Powerful solar flare eruption from 'sneaky' sunspot triggers widespread radio blackouts (video)

The relatively small, unassuming sunspot AR3599 has been crackling with minor solar flares in recent days — but it surprised everyone by unleashing a strong M7.4 class solar flare on Sunday (March 10) at 8:13 EDT (1213 GMT).

The flare was also accompanied by a coronal mass ejection (CME) — a large release of plasma and magnetic field from the sun. The CME is barreling through space at around 1.7 million mph (750 km/s), according to spaceweather.com, but to the disappointment of aurora chasers, it's predicted to pass ahead of our planet. However, we can keep our fingers crossed for a possible glancing blow, as suggested by a NASA model, that could trigger minor G1-class geomagnetic storms on March 13.

Just eight minutes after the solar flare erupted, an extensive radio blackout was experienced across Africa and the South Atlantic. According to spaceweather.com, ham radio operators may have experienced signal loss for up to 30 minutes after the flare. Blackouts like this are common after powerful solar flare eruptions occur, as these events release a strong pulse of X-rays and extreme ultraviolet radiation which travel towards Earth at the speed of light. When the radiation hits Earth's atmosphere, it ionizes the upper layer known as the thermosphere — causing shortwave radio blackouts on the portion of Earth that was facing the sun at the time of eruption.

radio blackout image showing a map with a large red patch over Africa and the South Atlantic showing widespread radio blackouts. — Shortwave radio blackouts were experienced across Africa and the South Atlantic. (Image credit: NOAA/SWPC)

What are solar flares?

Solar flares are triggered when magnetic energy builds up in the sun's atmosphere and is released in a vigorous burst of electromagnetic radiation. They are categorized by size into lettered groups, with X-class being the most powerful. There are then M-class flares that are 10 times smaller than X-class flares, followed by C-class, B-class, and finally, A-class flares which are too weak to significantly affect Earth. Within each class, numbers from 1 to 10 (and beyond, for X-class flares) denote a flare's relative strength. The recent flare clocked in at M.7.43, according to Spaceweatherlive.com. This result was achieved using data from NASA's GOES-16 satellite.

Daisy Dobrijevic joined Space.com in February 2022, having previously worked as a staff writer for All About Space magazine. She completed an editorial internship with BBC Sky at Night Magazine and worked at the National Space Centre, communicating space science to the public.

Daisy holds a PhD in plant physiology and a Master's in Environmental Science. Based in Nottingham, U.K., she covers all things space, with a special focus on solar activity and space weather. She also has a keen interest in astrotourism and is always on the lookout for the next northern lights adventure.

She will be a guest speaker aboard HX's Solar Eclipse Expedition in August 2026 and will join Hurtigruten as an onboard astronomer for a northern lights sailing in January 2027.