Friday

The orientation of field-aligned current sheets (FACs) can be inferred from dual-spacecraft maximum correlations between two Swarm spacecraft (A and C). The correlation and inferred orientations show clear trends in magnetic local time (MLT), which can show the behaviour of both large and small scale currents. Individual events also sampled by higher altitude spacecraft (e.g. Cluster), in conjunction with Swarm or other LEO satellites, also show two different domains of FACs: time-variable, small-scale (10s km), and scaled, large-scale (>100 km) FACs. The FACs map to R1/R2 auroral boundaries so potentially can be combined with future SMILE data. Conjugate effects seen in ground magnetic signals (dH/dt) can be identified. Intense dB/dt variations take place in the main phase of a geomagnetic storm, particularly during active substorms. Demonstration of directly driven dB/dt by bursty bulk flows (BBFs) at geosynchronous orbit is rare. The recovery phase of a geomagnetic storm on 7 January 2015 were covered by multi-point measurements, allowing Cluster and SWARM measurements to be combined with a group of ground-based magnetometer observations to show the characteristics and response. The locations of Cluster and SWARM map to the same conjugate region as the magnetometer ground stations at the time of the BBF, showing that corresponding signals in all measurements occur simultaneously (with suitable time lags) in this region. Around substorm onset the most intense dB/dt (dH/dt) variations are associated with FACs, corresponding to a modified SCW, driven by BBFs at geosynchronous orbit.