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The properties of g-modes in layered semiconvection

Belyaev, Mikhail A. and Quataert, Eliot and Fuller, Jim (2015) The properties of g-modes in layered semiconvection. Monthly Notices of the Royal Astronomical Society, 452 (3). pp. 2700-2711. ISSN 0035-8711. http://resolver.caltech.edu/CaltechAUTHORS:20151002-105914336

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Abstract

We study low-frequency waves that propagate in a region of layered semiconvection. Layered semiconvection is predicted to be present in stellar and planetary interiors and can significantly modify the rate of thermal and compositional mixing. We derive a series of analytical dispersion relations for plane-parallel layered semiconvection in the Boussinesq approximation using a matrix transfer formalism. We find that like a continuously stratified medium, a semiconvective staircase – in which small convective regions are separated by sharp density jumps – supports internal gravity waves (g-modes). When the wavelength is much longer than the distance between semiconvective steps, these behave nearly like g-modes in a continuously stratified medium. However, the g-mode period spacing in a semiconvective region is systematically smaller than in a continuously stratified medium, and it decreases with decreasing mode frequency. When the g-mode wavelength becomes comparable to the distance between semiconvective steps, the g-mode frequencies deviate significantly from those of a continuously stratified medium (the frequencies are higher). g-modes with vertical wavelengths smaller than the distance between semiconvective steps are evanescent and do not propagate in the staircase. Thus, there is a lower cut-off frequency for a given horizontal wavenumber. We generalize our results to gravitoinertial waves relevant for rapidly rotating stars and planets. Finally, we assess the prospects for detecting layered semiconvection using astero/planetary seismology.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1093/mnras/stv1446DOIArticle
http://mnras.oxfordjournals.org/content/452/3/2700PublisherArticle
http://arxiv.org/abs/1505.05492arXivDiscussion Paper
ORCID:
AuthorORCID
Quataert, Eliot0000-0001-9185-5044
Fuller, Jim0000-0002-4544-0750
Additional Information:© 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2015 June 26. Received 2015 June 26. In original form 2015 May 20. First published online July 25, 2015. We thank Pascale Garaud for fruitful discussions on stellar and planetary oscillations and semiconvection. This work was supported in part by the Theoretical Astrophysics Center at UCB, by a Simons Investigator award from the Simons Foundation to EQ, and by the David and Lucile Packard Foundation. JF acknowledges partial support from NSF under grant no. AST-1205732 and through a Lee DuBridge Fellowship at Caltech.
Group:TAPIR
Funders:
Funding AgencyGrant Number
University of California Center of Theoretical AstrophysicsUNSPECIFIED
Simons FoundationUNSPECIFIED
David and Lucile Packard FoundationUNSPECIFIED
NSFAST-1205732
Lee A. DuBridge FoundationUNSPECIFIED
Subject Keywords:convection; hydrodynamics; stars: oscillations
Record Number:CaltechAUTHORS:20151002-105914336
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20151002-105914336
Official Citation:Mikhail A. Belyaev, Eliot Quataert, and Jim Fuller The properties of g-modes in layered semiconvection MNRAS (September 21, 2015) Vol. 452 2700-2711 doi:10.1093/mnras/stv1446 First published online July 25, 2015
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:60702
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:02 Oct 2015 20:06
Last Modified:13 Sep 2017 15:49

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