Kerr black hole shadows in Melvin magnetic field with stable photon orbits

We have studied the spacetime of a Kerr black hole immersed in Melvin magnetic field, and found Melvin-Kerr shadow becomes more elongated as field parameter $B$ increases. not only that an unstable light ring could exist but also stable exist. The radius increases with increase $B$, it is opposite for ring. For certain rotation $a$, both prograde retrograde (stable) rings when less than critical value ${B}_{c}$ In this case, shadows two regions corresponding to photon orbits on sides middle main shadow. As continues increase, there region emerges life absence makes half-panoramic (equatorial) When bigger ring, neither nor exists. panoramic addition, some self-similar fractal structures arising from chaotic motion photon.