Observations of non-conjugate theta aurora N. Ostgaard, S.B. Mende, H.U. Frey, L.A. Frank, and J.B. Sigwarth Based on simultaneous imaging data from IMAGE FUV and Polar VIS Earth camera and DMSP particle measurements we report two events where a theta aurora was observed in one hemisphere but not in the other. IMF control and hemispherical conductivity differences are suggested as possible explanations for the occurrence of non-conjugate theta aurora. _______________ Geophysical Research Letters, 30, 2125, doi:10.1029/2003GL017914, 2003