Tag: magnetic field

Scientists better constrain time frame of Mars’ active dynamo

12:33 pm

Using data from the MAVEN orbiter, scientists have now constrained the time frame when Mars’ dynamo was active and producing a global magnetic field, between 3.7 and 4.5 billion years ago.

Magnetism in certain rocks on Mars’ surface indicate that the Martian dynamo was active between 4.3 and 4.2 billion years ago, but the absence of magnetism over three large basins – Hellas, Argyre, and Isidis – that formed 3.9 billion years ago has led most scientists to believe the dynamo was inactive by that time.

Mittelholz’s team analyzed new data from NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) orbiter and found clear evidence of a magnetic field coming from the Lucus Planum lava flow that formed about 3.7 billion years ago – much later than at other areas studied.

There is of course a lot of uncertainty here.

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North magnetic pole continues its drift

3:52 pm

The uncertainty of science: The newest 2020 version of the World Magnetic Model, released on December 10, 2019, shows that the north magnetic pole is continuing its unprecedented drift eastward and away from the Canadian Arctic.

A new and updated version of the WMM is released every five years. The latest WMM2020 model will extend to 2025.

Since Earth’s magnetic field is created by its moving, molten iron core, its poles aren’t stationary and they wander independently of each other. Since its first formal discovery in 1831, the north magnetic pole has traveled around 1,400 miles (2,250 km). This wandering has been generally quite slow, allowing scientists to keep track of its position fairly easily. Since the turn of the century, this speed has increased.

The WMM2020 forecasts that the northern magnetic pole will continue drifting toward Russia, although at a slowly decreasing speed—down to about 40 km per year compared to the average speed of 55 km over the past twenty years.

Though we know the magnetic field is produced by the magnetism related to the Earth’s molten iron core, scientists do not have a solid understanding of the details, including why the drift of the pole has accelerated this century as well as shifted eastward.

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Earth’s magnetic field undergoing unexpected changes

1:25 pm

The uncertainty of science: For reasons that scientists do not understand, the Earth’s magnetic field has been undergoing unexpected shifts in the past two years, causing its north pole to move significantly and somewhat quickly from Canada across to Siberia.

Earth’s north magnetic pole has been skittering away from Canada and towards Siberia, driven by liquid iron sloshing within the planet’s core. The magnetic pole is moving so quickly that it has forced the world’s geomagnetism experts into a rare move.

On 15 January, they are set to update the World Magnetic Model, which describes the planet’s magnetic field and underlies all modern navigation, from the systems that steer ships at sea to Google Maps on smartphones.

The most recent version of the model came out in 2015 and was supposed to last until 2020 — but the magnetic field is changing so rapidly that researchers have to fix the model now. “The error is increasing all the time,” says Arnaud Chulliat, a geomagnetist at the University of Colorado Boulder and the National Oceanic and Atmospheric Administration’s (NOAA’s) National Centers for Environmental Information.

Note that they have delayed the release of the World Magnetic Model until January 30, claiming the delay is caused by the government shutdown. Seems bogus to me. As I have already noted, these scientists aren’t slaves. If they think this is so important, and they have completed their work (which the article suggests they have), they can release the model, regardless of the federal government’s funding.

Hat tip reader Stephen Taylor.

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Jupiter’s weird magnetic field

11:34 am

New data from Juno has revealed that Jupiter’s magnetic field acts like it has three poles, one at each pole and another near the equator.

If Earth’s magnetic field resembles that of a bar magnet, Jupiter’s field looks like someone took a bar magnet, bent it in half and splayed it at both ends. The field emerges in a broad swath across Jupiter’s northern hemisphere and re-enters the planet both around the south pole and in a concentrated spot just south of the equator, researchers report in the Sept. 6 Nature.

“We were baffled” at the finding, says study coauthor Kimberly Moore, a graduate student at Harvard University.

They think the multiple poles are a result of the complexity of Jupiter’s inner core, which likely does not have the same kind of organization as a rocky terrestrial planet.

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Can the Earth’s magnetic field shut down and flip in only two centuries?

11:49 pm

A new study of a stalagmite in China suggests that the Earth’s magnetic field can reverse polarity in as little as two centuries, not the thousands of years as previously thought.

