  We explore the flux front patterns during virgin penetration and after
remagnetization in the iron-based superconductor Ba(Fe_{1-x}Co_{x})_{2}As_{2}.
After remagnetization we observe an instability characterized by turbulent
dynamics at the vortex-antivortex boundary. Associated with the turbulent flux
boundary a band of excess current density is observed. The turbulence is
contrasted with the instability observed in the cuprate superconductors. Our
results suggest turbulent instability at the vortex-antivortex interface may be
a common feature in all remagnetized type-II superconductors.

Superconductivity