Energetic particle anisotropies at the heliospheric boundary

V. Florinski, J. R. Jokipii, F. Alouani-Bibi, J. A. Le Roux

Research output: Contribution to journalArticlepeer-review

28 Scopus citations


In 2012 August the Voyager 1 space probe entered a distinctly new region of space characterized by a virtual absence of heliospheric energetic ions and magnetic fluctuations, now interpreted as a part of the local interstellar cloud. Prior to their disappearance, the ion distributions strongly peaked at a 90° pitch angle, implying rapid escape of streaming particles along the magnetic field lines. Here we investigate the process of particle crossing from the heliosheath into the interstellar space, using a kinetic approach that resolves scales of the particle's cyclotron radius and smaller. It is demonstrated that a "pancake" pitch-angle distribution naturally arises at a tangential discontinuity separating a weakly turbulent plasma from a laminar region with a very low pitch-angle scattering rate. The relatively long persistence of gyrating ions is interpreted in terms of field line meandering facilitating their cross-field diffusion within the depletion region.

Original languageEnglish (US)
Article numberL37
JournalAstrophysical Journal Letters
Issue number2
StatePublished - Oct 20 2013
Externally publishedYes


  • cosmic rays
  • magnetic fields
  • solar wind
  • turbulence

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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