Coronal potential magnetic fields from photospheric sources with finite width

Finite width photospheric sources are used to generate coronal potential ma gnetic field configurations. The prescription of a suitable distribution of the magnetic flux function within such regions allows to solve the Grad-Sh afranov equation and, using the superposition principle, to obtain magnetic field configurations related to arbitrary combinations of photospheric sou rces and sinks. Following this approach, we have focused our attention on b ipolar and quadrupolar magnetic configurations in a background horizontal m agnetic field, which creates the conditions for complex magnetic field topo logies with magnetic X-points and local dips (minima). These configurations , with infinitely thin and point sources, have been previously invoked (Pri est ct al. 1994; 1996) to explain the process of photospheric flux cancella tion (cancelling magnetic features) and prominence formation from photosphe ric material. We have investigated how the different parameters of the mode l (i.e. source width and magnetic strength) influence the magnetic field to pology and have compared our results to previous ones.