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Showing 1 to 20 of 23 for “"ambipolar diffusion"”.
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Ambipolar Diffusion in Interstellar Clouds: One-Dimensional, Isothermal Collapse
… neutral densities n(,n) < 10('9) cm('-3) due to ambipolar diffusion alone. Ambipolar diffusion sets in at gas densities larger than those by which the bulk of the angular momentum problem is resolved by magnetic braking.
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Ambipolar diffusion in interstellar clouds: One-dimensional, isothermal collapse
Submitted by Carolyn Mead (cmead2@illinois.edu) on 2011-06-09T14:05:17Z No. of bitstreams: 1 1983_paleologou.pdf: 2881441 bytes, checksum: 2daf79df8e0b48e52a8eeda9a54d11bd (MD5)
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The role of ambipolar diffusion in the formation of interstellar cloud cores and protostars
… their non-linear evolution/contraction owing to ambipolar diffusion. An important result is the selection by ambipolar diffusion of a characteristic mass comparable to a solar mass.
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The role of ambipolar diffusion in the formation of interstellar cloud cores and protostars
… their non-linear evolution/ contraction owing to ambipolar diffusion. An important result is the selection by ambipolar diffusion of a characteristic mass comparable to a solar mass.
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The Role of MHD Waves and Ambipolar Diffusion in the Formation of Interstellar Cloud Cores and Protostars
… formation and contraction of cloud cores due to ambipolar diffusion in isothermal, magnetic molecular clouds in the presence of MHD waves. The model clouds are initially in exact equilibrium states, with magnetic, thermal-pressure, and wave-pressure forces balancing self-gravity. An energy …
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The role of magnetic braking and ambipolar diffusion in the formation of interstellar cloud cores and protostars
… angular momentum by torsional Alfven waves) and ambipolar diffusion (the relative drift between neutral and charged particles). A core forms and ultimately evolves much more rapidly than the surrounding cloud. A core-envelope separation is demonstrated, and the final mass and angular momentum of …
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The effects of ambipolar diffusion, dust, and ultraviolet radiation in the formation of cores and protostars in interstellar molecular clouds
… with respect to plasma and magnetic field (ambipolar diffusion), which allows a cloud to gradually increase its central mass-to-flux ratio until it reaches the critical value for gravitational collapse. Beyond this stage, the magnetically supercritical core contracts dynamically, while the …
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Star formation in the presence of magnetic fields: Molecular cloud core formation and dynamical contraction due to ambipolar diffusion; a simulation with axial symmetry
… ratio in a cloud's central flux tubes (ambipolar diffusion) takes place at an ever-increasing rate, leading to the formation of high-density cores, typically after 8 million years of quasi-static contraction. Eventually, the central mass-to-flux ratio exceeds the critical value for …
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Investigation of an electron-beam sustained discharge in helium
… toward discharges in helium where radial ambipolar diffusion is the dominant plasma loss mechanism. This investigation is made in support of a continuing, technology-driven program to apply the unique attributes of the EBSD to plasma processing applications in the growth and etching of …
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The Nonisothermal Stage of Magnetic Star Formation
… of both elastic and inelastic collisions to ambipolar diffusion and Ohmic dissipation. The species abundances are calculated using an extensive chemical-equilibrium network. The thermal evolution of the protostellar core and its affect on the dynamics are followed by employing the grey …
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Fragmentation of magnetically-supported, weakly-ionized molecular clouds
… to the drift between the ions and the neutrals, ambipolar diffusion. To follow the evolution of the model clouds, we extended the publicly-available Zeus-MP code to include the effects of nonideal magnetohydrodynamics and have modified several algo- rithms to improve accuracy and convergence. We …
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Growth and properties of hydrogenated amorphous silicon carbon alloys by DC reactive magnetron sputtering
… defect states DOS, Urbach energy E$\rm\sb{U},$ ambipolar diffusion length L$\rm\sb{h},$ photoconductive mobility-lifetime product $\mu\tau$ and dark conductivity $\rm\sigma\sb{D}$ for Tauc bandgap E$\rm\sb{g}\approx$ 1.90 eV. We attribute the quality of these films to the translational energy of …
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Observational study of the role of magnetic fields in star formation
… of the regions observed. Until recently, only ambipolar diffusion theory had numerical models that simulated possible physical results that could be compared to observational data. These theories interpret the models in terms of a physical parameter: the ratio of the mass to the magnetic flux …
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Protostar Formation in Magnetic Clouds: The Phase Beyond Ion Detachment
… of different magnetic flux-loss mechanisms (ambipolar diffusion and Ohmic dissipation) in the resolution of the magnetic flux problem of star formation. During the accretion phase, we discover new phenomena, such as the formation and dissipation of a series of magnetically driven shocks that …
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Small-scale fluctuations in D-region ionization due to hydrodynamic turbulence
… is derived for the drift, distortion and diffusion relative to the neutral gas of ionization inhomogeneities in the presence of both uniform and turbulent motion of the neutral gas with uniform magnetic and gravitational fields. New effects are found which are due to the production of …
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From Large-scale Molecular Clouds to Filaments and Cores : Unveiling the Role of the Magnetic Fields in Star Formation
… non-ideal magnetohydrodynamic simulations (with ambipolar diffusion) to see the effect of magnetic fields on the evolution of the column density probability distribution function (PDF). Our results indicate a systematic dependence of the column density PDF of molecular clouds on magnetic field …
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Dispersive Transport and Drift Mobilities in Methylammonium Lead Iodide Perovskites
… unusually long photocharge carrier lifetimes and ambipolar diffusion. These discoveries changed the geometry of the solar cell from a dye-sensitized structure to n-i-p. The work done in this dissertation focuses on thin film methyl-ammonium lead iodide perovskites in n-i-p structures made by the …
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Multifluid Kelvin-Helmholtz instability in weakly ionised astrophysical plasmas
… a result of including the multlifluid effects of ambipolar diffusion and the Hall effect are isolated and individually studied in chapters 4 and 5 respectively. Finally, chapter 6 provides an in-depth examination of the respective roles these nonideal effects have in a multifluid astrophysical …
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Theoretical Study of Electron Transport and Trapping in Solvated Titanium Dioxide Nanoparticles
… effect. The barrier heights imply that concerted ambipolar diffusion of the Li+/e − can occur under thermal activation, but it is energetically disfavored for proton/e− pair. Those results advance our understanding of the effect of the cation and solvent on the density of states (DOS) of electron …
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A Homegrown DSMC-PIC Model for Electric Propulsion
… the accuracy and capabilities of the model. An ambipolar diffusion test case is compared to a neutral diffusion case and the electric field is shown to stabilize the diffusion rate. A steady state flow test case shows the simulation is able to stabilize and solve the electric potential for a …
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