Tag Archives: magnetic field

Scientists may have found how migrating birds sense Earth’s magnetic field

Birds migrate thousands of miles without a GPS, using the Earth’s magnetic field to orient themselves. It’s been a long mystery how they were able to do this, but now, scientists may have found the key reason behind it: a molecule in the eye that’s sensitive to magnetism and gives birds a working internal compass. 

Image credit: Flickr / Piplongstockings

Quantum birds

A group of biologists, chemists, and physicists tested a 40-years old theory according to which a light-sensitive molecule interacts with the Earth’s magnetic field via a quantum chemical process. To do this, they looked at a light-sensitive protein called cryptochrome 4 (CRY4) from the retina of European robins (Erithacus rubecula).

“We think we may have identified the molecule that allows small migratory songbirds to detect the direction of the Earth’s magnetic field, which they undoubtedly can do, and use that information to help them navigate when they migrate thousands of kilometres,” Peter Hore, researcher and co-author of the paper, told BBC News.

European robins live throughout Europe, Russia and western Siberia. Some migrate south every northern hemisphere winter, for example from Scandinavia to the United Kingdom, and return in spring. Many migrating robins are faithful to both their summer and winter territories, which may be many hundreds of kilometers apart.

Previous studies have shown that certain species of birds use Earth’s magnetic fields when they migrate. Suspicion had fallen on the CRY4, a light-sensitive protein, and the first one identified in animals that evolved specifically to detect magnetic fields. It’s part of a class of proteins known as cryptochromes, involved in the workings of circadian rhythms.  

Now, researchers managed to isolate the molecule from robins and showed that it is sensitive to magnetic fields. In the presence of light, electrons can jump between different parts of CRY4 and between it and another molecule called flavin adenine dinucleotide (FAD), ultimately leading to the production of a compound called CRY4-FADH. 

Changes in the level of the compound may allow light-sensitive cells in the eye to alter their output, making the view lighter or darker, depending on the direction and strength of the magnetic field in the bird’s field of vision, Henrik Mouritsen, co-author, told New Scientist. “You may be able to see where north is as kind of a shading on whatever else you would be seeing,” he said. 

For comparison, the researchers also looked at CRY4 proteins from chickens and pigeons, which are not migratory birds, but do contain this light-sensitive protein. Each species has a slightly different version of the molecule, and the team found that these two are less affected by magnetism. This suggests that the version of the molecule in migratory birds has been fine-tuned to amplify its sensitivity.

While the findings are exciting, the study hasn’t demonstrated that CRY4 is being used for magnetic sensing in real life. The researchers only looked at this molecule in isolation. Nevertheless, the fact that the molecule is more magnetically-sensitive in robins than in birds such as chickens that don’t migrate makes them optimistic about their findings. 

The study was published in the journal Nature. 

The Event Horizon Telescope (EHT) collaboration, who produced the first ever image of a black hole released in 2019, has today a new view of the massive object at the centre of the Messier 87 (M87) galaxy: how it looks in polarised light. This is the first time astronomers have been able to measure polarisation, a signature of magnetic fields, this close to the edge of a black hole. (EHT Collaboration)

Black Hole Seen Clearly in Historic New Direct Image

Using the Event Horizon Telescope (EHT) to observe the supermassive black hole at the centre of the galaxy Messier 87 (M87), astronomers have once again produced another first in the field of astronomy and cosmology.

Following up on the image of M87’s black hole published two years ago–the first time a black hole was imaged directly–astronomers at the EHT collaboration have captured a stunning image of the same black hole, this time in polarized light.

The achievement marks more than just an impressively sharp and clear second image of this black hole however–it also represents that first-time researchers have been able to capture the polarization of light around such an object.

Not only does this reveal details of the magnetic field that surrounds the supermassive black hole, but it also could give cosmologists the key to explaining how energetic jets launch from the core of this distant galaxy.

The Event Horizon Telescope (EHT) collaboration, who produced the first ever image of a black hole released in 2019, has today a new view of the massive object at the centre of the Messier 87 (M87) galaxy: how it looks in polarised light. This is the first time astronomers have been able to measure polarisation, a signature of magnetic fields, this close to the edge of a black hole. (EHT Collaboration)
The Event Horizon Telescope (EHT) collaboration, which produced the first-ever image of a black hole released in 2019, has today a new view of the massive object at the centre of the Messier 87 (M87) galaxy: how it looks in polarised light. This is the first time astronomers have been able to measure polarisation, a signature of magnetic fields, this close to the edge of a black hole.  This image shows the polarised view of the black hole in M87. The lines mark the orientation of polarisation, which is related to the magnetic field around the shadow of the black hole. (EHT Collaboration)

“M87 is a truly special object!  It is tied for the largest black hole in the sky with the black hole in our galaxy–Sagittarius A*, ” Geoffrey C. Bower, EHT Project Scientist and assistant research astronomer at the Academia Sinica Institute of Astronomy and Astrophysics, tells ZME Science. “It’s about one thousand times further away but also one thousand times more massive.

“The M87 black hole’s home is in the centre of the Virgo Cluster, the nearest massive cluster of galaxies, each with its own black hole. This makes it a great laboratory for studying the growth of galaxies and black holes.”

Geoffrey C. Bower, Academia Sinica Institute of Astronomy and Astrophysics.

Along with Monika Mościbrodzka, Coordinator of the EHT Polarimetry Working Group and Assistant Professor at Radboud University, Netherlands, Bower is one of the authors on two papers detailing the breakthrough published in the latest edition of The Astrophysical Journal Letters.

Messier 87 (M87) is an enormous elliptical galaxy located about 55 million light years from Earth, visible in the constellation Virgo. It was discovered by Charles Messier in 1781, but not identified as a galaxy until 20th Century. At double the mass of our own galaxy, the Milky Way, and containing as many as ten times more stars, it is amongst the largest galaxies in the local universe. Besides its raw size, M87 has some very unique characteristics. For example, it contains an unusually high number of globular clusters: while our Milky Way contains under 200, M87 has about 12,000, which some scientists theorise it collected from its smaller neighbours. Just as with all other large galaxies, M87 has a supermassive black hole at its centre. The mass of the black hole at the centre of a galaxy is related to the mass of the galaxy overall, so it shouldn’t be surprising that M87’s black hole is one of the most massive known. The black hole also may explain one of the galaxy’s most energetic features: a relativistic jet of matter being ejected at nearly the speed of light. The black hole was the object of paradigm-shifting observations by the Event Horizon Telescope. The EHT chose the object as the target of its observations for two reasons. While the EHT’s resolution is incredible, even it has its limits. As more massive black holes are also larger in diameter, M87's central black hole presented an unusually large target—meaning that it could be imaged more easily than smaller black holes closer by. The other reason for choosing it, however, was decidedly more Earthly. M87 appears fairly close to the celestial equator when viewed from our planet, making it visible in most of the Northern and Southern Hemispheres. This maximised the number of telescopes in the EHT that could observe it, increasing the resolution of the final image. This image was captured by FORS2 on ESO’s Very Large Telescope as part of the Cosmic Gems programme, an outreach initiative that (ESO)
Messier 87 (M87) is an enormous elliptical galaxy located about 55 million light-years from Earth, visible in the constellation Virgo and home of the black hole imaged by the EHT team (ESO)

“We are now seeing the next crucial piece of evidence to understand how magnetic fields behave around black holes, and how activity in this very compact region of space can drive powerful jets that extend far beyond the galaxy,” says Mościbrodzka.

“We have never see magnetic fields directly so close to the event horizon,” the astronomer tells ZME Science.

“We now, for the first time, have information on how magnetic field lines are oriented close to the event horizon and how strong these magnetic fields are. All this information is new.”

Deeper Into the Heart of M87

The release of the first image of a black hole on the 10th of April 2019 marked a milestone event in science, and ever since then, the team behind that image has worked hard to delve deeper into M87’s black hole. This second image is the culmination of this quest. The observation of the polarized light allows us to better understand the information in that prior image and the physics of black holes.

This composite image shows three views of the central region of the Messier 87 (M87) galaxy in polarised light. The galaxy has a supermassive black hole at its centre and is famous for its jets, that extend far beyond the galaxy.  One of the polarised-light images, obtained with the Chile-based Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner, shows part of the jet in polarised light. This image captures the part of the jet, with a size of 6000 light years, closer to the centre of the galaxy. The other polarised light images zoom in closer to the supermassive black hole: the middle view covers a region about one light year in size and was obtained with the National Radio Astronomy Observatory’s Very Long Baseline Array (VLBA) in the US.  The most zoomed-in view was obtained by linking eight telescopes around the world to create a virtual Earth-sized telescope, the Event Horizon Telescope or EHT. This allows astronomers to see very close to the supermassive black hole, into the region where the jets are launched.  The lines mark the orientation of polarisation, which is related to the magnetic field in the regions imaged.The ALMA data provides a description of the magnetic field structure along the jet. Therefore the combined information from the EHT and ALMA allows astronomers to investigate the role of magnetic fields from the vicinity of the event horizon (as probed with the EHT on light-day scales) to far beyond the M87 galaxy along its powerful jets (as probed with ALMA on scales of thousand of light-years). The values in GHz refer to the frequencies of light at which the different observations were made. The horizontal lines show the scale (in light years) of each of the individual images. (EHT Collaboration)
This composite image shows three views of the central region of the Messier 87 (M87) galaxy in polarised light. The galaxy has a supermassive black hole at its centre and is famous for its jets, that extend far beyond the galaxy.  (EHT Collaboration)

“Light is an electromagnetic wave which has amplitude and direction of oscillation or polarization,” explains Mościbrodzka. “With the EHT we observed that light in the M87’s surrounding ring is polarized meaning that waves oscillation have a preferred direction.”

