Abstract
After summarizing typical features of the plasma sheet boundary layer, this review will be addressed to that topic where a major advance was made during the last two years, namely understanding the role of the plasma sheet boundary layer in magnetospheric substorms. After a description of motivation and key features of the recently developed ‘boundary layer model’. I shall list several assumptions made in this model which do not seem explored deeply enough yet as well as observations which cannot be explained within the framework of this model. I will end with an update of the ‘near-earth neutral line model’, recent simulations of which now explicitly include boundary layer flows. I come to the conclusion that the near-earth neutral line model still explains the wealth of substorm phenomena more comprehensively, but that certain refinements are needed. The boundary layer model, on the other hand, describes certain substorm features quite well but needs to be considerably extended before it can serve as a coherent description of all substorm phenomena.
