Insights into Editorial: Iron ‘jet stream’ detected in Earth’s outer core
Jet streams are typically associated with weather patterns, storms and the changing of the seasons but they don’t just appear in the atmosphere. The European Space Agency has discovered a jet stream deep below the surface of the Earth, and it’s moving at increased speeds. This is a remarkable new feature in Earth’s molten outer core.
Scientists describe this “jet stream” as a fast-flowing river of liquid iron that is surging westwards under Alaska and Siberia.
How was it discovered?
The discovery was made by researchers using Esa’s Swarm satellites. Launched in 2013, the trio of satellites is used to measure the different magnetic fields that stem from Earth’s core, mantle, crust, oceans, ionosphere and magnetosphere.
About swarm mission:
Swarm is the fifth Earth Explorer mission approved in ESA’s Living Planet Programme. The objective of the Swarm mission is to provide the best-ever survey of the geomagnetic field and its temporal evolution as well as the electric field in the atmosphere using a constellation of 3 identical satellites carrying sophisticated magnetometers and electric field instruments.
- Swarm’s data help scientists understand better how the field is generated, and why it appears to be weakening.
- All three satellites in the Swarm constellation are identical. Their super-sensitive instrumentation acts rather like a 3D compass, enabling the precise strength and direction of the magnetic field to be determined all around the globe.
- The trio’s construction was led by the Astrium company, predominantly in Germany and the UK. Engineers have had to ensure the magnetism generated by the satellites’ own internal electronics does not obscure the mission’s subtle scientific measurements.
- This has meant putting the instruments on the end of a long boom to keep them separate from the main spacecraft body. It has given Swarm a very distinctive look – like giant mechanical rats with long tails.
Uses of swarm data:
The major part of Earth’s global magnetic field is generated by convection of molten iron within the planet’s outer liquid core, but there are other components that contribute to the overall signal. These include the magnetism retained in rocks, and there is even an effect derived from the movement of salt water ocean currents. Swarm will attempt to tease apart these various factors, to get a clearer picture of the field’s true origins and its changing behaviour.
Other uses of the Swarm data will embrace investigations of the electrical environment of the high atmosphere and the way this interacts with the solar wind – the continuous stream of charged particles billowing away from the Sun.
Existence of earth’s magnetic field:
Earth’s magnetic field behaves like a bar magnet with a north pole and south pole with magnetic field lines stretching into space, creating a bubble known as the magnetosphere. On the day side of Earth, the solar wind compresses the magnetosphere and charged particles stream around the planet and follow field lines into the poles, spawning the colorful auroras. On the side of Earth facing away from the sun, the magnetosphere is blown out like the tail of a comet.
- The magnetic field exists because of an ocean of superheated, swirling liquid iron that makes up the outer core. Like a spinning conductor in a bicycle dynamo, this moving iron creates electrical currents, which in turn generate our continuously changing magnetic field.
- But magnetism from rocks in the Earth’s crust and from the circulation of the oceans also contribute to the magnetic field, and solar activity is also an influence in the ionosphere and magnetosphere, the protective bubble around the planet.
Why scientists are interested in studying earth’s magnetic field?
Earth’s core is buried under about 1,900 miles (3,000 kilometers) of rock, so scientists study it indirectly by measuring the planet’s magnetic field. For instance, changes in the magnetic field suggested that liquid iron in the outer core moves faster in the Northern Hemisphere, largely beneath Alaska and Siberia.
- The magnetic field appears to be weakening, according to researchers, and the magnetic poles have been drifting over the last few decades, leading some experts to suggest Earth is on the verge of a pole reversal.
- The magnetic reversal has occurred, on average, about once every 250,000 years. But research shows the last time it happened was 780,000 years ago.
- Scientists want to study the reversal’s potential impact on modern humans, especially high-tech electrical grids, navigation and communications.
How jet stream was discovered?
The jet stream, located roughly 3,000 km (1,860 miles) below the Earth’s surface — a region where the molten outer core meets the solid mantle — is estimated to be over 260 miles wide. Its speed of over 25 miles a year is three times faster than the typical speed of liquid in the outer core and hundreds of thousands of times faster than the speed at which Earth’s tectonic plates move.
A pattern of ‘flux patches’ in the northern hemisphere, mostly under Alaska and Siberia, led to the discovery of jet stream in the core. These high-latitude flux patches are like bright spots in the magnetic field and they make it easy to see changes in the field. Swarm reveals that these changes are actually a jet stream moving at more than 25 miles a year – three times faster than typical outer-core speeds and hundreds of thousands of times faster than Earth’s tectonic plates move.
Scientists explain it as acceleration in a band of core fluid circling the pole, like the jet stream in the atmosphere.