The Earth's magnetic field acts as a shield, protecting us from damaging cosmic rays and harsh solar winds. It's as important to our survival as water and oxygen, yet it's in a constant state of flux. New research presented this week at the Living Planet Symposium shows just how rapidly our magnetic field is changing.
Despite being invisible, these changes have significant impacts as evident by the noticeable shift in our planet's magnetic North Pole. Fluctuations like these in the magnetic field could determine how events such as solar storms affect us in the future.
Earth's magnetic field is getting weaker over some parts of the world, and strengthening over others. Thanks to new data from a recent ESA mission, scientists are getting their first in depth look at these changes and now think they know what causes them. Understanding the processes at work will help scientists better predict future changes.
We've known the magnetic field is changing for a while, but what is surprising is that the data the shows the magnetic field is weakening at a more rapid pace—approximately 10 times faster than previously predicted. Scientists estimate that the field loses 5 percent of its strength each year. Why this is happening and what it means for our planet remains to be seen.
One explanation could be that the Earth's magnetic poles are getting ready to flip. When we think of north and south, we picture them as being fairly constant, but the Earth's magnetic field has flipped many times throughout our planet's history, with the last reversal happening during the Stone Age.
The Earth's magnetic field is a dipole, meaning it has two opposite poles—just like a magnet. The magnetic field typically maintains the same intensity for thousands to million of years, but occasionally (once every 100,000 years or so) it weakens and reverses directions. This sounds like a scary process, but scientists assure us there's no need to be alarmed.
To better understand our magnetic field, ESA launched a mission called Swarm in 2013. This trio of satellites orbits the Earth, mapping the magnetic signals from different regions of the planet such as the mantle, core, crust, oceans, ionosphere and magnetosphere.
After analyzing the data, scientists have produced a detailed map that shows where the magnetic field is strengthening and weakening, how quickly these changes are happening and what is causing them.
Data shows that since 1999, our magnetic field has weakened by about 3.5 percent over North America, but has simultaneously strengthened by roughly 2 percent over Asia during the same time period.
The weakest part of the magnetic field, located over South America, has steadily migrated westward over the past seven years, weakening by as much as 2 percent. Simultaneously, the North Pole is moving east towards Asia at a fairly rapid pace.
So what is causing these changes? Researchers believe that our magnetic field is generated by an ocean of molten iron that makes up our planet's outer core. The liquid metal sloshes and churns below the crust, generating electrical currents that power the magnetic field.
Swarm is the first mission to map changes in the planet's core and the magnetic field surrounding it. How each of these signals interacts with the others is key.
"Swarm data are now enabling us to map detailed changes in Earth's magnetic field, not just at Earth's surface but also down at the edge of its source region in the core," said Chris Finlay, ESA project lead. "Unexpectedly, we are finding rapid localised field changes that seem to be a result of accelerations of liquid metal flowing within the core."
The Swarm mission is already providing major insight into the Earth's magnetic heartbeat. Future data is expected to broaden our understanding of our magnetic field and how it interacts with the space environment.