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Archive Trawl Gives Bison Three Decades Of Solar Music

March 30, 2005

Scientists in Birmingham have scoured the archives and put together a complete archive of helioseismic data for nearly three solar cycles. The results from reprocessing the data will shed light on the link between helioseismology, the study of sound waves resonating within the Sun, and solar activity. Dr Graham Verner will be presenting preliminary findings at the RAS National Astronomy Meeting at the University of Birmingham on Tuesday 5th April.

The Sun is a like a vast bell that is being struck continuously by tiny grains of sand and is ringing away. Acoustic waves, generated in the outermost layers of the Sun's interior, bounce off the surface and then are refracted up again repeatedly and can create standing waves. The internal waves, which typically have an oscillatory period of five minutes, can be studied by measuring the Doppler shift of ripples that they cause on the Sun's surface. Some of the sound waves penetrate into the deep interior of the Sun, so they give scientists an opportunity to study these core regions where the nuclear reactions occur that power the Sun and also drive its evolution.

The Birmingham Solar Oscillations Network (BiSON) group has been collecting helioseismic data since 1976. Initially the group had only one station and only operated in the summer. As more stations were added, the quality of the data and the time-coverage improved, and in 1979 the group first observed the now familiar 5-minute oscillations. In the early 1990s a full 6-station network, now known as BiSON, was established, providing high quality and low noise data. Other groups have collected helioseismic data for one full 1-year solar cycle but the BiSON archive is the only one that extends back through three cycles.

There are millions of oscillation modes for standing waves inside the Sun. BiSON did pioneering work in the early 1990s on identifying the relationship between mode frequencies and solar activity. Now, with 29 years of data, they hope to look for changes between successive solar cycles and any long period trends. The results from this new analysis of old data should be published in the next few months.

Royal Astronomical Society (RAS)