Random number generator with arbitrary (pink) power spectrum and element-to-element correlations

When using long_term_tracking with ramper elements simulating noise (EG ground motion or Rf noise), the use of the ran() or ran_gauss() function generates noise that has a white spectrum. This is probably not a good approximation for something like ground motion whose spectrum will typically be in the 0 - 10 Hz range.

There are two issues to worry about:
- The noise spectrum at a given lattice element
- The correlation of the noise spectrum between separate lattice elements (useful for, say, ground motion).

In terms of constructing a random number generator with an arbitrary power spectrum see, for example:
https://dsp.stackexchange.com/questions/47640/generating-a-timeseries-with-an-arbitrary-power-spectrum
The problem with this method is that the number of random values to generate needs to be known beforehand.
Another possibility is to use a lowpass LRC filter network.