EIT observation of a Moreton wave expanding across much of the Sun’s surface. The wave was promulgated by a coronal mass ejection (CME) initiation site on 7 April 1997. This "running difference" imaging technique emphasizes the changes between successive frames. The wave front travels at speeds of about 300 km/s. These images were formed in the emission lines of Fe XII near 195 Å — this ion is formed at temperatures of about 1.5 million degrees.

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