"These are among the smallest signals detected by the ...Swarm mission... so far."
The European Space Agency's Swarm constellation can detect tiny changes in Earth's magnetic field.....
The observations were made by the European Space Agency's (ESA) Swarm constellation, which consists of three satellites circling the planet in low Earth orbit at altitudes between 287 and 318 miles (462 to 511 kilometers).
The Swarm satellites, launched in 2013, carry sensitive magnetometers that can spot tiny variations in Earth's magnetic field caused by the tidal movements of the ocean. Earth's magnetic field is produced by the motion of molten iron in the planet's core. It extends tens of thousands of miles into space, shielding the planet from harmful cosmic radiation and bursts of charged particles from the sun.
https://www.space.com/the-universe/earth/european-swarm-satellites-detect-electric-currents-from-the-oceans-tides
European 'Swarm' satellites detect electric currents from the ocean's tides | Space
Satellites have detected electromagnetic signals generated by ocean tides, suggesting that space-born sensors could obtain insights into the motion of other liquid masses on Earth.
https://www.space.com/the-universe/earth/european-swarm-satellites-detect-electric-currents-from-the-oceans-tides
