Mostly it is caused by the gases in the solar corona being so hot that, like steam rising from a pot, they simply escape into interplanetary space as a steady wind. High speed flows can be produced when solar storms near the surface magnetically accelerate particles in the inner corona to speeds of a thousand kilometers per second or more. This type of' coronal mass ejection' can happen anytime, but is more frequent when the Sun is near the peak of its sunspot cycle of activity.
All answers are provided by Dr. Sten Odenwald (Raytheon STX)
NASA IMAGE/POETRY Education and Public Outreach program.