Forecaster summary - Issued 2021-08-05T00:17:57

High energy electron flux (greater than 2 MeV) as observed at GEO by GOES-16 has increased from background levels to be persistently Moderate, as solar winds ease after the recent enhancement on the 2nd. Further Moderate flux levels, perhaps briefly peaking High, are likely during days 1 and 2 (5th and 6th), before the arrival of the fast wind of CH83 leads to the flux dropping out for a time. Whilst the strength of any connection to CH83 is currently low confidence, this is likely to charge the Van Allen belts to some degree, with flux levels at GEO rising again in response day 3 and 4, potentially reaching High levels, mainly at diurnal maximum. 

The associated electron fluence is currently rising in response to the increased flux observed on the 4th. Fluence levels are expected to remain below the Active threshold, but there is a slight chance of briefly rising above day 1 or 2 (5th or 6th). Whilst fluence values are expected to fall due to any dropout of flux on day 3 (7th), the following enhancement brings a chance of Active fluence by the end of day 4 (8th). The recent enhancement was not captured by REFM, likely due to its CME source, whilst CH83 is a new feature on this rotation and hence not known by REFM persistence data. Consequently REFM is currently giving poor guidance.