SOLAR ACTIVITY IN 1953

Abstract

During 1953, observations of the sun were made at Mount Wilson on 350 days, on 109 of which no spots were seen. The fifteen completely cloudy days in 1953 were evenly distributed throughout the year, only one month having three such days and four months none. The previous record for the number of observing days per year was 341 in 1942. The longest continuous sequence of spotless days was from November 8 to December 5 inclusive. The total number of spot groups observed at Mount Wilson was 93 in 1953, compared with 219 in 1952 and 294 in 1951. Only one of the 70 groups for which magnetic polarities were determined was irregular. The northern hemisphere was slightly the more active in 1953, having 51 groups, while the southern hemisphere had 42. The average latitude of the spot groups was 9?9 for the northern hemisphere and 8?6 for the southern. This compares with 10?7 and 10?4, respectively, in 1952, and 11?6 and 11?3, respectively, in 1951. The mean latitude of 9?9 in the northern hemisphere is for spots of the waning cycle and excludes one very high-latitude, short-lived spot1 at 52° N. The low average latitude of the groups indicates that the minimum is near and that new-cycle spots should be predominant in 1954. Sunspot activity, which declined noticeably in 1953 (Fig. 1), had a small maximum in August and September. This maximum in the short-period fluctuations was about thirteen months after a similar one in 1952.2