The newest geomagnetic field analysis built from more than six years of continuous satellite measurements has revealed a pattern of magnetic deterioration that is stronger, faster, and more asymmetric than previous global models detected. The CGGM-2 model, created using data from the China Seismo Electromagnetic Satellite, provides a fresh look at how Earth’s magnetic shield has evolved since 2018. The findings confirm that the South Atlantic Anomaly continues to deepen and spread. The western and eastern hemispheres are diverging in magnetic intensity. The global field is shifting unevenly. The north magnetic dip pole is still racing across the high latitudes. Several of the largest scale structural components of the field show substantial disagreement with other long-established satellite models. Each of these trends can be explained within the context of normal core dynamics, but their combination and timing form a pattern that specialists will monitor closely because it reflects unusual levels of magnetic reconfiguration within a short interval.
The CGGM-2 project was designed to evaluate the geomagnetic main field, its crustal contributions, the changes occurring inside the core, and the outward effects that appear in satellite measurements. The benefit of this new model is its reliance on a satellite that revisits the same locations every five days. That regularity allows the model to capture subtle nonlinear changes in the field that other models, which rely on less repetitive orbital sampling, may smooth over. The result is a more detailed map of temporal variability. The analysts used B-splines to describe non-linear changes through time at a scale that includes both the field itself and its first and second time derivatives. This method can highlight abrupt or rapidly intensifying changes in the field. Since the model is built from more than six years of continuous observations, it has become possible to evaluate how the South Atlantic Anomaly has changed with far greater precision.
The South Atlantic Anomaly remains the most significant expression of global magnetic weakening. It is the region where the magnetic field is weakest at Earth’s surface, and where satellites experience higher radiation exposure due to the reduced shielding. The new model shows that the second minimum within the anomaly, located near the zero degree meridian, continues to weaken at a rate that greatly exceeds the weakening at the primary western minimum near sixty degrees west. The eastern minimum lost approximately six hundred nanotesla of field strength between 2018 and 2025, compared with about two hundred nanotesla in the western minimum. This creates an imbalance inside the anomaly. It means that the anomaly is not only weakening but also developing structural complexity, with two minima that behave differently in intensity and spread. The second minimum is expanding laterally, indicating a sustained change in the underlying field that cannot be dismissed as a short-term fluctuation. This expansion supports a long term trend toward a broader depressed magnetic region that affects an increasingly large portion of the South Atlantic and African sectors.
The western minimum inside the South Atlantic Anomaly has shown continued westward drift. The minimum shifted by about one point six degrees over seven years, equal to roughly zero point two degrees per year. Drift in magnetic minima and maxima is expected as the core flows beneath the mantle, but drift combined with uneven weakening across two distinct minima raises questions about deeper changes in the core flow patterns. The satellite record is clear that the second minimum near the zero degree meridian is weakening at three times the rate of the western feature, which creates an unusual deformation in the field. Satellite maps generated from the CGGM-2 model show a distinct deepening in the eastern minimum accompanied by spreading contours that trace the outline of a widening depression in the field. When two minima evolve unevenly, it can create distortions in the field that influence how charged particles move in near-Earth space. This results in practical consequences for satellite operations but also points toward possible structural reorganizations inside the liquid outer core.
The model identifies regions along the ninetieth west and sixtieth east meridians where field intensity changes approach eight hundred nanotesla. These magnitudes represent significant shifts in the magnetic environment over a relatively short period. The spatial pattern shows broad areas of decline in the western hemisphere and broad areas of increase across the eastern hemisphere. This hemispheric asymmetry has been seen in earlier models and has often been associated with variations in how the core generates and transports magnetic flux. The new results reinforce that the asymmetry is persistent and strengthening. This creates long-term concerns about how field lines are organized inside the core and whether deeper flux systems are migrating, splitting, or reorganizing.
The movement of the dip poles adds to this picture. The north magnetic dip pole has been migrating at a rapid rate for more than two decades, and the new model confirms that the speed remains high. Between 2020 and 2025, its motion averaged about forty one kilometers per year. Predictions from the CGGM-2 model suggest that this may decrease to around thirty five kilometers per year by 2027, which is still fast relative to twentieth century changes. The south dip pole remains slower, near nine kilometers per year. Dip pole velocities reflect changes in the internal field geometry. Rapid movement over this timescale indicates continuing shifts in the balance of magnetic flux inside the core. When seen together with the deepening eastern South Atlantic minimum and hemispheric intensity divergence, the overall story points to increased internal variability rather than a stable configuration.
One of the more technical findings in the study involves discrepancies between the new model and the CHAOS-7 satellite model at the lowest spherical harmonic degrees. These degrees represent the largest scale global structures of the magnetic field. Disagreements between models at these scales often signal that underlying physical processes are changing in ways that challenge existing parameterizations. The CGGM-2 model shows differences in degrees two and three that reach thirty to fifty nanotesla squared. These are not minor deviations and cannot be attributed only to measurement noise or instrument alignment. The authors note that part of the difference could arise from boom deformation on the satellite or magnetic disturbances at high latitudes. However, these effects are typically accounted for in model evaluation. When the largest structural differences appear at low degrees, it means that the latest measurements are capturing a different global configuration than previous models. This strengthens the interpretation that Earth’s field is undergoing significant reorganization.
