a minimum about six years later. After 1938, therefore, it may be expected that terrestrial weather will improve, becoming more and more stable