The liquid iron in the Earth’s outer core does not always behave as expected. When it changed direction in an unexplained manner, ESA satellites provided data on the flow direction, which helped scientists better understand the dynamics at the center of our planet.
Change in the direction of the core’s movement
The molten core, which rotates at a depth of about 2,200 km beneath our feet, generates the Earth’s geomagnetic field as it moves. By measuring small changes in the magnetic field, scientists have historically concluded that the core is generally moving westward. But in 2010, it unexpectedly changed course deep beneath the Pacific Ocean and began moving rapidly eastward. The reasons for this puzzling reversal in the flow of molten material remain a mystery. But satellites, including ESA’s Swarm and CryoSat, provided data that was analyzed and published.
The study, published in the Journal of Studies of Earth’s Deep Interior, analyzes both ground-based observations and satellite data from 1997 to 2025. The study utilized data from ESA’s Swarm and Cryosat missions, as well as data from the German CHAMP and Ørsted missions. A study has shown that in 2010, a large area of iron-rich fluid beneath the equatorial Pacific Ocean shifted from a weak westward flow to an intense eastward flow.
Core motion and magnetic field generation
It was previously believed that the outer core moves relatively steadily—this sudden change in flow indicates that this is not always the case. The study provides insight into the turbulent processes that generate the Earth’s magnetic field and suggests possible links between the dynamics of the outer core and changes occurring deeper within the planet.
The lead author of the study, Frederik Dahl Madsen of the University of Edinburgh’s School of Geosciences, said: “The large-scale flow reversal beneath the Pacific raises new questions about the behavior of Earth’s deep interior. Scientists now want to understand whether the reversal represents a short-lived fluctuation, part of a repeating oscillation, or a new stable equilibrium for core circulation. Continued monitoring will be essential to determine how the flow evolves over the coming years.”
The Earth’s magnetic field is generated by motion in the liquid outer core, where electrically conductive molten iron circulates around the solid inner core. This geodynamo is constantly evolving, but many of its long-term flow patterns appear to be relatively stable over decades of observation.
Swarm satellites detect the event
Launched in 2013, the three Swarm satellites carry highly sensitive magnetometers capable of mapping Earth’s magnetic field with exceptional precision. Flying in carefully coordinated orbits, the satellites can distinguish magnetic signals originating from the core from those generated in the crust, oceans, ionosphere, and magnetosphere.
These observations enabled researchers to reconstruct evolutionary flow patterns at the core-mantle boundary and identify abrupt changes associated with the Pacific reversal and the 2017 geomagnetic jerk.
According to Anja Stromme, the ESA Swarm mission manager, the long-term dataset provided by Swarm is crucial to this research. She noted: “Although Swarm was launched after the dramatic reversal event of 2010, it has provided high-precision data that tell us about Earth’s inner core in the period that followed”.
Importantly, Swarm has provided continuous global coverage for many years, allowing scientists to track how the core’s dynamics change over time, rather than relying solely on ground-based magnetic observatories. Long-term satellite-based magnetic measurements allow researchers to track changes in the geodynamo in near real time and improve models of the Earth’s magnetic field evolution. Upcoming observations from missions such as Swarm will play a crucial role.
Satellite data also enabled researchers to identify wave-like accelerations and rapidly changing current structures that might otherwise have remained hidden in noisier datasets. The study also suggests that the eastern flow may now be weakening again after peaking several years ago, raising the possibility that the phenomenon represents temporary fluctuations or is part of a longer natural cycle in the core’s dynamics.
Understanding our Earth system
Although these processes take place deep beneath the Earth’s surface and pose no danger to people or the climate, they are fundamental to understanding how our planet works. The movement of molten iron in the Earth’s outer core generates the Earth’s magnetic field, which protects the planet from charged particles coming from the Sun. Without it, the Earth’s atmosphere and technological infrastructure would be more vulnerable to harmful solar radiation.
The magnetic field is not static. It changes slowly over time as the core’s flow evolves, affecting everything from navigation systems to the operation of spacecraft and models of space weather near Earth. Therefore, understanding how and why the core changes is important both scientifically and practically.
This study raises interesting questions about how the deepest layers of the Earth are dynamically interconnected. As the magnetic field continues to change, satellite missions are providing an increasingly detailed view of the dynamic processes occurring deep within our planet, revealing that the Earth’s core may be far more variable and complex than previously thought.
According to phys.org
