Tag Archives: field

Magnetic field readings point to the structure of Saturn’s interior

Researchers at the Johns Hopkins University have completed a new model of Saturn’s interior, which hints at a thick layer of helium rain that modulates the gas giant’s magnetic field.

Saturn’s interior with stably stratified Helium Insoluble Layer (HIL). Image credits Yi Zheng (HEMI/MICA Extreme Arts Program) / Johns Hopkins University.

The so-called ‘gas giants’ are notoriously hard to peer into, and they remain some of the most mysterious planets out there. Given the extreme environments they represent, it’s likely going to be a while before this changes, and an even longer while before any astronauts can actually go see for themselves.

That doesn’t mean we can’t draw some conclusions based on what we do know, however. And a team from Johns Hopkins University did just that, creating a new digital model looking into Saturn’s interior. This model hints at a temperature difference in the helium rain layer between the planet’s equator (where it is hotter) and the poles (where it gets colder).

Hot waist

“By studying how Saturn formed and how it evolved over time, we can learn a lot about the formation of other planets similar to Saturn within our own solar system, as well as beyond it,” said co-author Sabine Stanley, a Johns Hopkins planetary physicist.

“One thing we discovered was how sensitive the model was to very specific things like temperature,” she adds. “And that means we have a really interesting probe of Saturn’s deep interior as far as 20,000 kilometers down. It’s a kind of X-ray vision.”

Saturn is unique among the other gas giants in that its magnetic field is almost perfectly symmetrical around its axis. Since magnetic fields are generated by structures inside a planet’s body, this tidbit could help us glean some information about Saturn’s interior layout.

Using data recorded by NASA’s Cassini mission, researchers at Johns Hopkins University created detailed computer simulations using software typically employed for weather and climate simulations. The models indicate that there is a heat gradient in Saturn’s interior, with higher temperatures towards the equator. Overall, this could point to the existence of a layer of liquid helium around the planet’s core.

The magnetic field of Saturn seen at the surface. Image credits Ankit Barik / Johns Hopkins University.

This structure creates a dynamo-like mechanism, which goes on to produce the striking magnetic field recorded around Saturn. On Earth, the planet’s iron core and molten metal mantle play the role of dynamo. It was expected that gas giants rely on a different structure to create their magnetic field, given their different chemical composition and extreme mass, but this is the first study to actually pinpoint one candidate structure for this role in gas giants.

Apart from this, the simulations also suggest that a certain level of non-axisymmetry could be present near Saturn’s north and south poles.

“Even though the observations we have from Saturn look perfectly symmetrical, in our computer simulations we can fully interrogate the field,” said Stanley.

Naturally, until we can put a person on Saturn to check, we can’t confirm these findings. Until then, models will have to suffice.

The paper “Recipe for a Saturn‐Like Dynamo” has been published in the journal AGU Advances.

Sunset.

Massive solar storms are naturally-recurring events, study finds — and we’re unprepared for them

Solar storms can be even more powerful than what our measurements so far have indicated — and we’re still very unprepared.

Sunset.

Image via Pixabay.

Although our planet’s magnetic field keeps us blissfully unaware of it, the Earth is constantly being pelted with cosmic particles. Sometimes, however — during events known as solar storms, caused by explosions on the sun’s surface — this stream of particles turns into a deluge and breaks through that magnetic field.

Research over the last 70 years or so has revealed that these events can threaten the integrity of our technological infrastructure. Electrical grids, various communication infrastructure, satellites, and air traffic can all be floored by such storms. We’ve seen extensive power cuts take place in Quebec, Canada (1989) and Malmö, Sweden (2003) following such events, for example.

Now, new research shows that we’ve underestimated the hazards posed by solar storms — the authors report that we’ve underestimated just how powerful they can become.

‘Tis but a drizzle!

“If that solar storm had occurred today, it could have had severe effects on our high-tech society,” says Raimund Muscheler, professor of geology at Lund University and co-author of the study. “That’s why we must increase society’s protection again solar storms.”

Up to now, researchers have used direct instrumental observations to study solar storms. But the new study reports that these observations likely underestimated how violent the events can become. The paper, led by researchers at Lund University, analyzed ice cores recovered from Greenland to study past solar storms. These cores formed over the last 100,000 years or so, and have captured evidence of storms over that time.

According to the team, the cores recorded a very powerful solar storm occurring in 600 BCE. Also drawing on data recovered from the growth rings of ancient trees, the team pinpointed two further (and powerful) solar storms that took place in 775 and 994 CE.

