Forecaster summary - Issued 2019-02-19T00:07:30

The high energy electron forecast hinges on the onset of coronal hole 78, with the current Background-Moderate oscillation of the flux expected to continue until the coronal hole's onset, with this most likely at the very end of day one (Tuesday 19 February) or on day two.

Beyond this, a delayed rise in 24-hour integrated fluence is expected, although on balance, exceedence of Active seems relatively unlikely. In terms of evidencing this, Stereo A has recently seen a brief peak to around 450km/s. This satellite is sampling a higher solar latitude than Earth, but this coronal hole is relatively uniform north to south, and on last rotation Earth saw 600km/s speeds, with no exceedence of the Active threshold. It should be noted however that the starting fluence on this rotation is much higher prior to the coronal hole’s onset – something which may serve to compensate for the limited impetus.

So, while probabilities rise over the four days, the peak values are modest, perhaps a 30% chance by day three (Thursday 21 February).