This polarization is a property of synchrotron radiation that is produced in the vicinity of this black hole. Polarization occurs when light passes through a filter–think of polarized sunglasses blocking out light and thus giving you a clearer view–thus the polarization of light in this picture accounts for this clearer view of M87’s black hole, which reveals a great deal of information about the black hole itself.

“The polarization of the synchrotron light tells us about the orientation of magnetic fields. So by measuring light polarization we can map out the magnetic fields around the black hole.”

Monika Mościbrodzka, Coordinator of the EHT Polarimetry Working Group and Assistant Professor, Radboud University

Capturing such an image of polarized light at a distance of 55 million light-years is no mean feat, and is only possible with the eight linked telescopes across the globe that comprise the EHT. Together these telescopes–including the 66 antennas of the Atacama Large Millimeter/submillimeter Array (ALMA)–form a virtual telescope that is as large as the Earth itself with a resolution equivalent to reading a business card on the Moon.

This image shows the contribution of ALMA and APEX to the EHT. The left hand image shows a reconstruction of the black hole image using the full array of the Event Horizon Telescope (including ALMA and APEX); the right-hand image shows what the reconstruction would look like without data from ALMA and APEX. The difference clearly shows the crucial role that ALMA and APEX played in the observations. (EHT Collaboration)
This image shows the contribution of ALMA and APEX to the EHT. The left hand image shows a reconstruction of the black hole image using the full array of the Event Horizon Telescope (including ALMA and APEX); the right-hand image shows what the reconstruction would look like without data from ALMA and APEX. The difference clearly shows the crucial role that ALMA and APEX played in the observations. (EHT Collaboration)

“As a virtual telescope that is effectively as large as our planet the EHT has a resolution power than no other telescope has,” says Mościbrodzka. “The EHT is observing the edge of what is known to humans, the edge of space and time. And for the second time, it has allowed us to bring to the public the images of this black hole.”

This image–as the above comparison shows– has had its clarity enhanced immensely by calibration with data provided by the Atacama Pathfinder EXperiment (APEX).

Of course, these magnetic fields are responsible for much more than just giving us a crystal clear image of the black hole they surround. They also govern many of the physical processes that make black holes such powerful and fascinating events–including one of M87’s most mysterious features.

How Magnetic Fields Help Black Holes ‘Feed’

The M87 galaxy–55 million light years from Earth– is notable for its powerful astrophysical jets that blast out of its core and extend for 5000 light-years. Researchers believe that these jets are caused when some of the matter at the edge of the black hole escapes consumption.

Whilst other matter falls to the surface of the central black hole and disappears to the central singularity, this escaping matter is launched into space as these remarkable jets.

This artist’s impression depicts the black hole at the heart of the enormous elliptical galaxy Messier 87 (M87). This black hole was chosen as the object of paradigm-shifting observations by the Event Horizon Telescope. The superheated material surrounding the black hole is shown, as is the relativistic jet launched by M87’s black hole. 9ESO/M. Kornmesser)
This artist’s impression depicts the black hole at the heart of the enormous elliptical galaxy Messier 87 (M87). This black hole was chosen as the object of paradigm-shifting observations by the Event Horizon Telescope. The superheated material surrounding the black hole is shown, as is the relativistic jet launched by M87’s black hole. 9ESO/M. Kornmesser)

Even though this is a more than plausible explanation, many questions still remain about the process, namely, how an area that is no bigger than our solar system creates jets that are greater in length than the entire galaxy that surrounds it.

This image of the polarized light around M87’s black hole which offers a glimpse into this inner region finally gives scientists a chance to answer these mysteries.

“Our planet’s magnetosphere prevents ionized particles emitted by the Sun from reaching the Earth’s surface.  In the same way, strong black hole magnetic fields can prevent or slow down the accretion of matter onto the black hole,” Bowers says. “Those strong magnetic fields are also powerful for generating the jets of particles that flow at near the speed of light away from the black hole.”

By mitigating the feeding process of their central black holes, however, these magnetic fields may have an influence that like the jets they create may extend even further than M87 itself. They could be affecting the entire galactic cluster.

“Magnetic fields can play a very important role in how black holes ‘eat.’  If the fields are strong enough, they can prevent inflowing material from reaching the black hole.  They are also important in funnelling matter out into the relativistic jets that burst from the black hole region.  These jets are so powerful that they influence gas dynamics amongst the entire cluster of galaxies surrounding M87.”

Geoffrey C. Bower, Academia Sinica Institute of Astronomy and Astrophysics.

This means a better understanding of the magnetic fields around M87’s black hole also gives researchers an improved understanding of how the matter behaves at the edge of that black hole and perhaps of how such things affect neighbouring galaxies and their evolution.

And from the image of M87’s black hole the EHT team have developed, it looks clear that of the various models that cosmologists have developed to describe the interaction of matter at the edge of black holes, only those featuring strongly magnetized gases can account for its observed features.

“We have now a better idea about the physical process in the ring visible in the image,” Mościbrodzka says. “We now know more precisely how strong magnetic fields can be near a black hole. We also know more accurately at what rate the black hole is swallowing matter. And we have a better idea of what the black hole might look like in the future.”

We’ve come a long way: on the left the first image of the M87 black hole, released in 2019. On the right this new much sharper image. (EHT)

In terms of what is next for black hole imaging, both Mościbrodzka and Bowers are clear; they have their sights set on a black hole that is closer to home than M87–the one that sits at the centre of the Milky Way, which despite being closer to home, could be a tougher nut to crack in terms of imaging.

“We’re hard at work on a problem that we know everyone wants to see; an image of the black hole at the centre of our galaxy,” says Bowers. “This is really tricky because the gas around the black hole moves so fast that the image may be changing on same the time scale that it takes to snap our picture. We think we know how to handle this problem but it requires a lot of technical innovation.”

Given the advancements already made by the EHT collaboration team, it would be unwise to bet against them achieving this lofty goal at some point in the not too distant future.

“We’ve gone from imagining what happens around black holes to actually imaging it!” Bowers concludes. “In the near future, we’ll be able to show a movie of material orbiting the black hole and getting ejected into a jet. I never thought I would see anything like this.

“Black holes are the simplest but most enigmatic objects in the Universe.  These observations are just the beginning of the road to understanding them.”

Geoffrey C. Bower, Academia Sinica Institute of Astronomy and Astrophysics.

When Earth’s magnetic field flipped 42,000 years, the climate changed too

A reversal in Earth’s magnetic field and a decline in solar activity 42,000 years ago caused major climate shifts that led to global environmental change and mass extinctions, according to a new study. The researchers called it the “Adams Event”after sci-fi writer Douglas Adams who declared the number 42 as the ultimate answer.

Kauri trees. Image credit: WIkipedia Commons

The Earth has a magnetic field that works as a protective shield against damaging electromagnetic radiation. But when the poles switch, as it has happened many times in the planet’s geological history, the shield weakens significantly and leaves the planet exposed to high-energy particles. The last time this happened was 42,000 years ago and lasted for about 1,000 years, during what scientists refer to as the Laschamp event.

Previous studies couldn’t find much evidence of the impact of the event on the planet, probably because the focus wasn’t on the period in which the poles were actually reversing, Turney and his team argue. Now, they discovered that the pole switch could have been the reason for a wide array of climate and environmental phenomena with severe consequences.

For the study, the researchers carried out radiocarbon analyses of the rings of ancient kauri trees located in northern New Zealand wetlands, some of which were more than 42,000 years old. This allowed tracking over time the increase of carbon-14 levels in the atmosphere, which is generated by the increasing levels of high-energy cosmic radiation reaching the Earth.

“For the first time ever, we have been able to precisely date the timing and environmental impacts of the last magnetic pole switch,” co-author Chris Turney from the University of New South Wales said in a statement. “The findings were made possible with ancient New Zealand kauri trees, which have been preserved in sediments for over 40,000 years.”

The researchers looked at numerous records and materials from all over the world, including from lake and ice cores, and found that a host of major environmental changes happened at the same time as the carbon-14 levels peaked. This included a shift in tropical rain belts in the West Pacific and a large growth of the ice sheet over North America, for example.

They used a model to understand how the chemistry of the atmosphere might change if the Earth’s magnetic field was lost and there was a prolonged period of low solar activity, which would have further reduced Earth’s protection against cosmic radiation. Ice core records suggest such drops in solar activity, known as the “grand solar minima”, coincided with the Laschamps event.

The atmospheric changes would have caused big environmental and climate changes, the researchers believe. This would have accelerated the growth of ice sheets and contributed to the extinction of Australian megafauna. Plus, it could explain the emergence of red ochre handprints, as humans might have used the pigment as a sunscreen to cope with the increased levels of ultraviolet radiation.

But that’s not all. The harsh climate conditions would explain the larger use of caves by our ancestors, as the underground spaces offered shelter. This would have increased competition and could have contributed to the end of the Neanderthals. “It’s the most surprising and important discovery I’ve ever been involved in,” Alan Cooper, lead author of the study, said in a statement.

While the last time the poles switched was 42,000 years ago, the researchers said there’s currently rapid movement of the north magnetic pole across the Northern Hemisphere. This could eventually lead to another reversal. The magnetic field has already weakened by about 9% over the past 170 years.