The result thus showcases that, although rare, massive solar storms are a naturally recurring part of solar activity.

This finding should motivate us to review the possibility that a similar event will take place sooner or later — and we should prepare. Both the Quebec and Malmö incidents show how deeply massive solar storms can impact our technology, and how vulnerable our society is to them today.

“Our research suggests that the risks are currently underestimated. We need to be better prepared,” Muscheler concludes.

The paper “Multiradionuclide evidence for an extreme solar proton event around 2,610 B.P. (∼660 BC)” has been published in the journal Proceedings of the National Academy of Sciences.

Magnetic lines.

Earth’s inner core became solid just in time to save the planet

The Earth’s solid core likely formed about 565 million years ago, new research reveals — saving Earth’s magnetic shield in the process.

Magnetic lines.

Image credits Windell Oskay / Flickr.

Earth’s magnetic field forms a veritable bulwark against charged particles coming from space — such as solar wind and rays of cosmic radiation — that would otherwise turn us all to crispy mush. It also safeguards Earth’s atmosphere, which would be flayed little by little by these same solar winds in its absence. So if you enjoy breathing, you should be a big fan of the Earth’s magnetic field.

Our planet hasn’t always enjoyed the magnetic field protection of today, however. New research suggests that it’s only been around for roughly 565 million years.

Restarting the dynamo

The Earth’s magnetic field was at its lowest intensity around that time, the authors of a new study report. This suggests our planet’s internal dynamo was close to collapsing at that date (since this dynamo is what generates the planet’s magnetic field). The formation of Earth’s solid inner core was the one event that could strengthen this geomagnetic field, so this could not have happened yet.

As such, the team proposes that the planet’s inner core had begun to solidify around this time, although the process was not complete. These results should help refine our current estimates of when Earth’s inner core solidified. Currently, these estimates range between 2.5 billion and 500 million years ago.

For the study, John Tarduno and colleagues measured the geomagnetic field’s past intensity and direction. They did this by looking at tiny magnetic inclusions found within single crystals of plagioclase and clinopyroxene formed 565 million years ago in what is now Canada’s eastern Quebec. Think of these inclusions — usually iron compounds — as tiny compass needles, aligning themselves to the magnetic field as the crystals formed. By studying them, the team could determine the direction and intensity of the magnetic field at the date of the crystals’ formation.

They found unprecedentedly low geomagnetic field intensities. From this, they inferred that there was a high frequency of magnetic reversals at that time, suggesting that the geodynamo was on the point of collapsing. Iron solidifying at the (fledgling) inner core boundary would have injected significant energy into the dynamo system by driving the currents of liquid metal that generate the magnetic field. Computer simulations predicted that this energy boost would be preserved in the rock record, which determines the team to look for evidence in ancient crystals.

In a News & Views article detailing the studies, Peter Driscoll writes that “the nucleation of the inner core may have occurred right in the nick of time to recharge the geodynamo and save Earth’s magnetic shield.”

The paper “Young inner core inferred from Ediacaran ultra-low geomagnetic field intensity” has been published in the journal Nature.

Saturn Illustration.

Perturbations in Saturn’s rings reveal how long a day is on the gas giant

Saturn’s days are 10 hours, 33 minutes, and 38 seconds long — and we know this by looking at wave patterns in its rings.

Saturn Illustration.

Illustration showing NASA’s Cassini spacecraft in orbit around Saturn.
Image credits NASA / JPL-Caltech.

New observations from NASA’s Cassini spacecraft allowed researchers at the University of California Santa Cruz to calculate Saturn’s rate of rotation. This measurement — the most precise determination of its rotation rate — was based on observations of wave patterns created within the planet’s rings.

Timekeeping rings

“Particles in the rings feel this oscillation in the gravitational field. At places where this oscillation resonates with ring orbits, energy builds up and gets carried away as a wave,” explained Christopher Mankovich, a graduate student in astronomy and astrophysics at UC Santa Cruz, and lead author of the study.

Just like our own planet, Saturn vibrates in response to perturbations (large-scale movement of matter). Unlike our planet, these perturbations come not from the movement of tectonic plates, but likely from heat-driven convection in the planet’s gassy bulk. Such internal oscillations move about massive quantities of gas, which has a noticeable impact on local densities within Saturn’s atmosphere. Such changes, in turn, cause noticeable changes in the planet’s localized gravitational pull. And, even better, the frequency of oscillation within Saturn carries over to the gravitational effects — in short, they share the same ‘fingerprint’, so these internal events can be linked to their external, gravitational effects.

Saturn rings.

