The Magnetic Field of Earth's Core: What is the Source?

[stedwards]

1) Is there any evidence that the Earth's magnetic field originates in the core rather than elsewhere?

2) Is there a compelling physical model?

 

[SteamKing]

1) Is there any evidence that the Earth's magnetic field originates in the core rather than elsewhere?

What, you mean like Cincinnati?

2) Is there a compelling physical model?

Yes, there is.

http://en.wikipedia.org/wiki/Earth's_magnetic_field

 

[stedwards]

What, you mean like Cincinnati?

Yes, there is.

http://en.wikipedia.org/wiki/Earth's_magnetic_field

Where?

 

[SteamKing]

If you don't want to read the links, no one can help you.

 

[Ophiolite]

If you don't want to read the links, no one can help you.

I got the impression he was asking "where" Cincinatti was, as a humorous riposte to that portion of Steam King's post.

 

[davenn]

I got the impression he was asking "where" Cincinatti was, as a humorous riposte to that portion of Steam King's post.

LOL
No, I took it the same way Steamking did ... suspecting that the OP didn't see or understand the clickable link

 

[rootone]

Oh well, here it is again.
http://en.wikipedia.org/wiki/Earth's_magnetic_field
The answer to the OP questions are yes and yes.

 

[stedwards]

The parent Wikipedia article on the predominant theory on the origin of the Earth’s magnetic field is http://en.wikipedia.org/wiki/Dynamo_theory cut-and-paste, in part, into the Wikipedia article on the Earth’s Magnetic Field.Upwelling matter from the core is (quazi-) organized into rotating structures called Tylor Columns due to coriolis force.

1)Presumably, these structures are a source or electrical current loops generating a magnetic field. Perhaps this is enough explanation for most.

2)The means by which some mechanism could be responsible for separation of charge carriers in relative motion is not addressed. Take a cylinder of iron and spin it about its axis and it does not generate a magnetic field, obviously. Can anyone supply an explanation?

3) In combination, The Maxwell-Faraday law of induction and the Lorentz force obtain \nabla \times v \times B = -\frac{dB}{dt}. This doesn’t match the equation given by Wikipedia where there is an extra term. Where does it come from?

And I don't appreciate the indirect insults by the intellectual pretenders as a means to elevate their self esteem.

Anyone else without an axe to grind?

 

[Ophiolite]

Anyone else without an axe to grind?

Here I am!

But seriously stedwards, perhaps the misunderstanding could have been avoided if you had indicated in your OP that you were knowledgeable about the topic and had some specific reservations you wanted to discuss. As it was, others - myself included, thought the post was from a neophyte who was either too lazy, or too unskilled to do some basic searches.

In the light of your actual position and before we address shortfalls of current theory, it seems you have a notion the field originates somewhere other than the core. Is that correct, and if so where? And how? And are we allowed to discuss alternative theories inside the main fora?

 

[stedwards]

Here I am!

But seriously stedwards, perhaps the misunderstanding could have been avoided if you had indicated in your OP that you were knowledgeable about the topic and had some specific reservations you wanted to discuss. As it was, others - myself included, thought the post was from a neophyte who was either too lazy, or too unskilled to do some basic searches.

In the light of your actual position and before we address shortfalls of current theory, it seems you have a notion the field originates somewhere other than the core. Is that correct, and if so where? And how? And are we allowed to discuss alternative theories inside the main fora?

I am new to this topic. This was the first I hear of Dynamo Theory as a serious concept. It's actually a bunch of contending models with various degrees of fitness to the geological record and projected properties of the outer core material at high pressure.

This supplies the best introduction to the basic idea that I've found. http://abyss.uoregon.edu/~js/glossary/dynamo_effect.html

 

[Dotini]

1) Is there any evidence that the Earth's magnetic field originates in the core rather than elsewhere?

2) Is there a compelling physical model?

Here is some, really very little, experimental evidence that Earth's magnetic field originated elsewhere, and is merely amplified with the core.
http://www.voanews.com/content/scientists-take-on-eath-s-magnetic-field/2870542.html

 

[Dotini]

https://cosmosmagazine.com/earth-sciences/rocks-hold-records-Earth's-ancient-magnetic-history
The history of the Earth’s magnetic field is indelibly written in vortex-like structures inside grains of the iron oxide magnetite, a new study has shown. ...a detailed picture of the evolution of the Earth's magnetic field could improve our understanding of the planet’s core and plate tectonics.

https://static1.cosmosmagazine.com/sites/default/files/styles/cosmos_body_full/public/280416_magnetichistory_1.jpg?itok=ZzBwsywQ A visualisation of the thermomagnetic behaviour of a small grain of magnetite. Image A shows an electron microscopic image of the grain, while the other images are Magnetic induction maps reconstructed from holograms taken at various temperatures.