“Our atmosphere is already filled with carbon at levels never seen by humanity before. A magnetic pole reversal or extreme change in Sun activity would be unprecedented climate change accelerants,” Turney said in a statement. “We urgently need to get carbon emissions down before such a random event happens again.”

The study was published in the journal Science.

Electromagnetic fields could be used to manage, maybe even treat, type 2 diabetes

A new study reports that the symptoms of type 2 diabetes could be managed through a few hours’ worth of exposure to magnetic fields every day — in mice, at least.

Image credits Flickr / Tebo Steele.

Exposure to magnetic and static electric fields for a few hours can keep blood sugar levels in check without the need for medication or direct intervention, the paper explains. Type 2 diabetes is characterized by unsafe levels of sugars in the blood, and as such, the methods described in this study can help manage the condition.

For now, the findings have only been confirmed in lab mice, so we still don’t know if they hold true for humans as well. However, the team is hopeful that they do, which will provide us with a new, non-invasive means of managing the disease, especially for patients who are having trouble with current treatment options.


“We’ve built a remote control to manage diabetes,” says Calvin Carter, PhD, one of the study’s lead authors from the University of Iowa (UI) Carver College of Medicine.

“Exposure to electromagnetic fields (EMFs) for relatively short periods reduces blood sugar and normalizes the body’s response to insulin. The effects are long-lasting, opening the possibility of an EMF therapy that can be applied during sleep to manage diabetes all day.”

EMFs can alter the balance of oxidants and antioxidant compounds in the liver, the study showed, which can improve our body’s response to insulin (a sugar-regulating hormone). This response is likely mediated by molecules with electromagnetic properties that act as tiny “antennae”, the authors believe.

The findings were ‘a happy accident’, with the effect of EMFs on blood sugar levels discovered while Sunny Huang, the co-lead author on the paper, was analyzing their effect on the brain and behavior of mice. He noticed that all the animals exposed to EMFs showed normal blood sugar levels, despite being genetically-engineered to have type 2 diabetes. The team was quickly able to tie these abnormal readings to EMF exposure prior to the analysis.

Carter and Huang later developed a device that can wirelessly generate static magnetic and electric fields to see if it could modulate blood sugar levels in three of the genetically-modified mice — and it did. These fields are roughly 100 times stronger than those naturally generated by the Earth. Furthermore, mice who were exposed to these fields while they slept also saw their insulin resistance reversed in only three days of treatment.

The study helps us better understand how EMFs can interact with biological systems. Such fields are very common in today’s world, as they’re employed to transmit data wirelessly — for example in navigation or telecommunications.

The team explains that they found EMFs to interact with superoxide molecules in our bodies, but those in the liver specifically, leading to a heightened antioxidant response which in turn affects the effectiveness of insulin.

“When we remove superoxide molecules from the liver, we completely block the effect of the EMFs on blood sugar and on the insulin response. The evidence suggests that superoxide plays an important role in this process,” Carter adds.

The researchers also exposed human liver cells to EMFs for six hours and, through the use of an insulin surrogate marker, showed that they would likely produce similar anti-diabetic effects in human patients. The team is now working on a larger-scale test to see if EMFs would work the same in animals closer in size and physiology to humans.

The paper “Exposure to Static Magnetic and Electric Fields Treats Type 2 Diabetes” has been published in the journal Cell Metabolism.

Magnetic anomaly from 11 million years ago could help us understand how poles flip

We’re told as kids that a compass will always point north, but that’s not exactly true. A compass points to the North Magnetic Pole, not to the North Pole. The two are currently fairly close, so it’s a good approximation, but it’s not always like this.

The magnetic poles have flipped multiple times in history, approximately once every 300,000 years, though the period isn’t fixed. Researchers suspect a reversal may happen relatively soon. The last flip took place 780,000 years ago, and 41,000 years ago, the poles got significantly weaker, but never really flipped. Now, researchers studying a magnetic anomaly in the South Atlantic shed new light on this process.

The Earth is a big magnet

The Earth’s magnetic field is generated by the outer core. This outer core is fluid and consists mostly of iron and nickel, constantly moving and convecting, essentially acting like a dynamo that produces a magnetic field. In a sense, the Earth is just one big magnet.

We’re very lucky this happens: this magnetic field protects the earth by deflecting most of the solar wind. Without this protection, the solar wind would strip away most of the ozone layer, rendering our planet vulnerable to harmful radiation from the sun.

The Earth’s magnetic field isn’t uniform. Some areas have a stronger field, which offers extra protection, while some areas with a weaker field are somewhat vulnerable. A good example of the latter is a large and growing anomaly in the South Atlantic Ocean. The South Atlantic Anomaly has a magnetic field so weak that it’s as if you were flying in the ionosphere, hundreds of miles above the surface.

The South Atlantic Anomaly is a topic of interest for scientists, not just because they’re not sure how it came to be, but also because it poses real risks for space equipment. If it’s somehow connected to an upcoming pole reversal, it would be even more important to understand. But according to a new study, the anomaly has been there for a very long time — millions of years, in fact.

The new study suggests that the South Atlantic Anomaly isn’t a new phenomenon indicative of an upcoming pole reversal. Lead author of the paper, University of Liverpool Ph.D. student Yael Engbers, explains:

“Our study provides the first long term analysis of the magnetic field in this region dating back millions of years. It reveals that the anomaly in the magnetic field in the South Atlantic is not a one-off, similar anomalies existed eight to 11 million years ago.

“This is the first time that the irregular behaviour of the geomagnetic field in the South Atlantic region has been shown on such a long timescale. It suggests that the South Atlantic Anomaly is a recurring feature and probably not a sign of an impending reversal.

A map of the Earth showing the present-day deviation from expected magnetic field direction. Strong deviations are in yellow-orange, and little deviations are in blue. The star is Saint Helena, an island that is right in the anomaly. The grey line shows the outline of the seismic area that is warmer than the rest of the mantle. Credit: Dr. YAEL Engbers, University of Liverpool

Magnetic field, frozen in rocks

You might be wondering how we could possibly know what the magnetic field was like millions of years ago. The answer to this, and the question of how we know about magnetic pole reversal, lies “frozen” in rocks.

When volcanic or igneous rocks cool down, the minerals that form them slowly solidify. Minerals that are rich in iron and easily magnetized tend to align themselves on the magnetic poles. Like a compass, these minerals point to the direction of the magnetic North-South line — but only when they cool down. After they’ve solidified, they no longer change this alignment, they stick to the original. So if we date these rocks, we can know how this North-South line went. By analyzing how well these minerals aligned to the field, we can also deduce the strength of the magnetic field.

Using this information, geologists build time charts depicting the normal and reversed polarity, using black and white as below.

In this research, the team analyzed rocks from 34 different volcanic eruptions from Mount Saint Helena (not to be confused with St. Helens). These eruptions took place between 8 and 11 million years ago and highlight a similarly weak magnetic field in the area. In other words, the anomaly was still there 11 million years ago. Engbers says that this suggests no connection to an impending pole reversal, but this could help us better understand how the Earth’s field is produced by geological activity.

“It also supports earlier studies that hint towards a link between the South Atlantic Anomaly and anomalous seismic features in the lowermost mantle and the outer core. This brings us closer to linking behaviour of the geomagnetic field directly to features of the Earth’s interior”

The study has been published in PNAS.

Dogs can navigate using the Earth’s magnetic field

Dog navigation has been a black box for researchers. The way they find their way from place to place, often across great distances, has been a hard to crack mystery. Their keen sense of smell can sure help sometimes, but smell alone doesn’t explain how dogs can navigate over great distances.

In a new study, researchers describe one potential mechanism that helps dogs find their way: their internal compass.

Dogs in the study, enjoying the outdoors and finding their way back. Image credits: Benediktova et al.

The idea that dogs orient themselves using the Earth’s magnetic field is not new. Curiously, previous studies have shown that dogs tend to align themselves on the north-south axis when they poop or urinate. As funny as this sounds, it’s indicative of an intriguing underlying mechanism: somehow, dogs sense the Earth’s magnetic field, and align themselves to it under certain conditions.

So the next question is — can they use this for navigation?

To analyze this, PhD student Kateřina Benediktová from the Czech University of Life Sciences Prague carried out two experiments using 4 and 27 dogs, respectively, to see how they find their way.

Both experiments had the same format: Benediktova and colleagues attached GPS sensors to dogs, took them out to a natural environment, and let them run about. In all cases, dogs went and did their thing and then returned to their owner.

However, when researchers analyzed the path dogs took to return, a few interesting patterns emerged.

First of all, some of the dogs went and returned on the same path. This is where their exceptional sense of smell comes into play as it helps them find their way back. This type of behavior was called tracking, because dogs tracked their own path.

But in the second type of behavior, dogs left on one path and returned on another. This behavior is called scouting, because they scout a different path. Sometimes, the dogs used a combination of both.

Image credits: Benediktova et al.

It gets even more interesting: most of the scouting dogs also engaged in an odd behavior: they would sometimes run 20 meters on the north-south line, before returning to their starting point. The study authors believe this helped them find their bearings, much like a person would align the compass on north-south for easier orientation — and dogs that did it were more efficient in their return. In 170 of the 223 documented dog trips, dogs practiced this behavior.

It’s always hard to demonstrate whether animals are orienting themselves using magnetism alone. To be 100% sure of this, you’d basically have to make sure the animal isn’t using any of its other senses, which is not easy to do. However, the fact that such a similar behavior was observed in so many different dogs seems to be strong evidence, and it’s the closest you can get to a smoking gun. No other factors (such as wind, location, or the dog’s gender) seemed to make a difference in improving navigational efficiency, further supporting the idea that the dogs were able to use the Earth’s magnetic field to navigate.

