The role of ambipolar diffusion in the formation of interstellar cloud cores and protostars
Morton, Scott Allyn
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https://hdl.handle.net/2142/18891
Description
Title
The role of ambipolar diffusion in the formation of interstellar cloud cores and protostars
Author(s)
Morton, Scott Allyn
Issue Date
1991
Doctoral Committee Chair(s)
Mouschovias, T. Ch.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
ambipolar diffusion
interstellar cloud cores
protostars
formation of stars
astrophysics
Language
en
Abstract
The formation of stars is a fundamental unsolved problem in astrophysics. Interstellar molecular
clouds, observed to be the birth place of stars, have masses much larger than those of typical
stars. Observed densities, temperatures, and strengths of well-ordered magnetic fields imply
that magnetic forces, transmitted to the neutral fluid through collisions with ions, dominate
thermal forces in supporting these objects against self-gravity. The anisotropy of the Lorentz
force, which is always perpendicular to the magnetic field, allows a simplified treatment of the
dynamics involving motion along the magnetic field. We derive a reduced system of non-linear,
non-ideal magnetohydrodynamic equations by assuming a balance of thermal and gravitational
forces along the magnetic field. We then study both the stability of dense clouds as well as
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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