It is shown that, under certain conditions, the density fluctuation spectrum calculated from the linear radial eigenfunction associated with a toroidal version of the drift rippling instability presents a significant up-down asymmetry. The wave propagates in the direction of the electron diamagnetic velocity. Its frequency is ω0 = (1 + 1.71 ηe)whereis the diamagnetic frequency and ηe = (d ln Te/dr)/(d ln N/dr).