Simultaneous observations of quasiperiodic emissions by spacecraft and ground-based instruments

We present an analysis of conjugate observations of quasiperiodic (QP) emissions by a ground-based instrument (Kannuslehto, Northern Finland) and spacecraft (Van Allen Probes). Altogether, 26 events observed between September 2012 and November 2017 were analyzed. The study focuses on how the structure and intensity of the events vary during observations at different locations. It is shown that the structure of QP elements is conserved over a large spatial extent, while their intensity can change significantly. The magnetic local time extent of the events as well as their occurrence with respect to the plasmapause location were further analyzed. The magnetic local time separation between the instruments during the times of simultaneous detections of the events was typically lower than about 4 hours. Most of the detected events occurred inside the plasmasphere. Finally, properties of ultra-low frequency magnetic field pulsations measured by ground-based magnetometers at the times of the events were investigated.