Effects of Different Solar Wind Speed Profiles in the Heliosheath on the Modulation of Cosmic-Ray Protons

An asymmetric solar wind termination shock (TS) model is used to study the effects on the modulation of cosmic-ray protons for different scenarios of the solar wind speed (V) in the heliosheath. This two-dimensional model is applied using predictions for V the heliosheath that were calculated with a time-dependent three-dimensional hydrodynamic model. Decreases stronger than the generally assumed V 8 1/r super(2) in the heliosheath are studied, as well as an extreme case, V 8 r super(2), where r is the radial distance. The effect of the TS is enhanced under certain circumstances, and "barrier"-type modulation in the heliosheath also depends on the chosen V-profiles. Significant changes occur mostly for the A < 0 solar magnetic polarity cycle, at all distances in the equatorial plane, when the V is changed from an incompressible fluid (V 8 1/r super(2), v. = 0) in the heliosheath, to V 8 1/r super(8), in a symmetrical model. For the asymmetrical case the TS is predicted to be more effective in the heliospheric nose than in the tail, especially for the A < 0 cycle during solar minimum conditions. The different profiles for V do not have a significant effect on the intensities inside the TS, but in the heliosheath the difference can be quite significant. It is found that V 8 1/r super(2) in the heliosheath is an oversimplification. The consequent effects of having v. 0 in the heliosheath prove to be relevant for cosmic-ray modulation and acceleration, especially now that the Voyager 1 spacecraft encountered the TS and entered the heliosheath.