Here's a gif from a 1995 supercomputer simulation of the reversal process - https://imgur.com/a/jgpZZBF "The tubes represent magnetic field lines, blue when the field points towards the center and yellow when away."

Original source: https://www.psc.edu/science/glatzmaier.html It took them a year of computing on a CRAY C90 and 2000 hours of processing.