 

[Dotini]

From today's edition of spaceweather.com:

European Space Agency's constellation of Swarm satellites reveals that changes may be happening even faster than previously thought. In this map, blue depicts where Earth's magnetic field is weak and red shows regions where it is strong:

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 occurred over the relatively brief period between 1999 and mid-2016.

http://www.esa.int/Our_Activities/Observing_the_Earth/Swarm/Earth_s_magnetic_heartbeat
The magnetic field is thought to be produced largely by an ocean of molten, swirling liquid iron that makes up our planet’s outer core, 3000 km under our feet. Acting like the spinning conductor in a bicycle dynamo, it generates electrical currents and thus the continuously changing electromagnetic field.

It is thought that accelerations in field strength are related to changes in how this liquid iron flows and oscillates in the outer core.

Chris Finlay, senior scientist at DTU Space in Denmark, said, “Swarm data are now enabling us to map detailed changes in Earth's magnetic field, not just at Earth's surface but also down at the edge of its source region in the core.

“Unexpectedly, we are finding rapid localised field changes that seem to be a result of accelerations of liquid metal flowing within the core.”

 

[Alisdair]

Nice piece. I have asked a question regarding these things in another thread. Please follow the link and remember I'm a think Northerner when reading.

https://www.physicsforums.com/threads/generation-of-magnetic-fields.871492/

If you have any answers or can provide the references mentioned I'd be grateful for a comment.

Thanks,
Alisdair

 

[jim hardy]

If one takes a thin spherical shell of charge and sets it into rotation
does a magnetic field result ?
Apparently it does
http://www.physics.princeton.edu/~mcdonald/examples/rotatingshell.pdf
gives equations for it
and so do these
http://www.physicspages.com/2013/04/07/magnetic-field-of-rotating-sphere-of-charge/
http://www.physicspages.com/2013/04/11/magnetic-dipole-moment-of-spinning-spherical-shell/

What happens if, as in a simplified Earth's atmosphere
two concentric spherical shells of charge are separated by 50 km
and there's an E-field between the shells , Earth's is a few hundred volts per meter
and the shells rotate rotate in lockstep

1. Does a magnetic field result?

2. Is it in same direction as Earth's?

www.esa.int/Our_Activities/Observing_the_Earth/Swarm/Magnetic_complexity_begins_to_untangle
Swarm is tasked with measuring and untangling the different magnetic signals that stem from Earth’s core, mantle, crust, oceans, ionosphere and magnetosphere – an undertaking that will take at least four years to complete.

In doing so, the mission will provide insight into many natural processes, from those occurring deep inside the planet through to weather in space caused by solar activity. In turn, this information will yield a better understanding of why the magnetic field is weakening.

might there be more going on up there than we think?

 

[Lyon]

Very Interesting.

 

[Alisdair]

If one takes a thin spherical shell of charge and sets it into rotation
does a magnetic field result ?
Apparently it does

What happens if, as in a simplified Earth's atmosphere
two concentric spherical shells of charge are separated by 50 km
and there's an E-field between the shells , Earth's is a few hundred volts per meter
and the shells rotate rotate in lockstep

1. Does a magnetic field result?

2. Is it in same direction as Earth's?
might there be more going on up there than we think?

Really nice post Jim.
I had a look at those links you posted and pretty quickly found myself out of my depth... but as you're a smart cookie and appear to have time on your hands enough to post here I thought I'd ask...

If angular momentum changes then the intensity of the magnetic field would change? ...and if there were precessional changes which alter angular momentum would this cause a pole excursion in the field?
For example, if the surface of the sphere was heavier on one part of its surface and this caused a "blip" in rotation. Imagine an LP rotating on a record player and the label is off centre and transpose into 3D.

The reason I ask is that I read further up the thread..

Upwelling matter from the core is (quazi-) organized into rotating structures called Tylor Columns due to coriolis force.

In the case of the Earth's magnetic field would variations in the Earth's orbital characteristics and its wobble on its axis have any effect on the magnetic field orientation and intensity?

Apologies if any of this is badly written, ill explained or confusing... I love science but I'm not very clever, and if you have to ask a good question to get a good answer then I'm under no illusions about how this may be received.

My next question, depending on any answers which may be coming, would be regarding how a mass transfer of weight (ice) from the Arctic to the Antarctic might affect the Earth's orientation in space... does it wobble more or differently?

