Rice Convection Model Simulation of an Idealized Sawtooth Event with Multiple Simultaneous Injection Fronts
Abstract
Sawtooth events are identified as quasi-periodic oscillations of energetic particle fluxes at geosynchronous orbit during recurrent substorm injections. During sawtooth events, magnetic field stretching and dipolarization can be remarkable in both the nightside and dusk sectors, and plasma injections associated with the tailward escape of plasmoids are typically very wide in local times. They are also accompanied by pronounced multiple north-south-aligned finger-like auroral structures in the ionosphere. However, what dynamical processes in the plasma sheet cause the dramatical changes at geosynchronous orbit and in the ionosphere is still unclear. In this study, we use the Rice Convection Model (RCM) to simulate an idealized sawtooth event. Our approach is to impose a local-time-dependent and time-dependent flux-tube entropy parameter at the RCM outer boundary to reflect what is known about the substorm-dependent phenomena as described above. Our simulation results are in good agreement with the magnetic field data and the energetic proton flux measurements at geosynchronous orbit, as well as the auroral structures. It confirms that interchange instability plays an important role in the expansion phase during sawtooth-time substorms. Our simulation results also show multiple simultaneous injection fronts near geosynchronous orbit at the beginning of substorm expansion phase. Based on simple drift physics, we calculated the onset time and location of each injection using energy dispersion profiles from LANL energetic proton and electron fluxes. We found that data-inferred injection fronts in one substorm event are consistent with multiple simultaneous injection fronts produced in the simulation.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMSM0410022S
- Keywords:
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- 2427 Ionosphere/atmosphere interactions;
- IONOSPHERE;
- 2736 Magnetosphere/ionosphere interactions;
- MAGNETOSPHERIC PHYSICS;
- 2740 Magnetospheric configuration and dynamics;
- MAGNETOSPHERIC PHYSICS;
- 2788 Magnetic storms and substorms;
- MAGNETOSPHERIC PHYSICS