Observation of the Upper-Hybrid Soliton and Its Recurring Behaviour

A density cavity was observed at the upper-hybrid resonance layer when a high-power microwave of the extraordinary mode was injected into an afterglow plasma column in a uniform magnetic field. Further, when the upper-hybrid resonance layer was at the center of the plasma column, the formation of the density cavity recurred and the microwave power transmitted through the plasma showed oscillatory behaviour. These results can be explained by the modulational instability at the upper-hybrid frequency and the formation of an upper-hybrid soliton.