This fascinating article appeared the other day in SpaceWeather.com

Out of Nowhere, a Global Magnetic Anomaly
June 25, 2020 / Dr.Tony Phillips
Lately, Earth's magnetic field has been quiet. Very quiet. The sun is in the pits of what may turn out to be the deepest Solar Minimum in a century. Geomagnetic storms just aren’t happening.
"That's why I was so surprised on June 23rd when my instruments picked up a magnetic anomaly," reports Stuart Green, who operates a research-grade magnetometer in his backyard in Preston UK. "For more than 30 minutes, the local magnetic field oscillated like a sine wave."