(a)–(b) Average velocity distribution functions and normalized PADs (normalized to the maximum among all PA bins) of He⁺ observed by the SWS during “D1,” “D2,” and “U2” indicated in Figure 2; (c)–(d) same as (a)–(b), but for H⁺. The PADs are averaged over w_sw ∼  1.2–2.5 (dashed lines in (a)) for He⁺ and w_sw ∼ 1.5–4 (dashed lines in (c)) for H⁺. The selected range of w_sw ∼ 1.5–4 in (c) is far above the velocity of the small channel switch. The PSDs in (d) are obtained without applying the base rate weight. The estimated statistical errors are shown in each panel.