Megnatic Field Of Earth

[FizixFreak]

does earth has a megnatic field and if so how????????

[Pythagorean]

Yes. I don't think it's known for sure how, but a good guess is the motion of liquid-state metals in Earth's core, like iron.

[Naty1]

And there have been declines for unknown reasons in recent times...as well as shifts of north and south poles over the millenia...just wait until the man made global warming kooks find out that the magnetic field is about to undergo another upheaveal!!!

another strange effect is that the north and south poles drift over time...deviation and variation are the two most importasnt variants in navigation

http://en.wikipedia.org/wiki/Magnetic_variation#Variation

[FizixFreak]

yes. I don't think it's known for sure how, but a good guess is the motion of liquid-state metals in earth's core, like iron.

but the megnatic field is caused by moving charges only how can movement of liquid state metal cause megnatic field?????????

[Pythagorean]

but the megnatic field is caused by moving charges only how can movement of liquid state metal cause megnatic field?????????

There are moving charges in it ;)

[FizixFreak]

There are moving charges in it ;)

all type of matter contains moving charges but on the whole every substance is neutral why is not magnetic field caused by other substances :confused:
i m definatly missing something here:blushing:

[mgb_phys]

i m definatly missing something here:blushing:
Don't worry you're not as embarrassed as physics.
The Earth's magnetic field is amazingly poorly understood even today, which is why we get away with handwaving explanations of the 'dynamo effect'.

There are possible explanations from second order effects of a moving conductive (but overall uncharged) fluid moving in a field - a little like how the corriolis effect is a second-order effect of a rotating earth.

[dacruick]

If the earth is spinning doesn't that mean that the iron or whatever it is in the earth's core must be spinning. and when you spin isn't there acceleration? is it possible that in the earths core there is created some sort of strong electric field?

[FizixFreak]

electric field due to spin WOW that is some question
my guess is that the earth spin with a CONSTANT anguler velocity (no accelaration ) if the earth were accelarating our days would be shortened with time!!
but thats my personasl opinion could be wrong

[FizixFreak]

Don't worry you're not as embarrassed as physics.
The Earth's magnetic field is amazingly poorly understood even today, which is why we get away with handwaving explanations of the 'dynamo effect'.

There are possible explanations from second order effects of a moving conductive (but overall uncharged) fluid moving in a field - a little like how the corriolis effect is a second-order effect of a rotating earth.

what are the efffects which are seen because of the megnatic field of earth ?????????

[mgb_phys]

what are the efffects which are seen because of the megnatic field of earth ?????????

Important ones are:
Compass needles point north.
The effect of shielding us from solar radiation from the sun.

[dacruick]

electric field due to spin WOW that is some question
my guess is that the earth spin with a CONSTANT anguler velocity (no accelaration ) if the earth were accelarating our days would be shortened with time!!
but thats my personasl opinion could be wrong

even with CONSTANT angular velocity don't you get acceleration. towards the centre maybe? and then an electric field would be created magically causing a magnetic field to form perpendicular to a vector towards the centre of the earth, thereby pointing maybe to a north and south pole? . :smile: just speculating.

[dacruick]

maybe there are different materials inside the centre of the earth. and if the earth is spinning those materials are forced to the outside of the inner core. and then since those materials have different densities there could also be a distinct line that divides those two materials. even a third material between two materials. and if that third material has enough energy from heat could it accelerate electrons across a potential or something insane like that.

[FizixFreak]

even with CONSTANT angular velocity don't you get acceleration. towards the centre maybe? and then an electric field would be created magically causing a magnetic field to form perpendicular to a vector towards the centre of the earth, thereby pointing maybe to a north and south pole? . :smile: just speculating.

actually when we talk about uniform circuler motion the average accelaration is zero we get only the instantaneous values of the accelaration !!!!(i guess)
apart from that i m not completely familiar with the concept of electric field due to spin can you please enlighten me on that

[dacruick]

Well average acceleration is 0, but so is the average electric field. At any given moment there would be a changing electric field, which induces a magnetic field perpendicularly to that. I doubt I would provide you a fulfilling explanation. They do spin magnets in many devices though, try googling that.

[rewebster]

I think someone a long time ago buried a very large copper coil and batteries :biggrin:

[FizixFreak]

Well average acceleration is 0, but so is the average electric field. At any given moment there would be a changing electric field, which induces a magnetic field perpendicularly to that. I doubt I would provide you a fulfilling explanation. They do spin magnets in many devices though, try googling that.

so the in that case megnatic field will also be zero (overall) but we will get some instantaneuos values right
is that what you are trying too say ?
but in that case the megnatic field it self would not be non uniform and an non uniform megnatic field will show non uniform effects which is not the case (if i m not wrong)

[dacruick]

so the in that case megnatic field will also be zero (overall) but we will get some instantaneuos values right
is that what you are trying too say ?
but in that case the megnatic field it self would not be non uniform and an non uniform megnatic field will show non uniform effects which is not the case (if i m not wrong)

the magnetic field isn't uniform to my knowledge. is it?

