First direct ground‐based measurements of electron drift in the ionospheric F region

For the first time, vertical electron drift velocities in the F region of the ionosphere have been directly determined using the Doppler shift of the electron component of the incoherent‐scatter spectra. Simultaneous measurements of ion drift velocities were also made. A large difference between the electron and ion velocities of the order of 100 ms−1 with corresponding currents of 10−5 Am−2 was observed at sunrise. The most likely source of these currents appears to be the action of the local thermospheric wind on the large conductivity gradients associated with the sunrise line.