Magnetic field due to void in rock

[billiards]

This might seem a little strange because presumably a void would not have a magnetic field. However rocks do, so the situation I am considering is a body of rock which has permanent magnetization in one constant direction spread across the whole rock.

Without any voids the magnetic field intensity will be equal everywhere at the surface of the rock. But what happens if you remove some rock and create a void?

Presumably the field intensity will drop off accordingly, you would get an anomaly peaking at the surface at the point connecting the magnetic field lines to the void.

Is my view simplistic, is it possible the void would act as a dipole?

 

[Vailanor]

In which case you could possibly get an increase in intensity in the area outside the void relative to the area inside the void.

 

[astrokreng]

Your view is not simplistic, and your understanding is correct. The presence of a void in a rock does not create a magnetic field, but it can affect the existing magnetic field in the rock. The magnetic field in a rock is due to the alignment of magnetic minerals within the rock, and the presence of a void can disrupt this alignment and cause a decrease in the overall magnetic field intensity.

The void itself would not act as a dipole, as it does not have its own magnetic properties. However, the surrounding rock material may behave as a dipole, with one pole being closer to the void and the other pole being further away. This can create a distortion in the magnetic field intensity, resulting in an anomaly at the surface of the rock.

The exact effect of a void on the magnetic field in a rock will depend on the size and shape of the void, as well as the composition and magnetic properties of the surrounding rock material. Further research and experiments would be needed to fully understand and characterize the impact of voids on magnetic fields in rocks.