Fig. 2

Deviation of the longitude of the fitted peak intensity from that at 0.9 MHz (\(\theta _0\) in Fig. 1). (a) Observational data. The solid and dashed red lines show the average and standard deviation of the fitted data from Fig. 8. The blue and green bands show the longitude deviation in the scatter-free cases, assuming the emitter propagates along a Parker spiral at distances corresponding to fundamental (blue) and harmonic (green) frequencies. The angle of the Parker spiral at a given distance for a given solar wind speed is calculated as \(\theta = -\arctan (\Omega r/v_\textrm{sw})\). The upper and lower bounds of the coloured bands correspond to a range of \(v_\textrm{sw} (1~\textrm{au})\) for the solar wind between 340 km \(\hbox {s}^{-1}\) (lower bound) and 420 km \(\hbox {s}^{-1}\) (upper bound)³⁸, as shown in the inset. The dot-dashed line represents the harmonic scatter-free case with an unrealistic solar wind speed of 50 km \(\hbox {s}^{-1}\). (b) Simulation data using different turbulence scaling factors between \((0.5-2.0) \, \times\) the nominal profile³⁹. The bounds of each band correspond to different solar wind speeds as in the left panel. The sources are injected along the same Parker spiral field line for a given \(v_{\textrm{sw}}\). For each simulation, the longitude of peak directivity \(\theta _0\) is referenced with respect to that at 0.9 MHz from the nominal simulation data.