Sunspots & Radio

As if celebrating some ancient solar anniversary, the sun appeared to be setting off fireworks last week. Astronomer Lucien d'Azambuja of the Paris Observatory at Meudon peered at solar photographs made with his powerful spectrohelioscope, found flaring "prominences'" shooting out 90,000 to 180,000 miles from the surface. Astronomer d'Azambuja declared he had not observed such intense solar activity for 20 years.

Meantime in the U. S. one Harry LawIon, a free-lance astronomer of New Orleans, succeeded in getting on Associated Press wires a story that he had found a sunspot 125,000 miles long. Few days later Mr. Lawton wrote to the Naval Observatory in Washington, chided it for not publicizing this gigantic blotch. Observatory officials coughed politely, admitted sighting an unusually large crop of spots but none of the size mentioned by Lawton, declined to engage in controversy with him pending scrutiny of his scientific credentials.

There was no doubt last week, however, that the sun was working up a fine case of sunspot pox. Sunspot activity waxes & wanes in cycles of about eleven years. A new cycle started in 1933, its peak is expected in 1939. Sunspots appear to be the mouths of whirling funnels of gas originating in the solar interior. It has been suggested that the shifting combination of gravitational pulls exerted by the planets is the cause of the internal commotion which gives rise to sunspots.

No one has traced a consistent parallel which would show that sunspots cause war, prosperity, disease epidemics or drought. Astronomers agree, however, that at times of sunspot intensity more ultraviolet radiation comes from the sun to earth, the air averages about one degree cooler, slightly more rain falls and there are disturbances of the terrestrial magnetic field. At such times ordinary radio reception is more troubled by static. But a U. S. Bureau of Standards scientist has found evidence that ultra-short-wave reception is better in the daytime when sunspots are rampant (TIME, Dec. 16, 1935).

Ultraviolet radiation has a propensity for knocking electrons off molecules and thus creating ions--electrified particles. In the tenuous upper atmosphere of earth, far higher than any balloon has ascended, there are several layers of such ions which increase in density during sunspot peaks. This is to be expected since sunspots are accompanied by heavier ultra violet bombardment. These electrified layers serve to deflect most radio waves, curve them around the bulge of earth. In radio's pioneer days, when only one layer was known, it was called the Kennelly-Heaviside layer after its discoverers. Now the electrified region as a whole is more generally referred to as the ionosphere.

In Washington last week Physicist Lloyd Viel Berkner of the Carnegie Institution told what is known or surmised, in the light of most recent researches, about ''The Electrical State of the Earth's Outer Atmosphere." When radio waves of different frequencies are directed up at the ionosphere, some are bounced back to the starting point where the elapsed time is recorded while others escape into space. From this data the heights and densities of the layers can be calculated. Of the three major layers, said Dr. Berkner, the lowest (E) averages 65 miles high, the next (F1) 130 miles, the uppermost (F2) 190 miles. In summer the densities of these three, from top to bottom, are 16,000,000 ions, 5,300,000 ions and 2,800,000 ions per cubic inch. During the present sunspot cycle ionization has increased about 50% in the E and F1 layers, about 200% in the high F2 layer. Almost all the ionization in the lower layers seems due to radiation, but Dr. Berkner believes that much ionization in the F2 layer is caused by streams of particles hurled from the sun. It is possible that some ions are contributed by the swift, flaming fall of meteors.

The heights of the ionosphere shells change from hour to hour, from day to day. In June the two upper layers are widely separated in the Northern Hemisphere where the noon sun is highest, but in the Southern Hemisphere in that month they are merged, according to the findings of the Carnegie Institution s ionosphere stations in Peru and Australia. In December, the merging takes place in the Northern Hemisphere, the separation in the Southern.

Dr. Berkner pointed out that better acquaintance with the ionosphere has made it possible to say which short-wave frequencies will be best at different seasons and various stages of the sunspot cycle. Few years ago when many short-wave police radio stations were set up, the ranges were generally limited to 30 or 40 miles, since the signals escaped through the thin ionosphere into outer space. Now, with greater ion density in the upper air, messages for New York City police radio cars sometimes even carry across the Atlantic Ocean.

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