Joint ground/space observations of transient phenomena associated with the Polar cusp

This thesis concerns the study of solar wind entry into the near-Earth environment via the process of time-varying reconnection. Specifically, the plasma signatures associated with this magnetic flux transfer were investigated in the context of the upstream interplanetary conditions. Thus study is primarily accomplished with the Polar spacecraft, situated in the mid-altitude cusp, but also utilises low-altitude spacecraft and ground-based instrumentation to trace solar wind entry into the near-Earth space environment.;A detailed case study is presented of the energy-dispersed pulsed particle signatures (PPS) observed in the mid-altitude cusp by Polar. Two discrete time-scales of PPS were observed and linked to the prevailing IMF conditions. The simultaneous observation of two different frequency components has not previously been reported in the mid-altitude cusp.;A second, complementary case study was conducted utilising the definitions outlined in the previous study to relate PPS to the low-altitude and ionospheric signatures of transient reconnection. Although there is no direct 1:1 relationship between the mid-, low-altitude and ionospheric signatures of reconnection in this case study, the ionospheric footprints of all three signatures are closely located in time and space.;Finally, the location and occurrence statistics of PPS observed in the magnetosphere and traced into the ionosphere are investigated with respect to IMF orientation and the solar wind dynamic pressure. PPS were found to occur over a wide range of latitudes and local times, and also found to favour southward IMF in terms of increased numbers and percentage occurrence, than its positive Bz counterpart.