The ENA, Ring Current, and Auroral Response to ``Sawtooth Injections" in the October 4-6, 2000 Storm
Abstract
The October 4-6 geomagnetic storm reveals several interesting behaviors that illuminate the injection of plasmasheet material into the inner magnetosphere and the subsequent ring current and auroral responses. The storm began on October 4 in the second half of a North-then-South magnetic cloud. For nearly all of October 4 the IMF was only moderately southward with Bz around -10 nT. During that period of modest solar wind energy input geosynchronous satellites saw a series of ``sawtooth injections" which have a very characteristic temporal flux profile indicative of injection followed immediately by renewed plasmasheet thinning. Each sawtooth injection involves a large portion of the nightside and dusk-side magnetosphere. The injections are each accompanied by brightening of the auroral over a broad and expanded auroral oval. The geosynchronous injections are also apparent in simultaneous ENA images from the POLAR and IMAGE spacecraft which show that there is a true injection of fresh plasmasheet material into the inner magnetosphere and not simply an adiabatic reconfiguration of the magnetic field. During the period of sawtooth injections the Dst index decreased slowly to nearly -150 nT over an approximately 20-hour period. During that 20-hour decrease of Dst there is no evidence of trapping of injected ring current particles and nearly the entire build-up appears to be partial or untrapped ring current. The magnetospheric dynamics share many of the features of a ``steady magnetospheric convection" event in spite of the fact that there was nothing steady about the response in the inner magnetosphere. The long and slow main phase also provides an unusual opportunity for spacecraft to observe the dynamics during this event.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2001
- Bibcode:
- 2001AGUFMSM22B..10R
- Keywords:
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- 2720 Energetic particles;
- trapped;
- 2730 Magnetosphere: inner;
- 2778 Ring current