Cluster / FAST investigation of two early morning aurora events Costel Bunescu, Octav Marghitu Institute for Space Sciences, Bucharest We investigate two Cluster / FAST conjugate events, in January 2003 and January 2005, with Cluster crossing the auroral field lines in pearl-on-string configuration at about 3.5 RE altitude, and FAST probing the topside ionosphere at about 0.4RE altitude. Both events occur in the early morning sector, around 2--4 MLT, during the early / late substorm recovery phase in 2003 / 2005. Cluster data show interesting similarities between the two cases in the magnetic field, electric field, and particle signatures. By comparing different types of data we identify for each event both intervals when the various signatures are in good agreement with each other and intervals with rather poor agreement. This may be the result of space and time variablity, whose analysis is made possible by Cluster. At low altitude, FAST crosses field-aligned current (FAC) structures whose intensity and latitudinal extent appear to be consistent with the mapped characteristics of the FACs observed by Cluster, provided that the FAC motion at Cluster level is properly taken into account. For the event in 2003 Polar optical data are available as well, indicating a structured and time varying luminosity pattern, consistent with the measurements of Cluster and FAST. Although we could not find optical data for the event in 2005, the similarities in the Cluster data suggest as well a complex luminosity pattern. However, the FAST data, in particular the magnetic field, show a less disturbed profile, that we tentatively associate with an increased length scale of the aurora during the late recovery substorm phase.