The expanding/contracting polar cap model has been used to simulate DE 2 ion drift data during substorms as determined using the AL index. Of the 39 cases modeled, 57% required the opening of a nightside gap which maps to where reconnection occurs in the tail; 75% of the 16 recovery phase cases required a nighside gap while only 29% of the 17 expansion phase cases required a nightside gap. On the basis of this result, we conclude the following. If a nightside gap implies tail reconnection, then connection probably occurs after expansion phase onset and continues throughout most of the recovery phase of a substorm. ¿ American Geophysical Union 1989