He and his ANU colleague Dr Xiang Zhao from the Research School of Earth Sciences contributed to the study of the paleomagnetic record from 107,000 to 91,000 years ago that is based on precise magnetic analysis and radiometric dating of a stalagmite from a cave in southwestern China.

The stalagmite, which is one metre in length and eight centimetres in diameter, has a candle-like shape and ranges in colour from yellow to dark brown. “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.

In the past century or so the Earth’s magnetic field has weakened by about 10%. Some scientists think it possible this presages a possible magnetic reversal, which is apparently overdue. However, up until now it was assumed from available data that any reversal would take thousands of years for the magnetic field to shut down and then restart with a flipped polarity. This new data says the shutdown can happen within the span of one human life.

It is unclear to me if this increases our risk or decreases it. The magnetic field acts to protect us from the solar wind and other space radiation. When it shuts down there will be consequences, many negative, that we now can’t even predict. If a reversal is beginning now but takes longer to happen we will have at least a thousand years to plan and adapt, but the period of shut down will be far longer, causing more harm. If it happens quickly we will have to scramble to adapt, but the period of harm will be very short, and thus might not have time to cause significant harm.

Either way, this result is decidedly uncertain, based on a single stalagmite. No one should take it too seriously without further confirmation from other evidence.

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Scientists claim Earth’s magnetic field not about to flip

8:29 am

The uncertainty of science: Using computer models and data from the past two changes in the Earth’s magnetic field, some scientists now claim that the weakening of the magnetic field in the past two centuries does not herald an upcoming flip in polarity.

To calculate the likelihood of a full field switch, Holme and his colleagues looked at the magnetic alignment of rock particles deposited in and before the two most recent excursions – the Laschamp event, approximately 41,000 years ago, and the Lake Mono event, which occurred 34,000 years ago.

The scientists found that the strength of the Earth’s magnetic field several thousand years before the two wobbles – at 49,000 and 46,000 years ago – were pretty much the same as they are now. However, they were accompanied by SAA-style weak areas of much greater magnitude.

This, suggests Holme’s teams, considerably reduces the chances of anything drastic happening now. “There has been speculation that we are about to experience a magnetic polar reversal or excursion,” says Holmes. “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.”

Can I express my skepticism? This research is interesting, but there is no way it could provide enough data for anyone to trust such a prediction. We have zero knowledge of the behavior of the magnetic field during a polarity switch, and to claim that this data gives us enough information to say that we do understand that behavior is an overstatement of stupendous proportions.

Just as we don’t really understand the mechanics of the Sun’s magnetic field, causing it to flip polarity every 11 years, we certainly don’t understand the Earth’s either. The Earth’s magnetic field is going to do what it is going to do, and when it does, we will then maybe get an inkling as to why it does it.

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Uranus’s magnetic field switches on and off daily

9:54 am

Using data from the Voyager 2 flyby of Uranus in 1986, scientists now think that the gas giant’s magnetic field switches on and off each day as the planet rotates.

Uranus’s magnetosphere, in contrast [to Earth], exhibits precise regularity in its mode changes. This, say the researchers, is because it lies at an angle of roughly 60 degrees to the planet’s spin axis, causing its interaction with incoming solar winds to vary dramatically during the 17 hours it takes for a full rotation. “Uranus is a geometric nightmare,” says Paty.

“The magnetic field tumbles very fast, like a child cartwheeling down a hill head over heels. When the magnetised solar wind meets this tumbling field in the right way, it can reconnect and Uranus’s magnetosphere goes from open to closed to open on a daily basis.”

The researchers suggest the robust and regular changes to the magnetosphere may mean that the icy planet has spectacular auroras across its breadth every day.

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Maybe the Earth’s magnetic field is not weakening

3:31 pm

The uncertainty of science: New data using date-stamped jars covering the period from the 8th to the 2nd century BC suggest that the 8th century BC was a period when the Earth’s magnetic field was particularly strong, leading the scientists doing the research to conclude that the Earth’s magnetic field might not be weakening and that the recent field strength decline detected in the past two hundred years might simply be part of the field’s normal fluctuations.