If this is the case, it would probably indicate an old navigation method, from when dogs were still a wild species.

Many biologists believe that not just dogs, but all animals that range over long distances can orient themselves using the Earth’s magnetic field. It’s even suspected that humans can do it, but we’re not nearly as good at it as other species.

Honey bees have the ability to detect the Earth’s magnetic field using iron granules in their abdomen. Frogs, snails, and even some bacteria can do it, and this is still actively researched in a number of mammals, including mice and foxes. It’s pretty neat to see that dogs can do it too.

The study has been published in eLife.

Earth’s magnetic North Pole is now officially moving towards Siberia

Unlike the geographical poles, the planet’s magnetic poles are in constant motion, following the flow of Earth’s molten iron outer core, which moves and flows as the planet spins. That’s common knowledge for centuries now. In fact, sometimes the magnetic poles will even flip every couple hundred thousand years or so. What’s surprising, however, is the high rate at which the magnetic north pole is drifting toward the East, from the Canadian Arctic towards Russia.

How Earth’s magnetic north pole has drifted in recent decades. Credit: NOAA.

The planet’s outer core is composed of liquid iron which constantly moves as the planet’s interior gradually cools down. This motion creates electric currents as electrons move through the liquid and, in the process, the energy of the fluid is converted into a magnetic field. If we imagined that Earth’s magnetic field is similar to a bar magnet (or dipole), then we can locate a geomagnetic north and south pole. However, this is an oversimplification of the complexity and variation of Earth’s true magnetic field.

In the last couple of decades, scientists have noticed that the northern magnetic pole has been shifting away from the Canadian Arctic toward Siberia at an average rate of 55 kilometers (34 miles) per year. Most recently, it has slowed down to 40 kilometers (25 miles) per year, which is still significantly higher than the average recorded over the last century.

To keep up with the north magnetic pole’s motions, scientists have established the World Magnetic Model (WMM) in order to enable systems to provide accurate navigation and positioning.

The WMM is used by all sorts of applications from smartphones to the military. But although the WMM is also incorporated by things like Google Maps, regular folks shouldn’t worry too much since the north magnetic pole’s movements aren’t all that important for latitudes below 55 degrees.

The WMM is updated every five years, but researchers at the National Centers for Environmental Information — a collaboration between NOAA and the British Geological Survey — decided to hit the update button a year earlier in order to account for the faster than anticipated drifting of the north magnetic pole.

Current location of the Earth’s north magnetic pole. Credit: NOAA.

This week, 2020 World Magnetic Model was officially released, which forecasts where the magnetic pole is headed for the next 5 years until the next update. At the moment, researchers claim that the north magnetic pole has now officially crossed the prime meridian.

“Based on the WMM2020 coefficients for 2020.0 the geomagnetic north pole is at 72.68°W longitude and 80.65°N latitude, and the geomagnetic south pole is at 107.32°E longitude and 80.65°S latitude. The axis of the dipole is currently inclined at 9.41° to the Earth’s rotation axis. The WMM can also be used to calculate dip pole positions. These model dip poles are computed from all the Gauss coefficients using an iterative method. In 2020.0 the north dip pole computed from WMM2020 is located at longitude 164.04°E and latitude 86.50°N and the south dip pole at longitude 135.88°E and latitude 64.07°S,” NOAA researchers wrote.

Over the last 150 years, the magnetic pole has crept north over 1,000 kilometers. It’s not clear why this acceleration is occurring due to gaps in our knowledge of how the planet’s core behaves. One leading hypothesis suggests that liquid molten iron under Canada is being dragged toward Siberia. In the meantime, the magnetic South Pole has barely moved, which is another mystery.

Credit: MaxPexel.

Unbelievable experiment suggests humans are able to subconsciously sense Earth’s magnetic field

Credit: MaxPexel.

Credit: MaxPexel.

The ability to sense Earth’s magnetic field is essential for many animals that use the magnetic field as a sort of a heads-up display to help them navigate the globe. But do humans also have this capacity? Seems so, claim the researchers of a new study which found that at least some humans have a magnetic ‘sixth sense’, albeit on a subconscious level.

The vestigial compass inside our heads

Hundreds of miles beneath our feet, floating molten liquid is churning away, driving the planet’s magnetic field like a huge electromagnet. The magnetic field serves to deflect most of the solar wind, whose charged particles would otherwise strip away the ozone layer that protects the Earth from harmful ultraviolet radiation. The magnetic field is also what causes a compass to point north. Interestingly, some creatures have an internal compass that enables them to “see” the magnetic field — an ability called magnetoreception.

So far, researchers have identified this ability in quite a number of animals, both vertebrate and invertebrates, from fish and turtle to cows, even bacteria. One of the oddest examples of magnetoreception is dogs, who apparently always poop while facing either north or south.

In 2018, researchers found that European robins (Erithacus rubecula) and zebra finches (Taeniopygia guttata) both have a protein in their eyes’ retina, aptly called CRY4, which specifically evolved to detect magnetic fields.  Humans do not have this protein inside their eyes but other studies have suggested that some animals are capable of magnetoreception as a result of complex neurological processes. This intrigued Caltech geophysicist Joseph Kirschvink and neuroscientist Shin Shimojo who embarked on a new study which solely focused on studying brain waves alone.

For their study, 34 participants had their brain’s electrical activity recorded with electroencephalography (EEG) while they seated inside a custom-built chamber fitted with coils and wires. The researchers varied the current which ran through the wires, with it varying the magnetic field inside the enclosure. The ‘Faraday Cage’ also insulated the participants seated inside from any external magnetic fields.

Illustration of the Faraday Cage used in the present experiment. Credit: Bickel.

Illustration of the Faraday Cage used in the present experiment. Credit: Bickel.

During tests, each lasting for an hour each, the magnetic fields were rotated repeatedly while the participants sat inside the chamber in total darkness. When the magnetic field in the chamber was shifted, the participants could not experience any subjective experience of the fact. The EEG data, on the hand, showed that certain magnetic field rotations produced a strong and reproducible brain response. One of the EEG patterns recorded during the magnetic field shifts, called alpha-ERD, typically shows when an individual detects and processes a sensory stimulus.

“The brains were “concerned” with the unexpected change in the magnetic field direction, and this triggered the alpha-wave reduction. That we saw such alpha-ERD patterns in response to simple magnetic rotations is powerful evidence for human magnetoreception,” the authors wrote.

“Our participants’ brains only responded when the vertical component of the field was pointing downwards at about 60 degrees (while horizontally rotating), as it does naturally here in Pasadena, California. They did not respond to unnatural directions of the magnetic field – such as when it pointed upwards.”

“We suggest the response is tuned to natural stimuli, reflecting a biological mechanism that has been shaped by natural selection.”

For decades researchers have been testing humans’ ability to detect magnetic fields with conflicting results. The authors of the new study highlight how birds stop guiding themselves after the geomagnetic field if the strength is more than 25% different from what they’re used to. This tendency might also happen in humans, which may explain why previous efforts to detect magnetoreception came out empty handed — by cranking up the magnetic field to enable subjects to clearly detect it, the practice would only ensure the subjects’ brain ignored it.

The authors believe that this subconscious ability in humans, as in other species, is due to magnetoreceptor cells which contain the ferromagnetic mineral magnetite. In the future, the researchers plan on studying the biophysics of the process in greater detail. They would also like to bring magnetoreception into conscious awareness.

The findings appeared in the journal eNeuro.



We’ve just discovered the Earth’s largest drum: our planet’s magnetosphere

A new study found that the Earth’s magnetic shield beats like a drum when it’s hit by external impulses. This confirms a decades-old theory

Artist rendition of a plasma jet impact (yellow) generating standing waves at the magnetopause boundary (blue) and in the magnetosphere (green). The outer group of four THEMIS probes witnessed the flapping of the magnetopause over each satellite in succession, confirming the expected behavior/frequency of the theorized magnetopause eigenmode wave. Image credits: E. Masongsong/UCLA, M. Archer/QMUL, H. Hietala/UTU.

The Earth’s magnetic field is driven by convection currents in the Earth’s outer core. Differences in temperature, pressure, and composition within the outer core cause some parts of the core to move around. The flow of this liquid iron generates electric currents, which in turn produce magnetic fields. The resulting magnetic fields produce further electric currents, which then generate their own magnetic fields, and so on. This natural self-sustaining loop is called a geodynamo, and produces a magnetic field that loops around the entire planet.

This magnetosphere is essential for life on Earth, as it protects the atmosphere from being eroded by the solar wind and deflects cosmic rays (high-energy charged particles that are mostly from outside the Solar System). However, we’re still learning a lot about the magnetosphere. Obviously, no one has gone down to the inner core to actually see how it is formed, and measurements of its overall structure remain challenging. In a new paper, researchers describe a feature of this field which had been predicted mathematically 40 years ago, but never previously observed.

Essentially, when an impulse strikes the outer boundary of the magnetopause, ripples can travel along its surface. These then get reflected back when they approach the magnetic poles. It’s a bit like how acoustic waves are absorbed and reflected by a drum. When the impulse interacts with the Earth’s magnetosphere, the interference the waves leads to a standing wave pattern in which specific points appear to be standing still while others vibrate back and forth — it’s exactly the way a drum resonates when struck.

