An Australian Student, Cleo Loi, creatively using a radio telescope to see in 3D, astronomers detecting 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) at the University of Sydney.
Ms Loi is the lead author on this research, undertaken as part of her award-winning undergraduate thesis which was published in Geophysical Research Letters today. She identified the structures using the Murchison Widefield Array, which is a radio telescope in the Western Australian desert. Loi found that by using the array’s rapid snapshot capabilities to create a movie – effectively capturing the real-time movements of the plasma – to map large patches of the sky.
“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,” she said. “We measured their position to be about 600 km 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.
Here’s the abstract published in the journal Geophysical Research Letters.
Ionization of the Earth’s atmosphere by sunlight forms a complex, multilayered plasma environment within the Earth’s magnetosphere, the innermost layers being the ionosphere and plasmasphere. The plasmasphere is believed to be embedded with cylindrical density structures (ducts) aligned along the Earth’s magnetic field, but direct evidence for these remains scarce. Here we report the first direct wide-angle observation of an extensive array of field-aligned ducts bridging the upper ionosphere and inner plasmasphere, using a novel ground-based imaging technique. We establish their heights and motions by feature tracking and parallax analysis. The structures are strikingly organized, appearing as regularly spaced, alternating tubes of overdensities and underdensities strongly aligned with the Earth’s magnetic field. These findings represent the first direct visual evidence for the existence of such structures.
Loi has been awarded the 2015 Bok Prize of the Astronomical Society of Australia for her work. The plasma structures are explained in this clip: