Relationship Between Global Plasmapause Characteristics and Plasmapause Structures in the Frame of Interchange Instability Mechanism

Bandić, Mario [Astronomical Observatory Zagreb, Zagreb, Croatia] Verbanac, Giuliana [Faculty of science, University of Zagreb, Zagreb, Croatia,] Pierrard, Viviane [UCL]

Recent studies based on CLUSTER, CRRES, and especially on THEMIS satellite data have revealed the statistical behavior of the global plasmapause such as eastward azimuthal plasmapause propagation and radial plasmapause motion between 21 and 07 magnetic local times (MLTs) most likely at postmidnight. The results are shown to be in a good agreement with characteristics of the plasmapause modeled using interchange instability mechanism. The present study is based on the plasmapause modeled with the mentioned physical mechanism, and it aims to link the observed global plasmapause dynamic with formation and evolution of plasmapause structures.We investigated two plasmapause datasets obtained using real Kp values and certain type of time-dependent changes in the Kp (thereafter Kp jumps) as input in the simulations. The Kp jumps include sharp Kp increase, sharp Kp decrease, short-time burst enhancement (increase-decrease within 3 hr) in Kp, and their combinations in order to obtain plumes, shoulders, and notches, the structures most often observed in the nature. The cross-correlation analyses is applied to the modeled plasmapause and to the geomagnetic Kp index at different 1-hr MLT bins.We have shown that the cross-correlation curves provide deeper insight in the physical processes related to the plasmapause dynamic and evolution. Their behavior is interpreted as the imprint of the plasmapause structure passages through specific MLT sector. Taking into account that the plasmapause in the single events shows very complex and different behaviors, the most important finding of the present study is the simple explanation of what causes global plasmapause motions and deformation in time.