The frontside boundary layer of the magnetosphere and the problem of reconnection

Further Heos 2 plasma and magnetic field data obtained in the frontside boundary layers of he magnetosphere are presented. They reveal hat the low-latitude extension of the entry layer is of a somewhat different nature. The most pronounced difference with respect to the entry layer in the cusp region is the substantial density jump at the magnetopause. Furthermore, the low-latitude boundary layer tends to be thinner and less turbulent, and the flow velocity inside the layer is always lower than that of the adjacent magnetosheath. This observation excludes large-scale reconnection at the front of the magnetosphere as he origin of the layer. It is suggested that diffusive entry of magnetosheath plasma and/or heating of detached plasma from the plasmasphere leads to the formation of the layer. It appears likely that reconnection is dominantly occurring as a transient process in the cusp region and accompanies the eddy convection inside the entry layer. As a consequence, magnetic flux is being eroded from the front of the magnetosphere. This is in agreement with the signature of short-term large-amplitude magnetic perturbations observed in the low-latitude boundary layer.