Forecaster summary - Issued 2023-09-02T00:32:16

There is low confidence in this forecast, as it is very dependent upon the strength of the anticipated CME arrivals later day 1, and again on day 2 (02-03 Sep).   

High energy (greater than 2 MeV) electron flux observed by GOES16 is currently at background levels, but is likely to see some increase due to the current high speed stream from coronal hole 40, perhaps rising to Moderate later day 1 (02 Sep) before any drop out caused by the CME arrivals. These are likely to increase electron populations throughout the Van Allen belts, but initially compressing them into lower orbits. As the solar wind pressure eases, mainly day 3 onward (04 Sep), flux is expected to increase to become Moderate to High, and likely becoming persistently High into day 4 (05 Sep). A further suppression in observed flux is possible later day 4 from a further fast wind enhancement from CH42, however by this stage the forecast is very low confidence.

The associated 24 hour fluence is expected be below the Active (1e8 integrated pfu) threshold day 1-2 (02-03 Sep), but with an increasing risk of rising above day 3 (04), and likely rising above day 4 (05 Sep). MOSWOC REFM is currently good guidance until the CME arrival, but will likely become poor for a time, once this occurs.