Magnetotail behavior during storm time "sawtooth injections" 

A.T.Y. Lui, T. Hori, S. Ohtani, Y. Zhang, X.Y. Zhou, M.G. Henderson, T. Mukai, 
H. Hayakawa, S.B. Mende


A series of magnetic storms occurred during 16Ð21 April 2002 with multiple local
minima in the Dst index. During this storm period, Geotail traversed the
magnetotail from the premidnight tail lobe in the midtail region to the
postmidnight plasma sheet in the near-Earth region. Simultaneous observations of
energetic particles at the geostationary altitude showed the feature known as
"sawtooth injections" remarkably well from 18 April to 19 April. This
conjunction allows us to examine the magnetotail behavior in the tail lobe and
the plasma sheet associated with sawtooth injections. In the tail lobe, close
but not perfect time coincidence is found between injection onset and start of
southward dipping of the magnetic field vector in the tail lobe. Long-duration
(1Ð2 hours) southward dipping in the tail lobe magnetic field appears to be a
global behavior of the tail lobe in association with sawtooth injections. In the
plasma sheet, intermittent occurrences of plasma flow reversal from sunward to
tailward and of magnetic field from northward to southward are found. The
duration of southward magnetic field is typically short (1Ð5 min) within the
plasma sheet. There are some sawtooth injections that are not accompanied by any
significant changes in plasma sheet parameters (plasma flows, magnetic and
electric fluctuation levels), suggesting the plasma sheet behavior to be
localized even in association with sawtooth injections that are global in
nature. There was no indication of the magnetotail being driven in a relatively
"steady state" in association with sawtooth injections during this sequence of
storms.

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Journal of Geophysicla Research, 109, A10215, doi:10.1029/2004JA010543, 2005