Voyager 1 exited the solar wind at a distance of ∼85 AU from the Sun

Document Type

Article

Publication Date

11-6-2003

Abstract

The outer limit of the Solar System is often considered to be at the distance from the Sun where the solar wind changes from supersonic to subsonic flow. Theory predicts that a termination shock marks this boundary, with locations ranging from a few to over 100 AU (1 AU ≈ 1.5 × 10 8 km, the distance from Earth to the Sun). 'Pick-up ions' that originate as interstellar neutral atoms should be accelerated to tens of MeV at the termination shock, generating anomalous cosmic rays. Here we report a large increase in the intensity of energetic particles in the outer heliosphere, as measured by an instrument on the Voyager 1 spacecraft. We argue that the spacecraft exited the supersonic solar wind and passed into the subsonic region (possibly beyond the termination shock) on about 1 August 2002 at a distance of ∼85 AU (heliolatitude ∼34° N), then re-entered the supersonic solar wind about 200 days later at ∼87 AU from the Sun. We show that the composition of the ions accelerated at the putative termination shock is that of anomalous cosmic rays and of interstellar pick-up ions.

Identifier

0242713051 (Scopus)

Publication Title

Nature

External Full Text Location

https://doi.org/10.1038/nature02068

ISSN

00280836

First Page

45

Last Page

48

Issue

6962

Volume

426

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