[dacruick]

try checking out this link i found right at the bottom of the page.

http://www.physicsforums.com/showthread.php?t=272847

[FizixFreak]

when north goes south ??????????

[FizixFreak]

the magnetic field isn't uniform to my knowledge. is it?

i m not sure about it either but if it is not uniform it,s "non uniform effects" will be quite prominent dont you think?
but it is my openion only could be wrong

[dacruick]

hmm. well lets say that we have molten metal in the centre of the earth constantly rotating. the net magnetic flux would be the same wouldnt it? yeah i dont know fiz, i dont know.

[Leonardo de N]

Important ones are:
Compass needles point north.


Doesn't it seem odd that we define the magnetic field of Earth (a bar magnet) by using another bar magnet (a compass)? Isn't the use of a compass a formal self referring definition? Goedel proved that self referring systems will have places that are either incomplete or inconsistent. (a paraphrase) If this is true, what than is the incompleteness and/or inconsistency that one might expect in the magnetic fields around earth; or say in the simplier case of another bar magnet?

[jreelawg]

Some researchers are wondering if Earth's oceans have something to do with it.

"His research suggests that Earth’s magnetism is actually linked to ocean movements. The salt in seawater allows it to conduct electricity, meaning it generates electrical and magnetic fields as it moves."

http://www.timesonline.co.uk/tol/news/science/article6493481.ece

What do you guys think?

[dacruick]

salt water doesn't conduct electricity that well. But there are two people who say it could be valid who are much smarter than I. ill leave it at im quite skeptical.

[jreelawg]

A book I read from the seventies questions the dynamo effect as the cause of magnetic fields, because Venus's magnetic field is much weaker than expected. Has this issue been solved?

[jasonRF]

so the in that case megnatic field will also be zero (overall) but we will get some instantaneuos values right
is that what you are trying too say ?
but in that case the megnatic field it self would not be non uniform and an non uniform megnatic field will show non uniform effects which is not the case (if i m not wrong)

The magnetic field of the Earth is approximately a dipole, which is the magnetic field of a loop of current. So no, it is not uniform. And yes, it shows non-uniform effects. Consider two compasses, one in London and one in Tokyo. Do their needles point in the same direction? No! They both point towards the magnetic north pole, which is a different direction from London than it is from Tokyo.

[jasonRF]

A book I read from the seventies questions the dynamo effect as the cause of magnetic fields

This is still the dominant theory. The basic theory comes from magnetohydrodynamics (MHD), which sounds more impressive than it is. There is a reasonable number of geophysicists working this problem. search "Earth geomagnetic field MHD dynamo" in google scholar and you will find a ton of articles on this. Numerical models have been built that show the periodic field reversals in the Earth, etc.

[FizixFreak]

The magnetic field of the Earth is approximately a dipole, which is the magnetic field of a loop of current. So no, it is not uniform. And yes, it shows non-uniform effects. Consider two compasses, one in London and one in Tokyo. Do their needles point in the same direction? No! They both point towards the magnetic north pole, which is a different direction from London than it is from Tokyo.

WOW! why did not i thougth of that

[venkat130583]

there are several reasons for the earth,s magnetic field. but none can give the exact explanation. they are,
1. during the rotation of sun spin itself, the charged particles in the atmosphere also revolve with it. according to the christian oersted that revolution causes the magnetic field .
2. inside the earth there 3500km radially the molten magnetic materials are exhibiting the magnetic lines of forces.

[cragar]

water is fairly paramagnetic

[dacruick]

shouldn't magnetic fields be stronger closer to water then?

[cragar]

ya , you can push a grape with a bar magnet hanging from a torsion setup.
Isn't the earths B field pretty weak . I'm not necessarily saying our oceans are the major contributor to our field , but i just want to discuss it .

[FizixFreak]

has the strength of this megnatic field benn calculated?

[cragar]

yes , about 30 micro teslas at the surface . about 60 microteslas at the poles

[FizixFreak]

i doubt that such weak megnatic field will be prominent (but obviosly it is)
but since it is not uniform are we talking about average value ?
?

[dacruick]

Something tells me that it is not the water in the ocean. Wouldn't there be extremely stronger fields over water than there would be over land? wouldn't someone have noticed that by now.

It makes more sense to me that it is something in the earths core because that allows for the field to be distributed across the entire earth more plausibly.

[sophiecentaur]

I'd go for the argument which uses the Earth's metallic core to explain the majority of the B field. After all, there is such a small mass of surface water compared with the vast volume available in the region of the core.

[FizixFreak]

yeah the oceans do not seem to present an satisfying explanation

[dacruick]

its a nice idea though. I would like them to be right. I wonder what kind of energy you could create by cycling salt saturated water in a whirlpool and running current through it. I speculate it would be an overall loss in energy, but who knows.