October 30, 2013

Swiss Supercomputer Solves Core Mystery

Tiffany Trader

A team of scientists from ETH Zurich and the University of Leeds have solved a 300-year-old riddle about the nature of the Earth’s rotation. Using the Cray XE6 supercomputer “Monte Rosa” installed at CSCS, the researchers uncovered the reason for the gradual westward movement of the Earth’s magnetic field.

For three centuries, scientists have known about this westward-drift, but they did not fully understand the dynamics involved. Now, thanks to Monte Rosa’s advanced computing power and a sophisticated computer model, they have their answer.

First it’s necessary to explain that the Earth’s magnetic field is no mere artifact. The field acts as a shield, protecting the planet from harmful radiation. It’s also a navigation system for flying animals like birds and bats. The field is the result of geodynamo processes in both the liquid outer core and in the solid inner core.

Using advanced computer simulations, head researcher Philip Livermore from the University of Leeds along with Rainer Hollerbach and Andrew Jackson from ETH Zurich discovered that the magnetic field also influences the dynamic processes that are taking place in the Earth’s core.

The Earth’s inner core, which is made up of solid iron and roughly the same size as the moon, ‘superrotates’ in an eastward direction. The inner core spins faster than the rest of the planet, while the outer core and the magnetic field are essentially pushed westward.

This principle was first revealed in 1692 by the natural scientist Edmund Halley of Halley’s comet fame, but could not be explained up to now.

From the supercomputer simulations, it is apparent that the force of the Earth’s magnetic field in the outermost edges of the liquid core is driving the magnetic field westwards. At the same time, these forces push the solid inner core the opposite direction (aka east). As a result, the Earth’s inner core rates faster than the Earth.

This is the first time that scientists have been able to draw a direct connection to the spin of the outer and inner cores.

“The link is simply explained in terms of equal and opposite action,” remarks Dr. Livermore of the School of Earth and Environment at the University of Leeds. “The magnetic field pushes eastwards on the inner core, causing it to spin faster than the Earth, but it also pushes in the opposite direction in the liquid outer core, which creates a westward motion.”

The project relied on the supercomputing power of Monte Rosa, a resource of the Swiss National Supercomputing Center in Lugano, Switzerland. With this advanced computational ability and improved software, the science team was able to simulate the Earth’s core with an accuracy about 100 times better than other models.

writeup of the research at the Swiss HPC Service Provider Community website hpc-ch.org, asserts that numerical models of the Earth’s magnetic field are among the most compute-intensive simulations in high performance computing. Solving equations governing fluid dynamics involves both classical mechanics and thermodynamics. The article notes that “together with seismic measurements, such simulations are the only tool for researching the Earth’s interior from depths of 2,900 kilometres all the way to the Earth’s centre at a depth of 6,378 kilometres.” It’s only been in recent years, that modeling and simulation has advanced to the point where these kinds of deep discoveries of the Earth’s interior have been possible.

The full study, “Electromagnetically driven westward drift and inner-core superrotation in Earth’s core,” is available in Proceedings of the National Academy of Sciences.

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