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			 **   THE GEM MESSENGER   **
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						     Volume 14, Number 19
						     May 26, 2004

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"Sawtooth Events" Session at GEM
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From: Mike Henderson  <mghenderson@lanl.gov> and
      Bob Clauer <rclauer@umich.edu>
         
The "Inner Magnetosphere / Storms (IM/S) Campaign" is planning a session
on "Sawtooth Events" for the 2004 GEM workshop (http://gem.rice.edu/~gem).

Sawtooth events are quasi-periodic, large-amplitude flux oscillations 
with a periodicity of 2-4 hours observed globally at geostationary orbit.
The oscillations have been termed 'sawtooth events' because their shape 
-- a series of slow flux decreases followed by rapid increases -- resemble
the teeth of a saw blade. The 'sawtooth' shape is particularly 
well-defined in energetic proton fluxes.  They occur during storms when 
the ring current is enhanced and they appear to be driven by steady, 
moderate to strong, southward IMF conditions (magnetic clouds).   The 
plasma sheet appears to be unusually close to the Earth at the time of 
sawtooth events and the inner magnetospheric plasma convection is strong.
                                                                                  
Although each 'tooth' of a sawtooth event exhibits many of the 
characteristics that one would normally associate with substorms (e.g.  
field stretching and dipolarization, particle injections, auroral onsets,
etc.), the disturbances rapidly engage a wider than usual range of 
magnetic local time sectors and the dipolarization and dispersionless 
injection signatures can extend past the terminators into the dayside. 
This and other considerations have raised issues regarding the nature of 
substorms, storm-time substorms, steady magnetospheric convection events,
direct driving vs. unloading, the inner magnetospheric pressure 
catastrophy, magnetospheric convection and energy dissipation.
                                                                                  
The purpose of this session is to: (1) establish more fully the 
observational characteristics of sawtooth events and to (2) address 
theoretical physical mechanisms that might explain their occurrence.  
Among the questions that need to be addressed more fully are:  Do 
sawtooth events form a specific class of substorms? How does the tail 
behave during sawtooth events?  What does the ring curent look like 
(asymmetry, composition, radial structure, etc.) during sawtooth events?
Why doesn't the steady solar wind conditions that drive sawtooth events 
not produce steady magnetospheric convection (SMC) events instead?  What 
current systems are responsible for the observed field changes on the 
ground and in space? Why are the injections so energetic (especially in
protons)?

Those interested in giving a brief presentation should contact the 
session convenors listed above.

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