Earths Magnetic Field

[peter]

I see no reason to doubt the standard explanation

The Earth has a rotating molten or semi molten Iron Core. It is this rotating Iron core that generates the Magnetic field .

[CharlesChandler]

I see no reason to doubt the standard explanation

The Earth has a rotating molten or semi molten Iron Core. It is this rotating Iron core that generates the Magnetic field .

That's not an explanation.

For a rotating iron core to generate a magnetic field, it has to have a net electric charge. Is there a net electric charge in the standard explanation? No.

For an iron core to generate a magnetic field whose polarity flips every 450,000 years on average, the core would have to do either one of two things: 1) its charge would have to flip polarity, or 2) it would have to start rotating in the opposite direction. The standard explanation doesn't have a charged core, much less one whose electric polarity flips, nor is there any force capable of reversing the rotation.

In short, in order to evaluate the applicability of dynamo theories to geomagnetism, you first have to understand dynamos.

(The same could be said of the study of the Sun's magnetic field, which is twice as strong as the Earth's, and which flips much more regularly -- every 11.2 years.)

[seasmith]

That's not an explanation.

For a rotating iron core to generate a magnetic field, it has to have a net electric … charge

Charles, Sure that's one way, another is if the core is traveling through a (solar-centric) magnetic flux field then electric induction will generate the net electric charge in the spheroid as well as local magnetospherics. Of course you well know, induction is recursive; hence the e and the m in EM.
Just because we have currently a fairly primitive perception of the heliospheres doesn't mean earth isn't spin-orbiting along through a finely charged and highly organized EM/ES flux field, n'est pas ?
∞

[CharlesChandler]

Sure that's one way, another is if the core is traveling through a (solar-centric) magnetic flux field then electric induction will generate the net electric charge in the spheroid as well as local magnetospherics.

I'm not sure that a solar-centric magnetic flux is well-suited for the task. The Parker Spiral (i.e., the "ballerina's skirt") certainly produces a constant flux at any given point within its sphere of influence.

http://upload.wikimedia.org/wikipedia/c ... spiral.gif

Fluxes in the interplanetary magnetic field do induce an electric current in the Earth, called a ""geomagnetically induced current" (GIC). But the fluxes are weak in comparison to the Earth's field. So the interplanetary magnetic field isn't the prime mover.

I think that it's the rotation of the Earth, but with charged double-layers, and with differential rotation, where the layer that is rotating faster generates the dominant field. We know that the core rotates faster than the mantle. If the core has a net charge, it's a dynamo, but only if it has a net charge, which the standard model can't explain.

[seasmith]

CC wrote:

The Parker Spiral (i.e., the "ballerina's skirt") certainly produces a constant flux at any given point within its sphere of influence.

The so-called Parker "spiral" has anything but "constant" (ion/displacement current) flux :

Abstract
...unexpected observations of electron behaviour can be explained by rather dynamic physical conditions in the current sheet, caused by ongoing magnetic reorganizations…

The heliospheric magnetic field (HMF) is the extension of the coronal magnetic field carried out into the solar system by the solar wind. It is the means by which the Sun interacts with planetary magnetospheres and channels charged particles propagating through the heliosphere. As the HMF remains rooted at the solar photosphere as the Sun rotates, the large-scale HMF traces out an Archimedean spiral. This pattern is distorted by the interaction of fast and slow solar wind streams, as well as the interplanetary manifestations of transient solar eruptions called coronal mass ejections. On the smaller scale, the HMF exhibits an array of waves, discontinuities, and turbulence, which give hints to the solar wind formation process. This review aims to summarise observations and theory of the small- and large-scale structure of the HMF. Solar-cycle and cycle-to-cycle evolution of the HMF is discussed in terms of recent spacecraft observations and pre-spaceage proxies for the HMF in geomagnetic and galactic cosmic ray records.

http://solarphysics.livingreviews.org/A ... 5Color.pdf


Note that in prev post, your "differential rotation" view was not in the least discounted, only given some whole-system counterpoise.
It's entirely possible imho, that rotations in the HMF, and within Earth's interiors, may well be part and parcel of the same solarsystem coupling dynamic.
~

[CharlesChandler]

By "constant flux", I meant "constantly changing fields", which induces currents. Anyway...

I'm not ruling out the bigger picture. IMO, the galactic magnetic field is responsible for the axial rotation of the Sun, and for the axial and orbital rotations of the planets. Fluxes in the galactic field are responsible for the precession of some of the axial rotations, where rotation developed in the previous field comes into conflict with the present field, producing the axial force necessary for precession. I just think that the solar fields are in too much flux to be responsible for the semi-steady-state geomagnetic field.

