Credits: Stephan Sprinz / Wikimedia Commons — CC BY 4.0.
During the night of January 19 to 20, 2026, northern lights lit up the sky. They showed green, pink, and sometimes orange hues. In France, these phenomena were mainly visible in Brittany and Normandy. At the origin, a geomagnetic storm classified as G4 by the U.S. reference space weather center, triggered by the arrival of a coronal mass ejection (CME) emitted by the Sun. Authorities highlight the risks of disruptions to satellites behind the spectacle. In addition, some communications may be affected. Moreover, ground infrastructure is rarely affected.
A Night When Brittany Changed Color
On the edge of the Atlantic, the air seems motionless. Lighthouses cut through the darkness, villages go dark. And then, above a black horizon line, something rises that is neither cloud nor mist: a veil, a milky sheet, timid at first. Those who step outside without really believing in it see little, sometimes almost nothing. But phone sensors and cameras catch the color even when the northern lights remain faint to the naked eye: acidic green, pink northern lights in diffuse sheets, and yellow in places.
In several towns in Finistère and Morbihan, the “hunt” is organized the old-fashioned way: country road, headlights off, silence, then screens lighting up. Farther away, the Côtes-d’Armor and Ille-et-Vilaine report glows in turn, as images race around at high speed. The event, first told by witnesses and amateur photographers, becomes a collective gathering: people share a tripod, compare a long exposure, wait for a break in the clouds.
Normandy, Same Glow, Same Reflexes
Farther east, Normandy saw the same wave of light pass through. Same scenario: at first, people think it’s an illusion, a city reflection, a streak of moisture. Then the photos confirm it. The colors often seem more subdued than in Iceland or Norway: here, the aurora spreads in a band, it “breathes,” it moves slowly. The luckiest observers describe rippling curtains, like sheets lifted by a silent wind.
The episode is a reminder of a simple lesson: at our latitudes, beauty is often technical. You need a dark sky and an unobstructed view to the north to observe it properly. In addition, it is important to accept that the human eye captures less than photography does. That gap fuels misunderstandings: some people think they “missed” the phenomenon, when the images prove it was indeed there, discreet but real.
The Signal From the United States: A G4 Storm
The heart of the story plays out 1.5 million kilometers from us, along the line where satellites “taste” the solar wind before it hits Earth. On January 19, the U.S. space weather forecasting center placed January 20 (UTC) under surveillance. Indeed, that day is classified G4: a severe level on a scale from G1 to G5.
According to that center, the immediate cause is the arrival of a CME associated with a high-intensity solar flare (classified R3 for radio effects), which left the Sun on January 18. The impact itself pushed the indicators to G4 as of January 19 at 7:38 p.m. UTC. In the hours that followed, activity remained fairly high. Thus, this helped maintain favorable conditions for expansion. That expansion concerns the auroral oval toward unusual latitudes.
Why The Sky Ignites, Without Fire Or Smoke
An aurora is not a flame. It is a collision. The Sun sometimes sends out, during peaks of solar activity, a cloud of plasma and magnetic field: the CME. When that cloud reaches Earth, it shakes up the magnetosphere, the magnetic shield that deflects part of the particles.
A fraction of those particles is guided toward the polar regions along field lines. There, in the upper atmosphere, they excite atoms of oxygen and nitrogen. Light is born when those atoms return to their normal state. Green is the most common. However, red and pink appear under certain conditions. The shades depend on altitude, air density, and the energy involved.
When the event is strong, the auroral oval widens: it is this “moving south” that allows, on some nights, aurora France sightings. We then encounter a modern paradox: what looks like a miracle to stargazers is, for engineers, a reminder to pay attention.
Infrastructure Under Watch: Satellites, GPS, Radio, Networks
A G4 geomagnetic storm does not necessarily mean outages, but it broadens the range of possibilities. U.S. authorities mention potential disruptions to satellites. In addition, communication links could be affected. Some services that depend on positioning and timing, including GPS, are also concerned. In the background, there is also the question of power grids: during strong events, induced currents can complicate operations, especially in high-latitude areas.
The same episode comes with another, less visible and more technical signal: a solar radiation storm classified S4 (severe level) was reported on January 19. The U.S. center points out that such a level is rare. The impacts concern polar flights first and foremost. Increased exposure for astronauts is also noted. In addition, the heightened risk to certain space systems should be considered.
“Since 2003”: The Value Of Doubt, The Power Of Dates
Comparisons come fast, and the refrain is tempting: “the strongest since 2003.” It should be used with caution, because everything depends on what you are comparing. On the G scale, the episode reaches G4: that is severe, but not the theoretical maximum (G5). Very powerful episodes have been observed in recent years, sometimes at higher levels.
By contrast, an S4 level on the S scale is rare enough. Authorities compare it to the October 2003 storms. Those storms, nicknamed “Halloween,” still serve as a historical benchmark. That is the good journalistic practice: date it, specify the scale, avoid naked superlatives.
Space Weather, A Quiet Public Service
What the January episode reveals, beyond the photos, is a collective dependence. Our societies live in a thin technological layer: telecom satellites, Earth observation, network synchronization, navigation, aviation. Space weather is no longer just an astronomers’ topic; it is a branch of risk prevention.
It also has its limits. For the public, the main reference points are simple: aurora forecasts and the Kp index (the higher it is, the more the auroral oval can expand). A CME can be spotted in solar imagery, but its magnetic structure—the part that makes the difference at impact—can really only be measured as it approaches Earth. As a result, bulletins resemble Earth weather with terms like “watch,” “warning,” and “probability.” In addition, aurora forecasts sometimes hold up only at the last minute. Uncertainty remains until the very end. For the general public, that is good news: you can look up without panic, but with the awareness that the spectacle has another side.
Northern Lights To The Naked Eye: What Color Should You Expect?
For those who tried their luck on the night of January 19 to 20, the experience sometimes left a sense of something unfinished. Auroras are easier to see away from city lights, with a clear northern horizon, and especially when the sky is clear. The cold is a reminder that you are not looking at a screen: you are looking outdoors.
The most useful advice is also the humblest: if the eye sees only a gray veil, the photo may reveal the green and pink. Conversely, a photo that is too saturated can lie. Between the two, there is still the moment: a few minutes when the night sky, normally so still, takes on the movement of the sea.
What The Night Leaves Behind
By morning, the images are still circulating. They tell the story of a France that looks up, rediscovers darkness and patience, and shares a common sense of wonder. But they also remind us of something else: the Sun is not a steady lamp. It has its fits, its bursts, its silent rages.
January’s storm did more than offer a show. For one night, it put infrastructure and vigilance back in the spotlight. And it slipped a broader truth into everyday life: even 200 million kilometers away, a star can sometimes color our lives.