Electron 2 MeV Integral Flux Alert issued on December 18

An Electron 2 MeV Integral Flux Alert was issued at 11:06 UTC on December 18, 2025, after measurements recorded values exceeding 1,000 particles flux units (pfu). The alert, which continues from a previous notification, began at 14:05 UTC on December 17, 2025, and noted a maximum value of 1,632 pfu on the previous day.

Potential impacts noted in the alert include significant charging of satellite systems, resulting in an increased risk to those systems. Operators of satellite infrastructure should be aware of the heightened risk of surface charging and related operational issues while the elevated electron flux persists.

The event follows a period where the greater than 2 MeV electron flux briefly reached high levels with a peak flux of 1,020 pfu. This elevated flux is expected to remain at normal to moderate levels through December 18 with the possibility of renewed high levels on December 19 due to high-speed solar wind stream influences.