Overstability of acoustic waves in strongly magnetized anisotropic magnetohydrodynamic shear flows
- Abastumani Astrophysical Observatory, Ilia State University, Tbilisi, Georgia (United States)
- Institut für Theoretische Physik IV: Weltraum- und Astrophysik, Ruhr-Universitat Bochum, 44780 Bochum (Germany)
- Faculty of Exact and Natural Sciences, Javakhishvili Tbilisi State University, 3 Chavchavadze Ave., Tbilisi 0179, Georgia (United States)
- Centre for Mathematical Plasma Astrophysics, Department of Mathematics, KU Leuven, Celestijnenlaan 200B, 3001 Leuven (Belgium)
We present a linear stability analysis of the perturbation modes in anisotropic magnetohydrodynamic (MHD) flows with velocity shear and strong magnetic field. Collisionless or weakly collisional plasma is described within the 16-momentum MHD fluid closure model that takes into account not only the effect of pressure anisotropy but also the effect of anisotropic heat fluxes. In this model, the low frequency acoustic wave is revealed into a standard acoustic mode and higher frequency fast thermo-acoustic and lower frequency slow thermo-acoustic waves. It is shown that thermo-acoustic waves become unstable and grow exponentially when the heat flux parameter exceeds some critical value. It seems that velocity shear makes thermo-acoustic waves overstable even at subcritical heat flux parameters. Thus, when the effect of heat fluxes is not profound acoustic waves will grow due to the velocity shear, while at supercritical heat fluxes the flow reveals compressible thermal instability. Anisotropic thermal instability should be also important in astrophysical environments, where it will limit the maximal value of magnetic field that a low density ionized anisotropic flow can sustain.
- OSTI ID:
- 22303787
- Journal Information:
- Physics of Plasmas, Vol. 21, Issue 8; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
Similar Records
Convective overstability in radially stratified accretion disks under thermal relaxation
Anisotropic MHD model and some solutions