Use of CLUSTER data in investigating the correspondence between different regions of inner magnetosphere and  ionospheric phenomena   
Mirela Voiculescu, Viviane Pierrard, Fabien Darrouzet, Marius Echim, Johan De Keyser
Coincident observations of middle and top ionosphere using  satellite tomography, radar measurements and plasmapause observations  with IMAGE and/or CLUSTER are used to investigate the relationship between  the F region trough and the plasmapause.  Several  F region troughs observed in tomographic  images  have been selected in order to study the correspondence with plasmaspheric  boundary . There is a very small probability to find CLUSTER data that are both spatially and temporally coincident with a F region trough, however, satellite data available at the  moment of trough observations can be used to certify the validity of the plasmapheric model used for evaluating the position of plasmaspheric boundaries. These data are also used to specify characteristics of the trough and specific regions of the inner magnetosphere.  The position of the plasmapause can be estimated, presumably, from ionospheric data, as for instance the equatorial border of auroral precipitation, the light ion trough, the occurrence of red auroral arcs or enhancements of subauroral electron temperature.  Zonal rapid  ion drifts, known as subauroral ion drifts, occurring in the ionosphere in both westward and eastward directions, also indicate a strong coupling with the inner magnetosphere. Possible mechanisms that generate the well-known SAIDs and the recently discovered ASAIDs are analysed.  We discuss here the role of  background magnetospheric and solar wind conditions (geomagnetic activity, solar wind pressure, IMF orientation, etc) in  the coupling between the F region trough and the plasmapause and their relevance for the magnetosphere-ionosphere coupling.