Forecaster summary - Issued 2018-05-10T00:14:11

The current high speed stream should continue to supply electrons to the Van Allen belts, keeping flux levels elevated, although any enhancements to geomagnetic activity could briefly reduce flux levels. As the risk of enhanced geomagnetic activity gradually declines during the forecast period, flux levels will tend to remain high while solar winds remain elevated.

Therefore, high energy electron flux levels are expected to remain at mainly high levels (above 1000pfu), and likely reaching very high levels (above 50,000pfu) at peaks of the diurnal cycle. 

The corresponding 24-hour electron fluence recently rose above the Very Active threshold (1e9 integrated pfu) and continues to rise slowly.  Electron ffluence is expected to remain above the Very Active threshold (1e9 integrated pfu) throughout the forecast period, showing a further slight rise earlier in the forecast period, before likely levelling off later in the period.

The REFM forecast is currently not verifying well with observations of fluence in the last 24 hours, with forecast values too high and showing a declining trend, while observations show a rising trend.  These opposing trends do mean that the gap between observed and forecast values is getting smaller, though this should not be interpreted as improving accuracy in the model forecast  The REFM forecast also shows a jump in fluence values early on day 2 (11th May) to values of over 1e11 integrated pfu.  This is considered highly erroneous and should be ignored; such fluence values are extremely unlikely to be reached, especially not over such a short time frame.  As stated above, fluence values in the coming days are likely to remain above the Very Active threshold, with an early slight rise followed by a levelling off, but remaining within the 10e9 order of magnitude.