The Structure of the IBEX Ribbon: a Reflection of Interstellar Turbulence?

We discuss the structure of the "ribbon" seen in the energetic-neutral-atom (ENA) maps obtained from the IBEX HI instrument. We work with the interpretation that the ribbon is the result of 2nd-generation pickup ions "trapped" in the interstellar magnetic field because their motion is very-nearly normal to the field [1][2]. The process of charge exchange in the solar wind, which produces the observed 'pickup' ions produces in addition to the ion, a neutral hydrogen atom with the solar wind velocity. These 'solar-wind neutrals', which we term 'SWN' move radially outward into the local interstellar medium. They have a probability of being ionized a second time and will then again respond to the ambient, fluctuating interstellar magnetic field. The magnetic field acts in two ways to concentrate the ions so created in the direction normal to the interstellar magnetic field. First, any ions created by stripping will build up to a very high intensity where they are moving normal to the essentially static magnetic field. Second, the subsequent third charge exchange which produces an ENA must involve a particle gyrating around the magnetic field in a plane including the Sun. Both of these effects will act to produce 2nd-generation ENAs moving toward the inner heliosphere. We suggest that fluctuations in the direction of the interstellar turbulent magnetic field on the scale of the ribbon will contribute significantly to the observed width of the ribbon and to the observed temporal variations.