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Energy Transport, Overshoot, and Mixing in the Atmospheres of Very Cool Stars

Ludwig, Hans-Günter LU (2003) In Modelling of Stellar Atmospheres ; Proceedings of the 210th Symposium of the International Astronomical Union held at Uppsala University, Uppsala, Sweden, 17-21 June, 2002 210. p.113-125
Abstract
We constructed hydrodynamical model atmospheres for mid M-type main-, as well as pre-main-sequence objects. Despite the complex chemistry encountered in such cool atmospheres a reasonably accurate representation of the radiative transfer is possible. The detailed treatment of the interplay between radiation and convection in the hydrodynamical models allows to study processes usually not accessible within the framework conventional model atmospheres. In particular, we determined the efficiency of the convective energy transport, and the efficiency of mixing by convective overshoot. The convective transport efficiency expressed in terms of an equivalent mixing-length parameter amounts to values around 2 in the optically thick, and 2.8 in... (More)
We constructed hydrodynamical model atmospheres for mid M-type main-, as well as pre-main-sequence objects. Despite the complex chemistry encountered in such cool atmospheres a reasonably accurate representation of the radiative transfer is possible. The detailed treatment of the interplay between radiation and convection in the hydrodynamical models allows to study processes usually not accessible within the framework conventional model atmospheres. In particular, we determined the efficiency of the convective energy transport, and the efficiency of mixing by convective overshoot. The convective transport efficiency expressed in terms of an equivalent mixing-length parameter amounts to values around 2 in the optically thick, and 2.8 in the optically thin regime. The thermal structure of the formally convectively stable layers is little affected by convective overshoot and wave heating, i.e. stays close to radiative equilibrium. Mixing by convective overshoot shows an exponential decline with geometrical distance from the Schwarzschild stability boundary. The scale height of the decline varies with gravitational acceleration roughly as g(-1/2), with 0.5 pressure scale heights at log(g)=5.0. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Chapter in Book/Report/Conference proceeding
publication status
published
subject
in
Modelling of Stellar Atmospheres ; Proceedings of the 210th Symposium of the International Astronomical Union held at Uppsala University, Uppsala, Sweden, 17-21 June, 2002
editor
Piskunov, N.; Weiss, W.W. and Gray, D.F.
volume
210
pages
113 - 125
publisher
Astronomical Society of the Pacific
external identifiers
  • WOS:000243352400011
ISBN
1-583-81160-5
language
English
LU publication?
yes
id
65092e2a-92cd-4678-aaf1-b593b055a186 (old id 528240)
alternative location
http://arxiv.org/abs/astro-ph/0208583
date added to LUP
2007-09-21 12:21:06
date last changed
2016-04-16 07:34:50
@misc{65092e2a-92cd-4678-aaf1-b593b055a186,
  abstract     = {We constructed hydrodynamical model atmospheres for mid M-type main-, as well as pre-main-sequence objects. Despite the complex chemistry encountered in such cool atmospheres a reasonably accurate representation of the radiative transfer is possible. The detailed treatment of the interplay between radiation and convection in the hydrodynamical models allows to study processes usually not accessible within the framework conventional model atmospheres. In particular, we determined the efficiency of the convective energy transport, and the efficiency of mixing by convective overshoot. The convective transport efficiency expressed in terms of an equivalent mixing-length parameter amounts to values around 2 in the optically thick, and 2.8 in the optically thin regime. The thermal structure of the formally convectively stable layers is little affected by convective overshoot and wave heating, i.e. stays close to radiative equilibrium. Mixing by convective overshoot shows an exponential decline with geometrical distance from the Schwarzschild stability boundary. The scale height of the decline varies with gravitational acceleration roughly as g(-1/2), with 0.5 pressure scale heights at log(g)=5.0.},
  author       = {Ludwig, Hans-Günter},
  editor       = {Piskunov, N. and Weiss, W.W. and Gray, D.F.},
  isbn         = {1-583-81160-5},
  language     = {eng},
  pages        = {113--125},
  publisher    = {ARRAY(0xe63aa40)},
  series       = {Modelling of Stellar Atmospheres ; Proceedings of the 210th Symposium of the International Astronomical Union held at Uppsala University, Uppsala, Sweden, 17-21 June, 2002},
  title        = {Energy Transport, Overshoot, and Mixing in the Atmospheres of Very Cool Stars},
  volume       = {210},
  year         = {2003},
}