On the night of January 19–20, 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. The cause was a geomagnetic storm rated G4 by the U.S. space weather center, triggered by the arrival of a coronal mass ejection (CME) emitted by the Sun. Authorities stress the risk of disruptions to satellites behind the display. In addition, some communications may be affected. Ground infrastructure is rarely impacted.
A Night When Brittany Changed Color
On the Atlantic shore, the air seems still. Lighthouses cut through the dark, villages go quiet. Then, above a black horizon line, something rises that is neither cloud nor mist: a veil, a milky sheet, at first shy. Those who step outside without expecting much see little, sometimes almost nothing. But phone and camera sensors catch the color even when the aurora is faint to the naked eye: acidic green, pink aurora in diffuse sheets, and yellow in places.
In several towns in Finistère and Morbihan, the “chase” organized the old-fashioned way: country roads, dimming headlights, silence, then screens lighting up. Further inland, the Côtes-d’Armor and Ille-et-Vilaine report glows in turn, as images circulate rapidly. The event, first recounted by witnesses and amateur photographers, becomes a collective rendezvous: tripods are lent, long exposures compared, a clearing awaited.
Normandy, Same Glows, Same Reflexes
Further east, Normandy saw the same luminous wave. Same script: at first you think it’s an illusion, a city reflection, a streak of humidity. Then the photos confirm it. The hues often seem more subdued than in Iceland or Norway: here the aurora spreads in a band, it “breathes,” it moves slowly. The luckiest describe undulating curtains, like sheets lifted by a silent wind.
The episode recalls a simple lesson: at our latitudes, beauty is often technical. You need a dark sky and a clear northern horizon to observe properly. Also, it’s important to accept that the human eye captures less than photography. This gap fuels misunderstandings: some think they “missed” the phenomenon, while images prove it was there, discreet but real.
The Signal from the United States: A G4 Storm
The heart of the story plays out 1.5 million kilometers away, on the line where satellites “sample” the solar wind before it hits Earth. On January 19, the U.S. solar weather forecasting center placed January 20 (UTC) under watch. Indeed, that day was rated G4: a severe level on a scale from G1 to G5.
According to the center, the immediate cause was the arrival of a CME associated with a strong solar flare (rated R3 for radio effects), launched from the Sun on January 18. The impact shifted indicators to G4 as of January 19 at 19:38 UTC. In the following hours, activity remained fairly high. This allowed conditions favorable to expansion to persist. That expansion concerns the auroral oval toward unusual latitudes.
Why the Sky Blazes, Without Fire or Smoke
An aurora is not a flame. It’s a collision. The Sun sometimes shoots a cloud of plasma and magnetic field during peaks of solar activity: the CME. When that cloud reaches Earth, it disturbs the magnetosphere, the magnetic shield that deflects some particles.
A fraction of those particles is guided toward the polar regions along field lines. There, in the upper atmosphere, they excite oxygen and nitrogen atoms. Light is produced when those atoms return to their normal state. Green is most common. However, red and pink appear under certain conditions. The shades depend on altitude, air density, and energy involved.
When the event is strong, the auroral oval widens: that “moving south” is what allows auroras to be seen from France on some nights. We then touch a modern paradox: what looks like a miracle to stargazers is a reminder to engineers.
Infrastructure Under Watch: Satellites, GPS, Radio, Grids
A G4 geomagnetic storm doesn’t necessarily mean outages, but it widens the range of possibilities. U.S. authorities mention potential disruptions to satellites. In addition, communications links could be affected. Some services dependent on timing and positioning, including GPS, are also concerned. In the background is the issue of power grids: during strong episodes, induced currents can complicate operations, especially at high latitudes.
The same episode comes with another, less visible and more technical signal: a solar radiation storm rated S4 (severe) was reported on January 19. The U.S. center notes that such a level is rare. Impacts mainly concern polar flights. Increased exposure for astronauts is also noted. Additionally, heightened risk for certain space systems must be considered.
"Since 2003": The Value of Skepticism, the Weight of Dates
Comparisons come quickly, and the refrain is tempting: “the strongest since 2003.” Use that carefully, because it depends on what you compare. On the G scale, the episode reached G4: severe, but not the theoretical maximum (G5). Very powerful events have been observed in recent years, sometimes at higher levels.
By contrast, an S4 level on the S scale is rare enough. Authorities liken it to the October 2003 storms. Those storms, nicknamed “Halloween,” still serve as a historical reference. Good journalistic practice is clear: date it, specify the scale, avoid unqualified superlatives.
Space Weather, A Low-Key Public Service
What January’s episode reveals, beyond the photos, is a collective dependence. Our societies live within a thin technological layer: telecom satellites, Earth observation, network synchronization, navigation, aviation. Space weather is no longer just an astronomer’s topic; it’s a branch of risk prevention.
It also has limits. For the public, people mainly follow simple markers: aurora forecasts and the Kp index (the higher it rises, the more the auroral oval can expand). A CME can be spotted in solar imagery, but its magnetic structure—the thing that makes the difference on impact—is really measurable only as it approaches Earth. Result: bulletins resemble terrestrial weather reports with terms like “watch,” “alert,” and “probability.” Also, aurora forecasts sometimes only confirm at the last minute. Uncertainty remains until the final moment. For the general public, that’s good news: you can look up without panic, aware that the show has another side.
Naked-Eye Aurora: What Color to Expect?
For those who tried their luck on the night of January 19–20, the experience sometimes felt unfinished. Auroras are better seen away from lights, with a clear northern horizon, and especially when the sky is clear. The cold reminds you you’re outside, not looking at a screen.
The most useful advice is also the humblest: if the eye sees only a gray veil, a photo may reveal green and pink. Conversely, an overprocessed photo can lie. Between the two, there remains the moment: a few minutes when the night vault, usually so steady, takes on the motion of the sea.
What the Night Leaves Behind
In the morning, images keep circulating. They tell of a France that looks up, rediscovers darkness and patience, and shares a common wonder. But they also remind us of something else: the Sun is not a steady lamp. It has outbursts, bursts, its silent angers.
The January storm did more than provide a spectacle. For one night, it brought infrastructure and vigilance questions to the fore. And it slipped a larger truth into everyday life: even at 200 million kilometers, a star can sometimes color our lives.