Combined Effect of Secondary Electron Emission, Plasma Ion and Electron Number Density Variation due to Dust Charging and Ionization-Recombination Processes on Dust Ion Acoustic Wave Propagation

Abstract

In a dusty plasma, in addition to influencing the dust charge state the secondary electron emission also leads to an enhancement of the electron number density. For proper accounting for secondary electron emission effect one has therefore, for the sake of consistency, also to take into account the ambient electron and ion loss due to charging collisions. The existence of a steady state for the dusty plasma is possible only through compensation of such particle losses or gain – a likely candidate for which are ionization and recombination processes in dusty plasma. Taking into account the combined effects all these processes and assuming that the frequencies of the various types of interparticle collisions associated with the above-mentioned processes are much less than the dust ion acoustic (DIA) frequency it is shown that a small perturbation of the steady state of the dusty plasma may result in DIA wave growth provided the ionization rate is sufficiently high. Threshold values of the ratio of the ionization rate to recombination rate depending on different plasma parameters are shown graphically. The analysis presented is restricted to the case when the dust charge remains negative. It is seen that instability persists even when there is no secondary emission. The threshold for instability is lower for smaller values of the dimensionless charge parameter z0 = Zd0e2/aTe when secondary emission takes place, compared to the case when it is absent. The situation tends to get reversed as z0 increases. The possibility of the existence of such instability was not noted earlier.