[PPS03-P23] Evolution of Cometary Dust Particles to the Orbit of the Earth: Particle Size, Shape, and
Mutual Collisions
キーワード：Interplanetary dust particles, dynamical evolution, size frequency distribution, dust ejection
In this study, we numerically investigated the orbital evolution of cometary dust particles, with special
consideration of the initial size–frequency distribution (SFD) and different evolutionary tracks according to the
initial orbit and particle shape. We found that close encounters with planets (mostly Jupiter) are the dominating
factor determining the orbital evolution of dust particles. Therefore, the lifetimes of cometary dust particles
(∼250,000 yr) are shorter than the Poynting–Robertson lifetime, and only a small fraction of large cometary dust
particles can be transferred into orbits with small semimajor axis. The exceptions are dust particles from 2P/Encke
and, potentially, active asteroids that have little interaction with Jupiter. We also found that the effects of dust
shape, mass density, and SFD were not critical in the total mass supply rate to the interplanetary dust particle (IDP)
cloud complex when these quantities are confined by observations of zodiacal light brightness and SFD around the
Earth’s orbit. When we incorporate a population of fluffy aggregates discovered in the Earth’s stratosphere and the
coma of 67P/Churyumov–Gerasimenko within the initial ejection, the initial SFD measured at the comae of
comets (67P and 81P/Wild 2) can produce the observed SFD around the Earth’s orbit. Considering the above
effects, we derived the probability of mutual collisions among dust particles within the IDP cloud for the first time
in a direct manner via numerical simulation and concluded that mutual collisions can mostly be ignored.
consideration of the initial size–frequency distribution (SFD) and different evolutionary tracks according to the
initial orbit and particle shape. We found that close encounters with planets (mostly Jupiter) are the dominating
factor determining the orbital evolution of dust particles. Therefore, the lifetimes of cometary dust particles
(∼250,000 yr) are shorter than the Poynting–Robertson lifetime, and only a small fraction of large cometary dust
particles can be transferred into orbits with small semimajor axis. The exceptions are dust particles from 2P/Encke
and, potentially, active asteroids that have little interaction with Jupiter. We also found that the effects of dust
shape, mass density, and SFD were not critical in the total mass supply rate to the interplanetary dust particle (IDP)
cloud complex when these quantities are confined by observations of zodiacal light brightness and SFD around the
Earth’s orbit. When we incorporate a population of fluffy aggregates discovered in the Earth’s stratosphere and the
coma of 67P/Churyumov–Gerasimenko within the initial ejection, the initial SFD measured at the comae of
comets (67P and 81P/Wild 2) can produce the observed SFD around the Earth’s orbit. Considering the above
effects, we derived the probability of mutual collisions among dust particles within the IDP cloud for the first time
in a direct manner via numerical simulation and concluded that mutual collisions can mostly be ignored.