What is a sudden violent explosion on the sun called?

A sudden violent explosion on the Sun is called a solar flare. It is a rapid release of magnetic energy in the Sun’s atmosphere, producing intense electromagnetic radiation across wavelengths from radio waves to X-rays and gamma rays.

Solar flares usually erupt in active regions near sunspots, where tangled magnetic fields can suddenly reconnect. The released energy accelerates charged particles and heats plasma to temperatures above 10 million kelvin. A flare may occur alongside a coronal mass ejection, but the two are different phenomena: a flare is primarily a burst of radiation, while a coronal mass ejection is a vast cloud of solar plasma.

Flares are classified by their soft X-ray strength as A, B, C, M, or X classes, with X-class events the strongest. Their radiation reaches Earth in about eight minutes and can disturb the ionosphere, causing radio blackouts. The term “solar storm” is broader and should not be treated as an exact synonym for solar flare.