CME impacts Earth sparking widespread aurora, G3 – Strong storm Watch in effect for April 16
A coronal mass ejection produced by a filament eruption on April 13 impacted Earth’s magnetic field at 16:37 UTC on April 15, sparking a G2 – Moderate geomagnetic storm. A G3 – Strong geomagnetic storm watch is in effect for April 16 due to the anticipated arrival of additional CMEs.
Aurora borealis and STEVE by Kristian Eli Eli Zachariasen on April 15, 2025, at Faroe Islands, Denmark (via SpaceWeather)
A series of coronal mass ejections (CMEs) produced on April 13 have begun impacting Earth, with the initial CME hitting at 16:37 UTC on April 15 and producing G2 – Moderate geomagnetic storming.
The Space Weather Prediction Center (SWPC) has issued a Watch for a G3 – Strong geomagnetic storm on April 16 due to the anticipated arrival of additional CMEs.
Solar activity remained at moderate levels in 24 hours to 00:30 UTC today, due to multiple M-class solar flares. Two concurrent flares made precise source identification challenging, with simultaneous activity recorded on both the eastern and western solar limbs. The western limb event, linked to departing active Region 4055, was identified as an M1.3 flare peaking at 18:13 UTC on April 15.
A CME observed around 15:00 UTC on April 15, originating from beyond the Sun’s eastern limb, is not expected to impact Earth.
SWPC forecasts a reduction in M-class flare probability from 75% to 50% through April 18, as Region 4055 moves beyond Earth’s line of sight. Currently, all visible solar regions exhibit relatively simple magnetic configurations, keeping the chance of X-class (Strong) flares very low, at approximately 5%.
The high-speed solar wind stream (HSS) from a negative-polarity coronal hole (CH) in the southern solar hemisphere continued to influence Earth over the past several days. Electron flux levels greater than 2 MeV remained elevated over the past 36 hours, with peak measurements of 2 380 pfu detected by GOES-19 at 16:20 UTC and 5 120 pfu by GOES-18 at 17:50 UTC on April 15. Proton fluxes greater than 10 MeV remained at background levels.
SWPC expects continued high electron flux through April 18, reinforced by interactions with an additional northern CH stream expected on April 17. Proton flux is anticipated to remain at background unless significant flare activity occurs from Region 4055, which will remain in a favorable position through April 16.
Solar wind conditions intensified following CME arrival at 16:37 UTC on April 15. The interplanetary magnetic field (IMF) reached a peak strength (Bt) of 28.2 nT by 18:20 UTC, with the southward magnetic component (Bz) dropping sharply to -20.3 nT at 18:15 UTC.
Solar wind speed increased from pre-impact levels near 400 km/s to approximately 554 km/s. SWPC recorded variability in the phi angle, indicating fluctuating magnetic orientations embedded within the solar wind flow.
Solar wind parameters are forecast to remain elevated throughout April 16 due to ongoing CME impacts. Conditions will gradually subside on April 17, though effects from an approaching equatorial negative-polarity CH are expected to maintain elevated solar wind levels.
Earth’s geomagnetic field transitioned from quiet to unsettled conditions into G1 – Minor storm levels following CME impact, intensifying further into G2 – Moderate storm levels by the evening of April 15.
SWPC forecasts continued geomagnetic storming on April 16, with conditions expected to increase to G3 – Strong storm levels as multiple CME arrivals interact with Earth’s magnetosphere.
Storm conditions will diminish to G1 – Minor levels by April 17, with lingering active to unsettled geomagnetic activity expected thereafter.
References:
1 Forecast Discussion – SWPC – Issued at 00:30 UTC on April 16, 2025
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