New Study Reveals How Solar Coronal Holes Spray Solar Wind Like a Sun Garden Hose

Scientists from Skolkovo Institute of Science and Technology, together with scientists from the University of Graz, Kanzelhöhe Observatory, and Columbia University, have discovered how coronal holes — vast magnetic windows in the Sun’s corona — launch fast solar wind streams into space at supersonic speeds, shaping their flow throughout the heliosphere. These findings set the stage for the upcoming Vigil mission to Lagrange point L5 — a dedicated solar sentinel that will monitor our dynamic Sun, transforming deep-space observations into unprecedented early warnings of solar storms to protect critical infrastructure on Earth and in orbit. The study’s findings are published in Scientific Reports, Nature.

The Sun doesn’t just shine — it blows. A relentless stream of charged particles, known as the solar wind, surges outward at hundreds of kilometers per second, drenching Earth and the entire solar system in a flood of electrons, protons, and helium nuclei. But this isn’t a smooth breeze — it’s a turbulent river with fast and slow currents that spark dazzling auroras and disruptive geomagnetic storms. The fastest streams come from coronal holes — dark, cooler patches in the Sun’s outer atmosphere where magnetic fields stretch open and high-speed solar wind streams can escape from the Sun into interplanetary space. Yet how exactly these holes shape the solar wind’s behavior remains an open question. When high-speed solar wind streams collide with slower solar wind, they create massive structures called corotating interaction regions that spiral outward as the Sun rotates. Since the Sun rotates every 27 days, a single coronal hole can bombard us repeatedly — a celestial metronome of space weather.

A pioneering study led by solar physicists has revealed how coronal holes propel fast solar wind streams of charged particles that race across our solar system. The research also delivers a major advance in space weather forecasting, extending prediction lead times from hours to days. Using a unique observational vantage point at the L5 Lagrange point (60° behind Earth in orbit), scientists can now better predict when these solar winds will reach Earth. The team solved a key puzzle — why solar wind measurements differ between L5 and Earth-orbiting L1 observatories. They traced the variations to three critical factors — the combined effect of smaller coronal holes, their precise locations on the Sun’s surface, and the latitudinal position of spacecraft detecting the solar wind. These findings underscore the importance of future missions to L5 and L4 Lagrange points, like ESA’s Vigil, to improve early warnings for geomagnetic storms — helping protect satellites, aviation, and power grids from disruptive space weather.

“Imagine watering your garden with a hose,” explains lead author Associate Professor Tatiana Podladchikova, who heads the Engineering Center at Skoltech. “If you stand directly in front of the stream, you get hit hard. 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. Our study shows this effect is most pronounced for smaller coronal holes at higher solar latitudes, and depends strongly on the latitudinal separation between spacecraft. In contrast, larger coronal holes deliver solar wind more uniformly across the heliosphere.”

These findings will not only improve space weather forecasting and advance the fundamental understanding of the solar-terrestrial environment but also underscore the importance of continued exploration from diverse vantage points like L5 and L4 to fully unravel the Sun’s influence on the Solar System, enriching the broader field of heliophysics and space exploration.