  The narrow ribbon of enhanced energetic neutral atom flux observed by the
Interstellar Boundary Explorer (IBEX) spacecraft has prompted numerous ideas to
explain its structure and properties. One of these ideas is the "neutral solar
wind" scenario, which identifies the source particles as pickup protons in the
local interstellar medium originating in solar wind charge-exchange
interactions. This scenario has been thought to require unrealistically weak
pitch-angle scattering of the pickup protons to explain the narrow structure.
Recently, Schwadron & McComas (2013) suggested that this structure could result
from a spatial retention of the pickup protons, rather than from a restricted
pitch-angle distribution. Here, we present a physically motivated, quantitative
mechanism to produce such a spatial configuration. This mechanism is based on
the "dominant turbulence" assumption, which can be applied where the production
of new pickup protons is slow, and has been used to successfully explain the
level of turbulent heating observed in the outer solar wind. This formalism
predicts a pickup isotropization process which adds or subtracts energy from
the ambient turbulent fluctuations, depending on the initial pitch angle of the
pickup protons. We show that a simple model of this process can yield a ribbon
structure in qualitative agreement with the observations. The results of this
simple model are not yet quantitatively satisfactory, but we suggest several
improvements which may reduce the quantitative discrepancy.
