Journal Article

Buoyancy instabilities in degenerate, collisional, magnetized plasmas

Philip Chang and Eliot Quataert

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 403, issue 1, pages 246-252
Published in print March 2010 | ISSN: 0035-8711
Published online March 2010 | e-ISSN: 1365-2966 | DOI:
Buoyancy instabilities in degenerate, collisional, magnetized plasmas

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In low-collisionality plasmas, anisotropic heat conduction due to a magnetic field leads to buoyancy instabilities for any non-zero temperature gradient. We study analogous instabilities in degenerate collisional plasmas, i.e. when the electron collision frequency is large compared to the electron cyclotron frequency. Although heat conduction is nearly isotropic in this limit, the small residual anisotropy ensures that collisional degenerate plasmas are also convectively unstable independent of the sign of the temperature gradient. We show that the range of wavelengths that are unstable is independent of the magnetic field strength, while the growth time increases with decreasing magnetic field strength. We discuss the application of these collisional buoyancy instabilities to white dwarfs and neutron stars. Magnetic tension and the low specific heat of a degenerate plasma significantly limit their effectiveness; the most promising venues for growth are in the liquid oceans of young, weakly magnetized neutron stars (B≲ 109 G) and in the cores of young, high magnetic field white dwarfs (B∼ 109 G).

Keywords: convection; instabilities; plasmas; stars: neutron; white dwarfs

Journal Article.  5331 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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