Ice world opens eyes on ‘space weather’
Herald science reporter Jamie Morton is profiling new studies in Antarctica, before he returns to the frozen continent next month. Here he talks to the University of Otago’s Dr James Brundell
Piggy-backing on the world’s military radio signals has been helping New Zealand scientists understand how space weather affects the technology we use every day.
And of all places, they’ve been doing it from Antarctica.
Geomagnetic storms are a temporary disturbance of the magnetosphere surrounding our planet and formed by the interaction of the solar wind and Earth’s magnetic field.
When giant explosions on the sun — or solar flares — send energy, light and high-speed particles into space, the solar wind shock waves typically strike Earth’s magnetic field 24 to 36 hours later.
Coronal mass ejections (eruptions of gas and magnetised material from the sun) similarly have the potential to damage satellites and Earth-bound technologies, disrupting radio transmissions and causing transformer blowouts and blackouts.
Such space storms have been implicated in corroding NZ’s pipelines — and might have even played a role in Auckland’s fuel crisis last year.
“We use Antarctica as a vantage point to access information in the near-Earth atmosphere because here, the magnetic field of the Earth is more directly linked to space,” said Otago University physicist Dr James Brundell, who recently returned from the ice.
A radio receiver near NZ’s Scott Base constantly listens to very low frequency (VLF) bands of radio, sending information to the university.
While commercial AM radio stations broadcast at around 1000 kHz, VLF works in the 3-30 kHz range and can capture solar activity — and even lightning strikes.
One source of radio waves Brundell and his colleagues use is the radio transmitters used by the world’s military.
Although they can’t interpret their messages, they can use the radio source to monitor the upper atmosphere.
“We piggyback on military radio signals to monitor how space weather, generated by the sun, impacts our atmosphere and the technologies we use every day,” he said.
“Satellites, GPS and power networks and mobile phones can all be affected. Our monitoring gives us a better understanding of the volatility of near-Earth space and how we could lessen the impact of space weather events.”
They also use the radio receiver at Scott Base to capture the “crackle” of lightning, generating VLF signals that travel right around the planet.
While lightning is rare in Antarctica, around the world there are many lightning strikes each second that can be heard in the continent.
“Being part of the lightning network allows us all to form a bigger picture of how lightning behaves,” Brundell said.
“Our data has helped to discover that lightning in ash clouds can signal a volcanic eruption.” That could be used by communities and airlines as an early warning system.
On the ice, Brundell and his team were able to replace an old antenna that was disrupted by wind noise.
Antarctica NZ’s acting chief scientific adviser, Dr Fiona Shanhun, said the university’s work fills a gap in two important research groups: the World Wide Lightning Location Network and Aarddvark.
“Without their work in the Ross Sea region, it would be more challenging to triangulate lightning signals or to monitor solar activity.”