Forecaster summary - Issued 2026-04-16T00:16:21

High energy (>2 MeV) electron flux at GOES19 reached high levels at the diurnal maximum in the last 24 hours. Flux is likely to remain moderate to high until the fast wind from CH42/- arrives either late Day 2 or Day 3 (17-18 Apr) with the anticipated strong wind speeds and increase in geomagnetic activity expected to cause a flux dropout. The fast wind is then likely to cause further charging of the outer radiation belt, but the solar wind pressure is expected to keep the belt compressed below GEO into Day 4 (19 Apr), with any significant rebound of electron flux unlikely to occur until after the end of this period.

The associated 24 hour fluence is now just above the Active (1e8 integrated pfu) threshold and is expected to remain at or near this level for the start of this period. However a dropout is likely, probably early on Day 3 (18 Apr), after the onset of the fast wind from CH42/-. MOSWOC REFM is currently underestimating the observed fluence and is likely to continue to do so in the coming days. The strong downward trend in recurrence values on Day 2 (17 Apr) was tied to CME activity for the equivalent period in March and is not a good guide for the timing of any dropout in the upcoming period.