Earths Magnetic Field

On Feb 11, 2:32 pm, "Androcles" wrote:
"sean" wrote in message

...
|
| On Feb 2, 2:04 pm, "Androcles" wrote:
| "sean" wrote in message
|

| | Why do I need brushes in my model.
|
| Why do you need a question mark at the end of that statement?
| You need the brushes to connect the induced current in the coil
| to the rest of the circuit in a normal setup but..
| The circuit in the liquid core I describe is self contained.
| It doesnt need to be connected to itself. For instance in a
| dynamo ,.. does the coil that spins in the magnetic field need to
| be attached to itself ? No. It only needs brushes if you want
| to attach the rotating coil to an outside circuit. THink of the
| earths rotating liquid core as a coil that isnt attached to an
| outside circuit. Why do I need brushes? Im not suggesting the
| current in the core needs to be attached to any circuit outside the
| core.If I did ... THEN I would need brushes. But I dont so I
| dont need to specify brushes.
| | The liquid core is connected
| | to itself.
|
| So is the rotor in an AC induction motor, but the magnetic
| field reverses 50 times a second (60 in the USA). The Earth's
| magnetic field is DC.
| The earths core is not an ac motor nor does it resemble
| one. Whatever gave you that idea.?
| I certainly never said it resembled an AC induction motor.
| | The current flows around it and doesnt need to be
| | connected to anywhere else by brushes .
|
| The problem with that idea is resistance.
| Is the Earth's core a superconductor?
| No. Otherwise the eraths magnetic field would be tremendously
| powerful. Nonetheless it conducts at least on a residual
| basis. We have the observations of the earths field to
| attest to this. AND,.. the observations that a rotating liquid
| metal will without outside input generate an electromagnetic
| field
| | And you havent made it clear why your diagram proves
| | that Lenzs law is incorrect.
|
| http://en.wikipedia.org/wiki/Lenz's_law
| (wiki)..."The direction of the induced current depends on
| whether the north or south pole of the magnet is
| approaching: an approaching north pole will produce an
| anti-clockwise current (from the perspective of the
| magnet), and south pole approaching the coil will produce
| a clockwise current..."
| Yes I concede this point to you although wiki doesnt mention
| that reversing the motion of the conductor still reverses
| the induced magnetic field. Thats the main point my
| model was stating and it still stands.
| And rather than parralel, as Ive suggested previously,
| the liquid core induces a current at right angles to
| its motion. From core to mantle. I think Ill have to
| change my simulation at..
|http://www.youtube.com/watch?v=CiCBrXKIH_0
| To one that has the current direction from core to mantle
| rather than rotating around the core.
| Nonettheless when the direction of the motion reverses the
| induced field still reverses. This is whats observed and means
| my model is still consistent with the observations and with
| Lenz and Fleming.
| I think essentially this is similar to what
| happens in the faraday wheel? The field is at right angles
| to the current and motion. And the motion is at right
| angles to the field and current.
| What earths core shows us and what...R. Monchaux et al
| (Generation of a Magnetic Field by Dynamo Action in a
| Turbulent Flow of Liquid Sodium 2007)...
| confirm is that where a liquid faraday wheel rotates ..the shear
| of the atoms motion across the radius of the rotating liquid
| supplies the induced current which in turn induces the magnetic
| field. In other words a liquid faraday wheel can induce its own
| field as long as force is supplied through rotation,without
| neccesitating an applied external magnetic field. I know
| you wont like this but the fact is that this theoretical premise
| I suggest is confirmed by R Monchaux et al. If I was wrong
| then they would not have observed a roating liquid conductor
| generate and sustain a magnetic field without any external
| applied emf.
| | As far as Im aware an electrical
| | current always flows in the direction of the motion of the magnetic
| | field.
|
| I'll change the batteries in my fridge magnets then. My grocery list
| must be about to fall on the floor, I haven't changed them in years.
| Did I ever say that your permanent magnet wasnt permanent?
| No. You imagine facts .I never even mentioned permanent magnets
| or whether or not they are permanent or not.
| | At least thats what my reference indicates. For instance
| | if you have a solenoid arranged so that it is vertical on a
| | desk. If you then move
|
| Move? What's this about "move"?
| I don't move my fridge magnets very much. When I do
| then I create a small current in the door, but no current
| without movement.
| Exactly as I was saying. If you move your magnet,..
| you create a small current.