Image of Saturn’s rings taken by NASA’s Cassini spacecraft on Sept. 13, 2017.
Image credits NASA / JPL-Caltech / Space Science Institute.

Naturally, we’d need satellites or other sorts of equipment in orbit across the planet to pick up on such gravitational fluctuations. Which we haven’t really brought over yet. Rather conveniently, however, Saturn has a sprawling ring system surrounding it. They do react to the planet’s gravitational pull, its fluctuations causing certain wave patterns to form inside the rings. Not all patterns seen inside the rings are caused by gravitational effects — but most are.

In effect, this makes the rings act similarly to seismographs, devices that we use to measure earthquakes.

“Some of the features in the rings are due to the oscillations of the planet itself, and we can use those to understand the planet’s internal oscillations and internal structure,” says Jonathan Fortney, professor of astronomy and astrophysics at UC Santa Cruz and paper coauthor.

NASA’s Cassini spacecraft allowed researchers to observe Saturn’s rings in unprecedented detail. Mankovich’s team developed a series of models of the planet’s internal structure and used them to predict the frequency spectrum of Saturn’s internal vibrations. Then they compared their predictions to waves observed by Cassini in Saturn’s C ring.

One of the main results of this study is an estimation of Saturn’s speed of rotation — which has been notoriously difficult to accurately pin down. Saturn is basically a huge clump of gas and, as such, its surface doesn’t have any fixed, distinctive features we could track as it rotates. The planet is also unusual in that its magnetic poles are nearly perfectly aligned to its axis of rotation — so we can’t track those either. On Earth, for example, the magnetic poles aren’t aligned with this axis.

Mankovich’s team determined that a day on Saturn lasts for 10 hours, 33 minutes, and 38 seconds — several minutes shorter than previous estimates (which were based on radiometry readings from the Voyager and Cassini spacecraft).

“We now have the length of Saturn’s day, when we thought we wouldn’t be able to find it,” said Cassini Project Scientist Linda Spilker.

“They used the rings to peer into Saturn’s interior, and out popped this long-sought, fundamental quality of the planet. And it’s a really solid result. The rings held the answer.”

The paper “Measurement and implications of Saturn’s gravity field and ring mass” has been published in the journal Science.

Jupiter magnetic field.

Jupiter’s magnetic field is extremely bizarre, potentially due to unknown processes in its core

Jupiter’s magnetic field is crazy!

Jupiter, Io.

Jupiter and Io, one of its many moons.
Image via Pixabay.

The first map of the Jovian magnetic field has been compiled by an international team of researchers — and heads are still being scratched over it. The gas giants’ magnetic field is unlike anything we’ve ever seen before, hinting at unknown processes going on beneath its surface.

King of the gods

It didn’t come as much of a surprise to any researcher that Jupiter’s magnetic field is in a class of its own. While the gas giant boasts 11 times the diameter of our planet, it’s magnetic field is over 20,000 times as strong. It’s also much larger and has several complex features that have no counterpart in our own planet’s magnetic signature. These features, as far as we can tell, may stem from Jupiter’s rapid rotation and large liquid metallic hydrogen interior.

New data beamed back by the Juno spacecraft — which is still busy orbiting around the planet’s poles — allowed researchers from the US and Denmark to study this magnetic field much more closely than ever before. Starting from this data, which was recovered during eight orbits, they mapped the magnetic field in unprecedented detail at depths up to 10,000 kilometers (6,214 miles). Instead of making things more clear, however, the wealth of data only created further confusion. Take a look:

Jupiter magnetic field.

Image credits Moore et al., 2018, Nature.

Jupiter’s magnetic field emerges from a broad area close to its North pole (red on the image above) and re-enters around the South pole — so far, not especially surprising. What is very surprising, however, is that part of the magnetic field re-enters through a highly concentrated region just south of the equator — an area the team calls the Great Blue Spot.

The field is much weaker outside of these areas (grey-blue in the image above).

Earth’s magnetic field is dipolar. The field emerges from the South pole, re-enters through the North pole, and runs through the center of the planet. There are small non-dipolar components, but they’re relatively evenly spread out across the two hemispheres and they’re nowhere near as massive as the Great Blue Spot.

None of it prepared us for Jupiter’s hectic magnetic display.

“Before the Juno mission, our best maps of Jupiter’s field resembled Earth’s field,” planetary scientist Kimberly Moore of Harvard University told Newsweek. “The main surprise was that Jupiter’s field is so simple in one hemisphere and so complicated in the other. None of the existing models predicted a field like that.”

Juptier magnetic full.

