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Author Topic: Could Eddy Currents form the rings of Saturn?  (Read 1985 times)

Offline HannuMultanen

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Could Eddy Currents form the rings of Saturn?
« on: 10/10/2015 09:43:08 »
I have this "theory" and I would like to know if it's already known phenomenom... or just a bad idea:

I've read that the magnetic field of Saturn is very stable. I've also read that the rings consist mostly ice particles. I assume these particles are not perfect insulators but conduct electricity (water ice + inpurities = some conductivity?).
My idea is that eddy currents would be created within the ring particles. The energy wasted by the eddy currents would create drag and so over time only possible orbit would be on the "neutral" zone of the magnetic field: This would be round orbit (not oval), on the halfway between Saturns magnetic poles... This is where the rings appear to be located.

I understand there's other explanations for rings of Saturn but what I would like to know is if eddy currents could be contributing factor on the formation and/or shape of the rings?

In future, please phrase the title as a question - Mod.
« Last Edit: 10/10/2015 22:07:59 by evan_au »


 

Online evan_au

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Re: Eddy currents within the ring particles of Saturn?
« Reply #1 on: 10/10/2015 22:06:15 »
The Magnetic field of Saturn does play a part in the transport of ionized water vapor from Saturn's icy moon Enceledus.

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the "neutral" zone of the magnetic field
There is not really a "neutral" zone within a magnetic field. Any conductive object passing through the magnetic field will experience eddy currents.

The only time there would be no eddy currents within a magnetic field would be if the conductive object were rotating at exactly the same speed as the magnetic field.

Objects closer to the planet and orbiting faster than the magnetic field would tend to be slowed down, which would drop them out of orbit, into Saturn's atmosphere.

Objects farther from the planet and orbiting slower than the magnetic field would tend to be sped up, which would boost them into even higher orbits, and be lost into the solar wind through the "magnetotail". This is known to occur for ionized water vapor.

Non-conductive objects (like ice where the ions of any salts are locked in place due to their extremely low temperature) would not be affected by the magnetic field at all.

Quote
This is where the rings appear to be located.
The equatorial belt is also where Saturn's inner moons are located, and it is known that these moons contribute to the content of the rings.

Some have hypothesised that the rings were formed from the debris of an icy moon which was torn apart by Saturn's gravity, or rubble left over from Saturn's formation in the protoplanetary disk. In either case, the structure of the protoplanetray disk would tend to concentrate the moons in the orbital plane of the Solar System, and in the equatorial plane of Saturn's rotation.
 

Offline chris

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Re: Could Eddy Currents form the rings of Saturn?
« Reply #2 on: 10/10/2015 22:10:01 »
Nice work Evan!
 

Offline HannuMultanen

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Re: Eddy currents within the ring particles of Saturn?
« Reply #3 on: 11/10/2015 11:52:50 »
There is not really a "neutral" zone within a magnetic field. Any conductive object passing through the magnetic field will experience eddy currents.
I have to disagree on this Evan. I think that to create eddy currents there has to be a change in the magnetic field. If either orientation or force of the field doesn't change current is not created. If you are inside particle on the exact round orbit between the poles, you could observe steady magnetic field. So no eddy currents created... Right?
 

Offline Colin2B

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Re: Eddy currents within the ring particles of Saturn?
« Reply #4 on: 11/10/2015 12:03:15 »
If you are inside particle on the exact round orbit between the poles, you could observe steady magnetic field. So no eddy currents created... Right?
It really depends on the orientation. If you look at the earth the spin axis and magnetic axis are different, so changing field.
Not sure about Saturn.


Thanks for an interesting thread, your idea of eddy currents set folks thinking.

Edit PS just had a look on wiki, apparently the magnetic field is aligned with rotational axis
« Last Edit: 11/10/2015 12:07:49 by Colin2B »
 

Offline HannuMultanen

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Re: Could Eddy Currents form the rings of Saturn?
« Reply #5 on: 13/10/2015 14:40:58 »
So, until somebody points out an obvious fault in my "theory", I will continue speculation:

There might be a way to to determine if eddy currents have effect to rings of Saturn - or had millions of years ago: Unlike many forces (like gravity etc.), ones created by eddy currents are not necessary directly proportional to the mass of the particle. This could have created patterns to the structure of the rings.

