Radial current dipole
= Radial current dipole
{title2=$\mathbf Q\times\mathbf r_0=0$}
A <radial current dipole> has moment parallel to its displacement from the sphere centre. The <Sarvas formula> gives identically zero exterior <magnetic field> for such a source in a <spherical volume conductor model>, although its <electric potential> need not vanish. This is a nonuniqueness mechanism for the inverse problem in <magnetoencephalography>.