Image credits

The lop-sided nature of Jupiter’s magnetic field points to yet-undiscovered processes under the surface. Magnetic fields are the product of churning flows of conductive liquids inside a planet. As the planet rotates, these liquids create magnetic fields — just like a dynamo.

Earth’s ‘dynamo’ is encased by a solid crust; the team believes their results suggest Jupiter’s dynamo lacks this casing. One of the models they propose envisions Jupiter’s core not as a solid, but as a slush — a mixture of rock and ice partially dissolved in liquid metallic hydrogen. Such a structure could create layers that would result in an asymmetrical magnetic field, they explain.

Another possibility would be that helium rains on the planet work to destabilize the field. This scenario, however, fails to satisfactorily explain the asymmetry seen in the magnetic field.

Juno is still orbiting Jupiter and will continue for quite some time. The team hopes to use further observations to better understand the magnetic field they’ve uncovered.

The paper “A complex dynamo inferred from the hemispheric dichotomy of Jupiter’s magnetic field” has been published in the journal Nature.

Earth’s oceans generate a second, tiny, previously-unknown magnetic field, ESA satellites find

As it transits through the skies above, the Moon’s pull on the ocean’s salty depths generates a second, if much weaker, global magnetic field.

The ebb and flow of salty water, caused by our Moon’s gravitational pull, can induce their own magnetic field — one which a trio of European Space Agency’s (ESA) satellites has mapped in exquisite detail.

Known as “Swarm”, the trio of satellites was blasted off into orbit back in 2013 to help us better understand the planet’s magnetic field. Most of that field is produced by the churnings of molten iron in the Earth’s core, functioning like a massive underground dynamo. There are other secondary effects, however, such as those produced by human activity — and those are the effects Swarm was intended to peer into.

Imagine the surprise among ESA’s researchers when the satellites stumbled into a whole new magnetic phenomenon.

“It’s a really tiny magnetic field. It’s about 2-2.5 nanotesla at satellite altitude, which is about 20,000 times weaker than the Earth’s global magnetic field,” Nils Olsen, from the Technical University of Denmark, told BBC News.

What set the satellite trio apart from its peers — and enabled this discovery — is the way they ‘see’ water. Other devices we’ve sent in orbit record tides as a change in sea-surface height, but Swarm’s magnetic instruments view the movements of the entire column of water, all the way down to the seabed.

Water is diamagnetic, meaning that it has weak magnetic qualities when a magnetic field is applied to it. However, adding salt reduces its diamagnetism but makes it a good, but not great, electrical conductor — meaning it will start interacting with magnetic fields, relatively weakly. Still, oceans house humongous quantities of water, and as tides cycle around ocean basins, the overall effect is enough to ‘pull’ the geomagnetic field lines along. The interaction between saltwater and the Earth’s magnetic field also generates electrical currents, which, in turn, induce their own magnetic signals.

Studying the ebb and flow of this second magnetic field can let us peer into the movement of deep bodies of water. Oceans capture, store, and move a lot of heat around, and Swarm’s findings could help researchers build better models of Earth’s systems — particularly useful in understanding the effects of climate change.

The magnetic signature of the tides causes a “weak magnetic response” deep below the sea, Olson explained — which could allow us to peer into the electrical goings-on of our planet’s lithosphere and upper mantle. Such data will help us better map these structures, as well as the tectonic activity that drives earthquakes and volcanic eruptions.

“Since oceans absorb heat from the air, tracking how this heat is being distributed and stored, particularly at depth, is important for understanding our changing climate,” Olson said in a statement, adding that the discovery “gives us a truly global picture of how the ocean flows at all depths.”

The professor was speaking at the European Geosciences Union General Assembly (EGU) in Vienna, Austria, where a clutch of new Swarm results have been released.

Why Australia’s biggest oil discovery in 30 years doesn’t matter

Apache claims to have found the biggest oil field in 30 years. Image credit: Apache.

I was reading this morning how excited some journalists were in reporting “the biggest oil discovery in decades”, and I got a little curios: how big is it? According to US oil company Apache, the field could have potentially up to 300 million barrels of oil in place – Australia gets a lot of oil, stock prices for Apache surge, nobody in Australia cares about global warming anymore, so everybody wins, right? But when you start to dissect things and put them into perspective, you see that things aren’t quite as good as Australia and Apache are making them seem.

