Forecaster summary - Issued 2025-09-09T00:09:47

High-energy (>2 MeV) electron flux observed by GOES-19 has been kept Low in the last 48 hours, suppressed by the combined influence of the HSS from CH75/+ and the 04 Sep CME arrival. The influence of the magnetic cloud is now waning. However, there is still a chance for geomagnetic activity to become enhanced at times (driven by the influence of the HSS from CH75/+) over the coming days. A resurgence in electron flux is likely later in the forecast period as the HSS effects wane and the radiation belt relaxes back towards GEO. Based on recurrence, diurnally high flux levels are considered likely, particularly from Day 2 (10 Sep) onwards.

However, confidence is low due to the low-latitude position of CH75, which may hinder the connection with Earth and lead to a muted geomagnetic response, potentially allowing flux levels to rise earlier than anticipated.

Fluence is currently below the Active (1e8 integrated pfu) threshold but is likely to display a rising trend during the period, with Active fluence becoming possible Days 2-4 (10-12 Sep). MOSWOC REFM is also showing a rising trend, but is most likely overestimating the peak values and is too quick to raise the fluence level.