Summary
Solar Orbiter traced a large magnetic switchback in the solar wind to hot magnetic loops at the Sun. The findings point to interchange reconnection at its origin, with waves and turbulence influencing its later movement through space.
ESA’s Solar Orbiter spacecraft has traced a large magnetic switchback in the solar wind back to hot magnetic loops at the Sun. By combining measurements of particles inside the kink with solar images and magnetic-field modelling, researchers identified interchange reconnection as the process that released the plasma. Their analysis also points to waves and turbulence shaping the switchback after it moved away from the Sun.
Reading the particles inside a switchback
The solar wind is a stream of charged particles, or plasma, flowing outward from the Sun. Its magnetic field can bend and fold as it travels through space. A switchback is an S-shaped kink in that field. Solar Orbiter confirmed the S-shape in observations reported in 2022; the new study connects a switchback to its source on the Sun.
The spacecraft flew through a particularly large switchback while roughly halfway between Earth and the Sun. Its Solar Wind Analyser instrument sampled the plasma, including charged oxygen and carbon particles. The researchers interpreted the specific mix of these particles as a fingerprint of hot magnetic loops at the Sun’s surface: the particles had been confined there before escaping into space.
To trace the source, the team combined the spacecraft’s particle measurements with images of the Sun’s disc and models of magnetic fields around the Sun and in space. A new model connected the Solar Orbiter measurements with observations from NASA’s Solar Dynamics Observatory, allowing the researchers to map the plasma back to its solar origin.
Reconnection at the Sun, turbulence farther out
The particle signature points to interchange reconnection. This occurs when an open magnetic region—whose field lines extend outward into space—interacts with a closed region, where field lines loop back to the Sun. As the fields meet and reconnect, plasma previously trapped in a loop can escape along newly opened lines.
The study also found signs of waves and turbulence. The researchers’ interpretation is that these processes play a role after the switchback has left the Sun, influencing how it moves through space. That suggests the two proposed explanations for switchbacks need not be alternatives: reconnection can help form them near the Sun, while waves and turbulence shape their subsequent evolution.
The result offers a way to connect conditions at the Sun with particles measured much farther away. The researchers say that the solar atmosphere leaves identifiable signatures in the solar wind, which could help scientists investigate how the Sun heats its atmosphere and accelerates particles. Understanding how the solar wind and its magnetic field behave also matters for studying space weather that can affect technology in space and on Earth.
The reconstruction concerns the large switchback Solar Orbiter sampled. It provides evidence for how this event formed and evolved, rather than establishing that every switchback follows precisely the same sequence. The study, “On the Coronal Origin of Magnetic Switchbacks in the Solar Wind,” was published in Nature Astronomy.