Dr. Martin Archer, a space physicist at Queen Mary University of London and lead author of the paper, explains:

“There had been speculation that these drum-like vibrations might not occur at all, given the lack of evidence over the 45 years since they were proposed. Another possibility was that they are just very hard to definitively detect.”

“Earth’s magnetic shield is continuously buffeted with turbulence so we thought that clear evidence for the proposed booming vibrations might require a single sharp hit from an impulse. You would also need lots of satellites in just the right places during this event so that other known sounds or resonances could be ruled out. The event in the paper ticked all those quite strict boxes and at last, we’ve shown the boundary’s natural response,” said Archer.

In order to finally prove this theory, researchers used data from five NASATHEMIS satellites, designed specifically to study the magnetosphere. These five satellites were ideally located when a strong isolated plasma jet slammed into the magnetopause.

The probes were able to detect the boundary’s oscillations and the resulting sounds within the Earth’s magnetic shield, which confirmed the drum model and ruled out any alternative explanations

The Earth isn’t alone in having a magnetosphere. Other planets like Mercury, Jupiter and Saturn, have also been found to have similar magnetic shield — which means that drum-like vibrations may be possible elsewhere. However, further research is needed to understand just how often these vibrations occur and what their significance is.

Movements of the magnetopause can have wide-ranging effects on space weather, potentially damaging technology like power grids, GPS, and even passenger airlines.

Journal Reference: ‘Direct Observations Of A Surface Eigenmode Of The Dayside Magnetopause’. Archer et al. Nature Communications.
Credit: Los Angeles Air Force Base.

Earth’s magnetic poles might flip a lot faster than we thought — and we’re woefully unprepared

Credit: Los Angeles Air Force Base.

Credit: Los Angeles Air Force Base.

Earth can be likened to one big, planetary magnet. Likewise, Earth’s magnetic field is similar to that of a bar magnet tilted 11 degrees from the spin axis of the Earth. The magnetic field serves to deflect most of the solar wind, whose charged particles would otherwise strip away the ozone layer that protects the Earth from harmful ultraviolet radiation. But were you to use a compass at varied points throughout history, you would be in for a huge surprise, like seeing the compass’ needle pointing in the opposite direction than expected. When South becomes North and North becomes South, all sorts of unexpected and dangerous things can happen. This has happened many times throughout Earths’ geological history, and a new study suggests that we’re not only overdue for a pole reversal but that such events happen much faster and suddenly than previously thought.

The Earth’s magnetic field looks like that which would be produced by placing a bar magnet at the center of the Earth, with the North Magnetic Pole corresponding to the South Geographic Pole and vice versa. The Earth’s magnetic dipole originates in swirling currents of molten iron deep in the Earth’s core, and extends more than 10 Earth radii, or 63.7 million meters out into space on the side facing the Sun, and all the way to the Moon’s orbit, at 384.4 million meters on the opposite side. Magnetic field lines loop out of the South Geographic Pole and into the North Geographic Pole.

magnetic field

Credit: NASA Cosmos.

There are currents that guide the molten iron inside the planet’s core and, consequently, the magnetic poles can move or shift over time, losing or gaining strength. Scientists not only know that the magnetic field’s intensity changes over time, but they also know when dramatic shifts in intensity or pole reversal occurred. That’s because such events are recorded in the “frozen” ferromagnetic (or, more accurately, ferrimagnetic) minerals of consolidated sedimentary deposits or cooled volcanic flows on land.

It’s from these records that geologists learned that the last magnetic reversal took place 786,000 years ago. It happened very quickly, too, occurring in less than 100 years.

However, there are also dramatic reversals in field polarity, which occur more frequently. The challenge in pinpointing such events lies in the fact that igneous rocks do not capture the fine movements that lead up to a reversal. Andrew Roberts from the Australian National University (ANU) and colleagues found a workaround by studying stalagmite growing on the floor of a cave in southwestern China. A stalagmite is a type of rock formation that rises from the floor of a cave due to the accumulation of material deposited on the floor from ceiling drippings — given its slow growth, such formations offer the perfect opportunity to study slight variations in Earth’s magnetic field along the years.

The stalagmite, which is one meter in length and eight centimeters in diameter, has a candle-like shape and ranges in color from yellow to dark brown. Researchers cut it into 190 pieces, analyzing each with a high-res cryogenic magnetometer to make a snapshot of Earth’s magnetic field direction and strength as they stood from 107,000 to 91,000 years ago.

Writing in the Proceedings of the National Academy of Sciences, the authors of the new study found a brief pole reversal that occurred about 98,000 years ago and lasted for a century, maybe two. That’s a lot faster than scientists had guessed. Previously, scientists used to think it would take several thousands of years for the poles to change.

“The record provides important insights into ancient magnetic field behaviour, which has turned out to vary much more rapidly than previously thought,” Professor Roberts said.

This is bad news for a technologically-dependent species such as ourselves. Every pole reversal is joined by a weakening of the field and because the field’s intensity is bound to decrease considerably, much more radiation from space will be able to reach the planet’s surface than it does today. However, life on Earth shouldn’t be affected too much by this directly — humanity has lived through several pole reversals and we’re still here. Likewise, there were no mass extinction events coinciding with a pole reversal that scientists could find.

However, much has changed since the last time the planet’s magnetic field weakened by this much. For one, much of our existence is predicated on not only electrical power but also satellite-based communications, which nowadays are synced so much with the power grid that the two are basically inseparable. If our fleet of satellites was to suddenly come offline, much the world could suffer blackouts which could last for years. In the ensuing chaos, it’s anyone’s guess what would happen next.

Even today with Earth’s magnetic field at full strength, solar weather can pose a threat to sensitive electronics.

“Hopefully such an event is a long way in the future and we can develop future technologies to avoid huge damage, where possible, from such events,” Professor Roberts said in a statement.

No evidence to say that Earth’s magnetic pole is reversing, new study concludes

In recent years, the scientific community has closely followed the evolution of the Earth’s magnetic field, with some scientists finding clues of a sign of an incoming magnetic pole reversal (something which also spurred a hodgepodge of conspiracy theories). However, a new study reports that what we’re seeing now is probably not a precursor of a magnetic pole reversal.

The South Atlantic Anomaly. Image credits: NASA.

The Earth’s magnetic field is crucial for life on the planet, serving as a shield against hazardous radiation from space, especially coming from the Sun. Since 1840, scientists have been consistently monitoring this magnetic field, and since then, the global strength of the magnetic field has decayed at a rate of about five percent per century. Following this continuous decrease, a significant anomaly has emerged, called the South Atlantic Anomaly.

This anomaly represents an area of an abnormally weak magnetic field — think of it as a dip in the Earth’s magnetic defenses. Here, protection from harmful radiation from space is reduced, which has several unfortunate consequences (for instance, satellites in the area are more likely to suffer from communication blackouts and passengers on flights around the area are subjected to more radiation).

Within the research community, some have interpreted this anomaly as a sign of an incoming pole reversal. If this were the case, it wouldn’t really be surprising — the Earth’s magnetic field is constantly changing, and the way which it changes also changes. As a result, in the Earth’s geological history, magnetic pole reversals have been quite common, and we know this by studying geological proxies — magnetic minerals in the rocks and sediments “record” the orientation and strength of the Earth’s magnetic field at the time of rock formation. By dating the rocks, we can know how the magnetic field evolved, and we have a pretty good idea on how this field evolved through the ages. However, we don’t really know when the next reversal will come.

[panel style=”panel-default” title=”Chrons” footer=””]The Earth’s field has alternated between periods of normal polarity, in which the predominant direction of the field was the same as the present direction, and reverse polarity, in which it was the opposite. These periods are called chrons. The duration of chrons isn’t fixed, though the average time seems to be 450,000 years. The reversals themselves typically take between 1,000 and 10,000 years. However, the last one, which happened 780,000 years ago, happened very quickly — quite possibly in less than 100 years. It’s not really possible to predict these shifts.[/panel]

 Image via Wiki Commons.


Within their new study, scientists have reconstructed past changes in Earth’s magnetic field using paleomagnetic data from sediment cores and volcanic rocks from across the globe. They found a specifically good record for the time interval of 50,000 to 30,000 years before the present, including two magnetic dips that are similar to the South Atlantic Anomaly.

Neither of them led to a magnetic pole reversal, and as a result, the team concludes that the current anomaly is also unlikely to lead to a pole reversal. While this doesn’t rule out the possibility of a magnetic pole reversal at some point in the near future, it makes it much less likely. Monika Korte, co-author of the study, explained:

“Based on our observations of the past 50,000 years we conclude that the South Atlantic Anomaly cannot be interpreted as a sign for the beginning of a reversal of the poles. Times of the past that, unlike the beginning of the Laschamp excursion, showed patterns of the magnetic field like today were not followed by a pole reversal. After some time the anomalies disappeared.”


Richard Holme, Professor of Geomagnetism at the University of Liverpool and co-author, concludes:

“There has been speculation that we are about to experience a magnetic polar reversal or excursion. However, by studying the two most recent excursion events, we show that neither bear resemblance to current changes in the geomagnetic field and therefore it is probably unlikely that such an event is about to happen.

“Our research suggests instead that the current weakened field will recover without such an extreme event, and therefore is unlikely to reverse.”

The paper, `Earth’s magnetic field is probably not reversing’ has been published in Proceedings of the National Academy of Sciences (PNAS) doi:/10.1073/pnas.1722110115.

