Research Commons
      • Browse 
        • Communities & Collections
        • Titles
        • Authors
        • By Issue Date
        • Subjects
        • Types
        • Series
      • Help 
        • About
        • Collection Policy
        • OA Mandate Guidelines
        • Guidelines FAQ
        • Contact Us
      • My Account 
        • Sign In
        • Register
      View Item 
      •   Research Commons
      • University of Waikato Research
      • Computing and Mathematical Sciences
      • Computing and Mathematical Sciences Papers
      • View Item
      •   Research Commons
      • University of Waikato Research
      • Computing and Mathematical Sciences
      • Computing and Mathematical Sciences Papers
      • View Item
      JavaScript is disabled for your browser. Some features of this site may not work without it.

      Slowdown and heating of interstellar neutral helium by elastic collisions beyond the heliopause

      Swaczyna, P.; Rahmanifard, F.; Zirnstein, E. J.; McComas, David J.; Heerikhuisen, J.
      Thumbnail
      Files
      2104.08345v1.pdf
      Accepted version, 1.239Mb
      DOI
       10.3847/2041-8213/abf436
      Find in your library  
      Citation
      Export citation
      Swaczyna, P., Rahmanifard, F., Zirnstein, E. J., McComas, D. J., & Heerikhuisen, J. (2021). Slowdown and heating of interstellar neutral helium by elastic collisions beyond the heliopause. Astrophysical Journal Letters, 911(2), L36–L36. https://doi.org/10.3847/2041-8213/abf436
      Permanent Research Commons link: https://hdl.handle.net/10289/14279
      Abstract
      Direct sampling of interstellar neutral (ISN) atoms close to the Sun enables studies of the very local interstellar medium (VLISM) around the heliosphere. The primary population of ISN helium atoms has, until now, been assumed to reflect the pristine VLISM conditions at the heliopause. Consequently, the atoms observed at 1 au by the Interstellar Boundary Explorer (IBEX) were used to determine the VLISM temperature and velocity relative to the Sun, without accounting for elastic collisions with other species outside the heliopause. Here, we evaluate the effect of these collisions on the primary ISN helium population. We follow trajectories of helium atoms and track their collisions with slowed plasma and interstellar hydrogen atoms ahead of the heliopause. Atoms typically collide a few times in the outer heliosheath, and only ~1.5% of the atoms are not scattered at all. We use calculated differential cross sections to randomly choose scattering angles in these collisions. We estimate that the resulting primary ISN helium atoms at the heliopause are slowed down by ~0.45 km/s⁻¹ and heated by ~1100 K compared to the pristine VLISM. The resulting velocity distribution is asymmetric and shows an extended tail in the antisunward direction. Accounting for this change in the parameters derived from IBEX observations gives the Sun's relative speed of 25.85 km/s⁻¹ and temperature of 6400 K in the pristine VLISM. Finally, this paper serves as a source of the differential cross sections for elastic collisions with helium atoms.
      Date
      2021
      Type
      Journal Article
      Publisher
      IOP Publishing
      Rights
      This is an author’s accepted version of an article published in the journal: Astrophysical Journal Letters. © 2021. The American Astronomical Society.
      Collections
      • Computing and Mathematical Sciences Papers [1457]
      Show full item record  

      Usage

      Downloads, last 12 months
      48
       
       
       

      Usage Statistics

      For this itemFor all of Research Commons

      The University of Waikato - Te Whare Wānanga o WaikatoFeedback and RequestsCopyright and Legal Statement