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5/2/39
This is the region known as the ionosphere, where an electric shield is established by the action of the sun' s ultra¬ violet light, which prevents radio waves from escaping into space. The ionosphere is explored by the time taken by radio impulses to bounce against it and be reflected back to earth again. Its distance is from 100 to 300 kilometers. The time taken for the return trip journey ranges from one 1,500th to one 500th of a second.
The report was presented by Dr. L. V. Berkner of the Carnegie Institution of Washington, who set up and is directing the use of the present measuring apparatus. Following the meeting the annual conference of ionosphere experts was held at the ter¬ restrial magnetism laboratory.
The reflection of radio waves from the jagged edges of the ionosphere, where night and morning meet, was reported by Drs. J. A. Pierce and H. R. Mimmo of Harvard University.
For many years, they said, it has been generally known that strong, sharply defined radio echoes occasionally return to the sending station after having traversed a path which greatly exceeds the round-trip distance to the ionosphere. Such effects hitherto have been ascribed to reflections from mountains or from concentration of negatively charged particles over the polar reg¬ ions, where they supposedly are drawn by the magnetic field of the earth.
Their own studies of numerous such reflection patterns, they said, indicate that the delayed echoes are returned from regions where there is a marked curvature of the F. layer, the second of the electrified strata of the ionosphere. A region of this sort normally occurs at the edge of the sunlit zone and can turn back a ray which may have traveled many thousands of kilo¬ meters around the dark side of the earth. Small night-time vari¬ ations in the curvature of the F layer, they said, are of very common occurrence and are believed to explain such phenomena as long-period, long-distance radio fading.
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McNINCH, ILL, TAKES LEAVE OF ABSENCE
Chairman Frank McNinch of the Federal Communications Commission has left Washington for a three-week stay at an undis¬ closed destination. At Mr. McNinch' s office, it was said the Chairman's health has not been good for some time and he had decided on a rest period in an effort to recuperate.
During his absence, the other Commissioners, starting with Thad H. Brown, will serve in rotation as Acting Chairmen.
In some quarters it was believed that Mr. McNinch might remain away indefinitely or even resign because of his ill¬ ness. He has twice been in Naval Hospital with a stomach disorder.
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