Analyses of the proton cyclotron echoes observed on the Alouette 2 ionograms, in more than 800 examples, indicate that the echoes are produced in a range within ¿25¿ width of the magnetic dipole latitude centered at the magnetic equator. The generation mechanism of these proton cyclotron echoes is clarified here as follows: (1) the transmitted RF pulse makes an electrostatic plasma wave that produces a fast electron stream in opposite directions with respect to the wave propagation direction during damping processes of the wave; (2) the RF pulse also produces a proton concentration surrounding the antenna due to negative excursion of the antenna potential; (3) the proton concentration produced is repeated each proton cyclotron period and makes a pseudo-wave of the electric field; and (4) the encounter of the electron stream with the pseudo-wave due to the proton concentration makes a plasma wave with frequency in the transmitted RF range. The place where the electron stream encounters the pseudo-wave should be located at a position relatively close to the satellite for the observation of the RF echoes.