Heating of the Solar Wind Beyond 1 AU by Turbulent Dissipation

C. W. Smith, G. P. Zank, W. H. Matthaeus and S. Oughton

Proceedings of the 26th International Cosmic Ray Conference, in press (1999)

Abstract:

The deposition of energy into the solar wind is argued to result from the dissipation of low frequency magnetohydrodynamic turbulence via kinetic processes at spatial scales comparable to the ion gyroradius. We present a theory for heating the solar wind that relies on fluid processes such as wind shear inside about 10 AU and the pickup of interstellar ions and the associated generation of waves and turbulence beyond the ionization cavity to serve as energy sources for the heating. We compare the predictions of this theory to the observed magnetic turbulence levels and solar wind temperature measured by Voyager 2 beyond 1 AU. The contribution to the heating of the solar wind provided by interstellar pickup ions is a key feature of this theory and is chiefly responsible for the excellent agreement between theory and observation that is seen beyond 10 AU.