Forecaster summary - Issued 2018-03-21T00:29:27

The high energy electron flux has remained highly elevated, reaching peak values of 22100pfu and leading to the electron fluence levels remaining above the (1e8 integrated pfu) Active threshold throughout the 20 March. These high flux levels are expected to persist on day 1 (21st) and into day 2 (22nd) with fluence levels also remaining elevated. Furthermore, with fluence levels currently showing a rising trend there is a chance of exceeding the Very Active threshold at some point during day 1, perhaps extending into day 2.

The main uncertainty during the period, is the extent of any reductions in the flux levels due to the occurrence of any geomagnetic activity from the various coronal hole features on the earth-facing solar disc. The first of these is likely to become geoeffective later on day 2, with a further more significant feature expected at some point either later day 4, or beyond the forecast period on day 5.  However the analysis of these features is very uncertain, as they are situated in an area of weak magnetic fields, and the general signal would be for any significant flux reductions to be temporary, albeit with a general decay of peak values through the period. Consequently there is a potential for Active fluence levels persisting through the period, but with a gradually reducing risk beyond day 1.