The Solar Tachocline: Limiting Magneto-Tipping Instabilities

Abstract

Two dimensional magneto-shear instabilities in the solar tachocline have been extensively explored in recent years. One of their most notable traits over a wide range of shear and magnetic profiles is a propensity for the magnetic field to tip substantially from its initial axisymmetric configuration, with possible implications for patterns of flux emergence. However, it is found that modifications of the standard models to include either kinetic and magnetic drag, or prograde toroidal velocity jets associated with magnetic bands, can suppress the instabilities, or considerably reduce their nonlinear development. In the case of tip reduction by jets, for a toroidal field of around 100kG in the tachocline (required for sunspots to emerge in sunspot latitudes), simulations indicate that jets capable of reducing tipping below the limits of detection from sunspot patterns at the surface are potentially detectable by helioseismic methods, and should be looked for. Establishing an upper limit to the jet may result in a lower limit for the amount of tipping to be expected.