On Scaling Laws and Alfvenic Magnetic Fluctuations in Molecular Clouds

• Main Author: Xie, Taoling
• Format: Journal Article
• Language: English
• Published: 20-11-1996
• Subjects: Physics - Astrophysics of Galaxies; Physics - Cosmology and Nongalactic Astrophysics; Physics - Earth and Planetary Astrophysics; Physics - High Energy Astrophysical Phenomena; Physics - Instrumentation and Methods for Astrophysics; Physics - Solar and Stellar Astrophysics
• DOI: 10.48550/arxiv.astro-ph/9611153

Under the basic assumption that the observed turbulent motions in molecular
clouds are Alfvenic waves or turbulence, we emphasize that the Doppler
broadening of molecular line profiles directly measures the velocity amplitudes
of the waves instead of the Alfven velocity. Assuming an equipartition between
the kinetic energy and the Alfvenic magnetic energy, we further propose the
hypothesis that observed standard scaling laws in molecular clouds imply a
roughly scale-independent fluctuating magnetic field, which might be understood
as a result of strong wave-wave interactions and subsequent energy cascade. We
predict that $\sigma_{v}\propto \rho^{-0.5}$ is a more basic and robust
relation in that it may approximately hold in any regions where the spatial
energy density distribution is primarily determined by wave-wave interactions,
including gravitationally unbound regions. We also discuss the fact that a
scale-independent $\sigma_{B}^{2}$ appears to contradict existing 1-D and 2-D
computer simulations of MHD turbulence in molecular clouds.