The magnetic field – or magnetosphere – is a giant invisible shield that protects the planet, repelling solar wind and other forms of space weather that could threaten life on Earth. It is essential for the running of our global navigation systems (and those of ants, sharks and other animals), not to mention our ability to survive on this planet in the first place.
The strength of our magnetosphere makes it unique among the rocky planets. While Mars lost its magnetic field sometime in the distance past, Mercury possesses a measly imitation. According to NASA, it is only 1 percent as strong as the one surrounding the Earth. In contrast, Jupiter harbours a whopper – only beaten by the Sun. The Gas Giant’s magnetic field spans a mindblowing 12 million miles, a length roughly equivalent to 15 Suns.
The source of the magnetic field lies in the outer core, a thick layer of extremely hot liquid composed predominantly of nickel and iron, located deep below the Earth’s surface. According to USGS, convective forces within the core create a perpetual state of churning that generates large, fast-moving currents of electricity that, in turn, produce a magnetic field.
This magnetic field extends into space, forming a defensive layer around the Earth that deflects solar particles (aka solar wind). But it is not 100 percent foolproof – hence the phenomenon of the aurora, which is the result of interactions between solar wind and the magnetosphere. Strong geomagnetic storms and fluctuations in the strength of the magnetic field itself can also lead to distrubances that trigger disruptions on the power grid and our navigation systems.
The magnetosphere is in constant flux, oscillating in strength but also shifting location. The planet has two magnetic poles, distinct from the better-known geographical poles that lie in the Arctic and Antarctica. NASA reports that since it was located in 1831 by the British Royal Navy officer and polar explorer Sir James Clark Ross, the magnetic north pole has moved north-northwest by more than 600 miles (1,100 kilometers) – and the rate at which it is moving appears to be increasing. According to NOAA, it is currently migrating in this direction at a rate of approximately 34 miles (55 kilometers) per year. The most recent readings suggest it is now closer to Siberia than it is to Canada.
But things at the poles can get even more dramatic. Every 300,000 years or so, the magnetic poles flip. According to NASA, the last time this occurred was some 780,000 years ago, so we are more than due another switch up. While scientists do not know when exactly this will happen, they do know that it is a process that takes hundreds to thousands of years to complete. So it is not a pressing concern.
