The Ionosphere – Theremosphere – Magnetosphere coupling during Storm and Substorm Recovery Phases -project (ITM Recovery, PI Tuija Pulkkinen) was a collaboration within CLaSP with Professor Mike Liemohn and Professor Shasha Zou with contributions from Sanjay Kumar and Connor DiMarco. The project focused on processes during substorm and storm recovery phases, especially addressing why and how geomagnetic activity subsides. The project also addressed the effects of Subauroral Polarization Streams (SAPS) on the electrodynamics at the interface between the hot and cold particle populations in the inner magnetosphere as well as the conjugate ionosphere and thermosphere.

We used the THEMIS observations to study the magnetic field changes during the course of magnetospheric substorms at different downtail distances. We showed that the earliest substorm signatures are seen in the transition region magnetotail, but the differences in timings were of the oder of minutes. 

This figure shows the magnetic field evolution at three different distances (top – closest to the Earth, bottom – furthest from the Earth). The three columns show averages centered around substorm onset, peak of substorm activity, and at the end of the activity. We argue that the clearest signals were seen in the center panels at each time, pointing to its key role in the substorm process. Figure credit Sanjay Kumar.
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