Transverse streaming anisotropies of charged particles accelerated at the solar wind termination shock

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Abstract

We address the anisotropy, transverse to the heliographic radial direction, of energetic charged particles accelerated at the termination shock of the solar wind. We consider the transport of energetic charged particles both in the diffusion approximation and by directly integrating test particle trajectories in a turbulent magnetic field. We find that the nature and directions of the transverse anisotropies observed on Voyager 1 can be interpreted in terms of existing models of the heliosphere, if Voyager 1 were still upstream of the termination shock. In particular, the observations are consistent with recent models in which either the upstream heliospheric termination shock flares out from the nose of the heliosphere, so that its heliocentric radius increases away from the nose, or the heliosphere is offset from the direction of the incoming neutral wind, or both. In these pictures a Parker spiral magnetic field line from the Sun intersects the termination shock many times, not just once, and the closest intersection to Voyager 1 is on the direction along the field that leads back to the Sun, as is observed. We suggest that the recent Voyager 1 observations of energetic particle anisotropies, both radial and transverse, are expected in a scenario in which Voyager 1 did not cross the termination shock.

Original languageEnglish (US)
JournalAstrophysical Journal
Volume611
Issue number2 II
DOIs
StatePublished - Aug 20 2004

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solar wind
charged particles
anisotropy
shock
heliosphere
energetic particles
energetics
upstream
magnetic field
sun
particle trajectories
magnetic fields
intersections
trajectory
flares
particle
radii
approximation

Keywords

  • Acceleration of particles
  • Interplanetary medium
  • Shock waves

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

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title = "Transverse streaming anisotropies of charged particles accelerated at the solar wind termination shock",
abstract = "We address the anisotropy, transverse to the heliographic radial direction, of energetic charged particles accelerated at the termination shock of the solar wind. We consider the transport of energetic charged particles both in the diffusion approximation and by directly integrating test particle trajectories in a turbulent magnetic field. We find that the nature and directions of the transverse anisotropies observed on Voyager 1 can be interpreted in terms of existing models of the heliosphere, if Voyager 1 were still upstream of the termination shock. In particular, the observations are consistent with recent models in which either the upstream heliospheric termination shock flares out from the nose of the heliosphere, so that its heliocentric radius increases away from the nose, or the heliosphere is offset from the direction of the incoming neutral wind, or both. In these pictures a Parker spiral magnetic field line from the Sun intersects the termination shock many times, not just once, and the closest intersection to Voyager 1 is on the direction along the field that leads back to the Sun, as is observed. We suggest that the recent Voyager 1 observations of energetic particle anisotropies, both radial and transverse, are expected in a scenario in which Voyager 1 did not cross the termination shock.",
keywords = "Acceleration of particles, Interplanetary medium, Shock waves",
author = "Jokipii, {J. Randy} and Joe Giacalone and J. K{\'o}ta",
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T1 - Transverse streaming anisotropies of charged particles accelerated at the solar wind termination shock

AU - Jokipii, J. Randy

AU - Giacalone, Joe

AU - Kóta, J.

PY - 2004/8/20

Y1 - 2004/8/20

N2 - We address the anisotropy, transverse to the heliographic radial direction, of energetic charged particles accelerated at the termination shock of the solar wind. We consider the transport of energetic charged particles both in the diffusion approximation and by directly integrating test particle trajectories in a turbulent magnetic field. We find that the nature and directions of the transverse anisotropies observed on Voyager 1 can be interpreted in terms of existing models of the heliosphere, if Voyager 1 were still upstream of the termination shock. In particular, the observations are consistent with recent models in which either the upstream heliospheric termination shock flares out from the nose of the heliosphere, so that its heliocentric radius increases away from the nose, or the heliosphere is offset from the direction of the incoming neutral wind, or both. In these pictures a Parker spiral magnetic field line from the Sun intersects the termination shock many times, not just once, and the closest intersection to Voyager 1 is on the direction along the field that leads back to the Sun, as is observed. We suggest that the recent Voyager 1 observations of energetic particle anisotropies, both radial and transverse, are expected in a scenario in which Voyager 1 did not cross the termination shock.

AB - We address the anisotropy, transverse to the heliographic radial direction, of energetic charged particles accelerated at the termination shock of the solar wind. We consider the transport of energetic charged particles both in the diffusion approximation and by directly integrating test particle trajectories in a turbulent magnetic field. We find that the nature and directions of the transverse anisotropies observed on Voyager 1 can be interpreted in terms of existing models of the heliosphere, if Voyager 1 were still upstream of the termination shock. In particular, the observations are consistent with recent models in which either the upstream heliospheric termination shock flares out from the nose of the heliosphere, so that its heliocentric radius increases away from the nose, or the heliosphere is offset from the direction of the incoming neutral wind, or both. In these pictures a Parker spiral magnetic field line from the Sun intersects the termination shock many times, not just once, and the closest intersection to Voyager 1 is on the direction along the field that leads back to the Sun, as is observed. We suggest that the recent Voyager 1 observations of energetic particle anisotropies, both radial and transverse, are expected in a scenario in which Voyager 1 did not cross the termination shock.

KW - Acceleration of particles

KW - Interplanetary medium

KW - Shock waves

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