Page 65 - swp0000.dvi

shown that, the values of critical wave numbers decrease with  and   

One of the most important aim of this work is the study of MI growth rate,

Γ properties with the population of nonthermal ions , the carrier wave
ˆ
number , the equilibrium density of hot (cold) dust grains  0 ( 0 ) and
the charge numbers for negatively charged hot (cold) dust,   (  ) In Figs.

(3.15-3.19), we noted that, MI growth rate Γ increases with population of

nonthermal ions  the charge numbers for negatively charged hot dust  
and the equilibrium density of cold dust grains  0 while decreases with

the equilibrium density of cold dust grains  0 and the charge numbers

for negatively charged cold dust   Accordingly, for   0 the bright
envelope solitons can exist for modulationally instability as in Fig. (3.20)

but for   0, we obtain a dark envelope soliton which is stable as in

Fig. (3.21). In summary, it is found that, the parameter of the population
ˆ
of nonthermal ions , the carrier wave number , the equilibrium density
of hot (cold) dust grains  0 ( 0 ) and the charge numbers for negatively

charged hot (cold) dust,   (  ) would improve the properties of of the dust
acoustic MI and envelope solitons and the results presented here could be

helpful for understanding of dust acoustic features in dusty plasma of

Saturn F-rings.

52