Fig. 9

Simulated gradient \(d(\Delta \theta )/df\) against frequency for the simulation parameters used in Fig. 2b. The open circles and triangles represent solar wind speeds of 340 and 420 km \(\hbox {s}^{-1}\), respectively. The black lines give the gradient of the observed average and standard deviation, and the coloured bands give the gradient of the scatter-free cases. The uncertainty in the simulated gradient is a combination of the scatter (represented by the standard deviation \(\delta \theta _0\)) and 25% uncertainty in the frequency (i.e., 50% uncertainty in the density).