Forecaster summary - Issued 2021-04-15T00:14:17

The high energy flux (greater than 2MeV) as observed by GOES-16 is currently at background levels, and expected to persist at this level, until after the arrival of the fast solar wind stream of negative polarity CH45, expected during day 2 (16th). On the previous rotation, this feature led to a period of above Alert levels (above 1000 pfu). Whilst there is some uncertainty regarding the timing and strength of the connection on this occasion due to changes in the structure of the coronal hole, above alert flux levels are possible from day 3 (17th) at the peak of the diurnal cycle once any more significant geomagnetic activity has subsided. Further high speed stream influences are possible from negative coronal hole 46 later in day 4 (18th), bringing increased geomagnetic activity again, with further implications for electron counts.

The associated 24 hour fluence is forecast to stay at background levels for much of the period, and below the Active (1e8) threshold, as indicated by REFM. However, a rising trend is expected by day 3 (17th), with an increasing chance of reaching the Active threshold thereafter.