Magnetic fields of two large bodies interacting.

Omits

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If an object with a magnetic field as 'strong' as Earth's say were to position itself near Earth would this create problems with whatever (e.g. lower radiation protection, weather, comms., orbit.)?
 

CupofJoe

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I know auroras are pretty and that's about it.
 

Dave

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It will confuse some migrating birds and homing pigeons that use the magnetic field to navigate, but other than that probably not.

The Earth's magnetic pole positions are moving all the time, and on a geological timescale, they frequently flip over and reverse, but whether that causes any problems no one can be completely sure as we haven't seen it happen before while we've been around to record it. We know it happens, because when molten lava sets, any magnetic crystals aligned themselves to the Earth's current field at that time, and that direction can then be observed in ancient rocks.

Another large magnetic body coming close would certainly cause the Earth's magnetic field to change, but we know much less than we think we do about these things. We don't really know how much the Sun's magnetic field influences Earth, or Jupiter's strong field when it comes closer. They certainly cause radio interference. The Earth's Core isn't homogenous either, but has a large solid floating around in it. There was an article in New Scientist about that a few weeks ago.

This NASA article says that magnetic changes are nothing to be alarmed about or will have any effects on the Climate: Ask NASA Climate
 

Christine Wheelwright

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Interesting question. The Earth's magnetic field is thought of as an effect, not a cause. In terms of flux density it is relatively weak (25 to 65 micro teslas). A fridge magnet produces about 200 times this. I don't think we understand biological effects well though (eg migrating birds).
 

Yozh

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Could you have an object with a strong enough magnetic pull to affect life on earth , but not a great enough mass to cause epic *gravitational* interference? I'm asking honestly, I don't know.
 

Dave

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Could you have an object with a strong enough magnetic pull to affect life on earth , but not a great enough mass to cause epic *gravitational* interference? I'm asking honestly, I don't know.
I think it's unlikely but not impossible. As @Christine Wheelwright said, a fridge magnet produces about 200 times the flux density of the Earth, and about 6% of meteorites are iron-nickel alloy achondrites or siderites, which could potentially be both small enough and magnetic enough. I guess there is a science fiction story there somewhere. Larry Niven had his Belters out looking for monopole asteroids, something that I can't really conceive how they could work, but a magnetised very long, or a horseshoe-shaped, iron-nickel asteroid is quite a conceivable thing.

The large solid mass that I mentioned inside the Earth's core is supposedly an object that collided with the Earth during it's formation. Of course, in the early days of the formation of the solar system there were both more, and larger objects around, objects large enough to knock planets on their sides or make them rotate in the opposite direction. Over time, these have either struck planets, or struck each other, so that it is a much quieter place today.
 

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Could approaching like poles cause the earths liquid iron core to 'flip' over time?
 

Dave

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Could approaching like poles cause the earths liquid iron core to 'flip' over time?
I was interested in this about 40 years ago and why the flipping over happened. I don't believe that we've learnt very much more since. I do know that the magnetic poles are quite a long way off the axis of rotation at the moment, and are still moving further away. Whether that will continue or not, I don't think anyone knows. With all these things, the time that we've been taking measurements is infinitesimally small compared to the age of the Earth itself.
 

Venusian Broon

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Could you have an object with a strong enough magnetic pull to affect life on earth , but not a great enough mass to cause epic *gravitational* interference? I'm asking honestly, I don't know.
As others have pointed out, many basic magnets, never mind the ones used for particle accelerators etc,, humanity have made have magnetic fields stronger than the Earths. And even the strongest don't have global impact.

Off the top of my head, to impact the magnetic field of the Earth globally, I suspect you'd have to construct a device with at least the scale of the Earth itself. Possibly one could construct (theoretically) a far more efficient system, in terms of mass, than the natural one the Earth has....for example people have suggested ionising Phobos' surface to create a plasma torus around Mars that could give it magnetic field. So I guess nab an asteroid and make it orbit the Earth, ionising it? A little bit out of our abilities at the moment!

A passing Neutron star, which has magnetic fields trillions of times higher than the Earth's were to pass close by it could have a major impact on the magnetic field, but the impact would be hard to quantify. A neutron star is very small in scale - about 20km in diameter - so more like a point source next to the Earth. So although much stronger, I don't think it will have a 'smooth' global impact! However, a passing neutron star, close enough to majorly impact the Earth, is going to cause far more problems with its gravity.

In my eyes there are two main benefits of the Earth's magnetic field that are vital: In the short term they stop most of the solar wind and cosmic rays depleting and then overpowering the ozone layer. When this is gone, then the flux of hard radiation hitting the Earth would be, if for a quite small amount of time, catastrophic. Radiation could eventually kill everything living on the surface. A close enough supernova could do the same thing and wipe out the ozone layer in a similar manner.

Secondly, if the magnetic field were switched off, so to speak, for a very long time (and also somehow the fact that radiation didn't kill everything) then the solar wind would start to evaporate the parts of the Earth's atmosphere. Now in general Earth would hold onto quite a bit of its atmosphere as its gravity is strong enough to hold on, but lighter elements would be pulled away. Unfortunately molecules like water, when dissociated are a bit at risk. So give it long enough, we could lose a significant amount of water...maybe...but we're taking about geological timescales here that the magnetic field needs to be switched off, for this to happen. So it's not something to worry about for a very short, year or two magnetic field transition/disappearance!
 

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