ESA : Unravelling Earth’s magnetic field .- Desentrañar el campo magnético de la Tierra

http://www.esa.int/Our_Activities/Observing_the_Earth/Swarm/Unravelling_Earth_s_magnetic_field
                

Lithospheric magnetic field

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explained Nils Olsen from the Technical University of Denmark, one of the scientists behind the new map.

Unravelling Earth’s magnetic field

21 March 2017 A vuelo

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.

Most of the field is generated at depths greater than 3000 km by the movement of molten iron in the outer core. The remaining 6% is partly due to electrical currents in space surrounding Earth, and partly due to magnetised rocks in the upper lithosphere – the rigid outer part of Earth, consisting of the crust and upper mantle.

Although this ‘lithospheric magnetic field’ is very weak and therefore difficult to detect from space, the Swarm trio is able to map its magnetic signals. After three years of collecting data, the highest resolution map of this field from space to date has been released.

“By combining Swarm measurements with historical data from the German CHAMP satellite, and using a new modelling technique, it was possible to extract the tiny magnetic signals of crustal magnetisation,”

 

Magnetic anomaly: Bangui

 

ESA’s Swarm mission manager, Rune Floberghagen, added: “Understanding the crust of our home planet is no easy feat. We can’t simply drill through it to measure its structure, composition and history.

“Measurements from space have great value as they offer a sharp global view on the magnetic structure of our planet’s rigid outer shell.”

Presented at this week’s Swarm Science Meeting in Canada, the new map shows detailed variations in this field more precisely than previous satellite-based reconstructions, caused by geological structures in Earth’s crust.

One of these anomalies occurs in Central African Republic, centred around the city of Bangui, where the magnetic field is significantly sharper and stronger. The cause for this anomaly is still unknown, but some scientists speculate that it may be the result of a meteorite impact more than 540 million years ago.

The magnetic field is in a permanent state of flux. Magnetic north wanders, and every few hundred thousand years the polarity flips so that a compass would point south instead of north.

When new crust is generated through volcanic activity, mainly along the ocean floor, iron-rich minerals in the solidifying magma are oriented towards magnetic north, thus capturing a ‘snapshot’ of the magnetic field in the state it was in when the rocks cooled.

Since magnetic poles flip back and forth over time, the solidified minerals form ‘stripes’ on the seafloor and provide a record of Earth’s magnetic history.

 

Swarm

 

The latest map from Swarm gives us an unprecedented global view of the magnetic stripes associated with plate tectonics reflected in the mid-oceanic ridges in the oceans.

“These magnetic stripes are evidence of pole reversals and analysing the magnetic imprints of the ocean floor allows the reconstruction of past core field changes. They also help to investigate tectonic plate motions,” said Dhananjay Ravat from the University of Kentucky in the USA.

“The new map defines magnetic field features down to about 250 km and will help investigate geology and temperatures in Earth’s lithosphere.” 

ESA
Guillermo Gonzalo Sánchez Achutegui
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ESA : Magnetic oceans and electric Earth .- Océanos Magnéticos de La Tierra................

http://www.esa.int/Our_Activities/Observing_the_Earth/Swarm/Magnetic_oceans_and_electric_Earth

 

Swarm reveals Earth’s changing magnetism19 June 2014 The first set of high-resolution results from ESA’s three-satellite Swarm constellation reveals the most recent changes in the magnetic field that protects our planet.

 

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Magnetic signal from ocean tides

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3 October 2016 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.

The magnetic field shields us from cosmic radiation and charged particles that bombard Earth from the Sun. Without it, the atmosphere as we know it would not exist, rendering life virtually impossible.

Scientists need to learn more about our protective field to understand many natural processes, from those occurring deep inside the planet, to weather in space caused by solar activity. This information will then yield a better understanding of why Earth’s magnetic field is weakening.

Although we know that the magnetic field originates in different parts of Earth and that each source generates magnetism of different strengths, exactly how it is generated and why it changes is not fully understood.

 

Earth's protective shield

 

This is why, in 2013, ESA launched its trio of Swarm satellites.

While the mission is already shedding new light on how the field is changing, this latest result focuses on the most elusive source of magnetism: ocean tides.

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.

Last year, scientists from the Swiss Federal Institute of Technology, ETH Zurich, showed that if it could be measured from space – never done before – it should also tell us something about Earth’s interior. However, this all remained a theory – until now.