First you need a magnet to move.
An atom is essentially a magnet. So when an atom moves past another
atom it must therefore induce a change in the others magnetic field
And vice versa. Move many atoms in the same direction past
a smaller amount that arent moving then one will induce a current
in the latter. The direction of the induced current can be deduced
by refering to flemings law.
The earth displays this in its magnetic field. And researchers
have discovered that any moving fluid conductor when rotated will
induce a current in the rotating fluid conductor itself. Something
you pretend... cannot happen.
You ask me to supply the references?
Heres a few ...
******
By eavesdropping on earthquake vibrations passing through the globe's
innards, seismologists have discovered that Earth's solid core is a
solo dancer, spinning separately from the rest of the planet.

Earth's metallic core consists of a solid iron sphere, about three-
quarters of the size of the moon, sitting within an outer shell of
roiling liquid iron. Hidden beneath 2,600 kilometers of rock, the core
has remained the most cryptic realm of our planet. Some theorists have
argued that electromagnetic forces inside Earth should cause the core
to spin separately from the planet's outer layers. Others have
hypothesized that the core should spin in synchrony with the mantle
and the crust.

Xiaodong Song and Paul G. Richards of the Lamont-Doherty Earth
Observatory in Palisades, N.Y., have found that the inner core rotates
in the same direction as the rest of the planet but about 1 degree per
year faster. They report their observation in the July 18 Nature.

The surface of the core, at its equator, is moving about 20 km per
year relative to the liquid outer core. "That's 100,000 times faster
than the types of motion we normally associate with properties of the
solid Earth," says Richards. In contrast, the continents creep across
Earth's surface at only a few centimeters per year.

Song and Richards embarked on their research after a computer
simulation at Los Alamos (N.M.) National Laboratory predicted that
Earth's core should spin 1 degree to 2 degrees faster per year than
other parts of the planet.

Gary A. Glatzmaier of Los Alamos says he was surprised that Song and
Richards could actually observe the core's rotation. "We were really
excited to hear that they had found this," says Glatzmaier.

The Lamont-Doherty scientists could not have detected the core's
movement without the help of recent discoveries about inner Earth. Ten
years ago, seismologists found that earthquake vibrations passing
through the solid core travel at different speeds, depending on their
direction--a property called anisotropy. Waves go most slowly in the
plane of the equator and most quickly when heading poleward.

In the last 4 years, seismologists have uncovered evidence that the
grain is skewed slightly from an exact north-south alignment. The axis
of anisotropy--corresponding to the fastest direction for seismic
waves--tilts about 10 degrees from Earth's axis of rotation.

Song and Richards realized that this axis of anisotropy, which
currently points toward Siberia, should shift over time if the core
rotates separately. To test the idea, they pulled out old recordings
made in central Alaska of earthquakes that occurred in the South
Atlantic. Some of the seismic waves from the southern quakes passed
through the inner core on their way north. Comparing the old records
with newer earthquake recordings, the scientists determined that
seismic waves now take about 0.3 second less to complete the journey
than they did during the 1960s. This finding suggests that the core
has rotated in a way that speeds seismic waves heading from the South
Atlantic to Alaska.

The Lamont-Doherty scientists and other teams of researchers are now
examining different seismic records to validate the discovery and to
measure the core's rotation with more precision.

"I think this is one of the most exciting things to happen in the last
several years in deep-Earth studies," says Kenneth C. Creager of the
University of Washington in Seattle.
*****



| What makes you think that when
| I say.."a moving magnet induces a current""
| I actually mean .." a moving magnet does not induce
| a current".. ??!

