The effects of the great magnetic storm of July 15, 2000 on the equatorial ionosphere have been studied by ground-based and satellite in-situ measurements. A large westward plasma drift in the evening equatorial ionosphere was observed as a result of the ionospheric disturbance dynamo. In that environment, the IMF Bz turned southward and presumably caused penetration of E-fields to low latitudes. This E-field initiated the onset of 250 MHz and L-band scintillations at Ascension Island (15°W) and precipitous TEC decrease at Fortaleza, Brazil (38°W), bounding the narrow longitude region in the South Atlantic. These impulsive ionospheric effects were extremely well correlated with abrupt decreases of SYM-H (1-min resolution Dst). The DMSP in-situ measurements showed the presence of severe ion density bite-outs extending over 30° latitude in the South Atlantic Magnetic Anomaly region. The ROCSAT-1 satellite measured upward and large southward ion drifts in the same sector.