Forecaster summary - Issued 2025-05-20T00:20:57

GOES-19 high energy electron flux is currently at High levels following recent CME and HSS enhancement. Flux levels are expected to be mostly Moderate with diurnal periods at High levels during the forecast period. There is some uncertainty in the extent of influence following recent connection to the large source region of CH48/+. Positive features remain slightly less favoured for strong connection this side of the solstice, and as we approach this date strong connections are less favoured in general, regardless of the polarity of the wind. This is supported by the limited geomagnetic response from this feature, once the initial activity from the glancing CME arrival 16-17 May had passed. However, given the strength of the wind, and that some limited geomagnetic enhancement was observed, there was likely still some charging of the Van Allen Belt. This is expected increasingly be observed at GEO through the period, with spells of High flux likely, especially during diurnal maximum.

There remains some uncertainty in the forecast story from late Day 1 through Day 2 (20-21 May), due to the potential weak re-connection to CH48/+ later Day 1 or on Day 2 which could briefly enhance solar wind strengths and increase solar wind pressure, helping constrain the bulk of the electrons to lower orbits, and suppressing the observed flux at GEO for a time, before rising again later in the period as solar winds ease. However this is very low confidence.

The associated fluence is currently below Active, but showing a rising trend, although much slower than MOSWOC REFM which is currently much too high with its forecast, especially initially, This rising trend is expected to continue, however, this is expected to remain just below the Active level given the uncertainties above, but with a chance of rising above for a time, most likely on Day 1 (20 May).