Resulting expectations and measurements of the difference between the different measures of B_RR². In both panels, circles indicate results from the Parker spiral method, squares represent modes, and diamonds represent means, as a function of radius. Top panel: results for a purely synthetic data set using a Parker model for the “true” field and Gaussian* fluctuations in magnitude and clock angle as modelled by the linear trends shown in Fig. 5. Bottom panel: same measurements from the actual PSP data, binned into 0.05AU radial bins. Faint data points in the background show the computed values at one day intervals to show the general scatter (which clearly increases with radius). *Except where Gaussian fluctations would cause negative values of |B|; for details, see main text.