Bottom line: Coronal mass ejections – also knowns as CMEs – are powerful eruptions on the sun's surface. Caused by instabilities in the sun's magnetic field, they can launch a billion tons of superheated gas into space. Most drift harmlessly across the solar system, but occasionally one is aimed at Earth.

What causes solar flares and coronal mass ejections?

According to NASA, a solar flare is an intense burst of radiation that comes from the release of magnetic energy linked with the sunspots. Coronal mass ejections or CMEs are massive clouds of particles that are pushed out into space from the Sun's atmosphere.

How often does a coronal mass ejection occur?

The frequency of CMEs varies with the 11 year solar cycle. At solar minimum we observe about one a week. Near solar maximum we observe an average of two to three CMEs per day. CMEs disrupt the flow of the solar wind and cause disturbances that can damage systems in near-Earth and on Earth's surface.