Mathematics – Metric Geometry
Scientific paper
May 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993aas...182.7501b&link_type=abstract
American Astronomical Society, 182nd AAS Meeting, #75.01D; Bulletin of the American Astronomical Society, Vol. 25, p.925
Mathematics
Metric Geometry
Scientific paper
We study the evolution of isothermal, rotating, magnetic, self-gravitating molecular clouds through numerical solution of the two-fluid MHD equations in axisymmetric geometry. The formation and contraction of cores (or fragments) is followed through both the quasistatic and dynamic phases of evolution, until the central density increases by six orders of magnitude. The evolution away from an initial equilibrium state is initiated entirely by magnetic braking (transport of angular momentum by torsional Alfven waves) and/or ambipolar diffusion (drift of neutrals relative to plasma). Typically, the mass in the central flux tubes initially increases on the ambipolar diffusion time scale, while magnetic braking enforces near corotation with the background medium. This phase continues until a magnetically and thermally supercritical core forms. Subsequently, the core evolves much more rapidly than its surroundings, creating a clear core-envelope separation. As far as rotation is concerned, the evolution of the central region occurs in three distinct phases: (i) an exponential decrease of the angular velocity Omega_c (t) due to effective magnetic braking, followed by (ii) a constant Omega phase, which lasts until a supercritical core forms. Then (iii) a constant angular momentum (J) phase sets in. A parameter study reveals that, by a central density enhancement of 10(6) (e.g. from 3 times 10(3) to 3 times 10(9) cm(-3) ), masses of protostellar cores are in the range ~ 1 - 30 Msun, and the corresponding specific angular momenta (J/M) are in the range ~ 10(19) - 3 times 10(21) cm(2) s(-1) , in agreement with protosolar-nebula and binary-star values.
Basu Sarbani
Mouschovias Telemachos Ch.
No associations
LandOfFree
Magnetic Braking and Ambipolar Diffusion in Molecular Clouds: Selection of Core Masses and Angular Momenta does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Magnetic Braking and Ambipolar Diffusion in Molecular Clouds: Selection of Core Masses and Angular Momenta, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magnetic Braking and Ambipolar Diffusion in Molecular Clouds: Selection of Core Masses and Angular Momenta will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1850824