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Unravelling Earth's magnetic field

ESA's Swarm satellites are seeing fine details in one of the most difficult layers of Earth's magnetic field to unpick - as well as our planet's magnetic history imprinted on Earth's crust.
Earth's magnetic field can be thought of as a huge cocoon, protecting us from cosmic radiation and charged particles that bombard our planet in solar wind. Without it, life as we know it would not exist.

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Magnetic oceans and electric Earth

Oceans might not be thought of as magnetic, but they make a tiny contribution to our planet's protective magnetic shield. Remarkably, ESA's Swarm satellites have not only measured this extremely faint field, but have also led to new discoveries about the electrical nature of inner Earth.
When salty ocean water flows through the magnetic field, an electric current is generated and this, in turn, induces a magnetic response in the deep region below Earth's crust - the mantle. Because this response is such a small portion of the overall field, it was always going to be a challenge to measure it from space.

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Ancient crystals show Earth's magnetic field switched on early

Earth's magnetic field powered up early. The finding, gleaned from field lines frozen into zircon crystals up to 4.2 billion years old, offers a glimpse at our planet's infancy - and may hint at how the Earth was able to hold on to its life-sustaining atmosphere.
Looking back so far in time is not easy. In its 4.5 billion year history, our planet's surface has changed constantly, and the early pages of Earth's story remain frustratingly blank. "It's like you have chapters 19 and 20 of a 20-chapter book," says James Head of Brown University in Providence, Rhode Island, who was not involved in the study.

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Title: Detecting the oldest geodynamo and attendant shielding from the solar wind: Implications for habitability
Author: John A. Tarduno, Eric G. Blackman, Eric E. Mamajek

The onset and nature of the earliest geomagnetic field is important for understanding the evolution of the core, atmosphere and life on Earth. A record of the early geodynamo is preserved in ancient silicate crystals containing minute magnetic inclusions. These data indicate the presence of a geodynamo during the Paleoarchean, between 3.4 and 3.45 billion years ago. While the magnetic field sheltered Earth's atmosphere from erosion at this time, standoff of the solar wind was greatly reduced, and similar to that during modern extreme solar storms. These conditions suggest that intense radiation from the young Sun may have modified the atmosphere of the young Earth by promoting loss of volatiles, including water. Such effects would have been more pronounced if the field were absent or very weak prior to 3.45 billion years ago, as suggested by some models of lower mantle evolution. The frontier is thus trying to obtain geomagnetic field records that are >>3.45 billion-years-old, as well as constraining solar wind pressure for these times. In this review we suggest pathways for constraining these parameters and the attendant history of Earth's deep interior, hydrosphere and atmosphere. In particular, we discuss new estimates for solar wind pressure for the first 700 million years of Earth history, the competing effects of magnetic shielding versus solar ion collection, and bounds on the detection level of a geodynamo imposed by the presence of external fields. We also discuss the prospects for constraining Hadean-Paleoarchean magnetic field strength using paleointensity analyses of zircons.

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Missing link in metal physics explains Earth's magnetic field

Earth's magnetic field is crucial for our existence, as it shields the life on our planet's surface from deadly cosmic rays. It is generated by turbulent motions of liquid iron in Earth's core. Iron is a metal, which means it can easily conduct a flow of electrons that makes up an electric current. New findings from a team including Carnegie's Ronald Cohen and Peng Zhang shows that a missing piece of the traditional theory explaining why metals become less conductive when they are heated was needed to complete the puzzle that explains this field-generating process. Their work is published in Nature.
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Swarm reveals Earth's ever-changing magnetic field

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MIT scientists identify a plasma plume that naturally protects the Earth against solar storms.

Scientists at MIT and NASA have identified a process in the Earth's magnetosphere that reinforces its shielding effect, keeping incoming solar energy at bay.
By combining observations from the ground and in space, the team observed a plume of low-energy plasma particles that essentially hitches a ride along magnetic field lines - streaming from Earth's lower atmosphere up to the point, tens of thousands of kilometers above the surface, where the planet's magnetic field connects with that of the sun. In this region, which the scientists call the "merging point," the presence of cold, dense plasma slows magnetic reconnection, blunting the sun's effects on Earth.

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Maori stones hold magnetic clues

Scientists are studying the Earth's magnetic field using the stones that line Maori steam ovens.
The cooking process generates so much heat that the magnetic minerals in these stones will realign themselves with the current field direction.
An archaeological search is under way in New Zealand to find sites containing old ovens, or hangi as they are known.
Abandoned stones at these locations could shed light on Earth's magnetic behaviour going back hundreds of years.

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 Hidden Magnetic Portals Around Earth



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Earth's magnetic field provides vital protection

A chance alignment of planets during a passing gust of the solar wind has allowed scientists to compare the protective effects of Earth's magnetic field with that of Mars' naked atmosphere. The result is clear: Earth's magnetic field is vital for keeping our atmosphere in place.
The alignment took place on 6 January 2008. Using ESA's Cluster and Mars Express missions to provide data from Earth and Mars, respectively, scientists compared the loss of oxygen from the two planets' atmospheres as the same stream of solar wind hit them. This allowed a direct evaluation of the effectiveness of Earth's magnetic field in protecting our atmosphere.

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