Data from the ESA/NASA spacecraft SOHO shows clearly that powerful starquakes ripple around the Sun in the wake of mighty solar flares that explode above its surface. The observations give solar physicists new insight into a long-running solar mystery and may even provide a way of studying other stars.
The outermost quarter of the Suns interior is a constantly churning maelstrom of hot gas. Turbulence in this region causes ripples that criss-cross the solar surface, making it heave up and down in a patchwork pattern of peaks and troughs.
The joint ESA-NASA Solar and Heliospheric Observatory (SOHO) has proved to be an exceptional spacecraft for studying this phenomenon. Discovering how the ripples move around the Sun has provided valuable information about the Suns interior conditions. A class of oscillations called the 5-minute oscillations with a frequency of around 3 millihertz have proven particularly useful.
According to conventional thinking, the 5-minute oscillations can be thought of as the sound you would get from a bell sitting in the middle of the desert and constantly being touched by random sand grains, blown on the wind. But what Christoffer Karoff and Hans Kjeldsen, both at the University of Aarhus, Denmark, saw in the data, was very different.
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, Karoff says.
So they began looking for the culprit and discovered an unexpected correlation with solar flares. It seemed that when the number of solar flares went up, so did the strength of the 5-minute oscillations.
The strength of the correlation was so strong that there can be no doubt about it, says Karoff.
A similar phenomenon is known on Earth in the aftermath of large earthquakes. For example, after the 2004 Sumatra-Andaman Earthquake, the whole Earth ran
|Contact: Bernhard Fleck|
European Space Agency