I believe, Earth could be approximated by a molten, metallic, non-magnetic sphere, with a molten stony sphere around it. However,

  • As far I know, the magnetic properties of the lava in the crust, in its temperature and pressure, is not very well known.
  • The case is the same, for a greater extent, to the core. As far I know, the core is mostly a mix of different elements, with a large part of iron, so the amount and ratio of the non-ironic part might affect significantly the permeability.

I believe, getting the answer to this question could be better answered experimentally. However, in its naive form (getting a current around the equator) it seems unfeasible.

Corresponding this, I found nothing by google. Maybe lesser direct measurements are possible (like the interaction of the Earth's magnetic field to some external one?)

Is it known? How was it calculated?

  • $\begingroup$ Have you figured out the answer to this question? I was interested in this too because I wanted to know how hard it would be to create a magnetically supported orbital loop around earth/mars with a strong current flowing inside. This question was the first one to come up on my google search on "earth's core permeability". There doesn't seem to be many helpful materials out there, and all measurements of permeability that I've seen so far are done for commercially available alloys under standard pressure and below the curie points. $\endgroup$
    – martian17
    Commented Aug 3, 2022 at 10:46
  • $\begingroup$ Relative magnetic permeability (SI magnetic susceptibility + 1) of most rocks seem range from just above 1 to a few thousand. source1: researchgate.net/figure/… source2: iopscience.iop.org/article/10.1088/1742-6596/1176/4/042068/pdf $\endgroup$
    – martian17
    Commented Aug 3, 2022 at 11:53
  • $\begingroup$ I found a data on iron's "reduced inverse susceptibility" (λS(S+1)/3(k subscript B)Tc) against the temperature (T/Tc) above the curie temperature in this paper iopscience.iop.org/article/10.1088/0305-4608/13/1/018 The diagram was originally cited from another paper that I don't have access to journals.jps.jp/doi/10.1143/JPSJ.11.855 At T/Tc = 1.0, the value (from later on V) is close to zero, at T/Tc = 1.2 V ≈ 0.1, at T/Tc = 1.4 V ≈ 0.25, at T/Tc = 1.6 V ≈ 0.4, at T/Tc = 1.8 V ≈ 0.6, At T/Tc = 2.0 V ≈ 0.8, and at T/Tc = 2.2 V ≈ 1.0. $\endgroup$
    – martian17
    Commented Aug 3, 2022 at 12:32
  • 1
    $\begingroup$ The earth's outer core is around 5000K, and the inner core is around 5700K. Disregarding the pressure, this is around 5 times the curie temperature. Extrapolating the data above gives the reduced inverse susceptibility of around 4. This gives the susceptibility value of 0.25, and converting to the permeability gives 1.25 (very low I know!). Note that this observation was likely done under 1 bar of pressure (no detail provided), so the actual permeability of the earth's core may be drastically different. $\endgroup$
    – martian17
    Commented Aug 3, 2022 at 12:40


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