Thursday, October 08, 2026

Solar Orbiter tracks origin of mysterious magnetic switchbacks

European Space Agency

Zooming in on a solar switchback — image:
The switchback spotted by Solar Orbiter in 2022 (bright blue-white feature extending to the left). The observation confirmed them to be S-shaped.
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Credit: ESA & NASA/Solar Orbiter/EUI & Metis Teams and D. Telloni et al. (2022)

The European Space Agency-led Solar Orbiter spacecraft has flown through an S-shaped kink known as a ‘switchback’ in the solar wind’s magnetic field. By fingerprinting the elusive particles within the switchback, Solar Orbiter has traced its origin back to the Sun’s surface and revealed more about solar magnetism – the unruly instigator of dangerous solar storms.

The Sun has an intense and restless magnetic field. This field not only governs the star itself but is also dragged outwards along field lines by the solar wind, a stream of hot charged particles (plasma) that continuously pours out from the Sun into space. These lines can twist, snap, or fold back on themselves on their journey through the Solar System. Together, the solar wind and its dynamic field lines create all kinds of exciting activity that we can study to understand what’s happening on and around our star.

Back in 2022, ESA reported that Solar Orbiter had spotted a kink in the solar wind’s magnetic field known as a ‘switchback’. While switchbacks have been spotted often near the Sun, scientists are still debating how they form. By watching from afar, Solar Orbiter helped solve a piece of this puzzle, confirming the switchback to be S-shaped: something scientists had predicted but not seen directly.

The spacecraft has now added another crucial piece to this puzzle by tracing a switchback back to its source at the Sun. “Solar Orbiter flew through a very large switchback,” says Jesse Coburn of CNRS/LPP, France, lead author of the new paper. “Because of this, we were able to sample rarely observed particles there that have tell-tale fingerprints of their origin.”

Not either-or, but both

To make this connection, Jesse and colleagues used Solar Orbiter’s Solar Wind Analyser instrument (SWA) to sample the plasma making up the switchback. At the time, Solar Orbiter was roughly halfway between Earth and the Sun.

They found a mix of charged oxygen and carbon particles that could only have formed in one way: within hot magnetic field loops at the surface of the Sun.

“There are two main competing theories for how a switchback, and by extension the solar wind, forms,” adds Jesse. “The specific mix of particles detected by Solar Orbiter is the smoking gun for a formation process known as 'interchange reconnection’.”

This kind of reconnection takes place when parts of the Sun with different magnetic properties interact. In the Sun’s atmosphere, open regions have field lines that stretch away like highways, allowing material to zoom along them into space. Closed regions have lines that initially extend into space before curving back to the Sun, creating closed loops. When an open region engages with a closed one, the lines can crowd together, snap open, and reconnect in different ways, allowing plasma that was previously trapped in a loop to escape to space.

This is what happened with this switchback – but that’s not all. The alternative theory of switchback formation involves processes related to waves and turbulence (the kind of waves that Solar Orbiter has found to play a key role in heating and accelerating the solar wind).

“Excitingly, we also see signs of these, but likely only after the switchback heads out into space,” says co-author Stephanie Yardley of Northumbria University, UK. “Once the switchback has left the Sun, waves and turbulence take over and govern how it moves.

“Overall, it seems that both processes – interchange reconnection and waves and turbulence – are involved in how switchbacks form and move through space. Our finding reconciles the two, showing that they simply operate at different stages in a switchback’s lifetime.”

From switchbacks to storms

To make the discovery, the researchers studied in situ observations of the switchback’s particles from Solar Orbiter’s SWA, analysed images of the Sun’s disc, and modelled the magnetic fields of both the Sun and surrounding space. They created a new model to identify where the plasma came from; this model connected the measurements from Solar Orbiter to data from NASA’s Solar Dynamics Observatory to reveal the switchback’s solar source in unprecedented detail.

Looking beyond switchbacks, the finding reveals how the Sun heats its atmosphere and accelerates solar wind particles into space. Furthermore, it shows that the Sun’s atmosphere imprints its signature onto the particles making up this wind, giving us a possible way to read the history of solar plasma even far from the Sun.

“As humans on Earth – and in space – our lives are entangled with what’s happening on our star. The solar wind ties the Earth to the Sun, and our understanding of its dynamics has key implications for how we keep our planet safe from extreme space weather events,” says Daniel Müller, ESA Project Scientist for Solar Orbiter. “The more we know, the better we can prepare for solar storms to protect our space-based infrastructure and technology.”

