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			 **   THE GEM MESSENGER   **
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						     Volume 10, Number 3
						     January 6, 2000

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1999 GEM Snowmass Workshop Reports
Magnetotail/Substorm Campaign: Substorm Observations Working Group
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From: Mark Moldwin (moldwin at galileo.pss.fit.edu)

Co-Chairs: Shin Ohtani - JHU/APL and
           Mark Moldwin - Florida Institute of Technology

GEM 99 was the second workshop in which the working group named "Substorm
Observations" held sessions. The goal of the working group is to identify
all the substorm onset signatures - model independently - and to attempt
to organize them in terms of their temporal relationship. The focus on
this years workshop was the relationship betweeen mid-tail and near-Earth
substorm signatures. The working group had one plenary tutorial: Vasilius
Angelopalous from UC-Berkeley described current research on the
relationship between mid-tail plasmasheet flows and substorm onset
signatures in the near-Earth.

The working group had five sessions:Substorm Onset Timing, Pi 2 Propagation
(a joint working group with Chris Russell's "Special Session on Groundbased
Magnetometry"), Onset associated plasmasheet dynamics I, Onset associated
plasma-sheet dynamics II, and one summary discussion session. The first two
working group sessions were a continuation of the GEM 98 workshop. At that
workshop the idea that a reference time for ordering substorm phenomenology
and signatures is needed to be able to compare results from a variety of
instruments, platforms, locations, and definitions. Mid-latitude, nightside
Pi 2 pulsations were suggested to be this substorm onset T(reference).
Semantically T(reference) was preferred to T0 in that it does not imply the
initial cause of substorm onset but rather a fiducial which can be used to
order different observations. Studies that look at the relative timing and
consistency of ordering of different substorm signatures with respect to
mid-latitude Pi 2s were suggested. At GEM 99 this idea was followed up and
was the topic of a student tutorial by Bob McPherron. Unfortunately many
studies presented at the GEM 99 workshop still used different signatures to
identify onset time. These included studies presented in the Onset
associated plasma-sheet dynamics sessions. Both modeling and observational
studies were presented. Good discussion in these sessions motivated the
co-chairs to propose a special session on this topic for the Fall AGU
meeting. A special  "Connection Between Midtail and Near-Earth Substorm
Processes" session will be held at the Fall 99 AGU as an outgrowth of this
working group.

GEM 2000 will continue this working groups objectives of identifying and
ordering substorm onset signatures. Working group sessions on substorm
timing, and substorm signatures in the plasma sheet will be the focus of
this years workshop.

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