Sorry, I do think some clarification is needed since you are right that `rootps` actually means `sqrt(ps)` i.e. the root comes from square-root rather than root as in somehow denoting the origin or parent.  I only ever cache-stored rootps in the previous incarnation since it is actually the square root of the power spectrum that you need to generate a correlated random noise field using discrete Fourier transforms.

This means that the interpretation of the maths is a bit different too.  Like variances or covariances Power spectra simply add, so the square on rootps is really making it a power spectrum.  Then I simply add an all-positive power spectrum to it that results in a flat power-spectrum in the end.  I'll add more about this!!