Multicomponent theory of buoyancy instabilities in astrophysical plasma objects: The case of magnetic field perpendicular to gravity

Abstract

We develop a general theory of buoyancy instabilities in the electron-ion plasma with the electron heat flux based not upon MHD equations, but using a multicomponent plasma approach in which the momentum equation is solved for each species. We investigate the geometry in which the background magnetic field is perpendicular to the gravity and stratification. General expressions for the perturbed velocities are given without any simplifications. Collisions between electrons and ions are taken into account in the momentum equations in a general form, permitting us to consider both weakly and strongly collisional objects. However, the electron heat flux is assumed to be directed along the magnetic field that implies a weakly collisional case. Using simplifications justified for an investigation of buoyancy instabilities with the electron thermal flux, we derive simple dispersion relations both for collisionless and collisional cases for arbitrary directions of the wave vector. The collisionless dispersion relation considerably differs from that obtained in the MHD framework and is similar to the Schwarzschild's criterion. This difference is connected with simplified assumptions used in the MHD analysis of buoyancy instabilities and with the role of the longitudinal electric field perturbation which is not captured by the ideal MHD equations. The results obtained can be applied to clusters of galaxies and other astrophysical objects.

Accepted for publication in "Astrophysical Journal"

References in corpus (10)

• Buoyancy Instabilities in Weakly Magnetized Low Collisionality Plasmas
• AGN self-regulation in cooling flow clusters
• Nonlinear growth of firehose and mirror fluctuations in turbulent galaxy-cluster plasmas
• Deep high-resolution X-ray spectra from cool-core clusters
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• Compressible streaming instabilities in rotating thermal viscous objects
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• Electromagnetic instabilities in rotating magnetized viscous objects

Cited by in corpus (5)

• Electromagnetic thermal instability with momentum and energy exchange between electrons and ions in galaxy clusters
• Multicomponent theory of buoyancy instabilities in magnetized plasmas: The case of magnetic field parallel to gravity
• Streaming cold cosmic ray back-reaction and thermal instabilities across the background magnetic field
• Influence of energy exchange of electrons and ions on the long-wavelength thermal instability in magnetized astrophysical objects
• Back-reaction instabilities of relativistic cosmic rays