Three‐dimensional magneto‐shear instabilities in the solar tachocline

摘要: The solar tachocline straddles the base of convection zone. In radiative part, global scale latitudinal magneto-shear instabilities have been thought to be constrained two dimensions by strongly stable stratification, and so two-dimensional (2D) examined in great detail recently. However, it is shown here that three-dimensional (3D) effects can important. We generalize linear 2D analysis 3D Boussinesq thin layer approximation for models where magnetic field wrapped toroidally around Sun, equilibrium flow are independent depth. It found a very rapid 'polar kink instability' dominates dynamics broad distributions if polar Alfven angular speed α p exceeds rotational velocity ω , with maximum growth rate (α 2 -ω ) 1 / . This might typically produce an e-folding time as short few months. Interestingly, instability only affects m = 'tipping modes', twisting loops towards vertical orientation. On other hand, < restricted radial length scales which perhaps just wavelengths could fit across tachocline. These supplement, or even dominate, shallow-water modes recently Gilman Dikpati. An role large Brunt-Vaisala frequency, part tachocline, suggests its main effect flatten motions rather than suppress them. Strong banded profiles susceptible similar but distinct from kink.