The SAA is deepening and moving westwards.

  Table 4 shows the change in the SAA from 2025.0 to 2026.0 as estimated at Earth’s surface and at 500 km by WMM2025 and WMMHR2025.

  The area affected, as judged by the area inside the 25,000 nT contour at the Earth’s surface, has increased by about 8% over this time (for both WMM and WMMHR).

  This contour approximates the region where radiation damage to satellites is most likely to occur.

Page 13, State of the Geomagnetic Field, December 2025 (PDF 19 pages) https://news.ycombinator.com/item?id=46361359

How this was discovered is incredible. An amator satelite was lauched. operators collected data. At some point they had the idea to plot them. That gave a big stain in the south atlantic.