What is the name of a large eruption of plasma from the Sun's corona?

A large eruption of plasma from the Sun’s corona is called a coronal mass ejection, or CME.

A CME releases enormous quantities of magnetized plasma—mostly electrons and protons—from the corona into interplanetary space. These eruptions often begin when twisted or sheared magnetic fields in the corona become unstable and rapidly rearrange. The precise mechanisms that trigger different CMEs can vary and remain an active subject of solar-physics research.

A CME is not the same thing as a solar flare. A flare is an intense burst of electromagnetic radiation produced by magnetic energy release, while a CME is a moving cloud of plasma and magnetic field. The two events frequently occur together, but either can happen without the other. A solar prominence is cooler, denser plasma suspended above the Sun’s surface; an erupting prominence may become part of a CME, but the terms are not interchangeable.

If a CME reaches Earth, it can compress the magnetosphere and trigger a geomagnetic storm. Possible effects include bright auroras, radio disruptions, satellite problems, and stress on electrical grids. Most CMEs, however, are not aimed directly at Earth.