Thanks to Swarm’s precise measurements along with those from Champ – a mission that ended in 2010 after measuring Earth’s gravity and magnetic fields for more than 10 years – scientists have not only been able to find the magnetic field generated by ocean tides but, remarkably, they have used this new information to image the electrical nature of Earth’s upper mantle 250 km below the ocean floor.

 

Magnetic field sources

 

Alexander Grayver, from ETH Zurich, said, “The Swarm and Champ satellites have allowed us to distinguish between the rigid ocean ‘lithosphere’ and the more pliable ‘asthenosphere’ underneath.”

The lithosphere is the rigid outer part of the earth, consisting of the crust and upper mantle, while the asthenosphere lies just below the lithosphere and is hotter and more fluid than the lithosphere.

“Effectively, ‘geo-electric sounding from space’, this result is a first for space exploration,” he continues.

“These new results are important for understanding plate tectonics, the theory of which argues that Earth’s lithosphere consists of rigid plates that glide on the hotter and less rigid asthenosphere that serves as a lubricant, enabling plate motion.”

Roger Haagmans, ESA’s Swarm mission scientist, explained, “It’s astonishing that the team has been able to use just two years’ worth of measurements from Swarm to determine the magnetic tidal effect from the ocean and to see how conductivity changes in the lithosphere and upper mantle.

 

Swarm constellation over Earth

 

“Their work shows that down to about 350 km below the surface, the degree to which material conducts electric currents is related to composition.

“In addition, their analysis shows a clear dependence on the tectonic setting of the ocean plate. These new results also indicate that, in the future, we could get a full 3D view of conductivity below the ocean.”

Rune Floberghagen, ESA’s Swarm mission manager, added, “We have very few ways of probing deep into the structure of our planet, but Swarm is making extremely valuable contributions to understanding Earth’s interior, which then adds to our knowledge of how Earth works as a whole system.”

The research paper was published in Science Advances on 30 September.

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ESA
Guillermo Gonzalo Sánchez Achutegui
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NASA : Coronal Loops Over a Sunspot Group .- Lazos coronales sobre un grupo de manchas solares

Hola amigos: A VUELO DE UN QUINDE EL BLOG., hemos recibido información de la Agencia Espacial NASA, sobre los instrumentos que lleva el observatorio NASA's Solar Dynamics Observatory (SDO, siendo uno de ellos llamado : The Atmospheric Imaging Assembly (AIA); que permite captar imágenes de la atmósfera solar en múltiples longitudes de onda, para vincular los cambios en la superficie a los cambios anteriores. Su datos incluyen imágenes del sol en 10 longitudes de onda cada 10 segundos. Cuando las imágenes de AFP se agudizan un poco, como esta imagen del canal AIA 171Å, el campo magnético puede visualizarse fácilmente a través de los hilos brillantes y delgadas que son llamados "arcos coronales".Los Arcos (LAZOS) se muestran aquí en una superposición de mezclado con el campo magnético medido con Imager Heliosísmicas y Magnético de SDO debajo. Azul y amarillo representan las polaridades opuestas del campo magnético. Las imágenes combinadas fueron tomadas el 24 de octubre de 2014, a 23:50:37 UT.

More information...........
http://www.nasa.gov/image-feature/coronal-loops-over-a-sunspot-group

The Atmospheric Imaging Assembly (AIA) instrument aboard NASA's Solar Dynamics Observatory (SDO) images the solar atmosphere in multiple wavelengths to link changes in the surface to interior changes. Its data includes images of the sun in 10 wavelengths every 10 seconds. When AIA images are sharpened a bit, such as this AIA 171Å channel image, the magnetic field can be readily visualized through the bright, thin strands that are called "coronal loops". Loops are shown here in a blended overlay with the magnetic field as measured with SDO's Helioseismic and Magnetic Imager underneath. Blue and yellow represent the opposite polarities of the magnetic field. The combined images were taken on Oct. 24, 2014, at 23:50:37 UT.

Image Credit: NASA SDO

Last Updated: May 24, 2015

Editor: Sarah Loff

Tags:  Image of the Day, SDO (Solar Dynamics Observatory), Solar System, Sun

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Guillermo Gonzalo Sánchez Achutegui
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nsf.gov - News - Animal Magnetism: First Evidence That Magnetism Helps Salmon Find Home

Salmon appear to seek the magnetic signature of their home river during their spawning migration.
 

