Hello, I'm trying to find an equation which describes B(z) inside of a permanent ring magnet that is axially magnetized. Also, depending on if the equation holds true, if the ring magnet will behave as a magnetic mirror. Below is an equation which describes the axial field of such a magnet, however I believe the equation is only valid when considering a distance starting from the ending face of the magnet. When I use this equation for a magnet with the parameters shown below, here is the field which is visualized. Parameters: Br 12000 Thickness 0.1 [m] R(out) 0.18 [m] R(in) 0.1 [m] Its important to note that I shifted the graph below by .05 [m] to center the ring magnet at the origin. I'm surprised to discover that the field inside the magnet actually flips directions. I thought perhaps the equation shown above which describes this field, was inaccurate inside the magnet. But then I found this picture. Which appears to show exactly that. I have yet to find any graphs produced by finite element analysis software which would give me more confidence in the equation for B(z) shown above. My questions are, does anyone have experience solving the magnetic field for a ring magnet, and can confirm that indeed the equation listed above works for all space? And considering plasmas or charged particles, when approaching the inside of the magnet where the field grows, would this serve as a magnetic mirror in some sense? If the charged particles are not reflected from the increasing magnetic field before reaching the inside of the magnet, will they be accelerated by the abrupt change in magnetic field? Or will they be reflected as the charged particle continues towards the center of the magnet. Perhaps even trapped between the regions where the field direction abruptly changed?