A semicircular shock wave in the Sun’s chromosphere moving outwards from the site of a large solar flare at a velocity of about 1000 km/s; they are also known as flare waves. Moreton waves can cause the winking of dark filaments in their path and the oscillation of coronal loops. Metre-wave radio bursts invariably accompany Moreton waves. They are named after the American solar astronomer Gail Ernest Moreton (1930–82).