Some new experimental aspects of ion acoustic and dust acoustic waves

Ion acoustic wave is one of the most fundamental wave modes in unmagnetized low temperature plasma. Experimentally most of the linear and nonlinear characteristics of the IA waves are investigated. When mixed with additional negative ion component, however, the IA wave mode is modified. Interestingly, at a critical concentration of negative ion the ion wave mode become modulationally unstable for wide range wavenumbers and thus fulfils the condition for generation of Peregrine soliton -a prototype of oceanic rogue wave. The Peregrine soliton is a doubly localized nonlinear structure described by the nonlinear Schrodinger equation (NLSE). The dusty plasma on the other hand contains additional micron or sub-micron sized particles in the plasma and supports very low frequency waves namely dust acoustic waves (with characteristics frequency ~ few Hz- tens of Hz) analogous to ion acoustic waves. In the nonlinear regime the dust acoustic waves can be transformed into dust acoustic solitons. Experimentally these waves are visible with laser light scattering and captured in high speed video camera. In laboratory dusty plasma can be made to flow at controllable speed and when allowed to flow past an obstacle can generate nonlinear structures e.g., bow shock, vortex and other complex structures. Some experimental aspects of linear and nonlinear ion acoustic and dust acoustic waves and nonlinear structures in dusty plasma will be discussed in the presentation. (author)