OBSERVATIONAL AND THEORETICAL ASPECTS OF PROCESSES OTHER THAN MERGINGAND DIFFUSION GOVERNING PLASMA TRANSPORT ACROSS THE MAGNETOPAUSE

The magnetopause and its inner contact region with the magnetosphere, the magnetospheric boundary layer, constitute the interface between th e shocked solar wind plasma and the magnetosphere. Indeed magnetosheat h plasma has to cross the magnetopause in order to access the Earth's magnetosphere. The issue here is to identify the physical processes th at govern plasma transport across the magnetopause, plasma that subseq uently flows along the inside of the magnetopause boundary in the magn etospheric boundary layer. Some other relevant questions concerning ma gnetosheath plasma entry are: - how ''deep'' inside the magnetosphere does magnetosheath plasma penetrate? - is the plasma entry predominant ly steady or transient? -is the magnetospheric boundary layer on open or closed geomagnetic field lines? - to what extent can merging/reconn ection qualify as a general plasma entry mechanism? - does plasma diff usion represent a major steady state entry process? - what processes, besides merging/reconnection and diffusion may govern magnetosheath pl asma entry into the magnetosphere. Magnetosheath plasma energy, mass a nd momentum transfer into the magnetosphere remains a matter of contro versy. A number of workers in our field, perhaps a majority, has taken the stand that the issue is essentially settled and that merging/reco nnection, possibly complemented by some weak plasma diffusion, suffice s to explain the entire transfer of solar wind energy, mass and moment um into the magnetosphere. It is the purpose of this paper to discuss observational results of magnetosheath plasma entry that neither corro borate merging/reconnection nor a ''weak'' plasma diffusion as access mechanisms for magnetosheath plasma into the magnetosphere. The intent is not to rule out merging/reconnection as a class of plasma access p rocesses, but rather to point out that observations suggest more oppor tunities for plasma entry than conceived in existing MHD-based models. Moreover, these observations suggests that the solar wind energy, mas s and momentum transfer into the magnetosphere and the Earth's ionosph ere must be put in context with a current circuit that couples deceler ation in a dynamo/generator region with acceleration/heating in a load region. Indeed, observations suggests that transient reconnection phe nomena such as flux transfer events are related with field aligned cur rents.