Comment by phkahler

They show the forces tangential to the surface of the proton, going around one way near the "surface" and the other way in the middle. However, the hairy ball theorem says there must be something like "poles" in this case.

https://en.wikipedia.org/wiki/Hairy_ball_theorem

I'm wondering if their proton map covers that, and if the "axis" corresponds to anything familiar.