A magnetometer is a sophisticated type of compass that measures not only the direction but also the strength of the Earth's magnetic field.

There are many types of magnetometers. At Halley and on the AGOs, we use EDA fluxgate and search coil magnetometers.

A magnetic field is caused by electrical currents. The magnetic field measured by a magnetometer on the Earth's surface is made up from a number of different current systems inside the earth and in geospace. We interpret magnetometer data to remotely sense these geospace currents.