We have studied dayside magnetic reconnection by using a three-dimensional global magnetohydrodynamic simulation of the interaction between the solar wind and the magnetosphere. We found two different mechanisms for the formation of magnetic flux tubes at the dayside magnetopause which depend on the orientation of the interplanetary magnetic field (IMF). The dayside magnetic flux tubes occur only when the IMF has a southward component. A strongly twisted and localized magnetic flux tube similar to magnetic flux ropes appears at the subsolar magnetopause when the IMF has a large By component. When the By component is small, twin flux tubes appear at the dayside magnetopause. Both types of magnetic flux tube are consistent with several observational features of flux transfer events and are generated by antiparallel magnetic reconnection. ¿ American Geophysical Union 1989