Student Confirms That There Are Enormous Tubes Of Plasma Floating Above The Earth
June 3, 2015 | by Stephen Luntz
This is an artist's impression of tubular plasma structures in the Earth's magnetosphere, 600 kilometres above the ground. Credit: CAASTRO/Mats Bjorkland
(photo credit source : http://www.sciencedaily.com/
A 60-year-old theory about the structure of the magnetic fields that surround Earth has been confirmed directly for the first time. The lead author of the paper is an undergraduate student who invented a way to view the Earth's magnetosphere in three dimensions.
The sun emits a constant stream of charged particles that's supplemented by cosmic rays from sources such as supernovae. As these particles approach Earth, their path is altered by the Earth's magnetic field, which deflects some and funnels others towards the poles, leading to displays such as aurora.
This region, known as the magnetosphere, includes the ionosphere and plasmasphere as its inner layers. These distinctions aside, we don't know all that much about the structure of these regions.
A better understanding would be useful because the ionosphere interferes with satellite navigation systems and the images received by radio telescopes. During her honors project at the University of Sydney, Cleo Loi realized she could use the Murchison Widefield Array (MWA) radio telescope to probe these regions in a way that had never been done before, leading to a paper in the journal Geophysical Research Letters.
The MWA is a forerunner of the Square Kilometer Array (SKA), soon to transform radio astronomy. It consists of 128 antennae spread over three kilometers (almost two miles). Loi suggested that by splitting the observations between those from the eastern and western ends of the array, she would achieve something equivalent to binocular vision, allowing us to see in three dimensions.
For the MWA's usual astronomical work, a three-kilometer baseline does not give the parallax required to see in-depth, but the situation is very different when we are looking close to the Earth.
Loi detected a series of high and low density plasma tubes connecting the ionosphere and plasmasphere running in parallel to the magnetic field. "We measured their position to be about 600 kilometres [373 miles] 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," Loi said. The tubes move slowly with time, so telescopes experience changing interference effects.
Loi told IFLScience that while some limited probing has been done on the ionosphere with other radio telescopes such as the Very Large Array, no one to her knowledge has applied parallax to the problem previously.
“People theorized something like this from observations of a type of very low frequency electromagnetic wave. We can detect lightning from another hemisphere and people concluded there must be plasma tubes guiding the signal,” says Loi. “It's a very indirect conclusion, and no one had much idea what these tubes were like.”
Loi says she was amazed at how many tubes the MWA's enormous 30° field revealed. “There are no plans to use the SKA for studying the ionosphere, but I am hoping with publicity about this work to change that,” she says.
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Source : http://www.sciencedaily.com/
Seeing tubular plasma structures in inner layers of magnetosphere surrounding Earth
Date: June 1, 2015 Source: University of Sydney
Summary:
Astronomers have creatively used a radio telescope to see in 3-D, allowing them to detect the existence of tubular plasma structures in the inner layers of the magnetosphere surrounding the Earth. By creatively using a radio telescope to see in 3D, astronomers have detected the existence of tubular plasma structures in the inner layers of the magnetosphere surrounding 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 in Australia.
Ms Loi is the lead author on this research, undertaken as part of her award-winning undergraduate thesis and recently published in Geophysical Research Letters. In collaboration with international colleagues, she identified the structures.
"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," Ms Loi said.
The region of space around 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 revealed, 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," explained Ms Loi.
Using the Murchison Widefield Array (MWA), a radio telescope located in the Western Australian desert, Ms 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," Ms 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."
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.
"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," said Ms Loi.
"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."
This ability adds yet another accolade to the MWA's name after it had already proven its worth as a powerful precursor instrument to the Square Kilometre Array (SKA), and now the MWA's 3D vision has the potential to provide many more in-depth analyses of the formation of plasma structures.
"It is to Cleo's great credit that she not only discovered this but also convinced the rest of the scientific community. As an undergraduate student with no prior background in this, that is an impressive achievement," said Ms Loi's supervisor Dr Tara Murphy, also of CAASTRO and School of Physics at the University of Sydney.
"When they first saw the data, many of her senior collaborators thought the results were literally 'too good to be true' and that the observation process had somehow corrupted the findings, but over the next few months, Cleo managed to convince them that they were both real and scientifically interesting."
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