 

[rootone]

I'd say that the effects of doing this on the Earth's rotation would be minimal as the arctic ice cover is really quite a thin layer compared to the bulk of most of the Earth's radius.
Maybe if you moved the landmasses of Canada, Greenland, Scandinavia, and parts of Siberia along with the ice, well maybe.

 

[Alisdair]

Food for thought...

Are there connections between the Earth's magnetic field and climate? https://www.researchgate.net/publication/222817231_Are_there_connections_between_the_Earth's_magnetic_field_and_climate

 

[jim hardy]

Really nice post Jim.
I had a look at those links you posted and pretty quickly found myself out of my depth... but as you're a smart cookie and appear to have time on your hands enough to post here I thought I'd ask...

Thanks for the kind words Alisdair
but
i too was quickly out of my depth
So in this thread I'm a noob .

i posted the question just to explore the concept

I've always (since high school) been suspect of the "Earth as a Dynamo" article from 1958

Elsasser developed his dynamo theory in 1920's . I've never heard an alternative, and perhaps for good reason.
What will those satellites find ?

I am no geophysicist, but
i think the iron and nickel in Earth's mantle is hotter than its Curie temperature. That means it's effectively not ferromagnetic. Not magnetic at all, in fact.
If that's so, it seems natural that Earth's driving mmf likely originates someplace else.

No personal theories on pf, so i'll tinker with that spherical shell calculation next insomnia attack.
Here's a history of the ideas about Earth's field
http://www.phy6.org/earthmag/dynamos2.htm
everybody seems to look inside not outside.

Food for thought...

Are there connections between the Earth's magnetic field and climate? https://www.researchgate.net/publication/222817231_Are_there_connections_between_the_Earth's_magnetic_field_and_climate

Well, i just finished a fascinating book "The Sun Kings", history of solar astronomy and our observations of Earth's magnetic field.
https://www.amazon.com/dp/0691141266/?tag=pfamazon01-20
It tells how we have slowly come to appreciate the weather links between sun and Earth and magnetism's role.
Last chapter explains how sun's magnetic field affects Earth weather through cloud formation,
The researchers cited say sun's magnetic field modulates cosmic rays by ~12% which modulates Earth's cloud cover by 4 or 5 percent . Interestingly, they tied that to Maunder and Sporer and i think Oort minima by tree rings and ice core samples..

Cloud cover obviously affects albedo.
I'd say it's logical to think maybe Earth's own field does some modulating too.

Check out Nasa's SOHO page
http://sohowww.nascom.nasa.gov/

if you find a page for those satellites watching Earth's magnetic field please post link.

old jim

 

[Baluncore]

Atmospheric mass redistribution result in very slight annual changes to the speed of rotation of the Earth. The seasonal variational in the mass of snowfall is part of that process. Most ice in the Arctic is floating so it makes little difference to the mass distribution. Longer term changes in the Antarctic or Greenland icecaps may result in a slight axial change but it is not going to do much to the magnetic field from the core.

everybody seems to look inside not outside.

I think it a mistake to think of the core as an immediate field generator. The Earth must contain a historical collection of magnetic fields, interlocked with circulating electric currents, on and in the conductive core. It takes a long time for things that big and conductive to change. Even if it did not generate the field, the core would be a good place to store a field. I think we need to keep an open mind rather than hang our hat on anyone simple theory.

What happens if, as in a simplified Earth's atmosphere
two concentric spherical shells of charge are separated by 50 km
and there's an E-field between the shells , Earth's is a few hundred volts per meter
and the shells rotate rotate in lockstep
1. Does a magnetic field result?
2. Is it in same direction as Earth's?

We can try to apply magnetohydrodynamics (MHD) to the atmosphere.

Simply put, there is a magnetic field from a N magnet pole in the Antarctic where the penguins are, to a S magnet pole in the Arctic where the bears are. (Remember that a North magnet pole is one that seeks the North of the Earth, so the Earth's Arctic must actually be a S magnet pole).

There is also a dominant West to East atmospheric circulation. There are also four jet streams flowing from West to East at speeds of a few hundred km/hr. Those streams are driven by Earth rotation. https://en.wikipedia.org/wiki/Jet_stream

Now imagine embedding a dust or pollen particle in the atmosphere, then ionise it with UV radiation from sunlight. That will provide a supply of ions. Man-made dust and pollen released by farming practices along with smoke pollution from industrial regions will also provide particles for ionisation.

