  We revisit the question of how the unstable scattering of interstellar pickup
ions (PUIs) may drive turbulence in the outer solar wind, and why the energy
released into fluctuations by this scattering appears to be significantly less
than the standard bispherical prediction. We suggest that energization of the
newly picked-up ions by the ambient turbulence during the scattering process
can result in a more spherical distribution of PUIs, and reduce the generated
fluctuation energy to a level consistent with the observations of turbulent
intensities and core solar wind heating. This scenario implies the operation of
a self-regulation mechanism that maintains the observed conditions of
turbulence and heating in the PUI-dominated solar wind.
