ESA’s Solar Orbiter mission has made a new connection between a puzzling feature of the solar wind and activity at the Sun itself. The spacecraft flew through a large magnetic “switchback” — an S-shaped reversal in the solar wind’s magnetic field — and sampled particles whose composition points back to hot magnetic loops at the solar surface.
The finding matters because switchbacks are part of the Sun’s changing magnetic environment. Understanding how they form could improve scientists’ picture of how solar material and magnetic fields are released into space, processes that help drive space weather and can contribute to hazardous solar storms.
A close sample of a magnetic kink
The solar wind is a continuous outflow of hot, electrically charged plasma from the Sun. It carries magnetic-field lines outward through the Solar System. Those lines do not remain smooth: they can bend, fold, snap and reconnect. A switchback is one such distortion, in which the direction of the magnetic field briefly reverses.
Solar Orbiter had previously observed a switchback remotely in 2022 and confirmed that the structure was S-shaped, a geometry researchers had predicted. In the newer observation, the spacecraft passed through a particularly large switchback. That gave its instruments an opportunity to examine the plasma inside rather than infer its makeup from afar.
At the time of the encounter, Solar Orbiter was about halfway between Earth and the Sun. Its Solar Wind Analyser instrument measured the charged particles within the structure, including oxygen and carbon ions. According to ESA, the mix carried signatures that could only have been produced in hot magnetic loops close to the Sun’s surface.
Evidence for interchange reconnection
Scientists have been debating how switchbacks form, and the observation does not support a simple either-or answer in every detail. But the sampled particles provide evidence for a process known as interchange reconnection.
In that process, magnetic field lines rooted in closed loops near the Sun reconnect with field lines that extend outward into interplanetary space. The rearrangement can allow plasma associated with the hot loops to escape along open magnetic routes, carrying a compositional record of where it originated. ESA describes the measured ion mixture as the “smoking gun” for this formation mechanism.
The result is important beyond a single curved feature in the solar wind. It links structures seen well away from the Sun to magnetic activity at the surface, where fields are constantly being reshaped. That relationship helps scientists test models of how the solar wind is generated and why it can contain abrupt magnetic reversals.
Why the Sun’s magnetic behavior matters
The Sun’s magnetic field governs much of its outward behavior. It influences the solar atmosphere, guides streams of plasma and plays a central role in eruptions that can send energetic particles and magnetic disturbances through space. When solar activity reaches Earth, it can affect satellites, radio communications, navigation services and power systems.
Switchbacks are not themselves a forecast of a particular solar storm. Their value is scientific: they are natural probes of the magnetic processes that shape the solar wind. By tying one of these structures to plasma from hot surface loops, Solar Orbiter gives researchers a direct clue about the mechanisms operating near the Sun.
The mission was designed to combine close-up measurements of the solar wind with observations of the Sun and its magnetic environment. Its trajectory and instrument suite allow researchers to connect local particle data with larger structures in the solar atmosphere. The new result demonstrates the value of that approach: a spacecraft encounter far from the solar surface can still preserve evidence of conditions at the structure’s source.
Next steps for solar-wind research
The observation adds to a growing effort to resolve how the solar wind is accelerated and structured. Researchers will need further encounters and measurements to determine how common this particle signature is across different kinds of switchbacks and solar conditions.
For now, Solar Orbiter has supplied a rare in-situ sample from inside a major switchback and a clear origin clue. The mission’s measurement of oxygen and carbon ions connects a fleeting magnetic kink in space to reconnection in the Sun’s outer atmosphere — an advance in tracing the restless magnetic architecture that extends from our star across the Solar System.
This article is based on reporting by esa.int. Read the original article.
Originally published on esa.int
