Published on Mar 31, 2014
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Space Weather
by Dr. Tony Phillips.IMPULSIVE SOLAR FLARE SCRAMBLES RADIO SIGNALS:
On Saturday, March 29th, the magnetic canopy of sunspot AR2017 erupted, producing a brief but intense X1-class
solar flare. A flash of extreme UV radiation sent waves of ionization
rippling through Earth's upper atmosphere and disturbed the normal
propagation of terrestrial radio transmissions. Radio engineer Stan
Nelson of Roswell, NM, was monitoring WWV at 20 MHz when the signal
wobbled then disappeared entirely for several minutes:
"The
Doppler shift of the WWV signal (the 'wobble' just before the blackout)
was nearly 12 Hz, the most I have ever seen," says Nelson.
The flare not only blacked out radio signals, but also produced
some radio signals of its own. The explosion above sunspot AR2017 sent
shock waves racing through the sun's atmosphere at speeds as high as
4800 km/s (11 million mph). Radio emissions stimulated by those shocks
crossed the 93 million mile divide to Earth, causing shortwave radio
receivers to roar with static. Here is a plot of the outburst detected by Nelson using a 20.1 MHz RadioJove receiver. Elsewhere, strong bursts were recorded at frequencies as high as 2800 MHz. It was a very broad band event.
NASA's Solar Dynamics Observatory recorded a beautiful movie of the flare:
The
flash you just saw was extreme UV radiation, the type of radiation that
ionizes the upper layers of our atmosphere. In this case, the ionizing
action of the flare led to a rare magnetic crochet, measuring 17 nT at the magnetometer in Boulder, Colorado.
A
magnetic crochet is a ripple in Earth's magnetic field caused by
electrical currents flowing in air 60 km to 100 km above our heads.
Unlike geomagnetic disturbances that arrive with CMEs days after a
flare, a magnetic crochet occurs while the flare is in progress. They tend to occur during fast impulsive flares like this one.
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