The role of magnetic braking and ambipolar diffusion in the formation of interstellar cloud cores and protostars
Basu, Shantanu
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https://hdl.handle.net/2142/20927
Description
Title
The role of magnetic braking and ambipolar diffusion in the formation of interstellar cloud cores and protostars
Author(s)
Basu, Shantanu
Issue Date
1993
Doctoral Committee Chair(s)
Mouschovias, T. Ch.
Department of Study
Physics
Discipline
Physics
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Date of Ingest
2011-05-07T12:53:20Z
Keyword(s)
Physics, General
Physics, Astronomy and Astrophysics
Language
eng
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.
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