No. 35: Sep-Oct 1984
When the night sky is photographed in the infrared portion of the spectrum, luminous wave-like structures appear in the upper atmosphere. The wave crests are about 50 kilometers apart; lengthwise, they stretch up to 1.000 kilometers; altitude, about 85 kilometers. As many as ten waves may be seen at the same time. Morphologically, these waves resemble noctilucent clouds, which are sun-illumined, high-altitude clouds. The infrared waves, however, appear when the sun is well below the horizon. Since these waves are seen only at low angles over the horizon, some geophysicists propose they are the result of a geometric effect produced by viewing a rippled layer of weakly emitting gases in the upper atmosphere.
When one looks at this rippled layer just above the horizon, one sees alternating thick and thin sections due to the perspective. The thick portions will appear brighter than the thin sections. As for the origin of this postulated rippled layer; no one is sure. Gravity waves may be involved.
(Herse, M.; "Waves in the OH Emissive Layer," Science, 225:172, 1984.)
Comment. As described in our Catalog Lightning, Auroras, Nocturnal Lights. luminous atmospheric waves are, on rare occasions, visible to the naked eye. It is possible that the bandedsky phenomenon is related to the infrared waves. For more information on the book just mentioned, visit: here.
|Rippled emissive layer around the earth. The variable optical path near the horizon could create luminous ripples to a ground observer.|
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