Space Weather Forecast Headline: Minor geomagnetic Storm G1 likely today, perhaps extending through midweek UTC.

Analysis of Space Weather Activity over past 24 hours

Solar Activity: Activity has been low, with a small peak Common-class x-ray flare at 12/0202UTC from the recent most-active region, now nearing the western solar horizon. 

There are up to eight sunspot regions on the Earth-facing side of the Sun. The main changes seen in the past 24 hours were an apparent areal decrease in at least the trailing spots of the aforementioned most active region, although this now lies close to the western solar horizon and has an unfavourable viewing angle. The largest region on the facing side approached the middle of the Sun, but showed little development.

Other regions were generally smaller, magnetically simple and stable, although a train of up to three regions arriving in the northeast may yet reveal further detail.

A Coronal Mass Ejection (CME) that left the Sun around 12/0500UTC from a large 'filament eruption' (arc of plasma) near S20E030 has been analysed and modelled. Forecast output indicates that although the bulk of the ejecta will pass behind Earth orbit, some flanking influence is likely on 14 October.

A further - smaller - disappearing filament was then observed at 12/1005UTC, also from the southeast at S10E030. This has also been modelled but is slow enough to lie outside the four-day forecast, perhaps serving to enhance UTC weekend activity, but is not a major forecasting consideration.

Solar Wind / Geomagnetic Activity: Solar winds indicated waning fast wind influence from a coronal hole. Solar wind signatures at the very end of the reporting period perhaps suggest a nearing inbound CME.

Solar wind speeds fell from early elevated highs to reach slightly elevated by the period's end. The number of particles in the solar wind was below average, but with a rising trend observed after mid-period. The associated magnetic field was weak but rising to moderate in the final hours. The north-south component of the field became more erratic after around 15Z, but did not spend significant tracts of time either co- or anti-aligned with Earth's field.

The net result of the above solar wind measures was for provisionally quiet geomagnetic activity throughout.

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

Four-Day Space Weather Forecast Summary

Solar Activity: There is a falling daily chance of Moderate activity should any isolated Moderate-class flares occur, most likely from the western solar horizon sunspot group at first, and perhaps then the one nearing the middle of the Sun.

Solar Wind / Geomagnetic Activity: There are up to three CMEs in the forecast: one from 10 October due imminently, one from 12 October due as a glance on 14 October, and a second minor 12 October CME that falls outside the four-day period.

Earth is now leaving a fast wind. A (second) fast wind is due on Tuesday 13 October. Any typical precursor solar wind density increase may combine with the 10 October CME to exacerbate geomagnetic activity, probably the peak for the forecast period as a whole.

G1 Minor geomagnetic storm conditions are likely in the current UTC day from the possibly combined effects of the 10 October CME and the fast wind, perhaps peaking at a slight chance of Moderate storm G2 - more likely earlier in the UTC day. These conditions may be extended in time by any glancing influence of the 12 October large 'filament' on Wednesday 14 October, before a more decided reduction in risk into the latter part of the UTC working week. Any third CME from the smaller 12 October filament falls outside the period.

Energetic Particles / Solar Radiation: There is a now-reduced daily slight chance of S1/Minor Solar Radiation Storms throughout the period.