Sagdeev potential analysis for positively charged dust grains in nonthermal dusty plasma near Mars

The existence of nonlinear dust acoustic (DA) solitary waves for positive dust grains is examined in a dusty plasma (DP). Four charging currents are considered: photoemission, secondary electrons, as well as the electron and ion currents. The nonthermal ion charging current is presented for the first time. Introducing nonthermal ions in the DP system aids in increasing the net positive dust charge, though raising their temperature goes in the opposite direction. There is a maximum value of the ambient plasma potential allowing positive dust charges. The energy equation for the DP system is obtained. The allowed Mach number regime is expanded due to the presence of the nonthermal ions. In the present model, the rarefactive soliton is only permitted. For a constant dust charge, there is a maximum limit of the wave velocity attached to the DA soliton solution. The charging fluctuation always contributes to reducing the amplitude and the width of the produced soliton. The ratio of ion to electron number densities and the nonthermal parameter are two competitors to determine the amplitude and the width of the resultant solitons. Implications of these results to the recorded space phenomena in Martian space and tropical mesosphere are briefly discussed. (C) 2007 American Institute of Physics.