S1 – Minor Solar Radiation Storm Alert issued on September 5

An S1 – Minor Solar Radiation Storm Alert was issued by NOAA SWPC at 15:56 UTC on September 5, 2026. The alert was triggered after the integral flux of protons at 100 MeV exceeded 1 pfu, with the threshold being crossed at 15:52 UTC on the same day.

An S1 – Minor Solar Radiation Storm is the lowest level on the NOAA Space Weather Radiation Storm Scale. At this stage, there may be minor impacts on satellite operations and higher radiation exposures for spacecraft traveling at higher altitudes. No significant impacts to the general public or technology systems on the ground are expected at this alert level.

According to the latest SWPC Forecast Discussion, solar activity during the previous 24 hours was at low levels, with the largest events being C6.7 and C6.4 class flares from Region 4524. The proton event crossing the 1 pfu threshold at 100 MeV has occurred against a background of otherwise normal solar wind and geomagnetic conditions.