There is an invisible river that flows from the Sun to the Earth, a silent yet powerful torrent, which constantly hits us with billions of tiny charged particles shot at sidereal speeds. The solar wind, as physicists have romantically called it, is finally less mysterious thanks to a study of the Skoltech. These geniuses have in fact revealed the secret of coronal holes: those bizarre “black dots” on the solar surface that launch cosmic winds into space like enormous space garden hoses.
"Think of being in the garden and watering your beloved plants," says the professor Tatyana Podladchikova, author of the study. "If you stand directly in front of the hose, you get a really strong shower. But if you move to the side, you only get a few drops."
This explains, with an almost disarming comparison, why satellites aligned frontally to these solar flows record higher speeds than those further away.
The poetic (or almost) origin of the solar wind
The Sun, let's face it, is not just a giant cosmic light bulb: it also blows, and it does so with a certain force. Every second, billions of electrons, protons, and helium nuclei are hurled into space, traveling at hundreds of kilometers per second and showering the Earth with a constant barrage.
“Coronal holes” (the coldest and darkest areas of the solar corona) act as preferential highways for this cosmic wind. How? Thanks to magnetic fields that open up generously, letting whatever they want escape into interplanetary space.
It’s always surprising to think how something millions of miles away can affect us so much. When a fast stream of solar wind meets a slower one, giant vortices called “corotating interaction regions” form, which rotate around the Sun like a celestial spiral. Since our star rotates on its axis every 27 days or so, the same coronal hole can hit us repeatedly: a sort of cosmic metronome that marks the time of space weather.
Three factors that change everything
The research team has finally solved a puzzle that has kept physicists awake for a long time: Why do satellites positioned at the Lagrange point L5 and those in near-Earth orbit (L1) see different things? The answer lies in three fundamental ingredients: the size of coronal holes, their exact position on the solar surface, and (as if that wasn't enough) the latitude at which the satellites orbit.
"This effect is particularly evident in smaller coronal holes located at high latitudes," Podladchikova adds. "Larger holes are more democratic, spreading the solar wind quite generously throughout the heliosphere."
This >6° difference in coronal hole properties causes the fast solar wind to weaken at L1 relative to L5. Bottom panel: Combination of the small coronal hole at -35° latitude, the latitude of STEREO-B (+5,9°) and that of STEREO-A (-4,8°), creating a latitudinal difference of >10°, which reverses the predicted velocity trend, increasing the solar wind velocity at L1 relative to L5. Credit: Simulation of high-velocity solar wind flows from coronal holes using a Lagrangian point configuration L5-L1. Scientific Reports (2025). DOI: 10.1038/s41598-025-97246-2
The Garden Hose and Other Earth Stories
Why the garden hose metaphor? I answer with another question: why complicate things unnecessarily when you can explain everything with a simple garden hose? The solar wind works like this: if the satellite is straight in front of the jet, it is hit with full power, if instead it is positioned laterally, it receives little more than splashes. An almost domestic metaphor for a cosmic phenomenon that makes your head spin.
This thing, which seems little more than curious, actually has very serious implications: It is in fact essential to continue studying the Sun from various observation points, such as L5 and L4, to truly understand how profoundly our parent star influences the solar system.
Solar Wind: Not Just Stuff for Astrophysicists
The solar wind is not just a pastime for nerdy scientists. Its geomagnetic storms can in fact create real problems. What kind of problems? Disturb radio communications, disrupt satellites, put astronauts' health at risk and, in the most extreme cases, cause massive blackouts. Having a few hours or even a few days' notice to warn is therefore crucial to take effective countermeasures.
That's why all eyes are on the next ESA mission called VigilIt will be positioned right at the Lagrange point L5, which will act as a sentinel of the Sun, translating its eruptions into precious warnings for the Earth.
The study, recently published in the magazine Scientific Reports, represents a major step forward for space weather forecasting, but above all an invitation to continue exploring our solar system with greater curiosity and determination. Understanding how the solar wind works literally means protecting our fragile, technological way of life from the sudden and capricious outbursts of our favorite star.