The proportion of salmon using the northern versus southern passage to the Fraser River in British Columbia, Canada, could be largely predicted by the magnetic fields of these passages; the closer the magnetic field at a passage entrance matched the field at the river mouth years before when the fish originally swam through it, the more fish used the passage.
Credit: Nathan Putman, Oregon State University

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When sockeye salmon migrate from salt water to fresh water, they change color--going from their ocean colors of mostly silver with some darker coloration on their backs (like a lot of other ocean fish) to red when in fresh water.

Credit: Dr. Tom Quinn, University of Washington

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Sockeye salmon weigh on average 8 pounds, and may reach 3 feet in length.
Credit: Dr. Tom Quinn, University of Washington
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Amazing Salmon Migrations
Credit and Larger Version

February 7, 2013

View a video of Nathan Putnam, a post-doctoral researcher at Oregon State University, who is working to solve some of the mysteries of salmon migrations.

When migrating, sockeye salmon typically swim up to 4,000 miles into the ocean and then, years later, navigate back to the upstream reaches of the rivers in which they were born to spawn their young. Scientists, the fishing community and lay people have long wondered how salmon find their way to their home rivers over such epic distances.

How do they do that?

A new study, published in this week's issue of Current Biology and partly funded by the National Science Foundation, suggests that salmon find their home rivers by sensing the rivers' unique magnetic signature.

As part of the study, the research team used data from more than 56 years of catches in salmon fisheries to identify the routes that salmon had taken from their most northerly destinations, which were probably near Alaska or the Aleutian Islands in the Pacific Ocean, to the mouth of their home river--the Fraser River in British Columbia, Canada. This data was compared to the intensity of the Earth's magnetic field at pivotal locations in the salmon's migratory route.

The Earth has a magnetic field that weakens with proximity to the equator and distance from the poles and gradually changes on a yearly basis. Therefore, the intensity of the magnetosphere in any particular location is unique and differs slightly from year to year.

Because Vancouver Island is located directly in front of the Fraser River's mouth, it blocks direct access to the river's mouth from the Pacific Ocean. However, salmon may slip behind Vancouver Island and reach the river's mouth from the north via the Queen Charlotte Strait or from the south via the Juan De Fuca Strait.

Results from this study showed that the intensity of the magnetic field largely predicted which route the salmon used to detour around Vancouver Island; in any given year, the salmon were more likely to take whichever route had a magnetic signature that most closely matched that of the Fraser River years before, when the salmon initially swam from the river into the Pacific Ocean.

"These results are consistent with the idea that juvenile salmon imprint on (i.e. learn and remember) the magnetic signature of their home river, and then seek that same magnetic signature during their spawning migration," said Nathan Putman, a post-doctoral researcher at Oregon State University and the lead author of the study.

Important results

It has long been known that some animals use the Earth's magnetic field to generally orient themselves and to follow a straight course. However, scientists have never before documented an animal's ability to "learn" the magnetic field rather than to simply inherit information about it or to use the magnetic field to find a specific location.

This study provides the first empirical evidence of magnetic imprinting in animals and represents the discovery of a major new phenomenon in behavioral biology.

In addition, this study suggests that it would be possible to forecast salmon movements using geomagnetic models--a development that has important implications for fisheries management.

Get out the map

Putman says scientists don't know exactly how early and how often salmon check the Earth's magnetic field in order to identify their geographic locations during their trip back home. "But," he says, "for the salmon to be able to go from some location out in the middle of the Pacific 4,000 miles away, they need to make a correct migratory choice early--and they need to know which direction to start going in. For that, they would presumably use the magnetic field."

Putman continues, "As the salmon travel that route, ocean currents and other forces might blow them off course. So they would probably need to check their magnetic position several times during this migration to stay on track. Once they get close to the coastline, they would need to hone in on their target, and so would presumably check in more continuously during this stage of their migration."

Putman says that once the salmon reach their home river, they probably use their sense of smell to find the particular tributary in which they were born. However, over long distances, magnetism would be a more useful cue to salmon than odors because magnetism--unlike odors--can be detected across thousands of miles of open ocean.

A long, strange trip

Like other Pacific Salmon, sockeye salmon spawn in the gravel beds of rivers and streams. After the newly hatched salmon emerge from these beds, they spend one to three years in fresh water, and then they migrate downstream to the ocean.