This new data is certainly worthwhile, but the press release surely doesn’t reveal how the scientists were able to extrapolate future magnetic field strength from 8th century BC fluctuations. At a minimum, I would need to see a graph showing the measured field strength from the 8th century BC to the present time to see how today’s field strength compares with the past. Unfortunately, the press release does not provide this.

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Planes flying at high latitudes can travel through clouds of high cosmic radiation

10:14 pm

The uncertainty of science: Researchers have found evidence that suggests that planes flying at higher latitudes can sometimes fly through concentrated pockets of high cosmic radiation.

“We have flown radiation sensors onboard 264 research flights at altitudes as high as 17.3 km (56,700 ft) from 2013 to 2017,” says Kent Tobiska, lead author of the paper and PI of the NASA-supported program Automated Radiation Measurements for Aerospace Safety (ARMAS). “On at least six occasions, our sensors have recorded surges in ionizing radiation that we interpret as analogous to localized clouds.”

…Conventional wisdom says that dose rates should vary smoothly with latitude and longitude and the height of the aircraft. Any changes as a plane navigates airspace should be gradual. Tobiska and colleagues have found something quite different, however: Sometimes dose rates skyrocket for no apparent reason. “We were quite surprised to see this,” says Tobiska.

All of the surges they observed occurred at relatively high latitudes, well above 50 degrees in both hemispheres. One example offered in their paper is typical: On Oct 3, 2015, an NSF/NCAR research aircraft took off from southern Chile and flew south to measure the thickness of the Antarctic ice shelf. Onboard, the ARMAS flight module recorded a 2x increase in ionizing radiation for about 30 minutes while the plane flew 11 km (36,000 feet) over the Antarctic Peninsula. No solar storm was in progress. The plane did not abruptly change direction or altitude. Nevertheless, the ambient radiation environment changed sharply. Similar episodes have occurred off the coast of Washington state.

The theories proposed to explain this at the link are not very convincing, and suggest to me that they really do not know what causes this. All we do know is that it likely associated with the interaction of the Earth’s magnetic field and cosmic radiation.

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The recent changes in Earth’s magnetic field

11:44 am

New data from Europe’s Swarm constellation of satellites detail the recent bigger-than-expected changes that have been occurring in the Earth’s magnetic field.

Data from Swarm, combined with observations from the CHAMP and Ørsted satellites, show clearly that the field has weakened by about 3.5% at high latitudes over North America, while it has strengthened about 2% over Asia. The region where the field is at its weakest – the South Atlantic Anomaly – has moved steadily westward and weakened further by about 2%. These changes have occured over the relatively brief period between 1999 and mid-2016.

It was already known that the field has weakened globally by about 10% since the 19th century. These changes appear to be part of that generally weakening. Some scientists have proposed that this is the beginning of an overall flip of the magnetic field’s polarity, something that happens on average about every 300,000 years and last occurred 780,000 years ago. At the moment, however, we have no idea if this theory is correct.

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Earth’s magnetic field might not be flipping

10:12 pm

The uncertainty of science: A new analysis of the past strength of the Earth’s magnetic field suggests that today’s field is abnormally strong and that, even with the 10% decline in the field’s strength in the past two centuries, it remains stronger than the average over the past 5 million years.

The new data also suggests that the field might not be about to shut down and then reverse polarity, as some scientists have theorized based on the 10% decline. Instead, the data says that the field’s unusual strength today only means that the decline is bringing it back to its average strength, and is not necessarily an indication of a pending reversal.

To put it mildly, there are a lot of uncertainties here, including questions about the database that has been used previously by geologists to estimate the past strength of the Earth’s magnetic field. The database might have been right, but the new study raises significant new questions.

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Magnetic field science satellites launched

9:26 am

An Atlas 5 rocket successfully launched four NASA research satellites Thursday night designed to study the behavior of the Earth and Sun’s magnetic fields at high resolution.

The quartet of observatories is being placed into an oblong orbit stretching tens of thousands of miles into the magnetosphere — nearly halfway to the moon at one point. They will fly in pyramid formation, between 6 miles and 250 miles apart, to provide 3-D views of magnetic reconnection on the smallest of scales.

