The up-down potential asymmetry in the toroidal magnetic plasma iscaused by the separation of ions and electrons due to the toroidicity of theconfining magnetic field and/or due to the effect of flow along the verticalmagnetic field. In the SINP tokamak an interesting phenomenon of inversion ofup-down asymmetry during a discharge has been observed experimentally. Theorigin of this up-down potential asymmetry and its inversion is attributed totwo oppositely directed vertical velocities, causing the separation of chargedspecies.