Coronal potential magnetic fields from photospheric sources with finite width

Finite width photospheric sources are used to generate coronal potential magnetic field configurations. The prescription of a suitable distribution of the magnetic flux function within such regions allows to solve the Grad-Shafranov equation and, using the superposition principle, to obtain magnetic field configurations related to arbitrary combinations of photospheric sources and sinks. Following this approach, we have focused our attention on bipolar and quadrupolar magnetic configurations in a background horizontal magnetic field, which creates the conditions for complex magnetic field topologies with magnetic X-points and local dips (minima). These configurations, with infinitely thin and point sources, have been previously invoked (Priest ct al. 1994; 1996) to explain the process of photospheric flux cancellation (cancelling magnetic features) and prominence formation from photospheric material. We have investigated how the different parameters of the model (i.e. source width and magnetic strength) influence the magnetic field topology and have compared our results to previous ones.