A cloud of solar plasma launched into space on September 28, 2026, is arriving at Earth on October 2, according to the U.S. National Oceanic and Atmospheric Administration (NOAA). The agency's Space Weather Prediction Center (SWPC) issued a G1-level "minor" geomagnetic storm watch for the day, the lowest category on NOAA's G1-to-G5 scale, a classification reported by Exame and CNN Brasil.
The September 28 eruption
The event began with the eruption of a solar filament — a dense ribbon of plasma and magnetic material suspended above the Sun's surface — stretching from roughly S10W50 to N45W50, according to data cited by the space-weather outlet The Watchers. The filament started lifting off at about 13:51 UTC on September 28, and the resulting coronal mass ejection was first detected at 14:36 UTC by the SOHO spacecraft's LASCO C2 coronagraph. The Watchers described it as a partial-halo CME roughly 200 degrees wide, moving at about 500 kilometers per second (311 miles per second).
Diário do Comércio reported that a separate, near-M-class solar flare rated C8.6 occurred around the same period in active region AR4535, producing an additional burst of plasma. The outlet said a first wave of material was expected to reach Earth on October 2, with a second CME potentially delivering a glancing blow on October 4.
NOAA's forecast for October 2
According to figures reported by The Watchers from SWPC's three-day forecast, the highest three-hour Kp index expected on October 2 is 4.67 — equivalent to Kp 5-minus, the threshold for a G1-minor storm — during the window of 15:00 to 18:00 UTC. The CME's arrival at Earth was estimated near 00:05 to 03:15 UTC on October 2, with an uncertainty window of about seven hours either way. Exame separately reported that the material was expected after two calmer geomagnetic days on September 30 and October 1.
Forecasts differ in confidence: The Watchers noted that a NASA ensemble model put a 95 percent probability on the maximum Kp index staying between 2 and 4 — below the G1 threshold — meaning the storm's final strength remains uncertain. Exame, citing NOAA, additionally reported a 10 percent daily chance of a minor R1-to-R2 radio blackout and a 1 percent chance of an S1-or-higher solar radiation storm around the same period.
A coronal hole adds to the picture
EarthSky reported that a coronal hole — a region where the Sun's magnetic field opens up and allows faster solar wind to escape — became visible on the Earth-facing side of the Sun around October 1. The outlet noted that observers described its shape differently, with some calling it heart-shaped. EarthSky said solar wind from this feature could reach Earth around October 3, potentially keeping geomagnetic conditions unsettled after the initial CME passes.
Timeline of the early-October 2026 solar activity| Event | Approximate timing | Reported effect |
|---|
| Filament eruption and CME No. 1 | Erupted Sept. 28, 13:51 UTC; arrival expected Oct. 2 | G1-minor geomagnetic storm watch; peak Kp forecast ~4.67 |
|---|
| C8.6 solar flare, region AR4535 | Late September 2026 | Near-M-class flare with an associated CME |
|---|
| Coronal hole fast solar wind | Visible on disk Oct. 1; effects expected ~Oct. 3 | Possible unsettled conditions, extended aurora chance |
|---|
| Second CME | Possible glancing arrival Oct. 4 | Additional minor geomagnetic activity, per Diário do Comércio |
|---|
What this means for technology and daily life
- No disruption to internet access, mobile networks or television broadcasts is expected, CNN Brasil reported, citing NOAA's G1 impact description.
- GPS navigation and high-frequency radio may show small, short-lived variations, mainly at high latitudes near the poles, according to CNN Brasil and Exame.
- Satellite operators could see minor operational effects, while power grids may experience only weak voltage fluctuations close to the poles, per Exame.
- Aurora may become visible farther from the poles than usual overnight around October 2, including at high northern latitudes, according to The Watchers and EarthSky.
Background: how NOAA grades geomagnetic storms
NOAA rates geomagnetic storms from G1 (minor) to G5 (extreme) based on the planetary Kp index, which measures disturbances in Earth's magnetic field. CNN Brasil and Exame both reported, citing NOAA, that G1 storms are the mildest and most frequent category, causing no damage to the public and only localized, minor technical effects. A filament eruption of the kind reported on September 28 becomes a CME once the plasma and magnetic field detach from the Sun and travel into space; when a CME reaches Earth, it can compress and disturb the planet's magnetosphere, which is what produces a geomagnetic storm.
Questions
- What caused the October 2, 2026 solar storm?
- A filament eruption on the Sun on September 28, 2026 released a coronal mass ejection (CME) that NOAA's Space Weather Prediction Center forecast would reach Earth on October 2, triggering a G1-level geomagnetic storm watch, according to The Watchers and Exame.
- Will the storm disrupt the internet, phones or power grids?
- No. CNN Brasil and Exame reported, citing NOAA, that G1-level storms do not cause internet, mobile network or television disruptions, and power-grid effects are limited to minor voltage fluctuations near the poles.
- Where might aurora be visible because of this storm?
- The Watchers and EarthSky reported that aurora could become visible farther from the poles than usual, including at high northern latitudes, overnight around October 2.
- Is a G1 storm dangerous?
- G1 is the lowest level on NOAA's five-step G1-to-G5 geomagnetic storm scale and is described by NOAA, as cited by CNN Brasil and Exame, as causing no harm to the public and only minor technical effects at high latitudes.
- Is more solar activity expected after October 2?
- Yes. Diário do Comércio reported a possible second CME grazing Earth around October 4, and EarthSky reported that fast solar wind from a coronal hole could keep geomagnetic conditions unsettled around October 3.
This piece was prepared with artificial intelligence and passed an automated source check before publication. If you see an error, ask for a correction. Request a correction or reply · How we make this
