Energy spectra of downgoing protons. The dashed lines and solid lines correspond to the outer sphere at r = 3960 km and inner sphere at r = 3636 km, respectively. The spectra are averaged in different solar zenith angle intervals. In panels (a)–(c), the black and grey lines correspond to the solar wind protons and exospheric protons, respectively, and the curves are averages over the hemispheres. In panels (d)–(f), the black, light grey and dark grey lines correspond to the hemispheres and the average of both hemispheres, respectively, for all protons. The upstream solar wind spectrum is shown as a thick black line in panel (a).