Asymptotic directions of polar NMs. The abbreviations are given in Table 1. The color lines depict asymptotic directions plotted in the rigidity range 1–5 GV, for DOMC, SOPO, SUMT and VSTK from 0.7 to 5 GV respectively. The dashed lines correspond to new NMs proposed for extension of the network or to be reopened. The lines of equal pitch angles relative to the anisotropy axis of example event are plotted for 15° and 30° for sunward direction. The figure is adapted from Mishev et al. (2018a).