Moreton wave

A Moreton wave is a shock wave on the Sun's chromosphere that is produced by a large solar flare and expands outward at about 1,000 km/s. It usually appears as a slowly moving diffuse arc of brightening in H-alpha, and may travel for several hundred thousand km. Moreton waves are always accompanied by meter-wave radio bursts; they are named after the American solar astronomer Gail Moreton.