Solar Tornado
Date: 28 April 1998
Satellite: SOHO
Depicts: Tornado at the Sun's south pole
Copyright: ESA
A gyrating high-speed storm projects like a chimney from the south pole of the Sun in the lower picture. The scanning spectrometer CDS aborad SOHO has imaged this previously unknown type of feature of the Sun's weather in gas at 250 000 degrees C. Measurements reveal flows of around 150 kilometres per second, or 500 000 kilometres per hour. For comparison, tornadoes on the Earth blow at 400-500 kilometres per hour.
The colouring of the image shows, not the intensity of the emission, but the speed of the gas in the tornado. In the lighter right-hand side, the gas is moving towards SOHO, and away from SOHO in the darker left-hand side. The speed measurements come from shifts in the apparent wavelength of an emission from charged oxygen atoms (Doppler effect). The immense size of the tornado is apparent from the comparison with the Earth on the same scale.
The upper picture, used to show the position of the tornado, was obtained on a different date by EIT, SOHO's extreme ultraviolet imaging telescope.