Fig. 7.

Velocity distribution functions as a function of $w=v/V_{\mathrm{SW}}$ for ${\text{H}}^{+}$ and ${\text{He}}^{+}$ observed by Ulysses SWICS during a time when Ulysses was in the high latitude, fast solar wind. Multiple populations of ions were observed, including the core SWIs, interstellar PUIs, and the inner source PUIs. Fits to the interstellar PUI distributions assuming strong pitch angle scattering (“isotropic”, dashed) and weak pitch angle scattering (solid) are also shown, indicating better agreement under the assumption of weaker scattering allowing anisotropic distributions to form. From Gloeckler and Geiss (2001b). © Springer. Reproduced with permission