Magnetometers

Several kinds of natural waves in the ultra-low-frequency (ULF) range are generated in Earth’s space environment (the magnetosphere, bounded by Earth’s magnetic field as it extends into space). Most of these can penetrate the atmosphere and be detected on the ground by search coil magnetometers.

Monitoring wave activity using a search coil magnetometer can tell us lots about activity and energy flow in Earth’s space environment. One type of wave tells us about interactions between the solar wind and Earth’s magnetosphere. Another type is generated in association with bright auroral displays.

Waves provide evidence of nearby auroras even when clouds prevent visible light from reaching the ground. Yet another type of wave is generated at high altitudes inside Earth’s magnetosphere by instabilities of charged particles that make up the plasma trapped by Earth’s magnetic field. These help clear out energetic particles injected by magnetospheric storms as well as some of the high-energy electrons from the Van Allen radiation belts.

The Halley search coil plays a key role in international science related to the NASA Radiation Belt Storm Probes satellite mission, launched in August 2012. Halley is located at the foot of magnetic field lines that thread the outer portion of Earth’s radiation belts, and can provide continuous coverage of waves generated in these belts.

The fluxgate magnetometer measures the strength and direction of the Earth’s magnetic field. On a long timescale, this is driven by what goes on under your feet. It depends on where you are compared to the spinning iron core of the globe and the local geology. However, we are interested in short timescales, from seconds to hours. Here the magnetic field is driven by what happens above us in space.

Changes to the field strength and direction measured at ground level
are caused by distortion of the Earth’s magnetic field by the pressure of the solar wind (charged particles coming from the Sun) and by electrical currents flowing about 100km up in the ionosphere (the ionised part of our atmosphere at the edge of space). These are driven by solar effects but also by processes occurring in the ionosphere and the magnetosphere – a giant magnetic bubble surrounding the Earth and extending beyond the Moon.

As a result, the fluxgate magnetometer provides data to let us study the solar wind and the ‘space weather’ high up in the atmosphere and space.

Low-powered magnetometers (LPMs) measure magnetic fluctuations caused by currents flowing in the ionosphere high above us. This data can be used to produce maps of space weather in the region around the Earth where satellites orbit. The ability to predict space weather is a significant advantage to the telecommunications and aerospace industries, helping them to better protect spacecraft.

There are a dozen LPMs mostly in the deep field, including one very near the South Pole. BAS has also sold instruments to China, Japan and Italy that, together with the BAS instruments, form a network across Antarctica. They operate unmanned all year round, powered only by a solar panel – hence the low-powered part of the name.

Each year some of the sites are serviced by Twin Otter aircraft from Halley, often by one of the wintering engineers.