Earth's magnetic field in NOAA/BGS WMM2025: weakest over South America

Get the magnetic field map as a printable poster: https://www.etsy.com/listing/45994207... In the NOAA/BGS World Magnetic Model (WMM2025) for Jan 1, 2026, Earth's magnetic field at the surface is weakest over South America, at about 22,050 nT, roughly a third of its strength near the magnetic poles. We computed the field ourselves from the 168 WMM2025 coefficients (NOAA NCEI and the British Geological Survey) and matched all 100 official test values, then mapped its strength, dip and declination at sea level for Jan 1, 2026: from 22,049 nT at 26.1°S, 60.3°W over northern Argentina, in the South Atlantic Anomaly, to 66,946 nT off Antarctica, south of Australia. The dipole term carries about 93% of the field's power at the surface, its axis tilts 9.2° from Earth's spin axis, and the area inside NOAA's 25,000 nT contour covers about 30 million km², about 6% of Earth's surface. NOAA NCEI's modelled north dip pole travelled about 4,500 km from 1590 to 2025 (about 10 km a year in 1900–1950, about 45 km a year in 2015–2025), and in WMM2025 the field's yearly change for 2026 ranges from −126 nT a year near Oxford, Mississippi to +104 nT a year east of Madagascar. CHAPTERS 0:00 Intro: the field's weak spot 0:32 What the map shows 1:26 A tilted magnet in the core 2:22 The South Atlantic Anomaly 4:00 Which way is down: the dip 5:13 Which way is north: declination 6:11 The wandering north pole 7:20 A field that keeps changing 8:26 Reading the map SOURCES Magnetic field model: NOAA NCEI Geomagnetic Modeling Team; British Geological Survey. 2024: World Magnetic Model 2025 (WMM2025 coefficients WMM.COF and official test values; NCEI states the WMM may be used freely by the public). Retrieved Oct 18, 2026. https://doi.org/10.25921/aqfd-sd83 and https://www.ncei.noaa.gov/products/wo... Chulliat et al. (2025), The US/UK World Magnetic Model for 2025-2030: Technical Report, NOAA NCEI, doi:10.25923/prbc-s316 (navigation standard; core field dominant; geomagnetic and dip poles for 2025.0; South Atlantic Anomaly and satellite risk; compass Blackout Zones). Retrieved Oct 18, 2026. https://library.oarcloud.noaa.gov/noa... NOAA NCEI / BGS, WMM State of the Geomagnetic Field, December 2025 (outer-core flows, not fully predictable; dip pole speeds since Jan 1, 2025; SAA about one-third of the field near the poles, moved about 20 km west; 25,000 nT contour; 18,287 nT at 500 km). Retrieved Oct 18, 2026. https://www.ncei.noaa.gov/sites/defau... North dip pole positions 1590–2025: NOAA NCEI NP.xy modelled poles (gufm1 through 1980, then IGRF; NOAA NCEI data, openly available). Retrieved Oct 13, 2026. https://www.ngdc.noaa.gov/geomag/data... and https://www.ngdc.noaa.gov/geomag/data... Satellite basemap: NASA Earth Observatory, Blue Marble Next Generation with topography and bathymetry, December 2004 (Reto Stöckli, NASA EO; NASA imagery, not copyrighted). Retrieved Oct 22, 2026. https://eoimages.gsfc.nasa.gov/images... Coastlines and borders: Made with Natural Earth (public domain). https://www.naturalearthdata.com Method: our own synthesis of the NOAA/BGS WMM2025 (degree 12) at 0 km above the WGS 84 ellipsoid for Jan 1, 2026, on a 0.5° grid; yearly change = the model's secular variation; areas on a 6,371 km sphere. Dipole map = degree 1 terms; power share = Lowes-Mauersberger spectrum. Dip poles where the horizontal field is zero; pole speeds from yearly NP.xy positions, averaged per period. Declination colours saturate at 30°. The dipole axis on the globe is an illustration. Music: 'Uptempo atmospheric electronic tune' by obscure music, CC0 1.0 (public domain), via OpenGameArt. https://opengameart.org/content/uptem... Transition sounds: 'Swishes Sound Pack' by artisticdude, CC0 1.0, via OpenGameArt (slowed and filtered). https://opengameart.org/content/swish... Narration: AI-generated voice. Maps, animation and analysis: Restless Planet. More Planet Scale videos:    • Planet Scale   More Earth-science map posters: https://www.etsy.com/shop/RestlessPla... #RestlessPlanet #magneticfield #geomagnetism #earthscience New maps every Tuesday and Friday. Subscribe:    / @restlessplanetearth