New Type of Magnetorotational Instability in Cylindrical Taylor-Couette Flow

Abstract

We study the stability of cylindrical Taylor-Couette flow in the presence of combined axial and azimuthal magnetic fields, and show that adding an azimuthal field profoundly alters the previous results for purely axial fields. For small magnetic Prandtl numbers Pm, the critical Reynolds number ${\mathrm{Re}}_c$ for the onset of the magnetorotational instability becomes independent of Pm, whereas for purely axial fields it scales as ${\mathrm{Pm}}^{-1}$. For typical liquid metals, ${\mathrm{Re}}_c$ is then reduced by several orders of magnitude, enough that this new design should succeed in realizing this instability in the laboratory.