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Title: VOYAGER 1 NEAR THE HELIOPAUSE

Recent observations from the Voyager 1 spacecraft show that it is sampling the local interstellar medium (LISM). This is quite surprising because no realistic, steady-state model of the solar wind (SW) interaction with the LISM gives an inner heliosheath width as narrow as ∼30 AU. This includes models that assume a strong redistribution of the ion energy to the tails in the pickup ion distribution function. We show that the heliopause (HP), which separates the SW from the LISM, is not a smooth tangential discontinuity, but rather a surface subject to Rayleigh-Taylor-type instabilities which can result in LISM material penetration deep inside the SW. We also show that the HP flanks are always subject to a Kelvin-Helmholtz instability. The instabilities are considerably suppressed near the HP nose by the heliospheric magnetic field in steady-state models, but reveal themselves in the presence of solar cycle effects. We argue that Voyager 1 may be in one such instability region and is therefore observing plasma densities much higher than those in the pristine SW. These results may explain the early penetration of Voyager 1 into the LISM. They also show that there is a possibility that the spacecraft may start sampling the SW againmore » before it finally leaves the heliosphere.« less
Authors:
;  [1]
  1. Center for Space Physics and Aeronomic Research, The University of Alabama in Huntsville, Huntsville, AL 35805 (United States)
Publication Date:
OSTI Identifier:
22363945
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 783; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; DISTRIBUTION FUNCTIONS; HELIOSPHERE; HELMHOLTZ INSTABILITY; MAGNETIC FIELDS; PLASMA DENSITY; RAYLEIGH-TAYLOR INSTABILITY; SOLAR CYCLE; SOLAR WIND; STEADY-STATE CONDITIONS; SUN; VOYAGER SPACE PROBES