J. Giacalone, J. R. Jokipii

Research output: Contribution to journalArticlepeer-review

45 Scopus citations


We present a model for the narrow, ribbon-like enhancement in the emission of ∼keV energetic neutral atoms (ENA) coming from the outer heliosphere, coinciding roughly with the plane of the very local interstellar magnetic field (LISMF). We show that the pre-existing turbulent LISMF has sufficient amplitude in magnitude fluctuations to efficiently trap ions with initial pitch-angles near 90�, primarily by magnetic mirroring, leading to a narrow region of enhanced pickup-proton intensity. The pickup protons interact with cold interstellar hydrogen to produce ENAs seen at 1 AU. The computed width of the resulting ribbon of emission is consistent with observations. We also present results from a numerical model that are also generally consistent with the observations. Our interpretation relies only on the pre-existing turbulent interstellar magnetic field to trap the pickup protons. This leads to a broader local pitch-angle distribution compared to that of a ring. Our numerical model also predicts that the ribbon is double-peaked with a central depression. This is a further consequence of the (primarily) magnetic mirroring of pickup ions with pitch-angles close to 90� in the pre-existing, turbulent interstellar magnetic field.

Original languageEnglish (US)
Article numberL9
JournalAstrophysical Journal Letters
Issue number1
StatePublished - Oct 10 2015


  • ISM: kinematics and dynamics
  • ISM: magnetic fields
  • Sun: heliosphere
  • diffusion
  • turbulence

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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