Over the 400 years or so that humans have been measuring Earth’s magnetic field, it has drifted inexorably to the west. Now, a new hypothesis suggests that weird waves in Earth’s outer core may cause this drift.  The slow waves, called Rossby waves, arise in rotating fluids. They’re also known as “planetary waves,” and they’re found in many large, rotating bodies, including on Earth in the oceans and atmosphere and on Jupiter and the sun. [6 Visions of Earth’s Core]

Earth’s outer core is also a rotating fluid, meaning Rossby waves circulate in the core, too. Whereas oceanic and atmospheric Rossby waves have crests that move westward against Earth’s eastward rotation, Rossby waves in the core are “a bit like turning atmospheric Rossby waves inside out,” said O.P. Bardsley, a doctoral student at the University of Cambridge in England, and the author of a new study on the Rossby wave hypothesis. Their crests always move east.  READ MORE