Rayleigh-Taylor instabilities with sheared magnetic fields

Abstract

Magnetic Rayleigh-Taylor (MRT) instabilities may play a relevant role in many astrophysical problems. In this work the effect of magnetic shear on the growth rate of the MRT instability is investigated. The eigenmodes of an interface and a slab model under the presence of gravity are analytically calculated assuming that the orientation of the magnetic field changes in the equilibrium, i.e., there is magnetic shear. We solve the linearised magnetohydrodynamic (MHD) equations in the incompressible regime.We find that the growth rate is bounded under the presence of magnetic shear. We have derived simple analytical expressions for the maximum growth rate, corresponding to the most unstable mode of the system. These expressions provide the explicit dependence of the growth rate on the various equilibrium parameters. For small angles the growth time is linearly proportional to the shear angle, and in this regime the single interface problem and the slab problem tend to the same result. On the contrary, in the limit of large angles and for the interface problem the growth time is essentially independent of the shear angle. In this regime we have also been able to calculate an approximate expression for the growth time for the slab configuration. Magnetic shear can have a strong effect on the growth rates of the instability. As an application of the results found in this paper we have indirectly determined the shear angle in solar prominence threads using their lifetimes and the estimation of the Alfvén speed of the structure.

References in corpus (3)

• The Magnetic Rayleigh-Taylor Instability in Three Dimensions
• Transverse oscillations of flowing prominence threads observed with Hinode
• The discovery of geomagnetically trapped cosmic ray antiprotons

Cited by in corpus (12)

• Morphology and dynamics of solar prominences from 3D MHD simulations
• Quiescent prominence dynamics observed with the Hinode Solar Optical Telescope . II. Prominence Bubble Boundary Layer Characteristics and the Onset of a Coupled Kelvin-Helmholtz Rayleigh-Taylor Instability
• Solar prominences: 'double, double ... boil and bubble'
• On the nature of the magnetic Rayleigh-Taylor instability in Astrophysical Plasma: The case of uniform magnetic field strength
• Solar prominences embedded in flux ropes: morphological features and dynamics from 3D MHD simulations
• Two-fluid simulations of Rayleigh-Taylor instability in a magnetized solar prominence thread. I. Effects of prominence magnetization and mass loading
• Particle acceleration by magnetic Rayleigh-Taylor instability: mechanism for flares in black-hole accretion flows
• The Evolution of Magnetic Rayleigh-Taylor Unstable Plumes and Hybrid KH-RT Instability into A Loop-like Eruptive Prominence
• Magneto-Rayleigh-Taylor instability driven by a rotating magnetic field
• Simulating Rayleigh-Taylor induced magnetohydrodynamic turbulence in prominences
• Magnetic Rayleigh-Taylor Instability at a Contact Discontinuity With Oblique Magnetic Field
• Scaling of Small-Scale Dynamo Properties in the Rayleigh-Taylor Instability