I didn't think it or say it.
What makes you think you can pick yourself up by your bootstraps,
or the Earth's magnetic field is caused by currents which are induced
by the Earth's magnetic field which is caused by currents which cause
the Earth's magnetic field which is caused by currents which cause
the Earth's magnetic field which is caused by currents which cause
the Earth's magnetic field which is caused by currents which cause
the Earth's magnetic field which is caused by currents which cause
the Earth's magnetic field which is caused by currents which cause
the Earth's magnetic field which is caused by currents which cause
the Earth's magnetic field which is caused by currents which cause
the Earth's magnetic field which is caused by currents which cause
the Earth's magnetic field which is caused by currents which cause
the Earth's magnetic field which is caused by currents which cause
the Earth's magnetic field which is caused by currents which cause
the Earth's magnetic field which is caused by currents which cause
the Earth's magnetic field which is caused by currents which cause
the Earth's magnetic field which is caused by currents which cause
the Earth's magnetic field ?
You are trying not to understand on purpose here. The induced current
is
created by the relative motion between the outer part of the liquid
core
and the inner part. Here is a description of the earths inner dynamo
by
another online source . Although they make slightly different
assumptions
about what the exact mechanism is, they still use the assumption that
the inner and outer parts of the liquid core act as a dynamo. Maybe
their description will help you understand how a dynamo mechanism
can be attributed to earths emf....


******
-Gary A. Glatzmaier of the Institute of Geophysics & Planetary
Physics
at Los Alamos National Laboratory is one of the pioneers in modeling
the earth's core provides this response:
"This effect that Roberts and I found in our simulation is analogous
to the way in which a synchronous electric motor works, with the
inner
core acting like the rotor. The jet streams in the fluid outer core
result from thermal and compositional buoyancy forces, Coriolis
forces, pressure gradients and magnetic Lorentz forces. Hence,
the super-rotation of the inner core is really neither a pure
cause nor a pure effect of the magnetic field. The situation is
much more intricate: the inner core rotation, the fluid flow,
the magnetic field, and the thermal and compositional distributions
all have complicated nonlinear feedbacks on one another.

*******

Heres another onlinbe description you may find enlightening...



******
The Dynamo Effect
The simple question "how does the Earth get its magnetic field?"
does not have a simple answer. It does seem clear that the
generation of the magnetic field is linked to the rotation
of the earth, since Venus with a similar iron-core composition
but a 243 Earth-day rotation period does not have a measurable
magnetic field. It certainly seems plausible that it depends
upon the rotation of the fluid metallic iron which makes up a
large portion of the interior, and the rotating conductor model
leads to the term "dynamo effect" or "geodynamo", evoking the
image of an electric generator.
****

My guess is that venus doesnt have a rotating liquid core.
That would explain why it doesnt seem to have a magnetic field.

And heres a description of the fluid rotating conductor experiment
that shows that a rotating conductor can sustain without outside
assistance, a magnetic field. Contrary to what you believe is
possible.I think the term you dont understand is "self
sustaining feedback".
******


Phys. Rev. Lett. 98, 044502
(issue of 26 January 2007)
Title and Authors 30 January 2007
Molten Metal Magnet

