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article imageESA's Swarm satellites probe weakening of Earth's magnetic shield

By Karen Graham     May 20, 2020 in Science
In an area stretching from Africa to South America, Earth’s magnetic field is gradually weakening. This strange behavior (the South Atlantic Anomaly) has geophysicists puzzled and is causing technical disturbances in satellites orbiting Earth.
Up until the 1990s, scientists have known that the Earth's magnetic north was drifting at a rate of up to about 9 miles (15 kilometers) a year. Now, however, the drift of Earth’s magnetic north pole has turned into “more of a sprint,” scientists say. Its present speed is about 30 to nearly 40 miles a year (50-60 km a year) toward Siberia.
In October 2017, the magnetic north pole crossed the International Dateline, passing within 390 km [242 miles] of the geographic pole, and is now heading south, according to EarthSky.org.
The European Space Agency (ESA) released an article on May 14, 2020, that describes a new study in the peer-reviewed journal Nature Geoscience that discusses the theory of “tussling magnetic blobs deep below Earth’s surface” as the root cause of the phenomenon of rapid magnetic pole drift since the 1990s.
Tussling magnetic blobs deep below Earth’s surface appear to be at the root of the phenomenon of r...
Tussling magnetic blobs deep below Earth’s surface appear to be at the root of the phenomenon of rapid magnetic pole drift since the 1990s.
ESA
And in the technology-orientated world we live in today, it is not just compasses that are affected by the drift of Earth’s magnetic north pole. And while the South Atlantic Anomaly presents no cause for alarm, satellites and other spacecraft are more likely to experience technical malfunctions as the magnetic field is weaker in this region.
This means charged particles are able to penetrate the altitudes of low-Earth orbit satellites. Jürgen Matzka, from the German Research Centre for Geosciences, says, "We are very lucky to have the Swarm satellites in orbit to investigate the development of the South Atlantic Anomaly. The challenge now is to understand the processes in Earth’s core driving these changes.”
Using the Swarm to find answers
The ESA’s Living Planet Symposium last year featured a talk from scientists at the University of Leeds in the U.K. about their findings on magnetic north, using SWARM satellite data.
The ESA's Swarm constellation consists of three identical satellites for Earth observation. All three have a rather unusual configuration, being trapezoidal with a long boom that was deployed once they are in orbit. The shape was created while overcoming the challenges in accommodating the instrument package.
The primary objectives of the Swarm mission were as follows:
1. studies of core dynamics, geodynamo processes, and core-mantle interaction
2. mapping of the lithospheric magnetization and its geological interpretation
3. determination of the 3D electrical conductivity of the mantle
4. investigation of electric currents flowing in the magnetosphere and ionosphere
There were two additional objectives that included identifying the ocean circulation by its magnetic signature and quantifying the magnetic forcing of the upper atmosphere.
A change in the circulation pattern of magnetic blobs
The scientists found that a change in the flow underneath Canada has caused a patch of the magnetic field at the edge of Earth’s core, deep within the Earth, to be stretched out. This has weakened the Canadian patch and resulted in the pole shifting towards Siberia.
Studying the South Atlantic Anomaly, scientists found the minimum field strength in this area has dropped from around 24 000 nanoteslas to 22 000, while at the same time the area of the anomaly has grown and moved westward at a pace of around 20 km per year.
Over the past five years, a second center of minimum intensity has emerged southwest of Africa – indicating that the South Atlantic Anomaly could split up into two separate cells. Does this mean there will be a pole reversal - in which the north and south magnetic poles switch places?
We are long overdue for one. They usually happen every 250,000 years or so. However, according to the study, the intensity dip in the South Atlantic occurring now is well within what is considered normal levels of fluctuations.
More about Magnetic field, European space agency, Swarm Constellation, Geophysics, magnetosphere
 
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