Omnidirectional averaged phase-space density vs. proton velocity in the SWF for different time intervals. Three upstream intervals (a) and two downstream intervals (b) are labeled in Figs. 1 and 2. In panel (c), “Shock” indicates the average spectrum in the 12-s interval centered at the shock front, “Inverse event (sun)” indicates the average spectrum in the inverse-velocity dispersion event (same interval as U1) measured by the sunward telescope, and “Event (north)” indicates the spectrum of the peak fluxes in the velocity dispersion event measured by the northward telescope. The dashed lines indicate the slope of the power-law fit to the spectra in corresponding colors. The uncertainties are plotted as vertical or horizontal bars (but smaller than the symbols).