Multi-instrument Observations of the Formation and Evolution of Polar Cap Plasma Structures

Abstract:

Mid-latitude plumes of storm-enhanced density (SED) are an important source of large-scale plasma structures in the high latitude polar cap, such as the polar tongue of ionization (TOI) and polar cap patches. Several recent studies have highlighted the important role of the convection electric field in controlling the formation of these structures but there is still much to be learned about their detailed dynamics. Recent construction of a mid-latitude array of SuperDARN radars combined with the increasingly dense coverage of GPS receivers provides new possibilities to monitor how the convection electric field controls the dynamics of polar cap plasma structures over much wider spatial areas than was previously possible. Specifically, it is now possible to make continuous observations of convection electric fields and total electron content (TEC) at mid-latitudes in the region where the SED first appears, through the dayside auroral zone and cusp as the TOI evolves, and then into the polar cap where patches are formed and transported anti-sunward toward the nightside. Here, we present several recent event periods during which combined GPS-SuperDARN measurements were able to continuously monitor the formation and dynamics of the TOI and polar cap patch formation for several hours. In particular, we discuss the precise conditions under which the TOI and patches do or do not form and the controlling role of the convection electric field in modulating their dynamics.