ESA Swarm maps magnetic weak spot

ESA’s Swarm satellites are the source behind the “magnetic weak spot” maps circulating online this week. The European Space Agency said the mission’s three spacecraft are designed to measure Earth’s magnetic field and its changes over time, including the South Atlantic Anomaly — a low-field region stretching between South America and Africa. ESA said in an October 2025 update that, using 11 years of Swarm data, scientists found the anomaly had expanded by an area nearly half the size of continental Europe since 2014. ### What is the “weak spot” people are talking about? The South Atlantic Anomaly is a region where Earth’s magnetic field is weaker than surrounding areas, ESA said. The agency has described it as a zone extending from Africa to South America that can create technical disturbances for satellites in orbit because energetic charged particles can reach lower altitudes there. (esa.int) ESA said Earth’s magnetic field is generated largely by flows of liquid iron in the outer core, about 3,000 kilometers below the surface. Swarm was built to separate signals from the core, mantle, crust, oceans, ionosphere and magnetosphere so scientists can track how that field changes. (esa.int) ### What exactly did Swarm measure? Swarm consists of three satellites that carry magnetometers and electric-field instruments, according to ESA Earth Online. ESA said the constellation achieved its initial configuration on April 17, 2014, and is dedicated to producing a detailed survey of Earth’s geomagnetic field and its temporal evolution. (esa.int) In the October 2025 analysis, ESA said researchers used 11 years of Swarm measurements to compare the anomaly’s extent in 2014 and 2025. The result was a larger weak-field area, with ESA saying the anomaly had expanded by nearly half the size of continental Europe over that period. (earth.esa.int) ### Why does this matter for satellites and space weather? ESA said the anomaly matters because weaker magnetic shielding allows more high-energy particles to affect spacecraft systems. The agency has also used Swarm data for space-weather work, including a near-real-time hazard index developed with the British Geological Survey to track local geomagnetic variations globally. (esa.int) NOAA said the May 2024 solar storm reached G5, the highest level on its geomagnetic storm scale. NOAA’s Space Weather Prediction Center said the event began on May 10, 2024, after multiple coronal mass ejections from active region 3664, and later described it as the largest geomagnetic storm of Solar Cycle 25. ### Why was Mars mentioned in the same conversation? (esa.int) Mars came up because ESA often uses magnetic-field and solar-wind stories together to show how planetary environments respond differently to the Sun. ESA said Mars lacks a strong global magnetic field, so the solar wind can interact directly with its upper atmosphere and help strip particles away over time. (repository.library.noaa.gov) In a March 5, 2026 update, ESA said its Mars orbiters observed a May 2024 solar superstorm hitting the Red Planet, producing spacecraft glitches and a “supercharged upper atmosphere.” Earlier Mars Express findings also linked solar wind interaction to atmospheric erosion and water loss. (sci.esa.int) ### Where can readers see the underlying ESA material? ESA publishes Swarm mission updates on its main mission pages and through Earth Online. ESA also says the VirES for Swarm platform provides interactive access to mission data and geomagnetic models for researchers and the public. ESA’s latest public write-up on the weak spot is the October 13, 2025 article “Swarm reveals growing weak spot in Earth’s magnetic field.” NOAA’s public archive on the May 2024 storm remains available through the Space Weather Prediction Center, and ESA’s March 5, 2026 Mars update documents how that same solar activity affected Mars. (esa.int 1) (esa.int 2) (esa.int 3)