Next, the salmon travel thousands of miles from their home river to forage in the North Pacific for about two more years, and then, as well-fed adults, they migrate back to the same gravel beds in which they were born.

When migrating, salmon must transition from fresh water to sea water, and then back again. During each transition, the salmon undergo a metamorphosis that Putman says is almost as dramatic as the metamorphosis of a caterpillar into a butterfly. Each such salmon metamorphosis involves a replacement of gill tissues that enables the fish to maintain the correct salt balance in its environment: the salmon retains salt when in fresh water and pumps out excess salt when in salt water.

Salmon usually undertake their taxing, round-trip migration, which may total up to 8,000 miles, only once in their lives; they typically die soon after spawning.

For more information about this study, see Oregon State University's press release.

-NSF-

Media Contacts Lily Whiteman, National Science Foundation (703) 292-8310 lwhitema@nsf.gov
Mark Floyd, Oregon State University (541) 737-0788 mark.floyd@oregonstate.edu

Program Contacts Michelle Elekonich, National Science Foundation (703) 292-7202 melekoni@nsf.gov

Principal Investigators Nathan Putman, Oregon State University (205) 218-5276 nathan.putman@oregonstate.edu

Related WebsitesArticle about the use of magnetism by sea turtles: http://www.livescience.com/21080-loggerhead-turtle-migration.html
Press release about discovery that sea turtles use magnetism to steer when migrating around the Atlantic basin: http://www.nsf.gov/news/news_summ.jsp?cntn_id=124190

The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering. In fiscal year (FY) 2012, its budget is $7.0 billion. NSF funds reach all 50 states through grants to nearly 2,000 colleges, universities and other institutions. Each year, NSF receives over 50,000 competitive requests for funding, and makes about 11,000 new funding awards. NSF also awards nearly $420 million in professional and service contracts yearly.

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NASA - NASA Voyager 1 Probe Encounters New Region in Deep Space

PASADENA, Calif. -- NASA's Voyager 1 spacecraft has entered a new region at the far reaches of our solar system that scientists feel is the final area the spacecraft has to cross before reaching interstellar space.

Scientists refer to this new region as a magnetic highway for charged particles because our sun's magnetic field lines are connected to interstellar magnetic field lines. This connection allows lower-energy charged particles that originate from inside our heliosphere -- or the bubble of charged particles the sun blows around itself -- to zoom out and allows higher-energy particles from outside to stream in. Before entering this region, the charged particles bounced around in all directions, as if trapped on local roads inside the heliosphere.

The Voyager team infers this region is still inside our solar bubble because the direction of the magnetic field lines has not changed. The direction of these magnetic field lines is predicted to change when Voyager breaks through to interstellar space. The new results were described at the American Geophysical Union meeting in San Francisco on Monday.

"Although Voyager 1 still is inside the sun's environment, we now can taste what it's like on the outside because the particles are zipping in and out on this magnetic highway," said Edward Stone, Voyager project scientist based at the California Institute of Technology, Pasadena. "We believe this is the last leg of our journey to interstellar space. Our best guess is it's likely just a few months to a couple years away. The new region isn't what we expected, but we've come to expect the unexpected from Voyager."

Since December 2004, when Voyager 1 crossed a point in space called the termination shock, the spacecraft has been exploring the heliosphere's outer layer, called the heliosheath. In this region, the stream of charged particles from the sun, known as the solar wind, abruptly slowed down from supersonic speeds and became turbulent. Voyager 1's environment was consistent for about five and a half years. The spacecraft then detected that the outward speed of the solar wind slowed to zero.

The intensity of the magnetic field also began to increase at that time.

Voyager data from two onboard instruments that measure charged particles showed the spacecraft first entered this magnetic highway region on July 28, 2012. The region ebbed away and flowed toward Voyager 1 several times. The spacecraft entered the region again Aug. 25 and the environment has been stable since.

"If we were judging by the charged particle data alone, I would have thought we were outside the heliosphere," said Stamatios Krimigis, principal investigator of the low-energy charged particle instrument, based at the Johns Hopkins Applied Physics Laboratory, Laurel, Md. "But we need to look at what all the instruments are telling us and only time will tell whether our interpretations about this frontier are correct."