The force due to the cross product of the moving ions in the atmosphere, by the Earth's magnetic field, will tend to move free electrons and negative ions downwards while it lifts positive ions. That will tend to sort the charges and is consistent with the polarity of the Earth electric field. Over time the polarity of Earth-Ionosphere charge will be reinforced with more positive charges being concentrated in the ionosphere, while electrons end up on the Earth's surface. At some point we can expect a “sprite like” dielectric breakdown of the atmosphere that will limit the voltage gradient. https://en.wikipedia.org/wiki/Sprite_(lightning)

Such an atmospheric MHD charge pump may be sufficient to provide the electrification needed for thunderstorms. When MHD is considered, there seems to be less requirement for graupel collisions in thunderheads to explain the electrification of the atmosphere.

What are the implications of such an MHD interaction? We must expect both generator and motor effects from atmospheric MHD. Rain falling through the stationary cloud base can be expected to fall diagonally due to the charge on the nuclei that seeded the falling drops. We can also expect a slight deflection of the Earth magnetic field due to the mass of atmosphere being deflected as the distributed charge moves.

If the direction of the Earth's magnetic field and the polarity of the ionosphere is intimately linked by MHD through the jetstreams and general atmospheric circulation, how could we possibly test such an effect?
If the magnetic field was to reverse, would we see a reversal of Earth-Ionosphere electric polarity? Could the positive ions fall to Earth while electrons rise to the ionosphere? That might significantly change the availability of nuclei for rain drop formation. We could look for historical precipitation evidence. By drilling deep into the Antarctic icecap we could look at rates of precipitation around the time of the last magnetic change, about 800k years ago. Unfortunately the deepest holes drilled so far hit rock at about that time, so do not reveal the data needed to test such a reversal hypothesis. There is a search under way in the Antarctic for ice cores that go back to one million years. If such cores are found there will then be evidence. If such cores are not found then we have two obvious possibilities; evidence is lost because the weight of accumulated ice is sufficient to melt the base of the icecap where it contacts the rock, and/or ice did not start to accumulate in the Antarctic until the last magnetic reversal. The climate implications of such a magnetic reversal effect, if it occurred, could be very significant. We need data. Might rainforests change places with deserts?

might there be more going on up there than we think?

I do not expect Earth's magnetic field to be induced and accumulated in the core by the motion of atmospheric charge, but it is certainly coupled to some extent.

Yes, there is more going on than is admitted in the simple theories. This is a field of science that is ripe for exploration.

 

[Alisdair]

Thanks for the kind words Alisdair...

...if you find a page for those satellites watching Earth's magnetic field please post link.

old jim

You're welcome Jim and thanks for the links. It'll take me a while to get through that lot.

If I come across a, decent, page on the swarm I'll post it as requested.

Have a good day.
Alisdair

 

[Alisdair]

Atmospheric mass redistribution result in very slight annual changes to the speed of rotation of the Earth. The seasonal variational in the mass of snowfall is part of that process. Most ice in the Arctic is floating so it makes little difference to the mass distribution. Longer term changes in the Antarctic or Greenland icecaps may result in a slight axial change but it is not going to do much to the magnetic field from the core.
I do not expect Earth's magnetic field to be induced and accumulated in the core by the motion of atmospheric charge, but it is certainly coupled to some extent.

Yes, there is more going on than is admitted in the simple theories. This is a field of science that is ripe for exploration.

I really like your idea about an atmospherically generated gmf.

With regards the slight changes in Earth's orientation or speed change or similar I was thinking along the lines of the resultant Coriolis Force and how this might affect outer core liquid metal flow and in turn, magnetic field lines.

In my head I imagine it like a bicycle wheel with a dint in it (in 3D). The wheel rotates normally until the dint then it pitches over slightly, wobbles,and then returns to typical rotation. The dint in this case could be shifting ice or land mass and may not have to be that big to cause a small variation.

Would magnetic field lines move if this wobble caused anomalous Coriolis Force which then induced a temporary and minute change in the flow direction of the liquid metal in the outer core? Could then repeated wobbles with corresponding changes in direction flow create a geomagnetic excursion?

Could motion of other planetary bodies and the moon, in immediate proximity, have a gravitational effect on the liquid metal outer core and induce minor changes in flow direction which result in an excursion? Could these then fluctuate based on the proximity of other planets?

Alternatively, with Baluncore's idea on atmospheric gmf generation could the same impacts be felt on the atmosphere the same way they're undergone by the oceans?

I hope I'm not coming off sounding too daft. I've got an idea in my head and can't let it go. I'm keen for feedback and will do the reading in the next couple of days. Seems I've asked one question and come up with eight more...

 

[Baluncore]

I really like your idea about an atmospherically generated gmf.

I do not believe that is the case. I believe that the atmosphere is effected by the magnetic field.

