Effects of the collisional damping on a nonresonant parametric instability near the lower-hybrid frequency

It is experimentally verified that the dominant region of the nonresonant ion-quasimode is 1<ω0/ωsub(LH)<3 (ω0: pump frequency, ωsub(LH): lower-hybrid frequency), by controlling the linear Landau damping and the collisional damping of the parametric decay waves by varying neutral gas pressure, and this ion-quasimode have the maximum amplitude at the ratio ω0/ωsub(LH) asymptotically equals √2. The measured frequency, amplitude, and threshold of the low frequency decay wave are in good agreement with the Porkolab's theory of the nonresonant ion-quasimode including the effect of electron-neutral collisions. (author)