Members within the Astrophysics and Space Science Theory Group (ASSTG) conduct research in a variety of areas with current research topics including complex (dusty) plasmas, gravitoelectrodynamics, protoplanetary / protostellar evolution, grain charging in dense and tenuous dusty plasmas, grain coagulation in nebular clouds, ordered grain lattice formation within dusty plasmas, wave propagation through ordered and disordered dusty plasmas as well as numerical modeling of shock (low and hypervelocity impact) physics. Many of the above are relatively new research areas and as such show great potential for growth.
Specific areas of current interest include:
Dispersion Relations in Complex Plasmas. The formation of 2D coulomb crystals in low temperature plasmas is one of several interesting problems in a new area of physics called complex plasmas. In a Yukawa system, charged microparticles interact with one another through a screened Coulomb potential allowing system ordering ranging from gas->liquid->solid phases. Compared with colloidal suspensions, the particles are weakly damped allowing the excitation (via thermal perturbation or laser manipulation) of longitudinal, transverse and optical mode (optic-like inverse dispersion) waves. Determining the dispersion relations of such waves provides a sensitive diagnostic for use on experimental systems as well as provides data for basic physics research.
Coagulation of charged micron-sized dust.
The coagulation of micron-sized dust plays an early role in the process of protoplanetary formation. Protoplanets are formed from the gas and dust left in the circumstellar disk of a newly formed star. This gas and dust must coalesce on a relatively short time scale. The dust is immersed in a plasma environment and thus becomes charged. Depending on the plasma conditions and the dust size distribution, the dust particles may become oppositely charged, which would enhance coagulation rates. The dust also forms fluffy fractal aggregates as the particles collide and stick. This also enhances the coagulation rate as the fluffy aggregates have a larger cross-sectional area for future collisions.
Micro-, Meso- and Nanoscale Formation in Complex Plasmas.
The formation of micro-, meso- or nanoscale crystals, clusters and balls in low temperature plasmas is a recent (and very interesting) problem in complex plasmas. In a Yukawa system, charged microparticles interact with one another through a screened Coulomb potential allowing system ordering ranging from gas->liquid->solid phases. These particles self assemble into structured formations depending on the specific boundary conditions. This research area is of great interest in nanofabrication and manipulation and is on the cutting edge of nanoscience research.
Dynamics of charged grains in Saturn's F Ring.
Saturn's F Ring is a dynamic system with Voyager pictures revealing braids, kinks, and clumps that evolve in a matter of weeks or months. The plasma conditions in the F Ring are unknown, but it is likely that the micron sized dust in the ring is weakly charged. Saturn's magnetic field can impart a significant perturbation to the orbits of of these grains, while having negligible effect on the larger grains. This leads to a size-sorting mechanism which may influence the formation of braids and clumps.