Observation of the ponderomotive effect in an inductive plasma

A modification of the plasma density and the dc ambipolar potential profile by the ponderomotive force has been observed, for the first time, in an inductively coupled plasma (ICP) at low gas pressure. This ponderomotive effect was observed only at a low excitation frequency where the rf Lorentz force acting on electrons in the skin layer prevails over the rf electric field force. It is shown that this ponderomotive effect in an ICP is possible only at a condition of an anomalous skin effect when the classical formula for the ponderomotive force is no longer valid.