With regards the slight changes in Earth's orientation or speed change or similar I was thinking along the lines of the resultant Coriolis Force and how this might affect outer core liquid metal flow and in turn, magnetic field lines.

The coriolis force is massive compared with the few milliseconds variation in the length of a year. It will swamp the variation.

Would magnetic field lines move if this wobble caused anomalous Coriolis Force which then induced a temporary and minute change in the flow direction of the liquid metal in the outer core? Could then repeated wobbles with corresponding changes in direction flow create a geomagnetic excursion?

No. The Earth spins on its axis that passes through it's centre of mass. There is no wobble that could be amplified by rotation.

Could motion of other planetary bodies and the moon, in immediate proximity, have a gravitational effect on the liquid metal outer core and induce minor changes in flow direction which result in an excursion? Could these then fluctuate based on the proximity of other planets?

The tidal effects of the Moon and Sun effect the Earth's figure as well as the water on the surface. Distortion of the Earth by about one meter at the surface is unlikely to have any effect on the core or the magnetic field. Planets will have no effect whatsoever.
Solar flares generate much greater electric currents in the surface of the Earth. Those fields are able to shut down power distribution systems and sometimes make compasses point the wrong way for a short while.

Alternatively, with Baluncore's idea on atmospheric gmf generation could the same impacts be felt on the atmosphere the same way they're undergone by the oceans?

I do not believe the atmosphere generates the field. What have the oceans got to do with it?

I do not expect Earth's magnetic field to be induced and accumulated in the core by the motion of atmospheric charge, but it is certainly coupled to some extent.

 

[Dotini]

I really like your idea about an atmospherically generated gmf.

According to the following resource, about 10% of Earth's surface magnetic field is is due to atmospheric processes.

http://www.albany.edu/faculty/rgk/atm101/magnet.htm
Basics

• Earth acts like a bar magnet (which is slightly off axis of its rotational axis) with its south pole directed at Canada and its north pole at Antarctica.
  Location of the magnetic dip poles.
• The magnetic field at the surface of the Earth is largely determined by processes within Earth's core. The field generated by these processes is called the Main Field.
• However, about 10% of the surface magnetic field is due to processes in Earth's atmosphere. This contribution is called the External Field.
• Charge particles (electrons and ions) can simultaneously undergo three types of motion as a result of Earth's magnetic field.
  • gyration: circular motion or cyclotron motion [on the order of thousandths of seconds (milliseconds)]
    
  • latitudinal oscillation: bounce or mirroring between the poles [on the order of seconds]
    
  • longitudinal drift: revolution around the Earth [on the order of hours]
  http://vanallenprobes.jhuapl.edu/gallery/animations/visualization/ParticleMotionMovie2012.mov with all three types combined.
• Moving charged particles (electrical currents) generate magnetic fields
• Note: moving electrons usually determine the direction of an electrical current, but by convention, the direction of the electrical current is in the direction opposite to the flow of electrons

Additional resources of great interest related to the SWARM mission discoveries:
http://www.nasa.gov/feature/goddard...-probes-revolutionize-view-of-radiation-belts
http://www.nasa.gov/content/goddard/van-allen-probes-spot-impenetrable-barrier-in-space
http://www.nasa.gov/content/goddard/van-allen-probes-reveal-zebra-stripes-in-space
http://www.nasa.gov/content/goddard/van-allen-probes-observations-improve-space-weather-models
http://www.nasa.gov/content/goddard/van-allen-probes-find-source-of-fast-particles
https://physics.aps.org/featured-article-pdf/10.1103/PhysRevLett.111.235002

 

[jim hardy]

Thanks Dotini
now i have plenty to read this weekend !

Found a nice worked example of a spherical wound inductor
http://web.mit.edu/6.013_book/www/chapter8/8.5.html
example 8.5.1

Still struggling with "Magnetic Potential" and "Ψ"

they actually built and measured one.

ttfn

old jim

 

[Hornbein]

Take a cylinder of iron and spin it about its axis and it does not generate a magnetic field, obviously.

This baffles me too, and I'm not going to look it up right now. The idea is that the rotating charged particles amplify an existing external magnetic field. For some reason this is more effective with very large objects like planets. It wasn't until the 21st century that a model of a geodynamo was built. It is a rotating drum of liquid sodium. The materials have to meet a certain condition called the magnetic Reynolds number or something like that. It's at the University of Maryland.

To have a magnetic field a heavenly body needs to contain conductive mobile material: liquid, plasma, or gas. (Or have a magnetic field frozen in, something I don't understand.) I'd like to see the math, but I'm busy right now. I'm sure it is out there somewhere.

