The prevalent theory describing the entry of solar wind energy into the magnetosphere involves the merging of solar wind and terrestrial magnetic field lines on the dayside magnetopause and the subsequent reconnection of those field lines across the neutral sheet in the Earth's magnetotail. The reconnection is thought to occur at a neutral line, whose location is often set at ~100 Re behind the Earth. The location of this neutral line has not been verified experimentally to date, and in this paper we shall provide some constraints suggesting its average location to lie in the range -50>X>-80 Re. We shall use AMPTE, ISEE, and IMP 8 magnetic field data to evaluate the falloff of Bz at the position of the neutral sheet as one moves back into the tail. From these measurements we construct an analytical representation of Bz as a function of downtail position. Using the Coroniti and Kennel relationship for the flaring of the magnetotail, we evaluate the average position of the equatorward edge of the polar cap, which we then assume to represent the poleward edge of the average auroral oval. From flux conservation considerations, we then evaluate the average width of the auroral oval. We conclude the paper by discussing how the mapping from the magnetotail is reflected in the scale sizes of auroral features in the midnight sector of the auroral oval. ¿ American Geophysical Union 1993