Solar activity reached very high levels over the past 36 hours as Region 4366 produced an extensive sequence of strong flares culminating in an X8.1-class eruption at 23:57 UTC on February 1, one of the strongest of Solar Cycle 25 to date.
GOES-18 X-ray flux (1–8 Å channel) recorded continuous elevated emission as the region underwent rapid magnetic expansion on February 1, developing a ‘beta-gamma-delta’ configuration and increasing in area to more than 500 microhemispheres.
Throughout February 1, GOES-18 data registered 17 M-class and two X-class flares from the same region. Notable events included M6.6 at 10:02 UTC, M6.7 at 12:12 UTC, X1.0 at 12:33 UTC, M5.8 at 12:50 UTC, M5.1 at 16:05 UTC, and the X8.1 flare at 23:57 UTC.
After midnight on February 2, the region produced an X2.8 flare at 00:36 UTC, followed by six M-class events (M4.4, M5.2, M1.9, M3.0, M1.6, M2.3) in just 5 hours. An additional X1.6-class flare was recorded at 08:14 UTC on February 2, confirming continued high-level instability within the region.
Two CMEs detected earlier on February 1 at 01:32 and 13:32 UTC in GOES CCOR-1 and SOHO/LASCO C3 imagery originated from the west and southeast limbs and were not Earth-directed. However, SUVI 195 imagery showed post-flare dimming after the X8.1 eruption. A CME was produced, but it appears that most of it is directed away from Earth.
The > 10 MeV proton flux at geosynchronous orbit remained at background levels through most of February 1 but is forecast to briefly exceed S1 – Minor thresholds on February 2, with a continued chance on February 3 as a response to the X8.1 flare. The > 2 MeV electron flux reached high levels (~7 080 pfu) and is expected to remain moderate to high through February 4.
Solar-wind measurements at L1 showed no transient or recurrent disturbances. Speed declined from 400 to 300 km/s and total magnetic field strength (Bt) stayed below 6 nT. Interplanetary magnetic-field polarity remained negative.
The geomagnetic field was quiet, with planetary K-indices of 0 to 2 and predicted Ap ≈ 5 through February 4.
Continued moderate to high solar activity is forecast for the next three days. “Region 4366 is expected to continue producing M-class flares, and another X-class event would not be surprising,” SWPC forecasters said at 01:45 UTC today. “Trends in area and magnetic complexity at this time suggest the threat will linger for at least the next 24 hours, and flare probabilities have been raised through February 4 accordingly.”
Region’s 4366 ‘beta-gamma-delta’ magnetic configuration, its demonstrated ability to produce major-class flares, and the presence of type II radio bursts all support the likelihood of further eruptive activity capable of producing CMEs into the Earth-directed zone this week.