Would Earth's magnetic field be strong assuming all the iron from Earth's core were cooled down and then ordered in such a way that the magnetic fields of each individual atom aligns in such a way to create a magnetic field. Would it be stronger than Jupiter's magnetic field or would it even get larger and be the strongest magnetic field?
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$\begingroup$ Related physics.stackexchange.com/q/212787/226902 $\endgroup$– QuilloCommented Apr 4 at 6:31
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$\begingroup$ Please read carefully here the paragraph that describes simply how the field of the earth is generated. It has not much to do with iron .space.com/earths-magnetic-field-explained $\endgroup$– anna vCommented Apr 4 at 6:36
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1$\begingroup$ it seems that crust and mantle and core are mostly iron nickle, but the magnetic field is due to fluid dynamics not to the particular metals. To calculate the field of a solid magnet needs a lot of input numbers to solve.en.wikipedia.org/wiki/Earth%27s_inner_core $\endgroup$– anna vCommented Apr 4 at 7:07
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$\begingroup$ The question is saying if it was made of solid iron which was ferromagnetic would it be stronger than the magnetic field now? $\endgroup$– Roghan ArunCommented Apr 4 at 12:24
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$\begingroup$ What do you mean by "stronger than Jupiter's magnetic field"? Do you mean the magnetic field at a distance from the Earth's centre equal to the radius of Jupiter? Or the magnetic field strength at the surface of the Earth compared to the magnetic field strength at the surface of Jupiter? $\endgroup$– David BaileyCommented Apr 4 at 14:40
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If the Earth's core were a ferromagnet, the magnetic field at the Earth's surface would be a couple of hundred times stronger than the magnetic field on Jupiter's surface, but at a radius corresponding to surface of Jupiter, it would be slightly weaker than Jupiter's surface field.
It is impossible for all the magnetic moments of atoms in the Earth's core to align in single magnetic domain. In the absence of an externally applied field, atoms in a ferromagnetic are aligned by short-range quantum forces, but when a domain gets big enough long-range classical magnetic forces overcome the quantum forces and the domain splits into smaller oppositely aligned domains. The maximum size of a spherical iron domain is about 10 nm. (e.g. See slide 35 of these lectures)
The surface magnetic field you can get from a chunk of magnetized iron is hence limited by its maximum remanence of about a tesla (=10000 gauss). Dipole magnetic fields fall off as $1/r^3$, so if the Earth's core were a 1 tesla ferromagnet with a radius of about 3500 km, the magnetic field at the Earth's surface (with radius about 6400 km) would be about 1600 gauss. At a distance corresponding to Jupiter's radius of about 71000 km, the field would be about 1 gauss, somewhat smaller than Jupiter's actual surface magnetic field of about 4 gauss at its equator and 14 gauss at its North pole.
In practice - if that makes any sense when talking about Earth-core-sized permanent magnets - the field would likely be less. The solidified iron/nickel material of the Earth's core might not have high enough coercivity to hold its maximum remanence.
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$\begingroup$ So the 1600 gauss figure is the value even if all the iron magnetic domains aren't aligned then? $\endgroup$ Commented Apr 4 at 21:11
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$\begingroup$ @MiltonTheMeme Yes, all the magnetic domains do not align in a permanent magnet. The 1600 gauss number is based on the remanence which is the maximum field a permanent magnet can hold. $\endgroup$ Commented Apr 5 at 14:39