Electric circuit may link thunderstorms and solar activity

Electric field mill
Electric field mill (Photo: Peter Jansen)
Air earth current meter ball

29 December 2004

Dramatic lightning strikes and thunderstorms drive electricity around the globe and form part of a "global electric circuit" that atmospheric scientists will attempt to measure in Antarctica this summer.

To do this, the Australian Antarctic Division's (AAD) Dr Gary Burns and Mr Peter Jansen will deploy sensitive electronic instruments inland of Casey station and, with the help of Russian scientists, into the coldest known place on Earth… Vostok.

The instruments will measure the electric current that flows between the ground and the lower reaches of the ionosphere (about 70km up). Lightening provides a visual indication of the current travelling upwards towards the ionosphere, where it then trickles back to Earth in regions remote from thunderstorm activity, such as Antarctica.

If the scientists can accurately measure the current, they may be able to determine whether changes in the sun – through solar wind and cosmic rays – have an effect on the Earth's weather system.

"As the solar wind increases over its 11 year cycle, it restricts cosmic rays from entering the Earth's atmosphere, which in turn changes the conductivity of the atmosphere," Dr Burns says.

"This could alter the global electric circuit and the conditions under which thunderstorms develop, perhaps providing a link between solar activity and climate."

Accurate measurements of the current could also enable scientists to monitor changes in global thunderstorm activity as the world warms.

"It's thought that an increase in temperature of one degree Celsius could increase thunderstorm and lightening activity by 10 percent. So changes in the global electric circuit could provide an indication of the way the Earth's weather is changing," Dr Burns says.

By measuring the current in at least two places on the Antarctic continent, the scientists hope to establish the accuracy with which it can be detected.

"It's very difficult to measure the current flowing through the global electric circuit because day-to-day variations in temperature and wind mask the electric signal," Dr Burns says.

"But Vostok is an ideal site to measure it because it is distant from thunderstorm activity and the weather is fairly stable and calm. We hope to find suitable conditions inland of Casey station, so that we can compare measurements at each place."

The scientists will test their instruments – an 'electric field mill' and an 'air-earth current meter' – at the Casey site for up to six weeks. A new electric field mill will be flown to Vostok to replace one deployed in 1998.

"We've made a few changes to the electric field mill to improve its accuracy and ease of repair," Dr Burns says.

The scientists will travel to Antarctica on the AAD's fourth voyage south this summer, aboard the Vasiliy Golovnin. The voyage will resupply Australia's Casey and Mawson stations and retrieve personnel.

The ship will sail from Hobart at 5pm today.