Fig. 5.

Cassini CAPS measurements of ${\text{He}}^{+}$ (left) and ${\text{H}}^{+}$ (right) PUI fluxes divided by their 17-month average as Cassini traveled between 6.4 and 8.2 au downstream of the Sun. As demonstrated by the model results (solid curves), the ${\text{He}}^{+}$ PUI density decreased over long-term as Cassini traveled away from the interstellar He-focusing cone, and the ${\text{H}}^{+}$ PUI density increased over long-term as it traveled outside of the interstellar H shadow. From McComas et al. (2004)