Magnetic reconnection is what happens when magnetic fields like those around Earth and the sun come together, break apart, then come together again, releasing vast energy. This repeated process drives the aurora, as well as solar storms that can disrupt communications and power on Earth. Data from this two-year mission should help scientists better understand so-called space weather.

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The big solar hotshots of 2013.

11:37 am

The big solar hotshots of 2013.

The article is a nice and visually fascinating overview of the twelve most impressive solar events during the past year. Interestingly, I think #7 is the most significant in that it involved things that didn’t happen.

As small sunspot group NOAA 1838 was falling apart, another active region NOAA 1839 appeared just in time to avoid a spotless day, which would have been the first since 14 August 2011! A spotless day during a solar cycle maximum is not uncommon, but it remains of course a rare event. This absolute low in sunspot number highlighted a period of very low solar activity, with hardly any flares (no C-flares from 7 till 17 September: 11 consecutive days) and no (minor) geomagnetic storms for a full month! Meanwhile, the magnetic field near the solar north pole (finally) completed its reversal, whereas this magnetic flip is still ongoing at the south pole. These reversals testify we’re close to the maximum of solar cycle 24. [emphasis mine]

The phrases in bold clarify where we presently stand with the solar cycle. The southern magnetic field is in the process of reversing, but has not yet completed the flip.

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Astronomers have measured the most powerful magnetic field ever found around a star.

9:02 am

Astronomers have measured the most powerful magnetic field ever found around a star.

The star’s magnetic field is 20,000 times stronger than the Sun’s, and almost 10 times stronger than that detected around any other high-mass star. At about 35 times the Sun’s mass, the O-type star NGC 1624-2 lies in the open star cluster NGC 1624, about 20,000 light-years away in the constellation Perseus.

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When a solar storm slammed into both the Earth and Mars in January 2008, scientists were able to directly measure the importance of the Earth’s magnetic field in protecting our atmosphere from oxygen loss.

9:22 am

When a solar storm slammed into both the Earth and Mars in January 2008, scientists were able to directly measure the importance of the Earth’s magnetic field in protecting our atmosphere from oxygen loss.

They found that while the pressure of the solar wind increased at each planet by similar amounts, the increase in the rate of loss of martian oxygen was ten times that of Earth’s increase. Such a difference would have a dramatic impact over billions of years, leading to large losses of the martian atmosphere, perhaps explaining or at least contributing to its current tenuous state. The result proves the efficacy of Earth’s magnetic field in deflecting the solar wind and protecting our atmosphere.

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An experiment designed to mimic the dynamo at the Earth’s core is about to be turned on.

8:43 am

Mad scientists at their best! An experiment designed to mimic the dynamo at the Earth’s core is about to be turned on.

Ten years in the making, the US$2-million project is nearly ready for its inaugural run. Early next year, the sphere will begin whirling around while loaded with 13,000 kilograms of molten sodium heated to around 105 °C. Researchers hope that the churning, electrically conducting fluid will generate a self-sustaining electromagnetic field that can be poked, prodded and coaxed for clues about Earth’s dynamo, which is generated by the movement of liquid iron in the outer core. If it works, it will be the first time that an experiment that mirrors the configuration of Earth’s interior has managed to recreate such a phenomenon.

This is a really very cool experiment, as we really do not have a good understanding of how planetary magnetic fields are produced.

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A summary of Messenger’s first six months in orbit around Mercury

10:23 am

A summary of Messenger’s first six months in orbit around Mercury.

Though packed with lots of results, this strikes me as the most interesting discovery so far:

Orbital data reveal that Mercury’s magnetic field is offset far to the north of the planet’s center, by nearly 20% of Mercury’s radius. Relative to the planet’s size, this offset is much more than in any other planet, and accounting for it will pose a challenge to theoretical explanations of the field. . . . This finding has several implications for other aspects of Mercury, says Anderson, who co-authored several of the presentations in the MESSENGER session. “This means that the magnetic field in the southern hemisphere should be a lot weaker than it is in the north. At the north geographic pole, the magnetic field should be about 3.5 times stronger than it is at the south geographic pole.

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