On November 20, 2025, Earth was struck by a rare and subtle solar storm, first detected by scientists at NOAA (National Oceanic and Atmospheric Administration). This stealth solar storm arrived without warning, triggering auroras visible much farther south than usual, including in areas like Maine and Denmark. This rare event, reported by Space.com, highlights how stealth solar eruptions, though barely noticeable at first, can still disrupt Earth’s magnetic environment and create spectacular displays for skywatchers.
What is a Stealth Solar Storm?
Stealth solar storms, or coronal mass ejections (CMEs), are a bit of a space weather mystery. Unlike typical CMEs, which often show up on solar imaging with bright flares and dramatic bursts of activity, stealth CMEs sneak up on us. They’re much harder to detect because they don’t show the usual signals like bright solar flares or sudden shifts in ultraviolet light.
Instead, these stealth eruptions quietly release solar wind that slowly builds up and then disturbs the magnetic environment around Earth. In the case of the November 20 storm, NOAA’s Space Weather Forecasters reported that the solar wind conditions were dominated by a “negative-polarity coronal hole high-speed stream” combined with an “embedded transient,” a term suggesting a stealth CME.
“Stealthy solar storms are back!” space weather physicist Tamitha Skov tweeted, adding that these storms often go undetected until they hit Earth.
Stealthy #solarstorms are back! It may seem counterintuitive since we just had a near G5, but we just had an early sign of Solar Minimum’s approach! Right now, a true “Stealth CME” is passing over Earth. They are stealthy because they have no signature in on-disk or coronagraph… pic.twitter.com/a1eZClpeSF
— Dr. Tamitha Skov (@TamithaSkov) November 20, 2025
Unexpected Aurora Displays
For most people, the most memorable effect of this stealth storm was the sudden appearance of auroras in places that don’t usually get them. Normally, auroras are confined to high latitudes, closer to the poles, but on November 20, the storm helped push the auroras southward, as far as Maine and Denmark. In Denmark, skywatchers reported striking red and purple auroras that stretched across the night sky, with the Big Dipper hanging over the horizon.
These auroras were likely the result of the stealth CME combined with a fast-moving solar wind stream from a nearby coronal hole. According to reports, the geomagnetic activity spiked just enough to make the auroras visible at lower latitudes than usual, delighting skywatchers who don’t often get such a show.
Aurora tonight 20/11 23:30 CET near Hobro in Denmark. pic.twitter.com/eQhBlP1Gh8
— Mikhaël Vervoort (@HaelVoort) November 20, 2025
The Challenge of Forecasting Stealth CMEs
These kinds of storms are particularly difficult to forecast because they don’t have the obvious signs that other solar eruptions do. Typically, CMEs can be tracked by observing large, bright loops or sudden flares on the Sun’s surface, but stealth CMEs emerge quietly, from regions of the Sun with weaker magnetic fields.
As noted in a 2021 study, stealth CMEs can still produce strong magnetic effects, even though their origins are harder to detect. To spot these sneaky eruptions, scientists need to use more sophisticated methods, including multi-wavelength and multi-angle observations. This means that often, by the time we notice them, they’ve already arrived and started affecting Earth’s magnetic field.