Cassie Kelly | Space Science | March 22, 2017
Earth’s magnetic field affects the planet’s climate, tectonic shifts, gravity, and even its rotation. However, its most important function is deflecting harsh solar radiation and particles that could upend our very existence here. Up until now, technology wasn’t advanced enough to allow scientists to fully map the magnetic field, but, thanks to the European Space Agency’s Swarm mission, they finally have a more complete understanding.
The Swarm satellites are three spacecraft launched into Earth’s orbit — two in low elevation, one in high — in 2013 to survey the magnetic field, better understand the planet’s evolution, and measure the electric field in the atmosphere. After three years of collecting data, scientists were able to create the highest resolution map of the magnetic field to date.
“We had a very high volume of data and good coverage of Earth’s lower elevation,” Dhananjay Ravat, a geophysicist at the University of Kentucky who helped ESA complete the map, tells Inverse. “We took a different approach and also used data from the lower altitude CHAMP satellite, which helped us to achieve 250 km wavelength in resolution, which was not possible before.”
With the map, scientists can essentially peer 1,800 miles into Earth’s molten iron outer core, which generates the magnetic field and sends currents to magnetized rocks in the upper lithosphere — the rocky surface we dwell on.
The findings show that the magnetic field isn’t evenly distributed across the planet. In some places, there are higher deposits of iron and nickel, both highly magnetized elements. For example, in the Central African Republic, the field is sharper and stronger than anywhere else on the planet, possibly because of a meteorite that hit Earth 540 million years ago.
“The meteorite could have been made of iron and nickel and those fragments could have impacted the planet making it highly magnetized in that area,” explains Ravat.
Another interesting aspect of the map is that it shows the stripes on the sea floor. Those stripes are believed to be caused by shifts in the magnetic field. About every 700,000 years, the poles reverse, meaning the pointer on your compass would face south when it used to face north. This theory is evident in the stripes, which, as Ravat explains, are caused by rock formations that grow in the direction of the magnetic field and shift when the field shifts.
“These stripes are symmetric with the mid-oceanic ridge and can really only be seen from high altitudes or some satellites,” Ravat says. “They tell us about how the Earth’s magnetic field behaved in the past, that is why this map is so important, it’s a continuous record of 200 million years.”
The next step for the scientists is to collect data during the solar minimum, a time when the 11-year solar cycle is at its least active. Ravat says during this time there will be less radiation from the sun, and the satellites will be able to generate even higher quality maps.