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			 **   THE GEM MESSENGER   **
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						     Volume 6, Number 23
						     May 7, 1996

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GEM Snowmass, 1996 Summer Meeting
Tail/Substorm Campaign Working Group 2 Activities
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From: Terry Onsager (tonsager at sec.noaa.gov)

 Co-Chairs: Harlan Spence (spence at bu-ast.bu.edu)
            Terry Onsager (tonsager at sec.noaa.gov)

Working Group 2 has been focusing on the combination of theories/models
and data to facilitate the quantitative testing of theories and models and
to promote discussion on their capabilities and limitations.  At the 1995
GEM Snowmass workshop, Working Group 2 activities included discussions
of substorm trigger mechanisms and specific model predictions of various
aspects of magnetotail structure and dynamics.

Working Group 2 activities at the 1996 Snowmass workshop will
continue in these same areas, with the overall goal of testing models
and theories of magnetotail phenomena through comparisons with
observations.  We encourage anyone with specific model or theory
predictions that can be quantitatively tested with data, or those with
observational results that could provide important tests for models
and theories, to contact Harlan Spence or Terry Onsager to schedule
a presentation time during the workshop.  In addition, we would like
to discuss during the workshop the possibility of compiling a summary
document describing the capabilities and the limitations of current
models and theories, specifically identifying the areas where
quantitative tests with data have been accomplished and areas where
further tests should be done.

The three areas of focus in this summer's Working Group 2 sessions will be:

  1)  Substorm Triggering

  2)  Fluid vs. Particle Aspects of Magnetotail Convection

  3)  Specific Data-Model Comparisons


Substorm Triggering:

  Last year's session was devoted to identifying measurements that could
be used to quantitatively test specific predictions regarding substorm
triggers.  We would like to encourage presentations on both the
theoretical and observations aspects of substorm triggering.  Those
who gave presentations last year are encouraged to describe their
recent progress, and any new approaches are also welcome.

Fluid vs. Particle Aspects of Magnetotail Convection:

  We would like to welcome presentations on results relating to magnetotail
convection.  With the large observational data base that is now available
from multiple spacecraft and with the improved models of the magnetotail
that are being developed, we have the opportunity to address quantitatively
many aspects of magnetotail convection.  These issues include spatial
and temporal structure in the plasma convection, inductive effects,
location of the reconnection site, particle vs. fluid effects, etc.
We are particularly interested in discussing areas where quantitative
predictions or comparisons with data can be made.

Specific Data-Model Comparisons:

  The session last year covered a broad range of models and theories,
and many made specific predictions that were or could be tested with
current data.  The topics included Global 3-D MHD simulations, hybrid
simulations, substorm current disruption theories, the magnetospheric
specification model, static magnetic field models, particle trajectory
calculations, and an analytic model of the plasma sheet.  We encourage
those with models or theories of magnetotail processes that can be
tested quantitatively to present their results in this session.  We
also encourage presentations of observations that demonstrate features
that could test the current theories.



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