G3 Strong geomagnetic storm levels associated with the passage of slow-moving August 20th Coronal Mass Ejection were observed early August 26, 2018. Could this be the first big sunspot of the next solar cycle, popping up now in the middle of solar minimum?
A faint and slow-moving CME was first seen in LASCO coronagraph imagery on August 20. The source for this CME is unclear, SWPC forecasters said August 21, calling for a glancing blow and negligible impact due to CME's lack of density and slow nature.
G3 Strong geomagnetic storm potential impacts:
Area of impact primarily poleward of 50 degrees Geomagnetic Latitude.
Induced Currents - Power system voltage irregularities possible, false alarms may be triggered on some protection devices.
Spacecraft - Systems may experience surface charging; increased drag on low Earth-orbit satellites and orientation problems may occur.
Navigation - Intermittent satellite navigation (GPS) problems, including loss-of-lock and increased range error may occur.
Radio - HF (high frequency) radio may be intermittent.
Aurora - Aurora may be seen as low as Pennsylvania to Iowa to Oregon in the USA.
The level of disturbance this CME caused just a couple of hours after its arrival is not surprising if you consider the current state of our weakened geomagnetic field.
Credit Image Source at Top of Page:
STAR coronal hole and active region map (solen.info).
SDO (HMIIF, HMIB, AIA211) at 23:45UT on August 25, 2018