Scientists have found the first visual evidence that the Earth is surrounded by strangely shaped plasma structures, including plasma tubes.
Researchers using a radio telescope to see in 3D detected the existence of tubular plasma structures in the inner layers of the magnetosphere surrounding the Earth.
"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," said Cleo Loi of the ARC Centre of Excellence for All-sky Astrophysics (CAASTRO) and School of Physics at the University of Sydney.
"The discovery of the structures is important because they cause unwanted signal distortions that could, as one example, affect our civilian and military satellite-based navigation systems. So we need to understand them," said Loi, lead author on the research published in the journal Geophysical Research Letters.
The region of space around the Earth occupied by its magnetic field, called the magnetosphere, is filled with plasma that is created by the atmosphere being ionised by sunlight.
The innermost layer of the magnetosphere is the ionosphere, and above that is the plasmasphere. They are embedded with a variety of strangely shaped plasma structures including, as has now been shown, the tubes.
"We measured their position to be about 600 kilometres above the ground, in the upper ionosphere, and they appear to be continuing upwards into the plasmasphere. This is around where the neutral atmosphere ends, and we are transitioning to the plasma of outer space," said Loi.
Using the Murchison Widefield Array (MWA), a radio telescope located in the Western Australian desert, Loi found that she could map large patches of the sky and even exploit the MWA's rapid snapshot capabilities to create a movie - effectively capturing the real-time motions of the plasma.
"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.
"We realised we may be onto something big and things got even better when we invented a new way of using the MWA," she said.
The MWA consists of 128 antenna 'tiles' spread over an area roughly three by three kilometres that work together as one instrument - but by separating the signals from tiles in the east from the ones in the west, the astronomers gave the MWA the power to see in 3D.
"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," Loi said.
