AUSTRALIAN farmers are frequently finding Aboriginal stone tools on their land but they’re often nervous about what to do with them, says researchers at ANU. Lead researcher Dr Robyn McKenzie says the team at ANU […]
A study on past reversals of Earth’s magnetic field found a rapid shift occurred within two centuries, and, if such an event occurs in the future, it will increase exposure to the Sun’s radiation.
Prof Andrew Roberts from ANU says the magnetic field’s strength decreases by about 90 per cent when a field reversal occurs, making the Earth much more vulnerable to the Sun’s radiation.
“Earth’s magnetic field, which has existed for at least 3.45 billion years, provides a shield from the direct impact of solar radiation,” says Prof Roberts, who was part of the study led by Prof Chuan-Chou Shen at the National Taiwan University and lead author Dr Yu-Min Chou of the Southern University of Science and Technology in China.
“Even with Earth’s strong magnetic field today, we’re still susceptible to solar storms that can damage our electricity-based society,” he says.
He says a field reversal would have much more of an effect than the solar storm that hit Earth in 1859. A similar magnitude solar storm today would cause major damage to power grids and communications systems worth trillions of dollars.
“Hopefully such an event is a long way in the future and we can develop future technologies to avoid huge damage, where possible, from such events,” he says.
He and his ANU colleague Dr Xiang Zhao from the Research School of Earth Sciences contributed to the study of the paleomagnetic record from 107,000 to 91,000 years ago that is based on precise magnetic analysis and radiometric dating of a stalagmite from a cave in southwestern China.
The stalagmite, which is one metre in length and eight centimetres in diameter, has a candle-like shape and ranges in colour from yellow to dark brown.
“The record provides important insights into ancient magnetic field behaviour, which has turned out to vary much more rapidly than previously thought,” he says.
The study is published in the prestigious journal “Proceedings of the National Academy of Sciences of the United States of America (PNAS)”.