Sydney University physics undergraduate maps huge plasma tubes in the sky (original) (raw)
By Marcus Strom
Updated June 1, 2015 — 4.49pm
A Sydney University student has for the first time used radio telescopes like a giant pair of electronic eyes to locate huge plasma tubes in the atmosphere that interfere with astronomy observations and which could affect some civilian and military navigation systems.
Scientists have long thought that the interaction of the earth's magnetic field with energy from the sun would create huge tubes of plasma. But they have never been able to directly observe them over large scales or determine their shape. Until now.
University of Sydney astrophysics graduate, Cleo Loi.
While still an undergraduate, Cleo Loi, 23, used the Murchison Wide Field Array in the Western Australia desert in a way that no other radio telescope has been used before.
The wide field array consists of 128 antenna "tiles" over a seven-square-kilometre area. Ms Loi divided the array's tiles into two halves using the western half like a right eye and the eastern half like a left eye. Similar to the way humans use sight, she used triangulation to build a three-dimensional dynamic map of the plasma tubes over a large area.
One of the 128 radio telescope "tiles" at the Murchison Wide Field Array radio telescope in Western Australia.Credit: Pete Wheeler
Ms Loi, who graduated in March, had to overcome the initial scepticism of senior colleagues who thought her observations were too good to be true.
Her undergraduate supervisor, Dr Tara Murphy, said: "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.
"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."
The tubes are in the earth's upper atmosphere, known as the ionosphere, which largely consists of ionised oxygen. The ionosphere is so called because photons from the sun dislodge electrons from otherwise neutral atoms in this layer of the atmosphere, creating a soup or plasma of electronically charged particles. This plasma interacts with the earth's magnetic field, creating field-aligned ducts of the plasma.
The free electrons also interfere with astronomers' observations and can potentially affect satellite navigation systems.
Ms Loi told Fairfax Media that tubes "almost certainly stretch upwards into the plasmasphere", where ionised hydrogen and helium are more prevalent.
"For more than 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 Ms Loi of the ARC Centre of Excellence for All-sky Astrophysics (CAASTRO) at the University of Sydney.
(Above): A gif of Cleo Loi's findings show the plasma tubes (in red and orange) aligning with the Earth's magnetic field.
Understanding the structures of these ducts is important for astronomers using radio telescopes. The weak electromagnetic signals travelling over millions and billions of light years arrive in our solar system and must pass through the atmosphere before they are detected by radio telescopes. Astronomers must take into account the structure of the atmosphere when trying to understand the signals they receive from quasars, radio galaxies, black holes and similar astronomical entities.
"The discovery of the structures is also important because they cause unwanted signal distortions that could affect our civilian and military satellite-based navigation systems. So we need to understand them," Ms Loi said.
Ms Loi was lead author on this research, undertaken as part of her award-winning undergraduate thesis and published in Geophysical Research Letters on Monday.
Ms Loi won the Australian Astronomical Society's 2015 Bok Prize for her research. Ms Loi, who went to James Ruse High School, will move to Cambridge this year to begin her PhD in astrophysics.
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