DR. SHARANYA SUR

Turbulent motions are essential to the mixing of entrained fluids and are also capable of amplifying weak initial magnetic fields by dynamo action. In this talk, we consider the mixing of pollutants in the presence of an evolving magnetic field generated by dynamo action. We show that the scalar gradient field, which must be large for diffusion to operate effectively, is always strongly anti-aligned with the magnetic field. This is true both in the early kinematic phase, when the field is dynamically unimportant, and in the late, saturated phase, when magnetic back reactions become strong enough to influence the flow. At late times the saturated magnetic field is strong enough to resist compressive motions making it harder for scalar gradients to grow and likely leading to the longer mixing times. Since both mixing and magnetic field amplification are driven by turbulent motions, these results are likely to have a bearing on mixing in astrophysical systems.