Forecaster summary - Issued 2018-01-12T00:28:37

The 24 hour high energy electron flux (greater than 2MeV) is currently at background levels. On the last rotation of the coronal hole there was a spike in the density and a fluctuation in the magnetic field ahead of the onset of the coronal hole high speed stream (CH HSS) suggesting a CIR. Although there is little from the STEREO A data to suggest a CIR on this occasion, an allowance has been made in the probabilities for a slight reduction in electron flux ahead of the onset of the CH HSS.

There was a sharp rise in electron flux in the HSS on the last occasion, but the coronal hole is smaller this time, the Earth is south of the ecliptic and consequently the HSS stream is likely to be slower at the Earth. Therefore high energy flux values are expected to be comparatively lower this time around.

The corresponding high energy fluence values are therefore expected to remain at background levels on day 1 (12 Jan). There is then a slight chance of reaching Active (1e8 integrated pfu) levels on day 2 (13 Jan), dependent on the strength of any CIR and the subsequent effect on electron flux levels. There is then a chance of the fluence reaching Active levels on day 3 or 4 (14 or 15 Jan) as the CH HSS becomes geoeffective.