10:45 AM - 12:15 PM
[PPS07-P23] Co-evolution of temperature and density structure in the inner region of the disk of protoplanetary systems
Planetesimals are formed in protoplanetary disks by sticking or concentrating the dust particles and the planetesimals grow into planets through colliding with other planetesimals or catching circumambient dust particles. However, the process of formation of planetesimals is not clear.
It is necessary to understand the evolution of the disk structure for understanding how the concentration of the dust particles, which can be a cause of planet-forming, occurs. A recent theoretical calculation has shown that the temperature dependence of the magnetic turbulence intensity forms a region where dust particles concentrate and rocky planetesimals are formed in the area near the current orbits of planets of the solar system. However, this model assumes that the disk is always in radiative equilibrium and is unable to consider unsteady disk evolution, such as thermal instability due to non-equilibrium temperature evolution. The objective of this study is to verify whether pressure bumps can be formed that cause the dust concentration even when non-equilibrium temperature evolution in the inner disk is considered. We investigate the co-evolution of the temperature and density structures by simultaneously calculating the unsteady energy equation and the advection and diffusion of dust and gas. We assumed that the dust sublimate when the temperature exceeded 1400 K, and we also considered sticking and fragmentation with a critical fragmentation velocity of 10 m/s. For the temperature evolution, heating due to the central star irradiation and the disk accretion, radiative cooling, and thermal diffusion were considered. The temperature dependence of the magnetorotational instability (MRI) is assumed so that the turbulence intensity increases with MRI-active when the temperature exceeds 1000 K.
The calculations showed that the inner side of the disk became thermally unstable, but pressure bumps formed where the turbulence intensity switched, and dust concentration could occur. At the outer boundary of the region that became MRI-active due to accretion heating, the gas gained angular momentum due to turbulent viscous torque and flowed outward. The dust particles were dragged along by the gas flow trapped in the gas pressure maximum. After that, the temperature dropped, and the disk became MRI-inactive. The trapped dust particles moved inward again. The temperature then rose, and the inner region became MRI-active again. As these processes were repeated, the dust surface density gradually increased, and concentration occurred. The dust concentration where the dust density exceeds the gas density at the midplane, which can lead to the formation of planetesimals, occurred at around 0.5 au to 0.7 au, and the temperature in this area at that time was around 700 K to 800 K. The total mass of the dust concentration was several times the mass of the Earth. This result suggests that rocky planetesimals may be formed around the current Earth orbit under a hotter environment than the present one.
It is necessary to understand the evolution of the disk structure for understanding how the concentration of the dust particles, which can be a cause of planet-forming, occurs. A recent theoretical calculation has shown that the temperature dependence of the magnetic turbulence intensity forms a region where dust particles concentrate and rocky planetesimals are formed in the area near the current orbits of planets of the solar system. However, this model assumes that the disk is always in radiative equilibrium and is unable to consider unsteady disk evolution, such as thermal instability due to non-equilibrium temperature evolution. The objective of this study is to verify whether pressure bumps can be formed that cause the dust concentration even when non-equilibrium temperature evolution in the inner disk is considered. We investigate the co-evolution of the temperature and density structures by simultaneously calculating the unsteady energy equation and the advection and diffusion of dust and gas. We assumed that the dust sublimate when the temperature exceeded 1400 K, and we also considered sticking and fragmentation with a critical fragmentation velocity of 10 m/s. For the temperature evolution, heating due to the central star irradiation and the disk accretion, radiative cooling, and thermal diffusion were considered. The temperature dependence of the magnetorotational instability (MRI) is assumed so that the turbulence intensity increases with MRI-active when the temperature exceeds 1000 K.
The calculations showed that the inner side of the disk became thermally unstable, but pressure bumps formed where the turbulence intensity switched, and dust concentration could occur. At the outer boundary of the region that became MRI-active due to accretion heating, the gas gained angular momentum due to turbulent viscous torque and flowed outward. The dust particles were dragged along by the gas flow trapped in the gas pressure maximum. After that, the temperature dropped, and the disk became MRI-inactive. The trapped dust particles moved inward again. The temperature then rose, and the inner region became MRI-active again. As these processes were repeated, the dust surface density gradually increased, and concentration occurred. The dust concentration where the dust density exceeds the gas density at the midplane, which can lead to the formation of planetesimals, occurred at around 0.5 au to 0.7 au, and the temperature in this area at that time was around 700 K to 800 K. The total mass of the dust concentration was several times the mass of the Earth. This result suggests that rocky planetesimals may be formed around the current Earth orbit under a hotter environment than the present one.