Abstract. Experiments with the poloidal ring of 32 plane electrodes were performed on the CASTOR tokamak (R = 0.4 m, a = 0.06 m, B = 1 T) to measure, for the first time, the complete poloidal structure of the electrostatic edge turbulence. In addition, the possibility of active modification of the edge turbulence was checked. The main results are as follows: Quite regular turbulent structures with the pronounced poloidal periodicity are observed by passive measuring signals of the individual electrodes. The dominant poloidal mode number, m = 6-8, is approximately of the same value as the edge safety factor. Propagating waves of potential (f = 10-40 kHz) with the wave numbers in the range of m = 2-8, applied to the ring of the electrodes, modify the edge turbulence significantly due to their interaction with turbulent structures.