The European Space Agency (ESA) has a trio of satellites known as SWARM that studies Earth’s magnetic field.
“Launched in 2013, the trio of Swarm satellites are measuring and untangling the different magnetic fields that stem from Earth’s core, mantle, crust, oceans, ionosphere and magnetosphere. ” – ESA
The main source of Earth’s magnetic field is swirling liquid iron flows in the outer core. These iron flows create electrical currents which cause the changing magnetic field on the surface of the earth.
The most interesting 2016 result from SWARM is the finding that there is a strong liquid iron flow in the outer core below the arctic circle and the speed of this particular stream is accelerating. The results were published in a paper titled “An accelerating high-latitude jet in Earth’s core” in Nature Geoscience. Here’s the abstract of that paper:
“Observations of the change in Earth’s magnetic field—the secular variation—provide information about the motion of liquid metal within the core that is responsible for the magnetic field’s generation. High-resolution observations from the European Space Agency’s Swarm satellite mission show intense field change at high latitude, localized in a distinctive circular daisy-chain configuration centred on the north geographic pole. Here we show that this feature can be explained by a localized, non-axisymmetric, westward jet of 420 km width on the tangent cylinder, the cylinder of fluid within the core that is aligned with the rotation axis and tangent to the solid inner core. We find that the jet has increased in magnitude by a factor of three over the period 2000–2016 to about 40 km yr−1, and is now much stronger than typical large-scale flows inferred for the core. We suggest that the current accelerating phase may be part of a longer-term fluctuation of the jet causing both eastward and westward movement of magnetic features over historical periods, and may contribute to recent changes in torsional-wave activity and the rotation direction of the inner core.”
Note the last sentence in this paper’s abstract: “recent changes in torsional-wave activity and the rotation direction of the inner core.” Some of you may remember my speculations about a possible “true polar wander” or TPW due to a coupling between the geodynamo and the mantle. In those older posts I expressed this as:
“We do not understand the details of the geodynamics of this magnetic pole drift. One possibility, however, is that the rotational north pole and the magnetic north pole will be aligned due to coupling created by the geodynamics.”
Well..it seems that the scientists understand the geodynamics much better now. But, they are not saying anything about the possible coupling between the core and the mantle yet. They are not making any comment on whether the change in the rotation direction of the inner core can cause TPW by affecting the mantle. Let’s revisit this in the future when we have more data from the SWARM.
I have reported on SWARM’s earlier findings in my posts titled “European Space Agency’s Magnetic Field Mission SWARM” and “Recent changes in Earth’s magnetic field“. The picture below is from 2014. The red dots show the average position of the north magnetic pole. The SWARM team did not update the picture but confirmed that the drift towards Siberia is continuing.
Earth’s magnetic field strength has been weakening in the last 2000 years. The trend accelerated in the past decades. SWARM satellites have been launched at the end of 2013. In 2014, SWARM team reported that the Earth’s magnetic field has weakened 10 times faster in the Western hemisphere in the first 6 months of 2014. They updated the numbers in 2016.
Since the SWARM measurements started in the beginning of 2014 the Earth’s magnetic field strength has changed as follows:
“It shows clearly that the field has weakened by about 3.5% at high latitudes over North America, while it has strengthened about 2% over Asia. The region where the field is at its weakest – the South Atlantic Anomaly – has moved steadily westward and weakened further by about 2%. — In addition, the magnetic north pole is wandering east, towards Asia.” – SWARM team
ESA says it’ll take several more years for SWARM to measure and untangle the different magnetic signals from Earth’s core, mantle, crust, oceans, ionosphere and magnetosphere.
There is web page that contains a lot of information about SWARM.