In November 2025, the sky put on a show. Auroras appeared at latitudes that almost never see them. Then a team of scientists went back through the data from that storm and found something nobody had seen before: GPS signals across the entire continental US were scrambled hard enough to throw positioning off by more than 10 meters, about 33 feet, in places.
If you run, hike, or race on a watch, that number should make you sit up. Because the same ionosphere that glitched precision farming and confused autonomous vehicles is the one your watch's GPS signals pass through.
What actually happened
The paper, by Endawoke Yizengaw and colleagues and published in Geophysical Research Letters, analyzed the November 12, 2025 geomagnetic storm. It peaked at G4 on NOAA's scale, which earned it the nickname "the Ugly Duckling storm" in a separate analysis. Not the strongest storm on record, but with an unusual side effect.
Multiple coronal mass ejections slammed into Earth's magnetosphere, and energetic particles rained down into the ionosphere, the layer of charged atmosphere that GPS signals have to travel through. That mixing created a huge band of enhanced electron density stretching nearly coast to coast, east to west, across the continental US. Along its edges, density changed sharply, exactly the conditions that produce small-scale irregularities in the signal path.
The effect has a name: amplitude scintillation. The best analogy is an old, uneven pane of glass. Light passing through it comes out distorted. Radio signals passing through a lumpy ionosphere come out scrambled, with strength fluctuating rapidly by the time they reach a receiver on the ground.
Scientists have seen this before, but only near the poles and around the equator, where the ionosphere is naturally rowdy. Mid-latitudes were considered calm. This storm pushed the auroral oval far enough toward the equator that the whole central US ended up inside the disturbance zone. Strong amplitude scintillation spanning this wide a band of longitudes has never been recorded before.
The dumb luck that saved American farming
The paper's most striking passage is about what didn't happen. The authors note that if the storm had hit during farming season, the positioning errors could have cost the American farming and transportation industries heavily.
That's not hypothetical. The May 2024 superstorm, the G5 that lit up skies worldwide, hit mid-planting. Farmers relying on GPS-guided equipment reported real disruption. When John Deere and other precision-ag systems lose position accuracy by meters, tractors plant crooked rows and the losses add up fast.
The November 2025 storm landed in the off-season. Same magnitude of atmospheric chaos, near-zero economic damage. The researchers call that out explicitly as a lesson: industries leaning on precise positioning are exposed to the Sun's schedule, not their own.
So what about your watch?
Here's the honest answer, split into two parts.
What you probably didn't notice: A 10-meter positioning error sounds enormous, and it is, if you're driving a tractor in a straight line or guiding a car without a driver. For a runner on a road, it's noise. Your pace reading is already noisier than that, thanks to sampling intervals, signal multipath between buildings, and wrist position. A solar storm of this scale would mostly show up as a slightly wobblier track, or a segment time a few seconds off. Nobody's marathon result ever hinged on 33 feet.
What matters for GPS watches is the timing. Amplitude scintillation happens when the receiver is struggling to hold the signal at all. Consumer watch chips are designed to degrade gracefully: they interpolate, they lean on accelerometers, they smooth the track. Precision agriculture receivers are trying to achieve centimeter-level fixes using correction signals that scintillation breaks completely. Your watch tolerates what a tractor can't.
The practical risk for watch users is the same as the one we've covered for garmin-coros/">GPS accuracy in dense environments: it's the moments where the receiver briefly loses lock and then re-acquires it that create the worst jumps in a recorded track. During a strong geomagnetic storm at high-to-mid latitudes, those lock drops become more likely, and your track might show a sudden leap or a phantom shortcut through a building. Not enough to ruin a race, plenty to annoy you on Strava.
Will multi-band help?
This is the question watch companies will eventually have to answer in marketing copy, and the honest answer is: somewhat.
Multi-band receivers (dual-frequency, tri-band) are designed to correct for ionospheric delay by comparing how the same signal travels on different frequencies. But that correction model assumes the ionosphere is a calm, predictable layer. What this paper documents is the opposite: a turbulent, rapidly changing plasma with density spikes changing on scales the correction models don't capture well.
Multi-band helps your watch in the ordinary case, where ionospheric delay is a slow, stable offset. Against amplitude scintillation, where the signal itself is flickering, no frequency combination can reconstruct data that isn't arriving. It's the difference between fog and a strobe light.
There's also the battery argument we've covered before: multi-band chips already cost meaningful battery life on a watch, and solar storms are rare enough events that no manufacturer is going to spend continuous power budget on a once-in-years scenario.
Should you worry about the next storm?
Probably not for your running data. Watch-grade GPS has survived every solar event of the last two decades without a user-facing crisis.
But the trend is worth watching. The paper's core message is about predictability: the Sun is at solar maximum now, mid-latitude ionospheric disturbances are being recorded for the first time at this scale, and industries from farming to autonomous driving are building deeper dependencies on precise positioning every year. The November 2025 storm got lucky with its timing. The May 2024 storm didn't. At some point, a big one will land at the worst possible moment, and everyone building on GPS is quietly hoping it isn't theirs.
For runners, the takeaway is simpler. If you see a bizarre jump in your track on a night when aurora photos are flooding your feed, you now know the ionosphere is the culprit, not your watch, not the app, and not your route.
Sources: Yizengaw et al., "Impacts of Mid-Latitude Ionospheric Dynamics on RF Applications During the November 2025 Superstorm Event," Geophysical Research Letters (2026); ScienceAlert (August 31, 2026); British Geological Survey geomagnetic forecast for November 12, 2025; MDPI Sensors analysis of the November 12, 2025 G4 storm.
Bottom Line
The November 2025 geomagnetic storm produced the first coast-to-coast amplitude scintillation event ever recorded across the mid-latitude US, bending GPS positioning by more than 10 meters in places. For precision agriculture and autonomous vehicles, that's a genuine vulnerability. For your GPS watch, it's mostly a wobblier track and a story for the running group. Multi-band helps with ordinary ionospheric delay but can't fix a signal that's flickering. And the next G4 might not land in the farming off-season.