Sea turtles use magnetic fields to navigate the world

Turtles seem to “imprint” the magnetic field of the beach they were born, returning to it decades later to hatch the new generation. However, researchers report, this strategy sometimes tricks turtles into navigating to a beach that has a similar magnetic field to the one they were looking for.

Loggerhead sea turtles are a strange bunch. Facing an extremely dangerous beach run to the sea, and then daring the ocean on their own, they still somehow remember their birthplace, returning to it years and years later to lay their own eggs.

“Loggerhead sea turtles are fascinating creatures that begin their lives by migrating alone across the Atlantic Ocean and back. Eventually they return to nest on the beach where they hatched – or else, as it turns out, on a beach with a very similar magnetic field,” said Kenneth Lohmann, professor of biology in the College of Arts and Sciences at University of North Carolina (UNC).

UNC biologists Kenneth Lohmann and Roger Brothers already had some proof that adult loggerhead sea turtles use magnetic fields to find their way back to the beach where they themselves hatched. In a new study, the two scientists report that magnetic fields are the strongest predictor of genetic similarity among nesting loggerhead sea turtles, which adds new evidence to their magnetic imprint theory.

Traditionally, scientists have thought that animals that live close to each other are more likely to be similar genetically. This might also be the case because animals living in similar environments tend to develop similar adaptations. But for the loggerheads, proximity isn’t a predictor of genetical similarity — bug magnetic field is. In other words, turtles which lay eggs on a particular beach are more similar to other turtles which lay eggs on a beach with a similar magnetic field — even if that beach is much farther away, like on the opposite coast of Florida. Actually, researchers report, turtles sometimes mistake their beach for a different beach with a similar magnetic field.

Turtles aren’t the only ones to use magnetic fields to navigate across great distances, and researchers say this new finding could be extremely important for the conservation of these species.

“This is an important new insight into how sea turtles navigate during their long-distance migrations. It might have important applications for the conservation of sea turtles, as well as other migratory animals such as salmon, sharks and certain birds.”

Journal Reference: J. Roger Brothers, Kenneth J. Lohmann. Evidence that Magnetic Navigation and Geomagnetic Imprinting Shape Spatial Genetic Variation in Sea Turtles.

Magnetic field.

How birds “see” magnetic fields

Birds have a built-in magnetic sensor to help them find their home and migrate safely — all thanks to proteins in their eyes.

Magnetic field.

Image credits Popular Science Monthly Volume 83 via Wikimedia.

Common wisdom holds that iron-rich cells in birds’ beaks act as microscopic compasses to help them navigate. However, recent research suggests that this common wisdom may, in fact, be just common — sans wisdom: a new paper points to proteins in birds’ eyes that allow them to see magnetic fields.


Two new studies, one working with European robins (Erithacus rubecula), and the other with zebra finches (Taeniopygia guttata) both revolve around an interesting new molecule with the rather unfortunate name ‘Cry4’. Unlike the name would have you believe, this has nothing to do with tears and everything to do with the retina. Cry4 is a light-sensitive protein, which so far seems to be the first animal-sourced molecule we’ve identified that evolved specifically to detect magnetic fields.

The class of proteins Cry4 is part of is known as cryptochromes. From what we know so far, these proteins are involved in the workings of circadian rhythms (the body’s ‘biological clock’). However, because of quantum quirks some of them posses, certain proteins in this class are also believed to react to magnetic fields. These interactions could be harnessed by animals such as birds to sense the Earth’s natural magnetic field, according to Atticus Pinzon-Rodriguez, a biologist at the University of Lund in Sweden and lead author of the paper describing Cry4’s role in magnetoreception.

To figure out which of the proteins in this class act as the compass, Pinzon-Rodriguez’s team analyzed the retinas, muscles, and brains of 39 zebra finches for the presence of Cry4 and two related proteins, Cry1 and Cry2.

While expression levels of Cry1 and Cry2 rose and fell throughout the day in a rhythmic pattern, Cry4 levels remained constant — indicating that it was being steadily produced, the team reports.

“We assume that birds use magnetic compasses any time of day or night,” says University of Lund biologist Rachel Muheim, the paper’s co-author.

The team’s results are also supported by findings in the study on European robins, which also express constant levels of Cry4 throughout a 24-hour cycle but express higher levels during their migratory season. Furthermore, that study also revealed the protein in an area of the bird’s eyes that receives a lot of incoming light — a location which Pinzon-Rodriguez’s team says would help it act as a compass.

Right now, the evidence is compelling, but not yet enough to prove the theory beyond a doubt. Further research on birds with functioning Cry4 will be needed to either prove or disprove it.

The paper “Expression patterns of cryptochrome genes in avian retina suggest involvement of Cry4 in light-dependent magnetoreception” has been published in the Journal of the Royal Society Interface.

Magnetic field.

Astrochemists can now study stars’ magnetic fields using alcohol

Astrochemists have developed a technique which allows them to measure magnetic fields in space using methanol, the simplest type of alcohol.

Magnetic field.

Image credits Windell Oskay / Flickr.

While you might envision chemistry as something that’s sequestered in a tiny beaker, it’s actually a very powerful research tool for astronomers. Since the 1960’s or so, we’ve constantly been on the lookout for new molecules or compounds floating around in space using radio telescopes, and we’ve found quite a few. By following these molecules, astronomers can get an idea of the movements inside the dense (and otherwise quite opaque) clouds from which stars and planets are born. By understanding how they behave under different conditions (temperature, pressure), they can be used as a benchmark to determine physical parameters and inside these clouds as well.

However, there’s one thing these molecules couldn’t show us up to now: magnetic fields. And that’s actually a bummer, since magnetic fields are a major force involved in shaping massive stars. Now, however, a team of scientists led by Boy Lankhaar at Chalmers University of Technology thinks they’ve solved the puzzle. Their work with methanol (CH₃OH), the simplest alcohol compound (but dont drink this its toxic), gives astrochemists their first tool to investigate magnetic fields of developing massive stars.

Follow the alcohol

“When the biggest and heaviest stars are born, we know that magnetic fields play an important role. But just how magnetic fields affect the process is a subject of debate among researchers,” says Lankhaar. “So we need ways of measuring magnetic fields, and that’s a real challenge. Now, thanks to our new calculations, we finally know how to do it with methanol.”

The idea of using methanol to study magnetic fields is actually a few decades old now. Molecules of the compound are common around many newborn stars, and they shine as natural microwave lasers (masers). The signals “come from the regions where magnetic fields have the most to tell us about how stars form,” adds co-author Wouter Vlemmings. Even better, the inputs of these masers are both strong enough for us to pick up and are emitted at specific frequencies, so we can distinguish them from background noise.

The problem utill now was that we didn’t have any frame of reference to interpret these signals by — we could see the text but didn’t know how to read, so to speak.

Previous attempts to measure the magnetic properties of methanol in a laboratory setting have always met with difficulty and couldn’t be completed. Instead of going the same route, the team decided to start with a theoretical model, knitting it as closely as possible to previous lab measurements and theory. The result is a model that describes the behavior of methanol in a magnetic field based on “the principles of quantum mechanics,” Lankhaar explains.

After checking that their model fits to available experimental data, the team moved on to “extrapolate to conditions we expect in space”. The task proved to be surprisingly challenging, and the team’s two theoretical chemists, Ad van der Avoird and Gerrit Groenenboom from the Radboud University in the Netherlands, had to refine previous work based on new calculations.

“Since methanol is a relatively simple molecule, we thought at first that the project would be easy. Instead, it turned out to be very complicated because we had to compute the properties of methanol in great detail,” says Ad van der Avoird.

Still, all that work paid off. Astronomers and astrochemists now have a reliable tool to study magnetic fields throughout the observable universe. Who knows what it will reveal?

The paper “Characterization of methanol as a magnetic field tracer in star-forming regions” has been published in the journal Nature Astronomy.

The Ever-changing and Skepticized Van Allen Belts

The Van Allen belts are two radiation belts. These are zones of electrically charged particles which are poised, encompassing the Earth far above the surface, and held there by the planet’s magnetic field. The first of the belts was discovered in early 1958 through data collected by Explorer I (the United States’ first space satellite) and the Explorer III and Pioneer satellites, under James Alfred Van Allen and his team at the University of Iowa.

Similar radiation belts have since been found surrounding other planets, but the term of Van Allen belts only refers to those two belts (and sometimes other belts that are transitorily formed) which surround the Earth. They have been dubbed the Van Allen belts after the American physicist credited with their discovery.

Each of the two belts surrounds the Earth in a sort of doughnut-shaped formation. The inner belt reaches from approximately 600 to 3,000 miles above the Earth, and the outer belt from about 9,300 to 15,500 miles above the Earth. Astronomers have determined that the belts consist of many electrically charged particles, like protons and electrons. Earth’s magnetic field traps these particles, directing them to the magnetic poles.

The particles move in spiral paths along a system of flux lines, curving from the north magnetic pole to the south magnetic pole. As the particles come nearer either pole, the converging flux lines reflect them toward the opposite pole. This effect keeps the particles of the Van Allen belts bouncing between the poles. The belts receive new particles from the solar wind, a continuous stream of charged particles emitted from our sun.

Chart Showing the Van Allen Belts in Proportion to Earth


Other particles can be gained by solar flares and cosmic rays. Intense solar activity can disrupt the belts, leading to magnetic storms. Such disruptions also affect radio reception, cause surges in power lines, and produce auroras.

