Forecaster summary - Issued 2025-12-30T00:15:40

The diurnal oscillation in electron flux has remained above the high threshold over the past few days, and there are no likely mechanisms to reduce electron flux at GEO Day 1 (30 Dec) as geomagnetism has become mainly Quiet. Fast winds from CH10/- may connect with Earth on Day 2 (31 Dec), which would likely compress the electron belts and result in a reduction in electron flux to eventually Moderate or background levels. However, there remains some uncertainty regarding the timing of the onset of these coronal hole fast winds. A CME associated with the M4.2 flare at 28/2239 UTC from AR4317 is expected to arrive on the Day 3 (01 Jan), which should also help supress electron flux levels back below the Active threshold by the end of the period. 

The MOSWOC REFM forecast indicates a potential reduction in fluence by 30 Dec, but confidence in this scenario is low and assessed as unlikely. MOSWOC REFM recurrence is considered a more likely scenario, with current observed fluence running just below persistence but with a similar profile. As a result, an extended period of Active high-energy electron fluence is expected until the arrival of fast solar wind from CH10/- or the expected CME mentioned above. At that point, fluence levels are forecast to decline in response to reduced electron flux, potentially dropping below the Active threshold later on Day 2 (31 Dec).