  The effects of uniform horizontal shear on a stably stratified layer of gas
is studied. The system is initially destabilized by a magnetically buoyant flux
tube pointing in the cross-stream direction. The shear amplifies the initial
field to Lundquist numbers of about 200-400, but then its value drops to about
100-300, depending on the value of the sub-adiabatic gradient. The larger
values correspond to cases where the stratification is strongly stable and
nearly isothermal. At the end of the runs the magnetic field is nearly
axisymmetric, i.e. uniform in the streamwise direction. In view of Cowling's
theorem the sustainment of the field remains a puzzle and may be due to subtle
numerical effects that have not yet been identified in detail. In the final
state the strength of the magnetic field decreases with height in such a way
that the field is expected to be unstable. Low amplitude oscillations are seen
in the vertical velocity even at late times, suggesting that they might be
persistent.

Solar and Stellar Astrophysics