Radial dependence of the peak intensity, maximum first-order anisotropy, flux increase around the onset, and the time to maximum. Observations made by Solar Orbiter/EPT, Wind/3DP, and STEREO-A/SEPT are shown as blue circles, green triangles, and orange squares, respectively. The solid lines connect observations of the same event. The line colours correspond to the marker colours of the 1 au spacecraft. The dotted lines in the top panel show a dependence on I ∝ R⁻³.