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How Earth’s magnetic field is changing

Data from a trio of satellites show rapid local changes in Earth’s magnetic field. The cause is likely accelerations in the flow of liquid iron near Earth’s core.

Earth's magnetic field protects our planet from unhealthy solar radiation. Image via ESA.

Earth’s magnetic field protects our planet from unhealthy solar radiation. Image via ESA.

Earth’s continuously changing magnetic field is thought to be largely generated by superheated, swirling liquid iron in Earth’s outer core. Other sources of earthly magnetism include minerals in our world’s mantle and crust. Earth’s ionosphere, magnetosphere and oceans also play a role. The European Space Agency (ESA) now has two years of data from a trio of satellites in Earth-orbit, designed to measure magnetism from these various sources. The mission is called Swarm. At last week’s Living Planet Symposium held in Prague in the Czech Republic (May 9-13, 2016), scientists presented new results from the Swarm satellite trio and provided some recent insights about how Earth’s magnetic field is changing at this time.

Among other things, they said that the field has weakened by about 3.5% at high latitudes over North America, while it has grown about 2% stronger over Asia. The region where the field is at its weakest field – the South Atlantic Anomaly – has moved steadily westward and further weakened by about 2%.

Meanwhile, the magnetic north pole has been wandering east, towards Asia.

The animation below is based partly on results from ESA’s Swarm mission, and partly on information from the CHAMP and Ørsted satellites.

It shows how the strength of Earth’s magnetic field changed between 1999 and mid-2016.

Blue depicts where the field is weak and red shows regions where the field is strong. As you can see, the changes in field strength are relatively small.

Now check out the next animation, below. It shows the rate of change in Earth’s magnetic field between 2000 and 2015, and it shows what scientists called “rapid localized field changes.”

Regions where changes in the field slowed are shown in blue. Red shows where changes have sped up. So you can see, for example, that changes in the field have slowed near South Africa, but have changed faster over Asia.

Chris Finlay, senior scientist at DTU Space in Denmark, remarked in a statement:

Swarm data are now enabling us to map detailed changes in Earth’s magnetic field, not just at Earth’s surface but also down at the edge of its source region in the core.

Unexpectedly, we are finding rapid localized field changes that seem to be a result of accelerations of liquid metal flowing within the core.

ESA described Earth’s magnetic field as:

… a huge bubble, protecting us from cosmic radiation and charged particles that bombard Earth the solar wind.

The magnetic field is thought to be produced largely by an ocean of molten, swirling liquid iron that makes up our planet’s outer core, 3000 km under our feet. Acting like the spinning conductor in a bicycle dynamo, it generates electrical currents and thus the continuously changing electromagnetic field.

It is thought that accelerations in field strength are related to changes in how this liquid iron flows and oscillates in the outer core.

Without this protective shield, the atmosphere as we know it would not exist, rendering life on Earth virtually impossible.

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.

The magnetic field is thought to be largely generated by an ocean of superheated, swirling liquid iron that makes up Earth’s the outer core 3000 km under our feet. Acting like the spinning conductor in a bicycle dynamo, it generates electrical currents and thus the continuously changing electromagnetic field. Other sources of magnetism come from minerals in Earth’s mantle and crust, while the ionosphere, magnetosphere and oceans also play a role. ESA’s constellation of three Swarm satellites is designed to identify and measure precisely these different magnetic signals. This will lead to new insight into many natural processes, from those occurring deep inside the planet, to weather in space caused by solar activity.

Artist’s concept of ESA’s constellation of three Swarm satellites. They are designed to identify and measure the various magnetic signals from Earth. ESA says data from the satellites will lead to new insights into many natural processes, from those occurring deep inside the planet, to weather in space caused by solar activity. Image via ESA.

Bottom line: ESA’s Swarm satellite trio has been busy measuring and untangling Earth’s different magnetic signals in order to gauge our world’s magnetic heartbeat. Scientists presented recent results at the Living Planet Symposium in Prague.

Via ESA

Deborah Byrd

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