engleski

Relationship between plasmapause obtained from Cluster, solar wind and geomagnetic activity

Using Cluster satellite data and especially the observations of the instrument WHISPER from 2007 to 2011, we deduced the number density of the electrons along the orbit of the satellites to study the relationships between the plasmapause positions and different solar wind coupling functions and geomagnetic indices. A cross-correlation analysis is performed for three magnetic local time (MLT) sectors and for all MLT taken together. The plasmapause indicators suggest the faster plasmapause response in the post-midnight sector. The time lags are approximately 2-27 hours, always increasing with the MLT sector. The obtained fits clearly resolve the MLT structures. All studies show that the plasmapause is more earthward during geomagnetically active periods with the plasmapause bulge displaced toward dusk. The variability of the plasmapause is the largest for low values of the indicators. At low activity levels, the plasmapause position exhibits the largest values on the dayside and smallest in the post-midnight sector. Displacements towards larger values on the evening side (between 16 and 01 MLT) and lower values on the dayside (between 7 and 16 MLT) are identified for enhanced magnetic activity. Based on the correlation coefficients, we conclude that all studied indicators are capable to well describe the observed plasmapause position. Our results are used to improve our understanding of the physical mechanisms involved in the plasmapause formation.

plasmapause; geomagnetic activity; solar wind; Cluste satellite

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