How solar flares spread across the solar system

The sun is extremely active right now, throwing the biggest solar storm at Earth in 20 years. This is what it does to the rest of the solar system.

If you happened to look up at the sky during a few nights in May 2024, there was a good chance you’d see something spectacular. For those located at relatively low latitudes, it was a rare opportunity to see the flashing red, pink and green glow of our planet’s auroras.

A powerful solar storm sent bursts of charged particles hurtling toward Earth, unleashing spectacular displays of the northern and southern lights as they bounced off our planet’s atmosphere. The dazzling displays of the aurora borealis were visible much further south than they might normally be – and much further north in the case of the aurora borealis thanks to the strength of the geomagnetic storm, the so-called the strongest in two decades.

But while this surge of activity from the Sun left many on Earth shaken by the light display it produced, it also had a profound effect elsewhere in the Solar System. While most of us pondered the colors dancing across the night sky, astronomers were looking far beyond to see the strange ways such intense bursts of particles affect other planets and the space between them.

“The sun can shoot material in any direction like a garden sprinkler,” says Jim Wild, a professor of space physics at Lancaster University in the UK. “The effects are felt throughout the solar system.”

Our Sun is currently heading towards, or has already reached, its solar maximum – the point in the 11-year cycle where it is most active. This means that the Sun produces more bursts of radiation and particles from solar flares and events known as coronal mass ejections (CMEs). If they are sprayed in our direction, they can overpower the Earth’s magnetic field and cause beautiful auroras, but also cause problems satellites and power grids.

“Things seem to be getting better right now,” says Mathew Owens, a space physicist at the University of Reading in the UK. “I think we’re at solar maximum now, so we may see more storms like this in a few years.”

Several spacecraft are observing this increase in activity up close around the Sun. One of them, the European Space Agency’s (ESA) Solar Orbiter, has been studying the Sun since 2020 in an orbit that will take it into the orbit of Mercury. Currently, the spacecraft is “on the far side of the Sun as seen from Earth,” says project scientist Daniel Müller Solar Orbiter Mission in Esa in the Netherlands. “So we can see everything that Earth can’t see.

The storm that hit Earth in May came from an active region of solar flares and sunspots, bursts of plasma and twisting magnetic fields on the sun’s surface, known as its photosphere. Solar Orbiter was able to see “several eruptions from this monster active region that has rotated out of Earth’s line of sight,” says Müller, bright flashes of light and dark areas called sunspots on the Sun’s surface.

One of Solar Orbiter’s goals is to “connect what’s happening on the Sun with what’s happening in the heliosphere,” says Müller. The heliosphere is a huge bubble of plasma that surrounds the Sun and the planets of the Solar System as it travels through interstellar space. Where Müller and his colleagues hope to learn more is where the solar wind — the constant stream of particles pouring out of the Sun across the Solar System — “blows into the interstellar medium,” he says. “So we’re primarily interested in anything energetic in the Sun that we can find back.” solar wind turbulence.”

This particular cycle, cycle 25, appears to be “significantly more active than people predicted,” says Müller. relative number of sunspots – an index used to measure activity on the visible surface of the Sun – the shadowing of what was thought to be the peak of the previous solar cycle. “We predicted a maximum number of sunspots of 120 [a day]“Last month we maxed out at 270.

However, the effects of these changes in solar activity spread far across the solar system. Earth isn’t the only planet hit by solar storms as they churn through interplanetary space. Mercury, the planet closest to the Sun, has a much weaker magnetic field than Earth—about 100 times less—and lacks a substantial atmosphere. But solar activity can cause a planet’s surface shine with x-rays how the solar wind rains. Venus also lacks a substantial magnetic field, but the planet still produces auroras as the solar wind interacts with the planet’s ionosphere.

On Mars, the influence of solar activity is more apparent. This is where the NASA spacecraft called Maven (Mars Atmosphere and Volatile Evolution) has been studying the planet’s atmosphere from orbit since 2014. “We were on the waning side of the solar cycle 24 [then]” says Shannon Curry, a planetary scientist at the University of Colorado, Boulder, USA, and the mission leader. “We are now nearing the peak of cycle 25, and this latest batch of hotspots has produced the strongest activity Maven has ever seen.”

