RADIAL GRADIENTS OF ION DENSITIES AND TEMPERATURES DERIVED FROM SWICS ULYSSES OBSERVATIONS

Mean density and temperature gradients of solar wind protons and alpha particles are derived from SWICS/Ulysses observations between 1.2 and 5.4 AU in the ecliptic plane during declining solar activity. All parameters are sorted in solar wind speed classes. The radial gradients show a similar behavior for both ion species. In the slow solar wind protons as well as alpha particles are found to expand adiabatically all the way out to many AUs, while in the fast wind ions evolve non-adiabatically and are heated by interplanetary sources. The alpha particle to proton temperature and density ratios are also determined. They do not show any clear radial dependence.