Another wrinkle is that heavenly bodies with magnetic fields always have toroidal and poloidal fields. The Earth's toroidal field is beneath the surface.

 

[Dotini]

According to the following resource, about 10% of Earth's surface magnetic field is is due to atmospheric processes.

http://www.albany.edu/faculty/rgk/atm101/magnet.htm
...about 10% of the surface magnetic field is due to processes in Earth's atmosphere. This contribution is called the External Field.

Thinking about this process for just a minute:
The Earth is negatively charged.
The atmosphere is positively charged.
An electric field exists above the Earth, with both vertical and lateral gradients.
The strength of the field is higher in the day than the night.
As night turns to day, a gentle trade wind blows east to west.
As day turns to night, a stronger jet stream wind blows west to east.
The Earth spins from west to east.
The jet stream flows from west to east 100-200 mph faster than the Earth spins.
So an electric current will flow in the atmosphere around the Earth.
And a magnetic field will be generated orthogonal to the current.
So maybe the Earth's magnetic field could be partly or even substantially generated by the atmosphere after all.
And maybe even the spin of the Earth is helped along or even maintained by the lateral gradient of the electric field and the blowing of the prevailing wind.

 

[Baluncore]

However, about 10% of the surface magnetic field is due to processes in Earth's atmosphere. This contribution is called the External Field.

I believe that is referring to the upper atmosphere and ionosphere, where solar radiation and ions react with the thin gas of the upper atmosphere.

Thinking about this process for just a minute:

You need to think about it for longer than a minute. Try starting with a whole year of active research.

As night turns to day, a gentle trade wind blows east to west.

The trade winds flow at the surface and are very reliable. They have a seasonal variation but little daily variation. The mass of that much atmosphere is very difficult to speed up or slow down.

As day turns to night, a stronger jet stream wind blows west to east.

There are four jet streams driven by Earth rotation, not by diurnal effects. http://virga.sfsu.edu/pub/jetstream/
For this month I watch these 6 hourly updates; http://virga.sfsu.edu/pub/jetstream/jetstream_sohem/1605/
See if you can find a diurnal effect in these streams.

So maybe the Earth's magnetic field could be partly or even substantially generated by the atmosphere after all.

As the original quote said; a substantial 10% is due to atmospheric effects. Are you suggesting that those effects are somehow built up and accumulated deep in the body of the Earth?

And maybe even the spin of the Earth is helped along or even maintained by the lateral gradient of the electric field and the blowing of the prevailing wind.

Energy in the atmosphere comes from solar radiation and Earth rotation. If the atmosphere circulation is principaly driven by rotation then it will slow Earth down rather than speed it up.

So an electric current will flow in the atmosphere around the Earth.
And a magnetic field will be generated orthogonal to the current.

Yes. And that field will be about 10% of the total.

 

[jim hardy]

Simply put, there is a magnetic field from a N magnet pole in the Antarctic where the penguins are, to a S magnet pole in the Arctic where the bears are. (Remember that a North magnet pole is one that seeks the North of the Earth, so the Earth's Arctic must actually be a S magnet pole).

Negative charge on Earth's surface rotating E to W would place a North pole down South.

Playing around i found an old PF post, https://www.physicsforums.com/threads/finding-the-net-charge-of-the-earth.538741/
in 2011 @Hypnos_16 calculated Earth's surface charge is
q = -6.425e+5
6.425E5 Coulombs in 24 hours is only 7.44 amps
from that MIT link in post #26 (think it's safe to assume MIT uses SI ?)
at North pole, H = NI / 3R
and from above NI = 7.44
and from Wiki R of Earth = ~6.37E6 meters

H = 7.44 / (3 X 6.37E6) = 3.89E-7 amp/meter
Since B = μH
3.89E-7 X μ₀ = 4.89E-13 Tesla = ~ 5 nanogauss ?
eight or nine orders of magnitude too small .

I don't think that's the source.

 

[Baluncore]

...
... eight or nine orders of magnitude too small .

I don't think that's the source.

The charged Earth–Ionosphere capacitor rotates with the Earth. I would expect the charges on the two spherical electrodes to be equal and opposite, so the magnetic effects should significantly cancel.

Rotation of a negatively charged Earth cannot explain the repeated reversals of the Earth's magnetic polarity. That would require a reversal of the polarity of charge on the Earth.

 

[jim hardy]

That would require a reversal of the polarity of charge on the Earth.

Do CME's transport charge ?