VKS Collaboration
Causing a stir. When filled with molten sodium and stirred at up to 26
revolutions per second, this tank generates a magnetic field--similar
to the way the Earth's core creates a field. Previous experiments
controlled the flow more carefully and avoided turbulence, so they
were less like the Earth's core.
The Earth generates a magnetic field from the flow of molten metal in
its core. Lab experiments have generated fields in a similar way, and
in the 26 January Physical Review Letters, researchers report that
they can create the self-sustaining magnetic field even when the flow
is highly turbulent. The new experiment is a more realistic simulation
of Earth's dynamo than previous experiments because the fluid flows
freely in a large tank instead of being channeled into prescribed
patterns with baffles or tubes. The new design should help researchers
better understand the factors that give rise to magnetic fields in
planets and stars.
It's easy to create a magnetic field by using a battery to force an
electric current through a loop of wire. But Earth's core, a rotating
mix of iron and nickel with internal flows driven by the passage of
heat, has no battery and no wires. Instead, it creates magnetism by
means of self-sustaining feedback. Liquid metal moving through a
magnetic field generates a current, similar to that induced in the
moving coil of an electric generator. That current in turn generates
the magnetic field. This "self-generation" mechanism can dramatically
amplify the small, random fields that always exist in magnetic
materials. To do this, though, the flow must be both complex, mixing
up the longitudinal and latitudinal directions, and rapid, "tangling
up" magnetic field lines faster than they can untangle.
To demonstrate self-generation in the lab, two teams in 2000 forced
liquid sodium into complex but non-turbulent flows using physical
barriers that deflected the fluid along precisely defined paths. Now
the French VKS collaboration--which includes the École Normale
Supérieure (ENS) institutes in Paris and Lyon and the Atomic Energy
Commission (CEA) in Saclay--has created a self-generating magnetic
field with a less contrived flow. They placed disks, equipped with
curved vanes, at each end of a half-meter long cylindrical tank filled
with liquid sodium. Rotation of these "propellers" in opposite
directions at up to 26 revolutions per second created a turbulent flow
that generated a magnetic field. The field only appeared when the
propellers were made of iron, which modifies the field near its
surface.
Compared to the previous experiments, "the flow is less constrained
geometrically," says team member Stéphan Fauve of the ENS in Paris,
although he admits it's not as free as in Earth's core or in other
planets, stars, or galaxies with magnetic fields. The spontaneous
field appeared when the average flow speed throughout the liquid was
surprisingly low. Researchers expected a much higher speed would be
needed--perhaps impractically high--because other experiments
suggested that turbulence would increase the "untangling" rate for
field lines and destroy the dynamo effect. (The Earth's dynamo is
turbulent but also operates at a much higher effective speed.) This is
"the first time a magnetic field is self-generated by a fully
turbulent flow with turbulent fluctuations as large as the mean flow,"
says Fauve.
"There is a real advance here," says Cary Forest of the University of
Wisconsin at Madison, who also explores magnetic fields arising in
turbulent sodium flow. But he notes that the turbulent eddies in this
experiment are almost as big as the experimental cell itself, whereas
the eddies of molten metal that give rise to Earth's magnetism are
much smaller than the core. "It would be interesting in the future to
have an experiment where one had turbulence at small scales driving a
magnetic field at large scales," he says.

******

Amazing stuff isnt it? Earth can quite literally pick itself up
by its bootstraps after all,and generate a magnetic field.
In fact its not that magical. Because to create a emf one
only needs force moving a conductor that moves relative to another
conductor to create an emf. As the experiments show in the
reference Ive quoted above.
The force is the earths gravitational slingshot around the
sun and ultimately its own rotation around its own axis. The
different moving conductors are supplied by the liquid core
moving at different relative speeds. Put these together and you have
an emf generated. If you dont believe its possible.. Then explain
why the above french team managed to generate a emf purely from a
rotating liquid conductor without any external input?

| | a magnet south pole first downwards
| | into the top end,. the current in the solenoid
| | flows from top to bottom. The same occurs if the magnet
| | is reversed so that its north pole enters the top end of
| | the solenoid first and moves downwards.
| | But if you move the magnet either north or south pole first
| | upwards from the bottom of the solenoid then the current is
| | reversed in the solenoid. This is what any reference claims
| | is observed. It is this effect that I use to explain
| | how the current is induced in the liquid core.
|
| Yes, but the solenoid doesn't induce any voltage without you
| applying a force to make it move.

| Well Im glad you agree with me now that a moving magnet
| will induce a current.

