Self-modulation of low-frequency oscillations in a plasma

Experimental results are reported on the self-modulation of low-frequency oscillations in a plasma. The phenomenon is observed to occur at large amplitudes above a threshold. This is clearly shown by violent changes in the envelope form of externally modulated oscillations. Resultant spiky forms of the oscillation envelopes are observed to change strongly depending on parameters such as the rf frequency, the rf amplitude, and so on. Furthermore, spectral observations give additional information on the properties of the spiky oscillations. Finally, the observed phenomenon is qualitatively interpreted using a theory on the parametric process.