Forecaster summary - Issued 2023-09-15T00:14:04

High energy (greater than 2 MeV) electron flux observed by GOES16 is expected to remain generally at Normal Background levels through much of the period. The rationale for this is the succession of fast winds should give a sustained period of elevated geomagnetic activity that will serve to compress the Van Allen belt inside GEO and lead to an apparent decline in populations. This will likely continue to be the case into Day 3 (16 Sep) with the expected CME arrival, with any electron response unlikely until later Day 3 or into Day 4 (17-18 Sep) after this passes and coronal influences ease.

The associated 24-hour fluence will most likely remain below the Active (1e8 integrated pfu) threshold for much of the period, however there is perhaps a Slight Chance by the end of the UTC weekend in a late recovery in fluence. MOSWOC REFM is considered to be giving good guidance in the near term, with current coronal holes likely to deliver a similar response to last pass, although the main period of interest is the 72 to 96-hour period, which falls outside REFM's range.