Forecaster summary - Issued 2018-09-22T00:18:47

The high energy electron flux (greater than 2 MeV) at GEO will likely remain above the Active threshold, especially at the diurnal maximum, but may be reduced by the next coronal hole, due by Day 2 (23 Sep.), possibly persisting into Day 3 (24 Sep.). The corresponding 24-hour fluence values are also likely to remain above the Active threshold on Day 1 (22 Sep.), but may be temporarily reduced on Day 2 (23 Sep.)and Day 4  (24 Sep.) with the forthcoming high speed stream and geomagnetic activity.

The REFM forecast output continues to show a relatively rapid decline, which is probably overdone, however the recent arrival of a possible weak CME during the evening of 21 Sep. is likely to reduce the activity in the Van-Allen belts with a certain amount of decrease expected during Day 1 (22 Sep.). A more gradual decline is therefore forecast followed by a more marked decline for Day 2 on Sunday 23 Sep.. The 27-day persistence provides poor guidance due to 'contamination' as the near-Earth space environment was impacted by a CME on the previous rotation.