Protostar Formation in Magnetic Clouds: The Phase Beyond Ion Detachment
Tassis, Konstantinos
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https://hdl.handle.net/2142/85179
Description
Title
Protostar Formation in Magnetic Clouds: The Phase Beyond Ion Detachment
Author(s)
Tassis, Konstantinos
Issue Date
2005
Doctoral Committee Chair(s)
Telemachos Ch. Mouschovias
Department of Study
Astronomy
Discipline
Astronomy
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Physics, Astronomy and Astrophysics
Language
eng
Abstract
"We follow the formation and evolution of a molecular cloud core from mean molecular cloud densities to a density enhancement of twelve orders of magnitude, by which stage the magnetic flux problem of star formation is expected to be resolved. We use the nonideal six-fluid MHD equations, which we solve using an adaptive-grid numerical code. In the central part of the core, an opaque region forms above a certain density, where isothermality breaks down. We treat this region using the adiabatic approximation, while the density at which the transition occurs is treated as a free parameter, within reasonable limits suggested by observations. To follow the evolution of the isothermal disk surrounding the formed protostar at even later times, we introduce a ""central sink"" which allows us to exclude the central region from our computations, while still accounting for the physical effects of the accumulating mass and magnetic flux. In this way, we follow the accretion process onto the protostar until 1 M⊙ is accumulated in the central sink. We evaluate the relative importance 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 occur in a quasi-periodic fashion."
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