Numerical simulation of the 3-D topology of magnetic field lines above a Bipolar Magnetic Region (BMR) is demonstrated. In
contrast to the usually accepted description of photospheric magnetic fields by the continuous function, the new approach is tested. The BMR is represented as a specifically distributed set of discrete sources of magnetic flux. Three branches of the specific structures of potential field lines was found in different parts of the BMR. The field line structures correspond to chromospheric fibrils, prominence configurations and to coronal arches. We suppose that the field lines create the principal skeleton of the prominence phenomenon. A prominence plasma is considered inside the magnetic flux tubes. The prominence legs represent the part of the field lines rooted in the convective zone in regions with magnetic flux concentration.