Space Weather Forecast Headline: Falling chance of Minor Geomagnetic Storm G1 into new UTC week. Minor Radio Blackouts R1 likely.

Analysis of Space Weather Activity over past 24 hours

Solar Activity: Activity remained Moderate, with occasional low-level Moderate-class flares observed, peaking at 26/0035UTC from a sunspot region in the eastern solar hemisphere.

There are now seven sunspot regions on the facing side of the Sun, with two no longer visible over and near the northwestern solar horizon respectively. The main changes observed in the period included a spreading trend in the largest region in the central part of the Sun, with slight areal decay and opening out of its trailing spots, compensated for by new emergence and growth near its centre. There was also emergence and strong areal growth in a second sunspot region in the northeast, with its main trailing spot increasing in size, with the group as a whole spreading longitudinally. A third group showed some intermediate and trailing spot emergence to give a congested appearance of mainly small spots, although the narrow viewing angle to this region is likely to be hiding some additional detail. Other regions were either small and stable or else in decay.

A large 'filament' (arc of plasma) lifted off the southwest around 25/2000UTC. This was subsequently visible in satellite imagery, however no triangulating imagery is available as of the time of writing. Analysis is ongoing. With this event possibly excepted, no new Coronal Mass Ejections (CMEs) are thought to impinge on the Sun-Earth line.

Solar Wind / Geomagnetic Activity: The solar wind speed showed a slow wind give way to a fast wind, the fast wind likely emanating from one of a pair of 'coronal holes' lying in the western solar hemisphere.

The solar wind speed was initially at background. This was replaced by a rising trend from around 25/1900UTC, with this continuing to reach a late-period slightly elevated peak. The number of particles comprising the solar wind was mostly at background, however there was a rise between 25/1600 and 1900UTC to slightly elevated levels, perhaps related to a precursor to the fast wind.

The magnitude of the magnetic field in the solar wind showed a similar discontinuity, being at background until the fast wind onset, whereupon the trace became slightly elevated. The north-south component was variable - spending no protracted periods of time either aligned or anti-aligned with Earth's field.

The net result of the above solar wind measures was provisionally mainly quiet activity, below Minor Geomagnetic Storm G1 throughout.

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

Four-Day Space Weather Forecast Summary

Solar Activity: Moderate solar activity is likely to continue at first, with occasional Moderate‑class flares and a slight chance of isolated X‑class flares. This flare risk expected to decrease slightly through the period. 

Solar Wind / Geomagnetic Activity: Several weak CMEs may arrive at Earth, most likely on Day 1 (26 April) as a possible glancing blow, or else associated with the shock from larger CMEs off the northwest of the Sun. 

Solar winds are likely to peak through Day 1 (26 Apr) before slowly declining Day 2 (27 April) onwards. Geomagnetic activity due to the fast winds is likely to be fairly muted due to unfavourable polarity of the coronal holes for this time of year. However, this evolution is likely to be complicated by potential glancing CME influences through the period. 

There is a chance of G1/Minor Storms on Day 1 due to coronal hole fast winds and any glancing CME impacts. Through Day 2 into Day 3 (27-28 April) geomagnetic activity is expected to become quieter, although there is lower than normal confidence given a spate of minor peripheral CMEs and gaps in available imagery to assess them. 

Energetic Particles / Solar Radiation: There is a daily slight chance of Minor S1 solar radiation storms. The recent significant x-ray flares produced by a large off-going sunspot region have so far had negligible impact, and the risk from this region is now reducing. This daily slight chance is however maintained roughly level by a succeeding large front-sided active region following on its heels into the western solar hemisphere.