Proton energy spectrograms and magnetic-field observations from PSP on 2023 March 13, 02:00–12:00 UT. Top panel: proton differential flux energy spectrograms from PSP/IS⊙IS EPI-Lo (ChanP) for the sunward-looking apertures, which sample anti-sunward-streaming particles. Middle panel: the same for the anti-sunward-looking apertures, which sample sunward-streaming particles. Bottom panel: PSP/FIELDS magnetic-field components B_R (orange), B_T (teal), B_N (gray), and ∣B∣ (black) in radial-tangential-normal (RTN) coordinates, with vertical dashed lines marking the five pitch-angle distribution (PAD) snapshot times used in Figure 2. The shaded band marks the EPI-Lo data gap caused by instrument saturation following the shock crossing.