March 29, 2024: This is becoming routine. The sun just produced another X-class solar flare, the 7th of 2023. The X1.2-category explosion came from sunspot AR3256 near the sun’s southwestern limb:

Radiation from the flare ionized the top of Earth’s atmosphere, causing a strong shortwave radio blackout over southeast Asia, Australia and New Zealand. Ham radio operators may have noticed loss of signal and other propagation effects below 30 MHz for as much as an hour after the peak of the flare (March 29th @ 0233 UT).

A faint CME left the sun after the explosion. NOAA analysts have determined that it will miss Earth–no impact.

The real significance of this flare may be the number “7.” That’s the total number of X-flares in all of 2022. With today’s flare, the sun has already matched that total in 2023–and it’s only March.

This is yet another sign that Solar Cycle 25 is rapidly intensifying. If the trend continues, we could have nearly 30 X-flares by the end of 2023, an order-of-magnitude greater activity than only two years ago. Official forecasts are calling for Solar Maximum to arrive in 2024 or 2025. If so, there is plenty of time for the solar cycle to intensify even more; X-flares could become routine, indeed. Solar flare alerts: SMS Text.

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March 23, 2023:

Something rare and strange happened last month. On Feb. 23rd, growing sunspot AR3234 produced an M-class solar flare. It was nearly midnight in Florida when the explosion occurred, so you’d expect no one there to notice. On the contrary, in the community of High Springs, FL, amateur radio astronomer Dave Typinski recorded a strong shortwave radio burst.

“You CAN see the sun at midnight in Florida… sometimes,” says Typinski. This is what his instruments recorded while the flare was underway:

A double wave of static washed over Florida, filling the radio spectrum with noise at all frequencies below 25 MHz. “The Sun was 69° below the horizon when this happened,” he marvels.

How is this possible? The entire body of our planet was blocking the event from Typinski’s antenna. It’s called “antipodal focusing.” First postulated by Marconi more than 100 years ago, antipodal focusing is a mode of radio propagation in which a signal starts out on one side of the planet, gets trapped between Earth’s surface and the ionosphere, and travels to the opposite hemisphere. Waves converging at the antipode can create a surprisingly strong signal.

Right: This diagram from a declassified US Gov.report shows the basic geometry of antipodal focusing.

“This is the second or maybe third midnight solar radio burst I’ve seen in ten years, but it’s by far the strongest,” says Typinski. “The previous events happened at the height of Solar Cycle 24. They’re quite rare.”

Pause: Yes, solar flares can produce radio signals. Typinski’s midnight burst was a “Type V,” caused by streams of electrons shooting through the sun’s atmosphere in the aftermath of the flare. Plasma waves rippling away from the streams emited intense bursts of natural radio static. The burst was first observed in broad daylight at the Learmonth Solar Observatory in Australia, then it curved around Earth to reach Typinski.

Above: An example of antipodal focusing of seismic waves caused by the Chicxulub asteroid impact. The geometry is the same as for radio waves. [more].

“This propagation mode was used during the Cold War,” notes Typinski. “The U.S. would park a SIGINT ship in the south Pacific to grab signals from the Eastern Bloc. The Soviets probably did the same thing, parking in the southern Indian ocean.”

Turns out, this method of spying works for radio astronomers, too. Would you like to record an event like this? NASA’s Radio JOVE program makes it easy. Off-the-shelf radio telescope kits allow even novices to monitor radio outbursts from the sun, which are becoming more frequent as Solar Cycle 25 intensifies.

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March 13, 2023: Something big just happened on the farside of the sun. During the early hours of March 13th, SOHO coronagraphs recorded a farside halo CME leaving the sun faster than 3000 km/s:

Because of its extreme speed, this CME is classified as “extremely rare,” a fast-mover that occurs only once every decade or so. A NASA model of the event shows the CME heading almost directly away from Earth. Good thing!

Although the CME was not Earth-directed, it has nevertheless touched our planet. See all the snowy dots and streaks in the coronagraph movie above? Those are energetic particles accelerated by shock waves in the CME. They create short-lived luminous speckles when they hit SOHO’s digital camera.

NOAA’s GOES-16 satellite has detected the particles reaching Earth–all from the CME’s backside. Imagine what a frontside blast would have been like. Earth’s magnetic field is funneling the particles toward the poles where a type of radio blackout is underway–a polar cap absorption (PCA) event:

Note the broad red areas. Airplanes flying over these regions may find that their shortwave radios won’t work due to the ionizing effect of infalling protons. This PCA could persist for a day or more. You can monitor its progress here. Solar flare alerts: SMS Text.