3:45 PM - 4:00 PM
[MGI30-08] Time evolution of spiral structures in the Moon-forming disk
Keywords:Moon-forming disk, N-body simulation
The giant impact hypothesis is a widely supported scenario for the origin of the Moon(Hartmann & Davis 1975; Cameron & Ward 1976). According to this hypothesis, the Moon formed from the accretion of circumterrestrial disk generated by the collision of a Mars-sized celestial body with the proto-Earth. In this model, the circumterrestrial disk, which forms within the Roche limit and cools and solidifies from hot gas, may consist of very small rocky particles. These rocky particles can be modeled as particles in N-body simulations and understanding the numerical resolution dependence on the lunar accretion process is crucial.
Previous simulations of lunar accretion process have modeled the circumterrestrial disk using around 10,000 particles, and it is thought that the Moon was formed outside the Roche limit in approximately one month(e.g., Kokubo et al., 2000). Sasaki & Hosono (2018) modeled the circumterrestrial disk with particles ranging from 10,000 to 10,000,000 and investigated the effect of the numerical resolution on the luner accretion process. They revealed that in high-resolution simulations, spiral arms connect to form complex structures and that the Moon formation timescales longer. In addition, Yamaoka (JpGU 2023, MGI30-04) found that a leading spiral structure appeared in high-resolution simulations within 1.6 times Earth radius, attributing this to viscous overstability.
In this study, we investigated the time evolution of the leading spiral structure in the inner region of the disk and performed a stability analysis. We parformed N-body simulations of the lunar accretion from the circumterrestrial disk modeled with upto 10,000,000 particles. First, we tracked the time evolution of the inner disk structure through surface density distribution. When the number of particles is small, leading spirals do not form, but increasing the resolution makes them visible. The leading spiral is a transient structure that repeatedly forms and transitions into a trailing arm. Next, we calculated local Toomre's Q values and analyzed the stability of the region where the leading spiral is formed. In the high-resolution simulation where the leading spiral appears, we found that the gravitational instability bocomes stronger along the leading spiral. In the high-resolution simulation, the formation of the leading spiral creates high-density regions, which enhance the gravitational instability and lead to the transformation into trailing arms.
Thease spiral structures are likely influencing angular momentum transport, thereby extending the Moon formation timescale.
Previous simulations of lunar accretion process have modeled the circumterrestrial disk using around 10,000 particles, and it is thought that the Moon was formed outside the Roche limit in approximately one month(e.g., Kokubo et al., 2000). Sasaki & Hosono (2018) modeled the circumterrestrial disk with particles ranging from 10,000 to 10,000,000 and investigated the effect of the numerical resolution on the luner accretion process. They revealed that in high-resolution simulations, spiral arms connect to form complex structures and that the Moon formation timescales longer. In addition, Yamaoka (JpGU 2023, MGI30-04) found that a leading spiral structure appeared in high-resolution simulations within 1.6 times Earth radius, attributing this to viscous overstability.
In this study, we investigated the time evolution of the leading spiral structure in the inner region of the disk and performed a stability analysis. We parformed N-body simulations of the lunar accretion from the circumterrestrial disk modeled with upto 10,000,000 particles. First, we tracked the time evolution of the inner disk structure through surface density distribution. When the number of particles is small, leading spirals do not form, but increasing the resolution makes them visible. The leading spiral is a transient structure that repeatedly forms and transitions into a trailing arm. Next, we calculated local Toomre's Q values and analyzed the stability of the region where the leading spiral is formed. In the high-resolution simulation where the leading spiral appears, we found that the gravitational instability bocomes stronger along the leading spiral. In the high-resolution simulation, the formation of the leading spiral creates high-density regions, which enhance the gravitational instability and lead to the transformation into trailing arms.
Thease spiral structures are likely influencing angular momentum transport, thereby extending the Moon formation timescale.