Fig. 1: The community structure of a substorm on the 16/03/1997.

The abscissa of all panels is normalized time (\(t^{\prime} =0\) is onset (dashed green line) and \(t^{\prime} =30\) (dashed purple line) is the time of maximum auroral bulge expansion). Vertical gray dashed lines show ten normalized minute intervals within the expansion phase. a, b Plots individual communities as circles where the size of the circle reflects the number of connections within the community. The ordinate plots the mean magnetic local time/latitude (MLT/MLAT in h/degrees) of the community, \(\bar{{\theta }_{x}}(t^{\prime} )\) and \(\bar{{\phi }_{x}}(t^{\prime} )\), and the color indicates the proportion of connections with each time lag, ∣τ_c∣. The dashed lines overplotted are the edges of the auroral bulge (MLT) and the onset location (MLAT), found from auroral images. c, d Show the spatial extent of each community, where the dots are the magnetometer locations and the shading is the extent. Color represents the mean MLT of the stations contained within each community, \(\bar{{\theta }_{x}}(t^{\prime} )\). e Plots the modularity, Q, (blue line) and the random phase surrogate (black line). f Plots the normalized number of connections, \(\alpha (t^{\prime} )\), both within the nightside (solid blue) and within the SCW (dashed blue), as well as their surrogates (solid and dashed black, respectively, both near-zero throughout). The right ordinate plots (negative) SML (red).