Forecaster summary - Issued 2021-09-01T00:21:13

The high energy electron flux (greater than 2 MeV) as measured by GOES-16 at GEO has reached high levels over the last few days, though there has been a lower diurnal maximum each day and a shorter duration of high levels reached. It is likely that there will continue to be a declining trend over the next 24 hours or so, but still with flux levels rising to high at the diurnal maximum. There are uncertainties thereafter, with temporary electron flux suppression possible, associated with increased geomagnetic activity from a possible CME arrival on Day 1 (01 Sep). If we see this CME arrival, electron counts would be expected to rise to moderate to high levels again later in the period (Days 3 and 4).

The associated 24 hour fluence is currently just below the Active threshold with a decreasing trend and is likely to remain below the Active threshold over the next couple of days. Any re-enhancement is low confidence at this stage and heavily dependent on any increased electron counts in the wake of any CME activity. REFM guidance will be of limited use during this forecast period, especially beyond T+24 when it becomes primarily persistence based.