S1 – Minor Solar Radiation Storm Alert issued on July 31

An S1 – Minor Solar Radiation Storm Alert was issued on July 31, 2026, after the 100 MeV integral proton flux exceeded the alert threshold of 1 pfu. The alert was released by NOAA’s Space Weather Prediction Center and remains in effect as of the latest update.

S1 – Minor Solar Radiation Storms can lead to minor impacts on satellite operations and are monitored for potential effects on high-altitude flights and technology systems. According to the recent threshold crossing, the 100 MeV integral flux exceeded 1 pfu, confirming the alert conditions. No significant impacts to the general public are expected at this alert level according to official NOAA classification.

The event was triggered by a long-duration M1.9/Sf solar flare from Region 4492 (N16W74) at 17:00 UTC on July 30, accompanied by an approximately eight-degree-long filament eruption and several associated radio bursts. A partial-halo coronal mass ejection (CME) was also observed shortly after, further contributing to energetic particle enhancement.