A G1 – Minor Geomagnetic Storm Watch has been issued by the SWPC for September 14, superseding all previously active watches but limited to September 14.
Potential impacts from the expected geomagnetic activity are minor and generally confined to areas poleward of 60° geomagnetic latitude.
Weak power grid fluctuations may occur in these regions, and satellite operations could experience isolated disruptions. Aurora displays may become visible at high latitudes, particularly across the northern tier of the United States, including areas of northern Michigan and Maine.
According to the latest SWPC forecast discussion, the expected activity is primarily linked to enhancements in the solar wind environment associated with corotating interaction region (CIR) effects and the arrival of a negative polarity coronal hole high-speed stream (CH HSS).
In addition, a coronal mass ejection (CME) observed on September 11 may produce a weak glancing influence late on September 14 through early September 15.
Solar activity was at low levels over the past 24 hours, with a few low C-class flares recorded. Active Region 4213 (beta) showed minor development in its intermediate spot area as it approached the western limb, while AR 4216 (beta) added a small trailing spot after rotating further into view from the east limb.
Other regions on the visible disk remained stable.
At 01:40 UTC on September 13, a filament approximately 13° long, centered near S24E13, lifted off the disk. Imagery suggested most of the material was reabsorbed, as no associated CME was confirmed.
Solar activity is expected to remain at low levels through September 15, with only a slight chance for an isolated M-class flare.
The greater than 2 MeV electron flux briefly exceeded 1 000 pfu over the past 24 hours but did not reach high-level alert thresholds. The >10 MeV proton flux remained at background levels.
Forecasts indicate the >2 MeV electron flux will likely reach high levels on September 13–14 in response to elevated geomagnetic activity before returning to normal to moderate levels on September 15. The >10 MeV proton flux is expected to remain at background levels throughout.
Solar wind conditions over the past 24 hours reflected nominal background values. The total interplanetary magnetic field (IMF) ranged from 6 to 8 nT, with the Bz component fluctuating between ±5 nT and remaining mostly southward after 00:00 UTC on September 13.
Solar wind speeds decreased gradually from 400 km/s to near 350 km/s, while the phi angle remained in a positive orientation.
The geomagnetic field was quiet to unsettled during the past 24 hours.