Forecaster summary - Issued 2023-12-28T00:36:47

High energy electron flux (greater than 2MeV) observed by GOES16 just reached moderate levels at the diurnal maximum today. With one or more CME impacts possible on Day 1 (28 Dec), and with effects likely continuing into Day 2 (29 Dec), flux at GEO is likely to remain suppressed in the short term. Some increase is possible on Day 3 into 4 (30-31 Dec) after the CME effects have waned, but a potential high speed stream arrival later Day 4 will probably suppress flux levels once again. 

The associated 24-hour fluence is expected to persist below Active (1e8 integrated pfu) for the next couple of days, perhaps rising on Days 3 and 4, before a potential suppression later on Day 4. Once we see the level of geomagnetic activity from any CME effects by the end of Day 1 (28 Dec), we will have a better idea of the likelihood of a fluence increase later in the period. MOSWOC REFM will not be taking into account the possibility of CME arrival(s) in the short term, so although the below Active forecast is likely correct at first, it won't be able to forecast any potential increase later in the period until after the CME(s) have arrived.