Microturbulence


Microturbulence

Microturbulence is a form of turbulence that varies over small distance scales. (Large-scale turbulence is called macroturbulence.)

Contents

Stellar

Microturbulence is one of several mechanisms that can cause broadening of the absorption lines in the stellar spectrum.[1] Stellar microturbulence varies with the effective temperature and the surface gravity.[2]

The microturbulent velocity is defined as the microscale non-thermal component of the gas velocity in the region of spectral line formation.[3] Convection is the mechanism believed to be responsible for the observed turbulent velocity field, both in low mass stars and massive stars. When examined by a spectroscope, the velocity of the convective gas along the line of sight produces Doppler shifts in the absorption bands. It is the distribution of these velocities along the line of sight that produces the microturbulence broadening of the absorption lines in low mass stars that have convective envelopes. In massive stars convection can be present only in small regions below the surface; these sub-surface convection zones can excite turbulence at the stellar surface through the emission of acoustic and gravity waves.[4] The strength of the microturbulence (symbolized by ξ, in units of km s-1) can be determined by comparing the broadening of strong lines versus weak lines.[5]

Magnetic nuclear fusion

Microturbulence plays a critical role in energy transport during magnetic nuclear fusion experiments, such as the Tokamak.[6]

Oceanography

References

  1. ^ De Jager, C. (1954). "High-energy Microturbulence in the Solar Photosphere". Nature 173 (4406): 680–1. Bibcode 1954Natur.173..680D. doi:10.1038/173680b0. http://www.nature.com/nature/journal/v173/n4406/abs/173680b0.html. Retrieved 2007-05-21. 
  2. ^ Montalban, J.; Nendwich, J.; Heiter, U.; Kupka, F.; Paunzen, E.; Smalley, B. (1999). "The Effect of the microturbulence parameter on the Color-Magnitude Diagram". Reports on Progress in Physics 61 (S239): 77–115. Bibcode 2007IAUS..239..166M. doi:10.1017/S1743921307000361. 
  3. ^ Cantiello, M. et al. (2008). On the origin of Microturbulence in hot stars. http://www.astro.uu.nl/~cantiell/articles/liege1.pdf. 
  4. ^ Cantiello, M. et al. (2009); Langer, N.; Brott, I.; De Koter, A.; Shore, S. N.; Vink, J. S.; Voegler, A.; Lennon, D. J. et al. (2009). "Sub-surface convection zones in hot massive stars and their observable consequences". Astronomy and Astrophysics 499 (1): 279. arXiv:0903.2049. Bibcode 2009A&A...499..279C. doi:10.1051/0004-6361/200911643. 
  5. ^ Briley, Michael (July 13, 2006). "Stellar Properties from Spectral Lines: Introduction". University of Wisconsin. http://www.phys.uwosh.edu/mike/exercises/lines/lines.html. Retrieved 2007-05-21. 
  6. ^ Nevins, W.M. (August 21, 2006). "The Plasma Microturbulence Project". Lawrence Livermore National Laboratory. http://www.scidac.gov/FES/FES_PMP/reports/PMP2004Annual.html. Retrieved 2007-05-21. 

External links



Wikimedia Foundation. 2010.

Look at other dictionaries:

  • microturbulence — noun Turbulence on a small scale …   Wiktionary

  • Model photosphere — Some essential steps in model atmosphere analysis for determining stellar abundances (Figure by Bengt Gustafsson, Astronomical Observatory, Uppsala). The photosphere denotes those solar or stellar surface layers from which optical radiation… …   Wikipedia

  • Stellar rotation — is the angular motion of a star about its axis. The rate of rotation can be measured from the spectrum of the star, or by timing the movements of active features on the surface.The rotation of a star produces an equatorial bulge due to… …   Wikipedia

  • Apparent magnitude — Asteroid 65 Cybele and 2 stars with their magnitudes labeled The apparent magnitude (m) of a celestial body is a measure of its brightness as seen by an observer on Earth, normalized to the value it would have in the absence of the atmosphere.… …   Wikipedia

  • Corona — This article is about the astronomical term. For other uses, see Corona (disambiguation). During a total solar eclipse, the solar corona can be seen with the naked eye. A corona is a type of plasma atmosphere of the Sun or other celestial body,… …   Wikipedia

  • Main sequence — A Hertzsprung Russell diagram plots the actual brightness (or absolute magnitude) of a star against its color index (represented as B V). The main sequence is visible as a prominent diagonal band that runs from the upper left to the lower right.… …   Wikipedia

  • Molecular cloud — See also: Solar nebula Within a few million years the light from bright stars will have boiled away this molecular cloud of gas and dust. The cloud has broken off from the Carina Nebula. Newly formed stars are visible nearby, their images… …   Wikipedia

  • Neutron star — redirects here. For the story by Larry Niven, see Neutron Star (short story). Neutron stars crush half a million times more mass than Earth into a sphere no larger than Manhattan. A neutron star is a type of stellar remnant that can result from… …   Wikipedia

  • Star — For other uses, see Star (disambiguation) …   Wikipedia

  • Supernova — This article is about the astronomical event. For other uses, see Supernova (disambiguation). Multiwavelength X ray, infrared, and optical compilation image of Kepler s supernova remnant, SN 1604. A supernova is a stellar explosion that is more… …   Wikipedia


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.