A fully three-dimensional magnetic reconnection model is proposed for the merging between a spatially nonuniform interplanetary magnetic field and the geomagnetic field. The model generalizes the canonical model of Cowley (1973) and Stern (1973), replacing the two magnetic nulls of the canonical model by a web of A and B nulls and their associated null lines. It is shown that the new A-B model helps resolve some of the difficulties of the canonical model and allows a qualitatively consistent description of magnetic reconnection that begins on the dayside and subsequently evolves to the nightside. A kinematic study based on the induction equation demonstrates that in an ideal plasma, the velocity of the magnetic field has power-law singularities at the separatrices which are the sites of reconnection. Qualitative implications of this global model for ionospheric potential patterns and substorm signatures are discussed. ¿ American Geophysical Union 1996