Coronal holes are dark regions on the Sun seen in extreme ultraviolet and X-ray images. These areas have lower density and temperature and are key sources of fast-moving solar wind streams. While these streams don’t cause the strongest geomagnetic storms—those come from coronal mass ejections—they do trigger more frequent, medium-strength storms, which may contribute more total energy to Earth’s system.
Scientists from multiple institutions, including Skolkovo Institute and Columbia University, have uncovered how coronal holes launch solar wind streams into space at supersonic speeds. Their findings will support NASA’s upcoming Vigil mission at Lagrange point L5, which aims to provide early warnings of solar storms to safeguard Earth’s infrastructure. Understanding these processes could improve space weather predictions and their effects on our planet.
When fast solar wind streams collide with slower ones, they create massive spiraling structures known as corotating interaction regions, which move outward as the Sun rotates. Because the Sun completes a rotation every 27 days, a single coronal hole can repeatedly send high-speed solar winds toward Earth like a rhythmic pulse in space weather.
A new study by solar physicists has revealed how coronal holes propel charged particles into the solar system at extreme speeds. This improves space weather forecasts by extending prediction windows from hours to days. Scientists gained key insights using observations from the L5 Lagrange point, which sits 60° behind Earth in its orbit.
They solved a long-standing mystery—why solar wind measurements differ between L5 and Earth’s L1 observatories—by identifying three main factors: the influence of smaller coronal holes, their precise locations on the Sun, and the latitudinal position of spacecraft detecting the solar wind.
These findings underscore the significance of future missions to L5 and L4, such as ESA’s Vigil, which will provide early warnings of geomagnetic storms. This could help protect vital infrastructure like satellites, aviation, and power grids from space weather disruptions.
Lead author Associate Professor Tatiana Podladchikova, who heads the Engineering Center at Skoltech, said, “If you stand directly in front of the stream, you get struck. But if you’re off to the side, you only catch splashes.
This “garden hose effect” explains why satellites directly aligned with a solar wind stream measure higher speeds than those at an angle. The study reveals that this effect is most pronounced for smaller coronal holes at higher solar latitudes and is strongly dependent on the latitudinal separation between spacecraft. In contrast, larger coronal holes deliver solar wind more uniformly across the heliosphere.
Journal Reference:
- Podladchikova, T., Veronig, A., Temmer, M. et al. Simulating high-speed solar wind streams from coronal holes using an L5-L1 configuration of lagrangian points. Sci Rep 15, 12991 (2025). DOI: 10.1038/s41598-025-97246-2
