S1 – Minor Solar Radiation Storm Alert issued on September 5

An S1 – Minor Solar Radiation Storm Alert was issued on September 5, 2026, at 16:33 UTC. The alert was released after the 10 MeV integral proton flux exceeded the 10 pfu threshold beginning at 16:15 UTC. This event marks minor intensity on the NOAA Space Weather Scale for Solar Radiation Storms.

At the S1 – Minor level, minor solar radiation storms may result in small-scale impacts to satellite operations and pose an increased radiation risk to astronauts on spacewalks. Commercial aviation at high altitudes and polar routes may experience slight increases in radiation, but significant effects are not expected for the general public or ground-based systems at this intensity level.

According to the latest forecast discussion from the NOAA Space Weather Prediction Center, the radiation storm did not directly follow major flare activity. The prior 24-hour solar activity was generally low, with the most significant events being a C6.4 flare that peaked at 10:45 UTC and a C6.7 flare at 19:30 UTC on the previous day, both originating from Region 4524. The immediate trigger for this alert was the sudden increase in proton flux rather than a specific recent solar flare event.