SOLAR ACTIVITY

Dominion, Volume 33, Issue 84, 3 January 1940, Page 6

SOLAR ACTIVITY

Sunspot Observations

In 1939 185 DISTINCT GROUPS During the year just ended the sun was observed in Wellington on 166 days and on none of these occasions was the disk entirely clear of spots, reports Mr. G. V. Hudson, Karori. On December 6, however, only one small spot was visible, this being the lowest number for any observation taken during tlie year. One hundred and eightyfive distinct groups of sunspots were recorded, compared with 253 in 1938. A few sunspots persist for more than a single rotation of the sun (about 26 days) and in such cases the same group may sometimes be counted twice over. Sunspots over 100.000 miles in lengtn, which are usually visible to the naked eye through smoked glass, were observed on the following dates: —April 22-May 1: July 4-14, two large groups in view simultaneously; August 29September 5; September 5-16; and November 14-20. Since November 20 there has been a very marked decline in solar activity. Many astronomers estimate that sunspot activity was at its maximum about the middle of 1937, but the fact remains that the year 1938 was also a period of very intense activity. It i s generally considered that the last maximum is the greatest since 1870, or six solar cycles ago. As anticipated a moderate reduction in sunspots has taken place during 1939. but a greater decline may be expected in 1940. The next, solar minimum is due about 1944.