Forecaster summary - Issued 2023-06-17T00:10:37

High energy electron flux (greater than 2MeV) is expected to largely be at Background levels to start. The unexpectedly potent fast wind emanating from CH12 is now thought Likely to be able to provide the impetus for at least diurnal peaks within High flux. This may mean that Active 24-hour integrated fluence could come as early as day one, Saturday 17 June, although this is dependent on the brakes of recent Moderate geomagnetic activity lifting, allowing the charged Van Allen belt to recover to register fully at GOES16.

The revised forecast now proposes a significant upturn in flux and fluence through the coming UTC weekend, with exceedence of Active odds-on by Sunday 18 June. The trend thereafter depends on the uncertain contribution from a more diffuse trailing portion of CH12, which may extend its tenure on the disc and perhaps prolong geomagnetic activity and delay any eventual crossing of Active. The current forecast assumes that any contribution from this unnumbered feature is low.

MOSWOC REFM is showing a forecast trend in excess of that proposed by persistence, and this appears realistic, even if the exact timings are lower confidence.