Between May 14 and 20, the probe detected extremely strong solar activity reaching Mars, incl X8.7 – solar flares are in the B, C, M and X rankings in order from weakest to strongest. The results of this event have yet to be studied, but Curry noted that previous X8.2 flares had resulted in “a dozen papers” published in scientific journals. Another eruption on May 20, later estimated to be the even larger X12, hurled X-rays and gamma rays toward Mars before a subsequent coronal mass ejection sent a stream of charged particles in the same direction.

Images beamed back from NASA’s Curiosity Rover on Mars have revealed that a large amount of energy has just hit the Martian surface. Streaks and dots caused by charged particles hitting the camera’s sensors caused images to “dancing with snow,” according to a NASA press release. Meanwhile, Maven captured the glowing aurora as the particles hit the Martian atmosphere, engulfing the entire planet in ultraviolet light.

The flare could cause the temperature of the Martian atmosphere to “increase dramatically,” Curry says. “It can even double in the upper atmosphere. The atmosphere inflates itself. The entire atmosphere expands tens of kilometers – exciting for scientists, but harmful for spacecraft because when the atmosphere expands, there is more drag on the spacecraft.”

The expanding atmosphere can also cause solar panels on spacecraft orbiting Mars to degrade from the direction increase in radiation. “The last two eruptions have caused more degradation than a third of a year would normally cause,” Curry says.

Mars, even though it has lost most of its magnetic field, still has “crustal remnant magnetic fields, little bubbles all over the southern hemisphere,” Curry says. During a solar event, charged particles can light them up and excite the particles. “The whole day side shines in what we call the diffuse aurora,” says Curry. “The whole sky is glowing. That’s what astronauts on the surface would most likely see.”

By the time solar storms reach further into the solar system, they tend to dissipate, but can still impact the planets they encounter. Jupiter, Saturn, Uranus and Neptune all have auroras which are powered in part by charged particles from the Sun interacting with their magnetic fields.

But one of the key effects of solar activity on interplanetary space that astronomers are eager to study is something called “slow solar wind“, a slower but denser stream of charged particles and plasma from the Sun. Steph Yardley, a solar astronomer at Northumbria University in the UK, says the solar wind is “generally classified around 500 km/s (310 mph)”, but slow the wind drops below this value It also has a lower temperature and tends to be more volatile.

Recent work by Yardley and her colleagues, using data from the Solar Orbiter, suggests that the Sun’s atmosphere, its corona, plays a role in the speed of the solar wind. Regions where the magnetic field lines, field direction, and charged particles are “open”—stretching out into space without a feedback loop—provide a highway for the solar wind to reach high speeds. The closed loops above some active regions – where the magnetic field lines have no beginning and end – can occasionally rupture to create a slow solar wind. The variability of the slow solar wind appears to be controlled unpredictable plasma flow inside the Sunwhich causes the magnetic field to be particularly chaotic.

X-class flares and coronal mass ejections observed in May transformed the interplanetary medium as they ejected material across the solar system. Solar Orbiter detected a huge increase in ions moving at thousands of kilometers per second immediately after the May 20 eruption. Computers on board other spacecraft – BepiColombo probewhich is currently on a seven-year journey to Mercury, and Mars Expressin orbit around the Red Planet—both experienced a dramatic increase in memory errors caused by high-energy solar particles impinging on memory cells.

Increased solar activity is a boon for scientists. “If you look at the number of papers produced by solar physicists, you can almost see an 11-year cycle there,” Owens says. “We are all more productive scientifically when there are plenty of activities to study.”

As the Sun continues into solar maximum, the Solar System will see more and more activity streaming from its surface. While all planets witness at least some of this activity, our planet bears the brunt more than most. “Earth is slightly unique in that space weather can have interesting effects on human technology,” says Wild. “There is another dimension here on Earth.

Perhaps one day these anthropogenic effects will be felt elsewhere. “If you’re going to go to Mars and you’ve had a six-month interplanetary flight, you’re potentially soaking up a lot of space weather events,” says Wild. “How you protect your astronauts is an interplanetary matter we need to think about.”

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