Forecaster summary - Issued 2021-05-18T00:02:46

The high energy electron flux (greater than 2MeV) as measured by GOES-16 at GEO, remained mostly at background levels. No significant enhancements are expected until the onset of CH59 and the subsequent increase in solar wind speeds. However, later on day 2 (19th), the electron flux should start to increase. Any geomagnetic activity is likely to bring the flux down, due to the compression of the Van Allen belt, but this should only be temporary and the flux is likely to be become high by the end of the day. 

The associated fluence is therefore expected to rise accordingly, with a chance of exceeding the Active threshold on days 3 and 4 (20th and 21st). This is currently not supported by the latest REFM output, despite having observed high levels of electrons on the previous rotation. For that reason, the REFM is considered to provide poor guidance beyond T+48, so forecast values beyond this period should be used cautiously.