| Danish physicists find solar flares produce starquakes |
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| by William Atkins | |
| Friday, 25 April 2008 | |
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These physicists have been using data accumulated for ten years from the SOHO spacecraft, specifically from the VIRGO instrument, to observe and analyze five-minute oscillations on the Sun with a frequency of about 3 millihertz (mHz). These oscillations are found in a very turbulent region of the Sun, its outer interior. They ripple globally around the entire surface of the Sun whenever large solar flares occur. The two physicists—Christoffer Karoff and Hans Kjeldsen (both from the University of Aarhus, Denmark)—discovered the relationship: the strength of these 5-minute oscillations increased as the number of solar flares increased. The oscillations, they say, would be similar to what happens when a hammer hits a bell, it vibrates. In fact, Karoff stated, "The signal we saw was like someone occasionally walking up to the bell and striking it, which told us that there was something missing from our understanding of how the sun works.” (Associated Press: “Solar flares cause 'starquakes' on the sun”] Karoff added, "What we have seen is [something] that every once in a while comes up and knocks the bell with a hammer so it rings [loudly] for a short while. The flares are the hammer." [Cosmos: “Solar flares leave Sun quaking”] Plus, he said, "The strength of the correlation was so strong that there can be no doubt about it.” [Space Daily: “Solar Flares Set The Sun Quaking”] The physicists state the when earthquakes occur on our planet, seismic waves result, similar to the 5-minute oscillations and starquakes (or “sunquakes”) on the Sun. Both earthquakes and sunquakes ring like a vibrating bell to produce these oscillations (seismic waves). However, a sunquake is much larger than an earthquake. Karoff estimates that a typical sunquake could be equivalent to an 11.3 ranking on the Richter scale, which measures earthquakes here on Earth. Such a level has never been attained before on Earth (to our knowledge). They compared an average sunquake to the earthquake that leveled San Francisco, California in 1906: an average sunquake releases forty times the amount of energy as the huge San Francisco (Richter scale: 7.7 to 8.3). The largest recorded earthquake (since 1900) is considered the Great Chilean Earthquake on May 22, 1960, a magnitude of 9.5. The study by Karoff and Kjeldsen is to appear in the May 1, 2008 issue of the Astrophysical Journal Letters. Why is their research important to us on Earth? Please read on. |
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