Space Weather Forecast Headline: New potentially Earth-bound Coronal Mass Ejection (CME). Minor/Moderate (G1/G2) geomagnetic storm possible Monday 17 August.

Analysis of Space Weather Activity over past 24 hours

Solar Activity: Activity increased to Low, with a long-period Common-class flare from a sunspot region on the southwest of the Sun peaking at 14/0701UTC. This flare was associated with a burst of energy in the radio spectrum and a CME - this CME has yet to be analysed pending imagery.

There are currently up to seven sunspot regions on the Earth-facing side of the Sun. The largest and nominally most complex region is now approaching the central solar meridian and manifests as an areally growing and spreading group, with proliferation of central spots. The other main group, mainly inferred from activity, has been the one in the southwest, with the narrowing viewing angle beginning to impair analysis as to its complexity.

In addition to the peak x-ray flare-related CME discussed briefly above, additionally and more significantly, a large 'filament' (arc of plasma) forming a U-shape around a centre near S10E020 lifted off the Sun from around 14/0400UTC. The ejecta was visible on extreme UV satellite imagery as visibly intersecting the Sun-Earth line. The associated flare was weak and was interrupted by the larger Common-class event on measuring instruments. An early assessment of this larger CME suggests a most likely arrival time in the first half of the UTC day of Monday 17 August. This is likely to be refined as further imagery becomes available.

Solar Wind / Geomagnetic Activity: Solar winds showed a probably slow regime, with solar wind speeds falling from slightly elevated highs to dip into Background late in the period. The number of particles in the solar wind was below average on a roughly level trend. The associated magnetic field was mostly weak, rising to a mid-period peak. The north-south component was erratic in character, with a slight bias towards being anti-aligned with Earth's field (usually to greater geomagnetic effect).

The net result of the above solar wind measures was for mainly quiet but slightly rising activity.

Energetic Particles / Solar Radiation: No solar radiation storms were observed, with no enhancement tied to increased western solar hemisphere x-ray activity.

Four-Day Space Weather Forecast Summary

Solar Activity: Activity will most likely remain low, however there is now a relatively increased daily slight chance of Moderate-class flares given a slightly more complex facing side of the Sun and recent flaring.

Solar Wind / Geomagnetic Activity: There are two new CMEs undergoing assessment at present. Foremost of these given its visible extent and emission location is the 14/0400UTC 'filament eruption' from the southeast. This event carries some uncertainty given the intervening fast solar wind that is forecast but has yet to occur. This is an unknown - affecting how much the interplanetary medium affects the CME (slows or impedes its transit). This fast wind is the only other feature in the forecast, and may bring a chance of Minor Geomagnetic Storm G1 in the next 24 hours. As a first estimate for the central CME using limited imagery, G1 is likely from earlier in the UTC day of Monday 17 August, with perhaps a chance of G2.

Energetic Particles / Solar Radiation: Solar radiation levels showed no measurable reaction to increased activity from the sunspot region in the southwest. There is a daily slight chance of Minor Solar Radiation Storm S1 or greater, revised slightly higher than of late in light of increased activity.