docs: def calc_freefree_snu_ujy(ne, t, width, elongation, dist, ghz):
      """Calculate a flux density from pure free-free emission.
  
      """
      hz = ghz * 1e9
      eta = calc_freefree_eta(ne, t, hz)
      kappa = calc_freefree_kappa(ne, t, hz)
      snu = calc_snu(eta, kappa, width, elongation, dist)
      ujy = snu * cgs.jypercgs * 1e6
      return ujy