Scientists unlocked solar patterns that could help understand space weather - The Washington Post

The sun is more than a heat lamp for Earth. It is constantly spitting streams of solar particles our way and, sometimes, powerful pockets of solar material that can jolt our planet. Now, scientists are unlocking another puzzle piece on what may drive extreme solar activity, which could bombard Earth and disrupt our technology.

The missing piece could be linked to unusual patterns of high energy bursting from the sun’s surface, according to recent research.

We’re used to hearing about the sun’s ultraviolet radiation, which we protect ourselves against with sunscreen. The sun also emits much more powerful gamma rays, which are the most energetic waves on an electromagnetic spectrum. Each gamma ray photon carries a billion times as much energy as an ultraviolet photon.

Gamma rays don’t directly affect people on Earth’s surface because the photons are absorbed by our atmosphere. But scientists are investigating if some of these very energetic rays could trace solar activity, such as the sun’s powerful outbursts like solar flares or eruptions on its surface. Such strong events can create “space weather,” which can hit Earth, affect satellite operations and knock out railway or electric systems.

Predicting extreme solar events would be a huge improvement in our understanding of the sun, like predicting an earthquake before it strikes.

In a recent study, scientists found that some portions of the sun emit more intense gamma ray radiation than others — a surprising finding because models previously hinted that gamma radiation should be uniform across the sun. The latest research found the sun’s poles emitted the highest radiation during the moments the sun’s north and south magnetic fields flipped.

“It’s about having better tools to predict the solar activity,” said Bruno Arsioli, co-author and researcher at the University of Lisbon and University of Trieste. “Maybe we could use this new information from very high energies to help our models predict the behavior of the sun.”

The scientific reasoning for the strange orientation is still a mystery, the authors say. But the sun’s magnetic field is likely to flip in the next year or two, allowing the scientists to observe this oddity in real time and gather more data to explain the phenomenon.

Gamma rays are the kings of all energy. They are generated from the most energetic objects in our universe, such as supernova explosions or neutron stars. Nuclear explosions and lightning on Earth can also produce gamma rays.

The sun can also emit gamma rays through a few avenues. When an eruption on the sun sends off gas and plasma from its surface, gamma rays can also be emitted but in relatively small energy levels.

The bigger source of solar gamma radiation comes when very energetic particles emitted from supernova and neutron stars across the universe, called cosmic rays, bombard the sun. When the charged cosmic particle hits the sun, it gets turned around by the sun’s magnetic field and comes back out. On its way out, it hits gas on the sun’s surface and excites solar particles into gamma ray photons.

This gamma ray conversion, astrophysicist Tim Linden said, probably takes place 100 to 1,000 kilometers below the sun’s surface where the magnetic field is strong enough to turn the cosmic rays around.

“With gamma rays in the sun, we get to see a few thousand kilometers below,” said Linden, an astrophysicist at Stockholm University who was not involved in the new study. “That can give you a probe of what’s happening very deep below the solar surface.”

The sun’s activity is not constant. Every 11 years, our host star goes through a costume change where its north and south magnetic poles switch places, known as a solar cycle. As the poles flip, the level of activity at the sun’s surface changes. The sun is the least active at the beginning, known as a solar minimum, and most active around the middle when the magnetic poles officially flip, known as a solar maximum. The sun is expected to hit its solar maximum in the next year or so.

In the new study, researchers studied how the sun’s gamma radiation changed across an entire solar cycle, using data collected from NASA’s Fermi Gamma-ray Space Telescope. They found gamma radiation was the most intense at the sun’s poles as solar activity peaked during the cycle — coinciding when magnetic fields officially flipped.

“This was not expected,” said Arsioli. “It’s just something new we are finding out about the sun.”

The finding was surprising because the actual strength of the sun’s magnetic field doesn’t change much over the 11-year period, Linden added. During peak activity, the sun’s magnetic field becomes more tangled, which leads to more activity like flares and eruptions on the surface, but the overall strength doesn’t necessarily change.

“No one had any model that said that certain portions of the sun would be brighter than others as a function of the solar cycle,” but previous studies hinted at an unusual pattern, said Linden. He showed that certain areas of the sun are brighter than others in a previous study, but this new study analyzes the trends in more detail.

Now, the models and understanding of our sun’s gamma energies would need to be revised. Arsioli said because this lopsided structure shows up at the time the sun is going through its magnetic flip, the gamma rays could be connected to magnetic configuration and solar activity.

The exact explanation is still a mystery said Elena Orlando, a study author and researcher at University of Trieste and Stanford University. One idea could be the cosmic rays are hitting different regions during solar maximum. Or, perhaps, there is something special about the poles during solar maximum that attracts more cosmic rays to hit. There could also be a completely different explanation.

“This suggests that the gamma rays are carrying information about the solar activity,” said Arsioli. “It kind of opens up a new area to study this connection.”

Predicting an extreme solar event is like anticipating an earthquake. Processes below the surface start to shift and can trigger activity on the surface, but it’s difficult to forecast exactly when and where.

“This study helps extend our knowledge of where exactly on the sun’s surface the gamma rays are originating,” said particle physicist Mehr Un Nisa, who was not involved in the study.

Previous studies also hinted that gamma rays did not glow uniformly across the sun, but this is the first study to show a change during solar peak activity.

Gamma rays could help provide an early look at processes coming to surface and give clues about the overall condition of the sun, Orlando said. For instance, an increase in gamma radiation at the poles could signal the sun’s magnetic field is in the process of flipping and that the sun’s activity is increasing — leading to more solar eruptions that could hit Earth.

Future studies could also look at how gamma radiation changes before a large solar flare, Linden said, potentially using observations as a forecast tool — much like determining if it will rain on Earth from atmospheric conditions.

“The same magnetic fields that are responsible for modulating the high energy particles that produce these gamma rays are also responsible for the ebbs and flows of space weather,” Nisa said. “Regardless of whether life is disrupted by space weather, getting the physics of our nearest star right will only add to our knowledge of our place in the universe.”

This article is part of Hidden Planet, a column that explores wondrous, unexpected and offbeat science of our planet and beyond.

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