Histograms of the indices α for a radial dependence ∝R^α of the quasi-relativistic electron intensities in SEE events measured by MESSENGER. (a) Grey (purple) indicates the α indices for SEP events for which the longitudinal separation of the nominal footpoints of MESSENGER and the respective spacecraft observing near 1 au were ≤35° (< 20°). (b) Same as panel a, but including a correction for the different CA. (c), (d) Same as panels a and b, but including a calibration factor of 1.3 on STEREO measurements. The legend shows the mean and standard deviation and the median and median absolute deviation. Details are given in the text.