Searcharxiv⌕ Search

arXiv subjects

Sota Arakawa

Publications and source records attributed to Sota Arakawa.

41 records · Page 3Linked to original sources
arXiv2019

Thermal conductivity and coordination number of compressed dust aggregates

Understanding the heat transfer mechanism within dust aggregates is of great importance for many subjects in planetary science. We calculated the coordination number and the thermal conductivity through the solid network of compressed dust aggregates. We found a simple relationship between the coordination number and the filling factor and revealed that the thermal conductivity through the solid network of aggregates is represented by a power-law function of the filling factor and the coordination number.

astro-ph.EP↗
arXiv2017

Thermal conductivity of porous aggregates

$\mathit{Context.}$ The thermal conductivity of highly porous dust aggregates is a key parameter for many subjects in planetary science; however, it is not yet fully understood. $\mathit{Aims.}$ In this study, we investigate the thermal conductivity of fluffy dust aggregates with filling factors of less than $10^{-1}$. $\mathit{Methods.}$ We determine the temperature structure and heat flux of the porous dust aggregates calculated by $N$-body simulations of static compression in the periodic boundary condition. $\mathit{Results.}$ We derive an empirical formula for the thermal conductivity through the solid network $k_{\rm sol}$ as a function of the filling factor of dust aggregates $ϕ$. The results reveal that $k_{\rm sol}$ is approximately proportional to $ϕ^{2}$, and the thermal conductivity through the solid network is significantly lower than previously assumed. In light of these findings, we must reconsider the thermal histories of small planetary bodies.

astro-ph.EP↗
arXiv2017

Ejection of Chondrules from Fluffy Matrices

Chondritic meteorites primarily contain millimeter-sized spherical objects, the so-called chondrules; however, the co-accretion process of chondrules and matrix grains is not yet understood. In this study, we investigate the ejection process of chondrules via collisions of fluffy aggregates composed of chondrules and matrices. We reveal that fluffy aggregates cannot grow into planetesimals without losing chondrules if we assume that the chondrite parent bodies are formed via direct aggregation of similar-sized aggregates. Therefore, an examination of other growth pathways is necessary to explain the formation of rocky planetesimals in our solar system.

astro-ph.EP↗
arXiv2016

Rocky Planetesimal Formation via Fluffy Aggregates of Nanograins

Several pieces of evidence suggest that silicate grains in primitive meteorites are not interstellar grains but condensates formed in the early solar system. Moreover, the size distribution of matrix grains in chondrites implies that these condensates might be formed as nanometer-sized grains. Therefore, we propose a novel scenario for rocky planetesimal formation in which nanometer-sized silicate grains are produced by evaporation and recondensation events in early solar nebula, and rocky planetesimals are formed via aggregation of these nanograins. We reveal that silicate nanograins can grow into rocky planetesimals via direct aggregation without catastrophic fragmentation and serious radial drift, and our results provide a suitable condition for protoplanet formation in our solar system.

astro-ph.EP↗