"A very impressive spike in plasma density was noted in solar wind data, along with an impressive strength (Bt) and a Bz component that is swinging wildly between north and south. NOAA/SWPC have already added a moderate (G2) storm watch for the hours ahead and Strong (G3) conditions may also be possible," SolarHam wrote in the update.

A CME is a massive eruption of plasma, or electrically charged gas, and magnetic fields from the Sun's outer atmosphere, called the corona.

Possible impacts on Earth:

Brighter auroras, sometimes visible much farther south than usual.

Disruptions to GPS, radio communications, and satellites.

Stress on electrical grids, potentially causing blackouts during extreme storms.

SpaceWeatherLive reports that a radio blackout is already in progress: