Ionospheric convection enhancement with high westward velocities exceeding 1500 m s-1 was observed in association with the particle injection event by SuperDARN in the dusk sector of the auroral zone. Such a convection enhancement could be attributable to the enhanced sunward plasma flows in the dusk sector of the magnetosphere. At the dip equator a ground Pi2 onset was found to occur in association with these convection transients. The onset of the Pi2 lagged behind the convection enhancement by 4--11 min. It is argued that the convection transient could be the earliest indicator of the substorm onset among energetic particle injection, low-latitude Pi2 onset, and, perhaps, the auroral breakup. ¿ 2001 American Geophysical Union