We describe the response of the high-latitude convection to a sudden southward turning of the IMF. In this event Bz recorded at the WIND satellite switched from +6 nT to -6 nT in 2 1/2 minutes and effects in the ionosphere were observed by the SuperDARN HF radars. In the vicinity of noon MLT, the convection switched suddenly (~2 min) from sunward to antisunward with the velocity change reaching magnitudes as great as 1500 m/s in about 6 minutes. Surprisingly, the responses at the other MLTs distributed from noon to midnight began at virtually the same time. Meridional flows near 22 MLT were observed to reverse direction in about 4 minutes with the velocity change reaching magnitudes as great as 750 m/s in about 8 minutes. This example shows that the convection can respond to a sudden IMF change practically simultaneously (~2 min) over the entire high-latitude zone and reconfigure from a pattern characteristic of Bz+ to one characteristic of Bz- in a very short (2--4 min) time. ¿ 1998 American Geophysical Union