Amplification and stability of magnetic fields and dynamo effect in young A stars

This study is concerned with the early evolution of magnetic fields and differential rotation of intermediate-mass stars which may evolve into Ap stars. We report on simulations of the interplay of differential rotation and magnetic fields, the stability limits and non-linear evolution of such configurations, and the prospects of dynamo action from the unstable cases. The axisymmetric problem delivers a balance between field amplification and back-reaction of the magnetic field on the differential rotation. The non-axisymmetric case involves also the Tayler instability of the amplified toroidal fields. We consider limits for field amplification and apply these to young A stars.