Eddie Gonzales Jr. – MessageToEagle.com – The liquid iron in Earth’s outer core sometimes changes direction unexpectedly. ESA satellites have provided flow data, enabling scientists to better understand the planet’s internal dynamics.
The magnetic field is thought to be largely generated by an ocean of superheated, swirling liquid iron that makes up Earth’s the outer core 3000 km under our feet. Acting like the spinning conductor in a bicycle dynamo, it generates electrical currents and thus the continuously changing electromagnetic field. Other sources of magnetism come from minerals in Earth’s mantle and crust, while the ionosphere, magnetosphere and oceans also play a role. ESA’s constellation of three Swarm satellites is designed to identify and measure precisely these different magnetic signals. This will lead to new insight into many natural processes, from those occurring deep inside the planet, to weather in space caused by solar activity. Image credit: ESA/ATG Medialab
The molten core, located about 2200 km beneath the surface, generates Earth’s geomagnetic field. Scientists have traditionally inferred that the core flows mainly westward by measuring subtle changes in the magnetic field.
In 2010, it suddenly changed direction, far below the Pacific Ocean, and began moving quickly east. Scientists still do not know why the flow of molten material reversed. However, satellites such as ESA’s Swarm and CryoSat have collected data that researchers have now studied and shared.
A recent study in the Journal of Studies of Earth’s Deep Interior examines ground and satellite data collected from 1997 to 2025. The research draws on data from ESA’s Swarm and Cryosat missions, the German CHAMP mission, and the Ørsted mission. The findings indicate that in 2010, a large region of iron-rich fluid beneath the equatorial Pacific shifted from weak westward to strong eastward motion.
The outer core system was previously thought to move in a comparatively stable way – this dramatic change of flow suggests this is not always the case. The study provides insights into the turbulent processes that generate Earth’s magnetic field and hint at possible links between outer core dynamics and changes occurring deeper within the planet.
“The large-scale flow reversal beneath the Pacific raises new questions about the behaviour 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,” said Lead author of the study, Frederik Dahl Madsen, of the University of Edinburgh – School of Geosciences.
Frederik also said that the research model shows the Pacific eastward flow has weakened since 2020, adding that the rise of the strong eastward flow in the Pacific is contemporary with a change in behaviour in the inner core, as inferred from geodesy and seismology.
So, the researchersand hypothesise that these changes in the deep interior are associated with the changes in flow beneath the Pacific.”
Earth’s molten core detected from space
Earth’s magnetic field is created by movement in the liquid outer core, where molten iron that conducts electricity moves around the solid inner core. This geodynamo is always changing, but many of its long-term flow patterns have stayed fairly steady over decades of observation.
The three Swarm satellites (launched in 2013), carry highly sensitive magnetometers that map Earth’s magnetic field with exceptional precision. By flying in carefully coordinated orbits, the satellites can distinguish magnetic signals originating from the core from those produced by the crust, oceans, ionosphere, and magnetosphere.
Thanks to observations, the team reconstructed evolving flow patterns at the core–mantle boundary and identified the sudden changes associated with the Pacific reversal and the 2017 geomagnetic jerk.
“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,” ESA’s Swarm Mission Manager, Anja Stromme said.
“Importantly, Swarm provides continuous global coverage over many years, allowing scientists to track how core dynamics evolve over time rather than relying only on ground-based magnetic observatories. Long-duration satellite magnetic measurements allow researchers to follow changes in the geodynamo in near-realtime and improve models of Earth’s magnetic field evolution. Future observations from missions such as Swarm will play a crucial role.”
Additionally, the team detected wave-like accelerations and rapidly changing flow structures that may otherwise have remained hidden within noisier datasets. The study also suggests that the eastward flow may now be weakening again after reaching a peak several years ago, raising the possibility that the event represents a temporary oscillation or part of a longer natural cycle in core dynamics.
Understanding our Earth system
Although these processes occur far below Earth’s surface and pose no danger to people or climate, they are fundamental to understanding how our planet works. The movement of liquid iron in the outer core generates Earth’s magnetic field, which shields the planet from charged particles streaming from the Sun. Without it, Earth’s atmosphere and technological infrastructure would be far more exposed to harmful solar radiation.
The magnetic field is not fixed. It slowly changes over time as the core flow evolves, affecting everything from navigation systems to spacecraft operations and models of near-Earth space weather. Understanding how and why the core changes is therefore important both scientifically and practically.
“This study shows that regional changes can emerge rapidly within just a decade. The findings may also help scientists investigate possible interactions between Earth’s outer core, inner core, and lower mantle, thereby providing further insights into the core-mantle boundary, a critical region for deep Earth dynamics,” Elisabetta Iorfida, ESA’s Swarm Mission Scientist, said.
The Pacific reversal challenges the assumption that the outer core is dominated by a stable westward circulation.
Written by Eddie Gonzales Jr. – MessageToEagle.com Staff Writer