Space Weather Forecast Headline: G1-G2 (Minor-Moderate) geomagnetic storms likely Day 1 (17 Aug), chance of G1/Minor storms Days 2-3 (18-19 Aug). Chance of Moderate class flares. 

Analysis of Space Weather Activity over past 24 hours

Solar Activity: Solar activity has been Low, with several low-level Common-class flares.

There are currently four sunspot regions on the Earth-facing disc. The most complex region is in the western, central part of the disc. It has seen some growth in it's intermediate spots over the last few hours, though seems relatively stable in size overall. Another sunspot region, in the north-western part of the disc has seen some growth in recent hours,  and now displays a north-south configuration and has had some recent flare activity. All other sunspots regions are relatively small, stable and simple.

There was a Coronal Mass Ejection from a flare 16/1928 UTC which has been analysed to potentially give a glancing blow on Day 4 (20 Aug).

Solar Wind / Geomagnetic Activity: Solar winds, as measured at L1 by SOLAR-1, showed background conditions. Wind speeds were slow, generally around 300 km/s. The Interplanetary Magnetic Field, Bt, was Weak, but has been steadily increasing and is now Average. The north-south component, Bz, was weakly variable, but became generally negative for a time between 17/0200 UTC and 17/0900 UTC. Then it became weakly positive for a time. Geomagnetic activity has been Quiet (Kps 1-2).

Energetic Particles / Solar Radiation: GOES18 >10MeV proton flux was at background levels. 

Four-Day Space Weather Forecast Summary

Solar Activity: Activity will most likely remain Low, however there is a chance of Moderate-class flares.

Solar Wind / Geomagnetic Activity:  There are two Earth-directed Coronal Mass Ejectionss in the forecast. One from the filament eruption on 14 Aug is due to arrive during Day 1 (17 Aug), though the timing of this is uncertain. Enlil has not been modelling the solar wind speeds well and the ensemble has a wide range of onset times. A Coronal Mass Ejection from 16 Aug has been analysed with a slow speed, and may give a glancing blow on the morning of Day 4 (20 Aug) at around 0800 UTC. Again there is significant uncertainty with regards the timing and effects this may have.

On Day 2 (18 Aug) a new High Speed Stream may arrive, from one of the coronal holes in the north or south centre of the disc, which is likely to last into Day 3 (19 Aug). This is a complex feature that changed significantly on the previous rotation, with a sunspot region developing in the middle of the coronal hole during it's transit across the visible disc. It did give winds of up to 700 km/s on the last pass, but has changed so there is significant uncertainty in the wind speeds expected at this time. The Coronal holes are negative polarity, which is less favoured for geomagnetic response at this time of the year. Enlil suggests speeds of 550-600 km/s this time, but has not been doing well with wind speeds recently so they may be lower. 

Geomagnetic activity is like to start Quiet to Unsettled (Kps 1-3) on Day 1 (17 Aug), increasing upon arrival of the Coronal Mass Ejection later in the day to give likely G1/Minor Storm (Kp 5) intervals and a chance of G2/Moderate Geomagnetic storms (Kp 6). By Day 2 (18 Aug) the effects of the Coronal Mass Ejection are expected to gradually reduce, but onset of the High Speed Stream from the coronal holes may occur, keeping a chance of G1/Minor Storm (Kp 5) and a slight chance of G2./Moderate Geomagnetic storm (Kp 6)  into Day 3 (19 Aug). By Day 4 the influence of the Coronal Mass Ejection from 16 Aug is uncertain, but keeping a chance of G1/Minor storm (Kp 5). 

Energetic Particles / Solar Radiation: GOES18 >10MeV proton flux is likely to continue at background levels.