Credit: CLAUS LUNAU/GettyRossby Waves Affect Our Magnetic Field
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, as we now know, on the Sun.
Earth's outer core is thought of as 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. This is a little odd because Rossby waves in the core have eastward-moving crests, quite opposite the westward-moving drift. But crests of waves don't always represent their total energy movement.
So Rossby waves with a large-scale tendency to move energy westward could explain the westward drift of the earth’s magnetic field measured over the Atlantic Ocean. The small-scale details, like those eastward-moving crests, would be impossible to detect.
The westward drift and the Rossby wave hypothesis are largely unrelated to a more famous question regarding the magnetic field: Is it going to flip? Periodically throughout Earth's history, magnetic north and magnetic south have swapped places. This isn't particularly problematic because it is thought to take a while, and the process causes an uptick in anomalies and a weakening of the magnetic field in between the poles.
A weakened field can let more solar particles through, which can disrupt electric grids and cause problems with navigational systems. However, scientists aren't certain whether the weakening of the magnetic field over the past century or two is a sign of an impending flip-flop or merely a recoverable wobble.