Credits: XIIIfromTOKYO (Wikimedia Commons) / Wikimedia Commons — CC BY 4.0.
On 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. The origin was a geomagnetic storm rated G4 by the U.S. reference center for space weather, triggered by the arrival of a coronal mass ejection (CME) emitted by the Sun. Authorities emphasize the risk of disruptions for satellites behind the display. In addition, some communications can be affected. Ground infrastructures are rarely impacted.
A Night When Brittany Changed Color
On the Atlantic coast, the air seems still. Lighthouses cut the dark, villages switch off. And then, above a black horizon line, something rises that is neither cloud nor mist: a veil, a milky sheet, at first timid. Those who step out without much hope see little, sometimes almost nothing. But phone and camera sensors catch the color even when the aurora remains discreet to the naked eye: acidic green, diffuse pink aurora sheets and yellow in places.
In several towns of Finistère and Morbihan, the “hunt” is organized the old-fashioned way: country road, headlights off, silence, then the screens that light up. Further on, the Côtes-d’Armor and Ille-et-Vilaine report glows in turn, via images circulating at high speed. The event, first told by witnesses and amateur photographers, becomes a collective appointment: people lend a tripod, compare a long exposure, wait for a clearing.
Normandy, Same Glows, Same Reflexes
Further east, Normandy saw the same luminous wave. Same scenario: at first you think it’s an illusion, a city reflection, a streak of moisture. Then the photos confirm. The hues often appear 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 from us, on the line where satellites “taste” the solar wind before it hits Earth. On January 19, the U.S. solar weather forecasting center put January 20 (UTC) under watch. Indeed, that day was rated 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 strong solar flare (rated R3 for radio effects), launched from the Sun on January 18. The impact shock flipped the indicators to G4 as of January 19 at 19:38 UTC. In the following hours, activity remained fairly high. Thus, conditions stayed favorable for expansion. This 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 ejects, during peaks of solar activity, a cloud of plasma and magnetic field: the CME. When that cloud reaches Earth, it disrupts the magnetosphere, the magnetic shield that diverts 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 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: this “descending southward” is what allows, on some nights, auroras to be seen from France. We touch a modern paradox: what looks like a miracle to walkers is for engineers a reminder to stay vigilant.
Infrastructures Under Watch: Satellites, GPS, Radio, Grids
A G4 geomagnetic storm does not necessarily mean outages, but it widens the range of possibilities. U.S. authorities mention potential disruptions for satellites. In addition, communication links could be affected. Some services dependent on positioning and timing, including GPS, are also concerned. In the background, there is the issue of power grids: during strong episodes, induced currents can complicate operations, particularly at high latitudes.
The same episode came 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 concern first polar flights. Increased exposure for astronauts is also noted. In addition, the heightened risk for some space systems must be considered.
"Since 2003": The Value Of Doubt, The Power Of Dates
Comparisons come quickly, and the refrain is tempting: “the strongest since 2003.” Handle that carefully, because it all depends on what you compare. On the G scale, the episode reaches G4: severe, but not the theoretical maximum (G5). Very powerful events have been observed in recent years, sometimes at higher levels.
However, 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 here: date, 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’s a branch of risk prevention.
It also has limits. For the public, we mainly follow simple markers: aurora forecasts and the Kp index (the higher it rises, the more the auroral oval can extend). A CME can be spotted in solar imagery, but its magnetic structure—the one that makes the difference at impact—is really measurable only as it approaches Earth. Result: bulletins resemble terrestrial weather with terms like “watch,” “alert” and “probability.” Also, aurora forecasts are sometimes confirmed at the last minute. Uncertainty remains until the last moment. For the general public, that’s good news: you can look up without panic, but 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 to 20, the experience sometimes felt unfinished. Auroras are seen better away from lights, with a clear northern horizon, and especially when the sky is clear. The cold reminds you that you are not watching a screen: you are outside.
The most useful advice is also the humblest: if the eye sees only a gray veil, the photo can reveal green and pink. Conversely, an over-processed photo can lie. Between the two, there remains the moment: a few minutes when the night vault, usually so stable, takes on the movement of a sea.
What The Night Leaves Behind
In the morning, images keep circulating. They tell of a France that looks up, rediscovers darkness and patience, shares a common wonder. But they also recall something else: the Sun is not a stable lamp. It has its fits, its gusts, its silent rages.
The January storm did more than offer a show. For one night, it put infrastructure and vigilance back in the foreground. And it slipped, into everyday life, a larger truth: even at 200 million kilometers, a star can sometimes color our lives.