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Title: ENERGETIC PARTICLE ANISOTROPIES AT THE HELIOSPHERIC BOUNDARY

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.
Authors:
;  [1] ;  [2] ;  [3]
  1. Department of Space Sciences, University of Alabama in Huntsville, Huntsville, AL 35899 (United States)
  2. Department of Planetary Sciences and Lunar and Planetary Lab, University of Arizona, Tucson, AZ 85721 (United States)
  3. Center for Space Plasma and Aeronomic Research, University of Alabama in Huntsville, Huntsville, AL 35899 (United States)
Publication Date:
OSTI Identifier:
22215431
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 776; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ANISOTROPY; CLOUDS; COSMIC RADIATION; DISTRIBUTION; FLUCTUATIONS; INCLINATION; INTERSTELLAR SPACE; MAGNETIC FIELDS; SOLAR WIND; TAIL IONS; VOYAGER SPACE PROBES