Fig. 9.

Observations of ${\text{H}}^{+}$ and ${\text{He}}^{+}$ PUIs and solar wind ${\text{He}}^{2+}$ from Cassini CHEMS measured during quiet times in the solar wind. The ${\text{E}}^{-1.5}$ common spectrum proposed by Fisk and Gloeckler is also shown. From Hill et al. (2009). © AAS. Reproduced with permission