Soho discovers solar tornado

A gyrating high-speed storm wider than Africa projects from the south pole of the Sun, in the lower picture. It is one of a dozen such tornadoes found by the Soho solar spacecraft of ESA and NASA. The CDS scanning spectrometer made the discovery. It 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 km/s. 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 away from Soho, and towards Soho 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. Theorists now wonder what contribution the newly discovered tornadoes make to the solar wind that buffets the Earth's space environment and can harm satellites and power supplies. 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. EIT keeps a daily watch on the Sun's weather at four different ultraviolet wavelengths. The emission that made this image came from gas at 80,000 degrees C, usually occurring fairly low in the Sun's atmosphere except in prominences. Here one prominence (bottom left) has erupted from the Sun. [Image Date: 1998/04] [98.04.017-003]