[Solar]

Fluxes in the interplanetary magnetic field do induce an electric current in the Earth, called a ""geomagnetically induced current" (GIC). But the fluxes are weak in comparison to the Earth's field. So the interplanetary magnetic field isn't the prime mover.

I think that it's the rotation of the Earth, but with charged double-layers, and with differential rotation, where the layer that is rotating faster generates the dominant field. We know that the core rotates faster than the mantle. If the core has a net charge, it's a dynamo, but only if it has a net charge, which the standard model can't explain.

Just clarifying here Charles. GIC's refer to currents induced in man made metallic infrastructure such as power grids, pipelines, telephone networks etc. Electric currents induced in/on the Earth are "telluric currents".

[peter]

"For a rotating iron core to generate a magnetic field, it has to have a net electric charge. Is there a net electric charge in the standard explanation? No."

Go and get your self a Iron Bar Magnet - Place a piece of paper over it and sprinkle some iron fillings on the paper. Observer the Magnetic field and tell me where the net electric charge is.

The standard theory is The so called "Dynamo Theory"

Theory has it that magnetic fields tend to arise spontaneously in any rotating, electrically conducting fluid, whether that fluid is the molten iron in the Earth's deep interior or in the multi-million-degree plasma of the Sun. But empirical evidence is much harder to come by, given that no one has yet figured out how to stick a probe into the core of the Earth, or into the heart of a star.

As to The Periodic Reversals of the Earths Field - at one time I thought there might be a correlation between reversals and a large Meteor /Asteroid impacts. But there does not seem to be such a correlation. However a large impact could result in the disruption of the smooth circular flow of the molten core.

Alternatively another proposal is that the Magnetic Drift is caused by the Earths wobble on its rotational axis.
Such a wobble ,especially if it varied over time, could have varying effects of the smooth flow of the molten layers of the Earths core.
A point is reached when the drift becomes extreme and the poles flip. But if I remember correctly modern theory suggests that the reversals are preceded by first a weakening of the field then a period of no field followed by reversal. It has been observed that currently the field is weakening and some belief a reversal is due.

[CharlesChandler]

Go and get your self a Iron Bar Magnet - Place a piece of paper over it and sprinkle some iron fillings on the paper. Observer the Magnetic field and tell me where the net electric charge is.

The Curie temperature of iron is 1043 K, above which ferromagnetism is not possible. The temperature of the core of the Earth has been estimated at over 6000 K, meaning that it is not ferromagnetic. And that means that the geomagnetic field can only be caused by moving electric charges.

Theory has it that magnetic fields tend to arise spontaneously in any rotating, electrically conducting fluid, whether that fluid is the molten iron in the Earth's deep interior or in the multi-million-degree plasma of the Sun.

Has this been tested? An electrically conducting fluid isn't hard to come by, nor would it be difficult to find an apparatus to get it rotating. Flushing a toilet creates rotation in an electrically conducting fluid (i.e., water). Why don't you take a compass with you the next time you need to use the little astronomer's room, and tell me what you find.

As to The Periodic Reversals of the Earths Field - at one time I thought there might be a correlation between reversals and a large Meteor /Asteroid impacts. But there does not seem to be such a correlation. However a large impact could result in the disruption of the smooth circular flow of the molten core.

While you're in the little astronomer's room, see if you can figure out a way of simulating a meteor impact on the rotating conducting fluid in the toilet, and see if the compass needle points in the other direction.

[celeste]

By "constant flux", I meant "constantly changing fields", which induces currents. Anyway...

I'm not ruling out the bigger picture. IMO, the galactic magnetic field is responsible for the axial rotation of the Sun, and for the axial and orbital rotations of the planets. Fluxes in the galactic field are responsible for the precession of some of the axial rotations, where rotation developed in the previous field comes into conflict with the present field, producing the axial force necessary for precession. I just think that the solar fields are in too much flux to be responsible for the semi-steady-state geomagnetic field.

Charles,
Just to clarify, it is not the galactic magnetic field, but the magnetic field right here in the Local chimney/local bubble that matters. And it is important for others to remember that a change in magnetic flux can come from the solar system sitting parked in a changing magnetic field (not the right choice), or the solar system moving through space, where the background magnetic field changes strength and direction. You are right, of course, that since the rate of Earth's precession has stayed relatively stable (only increased slightly year after year for the last 100+ years), and Earth's obliquity angle has only changed by a fraction of a degree in that time, that it is almost inconceivable that the solar magnetic field (which flips direction completely in 11 years?), can play much of a role at all in these dynamics.

