Elusive magnetospheric plasma tubes finally recorded

After 60 years of research, astronomers have finally observed structures of plasma – one of the four fundamental states of matter – in the magnetosphere.

Scientists at the University of Sydney in Australia used a radio telescope and located tubular plasma structures aligned along the Earth's magnetic field.

Research leader, Cleo Loi said: “For over 60 years, scientists believed these structures existed but by imaging them for the first time, we've provided visual evidence that they are really there”.

In the study, published in Geophysical Research Letters, the team used the radio telescope Murchison Wide Field Array (MWA) located in Western Australia to map large patches of the plasma structures. The rapid snapshot capabilities of the telescope allowed the team to create a film capturing the real-time motions of the plasma. By adjusting the telescope they managed to view the motions in 3D.

“This is like turning the telescope into a pair of eyes, and by that we were able to probe the 3D nature of these structures and watch them move around. We saw a striking pattern in the sky where stripes of high-density plasma neatly alternated with stripes of low-density plasma. This pattern drifted slowly and aligned beautifully with the Earth's magnetic field lines, like aurorae,” Loi said.

The scientists estimated the position of plasma tubes to extend from the ionosphere – about 600 km above Earth’s surface – up to the plasmasphere where the neutral atmosphere ends, and a transition zone to the plasma of outer space begins. They also studied the organisation of these structures and discovered that they are organised and regularly spaced.

“We were able to measure the spacing between them, their height above the ground and their steep inclination. This has never been possible before and is a very exciting new technique,” added Loi.

The scientists believe that the plasma structures can cause unwanted signal distortions that could affect civilian and military satellite-based navigation systems.

Paper: http://onlinelibrary.wiley.com/doi/10.1002/2015GL063699/full

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