Forecaster summary - Issued 2021-03-21T00:05:01

The high energy electron flux (greater than 2 MeV) is currently measuring at background levels as the onset of the high speed stream from CH34/- has compressed the radiation belts. This high speed stream is expected to continue for several days, meaning that it may take a while for the radiation belts to rebound. A recovery in electron levels to reach high levels at the diurnal maxima is expected over the coming days, but there is low confidence in the timing of this increase. Corresponding 24-hour fluence is likely to rise above the Active threshold (1e8 integrated pfu), but again the timing is low confidence and there is a possibility this may not happen until near the end of the period.

The latest Met Office REFM output is currently suggesting fluence levels should gradually increase toward the Active threshold before rising above later on day 3 (23rd). On the last rotation the Active threshold was already breached on the equivalent of day 1 (21 March), however we experienced the onset a day later than on the last rotation. Given the current very low electron flux, the most likely onset of Active fluence is probably by day 3 (22 March) although as mentioned above this timing is low confidence.