The key observations/reasoning here:
In the original picture we had of a current filament, the magnetic field was azimuthal everywhere (like the magnetic field around a current carrying wire). Donald Scott comes along with a new picture of a filament's magnetic field, which varies from axial to azimuthal, but still leaves us with a magnetic field which is always tangential to the filament axis. Either way, no radial component of the magnetic field to the filament axis.
Next, along comes evidence of the Local Chimney being a filament, from the "tube" of plasma, to the "pinch" in the walls of the chimney as it crosses the galactic plane, to the ring of stars (Gould's Belt) around the pinch, and most importantly the Pleiades stream of stars traveling right down through the center.
Now, we see our solar system sitting inside the local chimney, with Earth's precessional axis pointed tangentially to the Pleiades. Perfect fit, and one you can verify for yourself.
Charles, if you don't have astronomy software,and don't want to calculate the celestial coordinates yourself for Pleiades vs North precessional pole, ask yourself these questions: 1. The Pleiades lies less than 4 degrees off the ecliptic,so where is the Pleiades compared to the pole of Earth's orbit? Or better yet, 2. If the moon occults (eclipses) the Pleiades from time to time, does that not mean the Earth-moon orbital axis is EXACTLY 90 degrees from the Pleiades at that time?
If the Local Chimney is really a huge scale current filament, with our solar system inside, any solar system axis must align with, or precess around, the helical magnetic field lines of that large scale filament. This is consistent with what we observe.

[peter]

The Dynamo Theory - Has this been tested?

There is an ongoing testing of this theory - the Madison Dynamo Experiment.

At its heart is a one-meter-wide, stainless steel sphere that contains about a ton of sodium metal, which serves as the conducting fluid. Sodium is being used as it has a low Melting Point.

"When the experiment is in operation, two opposing propellers stir the molten sodium in ways that approximate the flow of molten iron inside the Earth.

"At the core of the Earth, it is thought that there are lots of little flows and swirls occurring that contribute to the generation of the planet's magnetic field,"
With the Madison Dynamo Experiment now operational and generating data, the secrets of how natural dynamos perform will begin to emerge and the limits of current theory can begin to be tested."

More recently

On January 4th 2012 a new vessel was delivered and installed.

http://www.youtube.com/watch?v=99wZDeoW ... e=youtu.be

The Madison Plasma Dynamo Experiment (MPDX) is for investigating self-generation of magnetic fields in planets and stars, and related processes in a large, weakly magnetized, fast flowing, and hot (conducting) plasma.

[CharlesChandler]

I don't know much about the Local Chimney, and I'm still mulling over how the various galactic fluxes and angles of attack might interact to define the axial and orbital rotations and precessions in our solar system. As far as I know, the magnetic field outside of the heliosphere is as shown in this image:

http://www.eos.unh.edu/Spheres_1110/gra ... ex2_lg.jpg

The field lines are parallel to the spiral arm that we're in (i.e., the Orion Spur). I don't know why the field lines are shown wrapping around the heliosphere, and I'm wondering whether this is based on measurements, or theoretical expectations, or just the artist's prerogatives. If the interstellar magnetic field affects our solar system at all, those lines of force have to penetrate the heliosphere. So that needs to be researched. But I'm not aware of any evidence of electric currents along such lines, so I "think" that Scott's assertions are pure conjecture.

The Madison Plasma Dynamo Experiment (MPDX) is for investigating self-generation of magnetic fields in planets and stars, and related processes in a large, weakly magnetized, fast flowing, and hot (conducting) plasma.

Have they gotten any results yet?

[viscount aero]

Without sunlight reaching the surface, there shouldn't be much in the way of convection, since there shouldn't be any differential heating, and thus no stirring mechanism. And without convection, there shouldn't be much of a charging mechanism.

I must not understand convection. The Venusian atmosphere varies widely in temperature at distinct layers. The surface is almost 900ºF whereas at 100km height it is -279ºF. Then at 200km the temperature goes back up to 80ºF. Are these temperature differences irrelevant to convection? I would think just the opposite, ie, that it would create extremely violent weather at the boundary layers.

[viscount aero]

Also, Venus' atmosphere conducts electricity probably because it is composed of sulfuric acid (H2SO4) which can dissociate and become H + and HSO4 -. The atmosphere is then an electrolyte.

[peter]

Have they gotten any results yet?

Yes see: http://arxiv.org/abs/1310.8637

But when I read the paper its a bit above my IQ level. But I does seem that they got self generated Magnetic fields from rotating confined Plasmas

They are using Plasmas in their latest experimental work as Previous and ongoing dynamo experiments
use flowing liquid metals.suffer from several limitations which can be avoided by using
plasmas.