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Continuing the 100-year tradition of Antarctic magnetic measurements - 18/01/2017

New Zealand scientists are in Antarctica this month collecting measurements of the Earth’s magnetic field that were first taken by Scott’s Terra Nova Expedition over 100 years ago.

Tanja and Neville

Researchers Tanja Petersen and Neville Palmer of GNS Science who are in Antarctica collecting measurements of the Earth’s magnetic field to help update global models of the strength and location of the South Magnetic Pole. Photo – Margaret Low, GNS Science.

The measurements, which are collected at roughly five-yearly intervals, show Earth’s South Magnetic Pole is moving northwest by 10km to 15km a year.  It is currently some distance off the Antarctic coast and due south of Australia.

The magnetic pole is where the Earth’s magnetic field lines are directed vertically upwards into space.  The magnetic field is crucial as it protects the Earth from the solar wind – the stream of charged particles that constantly bombards Earth from outer space.

Without the magnetic field, the atmosphere as we know it would not exist.

Researchers Tanja Petersen and Neville Palmer of GNS Science are spending two weeks in the Dry Valleys collecting detailed measurements of the magnetic field’s strength and location.

They are using two instruments mounted on tripods. The first is a magnetic theodolite that measures both the horizontal angle and the inclination of the magnetic field.

Their other instrument – a proton magnetometer – gives a digital readout of the strength of the magnetic field in units called nanoTeslas or gammas. Both instruments are sensitive and require careful handling.

The pair will first visit Lake Vanda, 125km west of Scott Base, where they will camp for four nights in tents. They will set up their tripod over an aluminium pin in a prominent rock.

After Lake Vanda, they head to Cape Evans 30km from Scott Base, where they will take measurements at a small shelter near Scott’s hut. The measurements are taken at an exact mark inside the shelter.

Both sets of measurements are deliberately taken some distance from Scott Base as it is built on volcanic material ejected from Mount Erebus. The volcanic rocks are high in the iron-rich mineral magnetite, which can give anomalous magnetic readings.

Dr Petersen said repeat measurements show how the Earth’s magnetic field is changing due to the dynamic nature of the Earth’s iron-rich inner core.

“Scientists will use these observations to gain a better understanding of the motion within the Earth’s core creating our protective geomagnetic shield and how it changes over time,” she said.

“The data also provides an update on the exact location of the South Magnetic Pole and will help to build global geomagnetic models that are used in every-day applications.”

The measurements will also help to gain a better understanding of the effect of solar radiation on the Earth and therefore improve our ability to minimise the impact of a large magnetic storm on communications equipment. 

Dr Petersen said it was important that New Zealand played its part in a global sense by providing accurate magnetic measurements in a region where magnetic data was sparse.

With the gradual northward movement of the magnetic pole, the strength of the field at Scott Base had decreased by as much as 10 percent over the past century.

 

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