Many people have heard of jet streams, which are rivers of air in Earth’s atmosphere that travel at heights of between 20,000 and 45,000 feet (6,096 and 13,716 meters). Meteorological jet streams separate colder air from warmer air, and the winds of these phenomena can reach speeds of up to 200 miles (322 km) per hour. This time of year, those of us in the Northern Hemisphere are very familiar with where the polar front jet stream is, because it pulls rainstorms, ice storms, and blizzards into its path.
What you might not know is that Earth has another jet stream of sorts. This one doesn’t fly high in the atmosphere. It travels in Earth’s outer core, a shell of dense liquid iron and nickel that begins about 1,800 miles (2,900 km) beneath Earth’s surface. The “iron jet” was detected by the European Space Agency’s (ESA’s) Swarm satellite mission (a group of three satellites that work together to measure Earth’s magnetic field with magnetometers and other instruments). The Swarm satellites detected a stream some 260 miles (420 km) wide flowing within the outer core. Being liquid metal, it was shown to be slower than its atmospheric counterparts, traveling at a rate of only about 25 miles (40 km) per year. Inferences made about the data provided by the Swarm satellites pointed to a flow of iron originating under northwestern Canada and moving westward to the region of the outer core under Siberia.
The scientists hypothesized that the flow of metal passes through an area that separates two regions governed by different physical processes in the core. They referred to this area of fluid as the tangent cylinder, and they suspect that this abstract structure may rest in contact with the outermost edge of Earth’s inner core. The scientists also noted that the iron jet’s flow could be driven by changes in the magnetic field of the outer core or by changes in buoyancy, both of which could be squeezing dense iron and nickel through this tangent cylinder. The scientists observed that the speed of this flow was shown to have increased by two to three times between 1999 and 2016, and they suggest that this recent acceleration of a westward-directed force may be affecting the rotation of Earth’s inner core.
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