For example the electrical conductivity of one individual ring particle: Some ice particles might be better conductors than others (internal structure, different inpurities etc.). Temperature might have effect on to this also.

Other example: Size of the particle. Within lone, very small particles (like from one single water molecule on to perhaps a bit bigger) eddy currents are not created at all. So there's no drag effect.
(Possibly plasma clouds etc. might be exception on this cathegory).

I think there would then be particles which are "optimal" size. These might perhaps be something like 5mm or 100mm in diameter. On these particles maximum eddy current induced drag force would be created (compared to their mass).
I have a strong feeling that on a large ice blob (let's say size of a car), drag forces would again be relatively smaller. Maybe someone could verify this?

There's this one other thing I can't seem to figure out: When particle is orbiting outside "neutral zone" of the magnetic field, is the eddy current force just slowing the particle down? Or can it actually "steer" it sideways?  I think it might be the latter but can't really fully understand the forces involved.
 

Offline Colin2B

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Re: Could Eddy Currents form the rings of Saturn?
« Reply #6 on: 13/10/2015 14:58:44 »
So, until somebody points out an obvious fault in my "theory", I will continue speculation:
You would need to check a few more facts.
For example, the magnetic field on earth is not homogeneous, it varies depending on mineral deposits below the surface.

Edit. Just been for a run and question came to mind while out:
Are you arguing there are eddy currents in which case Evan seems a correct view, or are you arguing no eddy currents hence no drag effect?
« Last Edit: 13/10/2015 17:58:44 by Colin2B »
 

Offline HannuMultanen

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Re: Could Eddy Currents form the rings of Saturn?
« Reply #7 on: 15/10/2015 10:31:02 »
Edit. Just been for a run and question came to mind while out:
Are you arguing there are eddy currents in which case Evan seems a correct view, or are you arguing no eddy currents hence no drag effect?

I'm saying there are no eddy currents induced on the exact round orbit, on exactly half way between the magnetic poles. This is because ice particle wouldn't see change in magnetic field. Both orientation and magnitude of the field particle sees stays the same during any given round.
(Eddy currents are only created when there's a change in magnetic flux inside particle. Wikipedia says "...the induced electromotive force in any closed circuit is equal to the rate of change of the magnetic flux enclosed by the circuit").

So, the maximal change in magnetic flux inside ice particle would be if it would orbit over the magnetic poles. This would create the most drag. On the equator, on round orbit, the drag would be smallest. Actually non-existent if magnetic field would be 100% perfect.
 

Offline HannuMultanen

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Re: Could Eddy Currents form the rings of Saturn?
« Reply #8 on: 15/10/2015 18:17:40 »
My english might be far from perfect so I made this picture below to point out some things.

First point: Even if we rotate this magnet around it's vertical axis, it doesn't actually change the magnetic field (I wonder if people agree with this...). So magnetic field of Saturnus isn't "rotating". It would "wobble" if the rotational axis would be different than magnetic. But uniquelly in Saturns case these are on same axis.

So then if we travel with the electrically conducting particle on green orbit, the magnitude of the magnetic flux inside this particle stays the same. So no eddy currents created.
If we then travel with the particle on the blue orbit, we could see constant change on macnetic flux. Eddy currents would be created. Interestingly, current would now be created also at point B, since particle is exiting a stronger magnetic field in to a weaker (and moment later back to stronger field towards opposite pole).

 

Offline HannuMultanen

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Re: Eddy currents within the ring particles of Saturn?
« Reply #9 on: 19/10/2015 20:02:52 »
I made a webpage about my idea but can't post a link (forum rules...). Meaning I'm still looking for the fatal error in my idea. Any help is welcome.

This point Evan made is certainly valid and worth further discussion:
Non-conductive objects (like ice where the ions of any salts are locked in place due to their extremely low temperature) would not be affected by the magnetic field at all.
Wikipedia says that ring particles are 99.9% water ice. This doesn't sound like a great conductor. But quite many sources mention 93% ice with 7% of "amorphous carbon". That could well be conductive combination. I wonder what is the last/best knowledge on this?
 

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Re: Eddy currents within the ring particles of Saturn?
« Reply #9 on: 19/10/2015 20:02:52 »

 

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