  We consider N=2 four dimensional field theories compactified on a two torus
in the presence of a U(1) magnetic field. We discuss the restrictions leading
to theories with (2,2) supersymmetry or (0,2) supersymmetry in two dimensions.
The field theories live on D5 branes wrapped on four cycles of Calabi-Yau
3-folds or 4-folds described as resolved ADE singularities or resolved conifold
fibered over a two torus.
