Exploring the physics of sawtooth oscillations from MHD-EPIC simulations
Abstract
The sawtooth events are global magnetospheric oscillations with a 2~4 hour period identified by the saw blade like signature of the energetic particle flux and magnetic field near geosynchronous orbit. Previous global numerical simulations suggest that the oscillations are generated by the ionospheric O + outflows (Brambles et al. [2011]). However, recent satellite observations demonstrated the ionospheric outflow is neither a necessary nor a sufficient condition for the generation of the sawtooth oscillations (Liao et al. [2014], Lund et al. [2017]). We use the MHD with embedded particle-in-cell (MHD-EPIC) model, which simulates Earth's magnetotail with a PIC code, to show the periodic magnetospheric oscillations can be generated even without the ionospheric outflow. We show that the magnetotail reconnection is not fast enough to balance the incoming magnetic flux during the stretching phase of a sawtooth, and the dipolarization phase is triggered by the onset of reconnection around x=-20 R E , where the reconnection rate is fast enough to release the magnetic flux due to the high ambient magnetic field strength. We will present the spatial features and temporal variations of the sawtooth oscillations from the MHD-EPIC simulation results, and compare the simulations with the observations.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMSM21B3144C
- Keywords:
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- 2723 Magnetic reconnection;
- MAGNETOSPHERIC PHYSICS;
- 2744 Magnetotail;
- MAGNETOSPHERIC PHYSICS;
- 7526 Magnetic reconnection;
- SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY;
- 7835 Magnetic reconnection;
- SPACE PLASMA PHYSICS