Voyager observations of the magnetic field, interstellar pickup ions and solar wind in the distant heliosphere

L. F. Burlaga, N. F. Ness, J. W. Belcher, A. J. Lazarus, and J. D. Richardson

Laboratory for Extraterrestrial Physics, NASA-Goddard Space Flight Center, Greenbelt, MD 20771 

Abstract: 

Voyagers 1 and 2 are now observing the latitudinal structure of the heliospheric magnetic field in the distant heliosphere (the region between » 30 AU and the termination shock). Voyager 2 is observing the influence of the interstellar medium on the solar wind. The pressure of the interstellar pickup protons, measured by their contribution to pressure balanced structures, is greater than or equal to the magnetic pressure and much greater than the thermal pressure of the solar wind in the distant heliosphere. The solar wind speed decreases and its proton temperature increases with increasing distance from the sun. This may result from the production of pickup ions by the charge exchange process with the interstellar neutrals. The introduction of the pickup ions into the dynamics of the magnetized solar wind plasma appears to be an important new process which must be considered in future theoretical studies of the termination shock and boundary with the local interstellar medium.

Space Sci. Rev., 78, 33-42, 1996