The Sun has tall gyrating storms far larger and faster than tornadoes on theEarth. This unexpected finding is among the latest results from the solarspacecraft SOHO, announced at a European Space Agency press briefing on 28 April. British scientists discovered the solar tornadoes in images anddata from SOHO's scanning spectrometer CDS. So far they have detected adozen such events. They occur most frequently near the north and south polesof the Sun and are almost as wide as the Earth.
Steady windspeeds of 15 kilometres per second and gusts ten times faster(which means 500,000 kilometres per hour) occur in the solar tornadoes. Forcomparison, tornadoes on the Earth blow at 400-500 kilometres per hour. Thesolar measurements are made by the Doppler effect -- the same principle asthat used by police radars to detect speeding motorists. The observedwavelength of emission from hot oxygen atoms changes according to whetherthe gas is moving towards the detector or away from it, and the CDSinstrument is very sensitive to these variations.
One of SOHO's main tasks is to trace the sources of the wind from the Sunthat pervades the Solar System. Gusts and shocks in the solar wind buffetthe Earth's environment, causing auroras and magnetic storms and endangeringsatellites and power supplies. The newly discovered tornadoes may contributeto the solar wind, especially to a fast windstream that emanates fromrelatively cool parts of the solar atmosphere called coronal holes.
"We see the hot gas in the tornadoes spiralling away from the Sun andgathering speed," says David Pike of the Rutherford Appleton Laboratory, UK,who is co-discoverer of the solar tornadoes with Helen Mason of CambridgeUniversity. "These spectacular events in the Sun's atmosphere must havewidespread effects. Our next step will be to try to relate the solartornadoes to observations of the fast solar wind farther out in space, asseen by other instruments in SOHO."
Built in Europe for the European Space Agency, SOHO carries twelve sets ofinstruments provided by European and American investigators, and it wasdispatched into space on 2 December 1995 by a NASA launcher. SOHO is aproject of international cooperation between ESA and NASA.
Materials provided by European Space Agency. Note: Content may be edited for style and length.
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