David Greenhoff, age l2, of Lakewood, Ohio, for his question:
When are there most sunspots?
The radiant complexion of the sun often tends to be marred by rashes of dark spots. These sunspots have been under regular observation for more than l00 years, and they seem to occur in cycles. There are years when the sun is spotless for days at a time and years when it is never without two or more massive rashes.
Sunspots usually occur in groups and a lone spot is most likely the survivor of a fading rash. In l948 a tremendous dark spot measuring 90,000 by 60,000 miles was observed on the face of the sun. It was part of a group covering an area estimated to be 5,700 million square Miles. This monstrous rash covered about one half of 1% of our side of the sun.
As the sun rotated it was carried around three times and it did not subside for about l00 earth days. This rash was soon followed by another almost as big. Astronomers had expected l948 to be a maximum sunspot year and were not surprised. In the next few years they were not surprised to see the sunspots dwindle.
The next maximum year was expected to occur about l0 years later, and the International Geophysical Year was planned to observe it in detail from July, l957 to December, l958. Observation posts were set up at 4,000 stations strewn from pole to pole and around the globe. The experts were not disappointed for the IGY was opened with an outburst of sunspots.
A Russian station flashed news of a giant solar flare of a kind that usually blazes from major sunspot activity. When the sun rose over our eastern stations the rash of major sunspots came into full view. A world wide alert was sent out and in a few hours seething solar particles were bombarding our atmosphere. There were radio blackouts and upsets in the earth's magnetic field.
The pattern of sunspot activity was figured out by an amateur astronomer. He used a small two inch telescope to watch them through 20 years. In l843 astronomer Schwabe of Germany announced that sunspot activity tended to increase and deCre8se in
Cycles lasting a little longer than 11 years. We now know that the cycle may vary from 9 to 14 years. The last major outburst was during l957 and l958 and if it is followed by an average 11.2 year cycle, we can expect the sunspot year to begin in l969.
A maximum year dwindles rather slowly and the year of minimum sunspots may not follow for six or seven years. It tends to bring a few small sunspot groups near the solar equator. Then a few, rashes appear in higher latitudes and each year the rashes get bigger and more numerous. The activity builds up fast to another maximum year of peak performance.