# Finding a 'vector potential' such that $\mathbf E = \nabla\times \mathbf C$ for a point charge

Supposedly, "Any divergence-free vector field can be expressed as the curl of some other divergence-free vector field" over a simply-connected domain.

So, what is one such vector potential which works for half of the Coulomb field?

To be clear, I want a vector potential whose curl equals the vector field $\mathbf R/|\mathbf R|^3$ for $z>0$ (for any $x$ and any $y$). $\mathbf R$ is the position vector $(x,y,z)$.

I know the scalar potential method is usually used instead of this, but am curious about how ugly a vector potential would look. If this gets answered, it should then be easy to answer this.

• This is mathematically the same as the question of how magnetic monopoles are constructed. See, for example, this question and references therein. Jan 31, 2017 at 23:47
• I think I'm asking for something different since I only want the monopole effects over half of space...I could not find the math which answers my question in the references, so please point me directly if I missed it. Feb 1, 2017 at 0:09
• The initial title is somewhat misleading - it leads one to expect a standard vector potential. I've edited for clarity. Feb 2, 2017 at 1:28

In cylindrical coordinates, this potential (pointed angularly about the z-axis) works: $$\vec{C} = \frac{1-\frac{z}{\sqrt{r^2+z^2}}}{r} \hat{\phi}$$