A stealth photo voltaic storm hit Earth on Nov. 20. It arrived with out warning and will have contributed to auroras seen at mid latitudes.
This occasion did not set off a geomagnetic storm; nevertheless, such photo voltaic storms, or coronal mass ejections (CMEs), are nonetheless thrilling as a result of they erupt virtually undetected and disrupt the photo voltaic wind situations round Earth. They’re usually extra frequent when the solar enters the declining part of its 11-year photo voltaic cycle, the periodic rise and fall within the solar’s magnetic exercise.
An everyday CME is often apparent in photo voltaic knowledge. These eruptions contain vibrant flares, sudden modifications in excessive ultraviolet mild or massive loops visibly lifting off the solar’s floor. Coronagraphs usually seize them as billowing cloudlike constructions emanating from the solar. Stealth CMEs are the alternative. They erupt quietly, with out flares or any vibrant signatures. They are usually faint, slow-moving and really arduous to trace. Due to that, scientists often solely spot stealth CMEs after they arrive at Earth and disrupt the solar wind.
That’s exactly what happened on Nov. 20, when NOAA’s Space Weather Forecasters reported that photo voltaic wind situations on Nov. 20 have been dominated by negative-polarity coronal gap high-speed stream with a potential “embedded transient,” which may point out a stealth CME.
The magnetic subject carried by the photo voltaic wind, usually round 4-6 nanoteslas, briefly spiked to 18 nanoteslas at 9:20 a.m. EST (1420 GMT) whereas photo voltaic wind speeds hovered between 400-500 km/s, larger than the same old background ranges that circulate close to Earth.
“Stealthy #solarstorms are again!” area climate physicist Tamitha Skov wrote in a post on X. “They’re stealthy as a result of they don’t have any signature in on-disk or coronagraph imagery. We solely detect them once they arrive at Earth. Count on solely minor storming with this one at excessive latitudes, however a few of them may cause sturdy storming once they launch close to high-speed streams.”
Stealthy #solarstorms are again! It could appear counterintuitive since we simply had a close to G5, however we simply had an early signal of Photo voltaic Minimal’s method! Proper now, a real “Stealth CME” is passing over Earth. They’re stealthy as a result of they don’t have any signature in on-disk or coronagraph… pic.twitter.com/a1eZClpeSFNovember 20, 2025
Auroras reported in a single day from mid-latitudes, together with Maine and Denmark, may have been the results of this stealthy CME mixed with the consequences of the quick photo voltaic wind stream from a coronal gap.
Aurora is seen into mid latitudes over North America proper now – that is the view from Maine. Lovely pink and sunlit blue/purple rays and pillars. Observe the Huge Dipper sitting over the northern horizon. pic.twitter.com/6huxCPzjsXNovember 20, 2025
The high-speed stream helped increase geomagnetic exercise barely, that means auroras stretched barely farther than their standard background high-latitude vary.
Aurora tonight 20/11 23:30 CET close to Hobro in Denmark. pic.twitter.com/eQhBlP1Gh8November 20, 2025
Why stealth CMEs matter
Stealth CMEs are a known challenge for space-weather forecasting. A 2021 study discovered that stealth eruptions can originate from quiet areas of the solar, but nonetheless produce sturdy magnetic signatures in area. The authors observe that stealth CMEs “pose many issues for area climate forecasting” as a result of their signatures are extraordinarily faint and require multi-wavelength, multi-angle observations to establish.
Stealth CMEs come up from quiet areas on the solar with weak, easy magnetic fields. Situations that grow to be extra frequent in the course of the declining part of a photo voltaic cycle.
“It could appear counterintuitive since we simply had a close to G5, however we simply had an early signal of Photo voltaic Minimal’s method!” Skov wrote on X.
