Space Weather Forecast Headline: Chance of Moderate Geomagnetic Storm G2 from later in UTC day 08 September, through midweek.

Analysis of Space Weather Activity over past 24 hours

Solar Activity: Activity has been Low, peaking with an isolated Common-class flare observed at 07/0901UTC from a sunspot region just east of the middle of the Sun. This event may have a (most likely slow) Coronal Mass Ejection (CME) associated with it, with imagery to assess this aspect awaited. It is possible that any such CME would have an Earth-directed component given its near-central emission location.

There are currently up to seven sunspot regions. Extreme UV imagery also hints at an emerging region on the northwestern solar horizon, although analysis has not been possible of any feature here due to the narrow viewing angle. Much of the facing side comprises simple, stable magnetically unipolar groups in visible light, however this is felt to belie some 'sub-surface' complexity, with more frequent and larger flares observed in the recent past than would perhaps be expected. Foremost amongst these visibly simple regions with heightened activity is the most active region in the northeast - any process that has led to recent activity is elusive, other than perhaps an apparent spreading trend and the emergence of a new sunspot group in its neighbourhood.

CME activity in the period (other than the possible aforementioned Common-class flare-related event) was from the far-side, with a large CME visible in imagery from behind the eastern solar horizon. This has a similar longitude to an oncoming active region, which, if not a one-off event, might affect the forecast later this UTC working week.

Solar Wind / Geomagnetic Activity: Solar winds showed an initial slow regime, potentially giving way to a precursor to a fast wind after 07/0500UTC. This change accelerated immediately prior to the period's end, and may be a late report of fast wind conditions, or else perhaps related to the 02 September CME. This will become clearer with time.

The solar wind speed rose slightly from background to become slightly elevated by the period's end. The number of particles in the solar wind was below average at first, but rose to an above average peak. The associated magnetic field saw a similar increase from weak to strong, with the north-south component varying erratically.

The net result of the above solar wind measures was for initially quiet but increasing geomagnetic activity, remaining below Minor Geomagnetic Storm G1 throughout.

Energetic Particles / Solar Radiation: Solar radiation levels showed a continuing decline to resting background following the S1/Minor SEP event on 05 September.

Four-Day Space Weather Forecast Summary

Solar Activity: There is a slight chance of mainly low activity increasing to moderate before midweek UTC, perhaps rising to a chance thereafter due to the expected return of a far-sided active region. No significant departures are due in the period.

Solar Wind / Geomagnetic Activity: The geomagnetic forecast is complex. the only 'coronal hole' fast wind-derived component is due imminently and may result in a peak chance of Minor geomagnetic storm G1 in the first 24 hours. This may see a contribution from a close pass from a minor 02 September CME, with up to three other CMEs then due past Earth from later 08 September. These CMEs give a broad peak chance of Moderate geomagnetic storm G2 straddling these UTC days, with the peak risk centred on the midnight dividing them, but perhaps earlier than previous guidance given revised modelling. Confidence lowers later in the forecast period, with the tail of these CMEs' influence fading. Any new CME in the last 24 hours (discussed above would probably alter the tail of this four-day forecast, with a new coronal hole fast wind then also arriving before the UTC weekend.

Energetic Particles / Solar Radiation: Solar radiation is now near resting background. There is a slightly higher residual risk than is typical for the current cohort of sunspot regions, although the daily risk is still slight.