“This discovery just wouldn’t have been possible without Solar Orbiter – no other spacecraft has both the proximity to the Sun and the right instruments needed to make this connection. It’s a great example of the mission delivering exactly the kind of science we knew it could, connecting the Sun to its wider environment and revealing more detail about our star.”

Notes for Editors

‘On the Coronal Origin of Magnetic Switchbacks in the Solar Wind’ by Jesse T. Coburn et al. is published today in Nature Astronomy. DOI: 10.1038/s41550-026-02928-0

More about Solar Orbiter: https://www.esa.int/Science_Exploration/Solar_Orbiter

For more information, please contact

ESA Media Relations, media@esa.int

Journal

Nature Astronomy

DOI

10.1038/s41550-026-02928-0

Method of Research

Observational study

Article Title

On the Coronal Origin of Magnetic Switchbacks in the Solar Wind

Article Publication Date

8-Oct-2026

Infographic created after Solar Orbiter confirmed in 2022 that switchbacks are S-shaped.

Credit

Work performed by ATG under contract for ESA, based on data from ESA & NASA/Solar Orbiter/EUI & Metis Teams and D. Telloni et al. (2022); Zank et al. (2020).

The Sun, imaged by Solar Orbiter on 26 March 2022. Magnetic field loops visible at roughly the 2 o’clock, 4 o’clock, 8 o’clock and 10 o’clock positions.

Credit

ESA & NASA/Solar Orbiter/EUI Team

Healthy reef sounds can boost coral and fish recovery efforts

Two Scripps-led studies show how underwater sound can play a role in restoring degraded coral reefs and rebuilding fish communities

University of California - San Diego

Damselfish swim near artificial reef structure — image:
Damselfish swim near a separately located artificial reef “Stack” structure which were also used in the acoustic enrichment studies.
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Credit: Nina Schiettekatte

Coral reefs are renowned for their visual beauty, but for the marine life they support, their sounds may be just as enticing. Two new studies led by UC San Diego’s Scripps Institution of Oceanography reveal how underwater acoustic enrichment — the playback of sounds from healthy reefs — can help spur the recovery of degraded coral reefs and their fish communities.

These studies — one focusing on coral larvae, and the other focusing on fish larvae — are the first to field test the effects of underwater sound on fish and coral larvae simultaneously, alongside other restoration technologies including living materials and 3D-printed settlement surfaces. The research took place in Hawaii’s Kāne’ohe Bay, located off the island of O‘ahu, over several spawning events in 2023 and 2024.

“We have demonstrated in a single set of field studies that acoustic enrichment works in increasing the presence of both fish larvae and coral larvae on artificial reef structures,” said Scripps Oceanography researcher Aaron Thode, head of the Scripps Environmental Acoustics Lab and lead author of the coral larvae study.

Scripps Oceanography scientists led the studies in collaboration with the University of Hawai’i and other consortium partners of Rapid Resilient Reefs for Coastal Defense (R3D), a project focused on nature-based strategies to reduce wave energy, protect coastlines and improve coral resilience. The studies and broader R3D effort were funded by the Defense Advanced Research Projects Agency (DARPA).

Coral study

The newest study, published Oct. 8 in Communications Biology (part of the Nature Publishing Group), examines how acoustic enrichment affects coral larval settlement — the critical stage when free-drifting larvae search for a place to attach and begin building a reef. The research also demonstrates the potential of living materials and 3-D printed settlement surfaces to enhance coral settlement under natural spawning conditions.

“Our data indicate that when these drifting organisms detect a lot of sound from a reef, it signals to them that this is a good place to settle,” said Thode. “Our analysis also provided strong evidence that synthetic chemical cues attract these organisms to reefs.”

To start, the team collected sounds from a healthy reef environment off O‘ahu, Hawaii. Over the course of a lunar cycle, their recorder captured the sounds of fish and numerous other organisms, including shrimp and crustaceans that produce distinctive snapping noises. (Listen to the sounds of a healthy reef under the new moon, and the distinctive “purr” of a damselfish.)

The researchers then broadcast these recordings from an underwater speaker at the study site — a flat, sandy area off the small island of Moku o Loʻe. For two weeks, the speaker played the reef recordings from sunset to sunrise.

