This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: 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 outward 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 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 a new paper in Nature Astronomy.
"Because of this, we were able to sample rarely observed particles there that have telltale fingerprints of their origin." To make this connection, Coburn 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 Coburn. "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.
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