Since 2001, the gap has been widening at the rate of 65 kilometers (40.6 miles) per year, compared with just 10 kilometers (six miles) per year in estimates in the early 1990s. In addition, the magnetic field has been weakening. Since the mid-19th century it has lost around 15 percent of its…
Since 2001, the gap has been widening at the rate of 65 kilometers (40.6 miles) per year, compared with just 10 kilometers (six miles) per year in estimates in the early 1990s. In addition, the magnetic field has been weakening. Since the mid-19th century it has lost around 15 percent of its strength.
Earth’s magnetism derives from super-heated liquid iron and nickel, which swirl in the outer core about 3,000 kilometers (1,800 miles) beneath the surface. Like a spinning dynamo, this subterranean metal ocean generates electrical currents and thus a magnetic field.
The well-known gap between Earth’s magnetic north pole and its geographical north is growing. “Earth’s magnetic field is a very important thing. It makes life possible on Earth by providing shelter against radiation from space,” said Albert Zaglauer, project manager at Astrium, which made the three satellites.
Some experts wonder if this is a prelude to something really big – a reversal of magnetic polarity. Polarity switches occur around every 200,000 to 300,000 years, according to telltale magnetic signatures found in ancient sediments.
Reversals are believed to occur when iron atoms in lava spewed by volcanoes adopt a polarity and retain it after the rock has solidified. Eventually a planetary tipping point is reached. Earth is overdue for the next event and we are witnessing the precursors now.
Magnetism not only comes from deep within the Earth, but also above in the ionosphere (between 85 and 600 kilometers or 53 and 375 miles above the Earth) and the magnetosphere, about 60,000 to 120,000 kilometers (37,500 to 75,000 miles) beyond.
Scattered across South America and the South Atlantic are locations where it is weak — so much so that the lack of a shield against radiation is already affecting electronics on a low-altitude satellite.
“The magnetic field is a very complex phenomenon which changes in time and space,” said Mioara Mandea of France’s National Center of Space Studies (CNRS). “We have identified various sources but, at a given point on the surface, they all get mixed together.”
Three satellites in the Swarm constellation are due to lift off on Friday from Russia’s Plesetsk Cosmodrome aboard a Rocket launcher. The aim is to capture magnetic fields and discerning its content and spectrum.
Their long, sleek design gives them a slight look of a “Star Wars” fighter.
Each 470-kilo (1,034-pound) craft is due to operate at extremely low altitudes — two will fly initially at 460 kilometers (287 miles), reduced after four years to just 300 kilometers (180 miles) — where there are lingering molecules of atmosphere. The third will start at 530 kilometers (331 miles) to offer a different angle of view.
The satellites will each extend a four-meter (13-foot) boom on the end of which are perched instruments to measure the geomagnetic field’s strength, orientation and fluctuations.
The arm is designed to isolate the instruments as much as possible from the magnetic “noise” from the satellite’s own operational equipment — the battery, communications unit and so on.
“The biggest challenge was to deliver a product that can measure the magnetic field to extremely fine detail,” said Zaglauer.
“We have to measure (magnetic forces) in the order to 50,000 nano-teslas to within an accuracy of one nanotesla. This is unique.”
What emerges could not only unlock fundamental knowledge about the magnetic field, but also improve navigational accuracy on Earth as well as improve satellite design, he said.