IMAGE, POLAR, and geosynchronous observations of substorm and ring current 
ion injection  

G. D. Reeves, M. G. Henderson, R. M. Skoug, M. F. Thomsen, J. E. Borovsky, 
H. O. Funsten
Los Alamos National Laboratory, Los Alamos, New Mexico

P. C:son Brandt, D. J. Mitchell
Johns Hopkins APL, Laurel Maryland

J.-M. Jahn, C. J. Pollock, D. J. McComas
Southwest Research Institute, San Antonio, Texas

S. B. Mende
University of California, Berkeley California


The geomagnetic storm of October 4-6, 2000 provides an exceptionally good
opportunity to examine the role of substorms during the storm because of the
relatively moderate solar wind driving and because of the excellent set of 
satellite observations. We show that the entire day of October 4 was 
characterized a sequence of substorms and a gradual build-up of the storm-time 
ring current. We examined one of those substorms in some detail showing that 
it had the expected signatures of a magnetospheric substorm. ENA observations 
and in situ measurements show that the substorms clearly do provide a mechanism 
for transporting energetic ions from the magnetotail to the inner magnetosphere.
Substorm injections do not, however, provide the only mechanism. As other
studies have suggested, the evidence from this storm shows that the presence of 
a quasi-steady convection electric field plays an additional important role. 
This is seen through the comparison of Dst which decreases slowly and smoothly 
over nearly 10 hours with geosynchronous particle injections which occur 
impulsively at roughly 2-hour intervals producing a "sawtooth" injection profile. 
Further evidence comes from ENA observations that show both impulsive injection
during substorms and continued intensification and eastward expansion in
response to convection electric fields. We also investigate the transport and
symmetry of the ring current particles. We find that, even more than 10-hours
into the storm when Dst had decreased below -100 nT and at least five clear
substorm injections had occurred, the ring current remained highly asymmetric
with essentially no ENA emissions from the dawn-to-noon sector. We also find
that Dst, SYM-H, and ASY-H all respond approximately equally in spite of the
fact that there is apparently no symmetric component to the ring current until
later in the storm.

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Submitted to AGU Monograph on the Storm-Substorm Relationship, October 2001.