The European Solar Orbiter probe has traced one of the sharp turns that occur in the Sun’s magnetic field back to the region where it originated, using the chemical composition of particles that passed through its instruments. The finding explains how these phenomena arise and evolve in the solar wind, after decades of questions about their source.
European Space Agency links switchback to its solar source
The European Space Agency announced the findings on 8 October 2026, alongside the publication of a study in Nature Astronomy. The achievement goes beyond imaging the phenomenon’s twisted shape: it links a direct measurement made in space to a specific region in the Sun’s atmosphere, while bringing together two explanations that had competed to account for how it forms.
Known as magnetic switchbacks, these phenomena are sudden changes in the direction of the magnetic field carried by the solar wind, the continuous flow of charged particles released by the Sun. Earlier probes recorded them, and the US Parker mission later showed that they are widespread near the Sun, without resolving all the details of how they form.
Solar Orbiter captured an image in 2022 of a switchback shaped somewhat like the letter ‘S’, but identifying the source of the particles associated with these phenomena remained a separate challenge. As it passed through a large switchback, the probe was at a distance approaching half the separation between Earth and the Sun, allowing it to take direct measurements of the particles’ composition.
Chemical fingerprint identifies source of particles in the solar corona
A team led by Jesse Coburn, a researcher at the French National Centre for Scientific Research and the Plasma Physics Laboratory, analysed a mixture of oxygen and carbon ions. The charge states carried by these ions showed that the particles came from extremely hot magnetic loops in the solar corona, rather than from winds formed randomly during their journey between the planets.
This fingerprint supports a process known as interchange magnetic reconnection. In this process, open magnetic-field lines extending into space meet closed lines shaped like arcs, and their connections are rearranged. This releases material trapped inside the magnetic loops, sending it outwards in the solar wind.
Waves and turbulence reshape the switchback during its journey
But the switchback’s formation near the Sun does not mean it retains the same shape throughout its journey. The team found evidence of waves and turbulence affecting the particles after they left the solar corona.
Stephanie Yardley, a co-researcher at Northumbria University, said the two mechanisms are not contradictory: reconnection launches the phenomenon first, while waves and turbulence then govern its evolution as it moves through space. The scientists used the Solar Wind Analyser aboard the probe, along with images of the Sun and data from NASA’s Solar Dynamics Observatory.
They also used a model linking particle measurements to the regions from which they were released, showing that the solar wind can retain information about its original environment even after travelling millions of kilometres.
Daniel Müller, the European Space Agency’s Solar Orbiter project scientist, said understanding these links would help prepare for severe space-weather conditions that could affect satellites and technological infrastructure. The study cannot currently predict solar storms precisely, but it adds a tool for understanding the transfer of energy and matter from the Sun to regions near Earth.
