anelastic
---------

Solves the anelastic hydro/MHD equations by solving for the Poisson
equation for pressure by talking the divergence of the momentum equation.
No assumption about a background state us needed.

Major parts were written by Piyali Chatterjee in 2010, but it wasn't
completed and this part is not in use.

There is a sample in:
  ~/pencil-code/samples/2d-tests/anelastic_decay/

Documentation can be found under:
  [anelastic_hurdle.pdf][anelastic_hurdle]

[anelastic_hurdle]: anelastic_hurdle.pdf