Summary of the in situ magnetic field data analysed in this paper. In each panel, the shading is a 2D histogram with the x-axis in 1 day bins. A black solid line threads the histograms and shows themode of each day. Top panel: raw radial magnetic field measured by PSP. Magenta dashed vertical lines indicate successive perihelia of PSP. A faint dotted black line indicates an envelope (3 nT (1 AU/R²)) which communicates PSP’s changing heliocentric distance. The remaining three rows show the quantity B_RR² as measured by PSP, STEREO A and Wind respectively. The dotted horizontal line is the same envelope from the top panel scaled by R². In each panel, a solid red curve shows the spacecraft latitude. The polarity sampled is controlled primarily by the latitude. Panels on the right are 1D histograms which show in black (blue) the distributions of the 1 min average (full cadence) data of B_RR² summed over time.