Signs of life from the sun

2026-04-17 0530z

New active regions, increasing flare risk, large coronal hole brings fast solar wind and perhaps mid-latitude aurora

Synoptics

Active regions

• Region 4416 remained quiet and simply built
• Region 4415/4418 triggered a filament eruption to the southeast and an expansion of the large coronal hole
• Region 4419 emerged just behind the eastern limb and developed quickly, whether it will develop further towards more complexity with an increased risk of stronger flares and coronal mass ejections remains to be seen – the potential is there

Coronal holes

• Coronal hole CH41+ in the south could increase the solar wind speed in the short term with a low probability
• Coronal hole CH42- has recently increased significantly in size, especially in the south – its fast solar wind could reach us increasingly in stages from 18.4., the stream interaction region already on 17.4. The polarity is favourable for the time of year, mid-latitude polar light cannot be ruled out

Filaments

• The last numerous filaments are no longer visible in the H-alpha spectrum, some of them have erupted, some of them have become inactive, some of them have disintegrated

Low sunspot number, low X-ray flux

• Only three active regions are visible, so the number of sunspots is correspondingly low at around 50, and the radio flux is also quite low at around 100
• The X-ray flux (flares) is stable in the low B-class range, recently with a few C-class flares from region 4419, overall the level seems to be increasing – perhaps region 4419 will manage to produce M-class flares

Large-scale reconfiguration and filament eruptions

• Lots of movement in the corona, especially in the south and north-east, also at the edges and on the far side
• A very large filament eruption starting at region 4415 travelled across the entire south-eastern half of the sun and led to changes in the position and size of the surrounding coronal holes

Three days of corona, coronal loops, sunspots, magnetic field – different layers from the SDO satellite (Courtesy of NASA and the SDO AIA, HMI, EVE Science Teams)

One of many filament eruptions of the last days, here in the north-west – backside. A fast coronal mass ejection (CME) was produced (not earth-directed).

Travelling coronal hole & CME

Changes in the photospheric magnetic fields led to a large filament eruption, in the context of which corona material was evacuated from the vicinity of the coronal hole CH42-, which ultimately led to an enlargement of the coronal hole. The Earth-facing area is now significantly larger and we can expect a correspondingly faster solar wind and higher geoeffectiveness.

Coronal mass ejections (CMEs) in all directions, interesting for us the CME to the southeast in connection with the large filament eruption and the coronal hole expansion – it is slow and will probably miss us, but the possibility of a glancing blow exists for 18 April/ 19 April, if it manages to arrive in time together with the stream interaction region of CH42-.

Another CME, this time with an Earth-facing halo, can be seen in SOHO LASCO C2 – likely a result of the dimming/moving coronal hole or a flare from region 4418. A weak impact on 18 April, or more likely 19 April – together with the stream interaction region, noticeable effects could occur.

☞ kauai.ccmc.gsfc.nasa.gov/DONKI/view/CME/45707/1

As always, everything is very uncertain: Arrival of the stream from CH41+, arrival of the stream interaction region from CH42–, arrival and strength of the fast solar wind from CH42–, mixing/amplification with CMEs – SWPC issues a G2 watch for 17 Apr and 18 Apr (chance of G2 MODERATE STORM), Met Office UK sees a slight chance of G3 on 19 Apr if CME effects are noticeable.

Whether it will be enough for auroras in Central Europe is uncertain. Nevertheless, I have set the “Aurora Watch” flag for this article, as so much coronal activity before the arrival of a high-speed stream has often led to stronger geomagnetic activity.

Region 4419 in the north-east grows and new region behind the north-east limb

The astonishing development of region 4419, at the end not yet particularly complex but with many sunspots and quite large – interacting with the neighbouring coronal hole while swinging a filament whip. Lots of movement in the corona – let’s see how it continues. The location close to the coronal hole harbours potential for significant developments.

Something is moving behind the north-eastern limb. These are old regions that we have already seen during the last rotation. They seem to be regenerating with new ‘flux emergence’ (rise of plasma/magnetic field).

Solar Orbiter is currently on the far side of the sun and shows a broad strip of active regions in the north, although the sunspots have largely submerged again – but some regions appear to be reactivating. We will see.

More updates always on X or bluesky

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