Forecaster summary - Issued 2025-12-21T00:33:40

Electron flux is expected to be at mostly high levels through Day 1 (21 Dec) as the recent fast winds of CH08/- continue to wane and the Van Allen belts are expanding back towards GEO. The next HSS from CH09/+ is expected to arrive during Days 1-2 (21-22 Dec) with strong wind speeds likely to extend into Day 3 (23 Dec), before waning Day 4 (24 Dec). This is likely to reduce electron flux at GEO as the Van Allen belts will be compressed again. Any response to the upcoming HSS is expected to occur after the end of this forecast period.

Electron fluence is expected to be at Active levels into the start of Day 1 (21 Dec). However, with the anticipated arrival of the next HSS, fluence levels should reduce quite sharply during Days 1-2 (21-22 Dec) with a recovery then probable after the end of Day 4 (24 Dec).  MOSWOC REFM is currently under-forecasting fluence levels and is suggesting an immediate reduction which is considered unlikely to occur on the immediate timescale. The reducing trend later in the period is reasonable, however.