CASPER
Permanent URI for this communityhttps://hdl.handle.net/2104/5501
CASPER conducts fundamental research in astrophysics, early universe cosmology, space physics, superstring / M theory, complex (dusty) plasma physics, hypervelocity impact (shock) physics and laser hypervelocity impact simulation physics.
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Browsing CASPER by Author "Barge, Laura"
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Item Finite coulomb crystal formation(Advances in Space Research, 2004) Vasut, John; Hyde, Truell Wayne.; Barge, LauraDust particles immersed within a plasma environment, such as those found in planetary rings or comets, will acquire an electric charge. If the ratio of the inter-particle potential energy to average kinetic energy is large enough the particles will form either a “liquid” structure with short-range ordering or a crystalline structure with long-range ordering. Since their discovery in laboratory environments in 1994, such crystals have been the subject of a variety of experimental, theoretical and numerical investigations. Most numerical and theoretical investigations have examined infinite systems assuming periodic boundary conditions. Since experimentally observed crystals can be comprised of a few hundred particles, this often leads to discrepancies between predicted theoretical results and experimental data. In addition, recent studies have concentrated on the importance of random charge variations between individual dust particles, but very little on the importance of size variations between the grains. Such size variations naturally lead to inter-grain charge variations which can easily become more important than those due to random charge fluctuations (which are typically less than one percent). Although such size variations can be largely eliminated experimentally by introducing mono-dispersive particles, many laboratory systems and all astrophysical environments contain significant size distributions. This study utilizes a program to find the equilibrium positions of a dusty plasma system as well as a modified Barnes–Hut code to model the dynamic behavior of such systems. It is shown that in terms of inter-particle spacing and ordering, finite systems are significantly different than infinite ones, particularly for the most-highly ordered states.Item A model of coagulation in dust clouds during grain charging(Advances in Space Research, 2004) Barge, Laura; Matthews, Lorin Swint.; Hyde, Truell Wayne.Initially uncharged grains in space and laboratory plasma environments become charged due to currents driven by potential differences in the dusty plasma. Certain macroscopic effects such as coagulation of smaller grains into larger ones or fluffy aggregates can be affected during this initial grain charging phase. The charging profiles of micron- and submicron-sized dust grains immersed in such plasma environments are strongly size- and temperature-dependent, and under certain conditions, the dust cloud can have various configurations of charged grains. Using a standard grain charging model along with a modified Barnes–Hut tree code for calculating grain dynamics, this paper examines the effect of including initial grain charging in coagulation of clouds of negative grains, positive grains, and a mixture of oppositely charged grains. The immediate application to coagulation during transient dusty plasma conditions is discussed.