Forecaster summary - Issued 2021-09-29T00:11:38

The high energy electron flux (greater than 2MeV) has been at background or moderate levels. While some increase is expected on day 1 (29th) it is unlikely to be enough to breach the 1e3 pfu High threshold or significantly elevate fluence levels close to the 1e8 Integrated pfu Active level. On days 2 and 3 (30th/1st) we are expecting geomagnetic enhancements due to the CME arrival. This will act to limit any increasing flux, due to the compression of the radiation belts from CME induced geomagnetic storms.

After the influence of the high-speed stream from coronal hole (CH05/+) and probable CME on days 2 and 3, then the flux would be expected to start increasing from Day 4 (2nd Oct), though confidence is low due to uncertainties surrounding the arrival time of the CME. 

Despite the REFM forecasting a steady increase 24 hour electron fluence values are forecast to remain below the Active threshold.