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Visible Clouds in the Ionosphere?

January 16th Fact-of-the-Day

Lumpy clouds of ionized gas in the ionosphere often return radio signals to earth. The returned signals tend to twinkle like star light (only slower), because of the constantly changing positions and radio transparencies of the ionized clouds. The twinkle phenomenon is called radio scintillation. What is less commonly known is that visible clouds of some kind sometimes form in or near the base of the ionosphere. When they form, they often are illuminated by sunshine well after surface-level sunset, because of their high altitudes. Scientists don't why they form or exactly what they are, but they are believed to be related in some way to the level of solar activity. Look in the sky well after sunset when the atmosphere is clear of lower water-vapor clouds and you may see them. ©2005 Martek, International. All rights reserved.

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