Friday

The auroral substorm can be thought of as an amalgamation of energy conversion processes in the magnetosphere-ionosphere system. At its simplest, stored magnetic energy is converted into particle and wave energy which impinge on the ionosphere and are converted into auroral emissions, ionospheric currents and Joule heating. The auroral, wave and current signatures all show an enhancement then subsequently wane after substorm onset and seem to show an initial spatial localisation before spreading to multiple local time sectors. However, while broadly similar, the specifics of these variations differ for each of these signatures. In this study, we show that the auroral intensity shows similar variations to ULF wave amplitude in the substorm onset sector, peaking in the minutes after onset, but more closely follows the ground perturbations associated with ionospheric currents towards dusk and dawn. The ground magnetic perturbations show a very different pattern to the auroral emission and wave amplitudes, peaking in amplitude some 20-30 min after onset and several hours of local-time east of the onset sector. These results show that multiple energy pathways, separated both in time and space, exist for substorms and thus the timings for different space weather impacts may vary.