Mass current
= Mass current
{title2=$\mathbf j_m=\rho\mathbf v$}
The flux of <mass> carried by a continuum moving with <velocity> $\mathbf v$. In the nonrelativistic limit, $\partial_t\rho+\nabla\cdot\mathbf j_m=0$ is local <mass conservation>. A stationary mass current can produce a stationary gravitomagnetic field without emitting <gravitational radiation>.