I've known how generators work since I as a teenager riding
a bicycle with lamps to light.
Same method as the earths core. Except the inner and outer
parts of the liquid core dupicate the moving parts of your
bike lamp generator. And the force in your feet moving the wheels
duplicates the gravitational force from the sun and the earths
force of the earths own mass spinning on its axis.

| So what is the force that rotates the core relative
| to the mantle?

| First of all it is accepted by the scientific
| community that the earths core DOES rotate relative to the mantle

Second of all it is NOT accepted by the scientific community
that the Earth's core rotates relative to the mantle, you made that up.
Next time try google for reference before you pretend I make
things up. Heres a few references that clearly show that it is YOU
who makes things up...

******
1)Recent evidence has suggested that the inner core of Earth may
rotate slightly faster than the rest of the planet.[8] In August 2005
a team of geophysicists announced in the journal Science that,
according to their estimates, Earth's inner core rotates approximately
0.3 to 0.5 degrees per year relative to the rotation of the surface.

2)Xiaodong Song and Paul G. Richards of the Lamont-Doherty Earth
Observatory in Palisades, N.Y., have found that the inner core rotates
in the same direction as the rest of the planet but about 1 degree per
year faster. They report their observation in the July 18 Nature.

The surface of the core, at its equator, is moving about 20 km per
year relative to the liquid outer core. "That's 100,000 times faster
than the types of motion we normally associate with properties of the
solid Earth," says Richards. In contrast, the continents creep across
Earth's surface at only a few centimeters per year.

Song and Richards embarked on their research after a computer
simulation at Los Alamos (N.M.) National Laboratory predicted that
Earth's core should spin 1 degree to 2 degrees faster per year than
other parts of the planet.

Gary A. Glatzmaier of Los Alamos says he was surprised that Song and
Richards could actually observe the core's rotation. "We were really
excited to hear that they had found this," says Glatzmaier.

The Lamont-Doherty scientists could not have detected the core's
movement without the help of recent discoveries about inner Earth. Ten
years ago, seismologists found that earthquake vibrations passing
through the solid core travel at different speeds, depending on their
direction--a property called anisotropy. Waves go most slowly in the
plane of the equator and most quickly when heading poleward.

To explain the differences in speed, researchers proposed that the
iron crystals in the inner core have a distinct orientation, like the
grain in wood. Waves moving along this crystalline grain travel faster
than those going against it.

In the last 4 years, seismologists have uncovered evidence that the
grain is skewed slightly from an exact north-south alignment. The axis
of anisotropy--corresponding to the fastest direction for seismic
waves--tilts about 10 degrees from Earth's axis of rotation.

Song and Richards realized that this axis of anisotropy, which
currently points toward Siberia, should shift over time if the core
rotates separately. To test the idea, they pulled out old recordings
made in central Alaska of earthquakes that occurred in the South
Atlantic. Some of the seismic waves from the southern quakes passed
through the inner core on their way north. Comparing the old records
with newer earthquake recordings, the scientists determined that
seismic waves now take about 0.3 second less to complete the journey
than they did during the 1960s. This finding suggests that the core
has rotated in a way that speeds seismic waves heading from the South
Atlantic to Alaska.

*****


Are you still sure you want to claim that the earths
core doesnt rotate relative to the mantle?
If so then why have the above researchers and many others
decided it does rotate seperately?
What is the force that rotates the core relative to the mantle?

| Ive cited one source in my initial post to clarify that its
| not me imagining this.Here it is again..
| Song, Richards 2005 Check it out on google .

No. Either a give me a specific reference or shut up, I'm
not doing research on songs.
Ive now given you numerous references to show that many researchers
now agree that earths mantle moves relative to its core, that earths
liquid core moves at different relative speeds and that this can
create a dynamo effect that is also observed in labarotory experiment
to spontaneously generate an emf.
| So Ive responded to this observed fact

No you haven't and there is no observed fact. Answer the question.

What is the force that rotates the core relative to the mantle?
The same force that rotates earth around its own axis.
Sean
www.gammarayburst.com
http://www.youtube.com/watch?v=CiCBrXKIH_0
http://www.youtube.com/profile?user=jaymoseleygrb