Field lines of two bar magnets becoming one bar magnet I have the following conceptual missunderstanding (pressumably). If you have two bar magnets opposing each other separately, then the field lines go from the north- to the southpole of one bar to the other. However, since there are two south- and two-north poles, the field lines seem have opposite direction for the inner two poles. By interpreting these two bar magnets in the elementar magnet picture, combining them leads to a new larger bar magnet with one north- and one southpole. Now the field lines that originally were in opposite direction seem to be going in the same direction as for the outer two poles. Why did they flip? What's happening here?

 A: Every magnet is approximately made up of a zillion tiny dipole magnets. Each tiny dipole magnet has its own dipole magnetic field. The net magnetic field of the entire magnet is simply the linear sum of each tiny dipole magnet's magnetic field.
When you think of it in these terms, you will see that nothing magical or contradictory happens when you put together two magnets, because the same logic would apply to splitting apart one magnet. The picture linked by @Filip in his comment is very important, as it shows the qualitatively correct way of summing the magnetic fields of two dipole magnets.
A: The basic answer to your question is that the field lines that, in the top diagram, ran from left to right between the two neighbouring poles of the two magnets are now (when the magnets have been allowed to come together) INSIDE the magnets.
Remember that a magnet's magnetic field lines don't start on its North pole and end on its South; rather they are continuous closed loops, emerging from the magnet at its North end, running through the air, re-entering the magnet at its South Pole, and running from South to North Pole inside the magnet.
A: This picture shows the lines inside the magnets as well as outside. Perhaps it makes things a little more clear.

Image from https://www.reddit.com/r/explainlikeimfive/comments/97fcxr/eli5_why_does_breaking_a_magnet_in_half_result_in/
