An explanation of the opposite dawn-dusk asymmetry at magnetotails of Earth vs. Mercury.?
Abstract
Using 3D particle-in-cell (PIC) simulations, we study magnetic reconnection with the reconnection x-line being spatially confined in the current direction. We find that magnetic reconnection develops internal asymmetry along the x-line (i.e., in the current direction), with the active region concentrated on the electron-drifting side. This is consistent with the MESSENGER observation, that indicates a higher occurrence rate of flux transfer events on the dawn-side of Mercury's magnetotail. Interestingly, this dawn-dusk asymmetry is opposite to that observed in Earth's magnetotail. An explanation for this difference is desirable.
Simulations reveal that the dawnward transport of the normal magnetic flux (Bz) by electrons beneath the ion kinetic scale is a critical feature of current sheets. While the normal magnetic field in the tail geometry suppresses reconnection onset, the reconnected magnetic field (i.e., also Bz) enhances reconnection after the x-line develops. These all together result in the competition of opposite dawn-dusk asymmetries. We propose that the vastly different global dawn-dusk scale of the magnetotails at Earth and Mercury will lead to opposite outcomes in this competition of asymmetry. This new finding can be important to the on-going ESA-JAXA mission, BepiColombo, that plans to perform a comprehensive study of Mercury's magnetosphere.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMSM12A..09L
- Keywords:
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- 2431 Ionosphere/magnetosphere interactions;
- IONOSPHERE;
- 2740 Magnetospheric configuration and dynamics;
- MAGNETOSPHERIC PHYSICS;
- 2756 Planetary magnetospheres;
- MAGNETOSPHERIC PHYSICS;
- 7524 Magnetic fields;
- SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY