In this second part of our statistical study of themid-altitude cusp, we compare the cusp morphology, as seen in the Clusterion spectrometer (CIS), to the interplanetary magnetic field (IMF)orientation. We first recall the method we have used a) to define the cuspproperties, b) to sort IMF conditions or behaviour in classes, c) todetermine the proper time delay between the solar wind monitors and Cluster.Then, we define a few morphological features of the cusp and we relate theseto the prevailing IMF. Our results reveal, among other things, that theoccurrence of clearly dispersed ion structures in the cusp is 48%. Fromthese dispersions, we infer the distance to reconnection site, which werelate to external conditions. In all other cases, the cusp exhibits a moredisturbed behaviour in terms of ion structures and fall in our"discontinuous" or "irregular" categories. Among these, a fewinteresting cases of discontinuous cusps occurring under stable IMFconditions have been identified. They all occur when the IMF is dominated byits Y-component, which plays in principle in favour of anti-parallelreconnection but their wide MLT and latitudinal distributions is a prioriincompatible with the anti-parallel reconnection hypothesis solely.
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