Bound current (${\mathbf{J}}_b={\partial }_t\mathbf{P}+\nabla \times \mathbf{M}$)

The current associated with electric polarization and magnetization in matter. If the magnetic response is neglected, it is ${\mathbf{J}}_b={\partial }_t\mathbf{P}$. It is distinguished from a free conduction current in the Maxwell equations in matter.