 

[Dotini]

@jim hardy

http://www.sciencedirect.com/science/book/9780123978868
Abstract
The supersonic solar wind compresses the magnetic field of the Earth on the sunward side and elongates it in the opposite direction. In the rest frame of the planet, about 1 million volts are generated across the 20 Re cross section of the magnetosphere. The electrical interaction efficiency with the Earth depends on the interplanetary magnetic field (IMF) geometry. When the IMF is oppositely directed to the earth’s magnetic field at the subsolar point, about 10% of this voltage enters the magnetosphere and powers all known magnetospheric processes, including the aurora, energizing most of the radiation belts, magnetic storms, million-ampere currents in the auroral zone, atmospheric winds, etc. These phenomena cause several severe space weather processes that impact humanity, including satellite disruption and communication, navigation, and power grid outages. When the magnetic fields are parallel to each other, the energy input drops but, interestingly, new phenomena arise. In this chapter, we discuss these interactions and their associated electric fields.

 

[Dotini]

See if you can find a diurnal effect in these streams.

I found a diurnal effect in the electric field.

 

[Baluncore]

Do CME's transport charge ?

Yes. If they get here a couple of days later, protons and electrons in the solar wind are sorted differently by the Earth's magnetic field. That distorts the field during magnetic storms.

I found a diurnal effect in the electric field.

Atmospheric and ionospheric electric effects; YES. They are due to exposure to sunlight and the solar wind.

As night turns to day, a gentle trade wind blows east to west.
As day turns to night, a stronger jet stream wind blows west to east.

Atmospheric circulation velocity; NO variation.

 

[Dotini]

Atmospheric circulation velocity; NO variation.

So although the jet stream travels 100-200 mph faster than the surface of the Earth, there is said to be no difference in the atmospheric circulation velocity compared to the Earth's rotation velocity, no net movement of the atmosphere west to east relative to the surface?

 

[Baluncore]

So although the jet stream travels 100-200 mph faster than the surface of the Earth, there is said to be no difference in the atmospheric circulation velocity compared to the Earth's rotation velocity, no net movement of the atmosphere west to east relative to the surface?

"there is said". Where do you get that from?

The charge and movement of the troposphere has very little effect on the Earth's magnetic field.
The jet streams only have a small section and form between much larger slower circulation cells.
https://en.wikipedia.org/wiki/Atmospheric_circulation
https://en.wikipedia.org/wiki/Jet_stream

 

[Dotini]

"there is said". Where do you get that from?

That is what I understood you to say. I'm sorry if I have misunderstood you. Does the atmosphere actually circulate faster than the surface? Or does it not, despite the jet stream from west to east?

What I am trying to learn, rather unsuccessfully, is whether (or not) the jet stream produces a net west to east movement of the atmosphere relative to the surface?

 

[Baluncore]

What I am trying to learn, rather unsuccessfully, is whether (or not) the jet stream produces a net west to east movement of the atmosphere relative to the surface?

Then you need to study the atmospheric circulation as a whole. Don't jump to conclusions.
Net circulation is irrelevant to Earth magnetism as the atmosphere has close to a net neutral charge.

 

[Dotini]

Then you need to study the atmospheric circulation as a whole. Don't jump to conclusions.
Net circulation is irrelevant to Earth magnetism as the atmosphere has close to a net neutral charge.

Yes; the things we understand least we need to study most.

 

[rootone]

Jet streams:
Although these are high velocity winds at altitude, they are just one component of overall atmospheric circulation.
Other atmospheric systems contribute to moving air in the opposite direction with less velocity but in greater volume.
The net effect for the atmosphere as a whole is zero movement in relation to the surface, but locally (and including jet steams), there can be a strong bias for winds to blow in a prevailing direction.

There is no connection I know of between atmospheric circulation systems and the Earth's magnetic field.

 

[Dotini]

Other atmospheric systems contribute to moving air in the opposite direction with less velocity but in greater volume.

Could you cite a reference for this, please?

 

[rootone]

Easterly blowing trade winds at the surface are probably the most famous example of established wind patterns which move large volumes of air from east to west.
https://en.wikipedia.org/wiki/Trade_winds

 

[Chronos]

Venus has an induced magnetosphere due to its dense atmosphere, perhaps Earth has a similar contribution to its magnetosphere.

