HR: 0800h
AN: SM31B-1223    [Abstracts]
TI: What are Sawtooth Events?
AU: * Henderson, M G
EM: mghenderson@lanl.gov
AF: Los Alamos National Laboratory, Mail Stop D466, Los Alamos, NM 87545 United States
AB: Sawtooth events are quasi-periodic, large-amplitude flux oscillations with a periodicity of 2-4 hours often seen during storms when the ring current is enhanced. They are driven by moderate ($|-B_z| < 10$nT) and steadily southward IMF conditions. The oscillations have been termed `sawtooth events' because their shape -- a series of slow flux decreases followed by rapid increases -- resemble the teeth of a saw blade. The `sawtooth' shape is particularly well-defined in the high energy proton channels. At geosynchronous orbit, each tooth is associated with strong stretching and dipolarization of the B-field and, while this activity is typically strongest on the night-side, it can also extend well into the day-side for larger sawtooth events. An abrupt recovery in Sym-H is typically observed in association with each dipolarization and each tooth is associated with dispersed particle injections and pre-midnight sector auroral substorm onsets Nevertheless, the auroral activity rapidly engages a wider than usual azimuthal range and the injections can also be dispersionless over a wider than usual range of MLTs. Thus, despite the many similarities to substorms, the more distributed (in local time) nature of sawtooth events has led to an on-going debate as to whether or not they really are substorms. Here, we compare and contrast the phenomenology associated with a number of individual sawtooth and substorm events. In particular, we present a re-analysis of a well-studied interval of substorm activity (the CDAW-9C interval) and demonstrate that it was also a sawtooth event. We will also present the results of a statistical study showing how substorms and sawtooth events relate to one-another on average.
DE: 2704 Auroral phenomena (2407)
DE: 2778 Ring current
DE: 2784 Solar wind/magnetosphere interactions
DE: 2788 Storms and substorms
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting