Unified Bertotti-Robinson and Melvin Spacetimes
  We present a solution for the Einstein-Maxwell (EM) equations which unifies both the magnetic Bertotti-Robinson (BR) and Melvin (ML) solutions as a single metric in the axially symmetric coordinates ${t,\rho,z,\varphi} $. Depending on the strength of magnetic field the spacetime manifold, unlike the cases of separate BR and ML spacetime, develops singularity on the symmetry axis ($\rho =0$). Our analysis shows, beside other things that there are regions inaccessible to all null geodesics. 
M. Halilsoy and S. Habib Mazharimousavi
gr-qc