Global Imaging of Sawtooth Flux Variations

Skoug, R. M., M. F. Thomsen, G. D. Reeves, J. E. Borovsky, M. G. Henderson,
H. O. Funsten, C. J. Pollock, J.-M. Jahn, D. J. McComas, P. C. Brandt, and
D. G. Mitchell

During geomagnetic storms the fluxes of energetic particles observed at
geosynchronous orbit often exhibit a "sawtooth" profile, with quasi-periodic
repetitions of sudden flux increases followed by slower decays back to low
values.  Multi-spacecraft observations of some events indicate that the
sawtooth variations propagate rapidly around the earth, suggesting that they
represent some sort of global oscillation of the magnetosphere. However, a
recent analysis of the October 4-6, 2000 geomagnetic storm used global
images of energetic neutral atoms (ENAs) to demonstrate that the sawtooth
flux variations in that event corresponded to actual injections of new
material into the near-earth region, rather than an oscillatory adiabatic
reconfiguration of the magnetic field. In this study we examine sawtooth
flux variations from other storm-time intervals from mid-2000 to the
present, including August 11-13, 2000 and October 21-23, 2001. We combine
ENA images from the IMAGE satellite with geosynchronous particle
observations to determine the relationship between sawtooth variations and
the growth of the ring current, including particle transport and ring
current symmetry.

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To be presented at the Magnetospheric Imaging Workshop, 
Yosemite National Park, California, U.S.A., Feb. 5-8, 2002.