The study also validates that despite instrument imperfections, the CGGM-2 model performs exceptionally well at predicting secular variation between 2025 and 2030. Among all candidate models submitted for the International Geomagnetic Reference Field, the CGGM-2 secular variation model had some of the smallest differences from the final official model. This suggests that the satellite’s repeating ground track is particularly effective for observing short term field evolution, even when vector attitude uncertainties create limitations for crustal field measurements. This is important because secular variation represents the rate of change of the field. High precision in this component gives researchers better ability to track acceleration patterns, jerks, and other nonlinear features that signal changes in core dynamics.
The paper includes a detailed examination of how the field changed between 2018 and 2025. Maps of global intensity show that the most substantial reductions occurred in the South Atlantic sector. The anomaly’s intensity decreased sharply in the eastern zone near the zero degree meridian and more moderately in the western zone. The anomaly’s contours expanded outward, confirming that the depressed region is enlarging. The total changes along key meridians reach several hundred nanotesla, which is consistent with a system experiencing differential flux transport inside the core. The greatest increases in intensity appear across the eastern hemisphere, which pushes the global balance further away from symmetry. It is rare for a global field to experience this level of hemispheric differentiation over a seven year interval.
The authors also compare their findings with the officially adopted field for 2020, 2025, and the predicted secular variation through 2030. Their candidate models performed within expected margins, but the structural differences at low degrees continued to appear in the comparisons. This reinforces the observation that certain large scale field components are diverging from traditional model expectations. Some of these differences relate to high latitude disturbances and satellite alignment issues, but not all can be explained away. The core appears to be developing new patterns of flow and flux emergence that propagate into the surface field.
A notable conclusion in the paper concerns the potential for improvement once the CSES-02 satellite launches. The next mission will produce cleaner high latitude data and improve corrections for boom deformation. While this will sharpen crustal field calculations, it will also enable far more accurate monitoring of the secular variation and acceleration patterns that reveal deep core processes. If the trends identified in the CGGM-2 model persist, the next generation of data may show whether the South Atlantic Anomaly will continue its rapid expansion, whether the eastern minimum will deepen further, and whether global asymmetry will intensify.
The South Atlantic Anomaly has long been monitored due to its effect on satellites and high altitude flights. The phenomenon itself is not unusual because the field has always varied through time. What sets the current phase apart is the combination of rapid deepening in the eastern minimum, consistent westward drift in the western minimum, broad hemispheric divergence, and rapid dip pole movement. These trends occur alongside disagreements at low spherical harmonic degrees that represent changes in the global structure of the field. When all evidence is aligned, the interpretation is that Earth’s magnetic field is currently experiencing a more dynamic and irregular evolutionary period.
Throughout the record, the field continues to weaken in the western hemisphere while strengthening in the eastern hemisphere. This creates a global gradient that influences how magnetic flux is distributed across the core mantle boundary. The gradient also shapes the geometry of the magnetosphere. Over time, this may alter how the field couples with solar wind flow. Even small changes in the global dipole orientation or intensity have meaningful consequences for space weather interactions. The more Earth’s field diverges from symmetry, the more unpredictable certain radiation belt behaviours may become. The continued decline inside the South Atlantic Anomaly suggests that satellites crossing this region will face progressively worse conditions throughout the decade.
While the study does not claim that the geomagnetic field is heading toward a reversal, the documented behaviour in the anomaly’s twin minima bears resemblance to certain patterns modeled in core flow simulations. In those simulations, asymmetric minima can be a precursor to field restructuring events. However, it is important to note that the field has undergone many large variations in the past without reversing. What matters is that the system today is showing increased complexity. This creates scientific urgency to monitor the field closely as new data become available.
The newly mapped differences between 2018 and 2025 provide one of the clearest pictures yet of how much the magnetic field can change in less than a decade. The expansion of the anomaly’s secondary minimum demonstrates that the region where Earth’s shielding is weakest is growing. The steep decline near the zero degree meridian illustrates that internal core flows are exhibiting strong directional preference. The shift in dip pole speed patterns indicates that the balance of flux inside the core is also changing. The strong contrasts between eastern and western hemispheres show that the field is no longer adjusting in a uniform way. With new satellites and updated analyses, the immediate scientific question will be how these trends continue to unfold over the next five years.
The CGGM-2 findings do not present a stable field. They present a field in motion that is changing faster in some regions than expected and developing structures that require close attention. The deepening secondary minimum inside the South Atlantic Anomaly is the clearest sign of this change. It has weakened roughly three times faster than the western minimum and shows clear evidence of expansion. This is the feature that will likely receive the most scrutiny and will act as a critical indicator for understanding whether the present era is part of an extended period of geomagnetic instability. The most pressing concern is not that the field is about to collapse, but that its behaviour is demonstrating higher volatility. Scientists will track the motion of the minima, the acceleration of the dip poles, and the degree two and three variations with increasing urgency as more sophisticated models come online.
The new model gives a detailed view of how the magnetic field evolved between 2018 and 2025. It shows that the weakening in the South Atlantic is not slowing. It shows that the eastern hemisphere continues to gain intensity while the western hemisphere continues to lose it. It shows that large scale differences between satellite models emerge at the very levels that represent the global magnetic structure. It shows that nonlinear behaviour inside the core is becoming more evident as new mathematical approaches reveal previously hidden variations. All of this paints a clear picture. The magnetic field is currently in a phase of heightened internal variability. The next generation of satellite measurements will determine whether this is a temporary fluctuation or part of a larger trend.
Source:
Second generation of CSES global geomagnetic field model (CGGM-2) and associated candidate models for IGRF-14, Earth, Planets and Space (2026).
PDF: https://doi.org/10.1186/s40623-025-02361-z
