[image-51]Sequences of STEREO satellite images of a solar tsunami blasting across the Sun's million degree atmosphere. Solar tsunamis are launched by huge explosions near the Sun's atmosphere, called coronal mass ejections (CMEs). These waves can travel at over a million kilometers per hour. The tsunami took place on 19th May 2007 and lasted for about 35 minutes, reaching peak speeds around 20 minutes after the initial blast. The observations were made by a team from Trinity College, Dublin.
Solar tsunamis were observed before with the SOHO spacecraft, but this is the first time they have been observed in four different wavelengths corresponding to four different temperatures, enabling the team to see how the wave moved through the different layers of the solar atmosphere. This was possible because STEREO observes images at all four wavelengths at a much higher time cadence than SOHO.
The above figure shows a sequence of three 195 A difference images obtained by the EUVI instrument on STEREO taken on May 19, 2007. The images show a tsunami blasting through the Sun's atmosphere at millions of kilometers per hour. The images are "running difference" images in which each image is subtracted from the one following it. This highlights changes.