The structure of the plasma sheet under northward IMF

Studies on the properties of the plasma sheet have shown that it becomes cold and dense (T < 2 keV, n > 1 cm^-3) during extended northward IMF periods and this change in the plasma status is most prominent close to the flanks. When these Cold and Dense Ions (CDIs) are transported earthward, it is reasonable to expect the compression to keep the density high whereas the temperature is elevated by adiabatic heating upon compression. This process should produce Hot-Dense Ions (HDIs) at the inner-edge of the plasma sheet. By defining HDIs with the criteria T > 2 keV, n > 1 cm^-3, HDIs have been searched for using five years data of the Geotail spacecraft. HDIs are indeed found, and when focusing on those HDIs obtained under nominal solar wind dynamic pressures, we find them to appear only on the dawnside plasma sheet inner-edge and that during extended northward IMF intervals. That is, the result supports the idea that HDIs are the inner-magnetosphere extension of CDIs, and further imply that such a connection between the two populations takes place only on dawnside. In this paper, we describe the statistical study that reveals this structure of the plasma sheet. This picture suggesting significant dawn-dusk asymmetry in heating and transport in the magnetotail under northward IMF is also tested by case studies in which we inspect data from fortuitous orbits that transverse more than one key region under steady IMF/SW conditions. We also study data from multi-spacecraft monitoring the key regions simultaneously. Expected features are seen in these independent studies implying that the picture obtained by the statistic study indeed reflects the spatial structure of the plasma sheet under northward IMF.