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                **   THE GEM MESSENGER   **
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                                   Volume 4, Number 16
                                   September 6, 1994

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REPORT ON 1994 SNOWMASS WORKSHOP - BOUNDARY LAYER CAMPAIGN -- Part III
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           WG 2: PARTICLE ENTRY, BOUNDARY STRUCTURE AND TRANSPORT       
                  co-chairs: Chris Russell and Lou Lee         

The coordinators of this working group, L. C. Lee and C. T. Russell, this
year choose to concentrate the working group's attention on the formation
of the boundary layer. The first talks reviewed our observational 
understanding of the boundary layer. The boundary layer appears to be 
controlled intimately by the IMF. Guan Le reviewed the boundary layer
when the IMF is northward. She finds two types of boundary layer plasma.
One type is a simple mixture of magnetospheric and magnetosheath plasma.
Another consists of heated magnetosheath plasma. She also finds that 
the boundary layer thickens with distance away from the nose. Michelle
Thompson showed that when the IMF is southward the boundary layer is formed
on field lines that are open to the magnetosheath. There is an inner edge
to the ion boundary layer and a separate one for the electron boundary 
layer formed by the fastest particles on the field lines passing 
through reconnection point. Much more work needs to be done on the 
boundary layer. A project initiated by Jerry Chao to catalogue the entire
ISEE magnetopause file may help greatly in this respect.

The low latitude boundary layer also manifests itself at low altitudes in 
the auroral ionosphere. Dave Sibeck reviewed the measurements obtained 
of the LLBL by the DMSP Satellites. His principal warning was to be careful
in such studies because it was clear that plasma that was classified as 
LLBL could arise from more than one source. G. Fasel rounded out the 
observationally oriented talks with a discussion of the ionospheric evidence
for magnetic reconnection for northward IMF. This evidence consists of 
the many polar moving auroral forms seen for northward IMF. 

The theory of the low latitude boundary layer was addressed by E. Drakou,
P. Song, L. Lee and B. Sonnerup. E. Drakou's model depends on momentum 
transport across the velocity  shear layer at the magnetopause. In her
model the velocity accelerates away from the nose. In the model
of P. Song, reconnection injects plasma in the noon magnetosphere and
pressure gradients drive it tailward but it slow down due to ionospheric
drag. Lou Lee reviewed the work of Jay Johnson on the formation of the
LLBL by Kinetic Alfven waves and of Antonius Otto on linkage induced 
reconnection and boundary formation.

Bengt Sonnerup gave a comprehensive reviews of the unresolved issues 
and concluded that the unresolved issues need more observational 
guidance for their resolution. We need to identify which field lines 
are open and which lines are closed in the boundary layer.  We need to 
be able to construct true spatial profiles. We need to be able to map 
magnetic field lines from the magnetosphere to the ionosphere. We need 
to understand better potential drops along magnetic field lines, the 
dawn dusk asymmetries in the magnetosphere and the role of micro versus 
macroscopic instabilities. To solve these problems we will require a
combination of understanding better existing data and also the analysis
of data from new missions such as Cluster.

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