Relative frequency of the ecliptic longitude of particle perihelia (l_peri) recorded at semi-major axis bins of 0.05 au (no planets but Mars present, β = 0.005). The relative frequency is given for 60 bins in l_peri, thus a frequency of 1.67 × 10⁻² in each bin implies a uniform distribution. The ecl. long. of Mars’s perihelion (l_{peri,  Mars}) is indicated by the red line, as are l_{peri,  Mars} ± 90°. Mars’s perihelion and aphelion distances are indicated by vertical lines. Particle perihelia are equally distributed when in a semi-major axis range from 3 au to 2.5 au. As semi-major axis decreases, perihelia first gravitate towards l_{peri,  Mars} + 90°, followed by a stronger attraction towards roughly l_{peri,  Mars} − 80° once semi-major axis passes Mars’s aphelion distance. Migrating further, the particles’ apse line alignment relaxes again.