Yesterday, May 22nd, sunspot AR2824 unleashed a sequence of solar flares unlike anything we’ve seen in years.
In only 24 hours, NASA’s Solar Dynamics Observatory recorded 10 C-flares and 2 M-flares.
The rapidfire explosions hurled multiple overlapping CMEs into space. According to NOAA models, at least one of them will graze Earth’s magnetic field on May 26th.
Huge solar radio burst
During yesterday’s frenzy, the sun emitted a shortwave radio burst so loud that “it drowned out lightning static from a severe local thunderstorm,” reports Thomas Ashcraft, who recorded the noisy signal using a radio telescope in rural New Mexico. Listen to the huge solar storm noise in the audio below:
The radio burst coincided with an M1.4-class solar flare at 21:30 UT. “This was a very hot and dynamic flare for sure,” says Ashcraft. “I was recording audio at 22 MHz and 21 MHz, and my radio spectrograph was operating from 30 MHz down to 15 MHz. Strong solar radio emissions were present at all frequencies.”
This event was so intense, radio operators in the Arctic heard it at midnight. Rob Stammes chart-recorded the outburst from the Polarlightcenter in Lofoten, Norway:
“Normally, solar radio bursts can only be received during daylight hours,” says Stammes. “Here in the Lofoten islands, the sun is only just below the horizon in May around midnight. So I was able to detect the event even though the sun was not up.”
Widespread radio blackout
Waves of ionisation rippling through Earth’s upper atmosphere have caused shortwave radio blackouts over North America on May 21st and southeast Asia on May 22nd.
Ham radio operators, aviators and mariners might have noticed unusual propagation at frequencies below ~20 MHz.
Astronomers classify solar radio bursts into 5 types. Ashcraft’s radio spectrograph is able to determine which ones were present in the May 22nd outburst. “It was a mixture of Type II and Type V,” he says. These are caused, respectively, by shock waves and electron beams moving through the sun’s atmosphere in the aftermath of strong flares.
The flaring of sunspot AR2824 continues apace on May 23rd, so more radio bursts may be in the offing. The impact of the CME’s dense flank could spark G1-class geomagnetic storms and auroras. [Space Weather, Daily Express]
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