Counts of magnetic flux ropes per calendar day in the third (top panel) and fourth (bottom panels) orbits. Flux ropes with different durations (in minutes) are distinguished by different colors. For the fourth orbit, the radial magnetic field B_R, proton density N_p, and proton plasma beta β_p are shown in the bottom three panels. The two HCS crossings are identified by black vertical dashed lines, the fourth perihelion (~0.13 AU) is indicated by a blue vertical dashed line, and the HPS is shown by the pink shaded area.