Ring Current Composition During Sawtooth Storms

J. Jahn, J.D. Perez, P.C. Brandt, D.G. Mitchell, M.G. Henderson, 
and C.J. Pollock


Recent IMAGE observations have shown that the gradual development of the
hydrogen ring current during sawtooth storms is accompanied by a bursty
occurrence of oxygen. The observed oxygen energetic neutral atom (ENA) fluxes
are as high, if not sometimes higher, than oxygen fluxes associated with
non-sawtooth storms. They appear predominantly during individual sawtooth
injections. Once a sawtooth injection has occurred, oxygen ENA fluxes quickly
abate due to a combination of precipitation, drift loss and charge exchange. We
use ENA inversion techniques to estimate the amount of hydrogen and oxygen
plasma in the inner magnetosphere during sawtooth events. Due to the orbit of
IMAGE we can monitor the plasma content for 70-80 percent of the time, split
into uninterrupted stretches of up to 10 hours apiece. This coverage allows us
not only to study the time development of the ring current and the oxygen
content during a storm, but to also study several consecutive "teeth" without
interruption. We present results from several sawtooth storms that occurred
since the fall of 2001. We show the time development of the ring current during
those storms, and contrast it with the time history of observed oxygen. For
comparison, we will also show data from non-sawtooth storms since 2001

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Presentation, Fall A.G.U. Meeting, San Francisco, CA, 13-17 December 2004