Fig. 3.

AMPTE-IRM SULEICA observations of interstellar ${\text{He}}^{+}$ PUIs (filled circles) from sectors pointed near the Sun. Measurements correspond to times when the solar wind speed $V_{\mathrm{SW}}=\sim 680\text{km}{\text{s}}^{-1}$ and the angle between the solar wind flow velocity and IMF was $\sim {90}^{\circ }$ and $\sim {135}^{\circ }$. Models for the PUI distribution functions following Vasyliunas and Siscoe (1976) are also shown (stars with solid curve). From Möbius et al. (1988). Reproduced with permission from Springer Nature