Ever since their discovery, the Van Allen belts have concerned and inspired people’s minds. Hollywood feature film and TV producer, writer, and director Irwin Allen came out with his science fiction movie Voyage to the Bottom of the Sea in 1961, three years after the discovery of the first belt. The main plot conceived by Allen and Charles Bennett revolves around saving all life on Earth from the natural inferno that was created when a meteor shower pierced the Van Allen radiation belt, catching it ablaze.

Ice burgs begin to melt in the Arctic, entire forests are engulfed in flames, and the crews of sea-going vessels traveling on the ocean’s surface are baked alive. Eventually, scientist Admiral Harriman Nelson proposes to shoot a nuclear missile from his submarine Seaview into the burning belt at a certain projection and time, which would, in theory, overwhelm and extinguish the skyfire, essentially “amputating” the belt from the Earth.

Scene from Irwin Allen’s 1961 Film Voyage to the Bottom of the Sea. Source: 20th Century Fox.


Even today, decades later, people are concerned about the radiation belts. A prominent group of physicists wants the belts eliminated altogether. A plan was even suggested in which long conducting tethers that are charged with a high voltage are deployed from satellites into the belts. It would force charged particles that come into contact with the tethers to have their pitch angle altered.

Over time, theoretically, this would dissolve the inner belts. The belts pose certain difficulties and dangers (mainly caused by radiation) whenever a satellite, telescope, or human is to be launched into outer space. There is a decent scientific argument in that these belts provide anything useful, or that we could do away with them without a negative effect.

According to some, if the belts were not there, the Earth would no longer possess a magnetic field. That means that cosmic ray particles would be at liberty to collide with our atmosphere in larger quantities, resulting in a higher background level of secondary “air shower neutrons”, leading to higher doses of background radiation on the surface. If the Van Allen belts were gone, it would definitely impact human life.

Other sources:

The World Book Encyclopedia Vol. 20. World Book, Inc., 1987.

Artist's conception of the complex magnetic field environment at Mars. Yellow lines represent magnetic field lines from the Sun carried by the solar wind, blue lines represent Martian surface magnetic fields, white sparks are reconnection activity, and red lines are reconnected magnetic fields that link the surface to space via the Martian magnetotail. Credit: Anil Rao/Univ. of Colorado/MAVEN/NASA GSFC.

NASA discovers Mars has a magnetic tail twisted by solar wind

Artist's conception of the complex magnetic field environment at Mars. Yellow lines represent magnetic field lines from the Sun carried by the solar wind, blue lines represent Martian surface magnetic fields, white sparks are reconnection activity, and red lines are reconnected magnetic fields that link the surface to space via the Martian magnetotail. Credit: Anil Rao/Univ. of Colorado/MAVEN/NASA GSFC.

Artist’s conception of the complex magnetic field environment at Mars. Yellow lines represent magnetic field lines from the Sun carried by the solar wind, blue lines represent Martian surface magnetic fields, white sparks are reconnection activity, and red lines are reconnected magnetic fields that link the surface to space via the Martian magnetotail. Credit: Anil Rao/Univ. of Colorado/MAVEN/NASA GSFC.

Mars has a unique magnetotail found nowhere else in the solar system, NASA scientists report. According to the data gathered by the Mars Atmosphere and Volatile Evolution Mission (MAVEN) spacecraft, currently orbiting the Red Planet, this intriguing invisible magnetic tail is twisted by the interaction with solar wind. Studying this rare phenomenon could fill in the blanks in our understanding of how Mars went from a flourishing, wet world to a barren wasteland.

Tail in the solar wind

Here on Earth, the motion of molten iron alloys in its outer core acts like a geodynamo which generates a massive magnetic field. Scientists call our planet’s magnetic field the magnetosphere. It extends for several tens of thousands of kilometers into space, well above the atmosphere, sheltering the planet from charged particles of the solar wind and cosmic rays that would otherwise strip away the upper atmosphere, including the ozone layer that protects the Earth from harmful ultraviolet radiation.

Earth isn’t unique in this respect. Jupiter has masses of liquid metallic hydrogen in its outer mantle, creating the largest planetary magnetic field in the solar system. Uranus generates a global magnetosphere closer to the surface, which leads to some very strange quadrupole field effects —  rather than just a north and a south, there are another two poles lurking in a quadrupole field. Mars also used to have a magnetic field but lost it half a billion years after its formation.

Scientists aren’t sure how the red planet lost its magnetosphere but there are currently two leading theories. The first says that its core shut down, deactivating the dynamo and consequently Mars’ global magnetic field. The other leading hypothesis suggests that massive heat generated by large asteroid impacts warmed the outer layer of the planet to such a degree that it shut down convection from the hot core to the mantle.

After Mars’ lost its magnetic field, the atmosphere soon followed. With nothing to shelter it from cosmic rays and solar storms, the atmosphere thinned to the point that it’s now roughly 100 times less dense than Earth’s atmosphere. Mars is still continuously losing its atmosphere.

Nowadays, solar wind mostly comprised of protons strikes Mars at about 1,000,000 mph, moving so quickly that it flings atmospheric particles. Presently, Mars loses about 100 grams of atmospheric gas every second.

According to NASA scientists, there are still some remnant so-called ‘fossil’ magnetic fields embedded in certain features of the red planet’s surface. Instruments onboard MAVEN collected data that suggest the planet has a magnetotail formed when magnetic fields carried by solar wind interact with the fossil magnetic fields in a process called magnetic reconnection. For the two magnetic fields to join in magnetic reconnection, the solar wind field needs to be oriented in the opposite direction to that of the patchwork magnetic fields from Mars.

“We found that Mars’ magnetic tail, or magnetotail, is unique in the solar system,” said Gina DiBraccio of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, in a public statement. “It’s not like the magnetotail found at Venus, a planet with no magnetic field of its own, nor is it like Earth’s, which is surrounded by its own internally generated magnetic field. Instead, it is a hybrid between the two.”

Since MAVEN continually changes its orbit orientation with respect to the Sun, the spacecraft took measurements covering a wide range of Martian surface features. NASA scientists then used this valuable data to plot a map of the Martian magnetotail and its interaction with the solar wind. The scientists then designed a model that predicts the magnetic reconnection and compared their results with the live data. The theoretical and experimental data were in agreement suggesting the Martian magnetotail twists “45 degrees from what’s expected based on the direction of the magnetic field carried by the solar wind,” said DiBraccio.

Next, NASA plans to use other instruments deployed by MAVEN, this time to generate an ‘escaping particles’ map. The goal is to see whether or not reconnection is contributing to Martian atmospheric loss and how significant this effect is.

“Mars is really complicated but really interesting at the same time,” said DiBraccio.

How northern lights and stranded whales might strangely be connected

Researchers found an unlikely connection between stranded whales and the Northern Lights.

The northern lights might be a brilliant spectacle for some, but they might have spelled doom for some unfortunate sperm whales. Credits: NASA.

In early 2016, the stranding of 29 sperm whales in the North Sea left researchers surprised, since these whales are not normally found in that part of the world. None of them survived. Autopsies revealed that the whales were all in pretty good health, so the exact reason why they became stranded in shallow waters remained a mystery. Now, researchers proposed an unexpected culprit: geomagnetic storms.

Sperm whales live in temperate to warm waters all year long. They tend to migrate between the warmer equatorial waters and the colder but squid-rich waters of the Norwegian sea. The North Sea isn’t really on their list, and neither is it on the list of Gonatus fabricii squid — their preferred food — so it doesn’t make much sense to venture that far. They normally stick to the western side of Great Britain, whereas the North Sea is more to the east. That fatal mistake might be explained through magnetic fields.

The magnetic map of where the Norwegian and North Seas join. The whales should have traveled along the white arrow, but instead traveled along the red arrow. Credit: Vanselow et al.

The Earth’s magnetic field is not uniform — it has numerous anomalies, both positive and negative, big and small. It’s thought that some creatures use this field to navigate through their migration, but this technique can be severely disturbed by solar storms, which produce huge differences that totally confuse the animals. This is a relatively new concept, but it has been previously documented in both birds and bees. Dolphins also seem to use the magnetic field, so it would make sense for whales to do it too.

Dr Klaus Vanselow from the University of Kiel, Germany, believes this is also what happened to the whales. He and his team claim a large solar storm distorted the magnetic field, causing the unfortunate mammals to lose their way in the sea. The same solar storm produced spectacular northern lights, visible from the Arctic down to Scotland.

Specifically, they identified two such storms occurring on December 20/21, 2015, and December 31 and January 1, 2015/2016. They found that the anomalies caused by these storms stretched down to the Shetland Islands, where the whales would have turned right (east) instead of left (west). Normally, the whales would sense a magnetic barrier in front of the North Sea and avoid diving into it, kind of like a magnetic mountain. However, the storms “leveled” these magnetic mountains, rendering them invisible for the whales.

This misstep was all it took.

“Sperm whales are very huge animals and swim in the free ocean so if they are disrupted by this effect, they can swim in the wrong direction for days and then correct it,” says Vanselow. “But in the area between Scotland and Norway, if the whales swim in the wrong direction for one or two days, then it is too late for them to go back, they are trapped.”

This seems to fit very well with the timeline of the whales but of course, correlation does not imply causation. We still don’t know exactly how the whales detect and operate based on this magnetic field, and just because this seems to fit doesn’t mean it is indeed what happened.

“It would be difficult to say that ‘yes this was the cause’, we would be cautious in saying that,” said Abbo Van Neer from the University of Hannover who carried out the autopsies on the 16 whales that stranded in Germany. “But it is a valid hypothesis and a potential reason for the stranding.”