 

[Dotini]

Easterly blowing trade winds at the surface are probably the most famous example of established wind patterns which move large volumes of air from east to west.
https://en.wikipedia.org/wiki/Trade_winds

Thank you for that citation on the trade wind. In reading it, I could find no substantiation of your notion that "The net effect for the atmosphere as a whole is zero movement in relation to the surface," and that the tradewinds move a larger volume of air than the jet streams. On the other hand, I have found numerous references which tend to suggest a net movement west to east. Atmospheric Angular Momentum (AAM) and Length of Day (LOD)

http://onlinelibrary.wiley.com/doi/10.1029/2006RG000213/full

[2] Angular momentum characterizes the rotation of physical systems ranging from the atomic scale to galaxies. In particular, the global angular momentum M of the atmosphere reflects both the rotation tied to that of the Earth and rotation due to the winds. A wealth of data and theories is available to determine the distribution of angular momentum and to provide the reasons for its changes. Attention is restricted in this review to large-scale motions, although angular momentum is also of key importance, say, in hurricanes or tornadoes. The global atmospheric angular momentum is the integral

http://onlinelibrary.wiley.com/store/10.1029/2006RG000213/asset/equation/rog1654-math-0001.gif?v=1&t=ippj8s7t&s=2c2bab9f874ffdbedcaaf572f9d2096c39ec53ce
of the angular momentum

http://onlinelibrary.wiley.com/store/10.1029/2006RG000213/asset/equation/rog1654-math-0002.gif?v=1&t=ippj8s7t&s=518c5825d4839641914d971653bfaf4b0138cb78
per unit volume over the volume V of the Earth's atmosphere. In (2), r is the position vector pointing from the center of the Earth to the volume element dV of density ρ (see Figure 1). It is customary to assume a dry atmosphere because the contribution of the water substance to the total mass of the atmosphere is small. In principle, the density ρ in (2) also contains the water substance in all phases. The rotation of the Earth is represented by its angular velocity Ω with Ω = 2π/d. The relative velocity of the air with respect to this rotation is v and

http://onlinelibrary.wiley.com/store/10.1029/2006RG000213/asset/equation/rog1654-math-0003.gif?v=1&t=ippj8s7t&s=060425d355ced8d7b10839d0ee943b43171d0166
is the absolute velocity.

Figure 1.

• Open in figure viewer
• Download Powerpoint slide

Rotating Earth and the components Miii of the global angular momentum M in the rotating coordinate system with basic vectors ii. The position vector r points to a volume element dV in space, where the unit vectors eλ, eϕ, and er of the local rotating spherical coordinate system are defined.

Hide
Figure 2
Time and zonal mean of the (a) axial wind term [

w3] in 106 Had s and (b) south-north difference of the mass term [

m3] in 105 Had s as a function of height z (km) and latitude. The terms are integrated over zonal annuli of 5° width and 1000 m depth. Data basis is ERA-40 (1958–2001).-----------------------------------------------------------------------

[6] The laws of angular momentum emerged only slowly in fluid mechanics (see Truesdell [1968] for a lucid account). Bernoulli [1747] may have been first to apply angular momentum concepts correctly in a model of the equatorial easterlies. On the other hand, Hadley [1735]used inaccurate arguments concerning angular momentum in his celebrated treatise on trade winds. A historic account is, however, beyond the scope of this article. For our purpose it is sufficient to state that the axial angular momentum cycle of the atmosphere and its link to the rotating Earth via the torques have been a key topic of meteorology at least since the 1950s. Starr [1948], Starr and White [1951], Lorenz [1967], and others worked out the basic features of the atmosphere's axial angular momentum budget (see Oort [1989] and Rosen[1993] for introductions into historical aspects). The review by Oort and Peixoto [1983]describes the mean distribution of the axial angular momentum in the atmosphere, its transports, with particular emphasis on the role of eddies, and the contributions of latitude belts to friction and mountain torques. In general, good agreement is found between observed changes of M3 and those of LOD as predicted by (15) [Rosen, 1993].

 

[rootone]

OK, I will take a look at the various references, and if there is anything I don't understand I will start a new thread to continue the conversation, as atmospheric circulation is not the original topic for this thread.
On the face of it though I cannot see why the atmosphere (as a whole) would have a different net angular velocity than the Earth's surface since this would require a force external to the Earth acting upon the atmosphere (and in a very specific manner), in order to maintain the differential of the (overall) rates of rotation

 

[Dotini]

this would require a force external to the Earth acting upon the atmosphere (and in a very specific manner), in order to maintain the differential of the (overall) rates of rotation

Yes - sunlight!

 

[jim hardy]

as atmospheric circulation is not the original topic for this thread.

we had one last year, see

https://www.physicsforums.com/threads/Earth's-rotation-and-atmosphere.825307/

 

[ulios21]

Well,
The[/PLAIN] https://en.wikipedia.org/wiki/Earth's_magnetic_field has all information for you

 

[Fervent Freyja]

Some very recent work on the topic: The combined effect of precession and convection on the dynamo action