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10.7 cm Solar Flux

May 9th Fact-of-the-Day

Karl Kansky, a Bell Telephone Company engineer, discovered previously unknown radiation coming from the sky in 1933. British coastal radar was plagued by interference in 1942 that was first thought to be enemy jamming, but that was later found to be coming from the Sun. That finding intrigued astronomers who subsequently discovered that the Sun emits electromagnetic radiation over a very wide frequency spectrum and that surface-regions near sunspots emit strong radiation at a wavelength of 10.7 cm (2.8 GHz, which is near the 2.4 GHz wireless-network / cordless-telephone band). The National Research Council of Canada began logging the amplitude of solar flux at that wavelength at their Algonquin Radio Observatory near Ottawa in 1947. That record proved over-time to be an easier-to-obtain and more reliable indicator of ionosphere electron-density than the Sunspot Number. Sunspot observations are often obscured by clouds, but 10.7 cm solar flux penetrates clouds and can be measured regardless of cloud-cover. ©2005 Martek, International. All rights reserved.


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