In other words, it’s a properly designed study that offers a solid hypothesis, but it doesn’t really prove anything. Dr Antti Pulkkinen, who is leading a NASA effort to investigate the link between strandings in Cape Cod and geomagnetic storms, says there’s just not enough data to draw a definite conclusion.

“Having looked at this problem from a data analysis point of view, it is not a single factor that contributes to this. Things need to line up from multiple different perspectives for these events to take place.”

Journal Reference: Klaus Heinrich Vanselow, Sven Jacobsen, Chris Hall and Stefan Garthe. Solar storms may trigger sperm whale strandings: explanation approaches for multiple strandings in the North Sea in 2016. DOI: https://doi.org/10.1017/S147355041700026X


Ancient potters carefully recorded the planet’s magnetic field — without even knowing it

Three millennia ago, a potter working near Jerusalem made a big jar. It was likely meant to hold olive oil or some pretty valuable liquid. The potter stamped the jar with the royal seal and sent it as tax payment for his work. This was common practice and was maintained for centuries despite ongoing wars and numerous kings exchanging the reigns — potters paid their taxes in pottery. But without knowing it, these artisans didn’t only perpetuate an old system or taxpaying, they also monitored the Earth’s magnetic field.

Earth’s magnetic field changes all the time — geologically

Ancient jar handles like this one, stamped with a royal seal, provide a detailed timeline of the Earth’s magnetic field thousands of years ago.
Image courtesy of Oded Lipschits

You might have heard the Doomsday theories that the magnetic poles will reverse and that will kill us all. That’s simply crap. Earth’s magnetic poles have switched numerous times in its history, and are in state of constant movement. We just don’t see that because it takes a lot of time for them to move around. If you were alive 800,000 years ago and you’d look at your compass, you’d be shocked. North points where South is, because back then, the poles were reversed. For the past 20 million years, Earth has settled into a pattern of a pole reversal about every 200,000 to 300,000 years, although it has been more than twice that long since the last reversal.

We know this does happen, but we’re still not exactly sure why this happens

“Albert Einstein defined this problem as one of the five most enigmatic issues in modern physics, and it still is, because the mechanism that creates the magnetic field is not well understood,” says Erez Ben-Yosef, an archaeologist at Tel Aviv University in Israel and an author of the paper.

This is rarely a clean back-and-forth process, as magnetic fields morph and push and pull at one another, with multiple poles emerging at odd latitudes throughout the process. We know this thanks to cores taken from deep ocean floors. The magnetic field determines the polarization of lava as it is laid down on the ocean floor on either side of the Mid-Atlantic Rift where the North American and European continental plates are spreading apart. Like a compass, the lava records the position of the poles when it cools down. Date the lava, and you know where the poles were at that time. Date many pieces of lava, and you’ll have a good picture of how the poles evolved. Something similar happened to the pots.

Pots, pans, and magnetometers

As the potters would work the clay, the molten iron that was rotating deep below them tugged at tiny bits of magnetic minerals embedded in the potters’ clay. The jars were heated in the kiln and then cooled down, just like the lavas did, and magnetic minerals in the clay aligned themselves. The only problem then is how you date the pots. This is where it gets even cooler: remember when we said potters used to stamp the king’s seal onto their work? That’s how you date them.

“Instability — or even better, wars and destruction — are the best for us,” says Ben-Yosef. (Peaceful transitions are nearly impossible to spot in sedimentary layers, but something like a burned city makes a clearly visible dark line. And the Assyrians had a knack for destroying cities.)

Schematic illustration of Earth’s magnetic field.
Credits: Peter Reid, The University of Edinburgh

Ben-Yosef and his colleagues studied 67 jar handles spanning from the late 8th century B.C. to the late 2nd century B.C., finding that the movement of the poles was much messier than most people believed. For instance, during the 8th century BC, things got a little wild and the intensity of the magnetic field was double to what it is today.

“It was the strongest it’s been, at least in the last 100,000 years, but maybe ever. We call this phenomenon the Iron Age spike,” Ben-Yosef says.

After that, it started dropping fast, losing 30% of its intensity in just 30 years. This is particularly interesting as scientists have already indicated that the Earth’s magnetic field intensity is dropping, something which is yet unexplained. We’ve started learning this after geophysicists started using magnetic field measurement instruments called magnetometers.

“We are losing the magnetic field,” Ben-Yosef says. “We already lost more than 10 percent of its strength, so people are concerned that we might lose the magnetic field entirely.”

Geology and archaeology

Tiny minerals in the clay of this jar hold information about the strength of the Earth’s magnetic field at the time the jar was fired, thousands of years ago.
Image courtesy of Oded Lipschits

So while we had a pretty good idea of how the magnetic field evolved in geologic time, now we also get a better picture of what happened in recent times. Geologist Steven Forman of Baylor University was thrilled to read this study. He also found evidence of a magnetic spike about 3,000 years ago, based on a different study of Hall’s Cave in Texas.

“But we didn’t have the type of time resolution that the study in PNAS has,” he says, because it’s a lot harder to pinpoint rocks on a timeline than it is to pinpoint man-made objects. “That’s what so cool about what they did. They pulled this out of heated ceramics.”

It’s absolutely delightful to see how to different branches of science can meet up at a middle point and complement each other so. Geologists, archaeologists, physicists, and ancient potters – working together to solve one of the Earth’s greatest mysteries. Who would have thought?

Cardinal Fish

Baby Cardinal fish follow the magnetic field back home, scientists find

When night comes, baby Cardinal fish always know where home is — because they can feel the Earth’s magnetic field. New research has shown that the animals have an internal ‘compass’ that can help them orient even when there’s no sun or stars shining to guide them.

Cardinal Fish

Image credits Serge Melki / Flickr.

Professor Mike Kingsford from the ARC Centre of Excellence for Coral Reef Studies at James Cook University wanted to know why it is that baby Cardinal fish can always find their home at night. So he teamed up with colleagues from Germany to study the fingernail-sized little critters.

“This study is the first clear demonstration that reef fish larvae possess magnetic senses to orient them at night,” says Professor Kingsford. “Up until now, we only knew adult birds, marine mammals, sharks and boney fish have this in-built sense of direction.”

The team collected Cardinal fish less than one centimeter in length from Great Barrier Reef’s One Tree Island. They tested how well the fishes were able to orient in total darkness in the same magnetic field as the reef’s. As Kingsford explained, the fish normally orient to the south east but when the team shifted the magnetic field 120 degrees clockwise, the fish changed the direction they swam in — they all turned west, confident they were still on track. This shows that the animals can feel magnetic fields and use them to orient themselves.

“We know from our previous research that once they start to get closer to their target, a ‘homing process’ begins, where the larvae rely on odor, sounds and landmarks to find and settle on a reef,” Kingsford added.

Reef fish, such as the Cardinals, hatch from eggs in the reef as larvae. They then spend a few days up to months in the open ocean while they grow and look for a different reef to settle or return home. But once they do reach a reef, they generally stay there for life.

“The study tells us these baby fish actually have brains. They know where they are going and are strong swimmers. As a result they have some control over the reef they end up on. It’s not just about being led by the currents.”

“Knowing this, we can develop more accurate models of where larvae go to determine the best way to protect and maintain sustainable fish stocks.”

The full paper “A magnetic compass that might help coral reef fish larvae return to their natal reef” has been published in the journal Current Biology.

An illustration of ancient Earth's magnetic field compared to the modern magnetic field. Credit: Peter Driscoll

Earth may have had multiple magnetic poles one billion years ago

First and foremost, Earth owes its paradisiac condition to the powerful magnetic field that shields it from harmful radiation. Without this convenient field generated by a magnetic dipole there would be no plants, no bacteria, no humans — we’d be just like Mars. But it hasn’t always been this simple and stable. A new research suggests the planet went through periods of chaotic shifts in the magnetic field which lasted hundreds of millions of years. At times, more than two poles were active generating multiple, weaker magnetic fields than the one enveloping Earth today.

An illustration of ancient Earth's magnetic field compared to the modern magnetic field. Credit: Peter Driscoll

An illustration of ancient Earth’s magnetic field compared to the modern magnetic field. Credit: Peter Driscoll

The earth’s core acts like a geomagnetic dynamo. The solid inner part is constantly exchanging heat with the iron outer core, keeping it in a state of liquid motion. But the inner core was not always solid. It went through a strange period between 1 billion and 500 million years ago in which it was in a liquid state, and only began solidifying some 650 million years ago.

Peter Driscoll, a scientist at the department of terrestrial magnetism at the Carnegie Institution of Washington, was among the team of researchers who made simulations and models of Earth’s geomagnetic dynamo based on geological findings that revealed the planet’s thermal past.

“What I found was a surprising amount of variability,” Driscoll said. “These new models do not support the assumption of a stable dipole field at all times, contrary to what we’d previously believed.”

For instance, simulations suggest Earth had a dipole magnetic field one billion years ago but then transitioned to multiple poles positioned across the planet which generated weaker magnetic fields up to 650 million years ago. During this time, life may have been in a lot of trouble as it sought to adapt to varying magnetic conditions.

The implications are numerous. For one, it could change how scientists study the planet’s continental plates and ancient climate, both heavily influenced by the magnetic field.

“These findings could offer an explanation for the bizarre fluctuations in magnetic field direction seen in the geologic record around 600 to 700 million years ago,” Driscoll added. “And there are widespread implications for such dramatic field changes.”

These predictions are not the final word, though. Once these models are compared to magnetized rocks, we might be able to reach a more accurate picture.

The findings were published in the journal Geophysical Letters.