Abstract: | The properties of on drift waves observed in the rotating magnetized plasma column of the PSI‐2 are analysed. Their parallel wave numbers are found to be nearly zero, the measured azimuthal dispersion relation is approximately linear, and the azimuthal phase velocity is nearly equal to the azimuthal on drift velocity. Furthermore, the potential fluctuations always lag behind the density fluctuations with a phase shift slightly below π. A simple analytical model, describing the potential‐and density distribution of the ion drift wave, shows the underlying mechanism of the on drift instability. Finally, a classification of the observed on drift instability is given. |