A study of auroral photographs from the satellites of the defense meteorological satellite program (DMSP) over the southern hemisphere for May--July 1974--1975 confirms previous findings and provides the statistical characteristics of the semi-permanent gap in the day sector of the auroral oval. The gap morphology is related to the Bz component of the interplanetary magnetic field (IMF), and the phase of the auroral substorm. When Bz is southward the equatorward movement of the gap is 0.6¿ CGL/unit B2. The gap is relatively wider when Bz is positive than when Bz is negative. Inspite of trends observed to depend on By, the role of the By component on the morphology of the gap could not be established. The observations also confirm that the auroral activity in the night sector depends on the phase of the auroral substorm and the phase of the auroral substorm is related to the variations of the Bz, component of the IMF.