A trio of European satellites have just completed a very detailed map of this enigmatic field. The spacecraft are triplets that go by the group name of "Swarm," and they were launched by the European Space Agency (ESA) in 2013 to map out the planet's magnetic fields.
Researchers are now using the Swarm's data and the digital three-dimensional map to get a better understanding of how this magnetic field is created by the tides, its general behavior, and how it shifts as time passes by. (Related: If the Earth’s magnetic field reverses, scientists think they know where ground zero will be.)
The Earth's magnetic field derives its protective power from the planet's molten core, the rocks that make up the crust and upper mantle, and the oceans. This protective field keeps out the solar wind, rapidly moving streams of energetic particles cast out by the sun.
If unchecked by a magnetic field, the solar wind would be disrupting every electrical and electronic device on the planet in scenes straight out of a global disaster movie. Human health would also suffer due to the massive increase in radiation levels, warned Phil Livermore and John Mound of the University of Leeds.
The magnetic field of the oceans is small, but it can tug on the planet's bigger field
Swarm mapped the oceans' magnetic field in order to broaden our understanding of one of the mysterious forces protecting our planet. The researchers picked the oceans for a number of reasons, particularly because the role they play in the process is small yet vital.
Seawater contains salt, a mineral that can serve as an electrical conductor. Furthermore, oceans don't sit still like solid rock, and they flow much faster than molten rock.
The salty waters of the world follow a cyclical movement, moving up and down several times a day. As these tides course through the oceans, the constantly moving water tugs on the magnetic field surrounding our planet, which can be detected by Swarm.
"We have used Swarm to measure the magnetic signals of tides from the ocean surface to the seabed, which gives us a truly global picture of how the ocean flows at all depths — and this is new," stated Nils Olsen of the Technical University of Denmark (DTU).
Compared to the massive sheath around our planet, the magnetic field attributed to the ocean is much smaller. Olsen explained that it is 20,000 times weaker, measuring only 2-2.5 nanotesla at the altitudes occupied by the Swarm satellites.
Tidal magnetic field affects the lithosphere's magnetic properties
Interestingly, even as the tidally generated magnetic field tugs on the Earth's bigger barrier like a toddler would do to a parent's hand, it also causes a faint magnetic reaction from a source well beneath the seabed. This electrical signal is coming from the lithosphere, the rigid outer part of the planet comprised of the crust and upper mantle.
The electrical properties of the lithosphere have attracted the attention of researchers. In 2017, they used data from the Swarm satellites to make a magnetic map of the region.
The fact that the oceans' weak magnetic field is capable of affecting the lithosphere's own magnetism could indirectly help researchers learn more about the crust and mantle.
You can read about other breakthroughs in our growing understanding of our planet's processes at Scientific.news.
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