Local structures of the potential and ion saturation current profile are found in an asymmetric ion sheath under which the ion sheath instability is excited. In the high density region, the local structure of the ion saturation current profile was observed near the sheath edge for the first time. The formation of the sheath structure is confirmed by the numerical simulation using the particle-in-cell code. In this simulation, it was observed that the space potential oscillates in the both two regions devided by the asymmetric ion sheath and, the potential swell like as the virtual anode oscillate near the sheath edge in the driver region. It was concluded that the oscillation of the space potentials and the ion bounce motion inside the sheath lead to excite and suppress the grid current fluctuation from these experimental and numerical results.
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