HR: 1330h
AN: SH23A-04    [Abstracts]
TI: Turbulent Heating of the Distant Solar Wind by Interstellar Pickup Protons with a Variable Solar Wind Speed
AU: * Isenberg, P A
EM: phil.isenberg@unh.edu
AF: Institute for the Study of Earth, Oceans and Space, University of New Hampshire, Durham, NH 03824 United States
AU: Smith, C W
EM: charles.smith@unh.edu
AF: Institute for the Study of Earth, Oceans and Space, University of New Hampshire, Durham, NH 03824 United States
AU: Matthaeus, W H
EM: whm@udel.edu
AF: Bartol Research Institute, University of Delaware, Newark, DE 19716 United States
AU: Richardson, J D
EM: jdr@space.mit.edu
AF: Center for Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 United States
AB: We have been investigating the turbulent heating of the equatorial solar wind, as modeled by a phenomenological description of the turbulent evolution under the action of spherical expansion, shear driving in the inner heliosphere, and interstellar pickup proton driving in the outer heliosphere. This model is able to reproduce the radial trend of solar wind temperature observed at the Voyager 2 spacecraft out to nearly 80 AU. However, a detailed comparison with the observed solar-rotation-averaged temperature, which shows considerable spatial/temporal variation, is less than satisfactory. In particular, the solar wind temperature beyond 55 AU, measured during the most recent solar maximum period, is found to be consistently lower than predicted by our model and the variations of the observed and model temperatures are not well matched in phase. These differences may indicate the need for modifications in the turbulent evolution model, which presently contains a number of simplifications. However, the present model does not include several important physical effects, which should be treated before considering the effect of more complicated turbulence models. In particular, the well-defined slowdown of the solar wind due to the momentum loading by the pickup protons has not been incorporated. Neither has the dependence of the charge-exchange cross-section on solar wind flux been taken into account. Both of these effects are expected to reduce the predicted model temperature in the distant solar wind. We will extend the turbulent evolution model to allow these effects in the theory, and determine whether they result in significant improvement in the comparison with the Voyager observations.
DE: 2144 Interstellar gas
DE: 2149 MHD waves and turbulence
DE: 2152 Pickup ions
DE: 2164 Solar wind plasma
DE: 7863 Turbulence
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2005 Joint Assembly