What’s all this about the solar maximum?

A recent uptick in solar activity and its effects on infrastructure on and around Earth has raised concern about how the upcoming solar maximum will affect technology.

So, what’s going on?

Our cyclic Sun

The Sun has an approximately 11-year cycle of higher solar activity driven by the flipping of its magnetic field. The beginning of these cycles is known as a “solar minimum” – when solar activity is at its lowest – and the middle is known as the “solar maximum” – when the sun has the highest number of sunspots, solar flares and coronal mass ejections (CME) and, therefore is most active.

Our Sun, like all active stars, is a burning ball of gas and plasma. At its surface, temperatures can reach more than 5,000°C. At its nuclear fusion reactor core, the Sun is burning at temperatures greater than a million degrees.

So, it’s no surprise that there are violent interactions taking place.

Among these outbursts are solar flares, which are large eruptions of electromagnetic radiation from the Sun’s surface. These mysterious phenomena tend to take place in active regions in the presence of strong magnetic fields typically associated with sunspots.

CMEs are huge ejections of the solar magnetic field. These expulsions take with them huge amounts of plasma, ionising matter and shoot high-energy charged particles at great velocity into space.

Solar winds are streams of charged particles released from the Sun’s corona – a layer of superheated plasma, mostly consisting of electrons, in the Sun’s upper atmosphere.

Scientists have been tracking the solar cycle since 1755. We are now entering the solar maximum of Cycle 25 which is expected to peak in 2024–25. Solar Cycle 25 began in December 2019.

“At the moment, we’re seeing the rise of Solar Cycle 25. And it’s exceeded the forecasts that were made,” solar astrophysicist at the University of Sydney, Professor Mike Wheatland, tells Cosmos. “It looks like it’s on track to be about as big as Cycle 23.” Cycle 23, 1996–2008, peaked in 2001.

Know your ABCs and Ms and Xs

When CMEs collide with Earth’s magnetosphere – the region of space around the Earth that is produced by our planet’s magnetic field – they can cause geomagnetic storms and aurorae.

These storms are rated G1 to G5. Disturbances from high-energy particles from solar activity can also cause radio blackouts which are similarly scaled R1 to R5.

Solar flares fall into categories labelled A, B, C, M or X where each subsequent letter represents a flare with 10 times more energy than the previous letter. The number following the letter marks the number of times stronger than the weakest solar flare in that category. For example, an X2 flare is twice as powerful as an X1.

Increased solar activity has already led to technological disruptions on Earth in the last 18 months.

February 2022 saw a 38 of SpaceX’s 49 “Starlink” satellites fall out of the sky due to a G1-class storm from a CME. An M8-class solar flare in September released a pulse of X-rays and extreme UV radiation which caused a shortwave radio blackout in Africa and the Middle East for up to an hour. Earlier this month, an X1 solar flare caused a 30-minute high-frequency radio blackout across the Pacific Ocean and western US.

Solar activity in history

The greatest solar flare incident of the last 500 years occurred on September 1, 1859 and is known as the “Carrington Event.” Scientists estimate that the solar flare that caused it was an X45 ejection.

Drawing of sunspots by Richard Carrington (1826-1875), the English astronomer. Source: Wikimedia Commons.

Skies all over the planet were bathed in red, green and purple auroras, even in the tropics. Telegraph systems were disrupted, and their operators electrocuted, setting telegraph papers on fire.

In 1972, a solar flare knocked out long-distance US telephone communication. A 1989 solar flare knocked out power for six million Canadians for nine hours. An X5-class solar flare in 2000 (as Cycle 23 was reaching its maximum) caused radio blackouts and short-circuiting satellites.

Solar Cycle 25

Overall, the experts agree the peak of this cycle is expected to be “moderate.”

“During the solar maximum, the Sun is expected to emit 4 to 6 flares of varying intensity and direction per day,” says Alister Graham, a professor of astronomy at Melbourne’s Swinburne University.

“Predicting solar cycles is fraught,” Dr Marc Duldig, a physicist at the University of Tasmania, told Cosmos. “I don’t think it’s going to be a particularly violent solar maximum. Nothing like we were getting in the 1960s or 70s.”

“Although we haven’t reached the peak of Solar Cycle 25 yet, there’s already more sunspots than the previous solar cycle,” says University of Newcastle physicist Dr Hannah Schunker. “It’s going to be larger than the previous one but in the big scheme of things, it’s probably going to be fairly moderate.”

“To get a severe space weather storm, there’s a whole sequence of events that have to happen,” Wheatland adds. “There could be a severe space weather storm occurring during this solar cycle, there could be a couple of them.”

Duldig notes that it “is a bit of a probability game.”

“This is a really tough problem and we’re working really hard on it,” Schunker notes. “One of the issues is you can’t make an experiment with the sun.”

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