We present a recent study to identify new synergistic opportunities for magnetosphere-ionospherethermosphere (MIT) coupling investigations, by taking advantage of the complementary nature of the orbital (particularly altitude and local time) coverage and unique measurement capabilities of CASSIOPE e-POP, as an added component to the Swarm satellite constellation under European Space Agency’s Third Party Mission programme. The coordinated operation of the e-POP payload with Swarm, in particular the Magnetic Field (MGF), GPSreceiver- based Attitude, Positioning and Profiling (GAP) and Fast Aurora Imager (FAI) instruments, will enable or enhance a host of new investigations on the Earth’s magnetic field and related current systems, upper atmospheric dynamics, auroral dynamics, and related MIT coupling. These include (a) magnetic field perturbations at high latitudes, specifically their small scale structures, altitude distribution and longitudinal extent; (b) thermospheric density variations, plasma density irregularities, and density forecasts for orbit prediction; and (c) electrodynamics of the auroral arcs and magnetosphere-ionosphere coupling. These investigations are expected to contribute significantly to two of Swarm’s four primary research objectives, and to advance our fundamental knowledge on MIT coupling and the effects of associated space weather processes on the Earth’s magnetic field and its ionosphere and thermosphere. @en