The proposal addresses studies of kinetic instabilities in hot dilute inhomogeneous plasmas. Such inhomogeneities are present in particular also for plasmas in contact with solid objects as dust or metallic objects such as spacecrafts. Kinetic instabiliti es originate from properties of the velocity distribution functions of the charged particles, i.e. from their phase space distributions, and traditional fluid models are inadequate for their description and modeling. The conditions for such instabilities and their nonlinear evolution have been studied in great detail by analytical, experimental and numerical methods. It has been demonstrated that these types of plasma instabilities can saturate in weakly or strongly turbulent states, somewhat in contrast to fluid turbulence, where usually only a fully developed strongly turbulent state is observed. In models of weak plasma turbulence, the basic modes are assumed to follow (at least approximately) the dispersion relations obtained by a linearized model, an d the plasma nonlinearities couple the dynamics of these modes. For the strongly turbulent state, the linearized analysis does no longer identify the basic constituents of the plasma dynamics, and our studies will be concentrated on this strongly turbulen t state.
The methods used in the project will emphasize numerical simulations based on Particle-in-Cell codes, supported by analytical studies for investigations of current and beam driven plasma instabilities with finite geometries, where we will deal w ith plasmas in contact with solid surfaces, in particular.
The main results of the project will concern properties of dust particles in contact with plasmas. The material (conducting or insulating) and surface conditions are likely to be important for th ese properties. Plasma probes can be seen as a particular case of plasma-solid interactions, and related studies are included in the project.