Earth's writhing magnetic field could aid fusion research

Null points for ESA's Cluster

By Lucy Sherriff • Get more from this author

Posted in Physics, 19th July 2006 10:42 GMT

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The European satellite constellation Cluster has reported a first - it has seen a region of the Earth's magnetic field spontaneously reconfiguring itself. As well as breaking new scientific ground, the findings could have a practical application for scientists working on new ways of generating energy.

In space, magnetic field are violent turbulent things - a world away from a familiar bar magnet. Different regions of magnetism behave something like large, plasma containing bubbles, ESA explains. When the bubbles are pushed together, the field lines can deform, then break and reconnect, forming a new, more stable arrangement.

The exact point of the reconnection is called the "null point", and until now, scientists have never been able to observe one.

The actual event happened way back in September 2001 somewhere in the Earth's magnetotail on the night-side of the planet. But the data take so long to process, it is only now that scientists can say with any confidence that they have hit the bullseye and found a null point.

The analysis, led by Dr Xiao from Chinese Academy of Sciences, revealed that the null point existed in a vortex structure about 500km across.

This was totally unexpected, as no previous observations or computer simulations have predicted the null point to have this size or configuration.

This process - magnetic reconnection - is thought to be behind some spectacular phenomena, such as the jets of material ejected from the poles of black holes, the solar flares our own sun produces, and even some of the aurorae in our atmosphere.

But this isn't all about pretty pictures: understanding the process could help researchers developing nuclear fusion technology. The magnetic reconnection events are known to make nuclear fusion rather unpredictable. Better understanding the processes could lead to better reactor design.

Earlier this year, Cluster researchers discovered that space is fizzing. Thousands of bubbles of superheated gas are created at the boundary between Earth's magnetic field and the solar wind, a constant stream of gas from the sun.

Initially the scientists though the bubbles, also known as density holes, were glitches in the instrumentation. "Inside" a bubble, the density of the gas drops by ten times, but the temperature soars from 100,000 degrees to 10,000,000 degrees.

Exactly how the bubbles are formed is not known, but the scientists suspect the shock wave where the solar wind hits our magnetic shield is creating the energy to drive them. ®

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