Monday

We quantify the spatio-temporal evolution of the substorm ionospheric current system utilising the full set of 100+ SuperMAG ground based magnetometers. We use this magnetometer data to construct dynamical directed networks for the first time. If the canonical cross-correlation between vector magnetic field perturbations, observed at two magnetometer stations, exceeds an event and station specific threshold, they form a network connection. The time lag at which cross-correlation is maximal determines the direction of propagation or expansion of the structure captured by the network connection. If spatial correlation reflects ionospheric current patterns, network properties can test different models for the evolving substorm current system. This analysis has been used to compare 86 isolated substorm events, chosen based on nightside ground station coverage. We obtained the timings for, a consistent picture in which the classic substorm current wedge (SCW) forms. A current system is seen pre-midnight following the SCW westward expansion. Later, there is a weaker signal of eastward expansion. Finally, there is evidence of post-substorm convection. The effectiveness of this methodology and the resulting sequence of substorm current system evolution will be discussed.