Using a three-dimensional global hybrid simulation, we investigate the formation and evolution of ion-scale magnetic reconnection inside an interplanetary rotational discontinuity (RD) owing to its interaction with the quasi-perpendicular (Q-perpendicular to) bow shock and the magnetosphere. The interplanetary magnetic field (IMF) is initially predominantly northward, while it changes to purely southward across the RD. A significantly thinned RD current layer with a width similar to ion skin depth and normal magnetic field B-n approximate to...