A paper, published in the journal Proceedings of the National Academy of Sciences, describes how a team of scientists used information from ESA’s Swarm satellite mission to detect a new type of magnetic wave that sweeps across the ‘surface’ of Earth’s outer core – so where the core meets the mantle. This mysterious wave oscillates every seven years and propagates westward at up to 1500 kilometres a year. These waves align in columns along Earth’s axis of rotation. The motion and magnetic field changes associated with these waves are strongest near the equatorial region of the core.