A European spacecraft has traced a strange kink in the solar wind back to its source on the Sun. The solar wind is a flow of hot charged particles streaming away from the Sun, and it drags the magnetic field into space. Sometimes the field lines fold back on themselves in an S shape, forming what scientists call a switchback. In 2022, Solar Orbiter confirmed that a switchback really is S-shaped.
Now the spacecraft has flown through a very large switchback, about midway between Earth and the Sun. Its Solar Wind Analyser sampled the plasma inside. The team detected charged oxygen and carbon particles whose chemical signature points to hot magnetic loops at the Sun's surface. The lead author called this mix a clear fingerprint of a process called interchange reconnection. In that process, open field lines that stretch into space interact with closed loops, releasing material outward. Understanding this helps explain solar magnetism, the force behind dangerous solar storms.