A Moreton wave is the chromospheric signature of a large-scale solar coronal shock wave . Described as a kind of solar "tsunami", they are generated by solar flares. They are named for American astronomer Gail Moreton, who first reported their existence as found in observations by Harry Ramsey. Moreton waves propagate at a speed of 500-1500 km/s, and occur where a coronal MHD fast-mode weak shock wave intersects the chromosphere according to a well-known theory of Yutaka Uchida that links them to radio type II bursts. Moreton waves can be observed primarily in the Hα band.