Measurement of the Vertical Nonuniformity of the Plasma Sheath in a Complex Plasma

Employing an attenuated oscillation method, the anisotropic interaction force between two vertically aligned dust particles located in the sheath of a complex plasma was measured experimentally based on a linear approximation to the interaction force. Experimental data show that, although both particles experience a repulsive interaction force, the upper particle experiences a stronger magnitude force than does the lower particle. This result can be explained by the ion wakefield since the lower particle resides within the ion wakefield generated by the streaming ions passing through the sheath and around the upper particle.