Space Weather Forecast Headline: Chance of Minor Geomagnetic Storm G1 into UTC weekend and into new UTC working week.

Analysis of Space Weather Activity over past 24 hours

Solar Activity: Activity remained Low, with isolated minor Common-class x-ray flares observed, peaking with a small event at 10/0050UTC from a sunspot region in the northwest.

There are currently up to eight sunspot regions on the facing side of the Sun, with the majority of these stable, magnetically unipolar regions. The most-changed regions on the disc included the most active in the northwest, which saw slight areal decay in its main leading spot, but then some central spot emergence. Also of note was a small collection of spots near the middle of the Sun, which for the moment appears as an otherwise simple magnetically unipolar group.

Satellite imagery in the period showed a faint emerging Coronal Mass Ejection (CME) signature from the western solar hemisphere from around 09/1600UTC. This has proven difficult to attribute to observed activity, and also to triangulate. A provisional assessment shows a weak feature as potentially arriving at Earth in the first half of the UTC day of Monday 14 September, i.e. beyond the four-day forecast horizon. This assessment will be revisited.

A more obvious 'filament' lift-off (arc of plasma leaving the Sun) occurred from the southwest (near S15W030) around 10/0315UTC. This is just becoming apparent in imagery and will be analysed in due course.

Solar Wind / Geomagnetic Activity: Solar winds showed a chaotic trace, comprising possible fading contribution from the tail-end of minor Coronal Mass Ejection (CME).

The solar wind speed was slightly elevated, with a overall slightly upward trend around mid-period. The number of particles comprising the wind was average to below average, falling overall. The associated magnetic field was mostly weak, with a variable but mainly anti-aligned north-south component (with Earth's field).

The net result of the above solar wind measures was slightly elevated geomagnetic activity, but below G1 Minor geomagnetic Storm throughout.

Energetic Particles / Solar Radiation: No solar radiation storms were observed.

Four-Day Space Weather Forecast Summary

Solar Activity: Solar activity is expected to remain low to very low. There is a gradually increasing slight chance of isolated Moderate-class x-ray flares, given up to two further regions' arrival over the eastern solar horizon over the UTC weekend.

Solar Wind / Geomagnetic Activity: The geomagnetic forecast is of low confidence, due to a non-recurrent 'coronal hole' fast wind and then a possible CME.

All considered, there is a chance of Minor Geomagnetic Storm G1 from a coronal hole later Friday 11 September, and then a slight chance of G1 from a second coronal hole and any minor CME effects at the very end of day four, Sunday 13 September, with the full effects probably falling a day later on Monday 14 September - with greater geomagnetic activity contingent on any CME and fast wind arriving at Earth at the same time.

Energetic Particles / Solar Radiation: There is a slight chance of further enhancements above the S1/Minor Solar Radiation Storm threshold given the most active sunspot region's westward progress and development.