Science & Technology - Posted by Shemina Davis-Sheffield on Monday, March 8, 2010 13:18 - 0 Comments
Mega-tsunamis stoke up solar atmosphere
U. SHEFFIELD (UK)—Physicists from the University of Sheffield are scheduled to reveal their recent discovery of transition region quakes on the Sun. The finding could shed light on solar mega-tsunamis.
The discovery also may hold the key to understanding the long-standing secret of coronal heating.
The team will deliver their findings to an audience of MPs both from the United Kingdom’s House of Commons and the House of Lords.
The solar transition region is located about 2,000 km above the Sun’s visible surface. It is the narrow layer of sharp transition in density and temperature between the relatively cool solar chromosphere, which reaches temperatures of about 10-20,000 Kelvin, and the very hot upper corona, which sees temperature hit 1-10 Megakelvin.
The way in which the solar corona is heated to temperatures of over a million degrees has so far remained a long-standing puzzle of solar and space physics, especially as this region of the Sun is even further away from the centre of energy production than the underlying solar surface.
Physicists at Sheffield have addressed this enigma by discovering that transition region quakes power the lower base of the solar corona.
The quakes take the form of mega-tsunamis generated by narrow (a few 100 km radius), long (10-40,000 km) rapidly rising (10-100 km/s) plasma jets.
When these jets hit the transition region, they excite a wealth of transition region quakes that have now been observed and modelled for the first time.
The breakthrough has allowed scientists to estimate that at any moment of time there are about 60,000 of these mega-tsunamis splashing and crashing around the transition region.
Colleagues at the Solar Physics and Space Plasma Research Centre (SP2RC) and at the Solar Wave Theory Group (SWAT) devoted many years of research to understand this energy balance and wave processes of the solar atmosphere by using a combined approach of analytical theory, numerical modelling using a supercomputer Iceberg in Sheffield and the UKMHD Cluster in St Andrews, as well as joint satellite observations involving more than one spacecraft simultaneously.
The next step for the team will be to investigate the properties of this torrential sea and focus on the details of transferring the tsunami energy into plasma heat.
“This is indeed a very promising and fantastic result, says Robertus von Fay-Siebenburgen, professor in the Department of Applied Mathematics and head of SP2RC.
“We may now get a step closer to resolve one of the greatest puzzles of astrophysics—why the atmosphere of stars, like the Sun, is so much hotter than its surface.
“A number of international space missions are devoted to studying the heating of the solar atmosphere.
“With the Japanese-lead Hinode satellite on board the high-resolution UK-built EIS camera that we have used in this research, we were very lucky to observe these massive and energetic waves.
“This leap forward will certainly help us reveal the secrets of the Sun.”
University of Sheffield news: www.shef.ac.uk/mediacentre/