Effect of the tidal-seismic resonance
Abstract
For a moon spiraling inward to its planet, the tidal force frequency of a moon is increasing. When the distance of the moon to the planet is close enough, the tidal force frequency can intrude into the frequency range of planet normal modes. Usually the football mode, also known as 0S2, has the lowest frequency. This mode is most likely to be excited and coupled first. When the tidal force has the same frequency with the normal modes, the resonance can happen. The existence of the topography or internal heterogeneities of the planet can have mode coupling. So the energy of gravity force with higher spatial frequencies can be transferred to the low spatial 0S2 mode. The resonant mode 0S2 can exert a negative torque to the rotating moon so its orbit decays. With our 3D numerical boundary element method which takes into account planet surface topography (i.e., Mars as example), we found that the closer the moon is to the planet, the greater falling rate of the moon would be. We applied our method to a planet with equal size of Mars and elastic constants in possible range. The vibration amplitude on the planet surface can reach to the scale of meters when as the moon drop down to about 1.04 radius of the planet to achieve resonance with the 0S2 mode. Our modeling showed that the influence of tidal force caused resonance could not be neglected in the process of moon falling. On the other hand, the resonance may also be able to speed up the accretion of the early forming planet by absorbing the dust of small asteroid nearby by the tidal-seismic resonance.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFM.P51A2571T
- Keywords:
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- 6024 Interiors;
- PLANETARY SCIENCES: COMETS AND SMALL BODIES;
- 6040 Origin and evolution;
- PLANETARY SCIENCES: COMETS AND SMALL BODIES;
- 5430 Interiors;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS;
- 5455 Origin and evolution;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS