Reacción a "Geomagnetic anomalies in the Southern Hemisphere that pose a threat to satellites are a recurring phenomenon, according to research"

Our understanding of the Earth’s magnetic field and its variations over time remains remarkably limited, particularly beyond the last few centuries covered by direct observations. Although it is well established that the geomagnetic field varies on multiple timescales—from rapid secular variation over decades to longer-term changes in field intensity, geometry and even polarity reversals over centuries to millennia—our view of these processes is still fragmentary and geographically biased. This lack of comprehensive knowledge makes it difficult to fully understand the mechanisms that drive geomagnetic variability and, consequently, to make reliable predictions about its future evolution.

In particular, the Southern Hemisphere has long been underrepresented in paleomagnetic and archeomagnetic records. This article makes a valuable contribution by providing new, well-dated archeomagnetic intensity data from South America, demonstrating that weak-field conditions similar to the present-day South Atlantic Anomaly (SAA) have occurred repeatedly over the past two thousand years. These findings are consistent with previous evidence, but they significantly strengthen existing interpretations by filling critical gaps during periods that were previously poorly constrained. A notable strength of the study lies in the quality of its sampling and methodology: the authors rely on carefully selected archaeological materials with robust chronological control and apply rigorous paleointensity protocols, including repeated checks for alteration, corrections for anisotropy and cooling-rate effects, and strict data acceptance criteria. Although this conservative approach reduces the overall success rate, it increases confidence in the resulting intensity record and limits the risk of artefacts or spurious trends, which is particularly important when reconstructing hemispheric-scale features.

Understanding geomagnetic anomalies in the Southern Hemisphere is especially relevant because the Earth’s magnetic field plays a fundamental role in shielding the planet from solar and cosmic radiation. Regions of reduced field strength, such as the SAA today and its past analogues identified in this study, imply a locally weaker magnetic shield. In the modern world, such conditions can affect satellite electronics, spacecraft operations and the performance of satellite-based navigation systems such as GPS, due to enhanced radiation exposure.

Importantly, the study supports the idea that geomagnetic field morphology is controlled by multiscale geodynamic processes, involving interactions between outer core dynamics and regional boundary conditions at the core–mantle boundary. The recurrent westward drift of low-intensity anomalies from the Indian Ocean to South America, and the identification of structured intensity trends over the past millennium, point to a persistent regional control, plausibly linked to large low-shear-velocity provinces beneath Africa. These observations caution against deterministic claims about the near-future evolution of the SAA, whether towards weakening or continued growth, and underscore the need for additional high-quality archeomagnetic data—particularly directional records from the Southern Hemisphere—to better constrain the range of possible geomagnetic futures.