If it's possible to guide magnetic field lines using a shaped magnetic material(cone) and the increase in magnetic field strength is proportional to the ratio of the areas of the two ends of the cone,will a cone of magnetic material held in the air or placed on the ground increase the density or strength of earth's magnetic field? In otherwords if I had a cone of 45 degrees with a 1 inch hole on top and 10 inches at the bottom and earth' average magnetic strength is approximately .45 gauss,at the top of the cone it should measure 4.5 gauss?

  • $\begingroup$ Yes, this arrangement is sometimes being used in very sensitive fluxgate magnetometers. I think I saw this arrangement in a NASA planetary magnetometer once. I will try to dig up an image for you. I think you are off by a factor of ten, by the way... $(10:1)^2=100$. $\endgroup$ – CuriousOne Apr 20 '16 at 23:11

I couldn't find a good picture of a configuration that can be used to "concentrate" magnetic field lines, so I made a quick simulation with FEEM and this is what it looks like:

enter image description here

What you are looking at are two V-shaped magnet jokes from soft iron inside a coil that creates a weak, mostly constant field to simulate the geomagnetic field. Please ignore the field outside the coil, it's mostly an artifact of not treating the vacuum correctly (the surrounding area is too small and I have not made sure that the boundary conditions are correct). Also, this is a planar simulation, i.e. this is a cross section of a long flat structure. Planar simulations look nicer than axis-symmetric ones in FEMM, so I picked this one, even though it does underestimate the "concentration", since it only works in one dimension and not in two, as it would with a pair of axial-symmetric yokes.

  • $\begingroup$ I think it's yokes, not jokes $\endgroup$ – Voltage Spike Jun 7 '19 at 16:44

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