Convective, absolute and global azimuthal magnetorotational instabilities

Abstract

We study the convective and absolute forms of azimuthal magnetorotational instability (AMRI) in a Taylor-Couette (TC) flow with an imposed azimuthal magnetic field. We show that the domain of the convective AMRI is wider than that of the absolute AMRI. Actually, it is the absolute instability which is the most relevant and important for magnetic TC flow experiments. The absolute AMRI, unlike the convective one, stays in the device, displaying a sustained growth that can be experimentally detected. We also study the global AMRI in a TC flow of finite height using DNS and find that its emerging butterfly-type structure -- a spatio-temporal variation in the form of upward and downward traveling waves -- is in a very good agreement with the linear stability analysis, which indicates the presence of two dominant absolute AMRI modes in the flow giving rise to this global butterfly pattern.

11 pages, 6 figures, accepted for publication in J. Fluid Mech. Rapids

References in corpus (6)

• Experimental observation and characterization of the magnetorotational instability
• Experimental evidence for magnetorotational instability in a helical magnetic field
• Helical Magnetorotational Instability in Magnetized Taylor-Couette Flow
• Magnetohydrodynamic experiments on cosmic magnetic fields
• Observation of magnetocoriolis waves in a liquid metal Taylor-Couette experiment
• Absolute versus convective helical magnetorotational instability in a Taylor-Couette flow