Spacecraft data revealed the magnetic field became stronger each time Voyager entered the highway region; however, the direction of the magnetic field lines did not change.

"We are in a magnetic region unlike any we've been in before -- about 10 times more intense than before the termination shock -- but the magnetic field data show no indication we're in interstellar space," said Leonard Burlaga, a Voyager magnetometer team member based at NASA's Goddard Space Flight Center in Greenbelt, Md. "The magnetic field data turned out to be the key to pinpointing when we crossed the termination shock. And we expect these data will tell us when we first reach interstellar space."

Voyager 1 and 2 were launched 16 days apart in 1977. At least one of the spacecraft has visited Jupiter, Saturn, Uranus and Neptune. Voyager 1 is the most distant human-made object, about 11 billion miles (18 billion kilometers) away from the sun. The signal from Voyager 1 takes approximately 17 hours to travel to Earth. Voyager 2, the longest continuously operated spacecraft, is about 9 billion miles (15 billion kilometers) away from our sun. While Voyager 2 has seen changes similar to those seen by Voyager 1, the changes are much more gradual. Scientists do not think Voyager 2 has reached the magnetic highway.

The Voyager spacecraft were built and continue to be operated by NASA's Jet Propulsion Laboratory, in Pasadena, Calif. Caltech manages JPL for NASA. The Voyager missions are a part of NASA's Heliophysics System Observatory, sponsored by the Heliophysics Division of the Science Mission Directorate at NASA Headquarters in Washington.

For more information about the Voyager spacecraft, 

visit: http://www.nasa.gov/voyager 

and http://voyager.jpl.nasa.gov .

 

 

Jia-Rui C. Cook 818-354-0850
Jet Propulsion Laboratory, Pasadena, Calif.
jccook@jpl.nasa.gov

Dwayne Brown 202-358-1726
NASA Headquarters, Washington
dwayne.c.brown@nasa.gov

 This still image and set of animations show NASA's Voyager 1 spacecraft exploring a new region in our solar system called the "magnetic highway." Image credit: NASA/JPL-Caltech › Full image and caption       › Image gallery

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Voyager 1 Explores the 'Magnetic Highway'

This still image and set of animations show NASA's Voyager 1 spacecraft exploring a new region in our solar system called the "magnetic highway." In this region, the sun's magnetic field lines are connected to interstellar magnetic field lines, allowing particles from inside the heliosphere to zip away and particles from interstellar space to zoom in.

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Before Voyager 1 reached the magnetic highway, charged particles bounced around in all directions, as if trapped on local roads inside the heliosphere, as shown in the first scene. The pink particles are the lower-energy charged particles that originate from inside the heliosphere, which is the bubble of charged ions surrounding our sun. The second scene shows Voyager entering the highway region, where inside (pink) particles zip away and particles from interstellar space (blue) stream in. These interstellar particles are called cosmic ray particles and have more energy than the inside particles. In the third scene, further travel through the magnetic highway means that all of the inside particles are leaving and the population of outside particles is much higher. The cosmic ray particles rapidly fill this new region to the same level as outside and speed in all directions. The fourth scene shows the point at which all of the inside particles have zipped out, leaving an area dominated by cosmic rays from outside.

These animations are based on data from Voyager 1's cosmic ray instrument. These particles are invisible to the human eye and less populous, but are visualized here in exaggerated populations.

Image credit: NASA/JPL-Caltech

 
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The Sun's Southern Wind Flows Northward

This artist's concept shows how NASA's Voyager 1 spacecraft is bathed in solar wind from the southern hemisphere flowing northward. This phenomenon creates a layer just inside the outer boundary of the heliosphere, the giant bubble of solar ions surrounding the sun. If the outside pressure were symmetrical, the streams from the sun's northern hemisphere above the plane of the planets would all turn northward and the streams from the southern hemisphere would all turn southward.

However, the interstellar magnetic field presses more strongly on the boundary in the southern hemisphere, forcing some of the solar wind from the south that otherwise would have gone southward to be deflected northward to where Voyager 1 is. On July 21, 2012, the magnetometer instrument indicated that Voyager 1 had entered a region where the wind is from the southern hemisphere. Scientists interpret this to mean that the spacecraft is in the final region before reaching interstellar space because the southern wind streams have to flow out and around all of the northern wind to reach Voyager 1's location.

Image credit: NASA/JPL-Caltech

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