Solid harmonic
= Solid harmonic
{title2=$r^nY_{nm},\quad r^{-n-1}Y_{nm}$}
{wiki}
A <solid harmonic> extends a <spherical harmonic> to a <harmonic function> in space with either the regular radial power $r^n$ or the irregular radial power $r^{-n-1}$. In three dimensions these are the two separated radial solutions of the <Laplace equation> at angular degree $n$.