from
http://www.spaceweather.com/
IONOSPHERIC DISTURBANCE: The C4-class solar flare of Aug. 14th bathed Earth's upper atmosphere in X-rays and caused a wave of ionization to sweep over Europe. This improved the propagation of low-frequency radio signals which use the ionosphere as a reflector to skip over the horizon. A SID monitor operated by Jan Karlovsky of Hlohovec, Slovakia, recorded the effect:
"SID" stands for Sudden Ionospheric Disturbance, and a "SID monitor" is a radio receiver that monitors ~20 kHz signals from distant transmitters. "My system easily detected the effects of the solar flare," says Karlovsky. "I monitor two stations: DHO38 in Germany (23.4 kHz) and GQD in Great Britian (22.1 kHz). The German signal was most strongly boosted."
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Those of us who pay careful attention to solar flares (I'm interested for radio propagation and protecting my substantial investment in radio gear) know that "the big one" could (COULD) one day come as could a black hole beam, etc. etc. The odds of it happening in our lifetime (or in several lifetimes to come) in a way that leads to catastrophe (as opposed to a planned inconvenience) is very low. Talking to Europe and Australia with 20 watts has been a blast lately.