We use E¿B data from the Saint-Santin incoherent scatter facility to study the behavior of mid-latitude ionospheric electric fields during magnetic storms and substorms. To this end, we analyze the relation between departures of the Saint-Santin field from its quiet day values and the simultaneous variations of parameters characterizing the state of magnetospheric convection: the IMF BZ component, the auroral electrojet index, and the ring current inflation rate as deduced from time variations of the Dst index. Mid-latitude E ¿ B drift disturbances, when they occur during substorms, are generally associated with a large southward value of BZ and with large values of the ring current inflation rate. They are also associated in several instances with an activation of the eastward electrojet in the afternoon and evening sectors. Large values of the drift disturbances are also observed during magnetic storms, but their relationship to the large-scale convection parameters monitored does not seem to be reductible to the simple real-time relationships found for the substorm cases. This suggests that an additional mechanism characterized by a longer time constant may be at work. We calculate the average disturbance drifts for Kp≥30 and express them as a diurnal harmonic function of local time. There is no clear effect in the north-south drifts (east-west electric fields), but the east-west drifts (north-south electric fields) display large average disturbances. They are westward at all local times, maximize at 2200 LT with a 75-m/s amplitude, but are very small in the 0612 LT quadrant. A 34-m/s westward steady component and a 26-m/s diurnal oscillation are the two dominant terms of its harmonic content. This pattern is interpreted in the third companion paper.