{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/20927"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/20927","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"The role of magnetic braking and ambipolar diffusion in the formation of interstellar cloud cores and protostars","abstract":"The means by which parent molecular clouds give birth to stars constitutes a fundamental unsolved problem in astrophysics. Magnetic fields, which dominate thermal-pressure as a source of support against self-gravity in interstellar molecular clouds, are an important regulator of star-formation. We study the formation and contraction of fragments (or cores) in isothermal, rotating, magnetic molecular clouds. Initial states are exact equilibria with magnetic, centrifugal, and thermal-pressure forces balancing self-gravity. The full nonlinear two-fluid MHD equations for a flattened disk are solved numerically to obtain the cloud's evolution. The evolution of the model clouds is initiated entirely by the onset of magnetic braking (the transport of 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 the core is determined. Predictions are made for the spatial profiles of important physical quantities, e.g., angular velocity, density, magnetic field. A full parameter study is conducted.","abstract_html":"The means by which parent molecular clouds give birth to stars constitutes a fundamental unsolved problem in astrophysics. Magnetic fields, which dominate thermal-pressure as a source of support against self-gravity in interstellar molecular clouds, are an important regulator of star-formation. We study the formation and contraction of fragments (or cores) in isothermal, rotating, magnetic molecular clouds. Initial states are exact equilibria with magnetic, centrifugal, and thermal-pressure forces balancing self-gravity. The full nonlinear two-fluid MHD equations for a flattened disk are solved numerically to obtain the cloud's evolution. The evolution of the model clouds is initiated entirely by the onset of magnetic braking (the transport of 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 the core is determined. Predictions are made for the spatial profiles of important physical quantities, e.g., angular velocity, density, magnetic field. A full parameter study is conducted.","abstract_has_math":false,"creators":["Basu, Shantanu"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Physics","degree_department":null,"school":null,"contributors":["Mouschovias, T. 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Magnetic fields, which dominate thermal-pressure as a source of support against self-gravity in interstellar molecular clouds, are an important regulator of star-formation. We study the formation and contraction of fragments (or cores) in isothermal, rotating, magnetic molecular clouds. Initial states are exact equilibria with magnetic, centrifugal, and thermal-pressure forces balancing self-gravity. The full nonlinear two-fluid MHD equations for a flattened disk are solved numerically to obtain the cloud's evolution. The evolution of the model clouds is initiated entirely by the onset of magnetic braking (the transport of 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 the core is determined. 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Ch."],"dc:creator":["Basu, Shantanu"],"dc:date":["2011-05-07T12:53:20Z","10000-01-01","1993"],"dc:description":["The means by which parent molecular clouds give birth to stars constitutes a fundamental unsolved problem in astrophysics. Magnetic fields, which dominate thermal-pressure as a source of support against self-gravity in interstellar molecular clouds, are an important regulator of star-formation. We study the formation and contraction of fragments (or cores) in isothermal, rotating, magnetic molecular clouds. Initial states are exact equilibria with magnetic, centrifugal, and thermal-pressure forces balancing self-gravity. The full nonlinear two-fluid MHD equations for a flattened disk are solved numerically to obtain the cloud's evolution. The evolution of the model clouds is initiated entirely by the onset of magnetic braking (the transport of 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 the core is determined. Predictions are made for the spatial profiles of important physical quantities, e.g., angular velocity, density, magnetic field. A full parameter study is conducted.","Made available in DSpace on 2011-05-07T12:53:20Z (GMT). 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