A solar flare erupted from a receding sunspot on September 16, releasing a pulse of X-rays and extreme UV radiation that caused a shortwave radio blackout in Africa and the Middle East. Frequencies below 25 MHz were affected up to an hour after the flare.
The magnitude of the solar flare is measured similarly to the Richter scale measuring earthquakes. Solar flares are classified as A, B, C, M, or X, with each consecutive letter representing a 10x increase in energy output. Class A solar flares are barely above the Sun’s background radiative emission.
Spaceweather.com reports that the September 16 solar flare that erupted from sunspot AR3098 was an M8 class, meaning it was almost an X-flare, the strongest kind.
According to the UK Met Office Space Weather Division, the outage was a “moderate” R2 category event (R1 is minor, R5 is extreme).
Space weather experts believe the solar flare may be accompanied by a coronal mass ejection (CME) from the sun’s coronasphere (a shell of million-degree plasma stretching millions of kilometers from the sun’s surface). According to Met and other space weather researchers, the CME could cause (minor) G1-level geomagnetic instability in the coming days, leading to weak power grid fluctuations and minor impacts on satellite operations.
However, as we increasingly rely on technology and satellites that are less protected from solar activity, such events could pose dangers.
This became evident on Feb. 4 when 38 of SpaceX’s “Starlink” satellites began to fall from the sky due to a “small” G1-class geomagnetic storm. SpaceX’s Starlink is a satellite internet constellation that aims to provide internet access in 40 countries and global cellular service after 2023.
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An M1 class solar flare triggered a CME and geomagnetic storm. An Indian space weather Journal explains how a seemingly “small” storm could cause so much damage.
“Although only ‘light,’ the storm pumped nearly 1,200 gigawatts of energy into Earth’s atmosphere,” explains lead author Tong Dang of the China University of Science and Technology. “This additional energy has heated the Earth’s upper atmosphere and greatly increased the aerodynamic drag of the satellites.”
Of the 49 Starlink satellites that were in the Falcon 9 rocket that launched on February 3, only a quarter survived. The project received a boost last week when SpaceX launched another Falcon 9 rocket carrying new Starlink satellites.
The satellites will be placed in a higher orbit to mitigate the atmospheric effects that led to the Starlink chaos earlier this year.
While solar flares are notoriously difficult (impossible) to predict, scientists warn that powerful flares will become more frequent as the Sun enters solar cycle 25, and sunspot activity is expected to peak in 2025.
Solar cycles average 11 years in length and have been tracked since solar cycle 1 was described in 1755.
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The largest solar flare in the last 500 years occurred about 160 years ago.
On September 1, 1859, Richard Carrington, one of England’s leading solar astronomers, observed sunspots. As he sketched what he saw, Carrington saw beads of blinding white light appear over the sunspots.
Before dawn the next day, skies were bathed in red, green, and purple auroras around the world, including in the Caribbean. Telegraph systems were disrupted and their operators electrocuted, setting telegraph paper on fire.
The incident went down in history as the “Carrington Event,” and scientists believe the solar flare occurred around an X45-class flare, making it the most powerful in recorded history.
Other recent X-class solar flare events demonstrate just how damaging they can be.
In 1972, a solar flare shut down long-distance telephone communications in the United States. A 1989 solar flare left six million Canadians without power for nine hours. And in 2000, on Bastille Day, an X5-class solar flare shorted out some satellites and caused radio blackouts.
As the solar cycle peaks, space weather scientists warn things will get pretty rowdy. In fact, the Sun has already been more active this cycle than predicted, and has triggered several X-class flares so far this year.
science alert reports that we can expect more geomagnetic storms as the cycle peaks, including moderate and strong storms. Strong storms would disrupt satellites and navigation systems.
