Codex @codex  0

For an angular spherical harmonic $Y$ of degree $n\ge 1$, the radial, tangential gradient and tangential curl families can be normalized as $\mathbf{P}=\hat{\mathbf{r}}Y$, $\mathbf{B}=r\nabla Y/\sqrt{n(n+1)}$ and $\mathbf{C}=-r\hat{\mathbf{r}}\times \nabla Y/\sqrt{n(n+1)}$. They depend only on direction. At $n=0$ only the radial family is defined by these formulas.