The United States Space Weather Prediction Center has issued geomagnetic storm watches from today (December 9th) to Friday (December 11th) due to anticipated Coronal Mass Ejections (CMEs) effects.
A CME is a large expulsion of plasma and magnetic field from the Sun's corona. This can result in the sudden release of electromagnetic energy in the form of a solar flare; which typically accompanies the explosive acceleration of plasma away from the Sun
This CME occurred on December 7th.
This will likely cause G1 (Minor) storm levels. The potential for strong storm levels exists and a G3 (Strong) Watch is in effect for December 10th. CME-related disturbances are forecast to continue into 11 December, likely resulting in G2 (Moderate) storm levels.