Forecaster summary - Issued 2025-08-18T00:20:37

GOES high energy (>2MeV) electron flux has been mostly high as the recent HSS from CH71/+ has waned. However, the onset of the next HSS from CH72/- during Day 1 (18 Aug) is likely to suppress electron flux levels at GEO as the radiation belt becomes compressed. Confidence becomes low during the period as there is the potential for a CME glance late Day 2 into Day 3 (19-20 Aug). That said, a resurgence in flux is possible later in the period as HSS effects from CH72 start to wane.

A continuation of Active fluence is expected until CH72's onset during Day 1, whereupon a sharp fall at GEO should occur. Fluence may not drop below the Active level until Day 2, however. The magnitude and timing of any eventual recovery is less certain, but there is a chance of fluence rising back above Active by Day 4 (21 Aug). MOSWOC REFM is persisting in significantly underplaying the current fluence level, being damped when compared with both persistence and also current observations. Despite this current poor performance, the drop in fluence that REFM is suggesting is likely to occur due to the next HSS onset.