M5.8 solar flare and multiple CMEs, minor geomagnetic storms expected by December 16

prominence eruption 0636 utc december 14 2023

Solar activity increased to high levels in 24 hours to 12:30 UTC on December 14, 2023, with M5.8 solar flare at 07:44 UTC from Region 3514 and multiple coronal mass ejections (CMEs).

Region 3514 (N05W43, Ekc/Beta-Gamma) — the source of M5.8 and several C-class flares — has experienced substantial spot growth and a rise in magnetic complexity over the past 24 hours. Similarly, Regions 3519 (S12E32, Dao/Beta) and 3520 (N10W41, Dao/Beta) showed growth and activity, with Region 3519 contributing to a few C-class flares. Other regions remained mostly quiet and stable.

At approximately 06:00 UTC today, a nearly 25° long prominence centered near S20W90 erupted from the SW limb. The associated CME, with a southerly trajectory, is expected to precede the Sun-Earth line. Following this event, another CME was observed, likely linked to the M5 flare. Analysis of these events is ongoing.

Late on December 12, dimming near AR 3514 was noted in GOES-16 SUVI 195 imagery, followed by a faint, partial halo Coronal Mass Ejection (CME) with a west-northwest trajectory observed in NASA C2 and C3 coronagraph imagery at the start of December 13. This CME is on a Sun-Earth line trajectory, with an expected arrival around the early hours of December 16.

The greater than 2 MeV electron flux was at normal to moderate levels over the past 24 hours, and the 10 MeV proton flux was at background levels. Moderate levels of >2 MeV electron flux are expected to continue through December 16, with >10 MeV proton flux remaining near background levels unless influenced by today’s M5 flare.

Solar wind parameters reflected a weakly enhanced solar wind regime following the likely glancing influence from a passing transient feature. At approximately 22:00 UTC on December 13, total field increased from 7 nT to ~14 nT, the Bz component saw a southward deflection to -11 nT, and solar wind speeds increased from ~320 km/s to near 390 km/s. Phi was in a predominantly positive orientation.

Weak enhancements are expected periodically through December 16 due to positive polarity CH HSS influence. Additional enhancements are anticipated from weak CME influences.

The geomagnetic field was quiet to active, attributed to a transient feature. Quiet to unsettled levels with isolated active periods are expected on December 14, with G1 – Minor geomagnetic storming likely on December 15 – 16 due to the effects of recent partial halo CMEs.

Solar activity is expected to be at low levels with an increasing chance for an isolated R1 – R2 (Minor – Moderate) event through December 16, due to the anticipated return of active regions from the previous rotation as well as the increased magnetic complexity of Regions 3514, 3519, and 3520.


1 Forecast Discussion – Issued: 2023 Dec 14 1230 UTC – Prepared by the U.S. Dept. of Commerce, NOAA, Space Weather Prediction Center


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