Volleyballs and ping pong balls – Peak Oil is upon us

First of all, these are claims from Apache following prospection. It’s an estimate, and generally, these estimates tend to be optimistic. It could be the other way around and the field could be even richer, but that’s highly unlikely. If anything, history has taught us that oil companies tend to overestimate initial findings. Second of all, you never ever take all the oil out – it’s simply not possible. A pretty good extraction rate is 50%, while 60% is about as good as it gets. So let’s assume that you do have 300 million barrels of oil – optimistically, you’ll take out some 180 million. The average global daily consumption is 90 million barrels, and the annual Australian consumption is over 1 million barrels, so if somehow, magically extract all the oil tomorrow, you can power the entire world for 2 days, or Australia for almost half a year. That’s really good, that’s a huge figure and all the companies working on it will make billions in profit – but in the global picture, it doesn’t matter that much.

If you want to get a good sense of scale, here’s a good analogy: think of the world as a giant beach, and oil fields as volley balls and ping pong balls. Volley balls are bigger and much easier to spot, so you find those first. But after you do find them, you’ve got to focus on the ping pong balls – much harder to find, much harder to extract, and much smaller; this is exactly the case with oil fields at the moment. There are over 40,000 oil fields in the world right now, but 1,500 of them have 94% of all the oil! That means that under 4% of all the oil fields have 94% of all the oil in the world! Hey, and it all makes sense when you look at the biggest oil fields – the Ghawar Field in Saudi Arabia and the Burgan Field in Kuwait have over 70 billion barrels of recoverable oil! In total, they each have well over 150 billion barrels, so they’re about 500 times larger than the Australian find. As a matter of fact, an oil field is only considered a “volleyball” if it has over 1 billion barrels, so even by the most optimistic estimates, it’s not even close – so why are people so excited about this find?

“You are here”. Image source.

The thing is, there’s one aspect in which the volleyball analogy doesn’t do justice to reality – it only gives a sense of relative scale. The truth is, even ping pong balls have huge economic value. Again, we’re talking about billions of dollars in profit, and that’s not even all of it. Pretty soon we will reach (if we haven’t already) peak oil. Peak oil is the point in time when the maximum rate of petroleum extraction is reached, after which the rate of production is expected to enter terminal decline. Every oil field has its own peak oil, and of course, you can discuss the same concept at the global scale, so finding new reserves is harder and harder – and will become even more so in the near future.

Tony Abbott’s Australia – an environmental disaster

Australia’s PM will definitely be thrilled about the find. Image via Huffington Post.

I couldn’t possibly discuss Australian energy without mentioning the anti-scientific and anti-environmental measures taken by prime minister Tony Abbott. Usually, I tend to avoid discussing politics, because it’s a complicated subject, one in which I’m not very knowledgeable and in which it’s often hard to reach a consensus. But you see, Tony Abbott has antagonized himself to such a degree that I want to talk about him. As a European, the first time I really paid attention to him was in 2011, when he demonized climate action as “socialism”; that’s right, he even went as far as describing carbon price as “socialism masquerading as environmentalism“, something which he proceeded to repeat several times at various meetings. But in 2012, he really made things happen: he pushed forth an initiative to remove the carbon tax, making Australia not just the only country to ever abolish a carbon tax, but the only developed country without a carbon tax! He subsequently removed funding from environmental research, renewable energy, and science all around. Basically, he believes that science funding is not a necessity, but rather an unneeded whim, or even an obstacle. Because the truth is, the science disapproves with him – and like any other self-respecting tyrant, he is trying to remove any opposition.

But as the old saying goes, if you want to find out how things really are, you should follow the money; and a new article in the Guardian reports that Tony Abbott’s push to ditch renewables could hand coal and gas industry $10bn, basically scrapping Australia’s renewable sector, even though Australia could, realistically go 100% renewable in 10 years and wind power is already cheaper than fossil fuels there.

“We have to accept that in the changed circumstances of today, the renewable energy target is causing pretty significant price pressure in the system and we ought to be an affordable energy superpower … cheap energy ought to be one of our comparative advantages,” the prime minister said last year.

However, studies have clearly shown, as the Guardian explains, that “reducing the Renewable Energy Target would not cause power bills to fall and may make them rise in the longer term”. Shifting 10 billions from one eco-friendly, sustainable and growing industry to a declining, polluting industry with ever growing prices does indeed seem like a bad idea.

Other things that mister Abbott has done in his anti-progress crusade is speak against gay marriage and gay relationships in general, try to close the borders to immigrants as much as possible and prevent the creation of any new Natural Parks, saying that he believes  ‘[wood] loggers are the ultimate conservationists‘. Seriously, it’s like he’s trying to become a cartoonishly evil character. But hey, don’t take it from me – here he is getting owned by a bunch of smart highschool students.