Around the speaker, the team placed 37 artificial structures on the seafloor, at a depth of 4.5 meters (15 feet) and distances between 1 to 42 meters (3 to 138 feet) away. The structures varied in design and surface properties, and included engineered microhabitats developed in Scripps researcher Daniel Wangpraseurt’s Coral Reef Ecophysiology and Engineering Lab.

These microhabitats were engineered in two ways: through their physical architecture, which created complex, protected settlement spaces, and through their living surface coating, made with BRINK — a bioactive “reef ink” containing living bacteria. BRINK was developed by former Scripps postdoctoral researcher Natalie Levy and colleagues in Wangpraseurt’s lab.

Across three experiments conducted over two years, scientific divers measured coral larval settlement one and two weeks after the new moon, when spawning occurs. Using a handheld blue light and yellow filter, they counted the individual larvae that had settled on each structure.

The experiments showed that the structures closest to the speaker had the highest levels of coral settlement. Among those, the structures treated with BRINK had the best results.

“The acoustics help, and with the living biofilm, it's a lot better,” said Thode. “When combined with structures that had crevices, acoustic enrichment worked very well for the coral larvae settlement.”

The study noted that specialized 3D-printed structures developed by colleagues at the Hawaiʻi Institute of Marine Biology also performed well, but those structures were only tested with sound alone and not BRINK. For future experiments, the team recommends combining acoustic enrichment with these more complex structures coated with BRINK for the best chance of coral settlement success.

“We now have evidence that several of these technologies can work in the field, which is a major step forward,” said Wangpraseurt, who is also UC San Diego’s lead principal investigator for the R3D project and a co-author of the study. “It brings us closer to the vision of hybrid reefs, a new class of living coastal infrastructure that combines engineering and biology to protect our shores while supporting the growth and recovery of reef ecosystems.”

Reef fish study

In a related study published recently in Scientific Reports, Scripps PhD candidate Océane Boulais and colleagues used custom-built autonomous cameras to document an increase in fish larvae during the same acoustic enrichment field deployments.

“Fish are important components of healthy coral reefs, because certain species feed on smothering microalgae that would otherwise make it difficult for coral larvae to settle and grow,” said Boulais, the lead author of the study.

Because fish are easily disturbed by humans, monitoring their activity while scuba diving presents a challenge, one Thode likened to “Godzilla trampling through a city and trying to get an accurate count of all the humans scurrying away.” As a solution to this problem, Boulais developed an array of low-power autonomous cameras capable of continuously detecting and counting fish larvae for up to three weeks.

Boulais positioned the cameras near the entrances of complex, 3D-printed structures that functioned as “fish hotels,” documenting fish as they entered and left while also tracking the presence of larvae.

“By developing these non-invasive cameras, we can essentially spy on the fish and observe a lot of their natural behavior,” said Boulais. “The autonomy and long-term monitoring design of these cameras enable us to observe which animals show up, and how long they stay.”

The cameras were deployed at two sites: one near the underwater speaker providing acoustic enrichment, and one at a control site where an identical speaker did not emit any sound.

Larval counts at both sites peaked around the new moon, but the acoustically enriched site attracted 4 to 14 times more fish larvae overall — a promising indication that the added sound helped draw young fish to the structures. The results held even when the team swapped locations of the true speaker and control speaker.

“The cameras are relatively new, but they’re already helping us learn so much about the early life stages of reef fish, and how sound might enhance their presence on a reef,” said Boulais.

Next steps

DARPA plans to install a $22 million hybrid reef structure off Oʻahu this fall, with corals likely to be outplanted in late 2026 or early 2027. The Kalaeloa Hybrid Reef will span 50 meters (164 feet) and incorporate technologies tested through the R3D program, including Scripps-developed microstructures and an acoustic enrichment system.

After installation, DARPA will transition ownership of the prototype living breakwater to the Hawai’i Department of Transportation, a transition partner for the R3D program.

More than 50 researchers and R3D consortium members contributed to the studies as co-authors. View the coral larval study and the fish larvae study online to see the full list of authors.

To learn more about Scripps-led acoustic enrichment research, visit Birch Aquarium’s Living Seas Tropical Pacific exhibit, which features samples of the reef sounds used in these studies.

– Approved for Public Release, Distribution Unlimited.