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Title: Baroclinic instability in stellar radiation zones

Abstract

Surfaces of constant pressure and constant density do not coincide in differentially rotating stars. Stellar radiation zones with baroclinic stratification can be unstable. Instabilities in radiation zones are of crucial importance for angular momentum transport, mixing of chemical species, and, possibly, for magnetic field generation. This paper performs linear analysis of baroclinic instability in differentially rotating stars. Linear stability equations are formulated for differential rotation of arbitrary shape and then solved numerically for rotation nonuniform in radius. As the differential rotation increases, r- and g-modes of initially stable global oscillations transform smoothly into growing modes of baroclinic instability. The instability can therefore be interpreted as stability loss to r- and g-modes excitation. Regions of stellar parameters where r- or g-modes are preferentially excited are defined. Baroclinic instability onsets at a very small differential rotation of below 1%. The characteristic time of instability growth is about 1000 rotation periods. Growing disturbances possess kinetic helicity. Magnetic field generation by the turbulence resulting from baroclinic instability in differentially rotating radiation zones is therefore possible.

Authors:
 [1];  [2]
  1. Institute for Solar-Terrestrial Physics, Lermontov Str. 126A, Irkutsk 664033 (Russian Federation)
  2. (Russian Federation)
Publication Date:
OSTI Identifier:
22351464
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 784; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ANGULAR MOMENTUM; DENSITY; DISTURBANCES; GROWTH; HELICITY; HYDRODYNAMICS; INSTABILITY; MAGNETIC FIELDS; MIXING; OSCILLATIONS; ROTATION; STABILITY; STARS; STELLAR RADIATION; STRATIFICATION; SURFACES; TURBULENCE

Citation Formats

Kitchatinov, L. L., E-mail: kit@iszf.irk.ru, and Pulkovo Astronomical Observatory, St. Petersburg 176140. Baroclinic instability in stellar radiation zones. United States: N. p., 2014. Web. doi:10.1088/0004-637X/784/1/81.
Kitchatinov, L. L., E-mail: kit@iszf.irk.ru, & Pulkovo Astronomical Observatory, St. Petersburg 176140. Baroclinic instability in stellar radiation zones. United States. https://doi.org/10.1088/0004-637X/784/1/81
Kitchatinov, L. L., E-mail: kit@iszf.irk.ru, and Pulkovo Astronomical Observatory, St. Petersburg 176140. 2014. "Baroclinic instability in stellar radiation zones". United States. https://doi.org/10.1088/0004-637X/784/1/81.
@article{osti_22351464,
title = {Baroclinic instability in stellar radiation zones},
author = {Kitchatinov, L. L., E-mail: kit@iszf.irk.ru and Pulkovo Astronomical Observatory, St. Petersburg 176140},
abstractNote = {Surfaces of constant pressure and constant density do not coincide in differentially rotating stars. Stellar radiation zones with baroclinic stratification can be unstable. Instabilities in radiation zones are of crucial importance for angular momentum transport, mixing of chemical species, and, possibly, for magnetic field generation. This paper performs linear analysis of baroclinic instability in differentially rotating stars. Linear stability equations are formulated for differential rotation of arbitrary shape and then solved numerically for rotation nonuniform in radius. As the differential rotation increases, r- and g-modes of initially stable global oscillations transform smoothly into growing modes of baroclinic instability. The instability can therefore be interpreted as stability loss to r- and g-modes excitation. Regions of stellar parameters where r- or g-modes are preferentially excited are defined. Baroclinic instability onsets at a very small differential rotation of below 1%. The characteristic time of instability growth is about 1000 rotation periods. Growing disturbances possess kinetic helicity. Magnetic field generation by the turbulence resulting from baroclinic instability in differentially rotating radiation zones is therefore possible.},
doi = {10.1088/0004-637X/784/1/81},
url = {https://www.osti.gov/biblio/22351464}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 784,
place = {United States},
year = {Thu Mar 20 00:00:00 EDT 2014},
month = {Thu Mar 20 00:00:00 EDT 2014}
}