Space Weather Forecast Headline: Large filament lift off observed. Imagery pending. Otherwise, rising probabilities of G1 and R1, with Slight Chance S1 steady, then falling.

Analysis of Space Weather Activity over past 24 hours

Solar Activity: Activity rose to Moderate, with occasional Common-class flares observed, but with a Moderate-class flare greeting the period at 12/0001UTC from over the western solar horizon, most likely from a large off-going sunspot region here. This flare was previously mis-attributed to the eastern solar horizon and an arriving sunspot region here, which produced a near-simultaneous Common-class flare immediately prior to the 24-hour reporting period.

There are now up to six sunspot regions on the Earth-facing side of the Sun. A new region revealed itself on the northeastern solar horizon in the period, however further rotation may yet reveal further detail here. In addition to this arrival, a new magnetically unipolar group emerged in the central northwest of the facing side. Other regions were generally simpler and in decay, although a sunspot group in the far west saw emergence of spots and areal growth by the period's end.

Coronal Mass Ejection (CME) activity was often confined to the northeastern and southwestern horizons in the period (i.e. away from the Sun-Earth line). The large northeastern quadrant 'filament' (arc of plasma) was mobile in the period, and appeared to lift-off slowly to end the reporting period. Satellite imagery is awaited for this event.

Perhaps most notably, a full halo CME signature was observed on imagery starting roughly 12/1000UTC and mainly directed apparently east and south of the Sun-Earth line. This occurred at a nadir in X-ray activity and there is no obvious front-sided source. The event was not obviously visible on other satellite imagery and is considered most likely far-sided, albeit inferred rather than fully ascertained.

No new Earth-directed CMEs were therefore confirmed at the time of writing.

Solar Wind / Geomagnetic Activity: Solar winds were mainly reflective of a gradual exit from a fast wind, however the start of the period saw slightly elevated solar magnetic field and the number of particles comprising the wind, perhaps a hesitant connection to a precursor to another fast wind regime for a time.

The solar wind speed fell from slightly elevated highs to finish within background. The magnetic field was slightly elevated to begin and end the 24 hours, however the north-south component was mainly co-aligned with Earth's field to limit the geomagnetic effect of this behaviour. 

The net result of the above solar wind measures was for mainly quiet geomagnetic indices.

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

Four-Day Space Weather Forecast Summary

Solar Activity: There is a slightly rising eventual chance of Moderate-class flares as a result of returning eastern solar horizon sunspot regions in the period.

Solar Wind / Geomagnetic Activity: The current fast wind should continue to wane, with any additional contributions from other sources becoming less likely towards midweek. This should therefore give a midweek UTC lull, ahead of a possible rise during Day 3 (Thursday 15 May) in a further coronal hole-driven fast wind, as well as a low confidence CME glance from the northwest of the Sun, leaving on 11 May. There is a bookending risk of Minor Geomagnetic Storm G1 in the four days as a result, with intervening quieter activity.

Energetic Particles / Solar Radiation: No solar radiation storms are expected. A large sunspot region's presence just over the western solar horizon and the development of another far western group both give a slightly higher initial daily slight chance of Minor Solar Radiation Storm S1 enhancement, however this will soon fade.